Programs & Examples On #Xact

How can I convert this one line of ActionScript to C#?

There is collection of Func<...> classes - Func that is probably what you are looking for:

 void MyMethod(Func<int> param1 = null) 

This defines method that have parameter param1 with default value null (similar to AS), and a function that returns int. Unlike AS in C# you need to specify type of the function's arguments.

So if you AS usage was

MyMethod(function(intArg, stringArg) { return true; }) 

Than in C# it would require param1 to be of type Func<int, siring, bool> and usage like

MyMethod( (intArg, stringArg) => { return true;} ); 

Difference between opening a file in binary vs text

The link you gave does actually describe the differences, but it's buried at the bottom of the page:

Text files are files containing sequences of lines of text. Depending on the environment where the application runs, some special character conversion may occur in input/output operations in text mode to adapt them to a system-specific text file format. Although on some environments no conversions occur and both text files and binary files are treated the same way, using the appropriate mode improves portability.

The conversion could be to normalize \r\n to \n (or vice-versa), or maybe ignoring characters beyond 0x7F (a-la 'text mode' in FTP). Personally I'd open everything in binary-mode and use a good text-encoding library for dealing with text.

What's the net::ERR_HTTP2_PROTOCOL_ERROR about?

In my case, it was WordPress that now requires PHP 7.4 and I was running 7.2.
As soon as I updated, the errors disappeared.

OpenCV TypeError: Expected cv::UMat for argument 'src' - What is this?

gray = cv2.cvtColor(cv2.UMat(imgUMat), cv2.COLOR_RGB2GRAY)

UMat is a part of the Transparent API (TAPI) than help to write one code for the CPU and OpenCL implementations.

WARNING in budgets, maximum exceeded for initial

What is Angular CLI Budgets? Budgets is one of the less known features of the Angular CLI. It’s a rather small but a very neat feature!

As applications grow in functionality, they also grow in size. Budgets is a feature in the Angular CLI which allows you to set budget thresholds in your configuration to ensure parts of your application stay within boundaries which you setOfficial Documentation

Or in other words, we can describe our Angular application as a set of compiled JavaScript files called bundles which are produced by the build process. Angular budgets allows us to configure expected sizes of these bundles. More so, we can configure thresholds for conditions when we want to receive a warning or even fail build with an error if the bundle size gets too out of control!

How To Define A Budget? Angular budgets are defined in the angular.json file. Budgets are defined per project which makes sense because every app in a workspace has different needs.

Thinking pragmatically, it only makes sense to define budgets for the production builds. Prod build creates bundles with “true size” after applying all optimizations like tree-shaking and code minimization.

Oops, a build error! The maximum bundle size was exceeded. This is a great signal that tells us that something went wrong…

  1. We might have experimented in our feature and didn’t clean up properly
  2. Our tooling can go wrong and perform a bad auto-import, or we pick bad item from the suggested list of imports
  3. We might import stuff from lazy modules in inappropriate locations
  4. Our new feature is just really big and doesn’t fit into existing budgets

First Approach: Are your files gzipped?

Generally speaking, gzipped file has only about 20% the size of the original file, which can drastically decrease the initial load time of your app. To check if you have gzipped your files, just open the network tab of developer console. In the “Response Headers”, if you should see “Content-Encoding: gzip”, you are good to go.

How to gzip? If you host your Angular app in most of the cloud platforms or CDN, you should not worry about this issue as they probably have handled this for you. However, if you have your own server (such as NodeJS + expressJS) serving your Angular app, definitely check if the files are gzipped. The following is an example to gzip your static assets in a NodeJS + expressJS app. You can hardly imagine this dead simple middleware “compression” would reduce your bundle size from 2.21MB to 495.13KB.

const compression = require('compression')
const express = require('express')
const app = express()

Second Approach:: Analyze your Angular bundle

If your bundle size does get too big you may want to analyze your bundle because you may have used an inappropriate large-sized third party package or you forgot to remove some package if you are not using it anymore. Webpack has an amazing feature to give us a visual idea of the composition of a webpack bundle.

enter image description here

It’s super easy to get this graph.

  1. npm install -g webpack-bundle-analyzer
  2. In your Angular app, run ng build --stats-json (don’t use flag --prod). By enabling --stats-json you will get an additional file stats.json
  3. Finally, run webpack-bundle-analyzer ./dist/stats.json and your browser will pop up the page at localhost:8888. Have fun with it.

ref 1: How Did Angular CLI Budgets Save My Day And How They Can Save Yours

ref 2: Optimize Angular bundle size in 4 steps

Flutter - The method was called on null

You should declare your method first in void initState(), so when the first time pages has been loaded, it will init your method first, hope it can help

What is the Record type in typescript?

A Record lets you create a new type from a Union. The values in the Union are used as attributes of the new type.

For example, say I have a Union like this:

type CatNames = "miffy" | "boris" | "mordred";

Now I want to create an object that contains information about all the cats, I can create a new type using the values in the CatName Union as keys.

type CatList = Record<CatNames, {age: number}>

If I want to satisfy this CatList, I must create an object like this:

const cats:CatList = {
  miffy: { age:99 },
  boris: { age:16 },
  mordred: { age:600 }

You get very strong type safety:

  • If I forget a cat, I get an error.
  • If I add a cat that's not allowed, I get an error.
  • If I later change CatNames, I get an error. This is especially useful because CatNames is likely imported from another file, and likely used in many places.

Real-world React example.

I used this recently to create a Status component. The component would receive a status prop, and then render an icon. I've simplified the code quite a lot here for illustrative purposes

I had a union like this:

type Statuses = "failed" | "complete";

I used this to create an object like this:

const icons: Record<
  { iconType: IconTypes; iconColor: IconColors }
> = {
  failed: {
    iconType: "warning",
    iconColor: "red"
  complete: {
    iconType: "check",
    iconColor: "green"

I could then render by destructuring an element from the object into props, like so:

const Status = ({status}) => <Icon {...icons[status]} />

If the Statuses union is later extended or changed, I know my Status component will fail to compile and I'll get an error that I can fix immediately. This allows me to add additional error states to the app.

Note that the actual app had dozens of error states that were referenced in multiple places, so this type safety was extremely useful.

Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0

Try this one

cd android && ./gradlew clean && ./gradlew :app:bundleRelease

How do I install the Nuget provider for PowerShell on a unconnected machine so I can install a nuget package from the PS command line?

The provider is bundled with PowerShell>=6.0.

If all you need is a way to install a package from a file, just grab the .msi installer for the latest version from the github releases page, copy it over to the machine, install it and use it.

What exactly is the 'react-scripts start' command?

As Sagiv b.g. pointed out, the npm start command is a shortcut for npm run start. I just wanted to add a real-life example to clarify it a bit more.

The setup below comes from the create-react-app github repo. The package.json defines a bunch of scripts which define the actual flow.

"scripts": {
  "start": "npm-run-all -p watch-css start-js",
  "build": "npm run build-css && react-scripts build",
  "watch-css": "npm run build-css && node-sass-chokidar --include-path ./src --include-path ./node_modules src/ -o src/ --watch --recursive",
  "build-css": "node-sass-chokidar --include-path ./src --include-path ./node_modules src/ -o src/",
  "start-js": "react-scripts start"

For clarity, I added a diagram. enter image description here

The blue boxes are references to scripts, all of which you could executed directly with an npm run <script-name> command. But as you can see, actually there are only 2 practical flows:

  • npm run start
  • npm run build

The grey boxes are commands which can be executed from the command line.

So, for instance, if you run npm start (or npm run start) that actually translate to the npm-run-all -p watch-css start-js command, which is executed from the commandline.

In my case, I have this special npm-run-all command, which is a popular plugin that searches for scripts that start with "build:", and executes all of those. I actually don't have any that match that pattern. But it can also be used to run multiple commands in parallel, which it does here, using the -p <command1> <command2> switch. So, here it executes 2 scripts, i.e. watch-css and start-js. (Those last mentioned scripts are watchers which monitor file changes, and will only finish when killed.)

  • The watch-css makes sure that the *.scss files are translated to *.cssfiles, and looks for future updates.

  • The start-js points to the react-scripts start which hosts the website in a development mode.

In conclusion, the npm start command is configurable. If you want to know what it does, then you have to check the package.json file. (and you may want to make a little diagram when things get complicated).

Set default option in mat-select


<mat-select [(ngModel)]="modeSelect" placeholder="Mode">
  <mat-option *ngFor="let obj of Array"  [value]="obj.value">{{obj.value}}</mat-option>

Now set your default value to


, where you are getting the values in Array variable.

How to do a timer in Angular 5

This may be overkill for what you're looking for, but there is an npm package called marky that you can use to do this. It gives you a couple of extra features beyond just starting and stopping a timer. You just need to install it via npm and then import the dependency anywhere you'd like to use it. Here is a link to the npm package:

An example of use after installing via npm would be as follows:

import * as _M from 'marky';

 selector: 'app-test',
 templateUrl: './test.component.html',
 styleUrls: ['./test.component.scss']

export class TestComponent implements OnInit {
 Marky = _M;

constructor() {}

ngOnInit() {}

startTimer(key: string) {

stopTimer(key: string) {

key is simply a string which you are establishing to identify that particular measurement of time. You can have multiple measures which you can go back and reference your timer stats using the keys you create.

Access IP Camera in Python OpenCV

First find out your IP camera's streaming url, like whether it's RTSP/HTTP etc.

Code changes will be as follows:

cap = cv2.VideoCapture("ipcam_streaming_url")

For example:

cap = cv2.VideoCapture("")

Uncaught (in promise): Error: StaticInjectorError(AppModule)[options]

HttpClientModule needs to be in the imports array, and remove it from providers. That section is for you to tell Angular which services the module has (written by you and not imported from a library).

Default interface methods are only supported starting with Android N

You should use Java 8 to solve this, based on the Android documentation you can do this by

clicking File > Project Structure

and change Source Compatibility and Target Compatibility.

enter image description here

and you can also configure it directly in the app-level build.gradle file:

android {
  // Configure only for each module that uses Java 8
  // language features (either in its source code or
  // through dependencies).
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8

React : difference between <Route exact path="/" /> and <Route path="/" />

Take a look here:

exact: bool

When true, will only match if the path matches the location.pathname exactly.

**path**    **location.pathname**   **exact**   **matches?**

/one        /one/two                true        no
/one        /one/two                false       yes

ASP.NET Core - Swashbuckle not creating swagger.json file

// Enable middleware to serve generated Swagger as a JSON endpoint.

app.UseSwagger(c =>
    c.SerializeAsV2 = true;

// Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.),
// specifying the Swagger JSON endpoint.
app.UseSwaggerUI(c =>
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "API Name");

What is pipe() function in Angular

Two very different types of Pipes Angular - Pipes and RxJS - Pipes


A pipe takes in data as input and transforms it to a desired output. In this page, you'll use pipes to transform a component's birthday property into a human-friendly date.

import { Component } from '@angular/core';

  selector: 'app-hero-birthday',
  template: `<p>The hero's birthday is {{ birthday | date }}</p>`
export class HeroBirthdayComponent {
  birthday = new Date(1988, 3, 15); // April 15, 1988

RxJS - Pipe

Observable operators are composed using a pipe method known as Pipeable Operators. Here is an example.

import {Observable, range} from 'rxjs';
import {map, filter} from 'rxjs/operators';

const source$: Observable<number> = range(0, 10);

    map(x => x * 2),
    filter(x => x % 3 === 0)
).subscribe(x => console.log(x));

The output for this in the console would be the following:





For any variable holding an observable, we can use the .pipe() method to pass in one or multiple operator functions that can work on and transform each item in the observable collection.

So this example takes each number in the range of 0 to 10, and multiplies it by 2. Then, the filter function to filter the result down to only the odd numbers.

what does numpy ndarray shape do?

Unlike it's most popular commercial competitor, numpy pretty much from the outset is about "arbitrary-dimensional" arrays, that's why the core class is called ndarray. You can check the dimensionality of a numpy array using the .ndim property. The .shape property is a tuple of length .ndim containing the length of each dimensions. Currently, numpy can handle up to 32 dimensions:

a = np.ones(32*(1,))
# array([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ 1.]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]])
# (1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1)
# 32

If a numpy array happens to be 2d like your second example, then it's appropriate to think about it in terms of rows and columns. But a 1d array in numpy is truly 1d, no rows or columns.

If you want something like a row or column vector you can achieve this by creating a 2d array with one of its dimensions equal to 1.

a = np.array([[1,2,3]]) # a 'row vector'
b = np.array([[1],[2],[3]]) # a 'column vector'
# or if you don't want to type so many brackets:
b = np.array([[1,2,3]]).T

NullInjectorError: No provider for AngularFirestore

Open: ./src/app/app.module.ts
And import Firebase Modules at the top:

import { environment } from '../environments/environment';
import { AngularFireModule } from 'angularfire2';
import { AngularFirestoreModule } from 'angularfire2/firestore';

Remember to update 'imports' in NgModule:

  declarations: [
    OtherComponent // Add other components here
  imports: [
    AngularFireModule.initializeApp(environment.firebase, 'your-APP-name-here'),

Give it a try, it shall now work.
For detailed information follow the angularfire2 documentation:
Good luck!

How to update/upgrade a package using pip?

To upgrade pip for Python3.4+, you must use pip3 as follows:

sudo pip3 install pip --upgrade

This will upgrade pip located at: /usr/local/lib/python3.X/dist-packages

Otherwise, to upgrade pip for Python2.7, you would use pip as follows:

sudo pip install pip --upgrade

This will upgrade pip located at: /usr/local/lib/python2.7/dist-packages

How to open local file on Jupyter?

On osX, Your path should be:

path = "/Users/name/Downloads/filename"

with name the current user logged in

react-router (v4) how to go back?

I think the issue is with binding:

   this.goBack = this.goBack.bind(this); // i think you are missing this



<button onClick={this.goBack}>Go Back</button>

As I have assumed before you posted the code:

constructor(props) {
    this.handleNext = this.handleNext.bind(this);
    this.handleBack = this.handleBack.bind(this); // you are missing this line

How to VueJS router-link active style

Just add to @Bert's solution to make it more clear:

    const routes = [
  { path: '/foo', component: Foo },
  { path: '/bar', component: Bar }

const router = new VueRouter({
  linkExactActiveClass: "active" // active class for *exact* links.

As one can see, this line should be removed:

linkActiveClass: "active", // active class for non-exact links.

this way, ONLY the current link is hi-lighted. This should apply to most of the cases.


React Router Pass Param to Component

If you want to pass props to a component inside a route, the simplest way is by utilizing the render, like this:

<Route exact path="/details/:id" render={(props) => <DetailsPage globalStore={globalStore} {...props} /> } />

You can access the props inside the DetailPage using:


The {...props} is needed to pass the original Route's props, otherwise you will only get this.props.globalStore inside the DetailPage.

How to import popper.js?

IN bootstrap 4 you need to add popper js for tooltip, I also don`t understand why bootstrap 4 includes external popper.js, It means bootstrap makes more complicated instead of easy when upgrading to the latest versions.

You can import popper js before bootstrap on angular or a simple html, Angular import would be like this

npm install popper.js --save

then go to .angular-cli.json and change the order like below.

 "scripts": [

you can also use CDN direct call popper js into your any project.

NotificationCompat.Builder deprecated in Android O

Simple Sample

    public void showNotification (String from, String notification, Intent intent) {
        PendingIntent pendingIntent = PendingIntent.getActivity(

        String NOTIFICATION_CHANNEL_ID = "my_channel_id_01";
        NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "My Notifications", NotificationManager.IMPORTANCE_DEFAULT);

            // Configure the notification channel.
            notificationChannel.setDescription("Channel description");
            notificationChannel.setVibrationPattern(new long[]{0, 1000, 500, 1000});

        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID);
        Notification mNotification = builder

//                .setTicker("Hearty365")
//                .setContentInfo("Info")
                //     .setPriority(Notification.PRIORITY_MAX)


//                .setDefaults(Notification.DEFAULT_ALL)
//                .setWhen(System.currentTimeMillis())
                .setLargeIcon(BitmapFactory.decodeResource(context.getResources(), R.mipmap.ic_launcher))

        notificationManager.notify(/*notification id*/Notification_ID, mNotification);


Constraint Layout Vertical Align Center

May be i did not fully understand the problem, but, centering all view inside a ConstraintLayout seems very simple. This is what I used:

< xmlns:android=""

enter image description here

Last two lines did the trick!

ESLint not working in VS Code?

Since you are able to successfully lint via command line, the issue is most likely in the configuration of the ESLint plugin.

Assuming the extension is properly installed, check out all ESLint related config properties in both project (workspace) and user (global) defined settings.json.

There are a few things that could be misconfigured in your particular case; for me it was JavaScript disabled after working with TypeScript in another project and my global settings.json ended up looking following:

"eslint.validate": [
  { "language": "typescript", "autoFix": true }

From here it was a simple fix:

"eslint.validate": [
  { "language": "javascript", "autoFix": true },
  { "language": "typescript", "autoFix": true }

This is so common that someone wrote a straight forward blog post about ESLint not working in VS Code. I'd just add, check your global user settings.json before overriding the local workspace config.

Vue js error: Component template should contain exactly one root element

Note This answer only applies to version 2.x of Vue. Version 3 has lifted this restriction.

You have two root elements in your template.

<div class="form-group">
<div class="col-md-6">

And you need one.

    <div class="form-group">

    <div class="col-md-6">

Essentially in Vue you must have only one root element in your templates.

Returning JSON object as response in Spring Boot

More correct create DTO for API queries, for example entityDTO:

  1. Default response OK with list of entities:
public List<EntityDto> getAll() {
    return entityService.getAllEntities();

But if you need return different Map parameters you can use next two examples
2. For return one parameter like map:

public ResponseEntity<Object> getOneParameterMap() {
    return ResponseEntity.status(HttpStatus.CREATED).body(
            Collections.singletonMap("key", "value"));
  1. And if you need return map of some parameters(since Java 9):
@GetMapping(produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<Object> getSomeParameters() {
    return ResponseEntity.status(HttpStatus.OK).body(Map.of(
            "key-1", "value-1",
            "key-2", "value-2",
            "key-3", "value-3"));

React-router v4 this.props.history.push(...) not working

Seems like an old question but still relevant.

I think it is a blocked update issue.

The main problem is the new URL (route) is supposed to be rendered by the same component(Costumers) as you are currently in (current URL).

So solution is rather simple, make the window url as a prop, so react has a chance to detect the prop change (therefore the url change), and act accordingly.

A nice usecase described in the official react blog called Recommendation: Fully uncontrolled component with a key.

So the solution is to change from render() { return( <ul>

to render() { return( <ul key={this.props.location.pathname}>

So whenever the location changed by react-router, the component got scrapped (by react) and a new one gets initiated with the right values (by react).

Oh, and pass the location as prop to the component(Costumers) where the redirect will happen if it is not passed already.

Hope it helps someone.

VS 2017 Metadata file '.dll could not be found

In my case, I had to open the .csproj file and add the reference by hand, like this (Microsoft.Extensions.Identity.Stores.dll was missing):

<Reference Include="Microsoft.Extensions.Identity.Stores">
  <HintPath>..\..\..\..\Program Files\dotnet\sdk\NuGetFallbackFolder\microsoft.extensions.identity.stores\2.0.1\lib\netstandard2.0\Microsoft.Extensions.Identity.Stores.dll</HintPath>

Val and Var in Kotlin

var is a variable like any other language. eg.

var price: Double

On the other side, val provides you feature of referencing. eg.

// You refer this to get constant value 7. In this case, val acts as access
// specifier final in Java


val Int.absolute: Int
    get() {
        return Math.abs(this)
// You refer to the newly create 'method' which provides absolute value 
// of your integer

println(-5.absolute) // O.P: 5

The origin server did not find a current representation for the target resource or is not willing to disclose that one exists

I had this problem in InteliJ. I went to: Edit -> Configuration -> Deployment -> EditArtifact:

enter image description here

Then there where yellow problems, I just clicked on fix two times and it works. I hope this will help someone.

How do I set the background color of my main screen in Flutter?

Here's one way that I found to do it. I don't know if there are better ways, or what the trade-offs are.

Container "tries to be as big as possible", according to Also, Container can take a decoration, which can be a BoxDecoration, which can have a color (which, is the background color).

Here's a sample that does indeed fill the screen with red, and puts "Hello, World!" into the center:

import 'package:flutter/material.dart';

void main() {
  runApp(new MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  Widget build(BuildContext context) {
    return new Container(
      decoration: new BoxDecoration(color:,
      child: new Center(
        child: new Text("Hello, World!"),

Note, the Container is returned by the MyApp build(). The Container has a decoration and a child, which is the centered text.

See it in action here:

enter image description here

How to fix the error "Windows SDK version 8.1" was not found?

  • Install the required version of Windows SDK or change the SDK version in the project property pages


  • by right-clicking the solution and selecting "Retarget solution"

If you do visual studio guide, you will resolve the problem.

Spark difference between reduceByKey vs groupByKey vs aggregateByKey vs combineByKey

While both reducebykey and groupbykey will produce the same answer, the reduceByKey example works much better on a large dataset. That's because Spark knows it can combine output with a common key on each partition before shuffling the data.

On the other hand, when calling groupByKey - all the key-value pairs are shuffled around. This is a lot of unnessary data to being transferred over the network.

for more detailed check this below link

'Found the synthetic property @panelState. Please include either "BrowserAnimationsModule" or "NoopAnimationsModule" in your application.'

Simply add .. import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

imports: [ .. BrowserAnimationsModule


in app.module.ts file.

make sure you have installed .. npm install @angular/animations@latest --save

How to implement authenticated routes in React Router 4?

I implemented using-

<Route path='/dashboard' render={() => (
    this.state.user.isLoggedIn ? 
    (<Dashboard authenticate={this.authenticate} user={this.state.user} />) : 
    (<Redirect to="/login" />)
)} />

authenticate props will be passed to components e.g. signup using which user state can be changed. Complete AppRoutes-

import React from 'react';
import { Switch, Route } from 'react-router-dom';
import { Redirect } from 'react-router';

import Home from '../pages/home';
import Login from '../pages/login';
import Signup from '../pages/signup';
import Dashboard from '../pages/dashboard';

import { config } from '../utils/Config';

export default class AppRoutes extends React.Component {

    constructor(props) {

        // initially assuming that user is logged out
        let user = {
            isLoggedIn: false

        // if user is logged in, his details can be found from local storage
        try {
            let userJsonString = localStorage.getItem(config.localStorageKey);
            if (userJsonString) {
                user = JSON.parse(userJsonString);
        } catch (exception) {

        // updating the state
        this.state = {
            user: user

        this.authenticate = this.authenticate.bind(this);

    // this function is called on login/logout
    authenticate(user) {
            user: user

        // updating user's details
        localStorage.setItem(config.localStorageKey, JSON.stringify(user));

    render() {
        return (
                <Route exact path='/' component={Home} />
                <Route exact path='/login' render={() => <Login authenticate={this.authenticate} />} />
                <Route exact path='/signup' render={() => <Signup authenticate={this.authenticate} />} />
                <Route path='/dashboard' render={() => (
                    this.state.user.isLoggedIn ? 
                            (<Dashboard authenticate={this.authenticate} user={this.state.user} />) : 
                            (<Redirect to="/login" />)
                )} />

Check the complete project here:

Purpose of "%matplotlib inline"

If you don't know what backend is , you can read this:

Some people use matplotlib interactively from the python shell and have plotting windows pop up when they type commands. Some people run Jupyter notebooks and draw inline plots for quick data analysis. Others embed matplotlib into graphical user interfaces like wxpython or pygtk to build rich applications. Some people use matplotlib in batch scripts to generate postscript images from numerical simulations, and still others run web application servers to dynamically serve up graphs. To support all of these use cases, matplotlib can target different outputs, and each of these capabilities is called a backend; the "frontend" is the user facing code, i.e., the plotting code, whereas the "backend" does all the hard work behind-the-scenes to make the figure.

So when you type %matplotlib inline , it activates the inline backend. As discussed in the previous posts :

With this backend, the output of plotting commands is displayed inline within frontends like the Jupyter notebook, directly below the code cell that produced it. The resulting plots will then also be stored in the notebook document.

React-Router External link

With Link component of react-router you can do that. In the "to" prop you can specify 3 types of data:

  • a string: A string representation of the Link location, created by concatenating the location’s pathname, search, and hash properties.
  • an object: An object that can have any of the following properties:
    • pathname: A string representing the path to link to.
    • search: A string representation of query parameters.
    • hash: A hash to put in the URL, e.g. #a-hash.
    • state: State to persist to the location.
  • a function: A function to which current location is passed as an argument and which should return location representation as a string or as an object

For your example (external link):

You can do the following:

<Link to={{ pathname: "" }} target="_blank" />

You can also pass props you’d like to be on the such as a title, id, className, etc.

Unit Tests not discovered in Visual Studio 2017

In my case the Test Explorer couldn't find my tests after I moved the project to a new solution.

The answer was simply that I had a reference to the old MS Test Adapter in my project.

I had a duplicate of the line below for version 1.1.11 of the MS Test Adapter in my cs.proj file:

<Import Project="..\packages\MSTest.TestAdapter.1.1.18\build\net45\MSTest.TestAdapter.props" Condition="Exists('..\packages\MSTest.TestAdapter.1.1.18\build\net45\MSTest.TestAdapter.props')" />

To fix the problem,

  1. Right click on project and select 'Unload Project'.
  2. Right click project and select 'Edit'
  3. Remove line that imports old version of adapter.
  4. Right click on project and select 'Reload Project'.
  5. Rebuild Solution/Project

All libraries must use the exact same version specification

After spending about 5 hours, this solution worked for me..

First add this line to your manifest tag if you do not have yet:



<manifest xmlns:android=""

Then Add this meta tag inside your application to overwrite you build tools version, in this case for example I choosed the version 25.3.1

        android:value="25.3.1" />

In Typescript, what is the ! (exclamation mark / bang) operator when dereferencing a member?

Louis' answer is great, but I thought I would try to sum it up succinctly:

The bang operator tells the compiler to temporarily relax the "not null" constraint that it might otherwise demand. It says to the compiler: "As the developer, I know better than you that this variable cannot be null right now".

How to install PHP intl extension in Ubuntu 14.04

sudo apt-get install php-intl

then restart your server

TypeScript hashmap/dictionary interface

The most simple and the correct way is to use Record type Record<string, string>

const myVar : Record<string, string> = {
   key1: 'val1',
   key2: 'val2',

How does spring.jpa.hibernate.ddl-auto property exactly work in Spring?

For the record, the spring.jpa.hibernate.ddl-auto property is Spring Data JPA specific and is their way to specify a value that will eventually be passed to Hibernate under the property it knows,

The values create, create-drop, validate, and update basically influence how the schema tool management will manipulate the database schema at startup.

For example, the update operation will query the JDBC driver's API to get the database metadata and then Hibernate compares the object model it creates based on reading your annotated classes or HBM XML mappings and will attempt to adjust the schema on-the-fly.

The update operation for example will attempt to add new columns, constraints, etc but will never remove a column or constraint that may have existed previously but no longer does as part of the object model from a prior run.

Typically in test case scenarios, you'll likely use create-drop so that you create your schema, your test case adds some mock data, you run your tests, and then during the test case cleanup, the schema objects are dropped, leaving an empty database.

In development, it's often common to see developers use update to automatically modify the schema to add new additions upon restart. But again understand, this does not remove a column or constraint that may exist from previous executions that is no longer necessary.

In production, it's often highly recommended you use none or simply don't specify this property. That is because it's common practice for DBAs to review migration scripts for database changes, particularly if your database is shared across multiple services and applications.

Nested routes with react router v4 / v5

A complete answer for React Router v5.

const Router = () => {
  return (
      <Route path={"/"} component={LandingPage} exact />
      <Route path={"/games"} component={Games} />
      <Route path={"/game-details/:id"} component={GameDetails} />
        render={({ match: { path } }) => (
                path={path + "/"}
              <Route path={`${path}/inbox`} component={Inbox} />
              <Redirect exact from={path + "/*"} to={path} />
      <Route path="/not-found" component={NotFound} />
      <Redirect exact from={"*"} to={"/not-found"} />

export default Router;
const Dashboard = ({ children }) => {
  return (
      <DashboardSidebarNavigation />

export default Dashboard;

Github repo is here.

Angular 1.6.0: "Possibly unhandled rejection" error

The code you show will handle a rejection that occurs before the call to .then. In such situation, the 2nd callback you pass to .then will be called, and the rejection will be handled.

However, when the promise on which you call .then is successful, it calls the 1st callback. If this callback throws an exception or returns a rejected promise, this resulting rejection will not be handled, because the 2nd callback does not handle rejections in cause by the 1st. This is just how promise implementations compliant with the Promises/A+ specification work, and Angular promises are compliant.

You can illustrate this with the following code:

function handle(p) {
        () => {
            // This is never caught.
            throw new Error("bar");
        (err) => {
            console.log("rejected with", err);

// We do catch this rejection.
handle(Promise.reject(new Error("foo")));

If you run it in Node, which also conforms to Promises/A+, you get:

rejected with Error: foo
    at Object.<anonymous> (/tmp/t10/test.js:12:23)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:394:7)
    at startup (bootstrap_node.js:149:9)
    at bootstrap_node.js:509:3
(node:17426) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): Error: bar

Installing TensorFlow on Windows (Python 3.6.x)

Tensor flow has only support for python 2.7 3.4 3.5 Other python versions are not supported So you please install the supported python version and try it again. The official link is It provides how to install it with anaconda . This will help you

How to turn on/off MySQL strict mode in localhost (xampp)?

->STRICT_TRANS_TABLES is responsible for setting MySQL strict mode.

->To check whether strict mode is enabled or not run the below sql:


If one of the value is STRICT_TRANS_TABLES, then strict mode is enabled, else not. In my case it gave

|Variable_name |Value                                     |

Hence strict mode is enabled in my case as one of the value is STRICT_TRANS_TABLES.

->To disable strict mode run the below sql:

set global sql_mode='';

[or any mode except STRICT_TRANS_TABLES. Ex: set global sql_mode='NO_ENGINE_SUBSTITUTION';]

->To again enable strict mode run the below sql:

set global sql_mode='STRICT_TRANS_TABLES';

Disable nginx cache for JavaScript files

I know this question is a bit old but i would suggest to use some cachebraking hash in the url of the javascript. This works perfectly in production as well as during development because you can have both infinite cache times and intant updates when changes occur.

Lets assume you have a javascript file /js/script.min.js, but in the referencing html/php file you do not use the actual path but:

<script src="/js/script.<?php echo md5(filemtime('/js/script.min.js')); ?>.min.js"></script>

So everytime the file is changed, the browser gets a different url, which in turn means it cannot be cached, be it locally or on any proxy inbetween.

To make this work you need nginx to rewrite any request to /js/script.[0-9a-f]{32}.min.js to the original filename. In my case i use the following directive (for css also):

location ~* \.(css|js)$ {
                expires max;
                add_header Pragma public;
                etag off;
                add_header Cache-Control "public";
                add_header Last-Modified "";
                rewrite  "^/(.*)\/(style|script)\.min\.([\d\w]{32})\.(js|css)$" /$1/$2.min.$4 break;

I would guess that the filemtime call does not even require disk access on the server as it should be in linux's file cache. If you have doubts or static html files you can also use a fixed random value (or incremental or content hash) that is updated when your javascript / css preprocessor has finished or let one of your git hooks change it.

In theory you could also use a cachebreaker as a dummy parameter (like /js/script.min.js?cachebreak=0123456789abcfef), but then the file is not cached at least by some proxies because of the "?".

Support for ES6 in Internet Explorer 11

The statement from Microsoft regarding the end of Internet Explorer 11 support mentions that it will continue to receive security updates, compatibility fixes, and technical support until its end of life. The wording of this statement leads me to believe that Microsoft has no plans to continue adding features to Internet Explorer 11, and instead will be focusing on Edge.

If you require ES6 features in Internet Explorer 11, check out a transpiler such as Babel.

How to manage Angular2 "expression has changed after it was checked" exception when a component property depends on current datetime

I think the best and cleanest solution you can imagine is this:

@Component( {
  selector: 'app-my-component',
  template: `<p>{{ myData?.anyfield }}</p>`,
  styles: [ '' ]
} )
export class MyComponent implements OnInit {
  private myData;

  constructor( private myService: MyService ) { }

  ngOnInit( ) {
      async .. await 
      clears the ExpressionChangedAfterItHasBeenCheckedError exception.
      async (data) => { this.myData = await data }

Tested with Angular 5.2.9

BehaviorSubject vs Observable?

Observable and subject both are observable's means an observer can track them. but both of them have some unique characteristics. Further there are total 3 type of subjects each of them again have unique characteristics. lets try to to understand each of them.

you can find the practical example here on stackblitz. (You need to check the console to see the actual output)

enter image description here


They are cold: Code gets executed when they have at least a single observer.

Creates copy of data: Observable creates copy of data for each observer.

Uni-directional: Observer can not assign value to observable(origin/master).


They are hot: code gets executed and value gets broadcast even if there is no observer.

Shares data: Same data get shared between all observers.

bi-directional: Observer can assign value to observable(origin/master).

If are using using subject then you miss all the values that are broadcast before creation of observer. So here comes Replay Subject


They are hot: code gets executed and value get broadcast even if there is no observer.

Shares data: Same data get shared between all observers.

bi-directional: Observer can assign value to observable(origin/master). plus

Replay the message stream: No matter when you subscribe the replay subject you will receive all the broadcasted messages.

In subject and replay subject you can not set the initial value to observable. So here comes Behavioral Subject


They are hot: code gets executed and value get broadcast even if there is no observer.

Shares data: Same data get shared between all observers.

bi-directional: Observer can assign value to observable(origin/master). plus

Replay the message stream: No matter when you subscribe the replay subject you will receive all the broadcasted messages.

You can set initial value: You can initialize the observable with default value.

Updating to latest version of CocoaPods?

For those with a sudo-less CocoaPods installation (i.e., you do not want to grant RubyGems admin privileges), you don't need the sudo command to update your CocoaPods installation:

gem install cocoapods

You can find out where the CocoaPods gem is installed with:

gem which cocoapods

If this is within your home directory, you should definitely run gem install cocoapods without using sudo.

Finally, to check which CocoaPods you are currently running type:

pod --version

How to add SHA-1 to android application

For linux Ubuntu Open Terminal and Write :-

keytool -list -v -keystore ~/.android/debug.keystore -alias androiddebugkey -storepass android -keypass android

What is the meaning of <> in mysql query?

<> means NOT EQUAL TO, != also means NOT EQUAL TO. It's just another syntactic sugar. both <> and != are same.

The below two examples are doing the same thing. Query publisher table to bring results which are NOT EQUAL TO <> != USA.

SELECT pub_name,country,pub_city,estd FROM publisher WHERE country <> "USA";

SELECT pub_name,country,pub_city,estd FROM publisher WHERE country != "USA";

Can't bind to 'ngIf' since it isn't a known property of 'div'

If you are using RC5 then import this:

import { CommonModule } from '@angular/common';  
import { BrowserModule } from '@angular/platform-browser';

and be sure to import CommonModule from the module that is providing your component.

    imports: [CommonModule],
    declarations: [MyComponent]
class MyComponentModule {}

Clear an input field with Reactjs?

You can use input type="reset"

<form action="/action_page.php">
  text: <input type="text" name="email" /><br />  
  <input type="reset" defaultValue="Reset" />  

Convert a string to datetime in PowerShell

You can simply cast strings to DateTime:





$myDate = [DateTime]"Jul-16";

And you can format the resulting DateTime variable by doing something like this:

'{0:yyyy-MM-dd}' -f [DateTime]'Jul-16'




$myDate = [DateTime]"Jul-16";
'{0:yyyy-MM-dd}' -f $myDate

ImportError: No module named google.protobuf

To find where the name google clashes .... try this:


then >>> help('google')

... I got info about google-auth:


    auth (package)
    oauth2 (package)

Also then try

pip show google-auth


sudo pip3 uninstall google-auth

... and re-try >>> help('google')

I then see protobuf:


    protobuf (package)

Angular2 set value for formGroup

For set value when your control is FormGroup can use this example

      latitude: position.coords.latitude,
      longitude: position.coords.longitude

"OverflowError: Python int too large to convert to C long" on windows but not mac

Could anyone help explain why

In Python 2 a python "int" was equivalent to a C long. In Python 3 an "int" is an arbitrary precision type but numpy still uses "int" it to represent the C type "long" when creating arrays.

The size of a C long is platform dependent. On windows it is always 32-bit. On unix-like systems it is normally 32 bit on 32 bit systems and 64 bit on 64 bit systems.

or give a solution for the code on windows? Thanks so much!

Choose a data type whose size is not platform dependent. You can find the list at the most sensible choice would probably be np.int64

Check if a value is in an array or not with Excel VBA

The below function would return '0' if there is no match and a 'positive integer' in case of matching:

Function IsInArray(stringToBeFound As String, arr As Variant) As Integer IsInArray = InStr(Join(arr, ""), stringToBeFound) End Function ______________________________________________________________________________

Note: the function first concatenates the entire array content to a string using 'Join' (not sure if the join method uses looping internally or not) and then checks for a macth within this string using InStr.

Split / Explode a column of dictionaries into separate columns with pandas

How do I split a column of dictionaries into separate columns with pandas?

pd.DataFrame(df['val'].tolist()) is the canonical method for exploding a column of dictionaries

Here's your proof using a colorful graph.

enter image description here

Benchmarking code for reference.

Note that I am only timing the explosion since that's the most interesting part of answering this question - other aspects of result construction (such as whether to use pop or drop) are tangential to the discussion and can be ignored (it should be noted however that using pop avoids the followup drop call, so the final solution is a bit more performant, but we are still listifying the column and passing it to pd.DataFrame either way).

Additionally, pop destructively mutates the input DataFrame, making it harder to run in benchmarking code which assumes the input is not changed across test runs.

Critique of other solutions

  • df['val'].apply(pd.Series) is extremely slow for large N as pandas constructs Series objects for each row, then proceeds to construct a DataFrame from them. For larger N the performance dips to the order of minutes or hours.

  • pd.json_normalize(df['val'])) is slower simply because json_normalize is meant to work with a much more complex input data - particularly deeply nested JSON with multiple record paths and metadata. We have a simple flat dict for which pd.DataFrame suffices, so use that if your dicts are flat.

  • Some answers suggest df.pop('val').values.tolist() or df.pop('val').to_numpy().tolist(). I don't think it makes much of a difference whether you listify the series or the numpy array. It's one operation less to listify the series directly and really isn't slower so I'd recommend avoiding generating the numpy array in the intermediate step.

MongoDB: How to find the exact version of installed MongoDB

To check mongodb version use the mongod command with --version option.

To check MongoDB Server version, Open the command line via your terminal program and execute the following command:

Path : C:\Program Files\MongoDB\Server\3.2\bin Open Cmd and execute the following command: mongod --version To Check MongoDB Shell version, Type:

mongo --version

FCM getting MismatchSenderId

I was trying to send notification using the fcm api "" from postman. Server key was ok and token was pasted fine but was still getting error "MismatchSenderId".

Then introduced the follwoing dependency in the gradle file on android side.

implementation platform('') 

and it started receiving notifications on the device

Use of symbols '@', '&', '=' and '>' in custom directive's scope binding: AngularJS

> is not in the documentation.

< is for one-way binding.

@ binding is for passing strings. These strings support {{}} expressions for interpolated values.

= binding is for two-way model binding. The model in parent scope is linked to the model in the directive's isolated scope.

& binding is for passing a method into your directive's scope so that it can be called within your directive.

When we are setting scope: true in directive, Angular js will create a new scope for that directive. That means any changes made to the directive scope will not reflect back in parent controller.

How to return HTTP 500 from ASP.NET Core RC2 Web Api?

From what I can see there are helper methods inside the ControllerBase class. Just use the StatusCode method:

public IActionResult Post([FromBody] string something)
    catch(Exception e)
         return StatusCode(500);

You may also use the StatusCode(int statusCode, object value) overload which also negotiates the content.

What is FCM token in Firebase?

Here is simple steps add this gradle:

dependencies {
  compile ""

No extra permission are needed in manifest like GCM. No receiver is needed to manifest like GCM. With FCM, is added automatically.

Migrate your listener service

A service extending InstanceIDListenerService is now required only if you want to access the FCM token.

This is needed if you want to

  • Manage device tokens to send a messages to single device directly, or Send messages to device group, or
  • Send messages to device group, or
  • Subscribe devices to topics with the server subscription management API.

Add Service in manifest

        <action android:name="" />

        <action android:name=""/>

Change MyInstanceIDListenerService to extend FirebaseInstanceIdService, and update code to listen for token updates and get the token whenever a new token is generated.

public class MyInstanceIDListenerService extends FirebaseInstanceIdService {


   * Called if InstanceID token is updated. This may occur if the security of
   * the previous token had been compromised. Note that this is also called
   * when the InstanceID token is initially generated, so this is where
   * you retrieve the token.
  // [START refresh_token]
  public void onTokenRefresh() {
      // Get updated InstanceID token.
      String refreshedToken = FirebaseInstanceId.getInstance().getToken();
      Log.d(TAG, "Refreshed token: " + refreshedToken);
      // TODO: Implement this method to send any registration to your app's servers.


For more information visit

  1. How to import former GCM Projects into Firebase
  2. How to force a token refresh
  3. How to access the token
  4. How to set up firebase

How to unset (remove) a collection element after fetching it?

I'm not fine with solutions that iterates over a collection and inside the loop manipulating the content of even that collection. This can result in unexpected behaviour.

See also here: and in a comment the given link

So, when using foreach if seems to be OK but IMHO the much more readable and simple solution is to filter your collection to a new one.

 * Filter all `selected` items
 * @link
$selected = $collection->filter(function($value, $key) {
    return $value->selected;

How to call another components function in angular2

  1. Add injectable decorator to component2(or any component which have the method)
    providedIn: 'root'
  1. Inject into component1 (the component from where component2 method will be called)
constructor(public comp2 : component2) { }
  1. Define method in component1 from where component2 method is called

component 1 and component 2 code below.

import {Component2} from './Component2';

  selector: 'sel-comp1',
  templateUrl: './comp1.html',
  styleUrls: ['./comp1.scss']
export class Component1 implements OnInit {
  show = false;
  constructor(public comp2: Component2) { }

  selector: 'sel-comp2',
  templateUrl: './comp2.html',
  styleUrls: ['./comp2.scss']
export class Component2 implements OnInit {
  alert('called comp2 method from comp1');

Convert string to buffer Node

You can do:

var buf = Buffer.from(bufStr, 'utf8');

But this is a bit silly, so another suggestion would be to copy the minimal amount of code out of the called function to allow yourself access to the original buffer. This might be quite easy or fairly difficult depending on the details of that library.

How to Validate on Max File Size in Laravel?

According to the documentation:

$validator = Validator::make($request->all(), [
    'file' => 'max:500000',

The value is in kilobytes. I.e. max:10240 = max 10 MB.

JPA Hibernate Persistence exception [PersistenceUnit: default] Unable to build Hibernate SessionFactory

I found some issue about that kind of error

  1. Database username or password not match in the mysql or other other database. Please set like this


# =============================== # = DATA SOURCE # =============================== # Set here configurations for the database connection # Connection url for the database please let me know "[email protected]" spring.datasource.url = jdbc:mysql://localhost:3306/bookstoreapiabc # Username and secret spring.datasource.username = root spring.datasource.password = # Keep the connection alive if idle for a long time (needed in production) spring.datasource.testWhileIdle = true spring.datasource.validationQuery = SELECT 1 # =============================== # = JPA / HIBERNATE # =============================== # Use* for Hibernate native properties (the prefix is # stripped before adding them to the entity manager). # Show or not log for each sql query = true # Hibernate ddl auto (create, create-drop, update): with "update" the database # schema will be automatically updated accordingly to java entities found in # the project spring.jpa.hibernate.ddl-auto = update # Allows Hibernate to generate SQL optimized for a particular DBMS = org.hibernate.dialect.MySQL5Dialect

Issue no 2.

Your local server has two database server and those database server conflict. this conflict like this mysql server & xampp or lampp or wamp server. Please one of the database like mysql server because xampp or lampp server automatically install mysql server on this machine

Firebase cloud messaging notification not received by device

In my case, I manually killed some google play services and forgot about it.

Later, I have to restart the device, after that I can receive notification without any problem.

Differences between ConstraintLayout and RelativeLayout

Relative Layout and Constraint Layout equivalent properties

Relative Layout and Constraint Layout equivalent properties

(1) Relative Layout:


(1) Constraint Layout equivalent :


(2) Relative Layout:


(2) Constraint Layout equivalent:


(3) Relative Layout:


(3) Constraint Layout equivalent:


(4) Relative Layout:


(4) Constraint Layout equivalent:


(5) Relative Layout:


(5) Constraint Layout equivalent:


(6) Relative Layout:


(6) Constraint Layout equivalent:


(7) Relative Layout:


(7) Constraint Layout equivalent:


(8) Relative Layout:


(8) Constraint Layout equivalent:


(9) Relative Layout:


(9) Constraint Layout equivalent:


(10) Relative Layout:


(10) Constraint Layout equivalent:


(11) Relative Layout:


(11) Constraint Layout equivalent:


(12) Relative Layout:


(12) Constraint Layout equivalent:


(13) Relative Layout:


(13) Constraint Layout equivalent:


(14) Relative Layout:


(14) Constraint Layout equivalent:


(15) Relative Layout:


(15) Constraint Layout equivalent:


(16) Relative Layout:


(16) Constraint Layout equivalent:


(17) Relative Layout:


(17) Constraint Layout equivalent:


(18) Relative Layout:


(18) Constraint Layout equivalent:


(19) Relative Layout:


(19) Constraint Layout equivalent:


(20) Relative Layout:


(20) Constraint Layout equivalent:


(21) Relative Layout:


(21) Constraint Layout equivalent:


(22) Relative Layout:


(22) Constraint Layout equivalent:


Is the server running on host "localhost" (::1) and accepting TCP/IP connections on port 5432?

For Docker users: In my case it was caused by excessive docker image size. You can remove unused data using prune command:

docker system prune --all --force --volumes

Warning: as per manual (docker system prune --help):

This will remove:

  • all stopped containers
  • all networks not used by at least one container
  • all dangling images
  • all dangling build cache

Could not find method android() for arguments

guys. I had the same problem before when I'm trying import a .aar package into my project, and unfortunately before make the .aar package as a module-dependence of my project, I had two modules (one about ROS-ANDROID-CV-BRIDGE, one is OPENCV-FOR-ANDROID) already. So, I got this error as you guys meet:

Error:Could not find method android() for arguments [org.ros.gradle_plugins.RosAndroidPlugin$_apply_closure2_closure4@7e550e0e] on project ‘:xxx’ of type org.gradle.api.Project.

So, it's the painful gradle-structure caused this problem when you have several modules in your project, and worse, they're imported in different way or have different types (.jar/.aar packages or just a project of Java library). And it's really a headache matter to make the configuration like compile-version, library dependencies etc. in each subproject compatible with the main-project.

I solved my problem just follow this steps:

? Copy .aar package in app/libs.

? Add this in app/build.gradle file:

repositories {
    flatDir {
        dirs 'libs' //this way we can find the .aar file in libs folder

? Add this in your add build.gradle file of the module which you want to apply the .aar dependence (in my situation, just add this in my app/build.gradle file):

dependencies {
    compile(name:'package_name', ext:'aar')

So, if it's possible, just try export your module-dependence as a .aar package, and then follow this way import it to your main-project. Anyway, I hope this can be a good suggestion and would solve your problem if you have the same situation with me.

Checkbox value true/false

Checkboxes can be really weird in JS. You're best off checking for the presence of the checked attribute. (I've had older jQuery versions return true even if checked is set to 'false'.) Once you've determined that something is checked then you can get the value from the value attribute.

How to validate phone number in laravel 5.2?

    'phone' => 'numeric|required',
    'body' => 'required',

Running Node.Js on Android

Dory - node.js

Great New Application
No Need to root your Phone and You Can Run your js File From anywere.

  • node.js runtime(run ES2015/ES6, ES2016 javascript and node.js APIs in android)
  • API Documents and instant code run from doc
  • syntax highlighting code editor
  • npm supports
  • linux terminal(toybox 0.7.4). node.js REPL and npm command in shell (add '--no-bin-links' option if you execute npm in /sdcard)
  • StartOnBoot / LiveReload
  • native node.js binary and npm are included. no need to be online.

Update instruction to node js 8 (async await)

  1. Download node.js v8.3.0 arm zip file and unzip.

  2. copy 'node' to android's sdcard(/sdcard or /sdcard/path/to/...)

  3. open the shell(check it out in the app's menu)

  4. cd /data/user/0/io.tmpage.dorynode/files/bin (or, just type cd && cd .. && cd files/bin )

  5. rm node

  6. cp /sdcard/node .

  7. (chmod a+x node


Is there a way to specify which pytest tests to run from a file?

Maybe using pytest_collect_file() hook you can parse the content of a .txt o .yaml file where the tests are specify as you want, and return them to the pytest core.

A nice example is shown in the pytest documentation. I think what you are looking for.

PostgreSQL INSERT ON CONFLICT UPDATE (upsert) use all excluded values

Postgres hasn't implemented an equivalent to INSERT OR REPLACE. From the ON CONFLICT docs (emphasis mine):

It can be either DO NOTHING, or a DO UPDATE clause specifying the exact details of the UPDATE action to be performed in case of a conflict.

Though it doesn't give you shorthand for replacement, ON CONFLICT DO UPDATE applies more generally, since it lets you set new values based on preexisting data. For example:

INSERT INTO users (id, level)
VALUES (1, 0)
SET level = users.level + 1;

Angular2 get clicked element id

For nested html, use closest

<button (click)="toggle($event)" class="someclass" id="btn1">
    <i class="fa fa-user"></i>

toggle(event) {
   ('button') as Element).id; 

Format date as dd/MM/yyyy using pipes

You have to pass the locale string as an argument to DatePipe.

var ddMMyyyy = this.datePipe.transform(new Date(),"dd-MM-yyyy");

Pre-defined format options:

1.      'short': equivalent to 'M/d/yy, h:mm a' (6/15/15, 9:03 AM).
2.      'medium': equivalent to 'MMM d, y, h:mm:ss a' (Jun 15, 2015, 9:03:01 AM).
3.      'long': equivalent to 'MMMM d, y, h:mm:ss a z' (June 15, 2015 at 9:03:01 AM GMT+1).
4.      'full': equivalent to 'EEEE, MMMM d, y, h:mm:ss a zzzz' (Monday, June 15, 2015 at 9:03:01 AM GMT+01:00).
5.      'shortDate': equivalent to 'M/d/yy' (6/15/15).
6.      'mediumDate': equivalent to 'MMM d, y' (Jun 15, 2015).
7.      'longDate': equivalent to 'MMMM d, y' (June 15, 2015).
8.      'fullDate': equivalent to 'EEEE, MMMM d, y' (Monday, June 15, 2015).
9.      'shortTime': equivalent to 'h:mm a' (9:03 AM).
10. 'mediumTime': equivalent to 'h:mm:ss a' (9:03:01 AM).
11. 'longTime': equivalent to 'h:mm:ss a z' (9:03:01 AM GMT+1).
12. 'fullTime': equivalent to 'h:mm:ss a zzzz' (9:03:01 AM GMT+01:00).

add datepipe in app.component.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import {DatePipe} from '@angular/common';
  declarations: [
  imports: [
  providers: [
  bootstrap: [AppComponent]
export class AppModule { }


When you are using a self signed cert urllib3 version 1.25.3 refuses to ignore the SSL cert

To fix remove urllib3-1.25.3 and install urllib3-1.24.3

pip3 uninstall urllib3

pip3 install urllib3==1.24.3

Tested on Linux MacOS and Window$

How to know elastic search installed version from kibana?

I would like to add which isn't mentioned in above answers.

From your kibana's dev console, hit following command:


This is similar to accessing localhost:9200 from browser.

Hope this will help someone.

TypeError: tuple indices must be integers, not str

I think you should do

for index, row in result: 

If you wanna access by name.

How to change the Jupyter start-up folder

Easy way!

1 - Type jupyer notebook in start menu


2 - Make shortcut on desktop of jupyter notebook ( Right click mouse!)


3 - Only drag and drop your favorite folder in the shortcut

Async await in linq select

I prefer this as an extension method:

public static async Task<IEnumerable<T>> WhenAll<T>(this IEnumerable<Task<T>> tasks)
    return await Task.WhenAll(tasks);

So that it is usable with method chaining:

var inputs = await events
  .Select(async ev => await ProcessEventAsync(ev))

How to get user's high resolution profile picture on Twitter?

use this URL : ""

If you are using TWitter SDK you can get the user name when logged in, with TWTRAPIClient, using TWTRAuthSession.

This is the code snipe for iOS:

if let twitterId = session.userID{
   let twitterClient = TWTRAPIClient(userID: twitterId)
   twitterClient.loadUser(withID: twitterId) {(user, error) in
       if let userName = user?.screenName{
          let url = "\(userName)/profile_image?size=original")

HTTP 415 unsupported media type error when calling Web API 2 endpoint

I was trying to write a code that would work on both Mac and Windows. The code was working fine on Windows, but was giving the response as 'Unsupported Media Type' on Mac. Here is the code I used and the following line made the code work on Mac as well:

Request.AddHeader "Content-Type", "application/json"

Here is the snippet of my code:

Dim Client As New WebClient
Dim Request As New WebRequest
Dim Response As WebResponse
Dim Distance As String

Client.BaseUrl = ""
Request.AddHeader "Content-Type", "application/json" *** The line that made the code work on mac

Set Response = Client.Execute(Request)

How to install Android SDK on Ubuntu?

sudo add-apt-repository -y ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer oracle-java7-set-default
cd android-studio/bin

Why is my JQuery selector returning a n.fn.init[0], and what is it?

Another approach(Inside of $function to asure that the each is executed on document ready):

var ids = [1,2];
    if(ids.indexOf($(item).data('id')) > -1){
       $(item).prop("checked", "checked");

Working fiddle:

What is the n.fn.init[0], and why it is returned? Why are my two seemingly identical JQuery functions returning different things?

Answer: It seems that your elements are not in the DOM yet, when you are trying to find them. As @Rory McCrossan pointed out, the length:0 means that it doesn't find any element based on your search criteria.

About n.fn.init[0], lets look at the core of the Jquery Library:

var jQuery = function( selector, context ) {
   return new jQuery.fn.init( selector, context );

Looks familiar, right?, now in a minified version of jquery, this should looks like:

var n = function( selector, context ) {
   return new n.fn.init( selector, context );

So when you use a selector you are creating an instance of the jquery function; when found an element based on the selector criteria it returns the matched elements; when the criteria does not match anything it returns the prototype object of the function.

How to send an HTTP request with a header parameter?

If it says the API key is listed as a header, more than likely you need to set it in the headers option of your http request. Normally something like this :

headers: {'Authorization': '[your API key]'}

Here is an example from another Question

$http({method: 'GET', url: '[the-target-url]', headers: {
  'Authorization': '[your-api-key]'}

Edit : Just saw you wanted to store the response in a variable. In this case I would probably just use AJAX. Something like this :

   type : "GET", 
   url : "[the-target-url]", 
   beforeSend: function(xhr){xhr.setRequestHeader('Authorization', '[your-api-key]');},
   success : function(result) { 
       //set your variable to the result 
   error : function(result) { 
     //handle the error 

I got this from this question and I'm at work so I can't test it at the moment but looks solid

Edit 2: Pretty sure you should be able to use this line :

headers: {'Authorization': '[your API key]'},

instead of the beforeSend line in the first edit. This may be simpler for you

Using NotNull Annotation in method argument

As mentioned above @NotNull does nothing on its own. A good way of using @NotNull would be using it with Objects.requireNonNull

public class Foo {
    private final Bar bar;

    public Foo(@NotNull Bar bar) { = Objects.requireNonNull(bar, "bar must not be null");

How to add header row to a pandas DataFrame

Alternatively you could read you csv with header=None and then add it with df.columns:

Cov = pd.read_csv("path/to/file.txt", sep='\t', header=None)
Cov.columns = ["Sequence", "Start", "End", "Coverage"]

What does from __future__ import absolute_import actually do?

The changelog is sloppily worded. from __future__ import absolute_import does not care about whether something is part of the standard library, and import string will not always give you the standard-library module with absolute imports on.

from __future__ import absolute_import means that if you import string, Python will always look for a top-level string module, rather than current_package.string. However, it does not affect the logic Python uses to decide what file is the string module. When you do

python pkg/

pkg/ doesn't look like part of a package to Python. Following the normal procedures, the pkg directory is added to the path, and all .py files in the pkg directory look like top-level modules. import string finds pkg/ not because it's doing a relative import, but because pkg/ appears to be the top-level module string. The fact that this isn't the standard-library string module doesn't come up.

To run the file as part of the pkg package, you could do

python -m pkg.script

In this case, the pkg directory will not be added to the path. However, the current directory will be added to the path.

You can also add some boilerplate to pkg/ to make Python treat it as part of the pkg package even when run as a file:

if __name__ == '__main__' and __package__ is None:
    __package__ = 'pkg'

However, this won't affect sys.path. You'll need some additional handling to remove the pkg directory from the path, and if pkg's parent directory isn't on the path, you'll need to stick that on the path too.

Gradle Error:Execution failed for task ':app:processDebugGoogleServices'

In my case when i was using firebase services the google.json file was mismatched check once that also

Can a website detect when you are using Selenium with chromedriver?

One more thing I found is that some websites uses a platform that checks the User Agent. If the value contains: "HeadlessChrome" the behavior can be weird when using headless mode.

The workaround for that will be to override the user agent value, for example in Java:

chromeOptions.addArguments("--user-agent=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36");

How to uninstall jupyter

If you installed Jupiter notebook through anaconda, this may help you:

conda uninstall jupyter notebook

COPYing a file in a Dockerfile, no such file or directory?

I feel a little stupid, but my issue was that I was running docker-compose, and my Dockerfile was in a ./deploy subdirectory. My ADD reference needed to be relative to the root of the project, not the Dockerfile.

Changed: ADD ./file.tar.gz /etc/folder/ to: ADD ./deploy/file.tar.gz /etc/folder/

Anyhow, thought I'd post in case someone ran into the same issue.

How link to any local file with markdown syntax?

Thank you drifty0pine!

The first solution, it´s works!

[a relative link](../../some/dir/
[Link to file in another dir on same drive](/another/dir/
[Link to file in another dir on a different drive](/D:/dir/

but I had need put more ../ until the folder where was my file, like this:


Logging with Retrofit 2

The main problem which I faced was dynamical adding headers and logging them into debug logcat. I've tried to add two interceptors. One for logging and one for adding headers on-the-go (token authorization). The problem was that we may .addInterceptor or .addNetworkInterceptor. As Jake Wharton said to me: "Network interceptors always come after application interceptors. See". So here is working example with headers and logs:

OkHttpClient httpClient = new OkHttpClient.Builder()
            //here we can add Interceptor for dynamical adding headers
            .addNetworkInterceptor(new Interceptor() {
                public Response intercept(Chain chain) throws IOException {
                    Request request = chain.request().newBuilder().addHeader("test", "test").build();
                    return chain.proceed(request);
            //here we adding Interceptor for full level logging
            .addNetworkInterceptor(new HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY))

    Retrofit retrofit = new Retrofit.Builder()

Explain ggplot2 warning: "Removed k rows containing missing values"

I ran into this as well, but in the case where I wanted to avoid the extra error messages while keeping the range provided. An option is also to subset the data prior to setting the range, so that the range can be kept however you like without triggering warnings.


#> [1]  52 335

# Setting limits with scale_y_continous (or ylim) and subsetting accordingly
## avoid warning messages about removing data
ggplot(data= subset(mtcars, hp<=300 & hp >= 100), aes(mpg, hp)) + 
  geom_point() +

What are NR and FNR and what does "NR==FNR" imply?

There are awk built-in variables.

NR - It gives the total number of records processed.

FNR - It gives the total number of records for each input file.

Git push: "fatal 'origin' does not appear to be a git repository - fatal Could not read from remote repository."

These two steps worked for me!

Step 1:

git remote set-url origin

Step 2:

git push --set-upstream -f origin main

Step 3:

your username and password for github

On step 2, -f is actually required because of the rebase, quote from this post.

What exactly is std::atomic?

I understand that std::atomic<> makes an object atomic.

That's a matter of perspective... you can't apply it to arbitrary objects and have their operations become atomic, but the provided specialisations for (most) integral types and pointers can be used.

a = a + 12;

std::atomic<> does not (use template expressions to) simplify this to a single atomic operation, instead the operator T() const volatile noexcept member does an atomic load() of a, then twelve is added, and operator=(T t) noexcept does a store(t).

What exactly does numpy.exp() do?

The exponential function is e^x where e is a mathematical constant called Euler's number, approximately 2.718281. This value has a close mathematical relationship with pi and the slope of the curve e^x is equal to its value at every point. np.exp() calculates e^x for each value of x in your input array.

Check if a file exists or not in Windows PowerShell?

Use Test-Path:

if (!(Test-Path $exactadminfile) -and !(Test-Path $userfile)) {
  Write-Warning "$userFile absent from both locations"

Placing the above code in your ForEach loop should do what you want

LDAP: error code 49 - 80090308: LdapErr: DSID-0C0903A9, comment: AcceptSecurityContext error, data 52e, v1db1

LDAP is trying to authenticate with AD when sending a transaction to another server DB. This authentication fails because the user has recently changed her password, although this transaction was generated using the previous credentials. This authentication will keep failing until ... unless you change the transaction status to Complete or Cancel in which case LDAP will stop sending these transactions.

Module is not available, misspelled or forgot to load (but I didn't)

Using AngularJS 1.6.9+

There is one more incident, it also happen when you declare variable name different of module name.

var indexPageApp = angular.module('indexApp', []);

to get rid of this error,

Error: [$injector:nomod] Module 'indexPageApp' is not available! You either misspelled the module name or forgot to load it. If registering a module ensure that you specify the dependencies as the second argument.

change the module name similar to var declared name or vice versa -

var indexPageApp = angular.module('indexPageApp', []);

Activity, AppCompatActivity, FragmentActivity, and ActionBarActivity: When to Use Which?

If you talk about Activity, AppcompactActivity, ActionBarActivity etc etc..

We need to talk about Base classes which they are extending, First we have to understand the hierarchy of super classes.

All the things are started from Context which is super class for all these classes.

Context is an abstract class whose implementation is provided by the Android system. It allows access to application-specific resources and classes, as well as up-calls for application-level operations such as launching activities, broadcasting and receiving intents, etc

Context is followed by or extended by ContextWrapper

The ContextWrapper is a class which extend Context class that simply delegates all of its calls to another Context. Can be subclassed to modify behavior without changing the original Context.

Now we Reach to Activity

The Activity is a class which extends ContextThemeWrapper that is a single, focused thing that the user can do. Almost all activities interact with the user, so the Activity class takes care of creating a window for you

Below Classes are restricted to extend but they are extended by their descender internally and provide support for specific Api

The SupportActivity is a class which extends Activity that is a Base class for composing together compatibility functionality

The BaseFragmentActivityApi14 is a class which extends SupportActivity that is a Base class It is restricted class but it is extend by BaseFragmentActivityApi16 to support the functionality of V14

The BaseFragmentActivityApi16 is a class which extends BaseFragmentActivityApi14 that is a Base class for {@code FragmentActivity} to be able to use v16 APIs. But it is also restricted class but it is extend by FragmentActivity to support the functionality of V16.

now FragmentActivty

The FragmentActivity is a class which extends BaseFragmentActivityApi16 and that wants to use the support-based Fragment and Loader APIs.

When using this class as opposed to new platform's built-in fragment and loader support, you must use the getSupportFragmentManager() and getSupportLoaderManager() methods respectively to access those features.

ActionBarActivity is part of the Support Library. Support libraries are used to deliver newer features on older platforms. For example the ActionBar was introduced in API 11 and is part of the Activity by default (depending on the theme actually). In contrast there is no ActionBar on the older platforms. So the support library adds a child class of Activity (ActionBarActivity) that provides the ActionBar's functionality and ui

In 2015 ActionBarActivity is deprecated in revision 22.1.0 of the Support Library. AppCompatActivity should be used instead.

The AppcompactActivity is a class which extends FragmentActivity that is Base class for activities that use the support library action bar features.

You can add an ActionBar to your activity when running on API level 7 or higher by extending this class for your activity and setting the activity theme to Theme.AppCompat or a similar theme


I refer these two one,two

Excel doesn't update value unless I hit Enter

Select all the data and use the option "Text to Columns", that will allow your data for Applying Number Formatting ERIK

Logarithmic returns in pandas dataframe

Here is one way to calculate log return using .shift(). And the result is similar to but not the same as the gross return calculated by pct_change(). Can you upload a copy of your sample data (dropbox share link) to reproduce the inconsistency you saw?

import pandas as pd
import numpy as np

df = pd.DataFrame(100 + np.random.randn(100).cumsum(), columns=['price'])
df['pct_change'] = df.price.pct_change()
df['log_ret'] = np.log(df.price) - np.log(df.price.shift(1))

       price  pct_change  log_ret
0   101.7641         NaN      NaN
1   102.1642      0.0039   0.0039
2   103.1429      0.0096   0.0095
3   105.3838      0.0217   0.0215
4   107.2514      0.0177   0.0176
5   106.2741     -0.0091  -0.0092
6   107.2242      0.0089   0.0089
7   107.0729     -0.0014  -0.0014
..       ...         ...      ...
92  101.6160      0.0021   0.0021
93  102.5926      0.0096   0.0096
94  102.9490      0.0035   0.0035
95  103.6555      0.0069   0.0068
96  103.6660      0.0001   0.0001
97  105.4519      0.0172   0.0171
98  105.5788      0.0012   0.0012
99  105.9808      0.0038   0.0038

[100 rows x 3 columns]

How can I see function arguments in IPython Notebook Server 3?

Try Shift-Tab-Tab a bigger documentation appears, than with Shift-Tab. It's the same but you can scroll down.

Shift-Tab-Tab-Tab and the tooltip will linger for 10 seconds while you type.

Shift-Tab-Tab-Tab-Tab and the docstring appears in the pager (small part at the bottom of the window) and stays there.

reCAPTCHA ERROR: Invalid domain for site key

I had the same problems I solved it. I went to and clicked on the domain and then went to key settings at the bottom.

There I disabled the the option below Domain Name Validation Verify the origin of reCAPTCHA solution

clicked on save and captcha started working.

I think this has to do with way the server is setup. I am on a shared hosting and just was transferred without notice from Liquidweb to Deluxehosting(as the former sold their share hosting to the latter) and have been having such problems with many issues. I think in this case google is checking the server but it is identifying as shared server name and not my domain. When i uncheck the "verify origin" it starts working. Hope this helps solve the problem for the time being.

Flexbox: how to get divs to fill up 100% of the container width without wrapping?

You can use the shorthand flex property and set it to

flex: 0 0 100%;

That's flex-grow, flex-shrink, and flex-basis in one line. Flex shrink was described above, flex grow is the opposite, and flex basis is the size of the container.

beyond top level package error in relative import

if you have an in an upper folder, you can initialize the import as import file/path as alias in that init file. Then you can use it on lower scripts as:

import alias

Why does Oracle not find oci.dll?

I just added the oracle folder to my environmental variables and that fixed my identical error

Android Firebase, simply get one child object's data

You don't directly read a value. You can set it with .setValue(), but there is no .getValue() on the reference object.

You have to use a listener. If you just want to read the value once, you use ref.addListenerForSingleValueEvent().


Firebase ref = new Firebase("YOUR-URL-HERE/PATH/TO/YOUR/STUFF");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
   public void onDataChange(DataSnapshot dataSnapshot) {
       String value = (String) dataSnapshot.getValue();

       // do your stuff here with value


   public void onCancelled(FirebaseError firebaseError) {



Oracle SQL - DATE greater than statement

you have to use the To_Date() function to convert the string to date !

Guzzlehttp - How get the body of a response from Guzzle 6?

If expecting JSON back, the simplest way to get it:

$data = json_decode($response->getBody()); // returns an object

// OR

$data = json_decode($response->getBody(), true); // returns an array

json_decode() will automatically cast the body to string, so there is no need to call getContents().

How to solve : SQL Error: ORA-00604: error occurred at recursive SQL level 1

I noticed following line from error.

exact fetch returns more than requested number of rows

That means Oracle was expecting one row but It was getting multiple rows. And, only dual table has that characteristic, which returns only one row.

Later I recall, I have done few changes in dual table and when I executed dual table. Then found multiple rows.

So, I truncated dual table and inserted only row which X value. And, everything working fine.

How does Content Security Policy (CSP) work?

The Content-Security-Policy meta-tag allows you to reduce the risk of XSS attacks by allowing you to define where resources can be loaded from, preventing browsers from loading data from any other locations. This makes it harder for an attacker to inject malicious code into your site.

I banged my head against a brick wall trying to figure out why I was getting CSP errors one after another, and there didn't seem to be any concise, clear instructions on just how does it work. So here's my attempt at explaining some points of CSP briefly, mostly concentrating on the things I found hard to solve.

For brevity I won’t write the full tag in each sample. Instead I'll only show the content property, so a sample that says content="default-src 'self'" means this:

<meta http-equiv="Content-Security-Policy" content="default-src 'self'">

1. How can I allow multiple sources?

You can simply list your sources after a directive as a space-separated list:

content="default-src 'self'"

Note that there are no quotes around parameters other than the special ones, like 'self'. Also, there's no colon (:) after the directive. Just the directive, then a space-separated list of parameters.

Everything below the specified parameters is implicitly allowed. That means that in the example above these would be valid sources:

These, however, would not be valid:
^^^^ wrong protocol
                   ^^ above the specified path

2. How can I use different directives? What do they each do?

The most common directives are:

  • default-src the default policy for loading javascript, images, CSS, fonts, AJAX requests, etc
  • script-src defines valid sources for javascript files
  • style-src defines valid sources for css files
  • img-src defines valid sources for images
  • connect-src defines valid targets for to XMLHttpRequest (AJAX), WebSockets or EventSource. If a connection attempt is made to a host that's not allowed here, the browser will emulate a 400 error

There are others, but these are the ones you're most likely to need.

3. How can I use multiple directives?

You define all your directives inside one meta-tag by terminating them with a semicolon (;):

content="default-src 'self'; style-src 'self'"

4. How can I handle ports?

Everything but the default ports needs to be allowed explicitly by adding the port number or an asterisk after the allowed domain:

content="default-src 'self'"

The above would result in:
                           ^^^^ Not ok, wrong port - OK
                 ^^ Not ok, only the port 123 is allowed - OK

As I mentioned, you can also use an asterisk to explicitly allow all ports:


5. How can I handle different protocols?

By default, only standard protocols are allowed. For example to allow WebSockets ws:// you will have to allow it explicitly:

content="default-src 'self'; connect-src ws:; style-src 'self'"
                                         ^^^ web Sockets are now allowed on all domains and ports.

6. How can I allow the file protocol file://?

If you'll try to define it as such it won’t work. Instead, you'll allow it with the filesystem parameter:

content="default-src filesystem"

7. How can I use inline scripts and style definitions?

Unless explicitly allowed, you can't use inline style definitions, code inside <script> tags or in tag properties like onclick. You allow them like so:

content="script-src 'unsafe-inline'; style-src 'unsafe-inline'"

You'll also have to explicitly allow inline, base64 encoded images:

content="img-src data:"

8. How can I allow eval()?

I'm sure many people would say that you don't, since 'eval is evil' and the most likely cause for the impending end of the world. Those people would be wrong. Sure, you can definitely punch major holes into your site's security with eval, but it has perfectly valid use cases. You just have to be smart about using it. You allow it like so:

content="script-src 'unsafe-eval'"

9. What exactly does 'self' mean?

You might take 'self' to mean localhost, local filesystem, or anything on the same host. It doesn't mean any of those. It means sources that have the same scheme (protocol), same host, and same port as the file the content policy is defined in. Serving your site over HTTP? No https for you then, unless you define it explicitly.

I've used 'self' in most examples as it usually makes sense to include it, but it's by no means mandatory. Leave it out if you don't need it.

But hang on a minute! Can't I just use content="default-src *" and be done with it?

No. In addition to the obvious security vulnerabilities, this also won’t work as you'd expect. Even though some docs claim it allows anything, that's not true. It doesn't allow inlining or evals, so to really, really make your site extra vulnerable, you would use this:

content="default-src * 'unsafe-inline' 'unsafe-eval'"

... but I trust you won’t.

Further reading:

How to add element in Python to the end of list using list.insert?

list.insert with any index >= len(of_the_list) places the value at the end of list. It behaves like append

Python 3.7.4
>>>lst.insert(len(lst), 101)
[10, 20, 30, 101]
>>>lst.insert(len(lst)+50, 202)
[10, 20, 30, 101, 202]

Time complexity, append O(1), insert O(n)

Using an authorization header with Fetch in React Native

completed = (id) => {
    var details = {
        'id': id,


    var formBody = [];
    for (var property in details) {
        var encodedKey = encodeURIComponent(property);
        var encodedValue = encodeURIComponent(details[property]);
        formBody.push(encodedKey + "=" + encodedValue);
    formBody = formBody.join("&");

    fetch(markcompleted, {
        method: 'POST',
        headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/x-www-form-urlencoded'
        body: formBody
        .then((response) => response.json())
        .then((responseJson) => {
            console.log(responseJson, 'res JSON');
            if (responseJson.status == "success") {
                alert("your todolist is completed!!");
        .catch((error) => {

How can I print out just the index of a pandas dataframe?

You can use lamba function:

index = df.index[lambda x : for x in df.index() ]

How do I jump to a closing bracket in Visual Studio Code?

You can learn commands from the command palette Ctrl/Cmd + Shift + P). Look for "Go to Bracket". The keybinding is also shown there.


Check the nginx folder permission and set appache permission for that:

chown -R www-data:www-data /var/lib/nginx

Error - replacement has [x] rows, data has [y]

TL;DR ...and late to the party, but that short explanation might help future googlers..

In general that error message means that the replacement doesn't fit into the corresponding column of the dataframe.

A minimal example:

df <- data.frame(a = 1:2); df$a <- 1:3

throws the error

Error in $<*tmp*, a, value = 1:3) : replacement has 3 rows, data has 2

which is clear, because the vector a of df has 2 entries (rows) whilst the vector we try to replace it has 3 entries (rows).

How to check if any value is NaN in a Pandas DataFrame

Or you can use .info() on the DF such as : which returns the number of non_null rows in a columns such as:

<class 'pandas.core.frame.DataFrame'>
Int64Index: 3276314 entries, 0 to 3276313
Data columns (total 10 columns):
n_matches                          3276314 non-null int64
avg_pic_distance                   3276314 non-null float64

Convert Map to JSON using Jackson

You should prefer Object Mapper instead. Here is the link for the same : Object Mapper - Spring MVC way of Obect to JSON

What exactly does the T and Z mean in timestamp?

The T doesn't really stand for anything. It is just the separator that the ISO 8601 combined date-time format requires. You can read it as an abbreviation for Time.

The Z stands for the Zero timezone, as it is offset by 0 from the Coordinated Universal Time (UTC).

Both characters are just static letters in the format, which is why they are not documented by the datetime.strftime() method. You could have used Q or M or Monty Python and the method would have returned them unchanged as well; the method only looks for patterns starting with % to replace those with information from the datetime object.

Karma: Running a single test file from command line

Even though --files is no longer supported, you can use an env variable to provide a list of files:

// karma.conf.js
function getSpecs(specList) {
  if (specList) {
    return specList.split(',')
  } else {
    return ['**/*_spec.js'] // whatever your default glob is

module.exports = function(config) {
    files: ['app.js'].concat(getSpecs(process.env.KARMA_SPECS))

Then in CLI:

$ env KARMA_SPECS="spec1.js,spec2.js" karma start karma.conf.js --single-run

Android Studio Run/Debug configuration error: Module not specified

I would like to add some more information while I was facing this issue:

Ref: Answer from @Eli:

  1. Cut line include ':app' from the file.
  2. On Android Studio, click on the File Menu, and select Sync Project with Gradle files.
  3. After synchronisation, paste back line include ':app' to the settings.gradle file.
  4. Re-run Sync Project with Gradle files again.

So, let's follow the instruction and try to keep one thing in mind, that what is showing in your build configuration. Make sure you are seeing the name of your configuration app like the image below:

enter image description here

If you are seeing anything else, then the steps mentioned by @Eli (the most accepted answer) will not work.

An alternative Solution If you have a different name on the Run/Debug Configurations window and the above process is not working, please change the config name to 'app'

then -> hit Apply -> then Ok.

After that follow this:-

File->Sync project with gradle files (if needed).

Now check the issue will be resolved hopefully. I have faced this issue and I think it might help others as well.

php codeigniter count rows

This is what is did that solved the same problem. I solved it by creating a function that returns the query result thus:

function getUsers(){
$query = $this->db->get('users');
return $query->result();

//The above code can go in the user_model or whatever your model is.

This allows me to use one function for the result and number of returned rows.

Use this code below in your contoller where you need the count as well as the result array().

//This gives you the user count using the count function which returns and integer of the exact rows returned from the query.
$this->data['user_count'] = count($this->user_model->getUsers());

//This gives you the returned result array.
$this->data['users'] = $this->user_model->getUsers();

I hope this helps.

Jquery-How to grey out the background while showing the loading icon over it

I reworked the example you provided in the js fiddle :

Step 1 :

I renamed your container div to overlay, as semantically this div is not a container, but an overlay. I also placed the loader div as a child of this overlay div.

The resulting html is :

<div class="overlay">
    <div id="loading-img"></div>

<div class="content">
    <div>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ea velit provident sint aliquid eos omnis aperiam officia architecto error incidunt nemo obcaecati adipisci doloremque dicta neque placeat natus beatae cupiditate minima ipsam quaerat explicabo non reiciendis qui sit. ...</div>
    <button id="button">Submit</button>

The css of the overlay is the following

.overlay {
    background: #e9e9e9;  <- I left your 'gray' background
    display: none;        <- Not displayed by default
    position: absolute;   <- This and the following properties will
    top: 0;                  make the overlay, the element will expand
    right: 0;                so as to cover the whole body of the page
    bottom: 0;
    left: 0;
    opacity: 0.5;

Step 2 :

I added some dummy text so as to have something to overlay.

Step 3 :

Then, in the click handler we just need to show the overlay :

$("#button").click(function () {

How to use curl to get a GET request exactly same as using Chrome?

Open Chrome Developer Tools, go to Network tab, make your request (you may need to check "Preserve Log" if the page refreshes). Find the request on the left, right-click, "Copy as cURL".

Why do I get PLS-00302: component must be declared when it exists?

I came here because I had the same problem.
What was the problem for me was that the procedure was defined in the package body, but not in the package header.
I was executing my function with a lose BEGIN END statement.

What exactly is the difference between Web API and REST API in MVC?

ASP.NET Web API is a framework that makes it easy to build HTTP services that reach a broad range of clients, including browsers and mobile devices. ASP.NET Web API is an ideal platform for building RESTful applications on the .NET Framework.


RESTs sweet spot is when you are exposing a public API over the internet to handle CRUD operations on data. REST is focused on accessing named resources through a single consistent interface.


SOAP brings it’s own protocol and focuses on exposing pieces of application logic (not data) as services. SOAP exposes operations. SOAP is focused on accessing named operations, each implement some business logic through different interfaces.

Though SOAP is commonly referred to as “web services” this is a misnomer. SOAP has very little if anything to do with the Web. REST provides true “Web services” based on URIs and HTTP.


And finally: What they could be referring to is REST vs. RPC See this:

Converting rows into columns and columns into rows using R

Simply use the base transpose function t, wrapped with

final_df <-
     A    B    C    D
a    1    2    3    4
b 0.02 0.04 0.06 0.08
c Aaaa Bbbb Cccc Dddd

Above updated. As docendo discimus pointed out, t returns a matrix. As Mark suggested wrapping it with gets back a data frame instead of a matrix. Thanks!

Refreshing data in RecyclerView and keeping its scroll position

Here is an option for people who use DataBinding for RecyclerView. I have var recyclerViewState: Parcelable? in my adapter. And I use a BindingAdapter with a variation of @DawnYu's answer to set and update data in the RecyclerView:

fun setRecyclerViewItems(
    recyclerView: RecyclerView,
    items: List<RecyclerViewItem>?
) {
    var adapter = (recyclerView.adapter as? RecyclerViewAdapter)
    if (adapter == null) {
        adapter = RecyclerViewAdapter()
        recyclerView.adapter = adapter

    adapter.recyclerViewState = recyclerView.layoutManager?.onSaveInstanceState()
    // the main idea is in this call with a lambda. It allows to avoid blinking on data update
    adapter.submitList(items.orEmpty()) {
        adapter.recyclerViewState?.let {

Finally, the XML part looks like:


How does the Spring @ResponseBody annotation work?

@RequestBody annotation binds the HTTPRequest body to the domain object. Spring automatically deserializes incoming HTTP Request to object using HttpMessageConverters. HttpMessageConverter converts body of request to resolve the method argument depending on the content type of the request. Many examples how to use converters

Fatal error: Call to a member function prepare() on null

It looks like your $pdo variable is not initialized. I can't see in the code you've uploaded where you are initializing it.

Make sure you create a new PDO object in the global scope before calling the class methods. (You should declare it in the global scope because of how you implemented the methods inside the Category class).

$pdo = new PDO('mysql:host=localhost;dbname=test', $user, $pass);

How do I get HTTP Request body content in Laravel?

Inside controller inject Request object. So if you want to access request body inside controller method 'foo' do the following:

public function foo(Request $request){
    $bodyContent = $request->getContent();

What does question mark and dot operator ?. mean in C# 6.0?

This is relatively new to C# which makes it easy for us to call the functions with respect to the null or non-null values in method chaining.

old way to achieve the same thing was:

var functionCaller = this.member;
if (functionCaller!= null)
    functionCaller.someFunction(var someParam);

and now it has been made much easier with just:

member?.someFunction(var someParam);

I strongly recommend this doc page.

How to push a docker image to a private repository

First go to your Docker Hub account and make the repo. Here is a screenshot of my Docker Hub account: enter image description here

From the pic, you can see my repo is “chuangg”

Now go into the repo and make it private by clicking on your image’s name. So for me, I clicked on “chuangg/gene_commited_image”, then I went to Settings -> Make Private. Then I followed the on screen instructions enter image description here


Method #1= Pushing your image through the command line (cli)

1) docker commit <container ID> <repo name>/<Name you want to give the image>

Yes, I think it has to be the container ID. It probably cannot be the image ID.

For example= docker commit 99e078826312 chuangg/gene_commited_image

2) docker run -it chaung/gene_commited_image

3) docker login --username=<user username> --password=<user password>

For example= docker login --username=chuangg [email protected]

Yes, you have to login first. Logout using “docker logout”

4) docker push chuangg/gene_commited_image

Method #2= Pushing your image using pom.xml and command line.

Note, I used a Maven Profile called “build-docker”. If you don’t want to use a profile, just remove the <profiles>, <profile>, and <id>build-docker</id> elements.

Inside the parent pom.xml:

                                    <!-- Configure build settings -->

Docker Terminal Command to deploy the Docker Image (from the directory where your pom.xml is located)= mvn clean deploy -Pbuild-docker docker:push

Note, the difference between Method #2 and #3 is that Method #3 has an extra <execution> for the deployment.

Method #3= Using Maven to automatically deploy to Docker Hub

Add this stuff to your parent pom.xml:



                                    <!-- Configure build settings -->


Go to C:\Users\Gene.docker\ directory and add this to your config.json file: enter image description here

Now in your Docker Quickstart Terminal type= mvn clean install -Pbuild-docker

For those of you not using Maven Profiles, just type mvn clean install

Here is the screenshot of the success message: enter image description here

Here is my full pom.xml and a screenshot of my directory structure:

<project xmlns="" xmlns:xsi=""



<name>Maven Quick Start Archetype</name>








                                <!-- Configure build settings -->


Here is my Eclipse Directory: enter image description here

Here is my Dockerfile:

FROM java:8

RUN echo Running Dockerfile in src/docker/vending_machine_emulator/Dockerfile directory

ADD maven/VendingMachineDockerMavenPlugin-1.0-SNAPSHOT.jar /bullshitDirectory/gene-app-1.0-SNAPSHOT.jar 

CMD ["java", "-classpath", "/bullshitDirectory/gene-app-1.0-SNAPSHOT.jar", "com/gene/sample/Customer_View" ] 

Common Error #1: enter image description here

Solution for Error #1= Do not sync the <execution> with maven deploy phase because then maven tries to deploy the image 2x and puts a timestamp on the jar. That’s why I used <phase>install</phase>.

Error: Microsoft Visual C++ 10.0 is required (Unable to find vcvarsall.bat) when running Python script

I got the same error and ended up using a pre-built distribution of numpy available in SourceForge (similarly, a distribution of matplotlib can be obtained).

Builds for both 32-bit 2.7 and 3.3/3.4 are available.
PyCharm detected them straight away, of course.

How do I get the current timezone name in Postgres 9.3?

This may or may not help you address your problem, OP, but to get the timezone of the current server relative to UTC (UT1, technically), do:


The above works by extracting the UT1-relative offset in minutes, and then converting it to hours using the factor of 3600 secs/hour.


SET SESSION timezone TO 'Asia/Kabul';
-- output: 4.5 (as of the writing of this post)


How to configure Docker port mapping to use Nginx as an upstream proxy?

Using docker links, you can link the upstream container to the nginx container. An added feature is that docker manages the host file, which means you'll be able to refer to the linked container using a name rather than the potentially random ip.

Understanding passport serialize deserialize

  1. Where does go after passport.serializeUser has been called?

The user id (you provide as the second argument of the done function) is saved in the session and is later used to retrieve the whole object via the deserializeUser function.

serializeUser determines which data of the user object should be stored in the session. The result of the serializeUser method is attached to the session as req.session.passport.user = {}. Here for instance, it would be (as we provide the user id as the key) req.session.passport.user = {id: 'xyz'}

  1. We are calling passport.deserializeUser right after it where does it fit in the workflow?

The first argument of deserializeUser corresponds to the key of the user object that was given to the done function (see 1.). So your whole object is retrieved with help of that key. That key here is the user id (key can be any key of the user object i.e. name,email etc). In deserializeUser that key is matched with the in memory array / database or any data resource.

The fetched object is attached to the request object as req.user

Visual Flow

passport.serializeUser(function(user, done) {
});              ¦
                 +--------------------? saved to session
                                   ¦    req.session.passport.user = {id: '..'}
passport.deserializeUser(function(id, done) {
    User.findById(id, function(err, user) {
        done(err, user);
    });            +--------------? user object attaches to the request as req.user   

Am I trying to connect to a TLS-enabled daemon without TLS?

I was getting the same error on MacOS with sudo and without it.

I have solved it with:

boot2docker start
$(boot2docker shellinit)

P.S.: Thanks to Alan. I found out that this approach is recommended in their official documentation.

P.S.2: Sometimes boot2docker init can be required before running two commands (thank you Aaron).

You cannot call a method on a null-valued expression

The simple answer for this one is that you have an undeclared (null) variable. In this case it is $md5. From the comment you put this needed to be declared elsewhere in your code

$md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider

The error was because you are trying to execute a method that does not exist.

PS C:\Users\Matt> $md5 | gm

   TypeName: System.Security.Cryptography.MD5CryptoServiceProvider

Name                       MemberType Definition                                                                                                                            
----                       ---------- ----------                                                                                                                            
Clear                      Method     void Clear()                                                                                                                          
ComputeHash                Method     byte[] ComputeHash(System.IO.Stream inputStream), byte[] ComputeHash(byte[] buffer), byte[] ComputeHash(byte[] buffer, int offset, ...

The .ComputeHash() of $md5.ComputeHash() was the null valued expression. Typing in gibberish would create the same effect.

PS C:\Users\Matt> $bagel.MakeMeABagel()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $bagel.MakeMeABagel()
+ ~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

PowerShell by default allows this to happen as defined its StrictMode

When Set-StrictMode is off, uninitialized variables (Version 1) are assumed to have a value of 0 (zero) or $Null, depending on type. References to non-existent properties return $Null, and the results of function syntax that is not valid vary with the error. Unnamed variables are not permitted.

Adjust icon size of Floating action button (fab)

off of @IRadha's answer in vector drawable setting android:height="_dp" and setting the scale type to android:scaleType="center" sets the drawable to whatever size was set

Get last 30 day records from today date in SQL Server

This Should Work Fine

SELECT * FROM product 
WHERE pdate BETWEEN datetime('now', '-30 days') AND datetime('now', 'localtime')

How do I make WRAP_CONTENT work on a RecyclerView

This now works as they've made a release in version 23.2, as stated in this post. Quoting the official blogpost

This release brings an exciting new feature to the LayoutManager API: auto-measurement! This allows a RecyclerView to size itself based on the size of its contents. This means that previously unavailable scenarios, such as using WRAP_CONTENT for a dimension of the RecyclerView, are now possible. You’ll find all built in LayoutManagers now support auto-measurement.

Getting the difference between two Dates (months/days/hours/minutes/seconds) in Swift

Slightly modified code for Swift 3.0

let calendar = NSCalendar.current as NSCalendar

// Replace the hour (time) of both dates with 00:00
let date1 = calendar.startOfDay(for: startDateTime)
let date2 = calendar.startOfDay(for: endDateTime)

let flags =
let components = calendar.components(flags, from: date1, to: date2, options: [])


Why am I getting a " Traceback (most recent call last):" error?

At the beginning of your file you set raw_input to 0. Do not do this, at it modifies the built-in raw_input() function. Therefore, whenever you call raw_input(), it is essentially calling 0(), which raises the error. To remove the error, remove the first line of your code:

M = 1.6
# Miles to Kilometers 
# Celsius Celsius = (var1 - 32) * 5/9
# Gallons to liters Gallons = 3.6
# Pounds to kilograms Pounds = 0.45
# Inches to centimete Inches = 2.54

def intro():
    print("Welcome! This program will convert measures for you.")

def main():
    print("Select operation.")
    print("1.Miles to Kilometers")
    print("2.Fahrenheit to Celsius")
    print("3.Gallons to liters")
    print("4.Pounds to kilograms")
    print("5.Inches to centimeters")

    choice = input("Enter your choice by number: ")

    if choice == '1':

    elif choice == '2':

    elif choice == '3':

    elif choice == '4':

    elif choice == '5':


def convertMK():
    input_M = float(raw_input(("Miles: ")))
    M_conv = (M) * input_M
    print("Kilometers: %f\n" % M_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print("I didn't quite understand that answer. Terminating.")

def converCF():
    input_F = float(raw_input(("Fahrenheit: ")))
    F_conv = (input_F - 32) * 5/9
    print("Celcius: %f\n") % F_conv
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print("I didn't quite understand that answer. Terminating.")

def convertGL():
    input_G = float(raw_input(("Gallons: ")))
    G_conv = input_G * 3.6
    print("Centimeters: %f\n" % G_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print ("I didn't quite understand that answer. Terminating.")

def convertPK():
    input_P = float(raw_input(("Pounds: ")))
    P_conv = input_P * 0.45
    print("Centimeters: %f\n" % P_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print ("I didn't quite understand that answer. Terminating.")

def convertIC():
    input_cm = float(raw_input(("Inches: ")))
    inches_conv = input_cm * 2.54
    print("Centimeters: %f\n" % inches_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print ("I didn't quite understand that answer. Terminating.")

def end():
    print("This program will close.")


Unable to add window -- token null is not valid; is your activity running?

In my case, I was inflating a PopupMenu at the very beginning of the activity i.e on onCreate()... I fixed it by putting it in a Handler

  new Handler().postDelayed(new Runnable() {
            public void run() {
                PopupMenu popuMenu=new PopupMenu(SplashScreen.this,binding.progressBar);

RecyclerView inside ScrollView is not working

**Solution which worked for me
Use NestedScrollView with height as wrap_content

<br> RecyclerView 
                tools:targetApi="lollipop"<br><br> and view holder layout 
 <br> android:layout_width="match_parent"<br>

//Your row content goes here

socket connect() vs bind()

To make understanding better , lets find out where exactly bind and connect comes into picture,

Further to positioning of two calls , as clarified by Sourav,

bind() associates the socket with its local address [that's why server side binds, so that clients can use that address to connect to server.] connect() is used to connect to a remote [server] address, that's why is client side, connect [read as: connect to server] is used.

We cannot use them interchangeably (even when we have client/server on same machine) because of specific roles and corresponding implementation.

I will further recommend to correlate these calls TCP/IP handshake .

enter image description here

So , who will send SYN here , it will be connect() . While bind() is used for defining the communication end point.

Hope this helps!!

What steps are needed to stream RTSP from FFmpeg?

You can use FFserver to stream a video using RTSP.

Just change console syntax to something like this:

ffmpeg -i space.mp4 -vcodec libx264 -tune zerolatency -crf 18 http://localhost:1234/feed1.ffm

Create a ffserver.config file (sample) where you declare HTTPPort, RTSPPort and SDP stream. Your config file could look like this (some important stuff might be missing):

HTTPPort 1234
RTSPPort 1235

<Feed feed1.ffm>
        File /tmp/feed1.ffm
        FileMaxSize 2M
        ACL allow

<Stream test1.sdp>
    Feed feed1.ffm
    Format rtp
    VideoCodec libx264
    AVOptionVideo flags +global_header
    AVOptionVideo me_range 16
    AVOptionVideo qdiff 4
    AVOptionVideo qmin 10
    AVOptionVideo qmax 51
    ACL allow

With such setup you can watch the stream with i.e. VLC by typing:


Here is the FFserver documentation.

Purpose of installing Twitter Bootstrap through npm?

  1. Use npm/bower to install bootstrap if you want to recompile it/change less files/test. With grunt it would be easier to do this, as shown on If you only want to add precompiled libraries feel free to manually include files to project.

  2. No, you have to do this by yourself or use separate grunt tool. For example 'grunt-contrib-concat' How to concatenate and minify multiple CSS and JavaScript files with Grunt.js (0.3.x)

What's the difference between Apache's Mesos and Google's Kubernetes

Both projects aim to make it easier to deploy & manage applications inside containers in your datacenter or cloud.

In order to deploy applications on top of Mesos, one can use Marathon or Kubernetes for Mesos.

Marathon is a cluster-wide init and control system for running Linux services in cgroups and Docker containers. Marathon has a number of different canary deploy features and is a very mature project.

Marathon runs on top of Mesos, which is a highly scalable, battle tested and flexible resource manager. Marathon is proven to scale and runs in many production environments.

The Mesos and Mesosphere technology stack provides a cloud-like environment for running existing Linux workloads, but it also provides a native environment for building new distributed systems.

Mesos is a distributed systems kernel, with a full API for programming directly against the datacenter. It abstracts underlying hardware (e.g. bare metal or VMs) away and just exposes the resources. It contains primitives for writing distributed applications (e.g. Spark was originally a Mesos App, Chronos, etc.) such as Message Passing, Task Execution, etc. Thus, entirely new applications are made possible. Apache Spark is one example for a new (in Mesos jargon called) framework that was built originally for Mesos. This enabled really fast development - the developers of Spark didn't have to worry about networking to distribute tasks amongst nodes as this is a core primitive in Mesos.

To my knowledge, Kubernetes is not used inside Google in production deployments today. For production, Google uses Omega/Borg, which is much more similar to the Mesos/Marathon model. However the great thing about using Mesos as the foundation is that both Kubernetes and Marathon can run on top of it.

More resources about Marathon:


Fade In on Scroll Down, Fade Out on Scroll Up - based on element position in window

I know it's late, but I take the original code and change some stuff to control easily the css. So I made a code with the addClass() and the removeClass()

Here the full code :

        if( bottom_of_window > bottom_of_object ){
        if( bottom_of_window < bottom_of_object ){

How to solve Notice: Undefined index: id in C:\xampp\htdocs\invmgt\manufactured_goods\change.php on line 21

if you are getting id from url try

$id = (isset($_GET['id']) ? $_GET['id'] : '');

if getting from form you need to use POST method cause your form has method="post"

 $id = (isset($_POST['id']) ? $_POST['id'] : '');

For php notices use isset() or empty() to check values exist or not or initialize variable first with blank or a value

$id= '';

Warning: mysqli_select_db() expects exactly 2 parameters, 1 given in C:\

mysqli_select_db() should have 2 parameters, the connection link and the database name -

mysqli_select_db($con, 'phpcadet') or die(mysqli_error($con));

Using mysqli_error in the die statement will tell you exactly what is wrong as opposed to a generic error message.

How to add elements to a list in R (loop)

You should not add to your list using c inside the loop, because that can result in very very slow code. Basically when you do c(l, new_element), the whole contents of the list are copied. Instead of that, you need to access the elements of the list by index. If you know how long your list is going to be, it's best to initialise it to this size using l <- vector("list", N). If you don't you can initialise it to have length equal to some large number (e.g if you have an upper bound on the number of iterations) and then just pick the non-NULL elements after the loop has finished. Anyway, the basic point is that you should have an index to keep track of the list element and add using that eg

i <- 1
while(...) {
    l[[i]] <- new_element
    i <- i + 1

For more info have a look at Patrick Burns' The R Inferno (Chapter 2).

How to use goto statement correctly

If you look up continue and break they accept a "Label". Experiment with that. Goto itself won't work.

public class BreakContinueWithLabel {

    public static void main(String args[]) {

        int[] numbers= new int[]{100,18,21,30};

        //Outer loop checks if number is multiple of 2
        OUTER:  //outer label
        for(int i = 0; i<numbers.length; i++){
            if(i % 2 == 0){
                System.out.println("Odd number: " + i +
                                   ", continue from OUTER label");
                continue OUTER;

            for(int j = 0; j<numbers.length; j++){
                System.out.println("Even number: " + i +
                                   ", break  from INNER label");
                break INNER;

Read more

resize2fs: Bad magic number in super-block while trying to open

I ran into the same exact problem around noon today and finally found a solution here --> Trying to resize2fs EB volume fails

I skipped mounting, since the partition was already mounted.

Apparently CentOS 7 uses XFS as the default file system and as a result resize2fs will fail.

I took a look in /etc/fstab, and guess what, XFS was staring me in the face... Hope this helps.

Subtracting time.Duration from time in Go

There's time.ParseDuration which will happily accept negative durations, as per manual. Otherwise put, there's no need to negate a duration where you can get an exact duration in the first place.

E.g. when you need to substract an hour and a half, you can do that like so:

package main

import (

func main() {
    now := time.Now()

    fmt.Println("now:", now)

    duration, _ := time.ParseDuration("-1.5h")

    then := now.Add(duration)

    fmt.Println("then:", then)

Global constants file in Swift


import Foundation

let kBaseURL = NSURL(string: "")


var manager = AFHTTPRequestOperationManager(baseURL: kBaseURL)

Cannot read property 'addEventListener' of null

Thanks from all, Load the Scripts in specific pages that you use, not for all pages, sometimes using swiper.js or other library it may cause this error message, the only way to solve this issue it to load the JS library on specific pages that ID is exist and prevent loading of the same library in all pages.

Hope this help you.

Using "-Filter" with a variable

You don't need quotes around the variable, so simply change this:

Get-ADComputer -Filter {name -like '$nameregex' -and Enabled -eq "true"}

into this:

Get-ADComputer -Filter {name -like $nameregex -and Enabled -eq "true"}

Note, however, that the scriptblock notation for filter statements is misleading, because the statement is actually a string, so it's better to write it as such:

Get-ADComputer -Filter "name -like '$nameregex' -and Enabled -eq 'true'"

Related. Also related.

And FTR: you're using wildcard matching here (operator -like), not regular expressions (operator -match).

Java: convert seconds to minutes, hours and days

The simpliest way

    Scanner in = new Scanner(;
    System.out.println("Enter seconds");
    int s = in.nextInt();

    int sec = s % 60;
    int min = (s / 60)%60;
    int hours = (s/60)/60;

    System.out.println(hours + ":" + min + ":" + sec);

Error:java: invalid source release: 8 in Intellij. What does it mean?

As Andreas mentioned all about:

Error:java: invalid source release: 8 in IntelliJ
Error:java: invalid source release: 13 in IntelliJ
Error:java: invalid source release: 14 in IntelliJ...

OR whatever version you are using in Java...

The problem will exist if you do not have it matching inside the below code:


This 1.8 in my case, must be matching on your device through MAVEN project library, settings, preferences, project setting and SDK.

Slick.js: Get current and total slides (ie. 3/5)

Modifications are done to the new Slick version 1.7.1.

Here is a updated script example: jsfiddle

What is the OAuth 2.0 Bearer Token exactly?

A bearer token is like a currency note e.g 100$ bill . One can use the currency note without being asked any/many questions.

Bearer Token A security token with the property that any party in possession of the token (a "bearer") can use the token in any way that any other party in possession of it can. Using a bearer token does not require a bearer to prove possession of cryptographic key material (proof-of-possession).

JSON ValueError: Expecting property name: line 1 column 2 (char 1)

  1. replace all single quotes with double quotes
  2. replace 'u"' from your strings to '"' ... so basically convert internal unicodes to strings before loading the string into json
>> strs = "{u'key':u'val'}"
>> strs = strs.replace("'",'"')
>> json.loads(strs.replace('u"','"'))

Warning: mysqli_real_escape_string() expects exactly 2 parameters, 1 given... what I do wrong?

use mysql_real_escape_string() instead of mysqli_real_escape_string()

like so:

$username = mysql_real_escape_string($_POST['username']);

WinSCP: Permission denied. Error code: 3 Error message from server: Permission denied

You possibly do not have create permissions to the folder. So WinSCP fails to create a temporary file for the transfer.

You have two options:

Dynamically add item to jQuery Select2 control that uses AJAX

$("#my_select").select2('destroy').empty().select2({data: [{id: 1, text: "new_item"}]});

Understanding PrimeFaces process/update and JSF f:ajax execute/render attributes

By process (in the JSF specification it's called execute) you tell JSF to limit the processing to component that are specified every thing else is just ignored.

update indicates which element will be updated when the server respond back to you request.

@all : Every component is processed/rendered.

@this: The requesting component with the execute attribute is processed/rendered.

@form : The form that contains the requesting component is processed/rendered.

@parent: The parent that contains the requesting component is processed/rendered.

With Primefaces you can even use JQuery selectors, check out this blog:

Intel's HAXM equivalent for AMD on Windows OS

Buying a new processor is one solution, but for some of us that means buying other components as well. Alternatively you could just buy an Android phone that supports your lowest target API level and run your apps off the phone. You can find some of those phones on Amazon, Ebay, craigslist for pennies (sometimes). Plus this grants you the benefit of actually running on the minimum hardware you intend to support. While this may be a bit slower than installing your app on an emulated system, it will probably save you money.

Android, device testing/debugging link:

Difference between Width:100% and width:100vw?

You can solve this issue be adding max-width:

#element {
   width: 100vw;
   height: 100vw;
   max-width: 100%;

When you using CSS to make the wrapper full width using the code width: 100vw; then you will notice a horizontal scroll in the page, and that happened because the padding and margin of html and body tags added to the wrapper size, so the solution is to add max-width: 100%

async await return Task

You need to use the await keyword when use async and your function return type should be generic Here is an example with return value:

public async Task<object> MethodName()
    return await Task.FromResult<object>(null);

Here is an example with no return value:

public async Task MethodName()
    await Task.CompletedTask;

Read these:

TPL: and Tasks:

Async: Await:

Using GPU from a docker container?

Recent enhancements by NVIDIA have produced a much more robust way to do this.

Essentially they have found a way to avoid the need to install the CUDA/GPU driver inside the containers and have it match the host kernel module.

Instead, drivers are on the host and the containers don't need them. It requires a modified docker-cli right now.

This is great, because now containers are much more portable.

enter image description here

A quick test on Ubuntu:

# Install nvidia-docker and nvidia-docker-plugin
wget -P /tmp
sudo dpkg -i /tmp/nvidia-docker*.deb && rm /tmp/nvidia-docker*.deb

# Test nvidia-smi
nvidia-docker run --rm nvidia/cuda nvidia-smi

For more details see: GPU-Enabled Docker Container and:

Oracle query to identify columns having special characters

They key is the backslash escape character will not work with the right square bracket inside of the character class square brackets (it is interpreted as a literal backslash inside the character class square brackets). Add the right square bracket with an OR at the end like this:

select EmpNo, SampleText
from test 
where NOT regexp_like(SampleText, '[ A-Za-z0-9.{}[]|]');

How to create JNDI context in Spring Boot with Embedded Tomcat Container

In SpringBoot 2.1, I found another solution. Extend standard factory class method getTomcatWebServer. And then return it as a bean from anywhere.

public class CustomTomcatServletWebServerFactory extends TomcatServletWebServerFactory {

    protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {
        System.setProperty("catalina.useNaming", "true");
        return new TomcatWebServer(tomcat, getPort() >= 0);

public class TomcatConfiguration {
    public ConfigurableServletWebServerFactory webServerFactory() {
        TomcatServletWebServerFactory factory = new CustomTomcatServletWebServerFactory();

        return factory;

Loading resources from context.xml doesn't work though. Will try to find out.

iOS 8 removed "minimal-ui" viewport property, are there other "soft fullscreen" solutions?

The root problem here seems that iOS8 safari won't hide the address bar when scrolling down if the content is equal or less than the viewport.

As you found out already, adding some padding at the bottom gets around this issue:

html {
    /* enough space to scroll up to get fullscreen on iOS8 */
    padding-bottom: 80px;
// sort of emulate safari's "bounce back to top" scroll
window.addEventListener('scroll', function(ev) {
    // avoids scrolling when the focused element is e.g. an input
    if (
        || document.activeElement === document.body
    ) {

The above css should be conditionally applied, for example with UA sniffing adding a gt-ios8 class to <html>.

Comparing two maps

As long as you override equals() on each key and value contained in the map, then m1.equals(m2) should be reliable to check for maps equality.

The same result can be obtained also by comparing toString() of each map as you suggested, but using equals() is a more intuitive approach.

May not be your specific situation, but if you store arrays in the map, may be a little tricky, because they must be compared value by value, or using Arrays.equals(). More details about this see here.

When is the init() function run?

A few more tips:

  • There can only be 1 main() function, but there can be many init() functions.
  • You do not need to explicitly call init() or main(), they are called automatically.
  • init() and main() do not accept any parameters and also don't return anything.
  • init() runs before main().
  • If you have many init(), they run in the order they are declared.

Failed to load ApplicationContext from Unit Test: FileNotFound

I added the spring folder to the build path and, after clean&build, it worked.

Why is it that "No HTTP resource was found that matches the request URI" here?

WebApiConfig.Register(GlobalConfiguration.Configuration); should be on top.

Open firewall port on CentOS 7

Hello in Centos 7 firewall-cmd. Yes correct if you use firewall-cmd --zone=public --add-port=2888/tcp but if you reload firewal firewall-cmd --reload

your config not will be save

you need to add key

firewall-cmd --permanent --zone=public --add-port=2888/tcp

What exactly does the Access-Control-Allow-Credentials header do?

By default, CORS does not include cookies on cross-origin requests. This is different from other cross-origin techniques such as JSON-P. JSON-P always includes cookies with the request, and this behavior can lead to a class of vulnerabilities called cross-site request forgery, or CSRF.

In order to reduce the chance of CSRF vulnerabilities in CORS, CORS requires both the server and the client to acknowledge that it is ok to include cookies on requests. Doing this makes cookies an active decision, rather than something that happens passively without any control.

The client code must set the withCredentials property on the XMLHttpRequest to true in order to give permission.

However, this header alone is not enough. The server must respond with the Access-Control-Allow-Credentials header. Responding with this header to true means that the server allows cookies (or other user credentials) to be included on cross-origin requests.

You also need to make sure your browser isn't blocking third-party cookies if you want cross-origin credentialed requests to work.

Note that regardless of whether you are making same-origin or cross-origin requests, you need to protect your site from CSRF (especially if your request includes cookies).

Changing navigation title programmatically

Swift 5.1

// Set NavigationBar Title Programmatically and Dynamic

Note : First add NavigationControllerItem to Your ViewController then goto their ViewController.swift file and Just Copy and Paste this in viewDidLoad().

navigationItem.title = "Your Title Here"

How to create JSON string in JavaScript?

This can be pretty easy and simple

var obj = new Object(); = "Raj";
obj.age = 32;
obj.married = false;

//convert object to json string
var string = JSON.stringify(obj);

//convert string to Json Object
console.log(JSON.parse(string)); // this is your requirement.

How to discard local commits in Git?

I had to do a :

git checkout -b master

as git said that it doesn't exists, because it's been wipe with the

git -D master

How to plot a 2D FFT in Matlab?

Assuming that I is your input image and F is its Fourier Transform (i.e. F = fft2(I))

You can use this code:

F = fftshift(F); % Center FFT

F = abs(F); % Get the magnitude
F = log(F+1); % Use log, for perceptual scaling, and +1 since log(0) is undefined
F = mat2gray(F); % Use mat2gray to scale the image between 0 and 1

imshow(F,[]); % Display the result

Java equivalent to C# extension methods

Bit late to the party on this question, but in case anyone finds it useful I just created a subclass:

public class ArrayList2<T> extends ArrayList<T> 
    private static final long serialVersionUID = 1L;

    public T getLast()
        if (this.isEmpty())
            return null;
            return this.get(this.size() - 1);

Undefined function mysql_connect()

In php.ini file

change this




Check if a string has a certain piece of text

Here you go: ES5

var test = 'Hello World';
if( test.indexOf('World') >= 0){
  // Found world

With ES6 best way would be to use includes function to test if the string contains the looking work.

const test = 'Hello World';
if (test.includes('World')) { 
  // Found world

Laravel - Model Class not found

As @bulk said, it uses namespaces.

I recommend you to start using an IDE, it will suggest you to import all the required namespaces (\App\Post in this case).

What are best practices that you use when writing Objective-C and Cocoa?


Instead of:

@interface MyClass (private)
- (void) someMethod
- (void) someOtherMethod


@interface MyClass ()
- (void) someMethod
- (void) someOtherMethod

New in Objective-C 2.0.

Class extensions are described in Apple's Objective-C 2.0 Reference.

"Class extensions allow you to declare additional required API for a class in locations other than within the primary class @interface block"

So they're part of the actual class - and NOT a (private) category in addition to the class. Subtle but important difference.

'module' object is not callable - calling method in another file

  • from a directory_of_modules, you can import a
  • this, can contain a Class with some_methods() or just functions()
  • from a, you can instantiate a Class or call functions()
  • from this Class, you can execute some_method()


from directory_of_modules import specific_module
instance = specific_module.DbConnect("username","password")

Excerpts from PEP 8 - Style Guide for Python Code:

Modules should have short and all-lowercase names.

Notice: Underscores can be used in the module name if it improves readability.

A Python module is simply a source file(*.py), which can expose:

  • Class: names using the "CapWords" convention.

  • Function: names in lowercase, words separated by underscores.

  • Global Variables: the conventions are about the same as those for Functions.

How to access form methods and controls from a class in C#?

  1. you have to have a reference to the form object in order to access its elements
  2. the elements have to be declared public in order for another class to access them
  3. don't do this - your class has to know too much about how your form is implemented; do not expose form controls outside of the form class
  4. instead, make public properties on your form to get/set the values you are interested in
  5. post more details of what you want and why, it sounds like you may be heading off in a direction that is not consistent with good encapsulation practices

@Html.DisplayFor - DateFormat ("mm/dd/yyyy")

This is the best way to get a simple date string :

 @DateTime.Parse(Html.DisplayFor(Model => Model.AuditDate).ToString()).ToShortDateString()

Make Font Awesome icons in a circle?

The below example didnt quite work for me,this is the version that i made work!


<div class="social-links">
    <a href="#"><i class="fa fa-facebook fa-lg"></i></a>
    <a href="#"><i class="fa fa-twitter fa-lg"></i></a>
    <a href="#"><i class="fa fa-google-plus fa-lg"></i></a>
    <a href="#"><i class="fa fa-pinterest fa-lg"></i></a>


.social-links {

.social-links a{
    display: inline-block;
    height: 50px;
    border: 2px solid #909090;
    border-radius: 50px;
    margin-right: 15px;

.social-links a i{
    padding: 18px 11px;
    font-size: 20px;
    color: #909090;

HTTP Status 500 - Servlet.init() for servlet Dispatcher threw exception

You map your dispatcher on *.do:


but your controller is mapped on an url without .do:


Try changing this to:


ProgressDialog is deprecated.What is the alternate one to use?

Maybe this guide could help you.

Usually I prefer to make custom AlertDialogs with indicators. It solves such problems like customization of the App view.

How does java do modulus calculations with negative numbers?

x = x + m = x - m in modulus m.
so -13 = -13 + 64 in modulus 64 and -13 = 51 in modulus 64.
assume Z = X * d + r, if 0 < r < X then in division Z/X we call r the remainder.
Z % X returns the remainder of Z/X.

java.lang.IllegalAccessError: tried to access method

Just an addition to the solved answer:

This COULD be a problem with Android Studio's Instant Run feature, for example, if you realized you forgot to add the line of code: finish() to your activity after opening another one, and you already re-opened the activity you shouldn't have reopened (which the finish() solved), then you add finish() and Instant Run occurs, then the app will crash since the logic has been broken.


This is not necessarily a code problem, just an Instant Run problem

Windows service on Local Computer started and then stopped error

If the service starts and stops like that, it means your code is throwing an unhandled exception. This is pretty difficult to debug, but there are a few options.

  1. Consult the Windows Event Viewer. Normally you can get to this by going to the computer/server manager, then clicking Event Viewer -> Windows Logs -> Application. You can see what threw the exception here, which may help, but you don't get the stack trace.
  2. Extract your program logic into a library class project. Now create two different versions of the program: a console app (for debugging), and the windows service. (This is a bit of initial effort, but saves a lot of angst in the long run.)
  3. Add more try/catch blocks and logging to the app to get a better picture of what's going on.

Preventing twitter bootstrap carousel from auto sliding on page load

if you're using bootstrap 3 set data-interval="false" on the HTML structure of carousel


<div id="carousel-example-generic" class="carousel slide" data-ride="carousel" data-interval="false">

How does Spring autowire by name when more than one matching bean is found?

This is documented in section 3.9.3 of the Spring 3.0 manual:

For a fallback match, the bean name is considered a default qualifier value.

In other words, the default behaviour is as though you'd added @Qualifier("country") to the setter method.

How do I read a string entered by the user in C?

You can use scanf function to read string


i don't know about other better options to receive string,

Cannot connect to SQL Server named instance from another SQL Server

To solve this you must ensure the following is true on the machine hosting SQL Server...

  1. Ensure Server Browser service is running
  2. Ensure TCP/IP communication is enabled for each instance you wish to communicate with over the network. enter image description here
  3. If running multiple instances, ensure each instance is using a different port, and that the port is not in use. e.g for two instance 1433 (default port for the default instance, 1435 for a named instance. enter image description here
  4. Ensure the firewall has an entry to allow communication with SQL Server browser on port 1434 over the UDP protocol.
  5. Ensure the firewall has an entry to allow communication with SQL Server instances on the ports assigned to them in step 3 over the TCP protocol enter image description here

How to check if a string is null in python

Try this:

if cookie and not cookie.isspace():
    # the string is non-empty
    # the string is empty

The above takes in consideration the cases where the string is None or a sequence of white spaces.

Regular expression to validate US phone numbers?

The easiest way to match both




is to use alternation ((...|...)): specify them as two mostly-separate options:


By the way, when Americans put the area code in parentheses, we actually put a space after that; for example, I'd write (123) 123-1234, not (123)123-1234. So you might want to write:

^(\([0-9]{3}\) |[0-9]{3}-)[0-9]{3}-[0-9]{4}$

(Though it's probably best to explicitly demonstrate the format that you expect phone numbers to be in.)

Ajax using https on an http page may resolve to a different VirtualHost than (which, as the Host header is not sent, responds to the default for that IP), so the two are treated as separate domains and thus subject to crossdomain JS restrictions.

JSON callbacks may let you avoid this.

ASP.NET DateTime Picker

If you would like to work with a textbox, be aware that setting the TextMode property to "Date" will not work on Internet Explorer 11, because it does not currently support the "Date", "DateTime", nor "Time" values.

This example illustrates how to implement it using a textbox, including validation of the dates (since the user could enter just numbers). It will work on Internet Explorer 11 as well other web browsers.

<asp:Content ID="Content"

<link rel="stylesheet"
    href="//" />
   <script src=""></script>
   $(function () {
   <%= txtBoxDate.ClientID %>").datepicker();
 <asp:TextBox ID="txtBoxDate"
 <asp:CompareValidator ID="CompareValidator1"
                    Type="Date">Date invalid, please check format. 

Compiling php with curl, where is curl installed?

For Ubuntu 17.0 +

Adding to @netcoder answer above, If you are using Ubuntu 17+, installing libcurl header files is half of the solution. The installation path in ubuntu 17.0+ is different than the installation path in older Ubuntu version. After installing libcurl, you will still get the "cURL not found" error. You need to perform one extra step (as suggested by @minhajul in the OP comment section).

Add a symlink in /usr/include of the cURL installation folder (cURL installation path in Ubuntu 17.0.4 is /usr/include/x86_64-linux-gnu/curl).

My server was running Ubuntu 17.0.4, the commands to enable cURL support were

sudo apt-get install libcurl4-gnutls-dev

Then create a link to cURL installation

cd /usr/include
sudo ln -s x86_64-linux-gnu/curl

How to use orderby with 2 fields in linq?

If you have two or more field to order try this:

var soterdList = initialList.OrderBy(x => x.Priority).
                                    ThenBy(x => x.ArrivalDate).
                                    ThenBy(x => x.ShipDate);

You can add other fields with clasole "ThenBy"

How to put an image next to each other

try putting both images next to each other. Like this:

    <div id="icons"><a href=""><img src="images/facebook.png"></a><a href=""><img src="images/twitter.png"></a>

Generating sql insert into for Oracle

If you have an empty table the Export method won't work. As a workaround. I used the Table View of Oracle SQL Developer. and clicked on Columns. Sorted by Nullable so NO was on top. And then selected these non nullable values using shift + select for the range.

This allowed me to do one base insert. So that Export could prepare a proper all columns insert.

Passing an array by reference

It is a syntax. In the function arguments int (&myArray)[100] parenthesis that enclose the &myArray are necessary. if you don't use them, you will be passing an array of references and that is because the subscript operator [] has higher precedence over the & operator.

E.g. int &myArray[100] // array of references

So, by using type construction () you tell the compiler that you want a reference to an array of 100 integers.

E.g int (&myArray)[100] // reference of an array of 100 ints

First Heroku deploy failed `error code=H10`

In my case I had code=H10 and status=503 because my Procfile:

web: node build/server.js

and I included /build in .gitignore

Get exception description and stack trace which caused an exception, all as a string

Let's create a decently complicated stacktrace, in order to demonstrate that we get the full stacktrace:

def raise_error():
    raise RuntimeError('something bad happened!')

def do_something_that_might_error():

Logging the full stacktrace

A best practice is to have a logger set up for your module. It will know the name of the module and be able to change levels (among other attributes, such as handlers)

import logging
logger = logging.getLogger(__name__)

And we can use this logger to get the error:

except Exception as error:

Which logs:

ERROR:__main__:something bad happened!
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in do_something_that_might_error
  File "<stdin>", line 2, in raise_error
RuntimeError: something bad happened!

And so we get the same output as when we have an error:

>>> do_something_that_might_error()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in do_something_that_might_error
  File "<stdin>", line 2, in raise_error
RuntimeError: something bad happened!

Getting just the string

If you really just want the string, use the traceback.format_exc function instead, demonstrating logging the string here:

import traceback
except Exception as error:
    just_the_string = traceback.format_exc()

Which logs:

DEBUG:__main__:Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in do_something_that_might_error
  File "<stdin>", line 2, in raise_error
RuntimeError: something bad happened!

How does "304 Not Modified" work exactly?

Last-Modified : The last modified date for the requested object

If-Modified-Since : Allows a 304 Not Modified to be returned if last modified date is unchanged.

ETag : An ETag is an opaque identifier assigned by a web server to a specific version of a resource found at a URL. If the resource representation at that URL ever changes, a new and different ETag is assigned.

If-None-Match : Allows a 304 Not Modified to be returned if ETag is unchanged.

the browser store cache with a date(Last-Modified) or id(ETag), when you need to request the URL again, the browser send request message with the header:

enter image description here

the server will return 304 when the if statement is False, and browser will use cache.

Creating a new column based on if-elif-else condition

enter image description here

Lets say above one is your original dataframe and you want to add a new column 'old'

If age greater than 50 then we consider as older=yes otherwise False

step 1: Get the indexes of rows whose age greater than 50


step 2: Using .loc we can assign a new value to column


same for age below less than 50



JavaScriptSerializer - JSON serialization of enum as string

This is easily done by adding a ScriptIgnore attribute to the Gender property, causing it to not be serialised, and adding a GenderString property which does get serialised:

class Person
    int Age { get; set; }

    Gender Gender { get; set; }

    string GenderString { get { return Gender.ToString(); } }

Visibility of global variables in imported modules

This post is just an observation for Python behaviour I encountered. Maybe the advices you read above don't work for you if you made the same thing I did below.

Namely, I have a module which contains global/shared variables (as suggested above):


Then I had the main module which imports the shared stuff with:

import sharedstuff as shared

and some other modules that actually populated these arrays. These are called by the main module. When exiting these other modules I can clearly see that the arrays are populated. But when reading them back in the main module, they were empty. This was rather strange for me (well, I am new to Python). However, when I change the way I import the in the main module to:

from globals import *

it worked (the arrays were populated).

Just sayin'

Append text with .bat

Any line starting with a "REM" is treated as a comment, nothing is executed including the redirection.

Also, the %date% variable may contain "/" characters which are treated as path separator characters, leading to the system being unable to create the desired log file.

How to execute a stored procedure within C# program

using (var conn = new SqlConnection(connectionString))
using (var command = new SqlCommand("ProcedureName", conn) { 
                           CommandType = CommandType.StoredProcedure }) {

How to use npm with node.exe?

I just installed Node.js for the first time and it includes NPM, which can be ran from the Windows cmd. However, make sure that you run it as an administrator. Right click on cmd and choose "run as administrator". This allowed me to call npm commands.

How to end C++ code

If your if statement is in Loop You can use


If you want to escape some code & continue to loop Use :


If your if statement not in Loop You can use :

 return 0;



Using Selenium Web Driver to retrieve value of a HTML input

You can do like this :

webelement time=driver.findElement("input_name")).getAttribute("value");

this will give you the time displaying on the webpage.

Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

The basic difference between all these annotations is as follows -

  1. @BeforeEach - Use to run a common code before( eg setUp) each test method execution. analogous to JUnit 4’s @Before.
  2. @AfterEach - Use to run a common code after( eg tearDown) each test method execution. analogous to JUnit 4’s @After.
  3. @BeforeAll - Use to run once per class before any test execution. analogous to JUnit 4’s @BeforeClass.
  4. @AfterAll - Use to run once per class after all test are executed. analogous to JUnit 4’s @AfterClass.

All these annotations along with the usage is defined on Codingeek - Junit5 Test Lifecycle

TLS 1.2 not working in cURL

TLS 1.1 and TLS 1.2 are supported since OpenSSL 1.0.1

Forcing TLS 1.1 and 1.2 are only supported since curl 7.34.0

You should consider an upgrade.

Links in <select> dropdown options

Maybe this will help:

<select onchange="location = this.value;">
 <option value="home.html">Home</option>
 <option value="contact.html">Contact</option>
 <option value="about.html">About</option>

PHP - Session destroy after closing browser

The best way is to close the session is: if there is no response for that session after particular interval of time. then close. Please see this post and I hope it will resolve the issue. "How to change the session timeout in PHP?"

Get the Year/Month/Day from a datetime in php?

Try below code if you want to use php loop to display

  <select name="birth_month">
    <?php for( $m=1; $m<=12; ++$m ) { 
      $month_label = date('F', mktime(0, 0, 0, $m, 1));
      <option value="<?php echo $month_label; ?>"><?php echo $month_label; ?></option>
    <?php } ?>
  <select name="birth_day">
      $start_date = 1;
      $end_date   = 31;
      for( $j=$start_date; $j<=$end_date; $j++ ) {
        echo '<option value='.$j.'>'.$j.'</option>';
  <select name="birth_year">
      $year = date('Y');
      $min = $year - 60;
      $max = $year;
      for( $i=$max; $i>=$min; $i-- ) {
        echo '<option value='.$i.'>'.$i.'</option>';

MySQL Workbench: How to keep the connection alive

OK - so this issue has been driving me crazy - v 6.3.6 on Ubuntu Linux. None of the above solutions worked for me. Connecting to localhost mysql server previously always worked fine. Connecting to remote server always timed out - after about 60 seconds, sometimes after less time, sometimes more.

What finally worked for me was upgrading Workbench to 6.3.9 - no more dropped connections.

How to properly seed random number generator

If your aim is just to generate a sting of random number then I think it's unnecessary to complicate it with multiple function calls or resetting seed every time.

The most important step is to call seed function just once before actually running rand.Init(x). Seed uses the provided seed value to initialize the default Source to a deterministic state. So, It would be suggested to call it once before the actual function call to pseudo-random number generator.

Here is a sample code creating a string of random numbers

package main 
import (

func main(){

    var s string
    for i:=0;i<10;i++{
    s+=fmt.Sprintf("%d ",rand.Intn(7))

The reason I used Sprintf is because it allows simple string formatting.

Also, In rand.Intn(7) Intn returns, as an int, a non-negative pseudo-random number in [0,7).

Get filename and path from URI from mediastore

Any way for past Android Q, when MediaStore.Images.Media.DATA won't be available anymore? This field is depreciated in Android Q:

This constant was deprecated in API level 29. Apps may not have filesystem permissions to directly access this path. Instead of trying to open this path directly, apps should use ContentResolver#openFileDescriptor(Uri, String) to gain access.

--- Edited

As far as I know for past Android Q the only way is to relay on RELATIVE_PATH

Relative path of this media item within the storage device where it is persisted. For example, an item stored at /storage/0000-0000/DCIM/Vacation/IMG1024.JPG would have a path of DCIM/Vacation/.

How do I join two lists in Java?

Here is a java 8 solution using two lines:

List<Object> newList = new ArrayList<>();
Stream.of(list1, list2).forEach(newList::addAll);

Be aware that this method should not be used if

  • the origin of newList is not known and it may already be shared with other threads
  • the stream that modifies newList is a parallel stream and access to newList is not synchronized or threadsafe

due to side effect considerations.

Both of the above conditions do not apply for the above case of joining two lists, so this is safe.

Based on this answer to another question.

pip install fails with "connection error: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:598)"

First of all,

    pip install --trusted-host <package name>

did not work for me. I kept getting the CERTIFICATE_VERIFY_FAILED error. However, I noticed in the error messages that they referenced the '' site. So, I used this as the trusted host name instead of That almost got me there; the load was still failing with CERTIFICATE_VERIFY_FAILED, but at a later point. Finding the reference to the website that was failing, I included it as a trusted host. What eventually worked for me was:

    pip install --trusted-host --trusted-host <package name>

Format date in a specific timezone

As pointed out in Manto's answer, .utcOffset() is the preferred method as of Moment 2.9.0. This function uses the real offset from UTC, not the reverse offset (e.g., -240 for New York during DST). Offset strings like "+0400" work the same as before:

// always "2013-05-23 00:55"
moment(1369266934311).utcOffset(60).format('YYYY-MM-DD HH:mm')
moment(1369266934311).utcOffset('+0100').format('YYYY-MM-DD HH:mm')

The older .zone() as a setter was deprecated in Moment.js 2.9.0. It accepted a string containing a timezone identifier (e.g., "-0400" or "-04:00" for -4 hours) or a number representing minutes behind UTC (e.g., 240 for New York during DST).

// always "2013-05-23 00:55"
moment(1369266934311).zone(-60).format('YYYY-MM-DD HH:mm')
moment(1369266934311).zone('+0100').format('YYYY-MM-DD HH:mm')

To work with named timezones instead of numeric offsets, include Moment Timezone and use .tz() instead:

// determines the correct offset for America/Phoenix at the given moment
// always "2013-05-22 16:55"
moment(1369266934311).tz('America/Phoenix').format('YYYY-MM-DD HH:mm')

how to get bounding box for div element in jquery

using JQuery:

[myelement.offset().left, myelement.offset().top,  myelement.width(), myelement.height()]

Make A List Item Clickable (HTML/CSS)

The key is to give the anchor links a display property of "block" and a width property of 100%.

Making list-items clickable (example):


    <li><a href="">link1</a></li>
    <li><a href="">link2</a></li>
    <li><a href="">link3</a></li>


ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
ul li a {
  display: block;
  width: 100%;
  text-decoration: none;
  padding: 5px;
ul li a:hover {
  background-color: #ccc;

Install specific version using laravel installer

You can use composer method like

composer create-project laravel/laravel blog "5.1"

Or here is the composer file

    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": ">=5.5.9",
        "laravel/framework": "5.1.*"
    "require-dev": {
        "fzaninotto/faker": "~1.4",
        "mockery/mockery": "0.9.*",
        "phpunit/phpunit": "~4.0",
        "phpspec/phpspec": "~2.1"
    "autoload": {
        "classmap": [
        "psr-4": {
            "App\\": "app/"
    "autoload-dev": {
        "classmap": [
    "scripts": {
        "post-install-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        "pre-update-cmd": [
            "php artisan clear-compiled"
        "post-update-cmd": [
            "php artisan optimize"
        "post-root-package-install": [
            "php -r \"copy('.env.example', '.env');\""
        "post-create-project-cmd": [
            "php artisan key:generate"
    "config": {
        "preferred-install": "dist"

Hive cast string to date dd-MM-yyyy


from_unixtime(unix_timestamp('12-03-2010' , 'dd-MM-yyyy'))

How to Delete node_modules - Deep Nested Folder in Windows

I used GitBash to remove de folder!

rm -r node_modules

It took a while to delete everything, but worked for me!

what is the difference between const_iterator and iterator?

Performance wise there is no difference. The only purpose of having const_iterator over iterator is to manage the accessesibility of the container on which the respective iterator runs. You can understand it more clearly with an example:

std::vector<int> integers{ 3, 4, 56, 6, 778 };

If we were to read & write the members of a container we will use iterator:

for( std::vector<int>::iterator it = integers.begin() ; it != integers.end() ; ++it )
       {*it = 4;  std::cout << *it << std::endl; }

If we were to only read the members of the container integers you might wanna use const_iterator which doesn't allow to write or modify members of container.

for( std::vector<int>::const_iterator it = integers.begin() ; it != integers.end() ; ++it )
       { cout << *it << endl; }

NOTE: if you try to modify the content using *it in second case you will get an error because its read-only.

Equivalent of .bat in mac os

The common convention would be to put it in a .sh file that looks like this -

java -cp  ".;./supportlibraries/Framework_Core.jar;... etc

Note that '\' become '/'.

You could execute as


or set the x bit on the file

chmod +x

and then just call

Change Default branch in gitlab

In Gitlab CE 9.0, You can change the default branch from the Settings Tab in a repository's header.

How to upgrade all Python packages with pip

The following works on Windows and should be good for others too ($ is whatever directory you're in, in the command prompt. For example, C:/Users/Username).


$ pip freeze > requirements.txt

Open the text file, replace the == with >=, and execute:

$ pip install -r requirements.txt --upgrade

If you have a problem with a certain package stalling the upgrade (NumPy sometimes), just go to the directory ($), comment out the name (add a # before it) and run the upgrade again. You can later uncomment that section back. This is also great for copying Python global environments.

Another way:

I also like the pip-review method:

$ pip install pip-review

$ pip-review --local --interactive

$ pip3 install pip-review

$ py -3 -m pip_review --local --interactive

You can select 'a' to upgrade all packages; if one upgrade fails, run it again and it continues at the next one.

What's the easy way to auto create non existing dir in ansible

To ensure success with a full path use recurse=yes

- name: ensure custom facts directory exists
    file: >

How to set delay in android?

If you want to do something in the UI on regular time intervals very good option is to use CountDownTimer:

new CountDownTimer(30000, 1000) {

     public void onTick(long millisUntilFinished) {
         mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);

     public void onFinish() {

C# event with custom arguments

You need to declare a custom eventhandler.

public class MyEventArgs: EventArgs

public delegate void MyEventHandler(object sender, MyEventArgs e);

public class MyControl: UserControl
  public event MyEventHandler MyEvent;

Add (insert) a column between two columns in a data.frame

R has no functionality to specify where a new column is added. E.g., mtcars$mycol<-'foo'. It always is added as last column. Using other means (e.g., dplyr's select()) you can move the mycol to a desired position. This is not ideal and R may want to try to change that in the future.

Float and double datatype in Java

You should use double instead of float for precise calculations, and float instead of double when using less accurate calculations. Float contains only decimal numbers, but double contains an IEEE754 double-precision floating point number, making it easier to contain and computate numbers more accurately. Hope this helps.

Plot Normal distribution with Matplotlib

Assuming you're getting norm from scipy.stats, you probably just need to sort your list:

import numpy as np
import scipy.stats as stats
import matplotlib.pyplot as plt

h = [186, 176, 158, 180, 186, 168, 168, 164, 178, 170, 189, 195, 172,
     187, 180, 186, 185, 168, 179, 178, 183, 179, 170, 175, 186, 159,
     161, 178, 175, 185, 175, 162, 173, 172, 177, 175, 172, 177, 180]
hmean = np.mean(h)
hstd = np.std(h)
pdf = stats.norm.pdf(h, hmean, hstd)
plt.plot(h, pdf) # including h here is crucial

And so I get: enter image description here

Installing Java 7 on Ubuntu

Oracle Java 1.7.0 from .deb packages

chmod +x
sudo ./ -7
sudo apt-get update
sudo sudo apt-get install oracle-java7-jdk oracle-java7-fonts oracle-java7-source 
sudo apt-get dist-upgrade

Workaround for 1.7.0_51

There is an Issue 123 currently in OAB and a pull request

Here is the patched vesion:

chmod +x
sudo ./ -7
sudo apt-get update
sudo sudo apt-get install oracle-java7-jdk oracle-java7-fonts oracle-java7-source 
sudo apt-get dist-upgrade

How to send password securely over HTTP?

you can use ssl for your host there is free project for ssl like letsencrypt

Is there an alternative sleep function in C to milliseconds?

You can use this cross-platform function:

#ifdef WIN32
#include <windows.h>
#elif _POSIX_C_SOURCE >= 199309L
#include <time.h>   // for nanosleep
#include <unistd.h> // for usleep

void sleep_ms(int milliseconds){ // cross-platform sleep function
#ifdef WIN32
#elif _POSIX_C_SOURCE >= 199309L
    struct timespec ts;
    ts.tv_sec = milliseconds / 1000;
    ts.tv_nsec = (milliseconds % 1000) * 1000000;
    nanosleep(&ts, NULL);
    if (milliseconds >= 1000)
      sleep(milliseconds / 1000);
    usleep((milliseconds % 1000) * 1000);

Embed website into my site

You might want to check HTML frames, which can do pretty much exactly what you are looking for. They are considered outdated however.

CHECK constraint in MySQL is not working

CHECK constraints are ignored by MySQL as explained in a miniscule comment in the docs: CREATE TABLE

The CHECK clause is parsed but ignored by all storage engines.

What is the difference between typeof and instanceof and when should one be used vs. the other?

One more case is that You only can collate with instanceof - it returns true or false. With typeof you can get type of provided something

Python: finding an element in a list

assuming you want to find a value in a numpy array, I guess something like this might work:


recyclerview No adapter attached; skipping layout

Just put code inside onCreate() method

/* Like This*/

protected void onCreate(Bundle savedInstanceState) {

    recyclerView = (RecyclerView) findViewById(;
    layoutManager = new LinearLayoutManager(YourActivity.this);
    mAdapter = new YourAdapter(YourModelClassObject);

Convert Unix timestamp to a date string

The standard Perl solution is:

echo $TIMESTAMP | perl -nE 'say scalar gmtime $_'

(or localtime, if preferred)

Entity Framework. Delete all rows in table

Warning: The following is only suitable for small tables (think < 1000 rows)

Here is a solution that uses entity framework (not SQL) to delete the rows, so it is not SQL Engine(R/DBM) specific.

This assumes that you're doing this for testing or some similar situation. Either

  • The amount of data is small or
  • The performance doesn't matter

Simply call:


Assuming this context:

public class VotingContext : DbContext
    public DbSet<Vote> Votes{get;set;}
    public DbSet<Poll> Polls{get;set;}
    public DbSet<Voter> Voters{get;set;}
    public DbSet<Candidacy> Candidates{get;set;}

For tidier code you can declare the following extension method:

public static class EntityExtensions
    public static void Clear<T>(this DbSet<T> dbSet) where T : class

Then the above becomes:

await VotingTestContext.SaveChangesAsync();

I recently used this approach to clean up my test database for each testcase run (it´s obviously faster than recreating the DB from scratch each time, though I didn´t check the form of the delete commands that were generated).

Why can it be slow?

  1. EF will get ALL the rows (VotingContext.Votes)
  2. and then will use their IDs (not sure exactly how, doesn't matter), to delete them.

So if you're working with serious amount of data you'll kill the SQL server process (it will consume all the memory) and same thing for the IIS process since EF will cache all the data same way as SQL server. Don't use this one if your table contains serious amount of data.

T-SQL How to select only Second row from a table?

This is also useful:

  SELECT e1.*
    , row_number() OVER (ORDER BY e1.Rate DESC) AS _Rank
  HumanResources.EmployeePayHistory AS e1
) AS t
WHERE t._Rank = 2

How to split a data frame?

Splitting the data frame seems counter-productive. Instead, use the split-apply-combine paradigm, e.g., generate some data

df = data.frame(grp=sample(letters, 100, TRUE), x=rnorm(100))

then split only the relevant columns and apply the scale() function to x in each group, and combine the results (using split<- or ave)

df$z = 0
split(df$z, df$grp) = lapply(split(df$x, df$grp), scale)
## alternative: df$z = ave(df$x, df$grp, FUN=scale)

This will be very fast compared to splitting data.frames, and the result remains usable in downstream analysis without iteration. I think the dplyr syntax is

df %>% group_by(grp) %>% mutate(z=scale(x))

In general this dplyr solution is faster than splitting data frames but not as fast as split-apply-combine.

What's the difference between compiled and interpreted language?

Here is the Basic Difference between Compiler vs Interpreter Language.

Compiler Language

  • Takes entire program as single input and converts it into object code which is stored in the file.
  • Intermediate Object code is generated
  • e.g: C,C++
  • Compiled programs run faster because compilation is done before execution.
  • Memory requirement is more due to the creation of object code.
  • Error are displayed after the entire program is compiled
  • Source code ---Compiler ---Machine Code ---Output

Interpreter Language:

  • Takes single instruction as single input and executes instructions.
  • Intermediate Object code is NOT generated
  • e.g: Perl, Python, Matlab
  • Interpreted programs run slower because compilation and execution take place simultaneously.
  • Memory requirement is less.
  • Error are displayed for every single instruction.
  • Source Code ---Interpreter ---Output

Filter rows which contain a certain string

This answer similar to others, but using preferred stringr::str_detect and dplyr rownames_to_column.


mtcars %>% 
  rownames_to_column("type") %>% 
  filter(stringr::str_detect(type, 'Toyota|Mazda') )

#>             type  mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#> 1      Mazda RX4 21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
#> 2  Mazda RX4 Wag 21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
#> 3 Toyota Corolla 33.9   4  71.1  65 4.22 1.835 19.90  1  1    4    1
#> 4  Toyota Corona 21.5   4 120.1  97 3.70 2.465 20.01  1  0    3    1

Created on 2018-06-26 by the reprex package (v0.2.0).

LINQ Join with Multiple Conditions in On Clause

You can't do it like that. The join clause (and the Join() extension method) supports only equijoins. That's also the reason, why it uses equals and not ==. And even if you could do something like that, it wouldn't work, because join is an inner join, not outer join.

How to check if NSString begins with a certain character

NSString *stringWithoutAsterisk(NSString *string) {
    NSRange asterisk = [string rangeOfString:@"*"];
    return asterisk.location == 0 ? [string substringFromIndex:1] : string;

Convert StreamReader to byte[]

You can also use CopyTo:

var ms = new MemoryStream();
yourStreamReader.BaseStream.CopyTo(ms); // blocking call till the end of the stream
ms.GetBuffer().CopyTo(yourArray, ms.Length);


var ms = new MemoryStream();
var ct = yourStreamReader.BaseStream.CopyToAsync(ms);
await ct;
ms.GetBuffer().CopyTo(yourArray, ms.Length);

How do I iterate over a range of numbers defined by variables in Bash?

These are all nice but seq is supposedly deprecated and most only work with numeric ranges.

If you enclose your for loop in double quotes, the start and end variables will be dereferenced when you echo the string, and you can ship the string right back to BASH for execution. $i needs to be escaped with \'s so it is NOT evaluated before being sent to the subshell.

echo -e "for i in {$RANGE_START..$RANGE_END}; do echo \\${i}; done" | bash

This output can also be assigned to a variable:

VAR=`echo -e "for i in {$RANGE_START..$RANGE_END}; do echo \\${i}; done" | bash`

The only "overhead" this should generate should be the second instance of bash so it should be suitable for intensive operations.

how does unix handle full path name with space and arguments?

I would also like to point out that in case you are using command line arguments as part of a shell script (.sh file), then within the script, you would need to enclose the argument in quotes. So if your command looks like

> arg1 arg2

And arg1 is your path that has spaces, then within the shell script, you would need to refer to it as "$arg1" instead of $arg1

Here are the details

Passing an Object from an Activity to a Fragment

If the data should survive throughout the application lifecycle and shared among multiple fragments or activities, a Model class might come into consideration, which has got less serialization overhead.

Check this design example

HtmlSpecialChars equivalent in Javascript?

Hope this wins the race due to its performance and most important not a chained logic using .replace('&','&').replace('<','<')...

var mapObj = {
var re = new RegExp(Object.keys(mapObj).join("|"),"gi");

function escapeHtml(str) 
    return str.replace(re, function(matched)
        return mapObj[matched.toLowerCase()];

console.log('<script type="text/javascript">alert('Hello World');</script>');
console.log(escapeHtml('<script type="text/javascript">alert('Hello World');</script>'));

javascript how to create a validation error message without using alert

I would strongly suggest you start using jQuery. Your code would look like:

$(function() {
    $('form[name="myform"]').submit(function(e) {
        var username = $('form[name="myform"] input[name="username"]').val();
        if ( username == '') {
            $('#errors').text('*Please enter a username*');

Write to CSV file and export it?

Rom, you're doing it wrong. You don't want to write files to disk so that IIS can serve them up. That adds security implications as well as increases complexity. All you really need to do is save the CSV directly to the response stream.

Here's the scenario: User wishes to download csv. User submits a form with details about the csv they want. You prepare the csv, then provide the user a URL to an aspx page which can be used to construct the csv file and write it to the response stream. The user clicks the link. The aspx page is blank; in the page codebehind you simply write the csv to the response stream and end it.

You can add the following to the (I believe this is correct) Load event:

string attachment = "attachment; filename=MyCsvLol.csv";
HttpContext.Current.Response.AddHeader("content-disposition", attachment);
HttpContext.Current.Response.ContentType = "text/csv";
HttpContext.Current.Response.AddHeader("Pragma", "public");

var sb = new StringBuilder();
foreach(var line in DataToExportToCSV)


writing to the response stream code ganked from here.

Add a background image to shape in XML Android

This is a corner image

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="">

        android:top="5dp" />

            <corners android:radius="10dp" />
                android:color="@color/white" />


iOS: set font size of UILabel Programmatically

Its BECAUSE there is no font family with name @"System" hence size:36 will also not work ...

Check the fonts available in xcode in attribute inspector and try

For Loop on Lua

Your problem is simple:

names = {'John', 'Joe', 'Steve'}
for names = 1, 3 do
  print (names)

This code first declares a global variable called names. Then, you start a for loop. The for loop declares a local variable that just happens to be called names too; the fact that a variable had previously been defined with names is entirely irrelevant. Any use of names inside the for loop will refer to the local one, not the global one.

The for loop says that the inner part of the loop will be called with names = 1, then names = 2, and finally names = 3. The for loop declares a counter that counts from the first number to the last, and it will call the inner code once for each value it counts.

What you actually wanted was something like this:

names = {'John', 'Joe', 'Steve'}
for nameCount = 1, 3 do
  print (names[nameCount])

The [] syntax is how you access the members of a Lua table. Lua tables map "keys" to "values". Your array automatically creates keys of integer type, which increase. So the key associated with "Joe" in the table is 2 (Lua indices always start at 1).

Therefore, you need a for loop that counts from 1 to 3, which you get. You use the count variable to access the element from the table.

However, this has a flaw. What happens if you remove one of the elements from the list?

names = {'John', 'Joe'}
for nameCount = 1, 3 do
  print (names[nameCount])

Now, we get John Joe nil, because attempting to access values from a table that don't exist results in nil. To prevent this, we need to count from 1 to the length of the table:

names = {'John', 'Joe'}
for nameCount = 1, #names do
  print (names[nameCount])

The # is the length operator. It works on tables and strings, returning the length of either. Now, no matter how large or small names gets, this will always work.

However, there is a more convenient way to iterate through an array of items:

names = {'John', 'Joe', 'Steve'}
for i, name in ipairs(names) do
  print (name)

ipairs is a Lua standard function that iterates over a list. This style of for loop, the iterator for loop, uses this kind of iterator function. The i value is the index of the entry in the array. The name value is the value at that index. So it basically does a lot of grunt work for you.

"implements Runnable" vs "extends Thread" in Java

Difference between Extending Thread and Implementing Runnable are:

enter image description here

Can promises have multiple arguments to onFulfilled?

Since functions in Javascript can be called with any number of arguments, and the document doesn't place any restriction on the onFulfilled() method's arguments besides the below clause, I think that you can pass multiple arguments to the onFulfilled() method as long as the promise's value is the first argument. it must be called after promise is fulfilled, with promise’s value as its first argument.

CSS: Position text in the middle of the page

Try this CSS:

h1 {
    left: 0;
    line-height: 200px;
    margin-top: -100px;
    position: absolute;
    text-align: center;
    top: 50%;
    width: 100%;


About the Full Screen And No Titlebar from manifest

Another way: add windowNoTitle and windowFullscreen attributes directly to the theme (you can find styles.xml file in res/values/ directory):

<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowFullscreen">true</item>

in the manifest file, in application specify your theme

    android:theme="@style/AppTheme" >

How can I use nohup to run process as a background process in linux?

In general, I use nohup CMD & to run a nohup background process. However, when the command is in a form that nohup won't accept then I run it through bash -c "...".

For example:

nohup bash -c "(time ./script arg1 arg2 > script.out) &> time_n_err.out" &

stdout from the script gets written to script.out, while stderr and the output of time goes into time_n_err.out.

So, in your case:

nohup bash -c "(time bash executeScript 1 input fileOutput > scrOutput) &> timeUse.txt" &

Convert image from PIL to openCV format

use this:

pil_image ='Image.jpg').convert('RGB') 
open_cv_image = numpy.array(pil_image) 
# Convert RGB to BGR 
open_cv_image = open_cv_image[:, :, ::-1].copy() 

How do I combine 2 javascript variables into a string

if you want to concatenate the string representation of the values of two variables, use the + sign :

var var1 = 1;
var var2 = "bob";
var var3 = var2 + var1;//=bob1

But if you want to keep the two in only one variable, but still be able to access them later, you could make an object container:

function Container(){
   this.variables = [];
Container.prototype.addVar = function(var){
Container.prototype.toString = function(){
   var result = '';
   for(var i in this.variables)
       result += this.variables[i];
   return result;

var var1 = 1;
var var2 = "bob";
var container = new Container();
container.toString();// = bob1

the advantage is that you can get the string representation of the two variables, bit you can modify them later :

container.variables[0] = 3;
container.variables[1] = "tom";
container.toString();// = tom3

SQL: set existing column as Primary Key in MySQL

If you want to do it with phpmyadmin interface:

Select the table -> Go to structure tab -> On the row corresponding to the column you want, click on the icon with a key

Decoding UTF-8 strings in Python

It's an encoding error - so if it's a unicode string, this ought to fix it:


If it's a plain string, you'll need an extra step:


Both of these will give you a unicode string.

By the way - to discover how a piece of text like this has been mangled due to encoding issues, you can use chardet:

>>> import chardet
>>> chardet.detect(u"And the Hip’s coming, too")
{'confidence': 0.5, 'encoding': 'windows-1252'}

"Series objects are mutable and cannot be hashed" error

gene_name = no_headers.iloc[1:,[1]]

This creates a DataFrame because you passed a list of columns (single, but still a list). When you later do this:


you now have a Series object with a single value. You can't hash the Series.

The solution is to create Series from the start.

gene_type = no_headers.iloc[1:,0]
gene_name = no_headers.iloc[1:,1]
disease_name = no_headers.iloc[1:,2]

Also, where you have orph_dict[gene_name[x]] =+ 1, I'm guessing that's a typo and you really mean orph_dict[gene_name[x]] += 1 to increment the counter.

How to reload / refresh model data from the server programmatically?

Before I show you how to reload / refresh model data from the server programmatically? I have to explain for you the concept of Data Binding. This is an extremely powerful concept that will truly revolutionize the way you develop. So may be you have to read about this concept from this link or this seconde link in order to unterstand how AngularjS work.

now I'll show you a sample example that exaplain how can you update your model from server.

HTML Code:

<div ng-controller="PersonListCtrl">
        <li ng-repeat="person in persons">
            Name: {{}}, Age {{person.age}}
   <button ng-click="updateData()">Refresh Data</button>

So our controller named: PersonListCtrl and our Model named: persons. go to your Controller js in order to develop the function named: updateData() that will be invoked when we are need to update and refresh our Model persons.

Javascript Code:

app.controller('adsController', function($log,$scope,...){


$scope.updateData = function(){
$http.get('/persons').success(function(data) {
       $scope.persons = data;// Update Model-- Line X


Now I explain for you how it work: when user click on button Refresh Data, the server will call to function updateData() and inside this function we will invoke our web service by the function $http.get() and when we have the result from our ws we will affect it to our model (Line X).Dice that affects the results for our model, our View of this list will be changed with new Data.

Retrieving Dictionary Value Best Practices

I imagine that trygetvalue is doing something more like:

  someVal = myDict[someKey];
  return true;
return false;

So hopefully no try/catch anywhere.

I think it is just a method of convenience really. I generally use it as it saves a line of code or two.

How do I compare two columns for equality in SQL Server?

CASE WHEN is the better option

    THEN '1' 
    ELSE '0' 
  AS MyDesiredResult
FROM Table1
INNER JOIN Table2 ON Table1.PrimaryKey = Table2.ForeignKey

How to submit a form when the return key is pressed?

I think you should actually have a submit button or a submit image... Do you have a specific reason for using a "submit div"? If you just want custom styles I recommend <input type="image"....

HTML input file selection event not firing upon selecting the same file

handleChange({target}) {
    const files = target.files
    target.value = ''

Prevent flex items from overflowing a container

One easy solution is to use overflow values other than visible to make the text flex basis width reset as expected.

  1. Here with value auto the text wraps as expected and the article content does not overflow main container.

  2. Also, the article flex value must either have a auto basis AND be able to shrink, OR, only grow AND explicit 0 basis

main, aside, article {_x000D_
  margin: 10px;_x000D_
  border: solid 1px #000;_x000D_
  border-bottom: 0;_x000D_
  height: 50px;_x000D_
  overflow: auto; /* 1. overflow not `visible` */_x000D_
main {_x000D_
  display: flex;_x000D_
aside {_x000D_
  flex: 0 0 200px;_x000D_
article {_x000D_
  flex: 1 1 auto; /* 2. Allow auto width content to shrink */_x000D_
  /* flex: 1 0 0; /* Or, explicit 0 width basis that grows */_x000D_
  <aside>x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x </aside>_x000D_
  <article>don't let flex item overflow container.... y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y </article>_x000D_

Counting the Number of keywords in a dictionary in python

Calling len() directly on your dictionary works, and is faster than building an iterator, d.keys(), and calling len() on it, but the speed of either will negligible in comparison to whatever else your program is doing.

d = {x: x**2 for x in range(1000)}

# 1000

# 1000

%timeit len(d)
# 41.9 ns ± 0.244 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

%timeit len(d.keys())
# 83.3 ns ± 0.41 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

What is DOM Event delegation?

A delegate in C# is similar to a function pointer in C or C++. Using a delegate allows the programmer to encapsulate a reference to a method inside a delegate object. The delegate object can then be passed to code which can call the referenced method, without having to know at compile time which method will be invoked.

See this link -->

IntelliJ: Working on multiple projects


Having all the related projects in the same root directory.


1) First you create a new Empty project

New empty project

2) Then you select the root directory of all you projects.

This will create a empty project, with a .idea directory that will simply remember the module organisation we are about to do in the next step

Select root directory

3) Then, in the next window, you import the different projects as modules

Import projects as modules

4) In the next window, to import each project, simply double click on the build.gradle, or pom.xml

The project will be imported as a new module. Select build file

5) Done, you now have all your projects as modules, opened on the same IntelliJ project


Reading CSV file and storing values into an array

Just came across this library:

Very intuitive and easy to use. Has a nuget package too which made is quick to implement: Also appears to be actively maintained which I like.

Configuring it to use a semi-colon is easy:

Resolving PKIX path building failed Error? PKIX path building failed: unable to find valid certification path to requested target

• When I got the error, I tried to Google out the meaning of the expression and I found, this issue occurs when a server changes their HTTPS SSL certificate, and our older version of java doesn’t recognize the root certificate authority (CA).

• If you can access the HTTPS URL in your browser then it is possible to update Java to recognize the root CA.

• In your browser, go to the HTTPS URL that Java could not access. Click on the HTTPS certificate chain (there is lock icon in the Internet Explorer), click on the lock to view the certificate.

• Go to “Details” of the certificate and “Copy to file”. Copy it in Base64 (.cer) format. It will be saved on your Desktop.

• Install the certificate ignoring all the alerts.

• This is how I gathered the certificate information of the URL that I was trying to access.

Now I had to make my java version to know about the certificate so that further it doesn’t refuse to recognize the URL. In this respect I must mention that I googled out that root certificate information stays by default in JDK’s \jre\lib\security location, and the default password to access is: changeit.

To view the cacerts information the following are the procedures to follow:

• Click on Start Button-->Run

• Type cmd. The command prompt opens (you may need to open it as administrator).

• Go to your Java/jreX/bin directory

• Type the following

keytool -list -keystore D:\Java\jdk1.5.0_12\jre\lib\security\cacerts

It gives the list of the current certificates contained within the keystore. It looks something like this:

C:\Documents and Settings\NeelanjanaG>keytool -list -keystore D:\Java\jdk1.5.0_12\jre\lib\security\cacerts

Enter keystore password: changeit

Keystore type: jks

Keystore provider: SUN

Your keystore contains 44 entries

verisignclass3g2ca, Mar 26, 2004, trustedCertEntry,

Certificate fingerprint (MD5): A2:33:9B:4C:74:78:73:D4:6C:E7:C1:F3:8D:CB:5C:E9

entrustclientca, Jan 9, 2003, trustedCertEntry,

Certificate fingerprint (MD5): 0C:41:2F:13:5B:A0:54:F5:96:66:2D:7E:CD:0E:03:F4

thawtepersonalbasicca, Feb 13, 1999, trustedCertEntry,

Certificate fingerprint (MD5): E6:0B:D2:C9:CA:2D:88:DB:1A:71:0E:4B:78:EB:02:41

addtrustclass1ca, May 1, 2006, trustedCertEntry,

Certificate fingerprint (MD5): 1E:42:95:02:33:92:6B:B9:5F:C0:7F:DA:D6:B2:4B:FC

verisignclass2g3ca, Mar 26, 2004, trustedCertEntry,

Certificate fingerprint (MD5): F8:BE:C4:63:22:C9:A8:46:74:8B:B8:1D:1E:4A:2B:F6

• Now I had to include the previously installed certificate into the cacerts.

• For this the following is the procedure:

keytool –import –noprompt –trustcacerts –alias ALIASNAME -file FILENAME_OF_THE_INSTALLED_CERTIFICATE -keystore PATH_TO_CACERTS_FILE -storepass PASSWORD

If you are using Java 7:

keytool –importcert –trustcacerts –alias ALIASNAME -file PATH_TO_FILENAME_OF_THE_INSTALLED_CERTIFICATE -keystore PATH_TO_CACERTS_FILE -storepass changeit

• It will then add the certificate information into the cacert file.

It is the solution I found for the Exception mentioned above!!

How can I backup a Docker-container with its data-volumes?

If you want a complete backup, you will need to perform a few steps:

  1. Commit the container to an image
  2. Save the image
  3. Backup the container's volume by creating a tar file of the volume's mount point in the container.
  4. Repeat steps 1-3 for the database container as well.

Note that doing just a Docker commit of the container to an image does NOT include volumes attached to the container (ref: Docker commit documentation).

"The commit operation will not include any data contained in volumes mounted inside the container."

How can I delete a file from a Git repository?

  1. First,Remove files from local repository.

    git rm -r File-Name

    or, remove files only from local repository but from filesystem

    git rm --cached File-Name

  2. Secondly, Commit changes into local repository.

    git commit -m "unwanted files or some inline comments"   
  3. Finally, update/push local changes into remote repository.

    git push 

DeprecationWarning: Buffer() is deprecated due to security and usability issues when I move my script to another server

var userPasswordString = new Buffer(baseAuth, 'base64').toString('ascii');

Change this line from your code to this -

var userPasswordString = Buffer.from(baseAuth, 'base64').toString('ascii');

or in my case, I gave the encoding in reverse order

var userPasswordString = Buffer.from(baseAuth, 'utf-8').toString('base64');

What is WebKit and how is it related to CSS?

Webkit is an HTML rendering engine used by Chrome and Safari.

It supports a number of custom CSS properties that are prefixed by -webkit-.

MSSQL Error 'The underlying provider failed on Open'

I had a similar problem: In my test-cases executions I always got this error. I found out, that my "Distributed Transaction Service" was not started (run: services.msc -> start "Distributed Transaction Service" (best to set it to start automatic)). After I did that, it worked like a charm...

How to change a string into uppercase

s = 'sdsd'
print (s.upper())
upper = raw_input('type in something lowercase.')
lower = raw_input('type in the same thing caps lock.')
print upper.upper()
print lower.lower()

How to select date without time in SQL

select DATE(field) from table;

field value: 2020-12-15 12:19:00

select value: 2020-12-15

ORA-01008: not all variables bound. They are bound

On Charles' comment problem: to make things worse, let

:p1 = 'TRIALDEV'

via a Command Parameter, then execute

select T.table_name as NAME, COALESCE(C.comments, '===') as DESCRIPTION
from all_all_tables T
Inner Join all_tab_comments C on T.owner = C.owner and T.table_name = C.table_name
where Upper(T.owner)=:p1
order by T.table_name

558 line(s) affected. Processing time: 00:00:00.6535711

and when changing the literal string from === to ---

select T.table_name as NAME, COALESCE(C.comments, '---') as DESCRIPTION

ORA-01008: not all variables bound

Both statements execute fine in SQL Developer. The shortened code:

            Using con = New OracleConnection(cs)
                Using cmd = con.CreateCommand()
                    cmd.CommandText = cmdText
                    cmd.Parameters.Add(pn, OracleDbType.NVarchar2, 250).Value = p
                    Dim tbl = New DataTable
                    Dim da = New OracleDataAdapter(cmd)
                    Return tbl
                End Using
            End Using

using Oracle.ManagedDataAccess.dll Version with the default settings in VS2015 on the .Net 4.61 platform.

So somewhere in the call chain, there might be a parser that is a bit too aggressively looking for one-line-comments started by -- in the commandText. But even if this would be true, the error message "not all variables bound" is at least misleading.

TSQL - Cast string to integer or return default value

My solution to this issue was to create the function shown below. My requirements included that the number had to be a standard integer, not a BIGINT, and I needed to allow negative numbers and positive numbers. I have not found a circumstance where this fails.

CREATE FUNCTION [dbo].[udfIsInteger]
    -- Add the parameters for the function here
    @Value nvarchar(max)
    -- Declare the return variable here
    DECLARE @Result int = 0

    -- Add the T-SQL statements to compute the return value here
    DECLARE @MinValue nvarchar(11) = '-2147483648'
    DECLARE @MaxValue nvarchar(10) = '2147483647'

    SET @Value = ISNULL(@Value,'')

    IF LEN(@Value)=0 OR 
      ISNUMERIC(@Value)<>1 OR
      (LEFT(@Value,1)='-' AND LEN(@Value)>11) OR
      (LEFT(@Value,1)='-' AND LEN(@Value)=11 AND @Value>@MinValue) OR
      (LEFT(@Value,1)<>'-' AND LEN(@Value)>10) OR
      (LEFT(@Value,1)<>'-' AND LEN(@Value)=10 AND @Value>@MaxValue)

    DECLARE @cnt int = 0
    WHILE @cnt<LEN(@Value)
      SET @cnt=@cnt+1
      IF SUBSTRING(@Value,@cnt,1) NOT IN ('-','0','1','2','3','4','5','6','7','8','9') GOTO FINISHED
    SET @Result=1

    -- Return the result of the function
    RETURN @Result


What is the command to truncate a SQL Server log file?

if I remember well... in query analyzer or equivalent:


DBCC SHRINKFILE (  databasename_Log, 1)

difference between primary key and unique key

For an organization or a business, there are so many physical entities (such as people, resources, machines, etc.) and virtual entities (their Tasks, transactions, activities). Typically, business needs to record and process information of those business entities. These business entities are identified within a whole business domain by a Key.

As per RDBMS prospective, Key (a.k.a Candidate Key) is a value or set of values that uniquely identifies an entity.

For a DB-Table, there are so many keys are exist and might be eligible for Primary Key. So that all keys, primary key, unique key, etc are collectively called as Candidate Key. However, DBA selected a key from candidate key for searching records is called Primary key.

Difference between Primary Key and Unique key

1. Behavior: Primary Key is used to identify a row (record) in a table, whereas Unique-key is to prevent duplicate values in a column (with the exception of a null entry).

2. Indexing: By default SQL-engine creates Clustered Index on primary-key if not exists and Non-Clustered Index on Unique-key.

3. Nullability: Primary key does not include Null values, whereas Unique-key can.

4. Existence: A table can have at most one primary key, but can have multiple Unique-key.

5. Modifiability: You can’t change or delete primary values, but Unique-key values can.

For more information and Examples:

How do you add Boost libraries in CMakeLists.txt?

I agree with the answers 1 and 2. However, I prefer to specify each library separately. This makes the depencencies clearer in big projects. Yet, there is the danger of mistyping the (case-sensitive) variable names. In that case there is no direct cmake error but some undefined references linker issues later on, which may take some time to resolve. Therefore I use the following cmake function:

  foreach(lib ${ARGV}) 
    if(DEFINED ${lib})
    else(DEFINED ${lib})
      message(SEND_ERROR "Variable ${lib} is not defined")
    endif(DEFINED ${lib})

For the example mentioned above, this looks like:

target_link_libraries( run ${Boost_PROGRAM_OPTIONS_LIBRARY} ${Boost_REGEX_LIBRARY} )

If I had written "BOOST_PROGRAM_OPTIONS_LIBRARY" there would have been an error triggered by cmake and not much later triggered by the linker.

Spring - applicationContext.xml cannot be opened because it does not exist

If you use maven, create a directory called resources in the main directory, and then copy your applicationContext.xml into it.

From your java code call:

ApplicationContext appCtx = new ClassPathXmlApplicationContext("applicationContext.xml");

how can I login anonymously with ftp (/usr/bin/ftp)?

Anonymous FTP usage is covered by RFC 1635: How to Use Anonymous FTP:

What is Anonymous FTP?

Anonymous FTP is a means by which archive sites allow general access to their archives of information. These sites create a special account called "anonymous".

Traditionally, this special anonymous user account accepts any string as a password, although it is common to use either the password "guest" or one's electronic mail (e-mail) address. Some archive sites now explicitly ask for the user's e-mail address and will not allow login with the "guest" password. Providing an e-mail address is a courtesy that allows archive site operators to get some idea of who is using their services.

These are general recommendations, though. Each FTP server may have its own guidelines.

For sample use of the ftp command on anonymous FTP access, see appendix A: ftp
Connected to
220 FTP server (Wed May 4 12:15:15 PDT 1994) ready.
Name ( anonymous
331 Guest login ok, send your complete e-mail address as password.
230-Welcome to the NASA Network Applications and Info Center Archive
230-     Access to NAIC's online services is also available through:
230-        Gopher         - (port 70)
230-    World-Wide-Web -
230-        If you experience any problems please send email to
230-                    [email protected]
230-                 or call +1 (800) 858-9947
230-Please read the file README
230-  it was last modified on Fri Dec 10 13:06:33 1993 - 165 days ago
230 Guest login ok, access restrictions apply.
ftp> cd files/rfc
250-Please read the file README.rfc
250-  it was last modified on Fri Jul 30 16:47:29 1993 - 298 days ago
250 CWD command successful.
ftp> get rfc959.txt
200 PORT command successful.
150 Opening ASCII mode data connection for rfc959.txt (147316 bytes).
226 Transfer complete.
local: rfc959.txt remote: rfc959.txt
151249 bytes received in 0.9 seconds (1.6e+02 Kbytes/s)
ftp> quit
221 Goodbye.

See also the example session at the University of Edinburgh site.

Getting a link to go to a specific section on another page

I tried the above answer - using page.html#ID_name it gave me a 404 page doesn't exist error.

Then instead of using .html, I simply put a slash / before the # and that worked fine. So my example on the sending page between the link tags looks like:

<a href= "http://my">El Chorro</a>

Just use / instead of .html.

Get random boolean in Java

The easiest way to initialize a random number generator is to use the parameterless constructor, for example

Random generator = new Random();

However, in using this constructor you should recognize that algorithmic random number generators are not truly random, they are really algorithms that generate a fixed but random-looking sequence of numbers.

You can make it appear more 'random' by giving the Random constructor the 'seed' parameter, which you can dynamically built by for example using system time in milliseconds (which will always be different)

List of remotes for a Git repository?

None of those methods work the way the questioner is asking for and which I've often had a need for as well. eg:

$ git remote
fatal: Not a git repository (or any of the parent directories): .git
$ git remote user@bserver
fatal: Not a git repository (or any of the parent directories): .git
$ git remote user@server:/home/user
fatal: Not a git repository (or any of the parent directories): .git
$ git ls-remote
fatal: No remote configured to list refs from.
$ git ls-remote user@server:/home/user
fatal: '/home/user' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

The whole point of doing this is that you do not have any information except the remote user and server and want to find out what you have access to.

The majority of the answers assume you are querying from within a git working set. The questioner is assuming you are not.

As a practical example, assume there was a repository foo.git on the server. Someone in their wisdom decides they need to change it to foo2.git. It would really be nice to do a list of a git directory on the server. And yes, I see the problems for git. It would still be nice to have though.

Is it possible to display my iPhone on my computer monitor?

The latest SDKs (beginning with 2.2, I believe), include TV-Out functionality. With a special cable connected to the iPhone dock connector, a program can send RCA signals representing its current screen contents through the iPhone->RCA cable. If you have a TV Tuner for your computer (i.e. I have an EyeTV Hybrid) with RCA inputs, you can display the screen contents of your iPhone directly in the TV viewer.

Creating virtual directories in IIS express

@Be.St.'s aprroach is true, but incomplete. I'm just copying his explanation with correcting the incorrect part.

IIS express configuration is managed by applicationhost.config.
You can find it in

Users\<username>\Documents\IISExpress\config folder.

Inside you can find the sites section that hold a section for each IIS Express configured site.

Add (or modify) a site section like this:

<site name="WebSiteWithVirtualDirectory" id="20">
   <application path="/" applicationPool="Clr4IntegratedAppPool">
     <virtualDirectory path="/" physicalPath="c:\temp\website1" />
     <virtualDirectory path="/OffSiteStuff" physicalPath="d:\temp\SubFolderApp" />
      <binding protocol="http" bindingInformation="*:1132:localhost" />

Instead of adding a new application block, you should just add a new virtualDirectory element to the application parent element.

Edit - Visual Studio 2015

If you're looking for the applicationHost.config file and you're using VS2015 you'll find it in:


How can I use if/else in a dictionary comprehension?

You've already got it: A if test else B is a valid Python expression. The only problem with your dict comprehension as shown is that the place for an expression in a dict comprehension must have two expressions, separated by a colon:

{ (some_key if condition else default_key):(something_if_true if condition
          else something_if_false) for key, value in dict_.items() }

The final if clause acts as a filter, which is different from having the conditional expression.

Worth mentioning that you don't need to have an if-else condition for both the key and the value. For example, {(a if condition else b): value for key, value in dict.items()} will work.

Android image caching

Even later answer, but I wrote an Android Image Manager that handles caching transparently (memory and disk). The code is on Github

I didn't find "ZipFile" class in the "System.IO.Compression" namespace

you can use an external package if you cant upgrade to 4.5. One such is Ionic.Zip.dll from DotNetZipLib.

using Ionic.Zip;

you can download it here, its free.

How do I redirect with JavaScript?

To redirect to another page, you can use:

window.location = "";

Button that refreshes the page on click

Use onClick with one of the following:

window.location.reload(), i.e.:

<button onClick="window.location.reload();">Refresh Page</button>

Or history.go(0), i.e.:

<button onClick="history.go(0);">Refresh Page</button>

Or window.location.href=window.location.href for 'full' reload, i.e.:

<button onClick="window.location.href=window.location.href">Refresh Page</button>

MDN page on the <button> element.

PHP: How to get referrer URL?

Underscore. Not space.


How to implement class constants?

TypeScript 2.0 has the readonly modifier:

class MyClass {
    readonly myReadOnlyProperty = 1;

    myMethod() {
        this.myReadOnlyProperty = 5; // error, readonly

new MyClass().myReadOnlyProperty = 5; // error, readonly

It's not exactly a constant because it allows assignment in the constructor, but that's most likely not a big deal.

Alternative Solution

An alternative is to use the static keyword with readonly:

class MyClass {
    static readonly myReadOnlyProperty = 1;

    constructor() {
        MyClass.myReadOnlyProperty = 5; // error, readonly

    myMethod() {
        MyClass.myReadOnlyProperty = 5; // error, readonly

MyClass.myReadOnlyProperty = 5; // error, readonly

This has the benefit of not being assignable in the constructor and only existing in one place.

Decoding base64 in batch

Actually Windows does have a utility that encodes and decodes base64 - CERTUTIL

I'm not sure what version of Windows introduced this command.

To encode a file:

certutil -encode inputFileName encodedOutputFileName

To decode a file:

certutil -decode encodedInputFileName decodedOutputFileName

There are a number of available verbs and options available to CERTUTIL.

To get a list of nearly all available verbs:

certutil -?

To get help on a particular verb (-encode for example):

certutil -encode -?

To get complete help for nearly all verbs:

certutil -v -?

Mysteriously, the -encodehex verb is not listed with certutil -? or certutil -v -?. But it is described using certutil -encodehex -?. It is another handy function :-)


Regarding David Morales' comment, there is a poorly documented type option to the -encodehex verb that allows creation of base64 strings without header or footer lines.

certutil [Options] -encodehex inFile outFile [type]

A type of 1 will yield base64 without the header or footer lines.

See for a brief listing of the available type formats. And for a more in depth look at the available formats, see

Not investigated, but the -decodehex verb also has an optional trailing type argument.

How to use mod operator in bash?

Try the following:

 for i in {1..600}; do echo wget$(($i % 5)); done

The $(( )) syntax does an arithmetic evaluation of the contents.

When should I use GET or POST method? What's the difference between them?

There are two common "security" implications to using GET. Since data appears in the URL string its possible someone looking over your shoulder at Address Bar/URL may be able to view something they should not be privy to such as a session cookie that could potentially be used to hijack your session. Keep in mind everyone has camera phones.

The other security implication of GET has to do with GET variables being logged to most web servers access log as part of the requesting URL. Depending on the situation, regulatory climate and general sensitivity of the data this can potentially raise concerns.

Some clients/firewalls/IDS systems may frown upon GET requests containing an excessive amount of data and may therefore provide unreliable results.

POST supports advanced functionality such as support for multi-part binary input used for file uploads to web servers.

POST requires a content-length header which may increase the complexity of an application specific client implementation as the size of data submitted must be known in advance preventing a client request from being formed in an exclusively single-pass incremental mode. Perhaps a minor issue for those choosing to abuse HTTP by using it as an RPC (Remote Procedure Call) transport.

Others have already done a good job in covering the semantic differences and the "when" part of this question.

SQL Row_Number() function in Where Clause

       RowNum = row_number() OVER (order by employee_id)
    from V_EMPLOYEE 
SELECT  employee_id
FROM    MyCte
WHERE   RowNum > 0
ORDER BY employee_id

How to select from subquery using Laravel Query Builder?

The solution of @JarekTkaczyk it is exactly what I was looking for. The only thing I miss is how to do it when you are using DB::table() queries. In this case, this is how I do it:

$other = DB::table( DB::raw("({$sub->toSql()}) as sub") )->select(
    DB::raw('sum( qty ) as qty'), 
$other->mergeBindings( $sub );
print $other->toSql();

Special atention how to make the mergeBindings without using the getQuery() method

Java - Convert String to valid URI object

If you don't like libraries, how about this?

Note that you should not use this function on the whole URL, instead you should use this on the components...e.g. just the "a b" component, as you build up the URL - otherwise the computer won't know what characters are supposed to have a special meaning and which ones are supposed to have a literal meaning.

/** Converts a string into something you can safely insert into a URL. */
public static String encodeURIcomponent(String s)
    StringBuilder o = new StringBuilder();
    for (char ch : s.toCharArray()) {
        if (isUnsafe(ch)) {
            o.append(toHex(ch / 16));
            o.append(toHex(ch % 16));
        else o.append(ch);
    return o.toString();

private static char toHex(int ch)
    return (char)(ch < 10 ? '0' + ch : 'A' + ch - 10);

private static boolean isUnsafe(char ch)
    if (ch > 128 || ch < 0)
        return true;
    return " %$&+,/:;=?@<>#%".indexOf(ch) >= 0;

How to check if a class inherits another class without instantiating it?

To check for assignability, you can use the Type.IsAssignableFrom method:


This will work as you expect for type-equality, inheritance-relationships and interface-implementations but not when you are looking for 'assignability' across explicit / implicit conversion operators.

To check for strict inheritance, you can use Type.IsSubclassOf:


count number of characters in nvarchar column


SELECT length(yourfield) FROM table;

Syntax for if/else condition in SCSS mixin

You could default the parameter to null or false.
This way, it would be shorter to test if a value has been passed as parameter.

@mixin clearfix($width: null) {

  @if not ($width) {

    // if width is not passed, or empty do this

  } @else {

    display: inline-block;
    width: $width;


Excel SUMIF between dates

One more solution when you want to use data from any sell ( in the key C3)


What does the Ellipsis object do?

This is equivalent.

l=[..., 1,2,3]
l=[Ellipsis, 1,2,3]

... is a constant defined inside built-in constants.


The same as the ellipsis literal “...”. Special value used mostly in conjunction with extended slicing syntax for user-defined container data types.

Removing html5 required attribute with jQuery

<script src=""></script>

Get full query string in C# ASP.NET

Just use Request.QueryString.ToString() to get full query string, like this:

string URL = ""+Request.Querystring.ToString();

How to open existing project in Eclipse

i use Mac and i deleted ADT bundle source. faced the same error so i went to project > clean and adb ran normally.

How do I expand the output display to see more columns of a pandas DataFrame?

You can also try in a loop:

for col in df.columns: 

MaxJsonLength exception in ASP.NET MVC during JavaScriptSerializer

You can try define in your LINQ expression only the field's that you will need.

Example. Imagine that you have an Model with Id, Name, Phone and Picture (byte array) and need to load from json into an select list.

LINQ Query:

var listItems = (from u in Users where select u).ToList();

The problem here is "select u" that get all fields. So, if you have big pictures, booomm.

How to solve? very, very simple.

var listItems = (from u in Users where select new {u.Id, u.Name}).ToList();

The best practices is select only the field that you will use.

Remember. This is a simple tip, but can help many ASP.NET MVC developpers.

Disable browsers vertical and horizontal scrollbars

So far we have overflow:hidden on the body. However IE doesn't always honor that and you need to put scroll="no" on the body element as well and/or place overflow:hidden on the html element as well.

You can take this further when you need to 'take control' of the view port you can do this:-

 body {width:100%; height:100%; overflow:hidden; margin:0; }
 html {width:100%; height:100%; overflow:hidden; }

An element granted height 100% in the body has the full height of the window viewport, and element positioned absolutely using bottom:nnPX will be set nn pixels above the bottom edge of the window, etc.

Example: Communication between Activity and Service using Messaging

This is how I implemeted Activity->Service Communication: on my Activity i had

private static class MyResultReciever extends ResultReceiver {
     * Create a new ResultReceive to receive results.  Your
     * {@link #onReceiveResult} method will be called from the thread running
     * <var>handler</var> if given, or from an arbitrary thread if null.
     * @param handler
     public MyResultReciever(Handler handler) {

     protected void onReceiveResult(int resultCode, Bundle resultData) {
         if (resultCode == 100) {

And then I used this to start my Service

protected void onCreate(Bundle savedInstanceState) {
MyResultReciever resultReciever = new MyResultReciever(handler);
        service = new Intent(this, MyService.class);
        service.putExtra("receiver", resultReciever);

In my Service i had

public int onStartCommand(Intent intent, int flags, int startId) {
    if (intent != null)
        resultReceiver = intent.getParcelableExtra("receiver");
    return Service.START_STICKY;

Hope this Helps

Laravel redirect back to original destination after login

First, you should know, how you redirect user to 'login' route:

return redirect()->guest('/signin');

Not like this:

return redirect()->intended('/signin');

How do you run a single query through mysql from the command line?

If it's a query you run often, you can store it in a file. Then any time you want to run it:

mysql < thefile

(with all the login and database flags of course)

Good tool for testing socket connections?

Another tool is tcpmon. This is a java open-source tool to monitor a TCP connection. It's not directly a test server. It is placed in-between a client and a server but allow to see what is going through the "tube" and also to change what is going through.

jQuery - Illegal invocation

My problem was unrelated to processData. It was because I sent a function that cannot be called later with apply because it did not have enough arguments. Specifically I shouldn't have used alert as the error callback.

    url: csvApi,
    success: parseCsvs,
    dataType: "json",
    timeout: 5000,
    processData: false,
    error: alert

See this answer for more information on why that can be a problem: Why are certain function calls termed "illegal invocations" in JavaScript?

The way I was able to discover this was by adding a console.log(list[ firingIndex ]) to jQuery so I could track what it was firing.

This was the fix:

function myError(jqx, textStatus, errStr) {

    url: csvApi,
    success: parseCsvs,
    dataType: "json",
    timeout: 5000,
    error: myError // Note that passing `alert` instead can cause a "jquery.js:3189 Uncaught TypeError: Illegal invocation" sometimes

PostgreSQL wildcard LIKE for any of a list of words

You can use Postgres' SIMILAR TO operator which supports alternations, i.e.

select * from table where lower(value) similar to '%(foo|bar|baz)%';

Unable to make the session state request to the session state server

If you need to change HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\AllowRemoteConnection to 1, remember to restart the state service after you change the parameter.

Exception : AAPT2 error: check logs for details




Plot multiple columns on the same graph in R

A very simple solution:

df <- read.csv("df.csv",sep=",",head=T)
x <- cbind(df$Xax,df$Xax,df$Xax,df$Xax)
y <- cbind(df$A,df$B,df$C,df$D)

please note it just plots the data and it does not plot any regression line.

What's the difference between RANK() and DENSE_RANK() functions in oracle?

Rank(), Dense_rank(), row_number() These all are window functions that means they act as window over some ordered input set at first. These windows have different functionality attached to it based on the requirement. Heres the above 3 :


Starting by row_number() as this forms the basis of these related window functions. row_number() as the name suggests gives a unique number to the set of rows over which its been applied. Similar to giving a serial number to each row.


A subversion of row_number() can be said as rank(). Rank() is used to give same serial number to those ordered set rows which are duplicates but it still keeps the count mantained as similar to a row_number() for all those after duplicates rank() meaning as from below eg. For data 2 row_number() =rank() meaning both just differs in the form of duplicates.

Data row_number() rank() dense_rank() 
    1         1                    1       1
    1         2                    1       1
    1         3                    1       1
    2         4                    4       2


Dense_rank() is an extended version of rank() as the name suggests its dense because as you can see from the above example rank() = dense_rank() for all data 1 but just that for data 2 it differs in the form that it mantains the order of rank() from previous rank() not the actual data

Object not found! The requested URL was not found on this server. localhost

One thing I found out is that your folder holding your php/html files cannot be named the same name as the folder in your HTDOCS carrying your project.

DateTimeFormat in TypeScript

This should work...

var displayDate = new Date().toLocaleDateString();


But I suspect you are trying it on something else, for example:

var displayDate =; // No!


How to add default value for html <textarea>?

You can use this.innerHTML.

<textarea name="message" rows = "10" cols = "100" onfocus="this.innerHTML=''"> Enter your message here... </textarea>

When text area is focused, it basically makes the innerHTML of the textarea an empty string.

pull out p-values and r-squared from a linear regression

For the final p-value displayed at the end of summary(), the function uses pf() to calculate from the summary(fit)$fstatistic values.

fstat <- summary(fit)$fstatistic
pf(fstat[1], fstat[2], fstat[3], lower.tail=FALSE)

Source: [1], [2]

Alternative to the HTML Bold tag

Nowadays people tend to use website builders (CMS like Wordpress) instead of coding their own blog from scratch. Even professional web developers do it because it's faster.

It would be nice if you could mention the advantages and things to keep in mind when coding your own blog in real life, for example:

  • More flexibility (customization)
  • Pay a domain name
  • Pay and choose a web hosting
  • Security and maintenance
  • Copyright and license of some website builders' templates and graphics. Your website could be locked to a particular web host if you used your host's website builder. So you cannot move to another web host, because if you do you could no longer use that template.
  • Experience trouble when asking for website builder's tech support when the website goes down.
  • Some templates are not search engine friendly and this affects your website ranking (SEO)

Anyways, you can use css/css3 or JavaScript for making interactive webpage. Even you can upload your all sort of code into a server formatting the default blog theme.

numbers not allowed (0-9) - Regex Expression in javascript

Something as simple as [a-z]+, or perhaps [\S]+, or even [a-zA-Z]+?

JSON to pandas DataFrame

Once you have the flattened DataFrame obtained by the accepted answer, you can make the columns a MultiIndex ("fancy multiline header") like this:

df.columns = pd.MultiIndex.from_tuples([tuple(c.split('.')) for c in df.columns])

What is the difference between char * const and const char *?

// Some more complex constant variable/pointer declaration.
// Observing cases when we get error and warning would help
// understanding it better.

int main(void)
  char ca1[10]= "aaaa"; // char array 1
  char ca2[10]= "bbbb"; // char array 2

  char *pca1= ca1;
  char *pca2= ca2;

  char const *ccs= pca1;
  char * const csc= pca2;
  ccs[1]='m';  // Bad - error: assignment of read-only location ‘*(ccs + 1u)’
  ccs= csc;    // Good

  csc[1]='n';  // Good
  csc= ccs;    // Bad - error: assignment of read-only variable ‘csc’

  char const **ccss= &ccs;     // Good
  char const **ccss1= &csc;    // Bad - warning: initialization from incompatible pointer type

  char * const *cscs= &csc;    // Good
  char * const *cscs1= &ccs;   // Bad - warning: initialization from incompatible pointer type

  char ** const cssc=   &pca1; // Good
  char ** const cssc1=  &ccs;  // Bad - warning: initialization from incompatible pointer type
  char ** const cssc2=  &csc;  // Bad - warning: initialization discards ‘const’
                               //                qualifier from pointer target type

  *ccss[1]= 'x'; // Bad - error: assignment of read-only location ‘**(ccss + 8u)’
  *ccss= ccs;    // Good
  *ccss= csc;    // Good
  ccss= ccss1;   // Good
  ccss= cscs;    // Bad - warning: assignment from incompatible pointer type

  *cscs[1]= 'y'; // Good
  *cscs= ccs;    // Bad - error: assignment of read-only location ‘*cscs’
  *cscs= csc;    // Bad - error: assignment of read-only location ‘*cscs’
  cscs= cscs1;   // Good
  cscs= cssc;    // Good

  *cssc[1]= 'z'; // Good
  *cssc= ccs;    // Bad - warning: assignment discards ‘const’
                 //                qualifier from pointer target type
  *cssc= csc;    // Good
  *cssc= pca2;   // Good
  cssc= ccss;    // Bad - error: assignment of read-only variable ‘cssc’
  cssc= cscs;    // Bad - error: assignment of read-only variable ‘cssc’
  cssc= cssc1;   // Bad - error: assignment of read-only variable ‘cssc’

Split string in Lua?

Because there are more than one way to skin a cat, here's my approach:


#!/usr/bin/env lua

local content = [=[
Lorem ipsum dolor sit amet, consectetur adipisicing elit,
sed do eiusmod tempor incididunt ut labore et dolore magna 
aliqua. Ut enim ad minim veniam, quis nostrud exercitation 
ullamco laboris nisi ut aliquip ex ea commodo consequat.

local function split(str, sep)
   local result = {}
   local regex = ("([^%s]+)"):format(sep)
   for each in str:gmatch(regex) do
      table.insert(result, each)
   return result

local lines = split(content, "\n")
for _,line in ipairs(lines) do

Output: Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.


The gmatch function works as an iterator, it fetches all the strings that match regex. The regex takes all characters until it finds a separator.

java.sql.SQLException Parameter index out of range (1 > number of parameters, which is 0)

This is an issue with the jdbc Driver version. I had this issue when I was using mysql-connector-java-commercial-5.0.3-bin.jar but when I changed to a later driver version mysql-connector-java-5.1.22.jar, the issue was fixed.

No plot window in matplotlib

If you are user of Anaconda and Spyder then best solution for you is that :

Tools --> Preferences --> Ipython console --> Graphic Section

Then in the Support for graphics (Matplotlib) section:

select two avaliable options

and in the Graphics Backend:

select Automatic

CSS scale height to match width - possibly with a formfactor

I've made similar thing with YouTube's IFRAME where the iframe is inside a grid that always changed based on portrait/landscape so this code worked for:

So the code for this question is:

// Layout resize
let height = window.innerHeight;
let width = window.document.getElementById('player').parentNode.clientWidth;
    height = width / 1.77;
<div id="player"></div>

... etc ..

function onYouTubeIframeAPIReady() {
          // Layout resize
          let height = window.innerHeight;
          let width = window.document.getElementById('player').parentNode.clientWidth;
              height = width / 1.77;

          player = new YT.Player('player', {
            width: '100%',
            height: height,            
            videoId: currentVideoId,
            playerVars: {
              'autoplay': 0,
              'loop': 0,
              'mute': 0,
              'controls': 0,
              'enablejsapi': 1,
              'playsinline': 0,
              'rel': 0,
              'widget_referrer': 'http://my domain ...'
            events: {
              'onReady': onPlayerReady,
              'onStateChange': onPlayerStateChange,
              'onError': onError

Get value from input (AngularJS)

If you want to get values in Javascript on frontend, you can use the native way to do it by using :


Where "movie" is the name of your input <input type="text" name="movie">

If you want to get it on angular.js controller, you can use;


In C - check if a char exists in a char array

The equivalent C code looks like this:

#include <stdio.h>
#include <string.h>

// This code outputs: h is in "This is my test string"
int main(int argc, char* argv[])
   const char *invalid_characters = "hz";
   char *mystring = "This is my test string";
   char *c = mystring;
   while (*c)
       if (strchr(invalid_characters, *c))
          printf("%c is in \"%s\"\n", *c, mystring);


   return 0;

Note that invalid_characters is a C string, ie. a null-terminated char array.

Best way to get hostname with php

You could also use...

$hostname = getenv('HTTP_HOST');

PHP/MySQL Insert null values

This is one example where using prepared statements really saves you some trouble.

In MySQL, in order to insert a null value, you must specify it at INSERT time or leave the field out which requires additional branching:

INSERT INTO table2 (f1, f2)
  VALUES ('String Value', NULL);

However, if you want to insert a value in that field, you must now branch your code to add the single quotes:

INSERT INTO table2 (f1, f2)
  VALUES ('String Value', 'String Value');

Prepared statements automatically do that for you. They know the difference between string(0) "" and null and write your query appropriately:

$stmt = $mysqli->prepare("INSERT INTO table2 (f1, f2) VALUES (?, ?)");
$stmt->bind_param('ss', $field1, $field2);

$field1 = "String Value";
$field2 = null;


It escapes your fields for you, makes sure that you don't forget to bind a parameter. There is no reason to stay with the mysql extension. Use mysqli and it's prepared statements instead. You'll save yourself a world of pain.

Javascript regular expression password validation having special characters

If you check the length seperately, you can do the following:

var regularExpression  = /^[a-zA-Z]$/;

if (regularExpression.test(newPassword)) {
    alert("password should contain atleast one number and one special character");
    return false;

Eclipse error, "The selection cannot be launched, and there are no recent launches"

Eclipse can't work out what you want to run and since you've not run anything before, it can't try re-running that either.

Instead of clicking the green 'run' button, click the dropdown next to it and chose Run Configurations. On the Android tab, make sure it's set to your project. In the Target tab, set the tick box and options as appropriate to target your device. Then click Run. Keep an eye on your Console tab in Eclipse - that'll let you know what's going on. Once you've got your run configuration set, you can just hit the green 'run' button next time.

Sometimes getting everything to talk to your device can be problematic to begin with. Consider using an AVD (i.e. an emulator) as alternative, at least to begin with if you have problems. You can easily create one from the menu Window -> Android Virtual Device Manager within Eclipse.

To view the progress of your project being installed and started on your device, check the console. It's a panel within Eclipse with the tabs Problems/Javadoc/Declaration/Console/LogCat etc. It may be minimised - check the tray in the bottom right. Or just use Window/Show View/Console from the menu to make it come to the front. There are two consoles, Android and DDMS - there is a dropdown by its icon where you can switch.

Watermark / hint text / placeholder TextBox

There is an article on CodeProject on how to do it in "3 lines of XAML".

<Grid Background="{StaticResource brushWatermarkBackground}">
  <TextBlock Margin="5,2" Text="Type something..."
             Foreground="{StaticResource brushForeground}"
             Visibility="{Binding ElementName=txtUserEntry, Path=Text.IsEmpty,
                          Converter={StaticResource BooleanToVisibilityConverter}}" />
  <TextBox Name="txtUserEntry" Background="Transparent"
           BorderBrush="{StaticResource brushBorder}" />

Ok, well it might not be 3 lines of XAML formatted, but it is pretty simple.

One thing to note though, is that it uses a non-standard extension method on the Text property, called "IsEmpty". You need to implement this yourself, however the article doesn't seem to mention that.

javascript close current window

To close your current window using JS, do this. First open the current window to trick your current tab into thinking it has been opened by a script. Then close it using window.close(). The below script should go into the parent window, not the child window. You could run this after running the script to open the child.

<script type="text/javascript">'','_parent',''); 

How to make ConstraintLayout work with percentage values?

With the new release of ConstraintLayout v1.1 you can now do the following:

app:layout_constraintWidth_percent="0.65" />

This will constrain the button to be 20% the height and 65% of the width of the parent view.

Javascript: set label text

For a dynamic approach, if your labels are always in front of your text areas:


Mean Squared Error in Numpy?

Even more numpy

np.square(np.subtract(A, B)).mean()

iOS: Convert UTC NSDate to local Timezone

Convert your UTC date to Local Date

-(NSString *)getLocalDateTimeFromUTC:(NSString *)strDate
    NSDateFormatter *dtFormat = [[NSDateFormatter alloc] init];
    [dtFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    [dtFormat setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
    NSDate *aDate = [dtFormat dateFromString:strDate];

    [dtFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    [dtFormat setTimeZone:[NSTimeZone systemTimeZone]];

    return [dtFormat stringFromDate:aDate];

Use Like This

NSString *localDate = [self getLocalDateTimeFromUTC:@"yourUTCDate"];

Multiple Where clauses in Lambda expressions

You can include it in the same where statement with the && operator...

x=> x.Lists.Include(l => l.Title).Where(l=>l.Title != String.Empty 
    && l.InternalName != String.Empty)

You can use any of the comparison operators (think of it like doing an if statement) such as...

List<Int32> nums = new List<int>();


var results = nums.Where(x => x == 3 || x == 10);

...would bring back 3 and 10.