Programs & Examples On #Quantmod

quantmod is a package for R designed to assist quantitative traders in the development, testing, and deployment of statistically based trading models.

Error in model.frame.default: variable lengths differ

Joran suggested to first remove the NAs before running the model. Thus, I removed the NAs, run the model and obtained the residuals. When I updated model2 by inclusion of the lagged residuals, the error message did not appear again.

Remove NAs


Run the main model

model2<-gam(death ~ pm10 + s(trend,k=14*7)+ s(temp,k=5), data=df2, family=poisson)

Obtain residuals

resid2 <- residuals(model2,type="deviance")

Update model2 by including the lag 1 residuals

model2_1 <- update(model2,.~.+ Lag(resid2,1),  na.action=na.omit)

Unable to create/open lock file: /data/mongod.lock errno:13 Permission denied

If you literally want a one line equivalent to the commands in your original question, you could alias:

mongo --eval "db.getSiblingDB('admin').shutdownServer()"

Using JQuery to check if no radio button in a group has been checked

if ($("input[name='html_elements']:checked").size()==0) {
   alert('Nothing is checked!');
else {
  alert('One of the radio buttons is checked!');

Attach parameter to button.addTarget action in Swift

Swift 4.2


testButton.on(.touchUpInside) { (sender, event) in
    // You can use any reference initialized before the code block here
    // You can access self by adding [weak self] before (sender, event)
    // You can then either make self strong by using a guard statement or use a optional operator (?)
    print("user did press test button")

In the file UIButton+Events.swift I've created an extension method for UIButton that binds a UIControl.Event to a completion handler called EventHandler:

import UIKit

fileprivate var bindedEvents: [UIButton:EventBinder] = [:]

fileprivate class EventBinder {

    let event: UIControl.Event
    let button: UIButton
    let handler: UIButton.EventHandler
    let selector: Selector

    required init(
        _ event: UIControl.Event,
        on button: UIButton,
        withHandler handler: @escaping UIButton.EventHandler
    ) {
        self.event = event
        self.button = button
        self.handler = handler
        self.selector = #selector(performEvent(on:ofType:))
        button.addTarget(self, action: self.selector, for: event)

    deinit {
        button.removeTarget(self, action: selector, for: event)
        if let index = bindedEvents.index(forKey: button) {
            bindedEvents.remove(at: index)

private extension EventBinder {

    @objc func performEvent(on sender: UIButton, ofType event: UIControl.Event) {
        handler(sender, event)

extension UIButton {

    typealias EventHandler = (UIButton, UIControl.Event) -> Void

    func on(_ event: UIControl.Event, handler: @escaping EventHandler) {
        bindedEvents[self] = EventBinder(event, on: self, withHandler: handler)

The reason why I used a custom class for binding the event is to be able to dispose the reference later when the button is deintialised. This will prevent a possible memory leak from occurring. This wasn't possible within the UIButton its extension, because I'm not allowed to implement a property nor the deinit method.

How do I clear the std::queue efficiently?

Yes - a bit of a misfeature of the queue class, IMHO. This is what I do:

#include <queue>
using namespace std;;

int main() {
    queue <int> q1;
    // stuff
    q1 = queue<int>();  

Powershell: count members of a AD group

If you cannot utilize the ActiveDirectory Module or the Get-ADGroupMember cmdlet, you can do it with the LDAP "in chain"-matching rule:

$GroupDN = "CN=MyGroup,OU=Groups,DC=mydomain,DC=tld"
$LDAPFilter = "(&(objectClass=user)(objectCategory=Person)(memberOf:1.2.840.113556.1.4.1941:=$GroupDN))"

# Ideally using an instance of adsisearcher here:
Get-ADObject -LDAPFilter $LDAPFilter

See MSDN for additional LDAP matching rules implemented in Active Directory

Wait for a void async method

do a AutoResetEvent, call the function then wait on AutoResetEvent and then set it inside async void when you know it is done.

You can also wait on a Task that returns from your void async

IF function with 3 conditions

Using INDEX and MATCH for binning. Easier to maintain if we have more bins.

=INDEX({"Text 1","Text 2","Text 3"},MATCH(A2,{0,5,21,100}))

enter image description here

Installing jQuery?

Install JQuery with only JavaScript. This is not a very good solution if you are developing a website but it's great if you want JQuery in the JavaScript console of a random website that does not use JQuery already.

function loadScript(url, callback)
    // adding the script tag to the head as suggested before
   var head = document.getElementsByTagName('head')[0];
   var script = document.createElement('script');
   script.type = 'text/javascript';
   script.src = url;

   // then bind the event to the callback function 
   // there are several events for cross browser compatibility
   script.onreadystatechange = callback;
   script.onload = callback;

   // fire the loading

loadScript function thanks to e-satis's answer to Include JavaScript file inside JavaScript file?

Oracle PL/SQL - Raise User-Defined Exception With Custom SQLERRM

Yes. You just have to use the RAISE_APPLICATION_ERROR function. If you also want to name your exception, you'll need to use the EXCEPTION_INIT pragma in order to associate the error number to the named exception. Something like

SQL> ed
Wrote file afiedt.buf

  1  declare
  2    ex_custom EXCEPTION;
  3    PRAGMA EXCEPTION_INIT( ex_custom, -20001 );
  4  begin
  5    raise_application_error( -20001, 'This is a custom error' );
  6  exception
  7    when ex_custom
  8    then
  9      dbms_output.put_line( sqlerrm );
 10* end;
SQL> /
ORA-20001: This is a custom error

PL/SQL procedure successfully completed.

Force DOM redraw/refresh on Chrome/Mac

I had a react component list which when scrolled, then opened another page, then when returning back the list was not rendered on Safari iOS until page was scrolled. So this is the fix.

    componentDidMount() {
        setTimeout(() => {
            window.scrollBy(0, 0);
        }, 300);

Way to go from recursion to iteration

One pattern to look for is a recursion call at the end of the function (so called tail-recursion). This can easily be replaced with a while. For example, the function foo:

void foo(Node* node)
    if(node == NULL)
    // Do something with node...

ends with a call to foo. This can be replaced with:

void foo(Node* node)
    while(node != NULL)
        // Do something with node...
        node = node->right;

which eliminates the second recursive call.

How to inspect FormData?

Easy Method

I used this code in angular 8

var formData = new FormData();
formData.append('key1', 'value1');
formData.append('key2', 'value2');

 formData.forEach((value,key) => {

Node.js - Maximum call stack size exceeded


for me the program with the Max call stack wasn't because of my code. It ended up being a different issue which caused the congestion in the flow of the application. So because I was trying to add too many items to mongoDB without any configuration chances the call stack issue was popping and it took me a few days to figure out what was going on....that said:

Following up with what @Jeff Lowery answered: I enjoyed this answer so much and it sped up the process of what I was doing by 10x at least.

I'm new at programming but I attempted to modularize the answer it. Also, didn't like the error being thrown so I wrapped it in a do while loop instead. If anything I did is incorrect, please feel free to correct me.

module.exports = function(object) {
    const { max = 1000000000n, fn } = object;
    let counter = 0;
    let running = true;
    Error.stackTraceLimit = 100;
    const A = (fn) => {
        flipper = B;
    const B = (fn) => {
        flipper = A;
    let flipper = B;
    const then = process.hrtime.bigint();
    do {
        if (counter > max) {
            const now = process.hrtime.bigint();
            const nanos = now - then;
            console.log({ 'runtime(sec)': Number(nanos) / 1000000000.0 });
            running = false;
    } while (running);

Check out this gist to see the my files and how to call the loop.

WPF: Grid with column/row margin/padding?

RowDefinition and ColumnDefinition are of type ContentElement, and Margin is strictly a FrameworkElement property. So to your question, "is it easily possible" the answer is a most definite no. And no, I have not seen any layout panels that demonstrate this kind of functionality.

You can add extra rows or columns as you suggested. But you can also set margins on a Grid element itself, or anything that would go inside a Grid, so that's your best workaround for now.

How to convert a JSON string to a dictionary?

I've updated Eric D's answer for Swift 5:

 func convertStringToDictionary(text: String) -> [String:AnyObject]? {
    if let data = .utf8) {
        do {
            let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? [String:AnyObject]
            return json
        } catch {
            print("Something went wrong")
    return nil

INFO: No Spring WebApplicationInitializer types detected on classpath

For eclipse users: solution is simple just change the nature of project Spring Tools->add spring project nature


Installing OpenCV 2.4.3 in Visual C++ 2010 Express

1. Installing OpenCV 2.4.3

First, get OpenCV 2.4.3 from Its a self-extracting so just double click to start the installation. Install it in a directory, say C:\.

OpenCV self-extractor

Wait until all files get extracted. It will create a new directory C:\opencv which contains OpenCV header files, libraries, code samples, etc.

Now you need to add the directory C:\opencv\build\x86\vc10\bin to your system PATH. This directory contains OpenCV DLLs required for running your code.

Open Control PanelSystemAdvanced system settingsAdvanced Tab → Environment variables...

enter image description here

On the System Variables section, select Path (1), Edit (2), and type C:\opencv\build\x86\vc10\bin; (3), then click Ok.

On some computers, you may need to restart your computer for the system to recognize the environment path variables.

This will completes the OpenCV 2.4.3 installation on your computer.

2. Create a new project and set up Visual C++

Open Visual C++ and select FileNewProject...Visual C++Empty Project. Give a name for your project (e.g: cvtest) and set the project location (e.g: c:\projects).

New project dialog

Click Ok. Visual C++ will create an empty project.

VC++ empty project

Make sure that "Debug" is selected in the solution configuration combobox. Right-click cvtest and select PropertiesVC++ Directories.

Project property dialog

Select Include Directories to add a new entry and type C:\opencv\build\include.

Include directories dialog

Click Ok to close the dialog.

Back to the Property dialog, select Library Directories to add a new entry and type C:\opencv\build\x86\vc10\lib.

Library directories dialog

Click Ok to close the dialog.

Back to the property dialog, select LinkerInputAdditional Dependencies to add new entries. On the popup dialog, type the files below:


Note that the filenames end with "d" (for "debug"). Also note that if you have installed another version of OpenCV (say 2.4.9) these filenames will end with 249d instead of 243d (opencv_core249d.lib..etc).

enter image description here

Click Ok to close the dialog. Click Ok on the project properties dialog to save all settings.


These steps will configure Visual C++ for the "Debug" solution. For "Release" solution (optional), you need to repeat adding the OpenCV directories and in Additional Dependencies section, use:


instead of:


You've done setting up Visual C++, now is the time to write the real code. Right click your project and select AddNew Item...Visual C++C++ File.

Add new source file

Name your file (e.g: loadimg.cpp) and click Ok. Type the code below in the editor:

#include <opencv2/highgui/highgui.hpp>
#include <iostream>

using namespace cv;
using namespace std;

int main()
    Mat im = imread("c:/full/path/to/lena.jpg");
    if (im.empty()) 
        cout << "Cannot load image!" << endl;
        return -1;
    imshow("Image", im);

The code above will load c:\full\path\to\lena.jpg and display the image. You can use any image you like, just make sure the path to the image is correct.

Type F5 to compile the code, and it will display the image in a nice window.

First OpenCV program

And that is your first OpenCV program!

3. Where to go from here?

Now that your OpenCV environment is ready, what's next?

  1. Go to the samples dir → c:\opencv\samples\cpp.
  2. Read and compile some code.
  3. Write your own code.

How to search if dictionary value contains certain string with Python

Klaus solution has less overhead, on the other hand this one may be more readable

myDict = {'age': ['12'], 'address': ['34 Main Street, 212 First Avenue'],
          'firstName': ['Alan', 'Mary-Ann'], 'lastName': ['Stone', 'Lee']}

def search(myDict, lookup):
    for key, value in myDict.items():
        for v in value:
            if lookup in v:
                return key

search(myDict, 'Mary')

How to import a CSS file in a React Component

Using extract-css-chunks-webpack-plugin and css-loader loader work for me, see below:

webpack.config.js Import extract-css-chunks-webpack-plugin

const ExtractCssChunks = require('extract-css-chunks-webpack-plugin');

webpack.config.js Add the css rule, Extract css Chunks first then the css loader css-loader will embed them into the html document, ensure css-loader and extract-css-chunks-webpack-plugin are in the package.json dev dependencies

rules: [
        test: /\.css$/,
        use: [
            loader: ExtractCssChunks.loader,

webpack.config.js Make instance of the plugin

plugins: [
    new ExtractCssChunks({
      // Options similar to the same options in webpackOptions.output
      // both options are optional
      filename: '[name].css',
      chunkFilename: '[id].css'

And now importing css is possible And now in a tsx file like index.tsx i can use import like this import './Tree.css' where Tree.css contains css rules like

body {
    background: red;

My app is using typescript and this works for me, check my repo for the source :

Spring-boot default profile for integration tests

A delarative way to do that (In fact, a minor tweek to @Compito's original answer):

  1. Set in test/resources/
  2. Add test/resources/ for tests and override only the properties you need.

Checking Maven Version

Open command prompt go inside the maven folder and execute mvn -version, it will show you maven vesrion al

See :hover state in Chrome Developer Tools

Now you can see both the pseudo-class rules and force them on elements.

To see the rules like :hover in the Styles pane click the small :hov text in the top right.

Toggle element state

To force an element into :hover state, right click it and select :hover.

Force element state

Additional tips on the elements panel in Chrome Developer Tools Shortcuts.

jquery get all input from specific form

To iterate through all the inputs in a form you can do this:

$("form#formID :input").each(function(){
 var input = $(this); // This is the jquery object of the input, do what you will

This uses the jquery :input selector to get ALL types of inputs, if you just want text you can do :

$("form#formID input[type=text]")//...


Detecting a mobile browser

//true / false
function isMobile()
   return (/Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent) ); 

also you can follow this tutorial to detect a specific mobile. Click here.

How can I zoom an HTML element in Firefox and Opera?

zoom: 145%;
-moz-transform: scale(1.45);

use this to be on the safer side

Read and overwrite a file in Python

Honestly you can take a look at this class that I built which does basic file operations. The write method overwrites and append keeps old data.

class IO:
    def read(self, filename):
        toRead = open(filename, "rb")

        out =
        return out
    def write(self, filename, data):
        toWrite = open(filename, "wb")

        out = toWrite.write(data)

    def append(self, filename, data):
        append =
        self.write(filename, append+data)

Detecting when Iframe content has loaded (Cross browser)

For those using React, detecting a same-origin iframe load event is as simple as setting onLoad event listener on iframe element.

<iframe src={'path-to-iframe-source'} onLoad={this.loadListener} frameBorder={0} />

Remove local git tags that are no longer on the remote repository

All versions of Git since v1.7.8 understand git fetch with a refspec, whereas since v1.9.0 the --tags option overrides the --prune option. For a general purpose solution, try this:

$ git --version
git version 2.1.3

$ git fetch --prune origin "+refs/tags/*:refs/tags/*"
From ssh://xxx
 x [deleted]         (none)     -> rel_test

For further reading on how the "--tags" with "--prune" behavior changed in Git v1.9.0, see:

Change the row color in DataGridView based on the quantity of a cell value

Using the CellFormating event and the e argument:

If CInt(e.Value) < 5 Then e.CellStyle.ForeColor = Color.Red

Cannot install signed apk to device manually, got error "App not installed"

Android Studio 4.1.1 If you want to create the debug apk, and just before creating the apk you tried running on your phone/simulator (doing create signed apk right away will cause the APP NOT INSTALLED),YOU SHOULD CLEAN THE PROJECT before creating signed bundle/apk

Bootstrap modal in React.js

I was recently looking for a nice solution to this without adding React-Bootstrap to my project (as Bootstrap 4 is about to be released).

This is my solution:

let Modal = React.createClass({
        $(this.getDOMNode()).on('', this.props.handleHideModal);
        return (
          <div className="modal fade">
            <div className="modal-dialog">
              <div className="modal-content">
                <div className="modal-header">
                  <button type="button" className="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
                  <h4 className="modal-title">Modal title</h4>
                <div className="modal-body">
                  <p>One fine body&hellip;</p>
                <div className="modal-footer">
                  <button type="button" className="btn btn-default" data-dismiss="modal">Close</button>
                  <button type="button" className="btn btn-primary">Save changes</button>
        handleHideModal: React.PropTypes.func.isRequired

let App = React.createClass({
        return {view: {showModal: false}}
        this.setState({view: {showModal: false}})
        this.setState({view: {showModal: true}})
        <div className="row">
            <button className="btn btn-default btn-block" onClick={this.handleShowModal}>Open Modal</button>
            {this.state.view.showModal ? <Modal handleHideModal={this.handleHideModal}/> : null}

   <App />,

The main idea is to only render the Modal component into the React DOM when it is to be shown (in the App components render function). I keep some 'view' state that indicates whether the Modal is currently shown or not.

The 'componentDidMount' and 'componentWillUnmount' callbacks either hide or show the modal (once it is rendered into the React DOM) via Bootstrap javascript functions.

I think this solution nicely follows the React ethos but suggestions are welcome!

What is the difference between `sorted(list)` vs `list.sort()`?

The main difference is that sorted(some_list) returns a new list:

a = [3, 2, 1]
print sorted(a) # new list
print a         # is not modified

and some_list.sort(), sorts the list in place:

a = [3, 2, 1]
print a.sort() # in place
print a         # it's modified

Note that since a.sort() doesn't return anything, print a.sort() will print None.

Can a list original positions be retrieved after list.sort()?

No, because it modifies the original list.

What Regex would capture everything from ' mark to the end of a line?


I believe you need the option, Multiline.

How can I simulate an array variable in MySQL?

Both versions using sets didn't work for me (tested with MySQL 5.5). The function ELT() returns the whole set. Considering the WHILE statement is only avaible in PROCEDURE context i added it to my solution:


    SET @myArrayOfValue = '2,5,2,23,6,';

    WHILE (LOCATE(',', @myArrayOfValue) > 0)
        SET @value = LEFT(@myArrayOfValue, LOCATE(',',@myArrayOfValue) - 1);    
        SET @myArrayOfValue = SUBSTRING(@myArrayOfValue, LOCATE(',',@myArrayOfValue) + 1);

CALL __main__;

To be honest, i don't think this is a good practice. Even if its realy necessary, this is barely readable and quite slow.

.htaccess File Options -Indexes on Subdirectories

The correct answer is

Options -Indexes

You must have been thinking of

AllowOverride All

.htaccess files (or "distributed configuration files") provide a way to make configuration changes on a per-directory basis. A file, containing one or more configuration directives, is placed in a particular document directory, and the directives apply to that directory, and all subdirectories thereof.

What does "use strict" do in JavaScript, and what is the reasoning behind it?

Using 'use strict'; does not suddenly make your code better.

The JavaScript strict mode is a feature in ECMAScript 5. You can enable the strict mode by declaring this in the top of your script/function.

'use strict';

When a JavaScript engine sees this directive, it will start to interpret the code in a special mode. In this mode, errors are thrown up when certain coding practices that could end up being potential bugs are detected (which is the reasoning behind the strict mode).

Consider this example:

var a = 365;
var b = 030;

In their obsession to line up the numeric literals, the developer has inadvertently initialized variable b with an octal literal. Non-strict mode will interpret this as a numeric literal with value 24 (in base 10). However, strict mode will throw an error.

For a non-exhaustive list of specialties in strict mode, see this answer.

Where should I use 'use strict';?

  • In my new JavaScript application: Absolutely! Strict mode can be used as a whistleblower when you are doing something stupid with your code.

  • In my existing JavaScript code: Probably not! If your existing JavaScript code has statements that are prohibited in strict-mode, the application will simply break. If you want strict mode, you should be prepared to debug and correct your existing code. This is why using 'use strict'; does not suddenly make your code better.

How do I use strict mode?

  1. Insert a 'use strict'; statement on top of your script:

    // File: myscript.js
    'use strict';
    var a = 2;

    Note that everything in the file myscript.js will be interpreted in strict mode.

  2. Or, insert a 'use strict'; statement on top of your function body:

    function doSomething() {
        'use strict';

    Everything in the lexical scope of function doSomething will be interpreted in strict mode. The word lexical scope is important here. For example, if your strict code calls a function of a library that is not strict, only your code is executed in strict mode, and not the called function. See this answer for a better explanation.

What things are prohibited in strict mode?

I found a nice article describing several things that are prohibited in strict mode (note that this is not an exclusive list):


Historically, JavaScript has been confused about how functions are scoped. Sometimes they seem to be statically scoped, but some features make them behave like they are dynamically scoped. This is confusing, making programs difficult to read and understand. Misunderstanding causes bugs. It also is a problem for performance. Static scoping would permit variable binding to happen at compile time, but the requirement for dynamic scope means the binding must be deferred to runtime, which comes with a significant performance penalty.

Strict mode requires that all variable binding be done statically. That means that the features that previously required dynamic binding must be eliminated or modified. Specifically, the with statement is eliminated, and the eval function’s ability to tamper with the environment of its caller is severely restricted.

One of the benefits of strict code is that tools like YUI Compressor can do a better job when processing it.

Implied Global Variables

JavaScript has implied global variables. If you do not explicitly declare a variable, a global variable is implicitly declared for you. This makes programming easier for beginners because they can neglect some of their basic housekeeping chores. But it makes the management of larger programs much more difficult and it significantly degrades reliability. So in strict mode, implied global variables are no longer created. You should explicitly declare all of your variables.

Global Leakage

There are a number of situations that could cause this to be bound to the global object. For example, if you forget to provide the new prefix when calling a constructor function, the constructor's this will be bound unexpectedly to the global object, so instead of initializing a new object, it will instead be silently tampering with global variables. In these situations, strict mode will instead bind this to undefined, which will cause the constructor to throw an exception instead, allowing the error to be detected much sooner.

Noisy Failure

JavaScript has always had read-only properties, but you could not create them yourself until ES5’s Object.createProperty function exposed that capability. If you attempted to assign a value to a read-only property, it would fail silently. The assignment would not change the property’s value, but your program would proceed as though it had. This is an integrity hazard that can cause programs to go into an inconsistent state. In strict mode, attempting to change a read-only property will throw an exception.


The octal (or base 8) representation of numbers was extremely useful when doing machine-level programming on machines whose word sizes were a multiple of 3. You needed octal when working with the CDC 6600 mainframe, which had a word size of 60 bits. If you could read octal, you could look at a word as 20 digits. Two digits represented the op code, and one digit identified one of 8 registers. During the slow transition from machine codes to high level languages, it was thought to be useful to provide octal forms in programming languages.

In C, an extremely unfortunate representation of octalness was selected: Leading zero. So in C, 0100 means 64, not 100, and 08 is an error, not 8. Even more unfortunately, this anachronism has been copied into nearly all modern languages, including JavaScript, where it is only used to create errors. It has no other purpose. So in strict mode, octal forms are no longer allowed.

Et cetera

The arguments pseudo array becomes a little bit more array-like in ES5. In strict mode, it loses its callee and caller properties. This makes it possible to pass your arguments to untrusted code without giving up a lot of confidential context. Also, the arguments property of functions is eliminated.

In strict mode, duplicate keys in a function literal will produce a syntax error. A function can’t have two parameters with the same name. A function can’t have a variable with the same name as one of its parameters. A function can’t delete its own variables. An attempt to delete a non-configurable property now throws an exception. Primitive values are not implicitly wrapped.

Reserved words for future JavaScript versions

ECMAScript 5 adds a list of reserved words. If you use them as variables or arguments, strict mode will throw an error. The reserved words are:

implements, interface, let, package, private, protected, public, static, and yield

Further Reading

How to parse a query string into a NameValueCollection in .NET

let search =;


let qString = search.substring(1);

while(qString.indexOf("+") !== -1)

   qString  = qString.replace("+", "");

let qArray = qString.split("&");

let values = [];

for(let i = 0; i < qArray.length; i++){
   let pos = qArray[i].search("=");
   let keyVal = qArray[i].substring(0, pos);
   let dataVal = qArray[i].substring(pos + 1);
   dataVal = decodeURIComponent(dataVal);
   values[keyVal] = dataVal;

Oracle "Partition By" Keyword


 7839         10          4
 5555         10          4
 7934         10          4
 7782         10          4 --- 4 records in table for dept 10
 7902         20          4
 7566         20          4
 7876         20          4
 7369         20          4 --- 4 records in table for dept 20
 7900         30          6
 7844         30          6
 7654         30          6
 7521         30          6
 7499         30          6
 7698         30          6 --- 6 records in table for dept 30

Here we are getting count for respective deptno. As for deptno 10 we have 4 records in table emp similar results for deptno 20 and 30 also.

Compare objects in Angular

Bit late on this thread. angular.equals does deep check, however does anyone know that why its behave differently if one of the member contain "$" in prefix ?

You can try this Demo with following input

var obj3 = {}
obj3.a=  "b";
obj3.b.$c =true;

var obj4 = {}
obj4.a=  "b";
obj4.b.$c =true;


add new element in laravel collection object

If you want to add a product into the array you can use:

$item['product'] = $product;

How to add ASP.NET 4.0 as Application Pool on IIS 7, Windows 7

Open a windows command line. Switch directories to C:\Windows\Microsoft.Net\Framework\v4.0.xxxx where the x's are the build number. Type aspnet_regiis -ir and hit enter. This should register .Net v4.0 and create the application pools by default. If it doesn't, you will need to create them manually by right-clicking the Application Pools folder in IIS and choosing Add Application Pool.

Edit: As a reference, please refer to the section of the linked document referring to the -i argument.

How do I make a Git commit in the past?

The advice you were given is flawed. Unconditionally setting GIT_AUTHOR_DATE in an --env-filter would rewrite the date of every commit. Also, it would be unusual to use git commit inside --index-filter.

You are dealing with multiple, independent problems here.

Specifying Dates Other Than “now”

Each commit has two dates: the author date and the committer date. You can override each by supplying values through the environment variables GIT_AUTHOR_DATE and GIT_COMMITTER_DATE for any command that writes a new commit. See “Date Formats” in git-commit(1) or the below:

Git internal format = <unix timestamp> <time zone offset>, e.g.  1112926393 +0200
RFC 2822            = e.g. Thu, 07 Apr 2005 22:13:13 +0200
ISO 8601            = e.g. 2005-04-07T22:13:13

The only command that writes a new commit during normal use is git commit. It also has a --date option that lets you directly specify the author date. Your anticipated usage includes git filter-branch --env-filter also uses the environment variables mentioned above (these are part of the “env” after which the option is named; see “Options” in git-filter-branch(1) and the underlying “plumbing” command git-commit-tree(1).

Inserting a File Into a Single ref History

If your repository is very simple (i.e. you only have a single branch, no tags), then you can probably use git rebase to do the work.

In the following commands, use the object name (SHA-1 hash) of the commit instead of “A”. Do not forget to use one of the “date override” methods when you run git commit.

---A---B---C---o---o---o   master

git checkout master
git checkout A~0
git add path/to/file
git commit --date='whenever'
git tag ,new-commit -m'delete me later'
git checkout -
git rebase --onto ,new-commit A
git tag -d ,new-commit

---A---N                      (was ",new-commit", but we delete the tag)
         B'---C'---o---o---o   master

If you wanted to update A to include the new file (instead of creating a new commit where it was added), then use git commit --amend instead of git commit. The result would look like this:

---A'---B'---C'---o---o---o   master

The above works as long as you can name the commit that should be the parent of your new commit. If you actually want your new file to be added via a new root commit (no parents), then you need something a bit different:

B---C---o---o---o   master

git checkout master
git checkout --orphan new-root
git rm -rf .
git add path/to/file
GIT_AUTHOR_DATE='whenever' git commit
git checkout -
git rebase --root --onto new-root
git branch -d new-root

N                       (was new-root, but we deleted it)
  B'---C'---o---o---o   master

git checkout --orphan is relatively new (Git 1.7.2), but there are other ways of doing the same thing that work on older versions of Git.

Inserting a File Into a Multi-ref History

If your repository is more complex (i.e. it has more than one ref (branches, tags, etc.)), then you will probably need to use git filter-branch. Before using git filter-branch, you should make a backup copy of your entire repository. A simple tar archive of your entire working tree (including the .git directory) is sufficient. git filter-branch does make backup refs, but it is often easier to recover from a not-quite-right filtering by just deleting your .git directory and restoring it from your backup.

Note: The examples below use the lower-level command git update-index --add instead of git add. You could use git add, but you would first need to copy the file from some external location to the expected path (--index-filter runs its command in a temporary GIT_WORK_TREE that is empty).

If you want your new file to be added to every existing commit, then you can do this:

new_file=$(git hash-object -w path/to/file)
git filter-branch \
  --index-filter \
    'git update-index --add --cacheinfo 100644 '"$new_file"' path/to/file' \
  --tag-name-filter cat \
  -- --all
git reset --hard

I do not really see any reason to change the dates of the existing commits with --env-filter 'GIT_AUTHOR_DATE=…'. If you did use it, you would have make it conditional so that it would rewrite the date for every commit.

If you want your new file to appear only in the commits after some existing commit (“A”), then you can do this:

before_commit=$(git rev-parse --verify A)
file_blob=$(git hash-object -w "$file_path")
git filter-branch \
  --index-filter '

    if x=$(git rev-list -1 "$GIT_COMMIT" --not '"$before_commit"') &&
       test -n "$x"; then
         git update-index --add --cacheinfo 100644 '"$file_blob $file_path"'

  ' \
  --tag-name-filter cat \
  -- --all
git reset --hard

If you want the file to be added via a new commit that is to be inserted into the middle of your history, then you will need to generate the new commit prior to using git filter-branch and add --parent-filter to git filter-branch:

before_commit=$(git rev-parse --verify A)

git checkout master
git checkout "$before_commit"
git add "$file_path"
git commit --date='whenever'
new_commit=$(git rev-parse --verify HEAD)
file_blob=$(git rev-parse --verify HEAD:"$file_path")
git checkout -

git filter-branch \
  --parent-filter "sed -e s/$before_commit/$new_commit/g" \
  --index-filter '

    if x=$(git rev-list -1 "$GIT_COMMIT" --not '"$new_commit"') &&
       test -n "$x"; then
         git update-index --add --cacheinfo 100644 '"$file_blob $file_path"'

  ' \
  --tag-name-filter cat \
  -- --all
git reset --hard

You could also arrange for the file to be first added in a new root commit: create your new root commit via the “orphan” method from the git rebase section (capture it in new_commit), use the unconditional --index-filter, and a --parent-filter like "sed -e \"s/^$/-p $new_commit/\"".

'dependencies.dependency.version' is missing error, but version is managed in parent

Make sure the value in the child's project/parent/version node matches its parent's project/version value

Java Inheritance - calling superclass method

It is possible to use super to call the method from mother class, but this would mean you probably have a design problem. Maybe B.alphaMethod1() shouldn't override A's method and be called B.betaMethod1().

If it depends on the situation, you can put some code logic like :

public void alphaMethod1(){
    if (something) {
    // Rest of the code for other situations

Like this it will only call A's method when needed and will remain invisible for the class user.

Writing to CSV with Python adds blank lines

If you're using Python 2.x on Windows you need to change your line open('test.csv', 'w') to open('test.csv', 'wb'). That is you should open the file as a binary file.

However, as stated by others, the file interface has changed in Python 3.x.

How to get child element by index in Jquery?


What is IPV6 for localhost and

For use in a /etc/hosts file as a simple ad blocking technique to cause a domain to fail to resolve, the address has been widely used because it causes the request to immediately fail without even trying, because it's not a valid or routable address. This is in comparison to using in that place, where it will at least check to see if your own computer is listening on the requested port 80 before failing with 'connection refused.' Either of those addresses being used in the hosts file for the domain will stop any requests from being attempted over the actual network, but has gained favor because it's more 'optimal' for the above reason. "127" IPs will attempt to hit your own computer, and any other IP will cause a request to be sent to the router to try to route it, but for there's nowhere to even send a request to.

All that being said, having any IP listed in your hosts file for the domain to be blocked is sufficient, and you wouldn't need or want to also put an ipv6 address in your hosts file unless -- possibly -- you don't have ipv4 enabled at all. I'd be really surprised if that was the case, though. And still though, I think having the host appear in /etc/hosts with a bad ipv4 address when you don't have ipv4 enabled would still give you the result you are looking for which is for it to fail, instead of looking up the real DNS of say, and getting back either a v4 or v6 IP.

Convert all data frame character columns to factors

The easiest way would be to use the code given below. It would automate the whole process of converting all the variables as factors in a dataframe in R. it worked perfectly fine for me. food_cat here is the dataset which I am using. Change it to the one which you are working on.

    for(i in 1:ncol(food_cat)){

food_cat[,i] <- as.factor(food_cat[,i])


Traverse a list in reverse order in Python

the reverse function comes in handy here:

myArray = [1,2,3,4]
for x in myArray:
    print x

How to pass an array to a function in VBA?

Your function worked for me after changing its declaration to this ...

Function processArr(Arr As Variant) As String

You could also consider a ParamArray like this ...

Function processArr(ParamArray Arr() As Variant) As String
    'Dim N As Variant
    Dim N As Long
    Dim finalStr As String
    For N = LBound(Arr) To UBound(Arr)
        finalStr = finalStr & Arr(N)
    Next N
    processArr = finalStr
End Function

And then call the function like this ...

processArr("foo", "bar")

Compiling problems: cannot find crt1.o

This worked for me with Ubuntu 16.04

$ LIBRARY_PATH=/usr/lib/x86_64-linux-gnu

How to only find files in a given directory, and ignore subdirectories using bash

find /dev -maxdepth 1 -name 'abc-*'

Does not work for me. It return nothing. If I just do '.' it gives me all the files in directory below the one I'm working in on.

find /dev -maxdepth 1 -name "*.root" -type 'f' -size +100k -ls

Return nothing with '.' instead I get list of all 'big' files in my directory as well as the rootfiles/ directory where I store old ones.

Continuing. This works.

find ./ -maxdepth 1 -name "*.root" -type 'f' -size +100k -ls
564751   71 -rw-r--r--   1 snyder   bfactory   115739 May 21 12:39 ./R24eTightPiPi771052-55.root
565197  105 -rw-r--r--   1 snyder   bfactory   150719 May 21 14:27 ./R24eTightPiPi771106-2.root
565023   94 -rw-r--r--   1 snyder   bfactory   134180 May 21 12:59 ./R24eTightPiPi77999-109.root
719678   82 -rw-r--r--   1 snyder   bfactory   121149 May 21 12:42 ./R24eTightPiPi771098-10.root
564029  140 -rw-r--r--   1 snyder   bfactory   170181 May 21 14:14 ./combo77v.root

Apparently /dev means directory of interest. But ./ is needed, not just .. The need for the / was not obvious even after I figured out what /dev meant more or less.

I couldn't respond as a comment because I have no 'reputation'.

Using if-else in JSP

You may try this example:

  <h1>Hello! I'm duke! What's you name?</h1>_x000D_
  <input type="text" name="user">_x000D_
  <input type="submit" value="submit">&nbsp;&nbsp;&nbsp;&nbsp;_x000D_
  <input type="reset">_x000D_
<h1>Hello ${param.user}</h1> _x000D_
<!-- its Expression Language -->

How to setup virtual environment for Python in VS Code?

With a newer VS Code version it's quite simple.

Open VS Code in your project's folder.

Then open Python Terminal (Ctrl-Shift-P: Python: Create Terminal)

In the terminal:

python -m venv .venv

you'll then see the following dialog: enter image description here

click Yes

Then Python: Select Interpreter (via Ctrl-Shift-P)

and select the option (in my case towards the bottom)

Python 3.7 (venv) ./venv/Scripts/python.exe

If you see

Activate.ps1 is not digitally signed. You cannot run this script on the current system.

you'll need to do the following:

For more information see:

Browser back button handling

You can also add hash when page is loading:

location.hash = "noBack";

Then just handle location hash change to add another hash:

$(window).on('hashchange', function() {
    location.hash = "noBack";

That makes hash always present and back button tries to remove hash at first. Hash is then added again by "hashchange" handler - so page would never actually can be changed to previous one.

How do I handle a click anywhere in the page, even when a certain element stops the propagation?

document.body.addEventListener("keyup", function(event) {
  if (event.keyCode === 13) {
  console.log('clicked ;)');


jQuery how to find an element based on a data-attribute value?

You have to inject the value of current into an Attribute Equals selector:


For older JavaScript environments (ES5 and earlier):

$("ul").find("[data-slide='" + current + "']"); 

A fatal error has been detected by the Java Runtime Environment: SIGSEGV, libjvm

Here is your relief for the problem :

I have a problem of running different versions of STS this morning, the application crash with the similar way as the question did.

Excerpt of my log file.

A fatal error has been detected by the Java Runtime Environment:
#  SIGSEGV (0xb) at pc=0x00007f459db082a1, pid=4577, tid=139939015632640
# JRE version: 6.0_30-b12
# Java VM: Java HotSpot(TM) 64-Bit Server VM 
(20.5-b03 mixed mode linux-amd64 compressed oops)
# Problematic frame:
# C  []  short+0x11

note that exception occured at # C [] short+0x11

Okay then little below the line:

R9 =0x00007f461829e550: <offset 0xa85550> in /usr/share/java/jdk1.6.0_30/jre/lib/amd64/server/ at 0x00007f4617819000
R10=0x00007f461750f7c0 is pointing into the stack for thread: 0x00007f4610008000
R11=0x00007f459db08290: soup_session_feature_detach+0 in /usr/lib/x86_64-linux-gnu/ at 0x00007f459da9c000
R12=0x0000000000000000 is an unknown value
R13=0x000000074404c840 is an oop

This line tells you where the actual bug or crash is to investigate more on this crash issue please use below links to see more, but let's continue the crash investigation and how I resolved it and the novelty of this bug :)

links are :



Okay, after that here's what I found out to casue this case and why it happens as general advise.

  1. Most of the time, check that if you have installed, updated recently on Ubunu and Windows there are libraries like libsoup in linux which were the casuse of my crash.

  2. Check also for a new hardware problem and try to investigate the Logfile which STS or Java generated and also syslog in linux by

    tail - f /var/lib/messages or some other file

Then by carfully looking at those files the one you have the crash log for ... you can really solve the issue as follows:

sudo unlink /usr/lib/i386-linux-gnu/


sudo unlink /usr/lib/x86_64-linux-gnu/

Done !! Cheers!!

Adding two Java 8 streams, or an extra element to a stream

You can use Guava's Streams.concat(Stream<? extends T>... streams) method, which will be very short with static imports:

Stream stream = concat(stream1, stream2, of(element));

When restoring a backup, how do I disconnect all active connections?

I prefer to do like this,

alter database set offline with rollback immediate

and then restore your database. after that,

alter database set online with rollback immediate

MVC If statement in View

Every time you use html syntax you have to start the next razor statement with a @. So it should be @if ....

What is a good pattern for using a Global Mutex in C#?

A solution (for WPF) without WaitOne because it can cause an AbandonedMutexException. This solution uses the Mutex constructor that returns the createdNew boolean to check if the mutex is already created. It also uses the GetType().GUID so renaming an executable doesn't allow multiple instances.

Global vs local mutex see note in:

private Mutex mutex;
private bool mutexCreated;

public App()
    string mutexId = $"Global\\{GetType().GUID}";
    mutex = new Mutex(true, mutexId, out mutexCreated);

protected override void OnStartup(StartupEventArgs e)
    if (!mutexCreated)
        MessageBox.Show("Already started!");

Because Mutex implements IDisposable it is released automatically but for completeness call dispose:

protected override void OnExit(ExitEventArgs e)

Move everything into a base class and add the allowEveryoneRule from the accepted answer. Also added ReleaseMutex though it doesn't look like it's really needed because it is released automatically by the OS (what if the application crashes and never calls ReleaseMutex would you need to reboot?).

public class SingleApplication : Application
    private Mutex mutex;
    private bool mutexCreated;

    public SingleApplication()
        string mutexId = $"Global\\{GetType().GUID}";

        MutexAccessRule allowEveryoneRule = new MutexAccessRule(
            new SecurityIdentifier(WellKnownSidType.WorldSid, null),
        MutexSecurity securitySettings = new MutexSecurity();

        // initiallyOwned: true == false + mutex.WaitOne()
        mutex = new Mutex(initiallyOwned: true, mutexId, out mutexCreated, securitySettings);        

    protected override void OnExit(ExitEventArgs e)
        if (mutexCreated)
            catch (ApplicationException ex)
                MessageBox.Show(ex.Message, ex.GetType().FullName, MessageBoxButton.OK, MessageBoxImage.Error);

    protected override void OnStartup(StartupEventArgs e)
        if (!mutexCreated)
            MessageBox.Show("Already started!");

Sending Windows key using SendKeys

download InputSimulator from nuget package.

then write this:

        var simu = new InputSimulator();
        simu.Keyboard.ModifiedKeyStroke(VirtualKeyCode.LWIN, VirtualKeyCode.VK_E);

in my case to create new vertial desktop, 3 keys needed and code like this(windows key + ctrl + D):

        simu.Keyboard.ModifiedKeyStroke(new[] { VirtualKeyCode.LWIN, VirtualKeyCode.CONTROL }, VirtualKeyCode.VK_D);

Make var_dump look pretty

function var_view($var)

    ini_set("highlight.keyword", "#a50000;  font-weight: bolder");
    ini_set("highlight.string", "#5825b6; font-weight: lighter; ");

    highlight_string("<?php\n" . var_export($var, true) . "?>");
    $highlighted_output = ob_get_clean();

    $highlighted_output = str_replace( ["&lt;?php","?&gt;"] , '', $highlighted_output );

    echo $highlighted_output;

Removing duplicate rows from table in Oracle


Simple PowerShell LastWriteTime compare

I can't fault any of the answers here for the OP accepted one of them as resolving their problem. However, I found them flawed in one respect. When you output the result of the assignment to the variable, it contains numerous blank lines, not just the sought after answer. Example:

PS C:\brh> [datetime](Get-ItemProperty -Path .\deploy.ps1 -Name LastWriteTime).LastWriteTime

Friday, December 12, 2014 2:33:09 PM

PS C:\brh> 

I'm a fan of two things in code, succinctness and correctness. brianary has the right of it for succinctness with a tip of the hat to Roger Lipscombe but both miss correctness due to the extra lines in the result. Here's what I think the OP was looking for since it's what got me over the finish line.

PS C:\brh> (ls .\deploy.ps1).LastWriteTime.DateTime
Friday, December 12, 2014 2:33:09 PM

PS C:\brh> 

Note the lack of extra lines, only the one that PowerShell uses to separate prompts. Now this can be assigned to a variable for comparison or, as in my case, stored in a file for reading and comparison in a later session.

Fragments within Fragments

If you find your nested fragment not being removed or being duplicated (eg. on Activity restart, on screen rotate) try changing:

transaction.add(, newFragment);


transaction.replace(, newFragment);

If above doesn't help, try:

Fragment f = getChildFragmentManager().findFragmentById(;

FragmentTransaction transaction = getChildFragmentManager().beginTransaction();

if (f == null) {
    Log.d(TAG, "onCreateView: fragment doesn't exist");
    newFragment= new MyFragmentType();
    transaction.add(, newFragment);
} else {
    Log.d(TAG, "onCreateView: fragment already exists");
    transaction.replace(, f);

Learnt here

How to auto-remove trailing whitespace in Eclipse?

  1. Removing whitespace from the entire file being edited:

Preferences -> Java -> Editors -> Save Actions -> check Perform the selected actions on save -> check Additional actions -> click Configure.. -> go to Code organizing tab -> check Remove trailing whitespace -> select All lines.

  1. Removing whitespace only from the lines I changed:

Preferences -> Java -> Editor -> Save Actions -> check "Perform the selected actions on save -> check Format source code -> select Format edited lines.

Note it is not necessary to click Configure the formatter settings on the Formatter page - all the code styles automatically include removing trailing whitespace. At least I couldn't find a setting for this in Formatter configuration, and it worked out of the box for built-in Java Conventions, Eclipse, Eclipse 2.1 styles, as well as GoogleStyle.

When using this set-up, you obviously need to also turn off the solution to part 1 of the question.

Eclipse version checked: 4.5.2, 4.11

How to remove a field completely from a MongoDB document?

Because I kept finding this page when looking for a way to remove a field using MongoEngine, I guess it might be helpful to post the MongoEngine way here too:


Spring CORS No 'Access-Control-Allow-Origin' header is present

as @Geoffrey pointed out, with spring security, you need a different approach as described here: Spring Boot Security CORS

How to get the currently logged in user's user id in Django?

Assuming you are referring to Django's Auth User, in your view:

def game(request):
  user = request.user

  gta = Game.objects.create(name="gta", owner=user)

View list of all JavaScript variables in Google Chrome Console

Updated method from same article Avindra mentioned — injects iframe and compare its contentWindow properties to global window properties.

(function() {_x000D_
  var iframe = document.createElement('iframe');_x000D_
  iframe.onload = function() {_x000D_
    var iframeKeys = Object.keys(iframe.contentWindow);_x000D_
    Object.keys(window).forEach(function(key) {_x000D_
      if(!(iframeKeys.indexOf(key) > -1)) {_x000D_
  iframe.src = 'about:blank';_x000D_

How do I install PHP cURL on Linux Debian?

I wrote an article on topis how to [manually install curl on debian linu][1]x.

[1]: This is its shortcut:

  1. cd /usr/local/src
  2. wget
  3. tar -xvzf curl-7.36.0.tar.gz
  4. rm *.gz
  5. cd curl-7.6.0
  6. ./configure
  7. make
  8. make install

And restart Apache. If you will have an error during point 6, try to run apt-get install build-essential.

How to fix symbol lookup error: undefined symbol errors in a cluster environment

After two dozens of comments to understand the situation, it was found that the was actually a symlink (with several levels of indirection) to a file that was not shared between the queued processes and the interactive processes. This means even though the symlink itself lies on a shared filesystem, the contents of the file do not and as a result the process was seeing different versions of the library.

For future reference: other than checking LD_LIBRARY_PATH, it's always a good idea to check a library with nm -D to see if the symbols actually exist. In this case it was found that they do exist in interactive mode but not when run in the queue. A quick md5sum revealed that the files were actually different.

MVC3 DropDownListFor - a simple example?

For binding Dynamic Data in a DropDownList you can do the following:

Create ViewBag in Controller like below

ViewBag.ContribTypeOptions = yourFunctionValue();

now use this value in view like below:

@Html.DropDownListFor(m => m.ContribType, 
    new SelectList(@ViewBag.ContribTypeOptions, "ContribId", 
                   "Value", Model.ContribTypeOptions.First().ContribId), 
    "Select, please")

How to close a Java Swing application from the code



Crude, but effective.

VBA Excel sort range by specific column

Try this code:

Dim lastrow As Long
lastrow = Cells(Rows.Count, 2).End(xlUp).Row
Range("A3:D" & lastrow).Sort key1:=Range("B3:B" & lastrow), _
   order1:=xlAscending, Header:=xlNo

Call PowerShell script PS1 from another PS1 script inside Powershell ISE

How do you run PowerShell built-in scripts inside of your scripts?

How do you use built-in scripts like


Those are ran by your computer, automatically checking the path of the script.

Similarly, I can run my custom scripts by just putting the name of the script in the script-block

::sid.ps1 is a PS script I made to find the SID of any user
::it takes one argument, that argument would be the username
echo $(sid.ps1 jowers)

(returns something like)> S-X-X-XXXXXXXX-XXXXXXXXXX-XXX-XXXX

$(sid.ps1 jowers).Replace("S","X")

(returns same as above but with X instead of S)

Go on to the powershell command line and type

> $profile

This will return the path to a file that our PowerShell command line will execute every time you open the app.

It will look like this


Go to Documents and see if you already have a WindowsPowerShell directory. I didn't, so

> cd \Users\jowers\Documents
> mkdir WindowsPowerShell
> cd WindowsPowerShell
> type file > Microsoft.PowerShellISE_profile.ps1

We've now created the script that will launch every time we open the PowerShell App.

The reason we did that was so that we could add our own folder that holds all of our custom scripts. Let's create that folder and I'll name it "Bin" after the directories that Mac/Linux hold its scripts in.

> mkdir \Users\jowers\Bin

Now we want that directory to be added to our $env:path variable every time we open the app so go back to the WindowsPowerShell Directory and

> start Microsoft.PowerShellISE_profile.ps1

Then add this

$env:path += ";\Users\jowers\Bin"

Now the shell will automatically find your commands, as long as you save your scripts in that "Bin" directory.

Relaunch the powershell and it should be one of the first scripts that execute.

Run this on the command line after reloading to see your new directory in your path variable:

> $env:Path

Now we can call our scripts from the command line or from within another script as simply as this:

$(customScript.ps1 arg1 arg2 ...)

As you see we must call them with the .ps1 extension until we make aliases for them. If we want to get fancy.

C++ obtaining milliseconds time on Linux -- clock() doesn't seem to work properly

Please note that clock does not measure wall clock time. That means if your program takes 5 seconds, clock will not measure 5 seconds necessarily, but could more (your program could run multiple threads and so could consume more CPU than real time) or less. It measures an approximation of CPU time used. To see the difference consider this code

#include <iostream>
#include <ctime>
#include <unistd.h>

int main() {
    std::clock_t a = std::clock();
    sleep(5); // sleep 5s
    std::clock_t b = std::clock();

    std::cout << "difference: " << (b - a) << std::endl;
    return 0;

It outputs on my system

$ difference: 0

Because all we did was sleeping and not using any CPU time! However, using gettimeofday we get what we want (?)

#include <iostream>
#include <ctime>
#include <unistd.h>
#include <sys/time.h>

int main() {
    timeval a;
    timeval b;

    gettimeofday(&a, 0);
    sleep(5); // sleep 5s
    gettimeofday(&b, 0);

    std::cout << "difference: " << (b.tv_sec - a.tv_sec) << std::endl;
    return 0;

Outputs on my system

$ difference: 5

If you need more precision but want to get CPU time, then you can consider using the getrusage function.

Dynamically adding properties to an ExpandoObject

As explained here by Filip -

You can add a method too at runtime.

x.Add("Shout", new Action(() => { Console.WriteLine("Hellooo!!!"); }));

Java - Getting Data from MySQL database

Easy Java method to get data from MySQL table:


String Data(String query){
    String get=null;

Connection con = (Connection)DriverManager.getConnection
Statement stmt = (Statement) con.createStatement();
ResultSet rs=stmt.executeQuery(query);
if (
get = rs.getString("");

catch(Exception e){
JOptionPane.showMessageDialog (this, e.getMessage());
    return get;

Absolute and Flexbox in React Native

Ok, solved my problem, if anyone is passing by here is the answer:

Just had to add left: 0, and top: 0, to the styles, and yes, I'm tired.

position: 'absolute',
left:     0,
top:      0,

how to bold words within a paragraph in HTML/CSS?

Although your answer has many solutions I think this is a great way to save lines of code. Try using spans which is great for situations like yours.

  1. Create a class for making any item bold. So for paragraph text it would be
span.bold(This name can be anything do not include parenthesis) {
   font-weight: bold;
  1. In your html you can access that class like by using the span tags and adding a class of bold or whatever name you have chosen

How to specify preference of library path?

This is an old question, but no one seems to have mentioned this.

You were getting lucky that the thing was linking at all.

You needed to change

g++ -g -Wall -o my_binary -L/my/dir -lfoo bar.cpp

to this:

g++ -g -Wall -o my_binary -L/my/dir bar.cpp -lfoo

Your linker keeps track of symbols it needs to resolve. If it reads the library first, it doesn't have any needed symbols, so it ignores the symbols in it. Specify the libraries after the things that need to link to them so that your linker has symbols to find in them.

Also, -lfoo makes it search specifically for a file named libfoo.a or as needed. Not So either ln the name or rename the library as appopriate.

To quote the gcc man page:

-l library
   It makes a difference where in the command you 
   write this option; the linker searches and processes 
   libraries and object files in the order they are 
   specified.  Thus, foo.o -lz bar.o searches library z 
   after file foo.o but before bar.o.  If bar.o refers 
   to functions in z, those functions may not be loaded.

Adding the file directly to g++'s command line should have worked, unless of course, you put it prior to bar.cpp, causing the linker to ignore it for lacking any needed symbols, because no symbols were needed yet.

reading external sql script in python

according me, it is not possible


  1. import .sql file on mysql server

  2. after

    import mysql.connector
    import pandas as pd

    and then you use .sql file by convert to dataframe

Xamarin.Forms ListView: Set the highlight color of a tapped item

It looks like there is actually a cross-platform way to do this that works on both iOS and Android (not sure about Windows). It uses only binding and does not require custom renderers (which seems rare). This is a mash-up of lots of googling, so thanks to anyone who I may have borrowed from...

I am assuming ViewCells, but this should work for Text or Image cells as well. I am only including the relevant code here beyond the typical text, image, etc.

On your page do something like this:

MyModel model1 = new MyModel();
MyModel model2 = new MyModel();

ListView list = new ListView
    ItemsSource = new List<MyModel> { model1, model2 };
    ItemTemplate = new DataTemplate( typeof(MyCell) )

Your custom Model might look something like this:

public class MyModel : INotifyPropertyChanged
    public event PropertyChangedEventHandler PropertyChanged;

    private Color _backgroundColor;

    public Color BackgroundColor 
        get { return _backgroundColor; } 
            _backgroundColor = value; 

            if ( PropertyChanged != null )
                PropertyChanged( this, new PropertyChangedEventArgs( "BackgroundColor" ) );

    public void SetColors( bool isSelected )
        if ( isSelected )
            BackgroundColor = Color.FromRgb( 0.20, 0.20, 1.0 );
            BackgroundColor = Color.FromRgb( 0.95, 0.95, 0.95 ); 

Then for your ItemTemplate you need a custom cell class something like this:

public class MyCell : ViewCell
    public MyCell() : base()
        RelativeLayout layout = new RelativeLayout();
        layout.SetBinding( Layout.BackgroundColorProperty, new Binding( "BackgroundColor" ) );

        View = layout;

Then in your ItemSelected event handler, do the following. Note that 'selected' is an instance of MyModel used to track the currently selected item. I am only showing background color here, but I also use this technique to reverse highlight the text and detail text colors.

private void ItemSelected( object sender, ItemTappedEventArgs args )
    // Deselect previous
    if ( selected != null )
        selected.SetColors( false );

    // Select new
    selected = (list.SelectedItem as MyModel);
    selected.SetColors( true );

how to fix EXE4J_JAVA_HOME, No JVM could be found on your system error?

There are few steps to overcome this problem:

  1. Uninstall Java related softwares
  2. Uninstall NodeJS if installed
  3. Download java 8 update161
  4. Install it

The problem solved: The problem raised to me at the uninstallation on openfire server.

Specifying and saving a figure with exact size in pixels

Matplotlib doesn't work with pixels directly, but rather physical sizes and DPI. If you want to display a figure with a certain pixel size, you need to know the DPI of your monitor. For example this link will detect that for you.

If you have an image of 3841x7195 pixels it is unlikely that you monitor will be that large, so you won't be able to show a figure of that size (matplotlib requires the figure to fit in the screen, if you ask for a size too large it will shrink to the screen size). Let's imagine you want an 800x800 pixel image just for an example. Here's how to show an 800x800 pixel image in my monitor (my_dpi=96):

plt.figure(figsize=(800/my_dpi, 800/my_dpi), dpi=my_dpi)

So you basically just divide the dimensions in inches by your DPI.

If you want to save a figure of a specific size, then it is a different matter. Screen DPIs are not so important anymore (unless you ask for a figure that won't fit in the screen). Using the same example of the 800x800 pixel figure, we can save it in different resolutions using the dpi keyword of savefig. To save it in the same resolution as the screen just use the same dpi:

plt.savefig('my_fig.png', dpi=my_dpi)

To to save it as an 8000x8000 pixel image, use a dpi 10 times larger:

plt.savefig('my_fig.png', dpi=my_dpi * 10)

Note that the setting of the DPI is not supported by all backends. Here, the PNG backend is used, but the pdf and ps backends will implement the size differently. Also, changing the DPI and sizes will also affect things like fontsize. A larger DPI will keep the same relative sizes of fonts and elements, but if you want smaller fonts for a larger figure you need to increase the physical size instead of the DPI.

Getting back to your example, if you want to save a image with 3841 x 7195 pixels, you could do the following:

plt.figure(figsize=(3.841, 7.195), dpi=100)
( your code ...)
plt.savefig('myfig.png', dpi=1000)

Note that I used the figure dpi of 100 to fit in most screens, but saved with dpi=1000 to achieve the required resolution. In my system this produces a png with 3840x7190 pixels -- it seems that the DPI saved is always 0.02 pixels/inch smaller than the selected value, which will have a (small) effect on large image sizes. Some more discussion of this here.

case statement in where clause - SQL Server

A CASE statement is an expression, just like a boolean comparison. That means the 'AND' needs to go before the 'CASE' statement, not within it.:

Select * From Times
WHERE (StartDate <= @Date) AND (EndDate >= @Date)

AND -- Added the "AND" here

CASE WHEN @day = 'Monday' THEN (Monday = 1)   -- Removed "AND" 
    WHEN @day = 'Tuesday' THEN (Tuesday = 1)  -- Removed "AND" 
    ELSE AND (Wednesday = 1) 

How to add comments into a Xaml file in WPF?

For anyone learning this stuff, comments are more important, so drawing on Xak Tacit's idea
(from User500099's link) for Single Property comments, add this to the top of the XAML code block:

<!--Comments Allowed With Markup Compatibility (mc) In XAML!
    Usage in property:
ØignoreØ:AttributeToIgnore="Text Of AttributeToIgnore"-->

Then in the code block

<Application FooApp:Class="Foo.App"



Determine if map contains a value for a key?

amap.find returns amap::end when it does not find what you're looking for -- you're supposed to check for that.

Convert hex string to int in Python

with '0x' prefix, you might also use eval function

For example


Change class on mouseover in directive

In general I fully agree with Jason's use of css selector, but in some cases you may not want to change the css, e.g. when using a 3rd party css-template, and rather prefer to add/remove a class on the element.

The following sample shows a simple way of adding/removing a class on ng-mouseenter/mouseleave:

<div ng-app>
    ng-class="{red: hover}"
    ng-init="hover = false"
    ng-mouseenter="hover = true"
    ng-mouseleave="hover = false">
      Test 1 2 3.

with some styling:

.red {
  background-color: red;

.italic {
  font-style: italic;
  color: black;

See running example here: jsfiddle sample

Styling on hovering is a view concern. Although the solution above sets a "hover" property in the current scope, the controller does not need to be concerned about this.

Check if a Postgres JSON array contains a string

Not smarter but simpler:

select info->>'name' from rabbits WHERE info->>'food' LIKE '%"carrots"%';

Center content in responsive bootstrap navbar

this should work

 .navbar-nav {
    position: absolute;
    left: 50%;
    transform: translatex(-50%);

How to make an anchor tag refer to nothing?

I know this is an old question, but I thought I'd add my two cents anyway:

It depends on what the link is going to do, but usually, I would be pointing the link at a url that could possibly be displaying/doing the same thing, for example, if you're making a little about box pop up:

<a id="about" href="/about">About</a>

Then with jQuery

$('#about').click(function(e) {

This way, very old browsers (or browsers with JavaScript disabled) can still navigate to a separate about page, but more importantly, Google will also pick this up and crawl the contents of the about page.

Command to get nth line of STDOUT

From sed1line:

# print line number 52
sed -n '52p'                 # method 1
sed '52!d'                   # method 2
sed '52q;d'                  # method 3, efficient on large files

From awk1line:

# print line number 52
awk 'NR==52'
awk 'NR==52 {print;exit}'          # more efficient on large files

Numpy where function multiple conditions

I have worked out this simple example

import numpy as np

ar = np.array([3,4,5,14,2,4,3,7])

print [X for X in list(ar) if (X >= 3 and X <= 6)]

[3, 4, 5, 4, 3]

Select all elements with a "data-xxx" attribute without using jQuery


will get you all elements with that attribute.


will only get you ones with a value of 1.

How can I remove item from querystring in using c#?

Get the querystring collection, parse it into a (name=value pair) string, excluding the one you want to REMOVE, and name it newQueryString

Then call Response.Redirect(known_path?newqueryString);

The HTTP request is unauthorized with client authentication scheme 'Ntlm' The authentication header received from the server was 'NTLM'

If I recall correctly, there are some issues with adding SharePoint web services as a VS2K8 "Service Reference". You need to add it as an old-style "Web Reference" to work properly.

Bootstrap 3: pull-right for col-lg only

now include bootstrap 4:

@import url('');

and code should be like this:

<div class="row">
    <div class="col-lg-6 col-md-6" style="border:solid 1px red">elements 1</div>
    <div class="col-lg-6 col-md-6" style="border:solid 1px red">
         <div class="pull-lg-right pull-xl-right">
            elements 2

Best way to track onchange as-you-type in input type="text"?

Below code works fine for me with Jquery 1.8.3

HTML : <input type="text" id="myId" />


$("#myId").on('change keydown paste input', function(){

Convert generic List/Enumerable to DataTable?

A small change to Marc's answer to make it work with value types like List<string> to data table:

public static DataTable ListToDataTable<T>(IList<T> data)
    DataTable table = new DataTable();

    //special handling for value types and string
    if (typeof(T).IsValueType || typeof(T).Equals(typeof(string)))

        DataColumn dc = new DataColumn("Value", typeof(T));
        foreach (T item in data)
            DataRow dr = table.NewRow();
            dr[0] = item;
        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(typeof(T));
        foreach (PropertyDescriptor prop in properties)
            table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
        foreach (T item in data)
            DataRow row = table.NewRow();
            foreach (PropertyDescriptor prop in properties)
                    row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;
                catch (Exception ex)
                    row[prop.Name] = DBNull.Value;
    return table;

AJAX jQuery refresh div every 5 seconds

Try this out.

function loadlink(){
    $('#links').load('test.php',function () {

loadlink(); // This will run on page load
    loadlink() // this will run after every 5 seconds
}, 5000);

Hope this helps.

Use Device Login on Smart TV / Console

Implement Login for Devices

Facebook Login for Devices is for devices that directly make HTTP calls over the internet. The following are the API calls and responses your device can make.

1. Enable Login for Devices

Change Settings > Advanced > OAuth Settings > Login from Devices to 'Yes'.

2. Generate a Code which is required for facebook device identification

When the person clicks Log in with Facebook, you device should make an HTTP POST to:

       &amp;scope=<COMMA_SEPARATED_PERMISSION_NAMES> // e.g.public_profile,user_likes

The response comes in this form:

  "code": "92a2b2e351f2b0b3503b2de251132f47",
  "user_code": "A1NWZ9",
  "verification_uri": "",
  "expires_in": 420,
  "interval": 5

This response means:

  • Display the string “A1NWZ9” on your device
  • Tell the person to go to “” and enter this code
  • The code expires in 420 seconds. You should cancel the login flow after that time if you do not receive an access token
  • Your device should poll the Device Login API every 5 seconds to see if the authorization has been successful

3. Display the Code

Your device should display the user_code and tell people to visit the verification_uri such as on their PC or smartphone. See the Design Guidelines.

4. Poll for Authorization

Your device should poll the Device Login API to see if the person successfully authorized your application. You should do this at the interval in the response to your call in Step 1, which is every 5 seconds. Your device should poll to:

       &amp;code=<LONG_CODE_FROM_STEP_1> //e.g."92a2b2e351f2b0b3503b2de251132f47"

You will get 200 HTTP code i.e User has successfully authorized the device. The device can now use the access_token value to make authenticated API calls.

5. Confirm Successful Login

Your device should display their name and if available, a profile picture until they click Continue. To get the person's name and profile picture, your device should make a standard Graph API call:



  "name": "John Doe", 
  "picture": {
    "data": {
      "is_silhouette": false, 
      "url": ""
  "id": "2023462875238472"

6. Store Access Tokens

Your device should persist the access token to make other requests to the Graph API.

Device Login access tokens may be valid for up to 60 days but may be invalided in a number of scenarios. For example when a person changes their Facebook password their access token is invalidated.

If the token is invalid, your device should delete the token from its memory. The person using your device needs to perform the Device Login flow again from Step 1 to retrieve a new, valid token.

Argument of type 'X' is not assignable to parameter of type 'X'

For what it worth, if anyone has this problem only in VSCode, just restart VSCode and it should fix it. Sometimes, Intellisense seems to mess up with imports or types.

Related to Typescript: Argument of type 'RegExpMatchArray' is not assignable to parameter of type 'string'

adding multiple entries to a HashMap at once in one statement

You can use Google Guava's ImmutableMap. This works as long as you don't care about modifying the Map later (you can't call .put() on the map after constructing it using this method):


// For up to five entries, use .of()
Map<String, Integer> littleMap = ImmutableMap.of(
    "One", Integer.valueOf(1),
    "Two", Integer.valueOf(2),
    "Three", Integer.valueOf(3)

// For more than five entries, use .builder()
Map<String, Integer> bigMap = ImmutableMap.<String, Integer>builder()
    .put("One", Integer.valueOf(1))
    .put("Two", Integer.valueOf(2))
    .put("Three", Integer.valueOf(3))
    .put("Four", Integer.valueOf(4))
    .put("Five", Integer.valueOf(5))
    .put("Six", Integer.valueOf(6))

See also:

A somewhat related question: ImmutableMap.of() workaround for HashMap in Maps?

How do I use Notepad++ (or other) with msysgit?

Update 2010-2011:

zumalifeguard's solution (upvoted) is simpler than the original one, as it doesn't need anymore a shell wrapper script.

As I explain in "How can I set up an editor to work with Git on Windows?", I prefer a wrapper, as it is easier to try and switch editors, or change the path of one editor, without having to register said change with a git config again.
But that is just me.

Additional information: the following solution works with Cygwin, while the zuamlifeguard's solution does not.

Original answer.

The following:

C:\prog\git>git config --global core.editor C:/prog/git/

"c:/Program Files/Notepad++/notepad++.exe" -multiInst "$*"

does work. Those commands are interpreted as shell script, hence the idea to wrap any windows set of commands in a sh script.
(As Franky comments: "Remember to save your .sh file with Unix style line endings or receive mysterious error messages!")

More details on the SO question How can I set up an editor to work with Git on Windows?

Note the '-multiInst' option, for ensuring a new instance of notepad++ for each call from Git.

Note also that, if you are using Git on Cygwin (and want to use Notepad++ from Cygwin), then scphantm explains in "using Notepad++ for Git inside Cygwin" that you must be aware that:

git is passing it a cygwin path and npp doesn't know what to do with it

So the script in that case would be:

"C:/Program Files (x86)/Notepad++/notepad++.exe" -multiInst -notabbar -nosession -noPlugin "$(cygpath -w "$*")"

Multiple lines for readability:

"C:/Program Files (x86)/Notepad++/notepad++.exe" -multiInst -notabbar \
  -nosession -noPlugin "$(cygpath -w "$*")"

With "$(cygpath -w "$*")" being the important part here.

Val commented (and then deleted) that you should not use -notabbar option:

It makes no good to disable the tab during rebase, but makes a lot of harm to general Notepad usability since -notab becomes the default setting and you must Settings>Preferences>General>TabBar> Hide>uncheck every time you start notepad after rebase. This is hell. You recommended the hell.

So use rather:

"C:/Program Files (x86)/Notepad++/notepad++.exe" -multiInst -nosession -noPlugin "$(cygpath -w "$*")"

That is:

"C:/Program Files (x86)/Notepad++/notepad++.exe" -multiInst -nosession \
  -noPlugin "$(cygpath -w "$*")"

If you want to place the script '' in a path with spaces (as in 'c:\program files\...',), you have three options:

  • Either try to quote the path (single or double quotes), as in:

    git config --global core.editor 'C:/program files/git/'
  • or try the shortname notation (not fool-proofed):

    git config --global core.editor C:/progra~1/git/
  • or (my favorite) place '' in a directory part of your %PATH% environment variable. You would not have then to specify any path for the script.

    git config --global core.editor
  • Steiny reports in the comments having to do:

    git config --global core.editor '"C:/Program Files (x86)/Git/scripts/"'

Create an ISO date object in javascript

This worked for me:

var start = new Date("2020-10-15T00:00:00.000+0000");
start = new date("2020-10-15T00:00:00.000Z");

        $gte: start
_x000D_ new Date(2020,9,15,0,0,0,0) may lead to wrong date: i mean non ISO format (remember javascript count months from 0 to 11 so it's 9 for october)

How to align linearlayout to vertical center?

use RelativeLayout inside LinearLayout



Unstage a deleted file in git

I tried the above solutions and I was still having difficulties. I had other files staged with two files that were deleted accidentally.

To undo the two deleted files I had to unstage all of the files:

git reset HEAD .

At that point I was able to do the checkout of the deleted items:

git checkout -- WorkingFolder/FileName.ext

Finally I was able to restage the rest of the files and continue with my commit.

ArrayList: how does the size increase?

Context java 8

I give my answer here in the context of Oracle java 8 implementation, since after reading all the answers, I found that an answer in the context of java 6 has given by gmgmiller, and another answer has been given in the context of java 7. But how java 8 implementes the size increasement has not been given.

In java 8, the size increasement behavior is the same as java 6, see the grow method of ArrayList:

   private void grow(int minCapacity) {
        // overflow-conscious code
        int oldCapacity = elementData.length;
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        if (newCapacity - minCapacity < 0)
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        // minCapacity is usually close to size, so this is a win:
        elementData = Arrays.copyOf(elementData, newCapacity);

the key code is this line:

int newCapacity = oldCapacity + (oldCapacity >> 1);

So clearly, the growth factor is also 1.5, the same as java 6.

PySpark 2.0 The size or shape of a DataFrame

Use df.count() to get the number of rows.

Difference between $(window).load() and $(document).ready() functions

$(window).load is an event that fires when the DOM and all the content (everything) on the page is fully loaded like CSS, images and frames. One best example is if we want to get the actual image size or to get the details of anything we use it.

$(document).ready() indicates that code in it need to be executed once the DOM got loaded and ready to be manipulated by script. It won't wait for the images to load for executing the jQuery script.

<script type = "text/javascript">
    //$(window).load was deprecated in 1.8, and removed in jquery 3.0
    // $(window).load(function() {
    //     alert("$(window).load fired");
    // });

    $(document).ready(function() {
        alert("$(document).ready fired");

$(window).load fired after the $(document).ready().

$(window).load was deprecated in 1.8, and removed in jquery 3.0

Merging dictionaries in C#

The party's pretty much dead now, but here's an "improved" version of user166390 that made its way into my extension library. Apart from some details, I added a delegate to calculate the merged value.

/// <summary>
/// Merges a dictionary against an array of other dictionaries.
/// </summary>
/// <typeparam name="TResult">The type of the resulting dictionary.</typeparam>
/// <typeparam name="TKey">The type of the key in the resulting dictionary.</typeparam>
/// <typeparam name="TValue">The type of the value in the resulting dictionary.</typeparam>
/// <param name="source">The source dictionary.</param>
/// <param name="mergeBehavior">A delegate returning the merged value. (Parameters in order: The current key, The current value, The previous value)</param>
/// <param name="mergers">Dictionaries to merge against.</param>
/// <returns>The merged dictionary.</returns>
public static TResult MergeLeft<TResult, TKey, TValue>(
    this TResult source,
    Func<TKey, TValue, TValue, TValue> mergeBehavior,
    params IDictionary<TKey, TValue>[] mergers)
    where TResult : IDictionary<TKey, TValue>, new()
    var result = new TResult();
    var sources = new List<IDictionary<TKey, TValue>> { source }

    foreach (var kv in sources.SelectMany(src => src))
        TValue previousValue;
        result.TryGetValue(kv.Key, out previousValue);
        result[kv.Key] = mergeBehavior(kv.Key, kv.Value, previousValue);

    return result;

Catch KeyError in Python

If it's raising a KeyError with no message, then it won't print anything. If you do...

    connection = manager.connect("I2Cx")
except Exception as e:
    print repr(e)'ll at least get the exception class name.

A better alternative is to use multiple except blocks, and only 'catch' the exceptions you intend to handle...

    connection = manager.connect("I2Cx")
except KeyError as e:
    print 'I got a KeyError - reason "%s"' % str(e)
except IndexError as e:
    print 'I got an IndexError - reason "%s"' % str(e)

There are valid reasons to catch all exceptions, but you should almost always re-raise them if you do...

    connection = manager.connect("I2Cx")
except KeyError as e:
    print 'I got a KeyError - reason "%s"' % str(e)
    print 'I got another exception, but I should re-raise'

...because you probably don't want to handle KeyboardInterrupt if the user presses CTRL-C, nor SystemExit if the try-block calls sys.exit().

List of all index & index columns in SQL Server DB

with connect(schema_name,table_name,index_name,index_column_id,column_name) as
(   select schema_name, table_name, index_name, index_column_id, cast( as varchar(max)) column_name
 from sys.tables t
inner join sys.schemas s on t.schema_id = s.schema_id
inner join sys.indexes i on i.object_id = t.object_id
inner join sys.index_columns ic on ic.object_id = t.object_id and ic.index_id=i.index_id
        inner join sys.columns c on c.object_id = t.object_id and
                ic.column_id = c.column_id
                where index_column_id=1
union all
select schema_name, table_name, index_name, ic.index_column_id, cast(connect.column_name + ',' + as varchar(max)) column_name
 from sys.tables t
inner join sys.schemas s on t.schema_id = s.schema_id
inner join sys.indexes i on i.object_id = t.object_id
inner join sys.index_columns ic on ic.object_id = t.object_id and ic.index_id=i.index_id
        inner join sys.columns c on c.object_id = t.object_id and
                ic.column_id = c.column_id join connect on
connect.index_column_id+1 = ic.index_column_id
and connect.schema_name =
and connect.table_name =
and connect.index_name =
select connect.schema_name,connect.table_name,connect.index_name,connect.column_name
from connect join (select schema_name,table_name,index_name,MAX(index_column_id) index_column_id
from connect group by schema_name,table_name,index_name) mx
on connect.schema_name = mx.schema_name
and connect.table_name = mx.table_name
and connect.index_name = mx.index_name
and connect.index_column_id = mx.index_column_id
order by 1,2,3

Bootstrap button drop-down inside responsive table not visible because of scroll

I have a solution using only CSS, just use position relative for dropdowns inside the table-responsive:

@media (max-width: 767px) {
  .table-responsive .dropdown-menu {
    position: relative; /* Sometimes needs !important */

Search all of Git history for a string?

Try the following commands to search the string inside all previous tracked files:

git log --patch  | less +/searching_string


git rev-list --all | GIT_PAGER=cat xargs git grep 'search_string'

which needs to be run from the parent directory where you'd like to do the searching.

Using %f with strftime() in Python to get microseconds

When the "%f" for micro seconds isn't working, please use the following method:

import datetime

def getTimeStamp():
    dt =
    return dt.strftime("%Y%j%H%M%S") + str(dt.microsecond)

Violation of PRIMARY KEY constraint. Cannot insert duplicate key in object

There could be several things causing this and it somewhat depends on what you have set up in your database.

First, you could be using a PK in the table that is also an FK to another table making the relationship 1-1. IN this case you may need to do an update rather than an insert. If you really can have only one address record for an order this may be what is happening.

Next you could be using some sort of manual process to determine the id ahead of time. The trouble with those manual processes is that they can create race conditions where two records gab the same last id and increment it by one and then the second one can;t insert.

Third, you query as it is sent to the database may be creating two records. To determine if this is the case, Run Profiler to see exactly what SQL code you are sending and if ti is a select instead of a values clause, then run the select and see if you have due to the joins gotten some records to be duplicated. IN any even when you are creating code on the fly like this the first troubleshooting step is ALWAYS to run Profiler and see if what got sent was what you expected to be sent.

Android failed to load JS bundle

I am using Ubuntu and Android only, and I was unable to get it running. I found a really simple solution which is to update your package.json file, changing this lines:

"scripts": {
    "start": "node node_modules/react-native/local-cli/cli.js start"


"scripts": {
    "start": "adb reverse tcp:8081 tcp:8081 && node node_modules/react-native/local-cli/cli.js start"

And then you run the server by typing

npm run start

This ensures the android device looks for the node server on your computer instead of locally on the phone.

How can I confirm a database is Oracle & what version it is using SQL?

If your instance is down, you are look for version information in alert.log

Or another crude way is to look into Oracle binary, If DB in hosted on Linux, try strings on Oracle binary.

strings -a $ORACLE_HOME/bin/oracle |grep RDBMS | grep RELEASE

Convert a string into an int

I had to do something like this but wanted to use a getter/setter for mine. In particular I wanted to return a long from a textfield. The other answers all worked well also, I just ended up adapting mine a little as my school project evolved.

long ms = [self.textfield.text longLongValue];
return ms;

Pandas conditional creation of a series/dataframe column

You can simply use the powerful .loc method and use one condition or several depending on your need (tested with pandas=1.0.5).

Code Summary:

df=pd.DataFrame(dict(Type='A B B C'.split(), Set='Z Z X Y'.split()))
df['Color'] = "red"
df.loc[(df['Set']=="Z"), 'Color'] = "green"

df.loc[(df['Set']=="Z")&(df['Type']=="B")|(df['Type']=="C"), 'Color'] = "purple"


df=pd.DataFrame(dict(Type='A B B C'.split(), Set='Z Z X Y'.split()))

# df so far: 
  Type Set  
0    A   Z 
1    B   Z 
2    B   X 
3    C   Y

add a 'color' column and set all values to "red"

df['Color'] = "red"

Apply your single condition:

df.loc[(df['Set']=="Z"), 'Color'] = "green"

# df: 
  Type Set  Color
0    A   Z  green
1    B   Z  green
2    B   X    red
3    C   Y    red

or multiple conditions if you want:

df.loc[(df['Set']=="Z")&(df['Type']=="B")|(df['Type']=="C"), 'Color'] = "purple"

You can read on Pandas logical operators and conditional selection here: Logical operators for boolean indexing in Pandas

Controlling execution order of unit tests in Visual Studio

I'll not address the order of tests, sorry. Others already did it. Also, if you know about "ordered tests" - well, this is MS VS's response to the problem. I know that those ordered-tests are no fun. But they thought it will be "it" and there's really nothing more in MSTest about that.

I write about one of your assumptions:

as there is no way to tear down the static class.

Unless your static class represents some process-wide external state external to your code (like ie. the state of an unmanaged native DLL library thats P/Invoked by the rest of your code), your assumption that there is no way is not true.

If your static class refers to this, then sorry, you are perfectly right, the rest of this anwer is irrelevant. Still, as you didn't say that, I assume your code is "managed".

Think and check the AppDomain thingy. Rarely it is needed, but this is exactly the case when you'd probably like to use them.

You can create a new AppDomain, and instantiate the test there, and run the test method there. Static data used by managed code will isolated there and upon completion, you will be able to unload the AppDomain and all the data, statics included, will evaporate. Then, next test would initialize another appdomain, and so on.

This will work unless you have external state that you must track. AppDomains only isolate the managed memory. Any native DLL will still be load per-process and their state will be shared by all AppDomains.

Also, creating/tearing down the appdomains will, well, slow down the tests. Also, you may have problems with assembly resolution in the child appdomain, but they are solvable with reasonable amount of reusable code.

Also, you may have small problems with passing test data to - and back from - the child AppDomain. Objects passed will either have to be serializable in some way, or be MarshalByRef or etc. Talking cross-domain is almost like IPC.

However, take care here, it will be 100% managed talking. If you take some extra care and add a little work to the AppDomain setup, you will be able to even pass delegates and run them in the target domain. Then, instead of making some hairy cross-domain setup, you can wrap your tests with to something like:

void testmethod()
    TestAppDomainHelper.Run( () =>
        // your test code

or even

void testmethod()
    // your test code

if your test framework supports creating such wrappers/extensions. After some initial research and work, using them is almost trivial.

how to get the one entry from hashmap without iterating

import java.util.*;

public class Friday {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<String, Integer>();

        map.put("code", 10);
        map.put("to", 11);
        map.put("joy", 12);

        if (! map.isEmpty()) {
            Map.Entry<String, Integer> entry = map.entrySet().iterator().next();

This approach doesn't work because you used HashMap. I assume using LinkedHashMap will be right solution in this case.

Git: can't undo local changes (error: path ... is unmerged)

I find git stash very useful for temporal handling of all 'dirty' states.

Finding the average of a list

Combining a couple of the above answers, I've come up with the following which works with reduce and doesn't assume you have L available inside the reducing function:

from operator import truediv

L = [15, 18, 2, 36, 12, 78, 5, 6, 9]

def sum_and_count(x, y):
        return (x[0] + y, x[1] + 1)
    except TypeError:
        return (x + y, 2)

truediv(*reduce(sum_and_count, L))

# prints 

How to invert a grep expression

Use command-line option -v or --invert-match,

ls -R |grep -v -E .*[\.exe]$\|.*[\.html]$

Proper way to handle multiple forms on one page in Django

This is a bit late, but this is the best solution I found. You make a look-up dictionary for the form name and its class, you also have to add an attribute to identify the form, and in your views you have to add it as a hidden field, with the form.formlabel.

# form holder
form_holder = {
    'majeur': {
        'class': FormClass1,
    'majsoft': {
        'class': FormClass2,
    'tiers1': {
        'class': FormClass3,
    'tiers2': {
        'class': FormClass4,
    'tiers3': {
        'class': FormClass5,
    'tiers4': {
        'class': FormClass6,

for key in form_holder.keys():
    # If the key is the same as the formlabel, we should use the posted data
    if request.POST.get('formlabel', None) == key:
        # Get the form and initate it with the sent data
        form = form_holder.get(key).get('class')(

        # Validate the form
        if form.is_valid():
            # Correct data entries
  , _(u"Configuration validée."))

                # Save succeeded
                    _(u"Données enregistrées avec succès.")
                # Save failed
                    _(u"Un problème est survenu pendant l'enregistrement "
                      u"des données, merci de réessayer plus tard.")
            # Form is not valid, show feedback to the user
                _(u"Merci de corriger les erreurs suivantes.")
        # Just initiate the form without data
        form = form_holder.get(key).get('class')(key)()

    # Add the attribute for the name
    setattr(form, 'formlabel', key)

    # Append it to the tempalte variable that will hold all the forms

I hope this will help in the future.

How to remove item from list in C#?

    class Program
        public static List<Product> list;
        static void Main(string[] args)

            list = new List<Product>() { new Product() { ProductId=1, Name="Nike 12N0",Brand="Nike",Price=12000,Quantity=50},
                 new Product() { ProductId =2, Name = "Puma 560K", Brand = "Puma", Price = 120000, Quantity = 55 },
                 new Product() { ProductId=3, Name="WoodLand V2",Brand="WoodLand",Price=21020,Quantity=25},
                 new Product() { ProductId=4, Name="Adidas S52",Brand="Adidas",Price=20000,Quantity=35},
                 new Product() { ProductId=5, Name="Rebook SPEED2O",Brand="Rebook",Price=1200,Quantity=15}};

            Console.WriteLine("Enter ProductID to remove");
            int uno = Convert.ToInt32(Console.ReadLine());
            var itemToRemove = list.Find(r => r.ProductId == uno);
            if (itemToRemove != null)
            Console.WriteLine($"{itemToRemove.ProductId}{itemToRemove.Name}{itemToRemove.Brand}{itemToRemove.Price}{ itemToRemove.Quantity}");
            Console.WriteLine("------------sucessfully Removed---------------");

            var query2 = from x in list select x;
            foreach (var item in query2)
                /*Console.WriteLine(item.ProductId+" "+item.Name+" "+item.Brand+" "+item.Price+" "+item.Quantity );*/
                Console.WriteLine($"{item.ProductId}{item.Name}{item.Brand}{item.Price}{ item.Quantity}");



When to use DataContract and DataMember attributes?

In terms of WCF, we can communicate with the server and client through messages. For transferring messages, and from a security prospective, we need to make a data/message in a serialized format.

For serializing data we use [datacontract] and [datamember] attributes. In your case if you are using datacontract WCF uses DataContractSerializer else WCF uses XmlSerializer which is the default serialization technique.

Let me explain in detail:

basically WCF supports 3 types of serialization:

  1. XmlSerializer
  2. DataContractSerializer
  3. NetDataContractSerializer

XmlSerializer :- Default order is Same as class

DataContractSerializer/NetDataContractSerializer :- Default order is Alphabetical

XmlSerializer :- XML Schema is Extensive

DataContractSerializer/NetDataContractSerializer :- XML Schema is Constrained

XmlSerializer :- Versioning support not possible

DataContractSerializer/NetDataContractSerializer :- Versioning support is possible

XmlSerializer :- Compatibility with ASMX

DataContractSerializer/NetDataContractSerializer :- Compatibility with .NET Remoting

XmlSerializer :- Attribute not required in XmlSerializer

DataContractSerializer/NetDataContractSerializer :- Attribute required in this serializing

so what you use depends on your requirements...

SQL Server - Adding a string to a text column (concat equivalent)

To Join two string in SQL Query use function CONCAT(Express1,Express2,...)


SELECT CODE, CONCAT(Rtrim(FName), " " , TRrim(LName)) as Title FROM MyTable

getResourceAsStream() vs FileInputStream

The and consorts acts on the local disk file system. The root cause of your problem is that relative paths in are dependent on the current working directory. I.e. the directory from which the JVM (in your case: the webserver's one) is started. This may for example be C:\Tomcat\bin or something entirely different, but thus not C:\Tomcat\webapps\contextname or whatever you'd expect it to be. In a normal Eclipse project, that would be C:\Eclipse\workspace\projectname. You can learn about the current working directory the following way:

System.out.println(new File(".").getAbsolutePath());

However, the working directory is in no way programmatically controllable. You should really prefer using absolute paths in the File API instead of relative paths. E.g. C:\full\path\to\file.ext.

You don't want to hardcode or guess the absolute path in Java (web)applications. That's only portability trouble (i.e. it runs in system X, but not in system Y). The normal practice is to place those kind of resources in the classpath, or to add its full path to the classpath (in an IDE like Eclipse that's the src folder and the "build path" respectively). This way you can grab them with help of the ClassLoader by ClassLoader#getResource() or ClassLoader#getResourceAsStream(). It is able to locate files relative to the "root" of the classpath, as you by coincidence figured out. In webapplications (or any other application which uses multiple classloaders) it's recommend to use the ClassLoader as returned by Thread.currentThread().getContextClassLoader() for this so you can look "outside" the webapp context as well.

Another alternative in webapps is the ServletContext#getResource() and its counterpart ServletContext#getResourceAsStream(). It is able to access files located in the public web folder of the webapp project, including the /WEB-INF folder. The ServletContext is available in servlets by the inherited getServletContext() method, you can call it as-is.

See also:

Pandas DataFrame: replace all values in a column, based on condition

You need to select that column:

In [41]:
df.loc[df['First Season'] > 1990, 'First Season'] = 1

                 Team  First Season  Total Games
0      Dallas Cowboys          1960          894
1       Chicago Bears          1920         1357
2   Green Bay Packers          1921         1339
3      Miami Dolphins          1966          792
4    Baltimore Ravens             1          326
5  San Franciso 49ers          1950         1003

So the syntax here is:

df.loc[<mask>(here mask is generating the labels to index) , <optional column(s)> ]

You can check the docs and also the 10 minutes to pandas which shows the semantics


If you want to generate a boolean indicator then you can just use the boolean condition to generate a boolean Series and cast the dtype to int this will convert True and False to 1 and 0 respectively:

In [43]:
df['First Season'] = (df['First Season'] > 1990).astype(int)

                 Team  First Season  Total Games
0      Dallas Cowboys             0          894
1       Chicago Bears             0         1357
2   Green Bay Packers             0         1339
3      Miami Dolphins             0          792
4    Baltimore Ravens             1          326
5  San Franciso 49ers             0         1003

PHP 7 simpleXML

Had the same problem on AWS Linux 2, phpinfo() shows SimpleXML installed but not working, below cmd solved my issue

sudo yum install php-xml

Right to Left support for Twitter Bootstrap 3

in every version of bootstrap,you can do it manually

  1. set rtl direction to your body
  2. in bootstrap.css file, look for ".col-sm-9{float:left}" expression,change it to float:right

this do most things that you want for rtl

How can I make SQL case sensitive string comparison on MySQL?

The good news is that if you need to make a case-sensitive query, it is very easy to do:

SELECT *  FROM `table` WHERE BINARY `column` = 'value'

Create Table from View

Looks a lot like Oracle, but that doesn't work on SQL Server.

You can, instead, adopt the following syntax...


How can I check whether Google Maps is fully loaded?

In my case, Tile Image loaded from remote url and tilesloaded event was triggered before render the image.

I solved with following dirty way.

var tileCount = 0;
var options = {
    getTileUrl: function(coord, zoom) {
        return ""+coord;
    tileSize: new google.maps.Size(256, 256),
    opacity: 0.5,
    isPng: true
var MT = new google.maps.ImageMapType(options);
map.overlayMapTypes.setAt(0, MT);
google.maps.event.addListenerOnce(map, 'tilesloaded', function(){
    var checkExist = setInterval(function() {
        if ($('#map_canvas > div > div > div:nth-child(1) > div:nth-child(1) > div:nth-child(1) > div:nth-child(2) > div > div').length === tileCount) {
    }, 100); // check every 100ms

Add back button to action bar

if anyone else need the solution

public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == {

    return super.onOptionsItemSelected(item);

jQuery bind to Paste Event, how to get the content of the paste

There is an onpaste event that works in modern day browsers. You can access the pasted data using the getData function on the clipboardData object.

$("#textareaid").bind("paste", function(e){
    // access the clipboard using the api
    var pastedData = e.originalEvent.clipboardData.getData('text');
} );

Note that bind and unbind are deprecated as of jQuery 3. The preferred call is to on.

All modern day browsers support the Clipboard API.

See also: In Jquery How to handle paste?

Extracting columns from text file with different delimiters in Linux

You can use cut with a delimiter like this:

with space delim:

cut -d " " -f1-100,1000-1005 infile.csv > outfile.csv

with tab delim:

cut -d$'\t' -f1-100,1000-1005 infile.csv > outfile.csv

I gave you the version of cut in which you can extract a list of intervals...

Hope it helps!

Why avoid increment ("++") and decrement ("--") operators in JavaScript?

I'm frankly confused by that advice. Part of me wonders if it has more to do with a lack of experience (perceived or actual) with javascript coders.

I can see how someone just "hacking" away at some sample code could make an innocent mistake with ++ and --, but I don't see why an experienced professional would avoid them.

Background images: how to fill whole div if image is small and vice versa

This worked perfectly for me

background-repeat: no-repeat;
background-size: 100% 100%;

Bootstrap 3 Flush footer to bottom. not fixed

Galen Gidman has posted a really good solution to the problem of a responsive sticky footer that does not have a fixed height. You can find his full solution on his blog:


<header class="page-row">
  <h1>Site Title</h1>

<main class="page-row page-row-expanded">
  <p>Page content goes here.</p>

<footer class="page-row">
  <p>Copyright, blah blah blah.</p>


body { height: 100%; }

body {
  display: table;
  width: 100%;

.page-row {
  display: table-row;
  height: 1px;

.page-row-expanded { height: 100%; }

Datatable select with multiple conditions

If you really don't want to run into lots of annoying errors (datediff and such can't be evaluated in DataTable.Select among other things and even if you do as suggested use DataTable.AsEnumerable you will have trouble evaluating DateTime fields) do the following:

1) Model Your Data (create a class with DataTable columns)


public class Person
public string PersonId { get; set; }
public DateTime DateBorn { get; set; }

2) Add this helper class to your code

public static class Extensions
/// <summary>
/// Converts datatable to list<T> dynamically
/// </summary>
/// <typeparam name="T">Class name</typeparam>
/// <param name="dataTable">data table to convert</param>
/// <returns>List<T></returns>
public static List<T> ToList<T>(this DataTable dataTable) where T : new()
    var dataList = new List<T>();

    //Define what attributes to be read from the class
    const BindingFlags flags = BindingFlags.Public | BindingFlags.Instance;

    //Read Attribute Names and Types
    var objFieldNames = typeof(T).GetProperties(flags).Cast<PropertyInfo>().
        Select(item => new
            Name = item.Name,
            Type = Nullable.GetUnderlyingType(item.PropertyType) ?? item.PropertyType

    //Read Datatable column names and types
    var dtlFieldNames = dataTable.Columns.Cast<DataColumn>().
        Select(item => new {
            Name = item.ColumnName,
            Type = item.DataType

    foreach (DataRow dataRow in dataTable.AsEnumerable().ToList())
        var classObj = new T();

        foreach (var dtField in dtlFieldNames)
            PropertyInfo propertyInfos = classObj.GetType().GetProperty(dtField.Name);

            var field = objFieldNames.Find(x => x.Name == dtField.Name);

            if (field != null)

                if (propertyInfos.PropertyType == typeof(DateTime))
                    (classObj, ConvertToDateTime(dataRow[dtField.Name]), null);
                else if (propertyInfos.PropertyType == typeof(int))
                    (classObj, ConvertToInt(dataRow[dtField.Name]), null);
                else if (propertyInfos.PropertyType == typeof(long))
                    (classObj, ConvertToLong(dataRow[dtField.Name]), null);
                else if (propertyInfos.PropertyType == typeof(decimal))
                    (classObj, ConvertToDecimal(dataRow[dtField.Name]), null);
                else if (propertyInfos.PropertyType == typeof(String))
                    if (dataRow[dtField.Name].GetType() == typeof(DateTime))
                        (classObj, ConvertToDateString(dataRow[dtField.Name]), null);
                        (classObj, ConvertToString(dataRow[dtField.Name]), null);
    return dataList;

private static string ConvertToDateString(object date)
    if (date == null)
        return string.Empty;

    return HelperFunctions.ConvertDate(Convert.ToDateTime(date));

private static string ConvertToString(object value)
    return Convert.ToString(HelperFunctions.ReturnEmptyIfNull(value));

private static int ConvertToInt(object value)
    return Convert.ToInt32(HelperFunctions.ReturnZeroIfNull(value));

private static long ConvertToLong(object value)
    return Convert.ToInt64(HelperFunctions.ReturnZeroIfNull(value));

private static decimal ConvertToDecimal(object value)
    return Convert.ToDecimal(HelperFunctions.ReturnZeroIfNull(value));

private static DateTime ConvertToDateTime(object date)
    return Convert.ToDateTime(HelperFunctions.ReturnDateTimeMinIfNull(date));

public static class HelperFunctions

public static object ReturnEmptyIfNull(this object value)
    if (value == DBNull.Value)
        return string.Empty;
    if (value == null)
        return string.Empty;
    return value;
public static object ReturnZeroIfNull(this object value)
    if (value == DBNull.Value)
        return 0;
    if (value == null)
        return 0;
    return value;
public static object ReturnDateTimeMinIfNull(this object value)
    if (value == DBNull.Value)
        return DateTime.MinValue;
    if (value == null)
        return DateTime.MinValue;
    return value;
/// <summary>
/// Convert DateTime to string
/// </summary>
/// <param name="datetTime"></param>
/// <param name="excludeHoursAndMinutes">if true it will execlude time from datetime string. Default is false</param>
/// <returns></returns>
public static string ConvertDate(this DateTime datetTime, bool excludeHoursAndMinutes = false)
    if (datetTime != DateTime.MinValue)
        if (excludeHoursAndMinutes)
            return datetTime.ToString("yyyy-MM-dd");
        return datetTime.ToString("yyyy-MM-dd HH:mm:ss.fff");
    return null;

3) Easily convert your DataTable (dt) to a List of objects with following code:

List<Person> persons = Extensions.ToList<Person>(dt);

4) have fun using Linq without the annoying row.Field<type> bit you have to use when using AsEnumerable


var personsBornOn1980 = persons.Where(x=>x.DateBorn.Year == 1980);

Printing out all the objects in array list

Override toString() method in Student class as below:

   public String toString() {
        return ("StudentName:"+this.getStudentName()+
                    " Student No: "+ this.getStudentNo() +
                    " Email: "+ this.getEmail() +
                    " Year : " + this.getYear());

How to map a composite key with JPA and Hibernate?

The primary key class must define equals and hashCode methods

  1. When implementing equals you should use instanceof to allow comparing with subclasses. If Hibernate lazy loads a one to one or many to one relation, you will have a proxy for the class instead of the plain class. A proxy is a subclass. Comparing the class names would fail.
    More technically: You should follow the Liskows Substitution Principle and ignore symmetricity.
  2. The next pitfall is using something like name.equals( instead of name.equals(that.getName()). The first will fail, if that is a proxy.

PHP read and write JSON from file

If you want to display the JSON data in well defined formate you can modify the code as:

file_put_contents($file, json_encode($json,TRUE));

$headers = array('http'=>array('method'=>'GET','header'=>'Content: type=application/json \r\n'.'$agent \r\n'.'$hash'));


$str = file_get_contents("list.txt",FILE_USE_INCLUDE_PATH,$context);



foreach($str1 as $key=>$value)

    echo "key is: $key.\n";

    echo "values are: \t";
        foreach ($value as $k) {

        echo " $k. \t";
        # code...
        echo "<br></br>";
        echo "\n";


How do servlets work? Instantiation, sessions, shared variables and multithreading

The Servlet Specification JSR-315 clearly defines the web container behavior in the service (and doGet, doPost, doPut etc.) methods ( Multithreading Issues, Page 9):

A servlet container may send concurrent requests through the service method of the servlet. To handle the requests, the Servlet Developer must make adequate provisions for concurrent processing with multiple threads in the service method.

Although it is not recommended, an alternative for the Developer is to implement the SingleThreadModel interface which requires the container to guarantee that there is only one request thread at a time in the service method. A servlet container may satisfy this requirement by serializing requests on a servlet, or by maintaining a pool of servlet instances. If the servlet is part of a Web application that has been marked as distributable, the container may maintain a pool of servlet instances in each JVM that the application is distributed across.

For servlets not implementing the SingleThreadModel interface, if the service method (or methods such as doGet or doPost which are dispatched to the service method of the HttpServlet abstract class) has been defined with the synchronized keyword, the servlet container cannot use the instance pool approach, but must serialize requests through it. It is strongly recommended that Developers not synchronize the service method (or methods dispatched to it) in these circumstances because of detrimental effects on performance

CSS content generation before or after 'input' elements

Something like this works:

input + label::after {_x000D_
  content: 'click my input';_x000D_
  color: black;_x000D_
input:focus + label::after {_x000D_
  content: 'not valid yet';_x000D_
  color: red;_x000D_
input:valid + label::after {_x000D_
  content: 'looks good';_x000D_
  color: green;_x000D_
<input id="input" type="number" required />_x000D_
<label for="input"></label>

Then add some floats or positioning to order stuff.

How to prevent "The play() request was interrupted by a call to pause()" error?

I have encountered this issue recently as well - this could be a race condition between play() and pause(). It looks like there is a reference to this issue, or something related here.

As @Patrick points out, pause does not return a promise (or anything), so the above solution won't work. While MDN does not have docs on pause(), in the WC3 draft for Media Elements, it says:


Sets the paused attribute to true, loading the media resource if necessary.

So one might also check the paused attribute in their timeout callback.

Based on this great SO answer, here's a way you can check if the video is (or isn't) truly playing, so you can safely trigger a play() without the error.

var isPlaying = video.currentTime > 0 && !video.paused && !video.ended 
    && video.readyState > video.HAVE_CURRENT_DATA;

if (!isPlaying) {;

Otherwise, @Patrick's answer should work.

How to find whether MySQL is installed in Red Hat?

yum list installed | grep mysql

Then if it's not installed you can do (as root)

yum install mysql -y

strdup() - what does it do in C?

The most valuable thing it does is give you another string identical to the first, without requiring you to allocate memory (location and size) yourself. But, as noted, you still need to free it (but which doesn't require a quantity calculation, either.)

@RequestParam in Spring MVC handling optional parameters

As part of Spring 4.1.1 onwards you now have full support of Java 8 Optional (original ticket) therefore in your example both requests will go via your single mapping endpoint as long as you replace required=false with Optional for your 3 params logout, name, password:

@RequestMapping (value = "/submit/id/{id}", method = RequestMethod.GET,   
public String showLoginWindow(@PathVariable("id") String id,
                              @RequestParam(value = "logout") Optional<String> logout,
                              @RequestParam("name") Optional<String> username,
                              @RequestParam("password") Optional<String> password,
                              @ModelAttribute("submitModel") SubmitModel model,
                              BindingResult errors) throws LoginException {...}

Creating Roles in Identity MVC 5

If you are using the default template that is created when you select a new Web application and selected Individual User accounts as Authentication and trying to create users with Roles so here is the solution. In the Account Controller's Register method which is called using [HttpPost], add the following lines in if condition.

using Microsoft.AspNet.Identity.EntityFramework;

var user = new ApplicationUser { UserName = model.Email, Email = model.Email };

var result = await UserManager.CreateAsync(user, model.Password);

if (result.Succeeded)
  var roleStore = new RoleStore<IdentityRole>(new ApplicationDbContext());
  var roleManager = new RoleManager<IdentityRole>(roleStore);
  if(!await roleManager.RoleExistsAsync("YourRoleName"))
     await roleManager.CreateAsync(new IdentityRole("YourRoleName"));

  await UserManager.AddToRoleAsync(user.Id, "YourRoleName");
  await SignInManager.SignInAsync(user, isPersistent:false, rememberBrowser:false);
  return RedirectToAction("Index", "Home");

This will create first create a role in your database and then add the newly created user to this role.

How do you uninstall a python package that was installed using distutils?

If this is for testing and/or development purposes, setuptools has a develop command that updates every time you make a change (so you don't have to uninstall and reinstall every time you make a change). And you can uninstall the package using this command as well.

If you do use this, anything that you declare as a script will be left behind as a lingering file.

How can I remove leading and trailing quotes in SQL Server?

I know this is an older question post, but my daughter came to me with the question, and referenced this page as having possible answers. Given that she's hunting an answer for this, it's a safe assumption others might still be as well.

All are great approaches, and as with everything there's about as many way to skin a cat as there are cats to skin.

If you're looking for a left trim and a right trim of a character or string, and your trailing character/string is uniform in length, here's my suggestion:


Or in this question...

SELECT SUBSTRING('"this is a test message"',2, LEN('"this is a test message"')-2)

With this, you simply adjust the SUBSTRING starting point (2), and LEN position (-2) to whatever value you need to remove from your string.

It's non-iterative and doesn't require explicit case testing and above all it's inline all of which make for a cleaner execution plan.

CSS/HTML: Create a glowing border around an Input Field

Modified version with little less glowing version.

input {
    /* round the corners */
    //background-color: transparent;
    border: 1px solid;
    height: 20px;
    width: 160px;
    color: #CCC;
    border-radius: 4px;
    -moz-border-radius: 4px;
    -webkit-border-radius: 4px;    

input:focus { 
    border: 1px solid #4195fc; 
    /* create a BIG glow */
    box-shadow: 0px 0px 5px #4195fc; 
    -moz-box-shadow: 0px 0px 5px #4195fc;
    -webkit-box-shadow: 0px 0px 5px #4195fc;  

"Unorderable types: int() < str()"

Just a side note, in Python 2.0 you could compare anything to anything (int to string). As this wasn't explicit, it was changed in 3.0, which is a good thing as you are not running into the trouble of comparing senseless values with each other or when you forget to convert a type.

Bootstrap 3 - set height of modal window according to screen size

I assume you want to make modal use as much screen space as possible on phones. I've made a plugin to fix this UX problem of Bootstrap modals on mobile phones, you can check it out here -

All you will need to do is to apply modal-fullscreen class and it will act similar to native screens of iOS/Android.

Get row-index values of Pandas DataFrame as list?

To get the index values as a list/list of tuples for Index/MultiIndex do:

df.index.values.tolist()  # an ndarray method, you probably shouldn't depend on this


list(df.index.values)  # this will always work in pandas

mongodb/mongoose findMany - find all documents with IDs listed in array

This code works for me just fine as of mongoDB v4.2 and mongoose 5.9.9:

const Ids = ['id1','id2','id3']
const results = await Model.find({ _id: Ids})

and the Ids can be of type ObjectId or String

Get the name of a pandas DataFrame

You can name the dataframe with the following, and then call the name wherever you like:

import pandas as pd
df = pd.DataFrame( data=np.ones([4,4]) ) = 'Ones'


Hope that helps.

psql: FATAL: Ident authentication failed for user "postgres"

I had to reinstall pdAdmin to resolve this issue

brew cask reinstall pgadmin4

Fix CSS hover on iPhone/iPad/iPod

Old Post I know however I successfully used onlclick="" when populating a table with JSON data. Tried many other options / scripts etc before, nothing worked. Will attempt this approach elsewhere. Thanks @Dan Morris .. from 2013!

     function append_json(data) {
     var table=document.getElementById('gable');
     data.forEach(function(object) {
         var tr=document.createElement('tr');
         tr.innerHTML='<td onclick="">' + object.COUNTRY + '</td>' + '<td onclick="">' + object.PoD + '</td>' + '<td onclick="">' + object.BALANCE + '</td>' + '<td onclick="">' + object.DATE + '</td>';

The order of keys in dictionaries

Python 3.7+

In Python 3.7.0 the insertion-order preservation nature of dict objects has been declared to be an official part of the Python language spec. Therefore, you can depend on it.

Python 3.6 (CPython)

As of Python 3.6, for the CPython implementation of Python, dictionaries maintain insertion order by default. This is considered an implementation detail though; you should still use collections.OrderedDict if you want insertion ordering that's guaranteed across other implementations of Python.

Python >=2.7 and <3.6

Use the collections.OrderedDict class when you need a dict that remembers the order of items inserted.

Twitter Bootstrap Button Text Word Wrap

You can simply add this class.

.btn {
    white-space:normal !important;
    word-wrap: break-word; 

Fixing Sublime Text 2 line endings?

to chnage line endings from LF to CRLF:

open Sublime and follow the steps:-

1 press Ctrl+shift+p then install package name line unify endings

then again press Ctrl+shift+p

2 in the blank input box type "Line unify ending "

3 Hit enter twice

Sublime may freeze for sometimes and as a result will change the line endings from LF to CRLF

How to add AUTO_INCREMENT to an existing column?

Simply just add auto_increment Constraint In column or MODIFY COLUMN :-


Or add a column first then change column as -

1. Alter TABLE `emp` ADD COLUMN `id`;


Ruby on Rails: how to render a string as HTML?

since you are translating, and picking out your wanted code from a person's crappy coded file, could you use content_tag, in combo with your regex's.

Stealing from the api docs, you could interpolate this translated code into a content_tag like:

<%= content_tag translated_tag_type.to_sym, :class => "#{translated_class}" do -%>
<%= translated_text %>
<% end -%>
# => <div class="strong">Hello world!</div>

Not knowing your code, this kind of thinking will make sure your translated code is too compliant.

Copying data from one SQLite database to another

Consider a example where I have two databases namely allmsa.db and atlanta.db. Say the database allmsa.db has tables for all msas in US and database atlanta.db is empty.

Our target is to copy the table atlanta from allmsa.db to atlanta.db.


  1. sqlite3 atlanta.db(to go into atlanta database)
  2. Attach allmsa.db. This can be done using the command ATTACH '/mnt/fastaccessDS/core/csv/allmsa.db' AS AM; note that we give the entire path of the database to be attached.
  3. check the database list using sqlite> .databases you can see the output as
seq  name             file                                                      
---  ---------------  ----------------------------------------------------------
0    main             /mnt/fastaccessDS/core/csv/atlanta.db                  
2    AM               /mnt/fastaccessDS/core/csv/allmsa.db 
  1. now you come to your actual target. Use the command INSERT INTO atlanta SELECT * FROM AM.atlanta;

This should serve your purpose.

How do I rewrite URLs in a proxy response in NGINX

We should first read the documentation on proxy_pass carefully and fully.

The URI passed to upstream server is determined based on whether "proxy_pass" directive is used with URI or not. Trailing slash in proxy_pass directive means that URI is present and equal to /. Absense of trailing slash means hat URI is absent.

Proxy_pass with URI:

location /some_dir/ {
    proxy_pass http://some_server/;

With the above, there's the following proxy:

http:// your_server/some_dir/ some_subdir/some_file ->
http:// some_server/          some_subdir/some_file

Basically, /some_dir/ gets replaced by / to change the request path from /some_dir/some_subdir/some_file to /some_subdir/some_file.

Proxy_pass without URI:

location /some_dir/ {
    proxy_pass http://some_server;

With the second (no trailing slash): the proxy goes like this:

http:// your_server /some_dir/some_subdir/some_file ->
http:// some_server /some_dir/some_subdir/some_file

Basically, the full original request path gets passed on without changes.

So, in your case, it seems you should just drop the trailing slash to get what you want.


Note that automatic rewrite only works if you don't use variables in proxy_pass. If you use variables, you should do rewrite yourself:

location /some_dir/ {
  rewrite    /some_dir/(.*) /$1 break;
  proxy_pass $upstream_server;

There are other cases where rewrite wouldn't work, that's why reading documentation is a must.


Reading your question again, it seems I may have missed that you just want to edit the html output.

For that, you can use the sub_filter directive. Something like ...

location /admin/ {
    proxy_pass http://localhost:8080/;
    sub_filter "http://your_server/" "http://your_server/admin/";
    sub_filter_once off;

Basically, the string you want to replace and the replacement string

How to do a FULL OUTER JOIN in MySQL?

Modified shA.t's query for more clarity:

-- t1 left join t2
SELECT t1.value, t2.value
FROM t1 LEFT JOIN t2 ON t1.value = t2.value   

    UNION ALL -- include duplicates

-- t1 right exclude join t2 (records found only in t2)
SELECT t1.value, t2.value
FROM t1 RIGHT JOIN t2 ON t1.value = t2.value
WHERE t1.value IS NULL 

How can you integrate a custom file browser/uploader with CKEditor?

An article at zerokspot entitled Custom filebrowser callbacks in CKEditor 3.0 handles this. The most relevant section is quoted below:

So all you have to do from the file browser when you have a file selected is to call this code with the right callback number (normally 1) and the URL of the selected file:,url);

For the quick-uploader the process is quite similar. At first I thought that the editor might be listening for a 200 HTTP return code and perhaps look into some header field or something like that to determine the location of the uploaded file, but then - through some Firebug monitoring - I noticed that all that happens after an upload is the following code:

<script type="text/javascript">,url, errorMessage); </script>

If the upload failed, set the errorMessage to some non-zero-length string and empty the url, and vice versa on success.

Get a worksheet name using Excel VBA

i need to change the sheet name by the name of the file was opened

Sub Get_Data_From_File5()
    Dim FileToOpen As Variant
    Dim OpenBook As Workbook
    Dim currentName As String
    currentName = ActiveSheet.Name
    Application.ScreenUpdating = False
    FileToOpen = Application.GetOpenFilename(Title:="Browse for your File & Import Range", FileFilter:="Excel Files (*.csv*),*csv*")
    If FileToOpen <> False Then
        Set OpenBook = Application.Workbooks.Open(FileToOpen)
        ThisWorkbook.Worksheets(currentName).Range("Aw1:bc5000").PasteSpecial xlPasteValues
        OpenBook.Close False
    End If
    Application.ScreenUpdating = True
End Sub

Ruby function to remove all white spaces?

"1232 23 2 23 232 232".delete(' ')
=> "123223223232232"

Delete works faster =)

user         system     total      real
gsub, s      0.180000   0.010000   0.190000 (0.193014)
gsub, s+     0.200000   0.000000   0.200000 (0.196408)
gsub, space  0.220000   0.000000   0.220000 (0.222711)
gsub, join   0.200000   0.000000   0.200000 (0.193478)
delete       0.040000   0.000000   0.040000 (0.045157)

Getting PEAR to work on XAMPP (Apache/MySQL stack on Windows)

Try adding the drive letter:


also verify that PEAR.php is actually there, it might be in \php\ instead:


LINQ to read XML

A couple of plain old foreach loops provides a clean solution:

foreach (XElement level1Element in XElement.Load("data.xml").Elements("level1"))

    foreach (XElement level2Element in level1Element.Elements("level2"))
        result.AppendLine("  " + level2Element.Attribute("name").Value);

How can I stop "property does not exist on type JQuery" syntax errors when using Typescript?

You can cast it to

(<any>$('.selector') ).function();

Ex: date picker initialize using jquery

(<any>$('.datepicker') ).datepicker();

Changing Tint / Background color of UITabBar

I have been able to make it work by subclassing a UITabBarController and using private classes:

@interface UITabBarController (private)
- (UITabBar *)tabBar;

@implementation CustomUITabBarController

- (void)viewDidLoad {
    [super viewDidLoad];

    CGRect frame = CGRectMake(0.0, 0.0, self.view.bounds.size.width, 48);
    UIView *v = [[UIView alloc] initWithFrame:frame];
    [v setBackgroundColor:kMainColor];
    [v setAlpha:0.5];
    [[self tabBar] addSubview:v];
    [v release];


Split and join C# string

You can use string.Split and string.Join:

string theString = "Some Very Large String Here";
var array = theString.Split(' ');
string firstElem = array.First();
string restOfArray = string.Join(" ", array.Skip(1));

If you know you always only want to split off the first element, you can use:

var array = theString.Split(' ', 2);

This makes it so you don't have to join:

string restOfArray = array[1];

Count work days between two dates

As with DATEDIFF, I do not consider the end date to be part of the interval. The number of (for example) Sundays between @StartDate and @EndDate is the number of Sundays between an "initial" Monday and the @EndDate minus the number of Sundays between this "initial" Monday and the @StartDate. Knowing this, we can calculate the number of workdays as follows:

SET @StartDate = '2018/01/01'
SET @EndDate = '2019/01/01'

SELECT DATEDIFF(Day, @StartDate, @EndDate) -- Total Days
  - (DATEDIFF(Day, 0, @EndDate)/7 - DATEDIFF(Day, 0, @StartDate)/7) -- Sundays
  - (DATEDIFF(Day, -1, @EndDate)/7 - DATEDIFF(Day, -1, @StartDate)/7) -- Saturdays

Best regards!

Node.js/Windows error: ENOENT, stat 'C:\Users\RT\AppData\Roaming\npm'

You can go to the Start Menu and search the Node.js icon and open the shell and then install anything with

install <packagename> -g

jQuery Find and List all LI elements within a UL within a specific DIV


// or:


Now that you added that comment explaining that you want to "form an array of rels per column", you should do this:

var rels = [];

$('ul').each(function() {
    var localRels = [];

        localRels.push( $(this).attr('rel') );


IntelliJ and Tomcat.. Howto..?

Here is step-by-step instruction for Tomcat configuration in IntellijIdea:

1) Create IntellijIdea project via WebApplication template. Idea should be Ultimate version, not Community edition

enter image description here

2) Go to Run-Edit configutaion and set up Tomcat location folder, so Idea will know about your tomcat server enter image description here

3) Go to Deployment tab and select Artifact. Apply enter image description here

4) In src folder put your servlet (you can try my example for testing purpose) enter image description here

5) Go to web.xml file and link your's servlet like this

enter image description here

6) In web folder put your's .jsp files (for example hey.jsp)

enter image description here

7) Now you can start you app via IntellijIdea. Run(Shift+F10) and enjoy your app in browser:

- to jsp files: http://localhost:8080/hey.jsp (or index.jsp by default)

- to servlets via virtual link you set in web.xml : http://localhost:8080/st

Array.sort() doesn't sort numbers correctly

I've tried different numbers, and it always acts as if the 0s aren't there and sorts the numbers correctly otherwise. Anyone know why?

You're getting a lexicographical sort (e.g. convert objects to strings, and sort them in dictionary order), which is the default sort behavior in Javascript:




Specifies a function that defines the sort order. If omitted, the array is sorted lexicographically (in dictionary order) according to the string conversion of each element.

In the ECMAscript specification (the normative reference for the generic Javascript), ECMA-262, 3rd ed., section, the default sort order is lexicographical, although they don't come out and say it, instead giving the steps for a conceptual sort function that calls the given compare function if necessary, otherwise comparing the arguments when converted to strings:

13. If the argument comparefn is undefined, go to step 16.
14. Call comparefn with arguments x and y.
15. Return Result(14).
16. Call ToString(x).
17. Call ToString(y).
18. If Result(16) < Result(17), return -1.
19. If Result(16) > Result(17), return 1.
20. Return +0.

Matplotlib - How to plot a high resolution graph?

For saving the graph:

matplotlib.rcParams['savefig.dpi'] = 300

For displaying the graph when you use

matplotlib.rcParams["figure.dpi"] = 100

Just add them at the top

Non-static variable cannot be referenced from a static context

It is ClassLoader responsible to load the class files.Let's see what happens when we write our own classes.

Example 1:

class StaticTest {

      static int a;
      int b;
      int c;

Now we can see that class "StaticTest" has 3 fields.But actually there is no existence of b,c member variable.But why ???. OK Lest's see. Here b,c are instance variable.Since instance variable gets the memory at the time of object creation. So here b,c are not getting any memory yet. That's why there is no existence of b,c. So There is only existence of a. For ClassLoader it has only one information about a. ClassLoader yet not recognize b,c because it's object not instantiated yet.

Let's see another example: Example 2:

class StaticTest {

      public void display() {
          System.out.println("Static Test");

      public static void main(String []cmd) {



Now if we try to compile this code compiler will give CE error. CE: non-static method display() cannot be referenced from a static context.

Now For ClassLoader it looks like:

class StaticTest {

      public static void main(String []cmd) {



In Example 2 CE error is because we call non static method from a static context. So it is not possible for ClassLoader to recognize method display() at compile time.So compile time error is occurred.

How can I get the browser's scrollbar sizes?

I made an updated version of @Matthew Vines answer.

It's easier to read, easier to understand. It doesn't require an inner element. The element created to get the scroll bar width has a 100% height/width so it doesn't create any visible scroll bar on the body on lower end PCs/mobiles which could take a bit more time to create the element, get the widths, and finally remove the element.

const getScrollBarWidth = () => {
  const e = document.createElement('div');
  Object.assign(, {
    width: '100%',
    height: '100%',
    overflow: 'scroll',
    position: 'absolute',
    visibility: 'hidden',
    top: '0',
    left: '0',


  const scrollbarWidth = e.offsetWidth - e.clientWidth;


  return scrollbarWidth;


I do recommend to check for the scroll bar width only once, at page load (except if it doesn't fit your needs) then store the result in a state/variable.

How to convert a string to ASCII

I think this code may be help you:

string str = char.ConvertFromUtf32(65)

Vector of structs initialization

You cannot access elements of an empty vector by subscript.
Always check that the vector is not empty & the index is valid while using the [] operator on std::vector.
[] does not add elements if none exists, but it causes an Undefined Behavior if the index is invalid.

You should create a temporary object of your structure, fill it up and then add it to the vector, using vector::push_back()

subject subObj; = s1;

Xcode 5.1 - No architectures to compile for (ONLY_ACTIVE_ARCH=YES, active arch=x86_64, VALID_ARCHS=i386)

I had similar issue. Got it solved by changing "Architecture" to "$(ARCHS_STANDARD_32_BIT)" in Build Settings for Project.

Now, you have to select Standard architectures (armv7, arm64) - $(ARCHS_STANDARD) since apple recommends apps to be build on 64-bit architecture. Click : Apple document

How to detect when a youtube video finishes playing?

This can be done through the youtube player API:

Working example:

    <div id="player"></div>

    <script src=""></script>


        // create youtube player
        var player;
        function onYouTubePlayerAPIReady() {
            player = new YT.Player('player', {
              width: '640',
              height: '390',
              videoId: '0Bmhjf0rKe8',
              events: {
                onReady: onPlayerReady,
                onStateChange: onPlayerStateChange

        // autoplay video
        function onPlayerReady(event) {

        // when video ends
        function onPlayerStateChange(event) {        
            if( === 0) {          


How to overlay one div over another div

Here is a simple example to bring an overlay effect with a loading icon over another div.

    #overlay {
        position: absolute;
        width: 100%;
        height: 100%;
        background: black url('icons/loading.gif') center center no-repeat; /* Make sure the path and a fine named 'loading.gif' is there */
        background-size: 50px;
        z-index: 1;
        opacity: .6;
        position: relative;
        width:400px;  /* Just for testing, remove width and height if you have content inside this div */
        height:500px; /* Remove this if you have content inside */

<h2>The overlay tester</h2>
<div class="wraper">
    <div id="overlay"></div>
    <h3>Apply the overlay over this div</h3>

Try it here:,css,output