Programs & Examples On #Javascript framework

A JavaScript framework is a library of pre-written JavaScript which allows for easier development of JavaScript-based applications, especially for AJAX and other web-centric technologies.

AngularJS passing data to $http.get request

You can even simply add the parameters to the end of the url:

$http.get('path/to/script.php?param=hello').success(function(data) {

Paired with script.php:

<? var_dump($_GET); ?>

Resulting in the following javascript alert:

array(1) {  
    string(4) "hello"

Get epoch for a specific date using Javascript

Take a look at

There is a function UTC() that returns the milliseconds from the unix epoch.

Error: 10 $digest() iterations reached. Aborting! with dynamic sortby predicate

This happened to me after upgrading from angular 1.6 -> 1.7 when using $sce.trustAsResourceUrl() as the return value of a function called from ng-src. You can see this issue mentioned here.

In my case I had to change the following.

<source ng-src="{{trustSrc(someUrl)}}" type='video/mp4' />
trustSrc = function(url){
    return $sce.trustAsResourceUrl(url);


<source ng-src='{{trustedUrl}} type='video/mp4' />
trustedUrl = $sce.trustAsResourceUrl(someUrl);

jQuery: Check if div with certain class name exists

$('div').hasClass('mydivclass')// Returns true if the class exist.

Difference between the 'controller', 'link' and 'compile' functions when defining a directive

I'm going to expand your question a bit and also include the compile function.

  • compile function - use for template DOM manipulation (i.e., manipulation of tElement = template element), hence manipulations that apply to all DOM clones of the template associated with the directive. (If you also need a link function (or pre and post link functions), and you defined a compile function, the compile function must return the link function(s) because the 'link' attribute is ignored if the 'compile' attribute is defined.)

  • link function - normally use for registering listener callbacks (i.e., $watch expressions on the scope) as well as updating the DOM (i.e., manipulation of iElement = individual instance element). It is executed after the template has been cloned. E.g., inside an <li ng-repeat...>, the link function is executed after the <li> template (tElement) has been cloned (into an iElement) for that particular <li> element. A $watch allows a directive to be notified of scope property changes (a scope is associated with each instance), which allows the directive to render an updated instance value to the DOM.

  • controller function - must be used when another directive needs to interact with this directive. E.g., on the AngularJS home page, the pane directive needs to add itself to the scope maintained by the tabs directive, hence the tabs directive needs to define a controller method (think API) that the pane directive can access/call.

    For a more in-depth explanation of the tabs and pane directives, and why the tabs directive creates a function on its controller using this (rather than on $scope), please see 'this' vs $scope in AngularJS controllers.

In general, you can put methods, $watches, etc. into either the directive's controller or link function. The controller will run first, which sometimes matters (see this fiddle which logs when the ctrl and link functions run with two nested directives). As Josh mentioned in a comment, you may want to put scope-manipulation functions inside a controller just for consistency with the rest of the framework.

What is the difference between React Native and React?

A little late to the party, but here's a more comprehensive answer with examples:


React is a component based UI library that uses a "shadow DOM" to efficiently update the DOM with what has changed instead of rebuilding the entire DOM tree for every change. It was initially built for web apps, but now can be used for mobile & 3D/vr as well.

Components between React and React Native cannot be interchanged because React Native maps to native mobile UI elements but business logic and non-render related code can be re-used.


Was initially included with the React library but was split out once React was being used for other platforms than just web. It serves as the entry point to the DOM and is used in union with React.


import React from 'react';
import ReactDOM from 'react-dom';

class App extends Component {
    state = {
        data: [],

    componentDidMount() {
        const data = API.getData(); // fetch some data
        this.setState({ data })

    clearData = () => {
            data: [],

    render() {
        return (
                { => (
                    <p key={}>{data.label}</p>
                <button onClick={this.clearData}>
                    Clear list


ReactDOM.render(App, document.getElementById('app'));

React Native

React Native is a cross-platform mobile framework that uses React and communicates between Javascript and it's native counterpart via a "bridge". Due to this, a lot of UI structuring has to be different when using React Native. For example: when building a list, you will run into major performance issues if you try to use map to build out the list instead of React Native's FlatList. React Native can be used to build out IOS/Android mobile apps, as well as for smart watches and TV's.


Expo is the go-to when starting a new React Native app.

Expo is a framework and a platform for universal React applications. It is a set of tools and services built around React Native and native platforms that help you develop, build, deploy, and quickly iterate on iOS, Android, and web apps

Note: When using Expo, you can only use the Native Api's they provide. All additional libraries you include will need to be pure javascript or you will need to eject expo.

Same example using React Native:

import React, { Component } from 'react';
import { Flatlist, View, Text, StyleSheet } from 'react-native';

export default class App extends Component {
    state = {
        data: [],

    componentDidMount() {
        const data = API.getData(); // fetch some data
        this.setState({ data })

    clearData = () => {
            data: [],

    render() {
        return (
            <View style={styles.container}>
                    renderItem={({ item }) => <Text key={}>{item.label}</Text>}
                <Button title="Clear list" onPress={this.clearData}></Button>


const styles = StyleSheet.create({
    container: {
        flex: 1,


  • Notice that everything outside of render can remain the same, this is why business logic/lifecycle logic code can be re-used across React and React Native
  • In React Native all components need to be imported from react-native or another UI library
  • Using certain API's that map to native components are usually going to be more performant than trying to handle everything on the javascript side. ex. mapping components to build a list vs using flatlist
  • Subtle differences: things like onClick turn into onPress, React Native uses stylesheets to define styles in a more performant way, and React Native uses flexbox as the default layout structure to keep things responsive.
  • Since there is no traditional "DOM" in React Native, only pure javascript libraries can be used across both React and React Native


It's also worth mentioning that React can also be used to develop 3D/VR applications. The component structure is very similar to React Native.

Angular JS break ForEach

Concretely, you can exit of a forEach loop, and of any place, throw an exception.

try {
   angular.forEach([1,2,3], function(num) {
      if (num === 2) throw Error();
} catch(e) {
    // anything

However, it is better if you use other library or implement your own function, a find function in this case, so your code is most high-level.

AngularJs ReferenceError: $http is not defined

I have gone through the same problem when I was using

    myApp.controller('mainController', ['$scope', function($scope,) {
        //$http was not working in this

I have changed the above code to given below. Remember to include $http(2 times) as given below.

 myApp.controller('mainController', ['$scope','$http', function($scope,$http) {
      //$http is working in this

and It has worked well.

How to generate UL Li list from string array using jquery?

It's possible without jQuery too! :)

let countries = ['United States', 'Canada', 'Argentina', 'Armenia', 'Aruba'];_x000D_
// The <ul> that we will add <li> elements to:_x000D_
let myList = document.querySelector('ul.mylist');_x000D_
// Loop over the Array of country names:_x000D_
countries.forEach(function(value, index, array) {_x000D_
  // Create an <li> element:_x000D_
  let li = document.createElement('li');_x000D_
  // Give it the desired classes & attributes:_x000D_
  li.setAttribute('role', 'menuitem');_x000D_
  // Now create an <a> element:_x000D_
  let a = document.createElement('a');_x000D_
  // Give it the desired classes & attributes:_x000D_
  a.tabIndex = -1;_x000D_
  a.innerText = value; //  <--- the country name from our Array_x000D_
  a.href = "#"_x000D_
  // Now add the <a> to the <li>, and add the <li> to the <ul>_x000D_
<ul class="mylist"></ul>

How to create a jQuery plugin with methods?

Here I want to suggest steps to create simple plugin with arguments.

(function($) {_x000D_
  $.fn.myFirstPlugin = function(options) {_x000D_
    // Default params_x000D_
    var params = $.extend({_x000D_
      text     : 'Default Title',_x000D_
      fontsize : 10,_x000D_
    }, options);_x000D_
    return $(this).text(params.text);_x000D_
$('.cls-title').myFirstPlugin({ text : 'Argument Title' });
<script src=""></script>_x000D_
<h1 class="cls-title"></h1>

Here, we have added default object called params and set default values of options using extend function. Hence, If we pass blank argument then it will set default values instead otherwise it will set.

Read more: How to Create JQuery plugin

Pass variables to AngularJS controller, best practice?

You could use ng-init in an outer div:

<div ng-init="param='value';">
    <div ng-controller="BasketController" >
        <label>param: {{value}}</label>

The parameter will then be available in your controller's scope:

function BasketController($scope) {

How to get an element by its href in jquery?

Yes, you can use jQuery's attribute selector for that.

var linksToGoogle = $('a[href=""]');

Alternatively, if your interest is rather links starting with a certain URL, use the attribute-starts-with selector:

var allLinksToGoogle = $('a[href^=""]');

VBA - Range.Row.Count

You could also use the "Last" function from Ron de Bruin (, it worked perfectly for me and also gives back the last column and cell if you want. To get the last row use it like

lastRow = Last(1,yourRange)

I found this quite handy.

Function Last(choice As Long, rng As Range)
'Ron de Bruin, 5 May 2008
' 1 = last row
' 2 = last column
' 3 = last cell
    Dim lrw As Long
    Dim lcol As Long

    Select Case choice

    Case 1:
        On Error Resume Next
        Last = rng.Find(What:="*", _
                        After:=rng.Cells(1), _
                        Lookat:=xlPart, _
                        LookIn:=xlFormulas, _
                        SearchOrder:=xlByRows, _
                        SearchDirection:=xlPrevious, _
        On Error GoTo 0

    Case 2:
        On Error Resume Next
        Last = rng.Find(What:="*", _
                        After:=rng.Cells(1), _
                        Lookat:=xlPart, _
                        LookIn:=xlFormulas, _
                        SearchOrder:=xlByColumns, _
                        SearchDirection:=xlPrevious, _
        On Error GoTo 0

    Case 3:
        On Error Resume Next
        lrw = rng.Find(What:="*", _
                       After:=rng.Cells(1), _
                       Lookat:=xlPart, _
                       LookIn:=xlFormulas, _
                       SearchOrder:=xlByRows, _
                       SearchDirection:=xlPrevious, _
        On Error GoTo 0

        On Error Resume Next
        lcol = rng.Find(What:="*", _
                        After:=rng.Cells(1), _
                        Lookat:=xlPart, _
                        LookIn:=xlFormulas, _
                        SearchOrder:=xlByColumns, _
                        SearchDirection:=xlPrevious, _
        On Error GoTo 0

        On Error Resume Next
        Last = rng.Parent.Cells(lrw, lcol).Address(False, False)
        If Err.Number > 0 Then
            Last = rng.Cells(1).Address(False, False)
        End If
        On Error GoTo 0

    End Select
End Function

Setting unique Constraint with fluent API?

modelBuilder.Property(x => x.FirstName).IsUnicode().IsRequired().HasMaxLength(50);

How do I compare 2 rows from the same table (SQL Server)?

OK, after 2 years it's finally time to correct the syntax:

SELECT  t1.value, t2.value
FROM    MyTable t1
JOIN    MyTable t2
ON =
WHERE = @id
        AND t1.status = @status1
        AND t2.status = @status2

Two column div layout with fluid left and fixed right column

Here's a solution (and it has some quirks, but let me know if you notice them and that they're a concern):

    <div style="width:200px;float:left;display:inline-block;">
        Hello world
    <div style="margin-left:200px;">
        Hello world

"int cannot be dereferenced" in Java

Basically, you're trying to use int as if it was an Object, which it isn't ('s complicated)


Should be...

id == list[pos].getItemNumber()

Avoid "current URL string parser is deprecated" warning by setting useNewUrlParser to true

The following work for me for the mongoose version 5.9.16

const mongoose = require('mongoose');

mongoose.set('useNewUrlParser', true);
mongoose.set('useFindAndModify', false);
mongoose.set('useCreateIndex', true);
mongoose.set('useUnifiedTopology', true);

    .then(() => console.log('Connect to MongoDB..'))
    .catch(err => console.error('Could not connect to MongoDB..', err))

An efficient way to Base64 encode a byte array?

You could use the String Convert.ToBase64String(byte[]) to encode the byte array into a base64 string, then Byte[] Convert.FromBase64String(string) to convert the resulting string back into a byte array.

How to use ADB in Android Studio to view an SQLite DB

Easiest Way: Connect to Sqlite3 via ADB Shell

I haven't found any way to do that in Android Studio, but I access the db with a remote shell instead of pulling the file each time.

Find all info here:

1- Go to your platform-tools folder in a command prompt

2- Enter the command adb devices to get the list of your devices

C:\Android\adt-bundle-windows-x86_64\sdk\platform-tools>adb devices
List of devices attached
emulator-xxxx   device

3- Connect a shell to your device:

C:\Android\adt-bundle-windows-x86_64\sdk\platform-tools>adb -s emulator-xxxx shell

4a- You can bypass this step on rooted device

run-as <your-package-name> 

4b- Navigate to the folder containing your db file:

cd data/data/<your-package-name>/databases/

5- run sqlite3 to connect to your db:

sqlite3 <your-db-name>.db

6- run sqlite3 commands that you like eg:

Select * from table1 where ...;

Note: Find more commands to run below.

SQLite cheatsheet

There are a few steps to see the tables in an SQLite database:

  1. List the tables in your database:

  2. List how the table looks:

    .schema tablename
  3. Print the entire table:

    SELECT * FROM tablename;
  4. List all of the available SQLite prompt commands:


Fill DataTable from SQL Server database

If the variable table contains invalid characters (like a space) you should add square brackets around the variable.

public DataTable fillDataTable(string table)
    string query = "SELECT * FROM dstut.dbo.[" + table + "]";

    using(SqlConnection sqlConn = new SqlConnection(conSTR))
    using(SqlCommand cmd = new SqlCommand(query, sqlConn))
        DataTable dt = new DataTable();
        return dt;

By the way, be very careful with this kind of code because is open to Sql Injection. I hope for you that the table name doesn't come from user input

No server in Eclipse; trying to install Tomcat

You can install Tomcat server form Eclipse market place.

Help -> Eclipse Market Place search for 'Tomcat' -> Install Eclipse Tomcat plugin.

enter image description here

After installation restart eclipse.

Stop an input field in a form from being submitted

$('#serialize').click(function () {_x000D_
$('#exclude').change(function () {_x000D_
  if ($(this).is(':checked')) {_x000D_
    $('[name=age]').attr('form', 'fake-form-id');_x000D_
  } else {_x000D_
    $('[name=age]').removeAttr('form');    _x000D_
<script src=""></script>_x000D_
<form action="/">_x000D_
  <input type="text" value="John" name="name">_x000D_
  <input type="number" value="100" name="age">_x000D_
<input type="button" value="serialize" id="serialize">_x000D_
<label for="exclude">  _x000D_
  <input type="checkbox" value="exclude age" id="exclude">_x000D_
  exlude age_x000D_
<pre id="out"></pre>

What is the correct format to use for Date/Time in an XML file

If you are manually assembling the XML string use var.ToUniversalTime().ToString("yyyy-MM-dd'T'HH:mm:ss.fffffffZ")); That will output the official XML Date Time format. But you don't have to worry about format if you use the built-in serialization methods.

Convert a string date into datetime in Oracle

Try this: TO_DATE('2011-07-28T23:54:14Z', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')

How to resolve cURL Error (7): couldn't connect to host?

In my case I had something like cURL Error (7): ... Operation Timed Out. I'm using the network connection of the company I'm working for. I needed to create some environment variables. The next worked for me:

In Linux terminal:

$ export https_proxy=yourProxy:80
$ export http_proxy=yourProxy:80  

In windows I created (the same) environment variables in the windows way.

I hope it helps!


How to add hours to current time in python

Import datetime and timedelta:

>>> from datetime import datetime, timedelta
>>> str( + timedelta(hours=9))[11:19]

But the better way is:

>>> ( + timedelta(hours=9)).strftime('%H:%M:%S')

You can refer strptime and strftime behavior to better understand how python processes dates and time field

Correct MIME Type for favicon.ico?

When you're serving an .ico file to be used as a favicon, it doesn't matter. All major browsers recognize both mime types correctly. So you could put:

<!-- IE -->
<link rel="shortcut icon" type="image/x-icon" href="favicon.ico" />
<!-- other browsers -->
<link rel="icon" type="image/x-icon" href="favicon.ico" />

or the same with image/, and it will work with all browsers.

Note: There is no IANA specification for the MIME-type image/x-icon, so it does appear that it is a little more unofficial than image/

The only case in which there is a difference is if you were trying to use an .ico file in an <img> tag (which is pretty unusual). Based on previous testing, some browsers would only display .ico files as images when they were served with the MIME-type image/x-icon. More recent tests show: Chromium, Firefox and Edge are fine with both content types, IE11 is not. If you can, just avoid using ico files as images, use png.

Add a link to an image in a css style sheet

You don't add links to style sheets. They are for describing the style of the page. You would change your mark-up or add JavaScript to navigate when the image is clicked.

Based only on your style you would have:

<a href="" id="logo"></a>

running a command as a super user from a python script

You have to use Popen like this:

cmd = ['sudo', 'apache2ctl', 'restart']
proc = subprocess.Popen(cmd, shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

It expects a list.

How to set a default value for an existing column

This will work in SQL Server:


Can "list_display" in a Django ModelAdmin display attributes of ForeignKey fields?

Like the rest, I went with callables too. But they have one downside: by default, you can't order on them. Fortunately, there is a solution for that:

Django >= 1.8

def author(self, obj):
author.admin_order_field  = 'book__author'

Django < 1.8

def author(self):
author.admin_order_field  = 'book__author'

Proper use of the IDisposable interface

In the example you posted, it still doesn't "free the memory now". All memory is garbage collected, but it may allow the memory to be collected in an earlier generation. You'd have to run some tests to be sure.

The Framework Design Guidelines are guidelines, and not rules. They tell you what the interface is primarily for, when to use it, how to use it, and when not to use it.

I once read code that was a simple RollBack() on failure utilizing IDisposable. The MiniTx class below would check a flag on Dispose() and if the Commit call never happened it would then call Rollback on itself. It added a layer of indirection making the calling code a lot easier to understand and maintain. The result looked something like:

using( MiniTx tx = new MiniTx() )
    // code that might not work.


I've also seen timing / logging code do the same thing. In this case the Dispose() method stopped the timer and logged that the block had exited.

using( LogTimer log = new LogTimer("MyCategory", "Some message") )
    // code to time...

So here are a couple of concrete examples that don't do any unmanaged resource cleanup, but do successfully used IDisposable to create cleaner code.

Efficient way to remove ALL whitespace from String?

Just an alternative because it looks quite nice :) - NOTE: Henks answer is the quickest of these.

 .Where(c => !Char.IsWhiteSpace(c))
 .Select(c => c.ToString())
 .Aggregate((a, b) => a + b);

Testing 1,000,000 loops on "This is a simple Test"

This method = 1.74 seconds
Regex = 2.58 seconds
new String (Henks) = 0.82 seconds

Checking whether a variable is an integer or not

If you just need the value, operator.index (__index__ special method) is the way to go in my opinion. Since it should work for all types that can be safely cast to an integer. I.e. floats fail, integers, even fancy integer classes that do not implement the Integral abstract class work by duck typing.

operator.index is what is used for list indexing, etc. And in my opinion it should be used for much more/promoted.

In fact I would argue it is the only correct way to get integer values if you want to be certain that floating points, due to truncating problems, etc. are rejected and it works with all integral types (i.e. numpy, etc.) even if they may not (yet) support the abstract class.

This is what __index__ was introduced for!

Determine the data types of a data frame's columns

For small data frames:



gives you a print out of the df with data types

# A tibble: 32 x 11
     mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb
 * <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
 1  21       6  160    110  3.9   2.62  16.5     0     1     4     4
 2  21       6  160    110  3.9   2.88  17.0     0     1     4     4
 3  22.8     4  108     93  3.85  2.32  18.6     1     1     4     1

For large data frames:


gives you a structured view of data types:

Observations: 32
Variables: 11
$ mpg  <dbl> 21.0, 21.0, 22.8, 21.4, 18.7, 18.1, 14.3, 24.4, 22.8, 19.2, 17.8, 16.4, 17....
$ cyl  <dbl> 6, 6, 4, 6, 8, 6, 8, 4, 4, 6, 6, 8, 8, 8, 8, 8, 8, 4, 4, 4, 4, 8, 8, 8, 8, ...
$ disp <dbl> 160.0, 160.0, 108.0, 258.0, 360.0, 225.0, 360.0, 146.7, 140.8, 167.6, 167.6...
$ hp   <dbl> 110, 110, 93, 110, 175, 105, 245, 62, 95, 123, 123, 180, 180, 180, 205, 215...
$ drat <dbl> 3.90, 3.90, 3.85, 3.08, 3.15, 2.76, 3.21, 3.69, 3.92, 3.92, 3.92, 3.07, 3.0...
$ wt   <dbl> 2.620, 2.875, 2.320, 3.215, 3.440, 3.460, 3.570, 3.190, 3.150, 3.440, 3.440...
$ qsec <dbl> 16.46, 17.02, 18.61, 19.44, 17.02, 20.22, 15.84, 20.00, 22.90, 18.30, 18.90...
$ vs   <dbl> 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, ...
$ am   <dbl> 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, ...
$ gear <dbl> 4, 4, 4, 3, 3, 3, 3, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 4, 4, 4, 3, 3, 3, 3, 3, ...
$ carb <dbl> 4, 4, 1, 1, 2, 1, 4, 2, 2, 4, 4, 3, 3, 3, 4, 4, 4, 1, 2, 1, 1, 2, 2, 4, 2, ...

To get a list of the columns' data type (as said by @Alexandre above):

map(mtcars, class)

gives a list of data types:

[1] "numeric"

[1] "numeric"

[1] "numeric"

[1] "numeric"

To change data type of a column:


mtcars %>% 
  convert(chr(mpg, am),

converts columns mpg and am to character and the column carb to integer:

# A tibble: 32 x 11
   mpg     cyl  disp    hp  drat    wt  qsec    vs am     gear  carb
   <chr> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <chr> <dbl> <int>
 1 21        6  160    110  3.9   2.62  16.5     0 1         4     4
 2 21        6  160    110  3.9   2.88  17.0     0 1         4     4
 3 22.8      4  108     93  3.85  2.32  18.6     1 1         4     1
 4 21.4      6  258    110  3.08  3.22  19.4     1 0         3     1

PHP shell_exec() vs exec()

A couple of distinctions that weren't touched on here:

  • With exec(), you can pass an optional param variable which will receive an array of output lines. In some cases this might save time, especially if the output of the commands is already tabular.


exec('ls', $out);
// Look an array

$out = shell_exec('ls');
// Look -- a string with newlines in it

Conversely, if the output of the command is xml or json, then having each line as part of an array is not what you want, as you'll need to post-process the input into some other form, so in that case use shell_exec.

It's also worth pointing out that shell_exec is an alias for the backtic operator, for those used to *nix.

$out = `ls`;

exec also supports an additional parameter that will provide the return code from the executed command:

exec('ls', $out, $status);
if (0 === $status) {
} else {
    echo "Command failed with status: $status";

As noted in the shell_exec manual page, when you actually require a return code from the command being executed, you have no choice but to use exec.

Error occurred during initialization of VM Could not reserve enough space for object heap Could not create the Java virtual machine

If your computer is a 64bit, all you need to do is uninstall your Java x86 version and install a 64bit version. I had the same problem and this worked. Nothing further needs to be done.

Visual Studio Code open tab in new window

When I want to split the screens I usually do one of the following:

  1. open new window with: Ctrl+Shift+N
    and after that I drag the current file I want to the new window.
  2. on the File explorer - I hit Ctrl+Enter on the file I want - and then this file and the other file open together in the same screen but in split mode, so you can see the two files together. If the screen is wide enough this is not a bad solution at all that you can get used to.

How to remove illegal characters from path and filenames?

If you have to use the method in many places in a project, you could also make an extension method and call it anywhere in the project for strings.

 public static class StringExtension
        public static string RemoveInvalidChars(this string originalString)
            string finalString=string.Empty;
            if (!string.IsNullOrEmpty(originalString))
                return string.Concat(originalString.Split(Path.GetInvalidFileNameChars()));
            return finalString;            

You can call the above extension method as:

string illegal = "\"M<>\"\\a/ry/ h**ad:>> a\\/:*?\"<>| li*tt|le|| la\"mb.?";
string afterIllegalChars = illegal.RemoveInvalidChars();

Python display text with font & color?

Yes. It is possible to draw text in pygame:

# initialize font; must be called after 'pygame.init()' to avoid 'Font not Initialized' error
myfont = pygame.font.SysFont("monospace", 15)

# render text
label = myfont.render("Some text!", 1, (255,255,0))
screen.blit(label, (100, 100))

How to give spacing between buttons using bootstrap

You can achieved by use bootstrap Spacing. Bootstrap Spacing includes a wide range of shorthand responsive margin and padding. In below example mr-1 set the margin or padding to $spacer * .25.


<button class="btn btn-outline-primary mr-1" href="#">Sign up</button>
<button class="btn btn-outline-primary" href="#">Login</button>

You can read more at Bootstrap Spacing.

Change Color of Fonts in DIV (CSS)

Your first CSS selector—social.h2—is looking for the "social" element in the "h2", class, e.g.:

<social class="h2">

Class selectors are proceeded with a dot (.). Also, use a space () to indicate that one element is inside of another. To find an <h2> descendant of an element in the social class, try something like:

.social h2 {
  color: pink;
  font-size: 14px;

To get a better understanding of CSS selectors and how they are used to reference your HTML, I suggest going through the interactive HTML and CSS tutorials from CodeAcademy. I hope that this helps point you in the right direction.

Bootstrap carousel resizing image

add this to your css:

.carousel-inner > .item > img, .carousel-inner > .item > a > img {
    width: 100%;

How to split strings into text and number?

>>> def mysplit(s):
...     head = s.rstrip('0123456789')
...     tail = s[len(head):]
...     return head, tail
>>> [mysplit(s) for s in ['foofo21', 'bar432', 'foobar12345']]
[('foofo', '21'), ('bar', '432'), ('foobar', '12345')]

Is it possible to use the SELECT INTO clause with UNION [ALL]?

SELECT * INTO tmpFerdeen FROM 
(SELECT top(100)*  
FROM Customers 
SELECT top(100)*  
FROM CustomerEurope 
SELECT top(100)*  
FROM CustomerAsia 
SELECT top(100)*  
FROM CustomerAmericas) AS Blablabal

This "Blablabal" is necessary

How to install packages offline?

For Pip 8.1.2 you can use pip download -r requ.txt to download packages to your local machine.

How do I create a user with the same privileges as root in MySQL/MariaDB?

% mysql --user=root mysql
CREATE USER 'monty'@'localhost' IDENTIFIED BY 'some_pass';
CREATE USER 'monty'@'%' IDENTIFIED BY 'some_pass';
CREATE USER 'admin'@'localhost';
GRANT RELOAD,PROCESS ON *.* TO 'admin'@'localhost';
CREATE USER 'dummy'@'localhost';

Refresh Excel VBA Function Results

If you include ALL references to the spreadsheet data in the UDF parameter list, Excel will recalculate your function whenever the referenced data changes:

Public Function doubleMe(d As Variant)
    doubleMe = d * 2
End Function

You can also use Application.Volatile, but this has the disadvantage of making your UDF always recalculate - even when it does not need to because the referenced data has not changed.

Public Function doubleMe()
    doubleMe = Worksheets("Fred").Range("A1") * 2
End Function

Detect all changes to a <input type="text"> (immediately) using JQuery

Add this code somewhere, this will do the trick.

var originalVal = $.fn.val;
$.fn.val = function(){
    var result =originalVal.apply(this,arguments);
        $(this).change(); // OR with custom event $(this).trigger('value-changed');
    return result;

Found this solution at val() doesn't trigger change() in jQuery


Use the WebRequest class

This is to get an image:

    Dim _WebRequest As System.Net.WebRequest = Nothing
    _WebRequest = System.Net.WebRequest.Create(
Catch ex As Exception
    Exit Sub
End Try

    _NormalImage = Image.FromStream(_WebRequest.GetResponse().GetResponseStream())
Catch ex As Exception
    Exit Sub
End Try

substring index range

public class SubstringExample
    public static void main(String[] args) 
        String str="OOPs is a programming paradigm...";

        System.out.println(" Length is: " + str.length());

        System.out.println(" Substring is: " + str.substring(10, 30));


length is: 31

Substring is: programming paradigm

How do I redirect to another webpage?

One does not simply redirect using jQuery

jQuery is not necessary, and window.location.replace(...) will best simulate an HTTP redirect.

window.location.replace(...) is better than using window.location.href, because replace() does not keep the originating page in the session history, meaning the user won't get stuck in a never-ending back-button fiasco.

If you want to simulate someone clicking on a link, use location.href

If you want to simulate an HTTP redirect, use location.replace

For example:

// similar behavior as an HTTP redirect

// similar behavior as clicking on a link
window.location.href = "";

JavaScript: How to pass object by value?

Here is clone function that will perform deep copy of the object:

function clone(obj){
    if(obj == null || typeof(obj) != 'object')
        return obj;

    var temp = new obj.constructor(); 
    for(var key in obj)
        temp[key] = clone(obj[key]);

    return temp;

Now you can you use like this:

    var obj = clone(x); = 'foo'; = 'bar';

How do you set your pythonpath in an already-created virtualenv?

It's already answered here -> Is my virtual environment (python) causing my PYTHONPATH to break?


Add "export PYTHONPATH=/usr/local/lib/python2.0" this to ~/.bashrc file and source it by typing "source ~/.bashrc" OR ". ~/.bashrc".


1) Go to the Control panel 2) Double click System 3) Go to the Advanced tab 4) Click on Environment Variables

In the System Variables window, check if you have a variable named PYTHONPATH. If you have one already, check that it points to the right directories. If you don't have one already, click the New button and create it.


Alternatively, you can also do below your code:-

import sys

PHP PDO returning single row

Thanks to Steven's suggestion to use fetchColumn, here's my recommendation to cut short one line from your code.

$DBH = new PDO( "connection string goes here" );
$STH = $DBH->query( "select figure from table1" );
$result = $STH->fetchColumn();
echo $result;
$DBH = null;

How to load a resource from WEB-INF directory of a web archive

The problem I had accessing the sqlite db file I created in my java (jersey) server had solely to due with path. Some of the docs say the jdbc connect url should look like "jdbc:sqlite://path-to-file/sample.db". I thought the double-slash was part of a htt protocol-style path and would map properly when deployed, but in actuality, it's an absolute or relative path. So, when I placed the file at the root of the WebContent folder (tomcat project), a uri like this worked "jdbc:sqlite:sample.db".

The one thing that was throwing me was that when I was stepping through the debugger, I received a message that said "opening db: ... permission denied". I thought it was a matter of file system permissions or perhaps sql user permissions. After finding out that SQLite doesn't have the concept of roles/permissions like MySQL, etc, I did eventually change the file permissions before I came to what I believe was the correct solution, but I think it was just a bad message (i.e. permission denied, instead of File not found).

Hope this helps someone.

When to use pthread_exit() and when to use pthread_join() in Linux?

Using pthread_exit in the main thread(in place of pthread_join), will leave the main thread in defunct(zombie) state. Since not using pthread_join, other joinable threads which are terminated will also remain in the zombie state and cause resource leakage.

Failure to join with a thread that is joinable (i.e., one that is not detached), produces a "zombie thread". Avoid doing this, since each zombie thread consumes some system resources, and when enough zombie threads have accumulated, it will no longer be possible to create new threads (or processes).

Another point is keeping the main thread in the defunct state, while other threads are running may cause implementation dependent issues in various conditions like if resources are allocated in main thread or variables which are local to the main thread are used in other threads.

Also, all the shared resources are released only when the process exits, it's not saving any resources. So, I think using pthread_exit in place of pthread_join should be avoided.

Why use Gradle instead of Ant or Maven?

This may be a bit controversial, but Gradle doesn't hide the fact that it's a fully-fledged programming language.

Ant + ant-contrib is essentially a turing complete programming language that no one really wants to program in.

Maven tries to take the opposite approach of trying to be completely declarative and forcing you to write and compile a plugin if you need logic. It also imposes a project model that is completely inflexible. Gradle combines the best of all these tools:

  • It follows convention-over-configuration (ala Maven) but only to the extent you want it
  • It lets you write flexible custom tasks like in Ant
  • It provides multi-module project support that is superior to both Ant and Maven
  • It has a DSL that makes the 80% things easy and the 20% things possible (unlike other build tools that make the 80% easy, 10% possible and 10% effectively impossible).

Gradle is the most configurable and flexible build tool I have yet to use. It requires some investment up front to learn the DSL and concepts like configurations but if you need a no-nonsense and completely configurable JVM build tool it's hard to beat.

Is Python faster and lighter than C++?

All the slowest (>100x) usages of Python on the shootout are scientific operations that require high GFlop/s count. You should NOT use python for those anyways. The correct way to use python is to import a module that does those calculations, and then go have a relaxing afternoon with your family. That is the pythonic way :)

Python: Finding differences between elements of a list

You can use itertools.tee and zip to efficiently build the result:

from itertools import tee
# python2 only:
#from itertools import izip as zip

def differences(seq):
    iterable, copied = tee(seq)
    for x, y in zip(iterable, copied):
        yield y - x

Or using itertools.islice instead:

from itertools import islice

def differences(seq):
    nexts = islice(seq, 1, None)
    for x, y in zip(seq, nexts):
        yield y - x

You can also avoid using the itertools module:

def differences(seq):
    iterable = iter(seq)
    prev = next(iterable)
    for element in iterable:
        yield element - prev
        prev = element

All these solution work in constant space if you don't need to store all the results and support infinite iterables.

Here are some micro-benchmarks of the solutions:

In [12]: L = range(10**6)

In [13]: from collections import deque
In [15]: %timeit deque(differences_tee(L), maxlen=0)
10 loops, best of 3: 122 ms per loop

In [16]: %timeit deque(differences_islice(L), maxlen=0)
10 loops, best of 3: 127 ms per loop

In [17]: %timeit deque(differences_no_it(L), maxlen=0)
10 loops, best of 3: 89.9 ms per loop

And the other proposed solutions:

In [18]: %timeit [x[1] - x[0] for x in zip(L[1:], L)]
10 loops, best of 3: 163 ms per loop

In [19]: %timeit [L[i+1]-L[i] for i in range(len(L)-1)]
1 loops, best of 3: 395 ms per loop

In [20]: import numpy as np

In [21]: %timeit np.diff(L)
1 loops, best of 3: 479 ms per loop

In [35]: %%timeit
    ...: res = []
    ...: for i in range(len(L) - 1):
    ...:     res.append(L[i+1] - L[i])
1 loops, best of 3: 234 ms per loop

Note that:

  • zip(L[1:], L) is equivalent to zip(L[1:], L[:-1]) since zip already terminates on the shortest input, however it avoids a whole copy of L.
  • Accessing the single elements by index is very slow because every index access is a method call in python
  • numpy.diff is slow because it has to first convert the list to a ndarray. Obviously if you start with an ndarray it will be much faster:

    In [22]: arr = np.array(L)
    In [23]: %timeit np.diff(arr)
    100 loops, best of 3: 3.02 ms per loop

What is the use of the JavaScript 'bind' method?

Simple Explanation:

bind() create a new function, a new reference at a function it returns to you.

In parameter after this keyword, you pass in the parameter you want to preconfigure. Actually it does not execute immediately, just prepares for execution.

You can preconfigure as many parameters as you want.

Simple Example to understand bind:

function calculate(operation) {
  if (operation === 'ADD') {
   alert('The Operation is Addition');
  } else if (operation === 'SUBTRACT') {
   alert('The Operation is Subtraction');

addBtn.addEventListener('click', calculate.bind(this, 'ADD'));
subtractBtn.addEventListener('click', calculate.bind(this, 'SUBTRACT'));

This Activity already has an action bar supplied by the window decor

If you get the error on this line:


You need to check if your activity is referring to a theme that contains a toolbar. Your application's AppTheme might already contain a toolbar, such as

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

and you are trying to add a second one. If you want to use your application's AppTheme, you need to remove the theme from your activity, in the manifest.xml file.

For example:

    android:theme="@style/AppTheme1" /> --> remove this theme

Textarea onchange detection

The best thing that you can do is to set a function to be called on a given amount of time and this function to check the contents of your textarea.

self.setInterval('checkTextAreaValue()', 50);

Regarding Java switch statements - using return and omitting breaks in each case

I suggest you not use literals.

Other than that the style itself looks fine.

Should I use != or <> for not equal in T-SQL?

Although they function the same way, != means exactly "not equal to", while <> means greater than and less than the value stored.

Consider >= or <=, and this will make sense when factoring in your indexes to queries... <> will run faster in some cases (with the right index), but in some other cases (index free) they will run just the same.

This also depends on how your databases system reads the values != and <>. The database provider may just shortcut it and make them function the same, so there isn't any benefit either way.PostgreSQL and SQL Server do not shortcut this; it is read as it appears above.

Assembly - JG/JNLE/JL/JNGE after CMP

Wikibooks has a fairly good summary of jump instructions. Basically, there's actually two stages:

cmp_instruction op1, op2

Which sets various flags based on the result, and

jmp_conditional_instruction address

which will execute the jump based on the results of those flags.

Compare (cmp) will basically compute the subtraction op1-op2, however, this is not stored; instead only flag results are set. So if you did cmp eax, ebx that's the same as saying eax-ebx - then deciding based on whether that is positive, negative or zero which flags to set.

More detailed reference here.

How to get full path of a file?

This works with both Linux and Mac OSX ..

 echo $(pwd)$/$(ls file.txt)

how to check for null with a ng-if values in a view with angularjs?

You should check for !test, here is a fiddle showing that.

<span ng-if="!test">null</span>

NVIDIA NVML Driver/library version mismatch

reboot. If the problem still exist:

sudo rmmod nvidia_drm
sudo rmmod nvidia_modeset
sudo rmmod nvidia

for cent/rhel

cd /boot
mv initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.bak
dracut -vf initramfs-$(uname -r).img $(uname -r)



for debian/ubuntu

update-initramfs -u

if problem exist persist

apt install -y dkms && dkms install -m nvidia -v 440.82

Change 440.82 to your actual version.

tip: get the Nvidia driver version:

ls /usr/src

you will find the Nvidia driver dir such as nvidia-440.82

also you can remove all Nvidia pkg and reinstall driver again

apt purge nvidia*
apt purge *cuda*

apt list -i |grep nvidia
apt list -i |grep cuda

How to get a MemoryStream from a Stream in .NET?

byte[] fileData = null;
using (var binaryReader = new BinaryReader(Request.Files[0].InputStream))
    fileData = binaryReader.ReadBytes(Request.Files[0].ContentLength);

Show and hide divs at a specific time interval using jQuery

Heres a another take on this problem, using recursion and without using mutable variables. Also, im not using setInterval so theres no cleanup that has to be done.

Having this HTML

<section id="testimonials">
    <h2>My testimonial spinner</h2>
    <div class="testimonial">
      <p>First content</p>
    <div class="testimonial">
      <p>Second content</p>
    <div class="testimonial">
       <p>Third content</p>

Using ES2016

Here you call the function recursively and update the arguments.

  const testimonials = $('#testimonials')

  const showTestimonial = index => {


    return index === testimonials.length
      ? showTestimonial(0)
      : setTimeout(() => { showTestimonial(index + 1); }, 10000);

showTestimonial(0); // id of the first element you want to show.

Proxy Error 502 : The proxy server received an invalid response from an upstream server

The java application takes too long to respond(maybe due start-up/jvm being cold) thus you get the proxy error.

Proxy Error

The proxy server received an invalid response from an upstream server.
 The proxy server could not handle the request GET /lin/Campaignn.jsp.

As Albert Maclang said amending the http timeout configuration may fix the issue. I suspect the java application throws a 500+ error thus the apache gateway error too. You should look in the logs.

Difference Between Cohesion and Coupling

best explanation of Cohesion comes from Uncle Bob's Clean Code:

Classes should have a small number of instance variables. Each of the methods of a class should manipulate one or more of those variables. In general the more variables a method manipulates the more cohesive that method is to its class. A class in which each variable is used by each method is maximally cohesive.

In general it is neither advisable nor possible to create such maximally cohesive classes; on the other hand, we would like cohesion to be high. When cohesion is high, it means that the methods and variables of the class are co-dependent and hang together as a logical whole.

The strategy of keeping functions small and keeping parameter lists short can sometimes lead to a proliferation of instance variables that are used by a subset of methods. When this happens, it almost always means that there is at least one other class trying to get out of the larger class. You should try to separate the variables and methods into two or more classes such that the new classes are more cohesive.

rotating axis labels in R

As Maciej Jonczyk mentioned, you may also need to increase margins

par(mar=c(8,8,1,1)) # adjust as needed

Javascript get object key name

An ES6 update... though both filter and map might need customization.

Object.entries(theObj) returns a [[key, value],] array representation of an object that can be worked on using Javascript's array methods, .each(), .any(), .forEach(), .filter(), .map(), .reduce(), etc.

Saves a ton of work on iterating over parts of an object Object.keys(theObj), or Object.values() separately.

const buttons = {_x000D_
    button1: {_x000D_
        text: 'Close',_x000D_
        onclick: function(){_x000D_
    button2: {_x000D_
        text: 'OK',_x000D_
        onclick: function(){_x000D_
    button3: {_x000D_
        text: 'Cancel',_x000D_
        onclick: function(){_x000D_
list = Object.entries(buttons)_x000D_
    .filter(([key, value]) => `${key}`[value] !== 'undefined' ) //has options_x000D_
    .map(([key, value], idx) => `{${idx} {${key}: ${value}}}`)_x000D_

HttpServletRequest - Get query string parameters, no form data

The servlet API lacks this feature because it was created in a time when many believed that the query string and the message body was just two different ways of sending parameters, not realizing that the purposes of the parameters are fundamentally different.

The query string parameters ?foo=bar are a part of the URL because they are involved in identifying a resource (which could be a collection of many resources), like "all persons aged 42":

GET /persons?age=42

The message body parameters in POST or PUT are there to express a modification to the target resource(s). Fx setting a value to the attribute "hair":

PUT /persons?age=42


So it is definitely RESTful to use both query parameters and body parameters at the same time, separated so that you can use them for different purposes. The feature is definitely missing in the Java servlet API.

C++, copy set to vector

here's another alternative using vector::assign:

theVector.assign(theSet.begin(), theSet.end());

How can I use JSON data to populate the options of a select box?

Why not just make the server return the names?

["Woodland Hills", "none", "Los Angeles", "Laguna Hills"]

Then create the <option> elements using JavaScript.

    data: 'q=' + str,
    dataType: 'json',
    success: function( json ) {
        $.each(json, function(i, value) {
            $('#myselect').append($('<option>').text(value).attr('value', value));

How to properly validate input values with React.JS?

I have used redux-form and formik in the past, and recently React introduced Hook, and i have built a custom hook for it. Please check it out and see if it make your form validation much easier.



with this approach, you are no longer doing controlled input too.

example below:

import React from 'react'
import useForm from 'react-hook-form'

function App() {
  const { register, handleSubmit, errors } = useForm() // initialise the hook
  const onSubmit = (data) => { console.log(data) } // callback when validation pass

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input name="firstname" ref={register} /> {/* register an input */}

      <input name="lastname" ref={register({ required: true })} /> {/* apply required validation */}
      {errors.lastname && 'Last name is required.'} {/* error message */}

      <input name="age" ref={register({ pattern: /\d+/ })} /> {/* apply a Refex validation */}
      {errors.age && 'Please enter number for age.'} {/* error message */}

      <input type="submit" />

Setting the Vim background colors

In a terminal emulator like konsole or gnome-terminal, you should to set a 256 color setting for vim.

:set  t_Co=256

After that you can to change your background.

How to unzip gz file using Python

Not an exact answer because you're using xml data and there is currently no pd.read_xml() function (as of v0.23.4), but pandas (starting with v0.21.0) can uncompress the file for you! Thanks Wes!

import pandas as pd
import os
fn = '../data/file_to_load.json.gz'
df = pd.read_json(fn, lines=True, compression='gzip')

How to use BOOLEAN type in SELECT statement

You can definitely get Boolean value from a SELECT query, you just can't use a Boolean data-type.

You can represent a Boolean with 1/0.

CASE WHEN (10 > 0) THEN 1  ELSE 0 END (It can be used in SELECT QUERY)


Returns, 1 (in Hibernate/Mybatis/etc 1 is true). Otherwise, you can get printable Boolean values from a SELECT.


This returns the string 'true'.

Copy a file in a sane, safe and efficient way

Qt has a method for copying files:

#include <QFile>

Note that to use this you have to install Qt (instructions here) and include it in your project (if you're using Windows and you're not an administrator, you can download Qt here instead). Also see this answer.

How do I align a label and a textarea?

You need to put them both in some container element and then apply the alignment on it.

For example:

.formfield * {_x000D_
  vertical-align: middle;_x000D_
<p class="formfield">_x000D_
  <label for="textarea">Label for textarea</label>_x000D_
  <textarea id="textarea" rows="5">Textarea</textarea>_x000D_

Can a html button perform a POST request?

You can:

  • Either, use an <input type="submit" ..>, instead of that button.
  • or, Use a bit of javascript, to get a hold of form object (using name or id), and call submit(..) on it. Eg: form.submit(). Attach this code to the button click event. This will serialise the form parameters and execute a GET or POST request as specified in the form's method attribute.

How to convert an enum type variable to a string?

My own preference is to minimize both repetitive typing and hard to understand macros and to avoid introducing macro definitions into the general compiler space.

So, in the header file:

enum Level{
        * zero reserved for internal use
        verbose = 1,

static Level readLevel(const char *);

and the cpp implementation is:

 Logger::Level Logger::readLevel(const char *in) { 
 #  define MATCH(x) if (strcmp(in,#x) ==0) return x; 
 # undef MATCH
    std::string s("No match for logging level ");
    s += in;
    throw new std::domain_error(s);

Note the #undef of the macro as soon we're done with it.

Parsing ISO 8601 date in Javascript

Maybe, you can use moment.js which in my opinion is the best JavaScript library for parsing, formatting and working with dates client-side. You could use something like:

var momentDate = moment('1890-09-30T23:59:59+01:16:20', 'YYYY-MM-DDTHH:mm:ss+-HH:mm:ss');_x000D_
var jsDate = momentDate.toDate();_x000D_
// Now, you can run any JavaScript Date method_x000D_

The advantage of using a library like moment.js is that your code will work perfectly even in legacy browsers like IE 8+.

Here is the documenation about parsing methods:

How to apply a CSS class on hover to dynamically generated submit buttons?

You have two options:

  1. Extend your .paging class definition:

    .paging:hover {
        border:1px solid #999;
  2. Use the DOM hierarchy to apply the CSS style:

    div.paginate input:hover {
        border:1px solid #999;

Sort Pandas Dataframe by Date

You can use pd.to_datetime() to convert to a datetime object. It takes a format parameter, but in your case I don't think you need it.

>>> import pandas as pd
>>> df = pd.DataFrame( {'Symbol':['A','A','A'] ,
>>> df
         Date Symbol
0  02/20/2015      A
1  01/15/2016      A
2  08/21/2015      A
>>> df['Date'] =pd.to_datetime(df.Date)
>>> df.sort('Date') # This now sorts in date order
        Date Symbol
0 2015-02-20      A
2 2015-08-21      A
1 2016-01-15      A

For future search, you can change the sort statement:

>>> df.sort_values(by='Date') # This now sorts in date order
        Date Symbol
0 2015-02-20      A
2 2015-08-21      A
1 2016-01-15      A

Check if TextBox is empty and return MessageBox?

Use something such as the following:

if (String.IsNullOrEmpty(MaterialTextBox.Text)) 

How to generate .angular-cli.json file in Angular Cli?

I found similar error it was located to C:\Users\sony\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@schematics\angular\workspace\files

it is installed in windows try to search in c drive angular.json you will view the file

node-request - Getting error "SSL23_GET_SERVER_HELLO:unknown protocol"

in my case (the website SSL uses ev curves) the issue with the SSL was solved by adding this option ecdhCurve: 'P-521:P-384:P-256'

request({ url, 
   agentOptions: { ecdhCurve: 'P-521:P-384:P-256', }
}, (err,res,body) => {

JFYI, maybe this will help someone

Passing array in GET for a REST call


is fine. It's pretty much your only sensible option since you can't pass in a body with a GET.

ModelState.IsValid == false, why?

The ModelState property on the controller is actually a ModelStateDictionary object. You can iterate through the keys on the dictionary and use the IsValidField method to check if that particular field is valid.

Change url query string value using jQuery

If you only need to modify the page num you can replace it:

var newUrl = location.href.replace("page="+currentPageNum, "page="+newPageNum);

How can I read an input string of unknown length?

Enter while securing an area dynamically


#include <stdio.h>
#include <stdlib.h>

char *inputString(FILE* fp, size_t size){
//The size is extended by the input with the value of the provisional
    char *str;
    int ch;
    size_t len = 0;
    str = realloc(NULL, sizeof(*str)*size);//size is start size
    if(!str)return str;
    while(EOF!=(ch=fgetc(fp)) && ch != '\n'){
            str = realloc(str, sizeof(*str)*(size+=16));
            if(!str)return str;

    return realloc(str, sizeof(*str)*len);

int main(void){
    char *m;

    printf("input string : ");
    m = inputString(stdin, 10);
    printf("%s\n", m);

    return 0;

How to check whether a string is a valid HTTP URL?

Uri uri = null;
if (!Uri.TryCreate(url, UriKind.Absolute, out uri) || null == uri)
    return false;
    return true;

Here url is the string you have to test.

What is the difference between a deep copy and a shallow copy?

A shallow copy constructs a new compound object and insert its references into it to the original object.

Unlike shallow copy, deepcopy constructs new compound object and also inserts copies of the original objects of original compound object.

Lets take an example.

import copy
x =[1,[2]]
z= copy.deepcopy(x)
print(y is z)

Above code prints FALSE.

Let see how.

Original compound object x=[1,[2]] (called as compound because it has object inside object (Inception))

enter image description here

as you can see in the image, there is a list inside list.

Then we create a shallow copy of it using y = copy.copy(x). What python does here is, it will create a new compound object but objects inside them are pointing to the orignal objects.

enter image description here

In the image it has created a new copy for outer list. but the inner list remains same as the original one.

Now we create deepcopy of it using z = copy.deepcopy(x). what python does here is, it will create new object for outer list as well as inner list. as shown in the image below (red highlighted).

enter image description here

At the end code prints False, as y and z are not same objects.


Variable not accessible when initialized outside function

A global variable would be best expressed in an external JavaScript file:

var system_status;

Make sure that this has not been used anywhere else. Then to access the variable on your page, just reference it as such. Say, for example, you wanted to fill in the results on a textbox,

document.getElementById("textbox1").value = system_status;

To ensure that the object exists, use the document ready feature of jQuery.


$(function() {
    $("#textbox1")[0].value = system_status;

How to set Java environment path in Ubuntu

Java is typically installed in /usr/java locate the version you have and then do the following:

Assuming you are using bash (if you are just starting off, i recommend bash over other shells) you can simply type in bash to start it.

Edit your ~/.bashrc file and add the paths as follows:

for eg. vi ~/.bashrc

insert following lines:

export JAVA_HOME=/usr/java/<your version of java>
export PATH=${PATH}:${JAVA_HOME}/bin

after you save the changes, exit and restart your bash or just type in bash to start a new shell

Type in export to ensure paths are right.

Type in java -version to ensure Java is accessible.

Various ways to remove local Git changes

First of all check is your important change saved or not by:

$ git status

than try

$ git reset --hard

it will reset your branch to default

but if you need just undo:

$ edit (1) $ git add frotz.c filfre.c $ mailx (2) $ git reset
(3) $ git pull git:// nitfol


What is the non-jQuery equivalent of '$(document).ready()'?

There is a standards based replacement,DOMContentLoaded that is supported by over 90%+ of browsers, but not IE8 (So below code use by JQuery for browser support):

document.addEventListener("DOMContentLoaded", function(event) { 
  //do work

jQuery's native function is much more complicated than just window.onload, as depicted below.

function bindReady(){
    if ( readyBound ) return;
    readyBound = true;

    // Mozilla, Opera and webkit nightlies currently support this event
    if ( document.addEventListener ) {
        // Use the handy event callback
        document.addEventListener( "DOMContentLoaded", function(){
            document.removeEventListener( "DOMContentLoaded", arguments.callee, false );
        }, false );

    // If IE event model is used
    } else if ( document.attachEvent ) {
        // ensure firing before onload,
        // maybe late but safe also for iframes
        document.attachEvent("onreadystatechange", function(){
            if ( document.readyState === "complete" ) {
                document.detachEvent( "onreadystatechange", arguments.callee );

        // If IE and not an iframe
        // continually check to see if the document is ready
        if ( document.documentElement.doScroll && window == ) (function(){
            if ( jQuery.isReady ) return;

            try {
                // If IE is used, use the trick by Diego Perini
            } catch( error ) {
                setTimeout( arguments.callee, 0 );

            // and execute any waiting functions

    // A fallback to window.onload, that will always work
    jQuery.event.add( window, "load", jQuery.ready );

Jenkins "Console Output" log location in filesystem

You can install this Jenkins Console log plugin to write the log in your workspace as a post build step.

You have to build the plugin yourself and install the plugin manually.

Next, you can add a post build step like that:

enter image description here

With an additional post build step (shell script), you will be able to grep your log.

I hope it helped :)

sqlplus: error while loading shared libraries: cannot open shared object file: No such file or directory

I did solve this error by setting


yes, not only $ORACLE_HOME/lib but $ORACLE_HOME too.

How to query a CLOB column in Oracle

If it's a CLOB why can't we to_char the column and then search normally ?

Create a table

CREATE TABLE MY_TABLE(Id integer PRIMARY KEY, Name varchar2(20), message clob);

Create few records in this table

INSERT INTO MY_TABLE VALUES(1,'Tom','Hi This is Row one');
INSERT INTO MY_TABLE VALUES(2,'Lucy', 'Hi This is Row two');
INSERT INTO MY_TABLE VALUES(3,'Frank', 'Hi This is Row three');
INSERT INTO MY_TABLE VALUES(4,'Jane', 'Hi This is Row four');
INSERT INTO MY_TABLE VALUES(5,'Robert', 'Hi This is Row five');

Search in the clob column

SELECT * FROM MY_TABLE where to_char(message) like '%e%';


1    Tom     Hi This is Row one         
3    Frank   Hi This is Row three
5    Robert  Hi This is Row five

LINQ order by null column where order is ascending and nulls should be last

Try putting both columns in the same orderby.

orderby p.LowestPrice.HasValue descending, p.LowestPrice

Otherwise each orderby is a separate operation on the collection re-ordering it each time.

This should order the ones with a value first, "then" the order of the value.

How can we stop a running java process through Windows cmd?

It is rather messy but you need to do something like the following:

START "do something window" dir
FOR /F "tokens=2" %I in ('TASKLIST /NH /FI "WINDOWTITLE eq do something window"' ) DO SET PID=%I

Found this on this page.

(This kind of thing is much easier if you have a UNIX / LINUX system ... or if you run Cygwin or similar on Windows.)

Check if current date is between two dates Oracle SQL

SELECT to_char(emp_login_date,'DD-MON-YYYY HH24:MI:SS'),A.* 
FROM emp_log A
WHERE emp_login_date BETWEEN to_date(to_char('21-MAY-2015 11:50:14'),'DD-MON-YYYY HH24:MI:SS')
to_date(to_char('22-MAY-2015 17:56:52'),'DD-MON-YYYY HH24:MI:SS') 
ORDER BY emp_login_date

Counter in foreach loop in C#

This is only true if you're iterating through an array; what if you were iterating through a different kind of collection that has no notion of accessing by index? In the array case, the easiest way to retain the index is to simply use a vanilla for loop.

Get data from file input in JQuery

I created a form data object and appended the file:

var form = new FormData(); 
form.append("video", $("#fileInput")[0].files[0]);

and i got:

Content-Disposition: form-data; name="video"; filename="Wildlife.wmv"
Content-Type: video/x-ms-wmv

in the headers sent. I can confirm this works because my file was sent and stored in a folder on my server. If you don't know how to use the FormData object there is some documentation online, but not much. Form Data Object Explination by Mozilla

Regular Expression to match only alphabetic characters

If you need to include non-ASCII alphabetic characters, and if your regex flavor supports Unicode, then


would be the correct regex.

Some regex engines don't support this Unicode syntax but allow the \w alphanumeric shorthand to also match non-ASCII characters. In that case, you can get all alphabetics by subtracting digits and underscores from \w like this:


\A matches at the start of the string, \z at the end of the string (^ and $ also match at the start/end of lines in some languages like Ruby, or if certain regex options are set).

How to get box-shadow on left & right sides only

I wasn't satisfied with the rounded top and bottom to the shadow present in Deefour's solution so created my own.

inset box-shadow creates a nice uniform shadow with the top and bottom cut off.

To use this effect on the sides of your element, create two pseudo elements :before and :after positioned absolutely on the sides of the original element.

div:before, div:after {
  content: " ";
  height: 100%;
  position: absolute;
  top: 0;
  width: 15px;
div:before {
  box-shadow: -15px 0 15px -15px inset;
  left: -15px;
div:after {
  box-shadow: 15px 0 15px -15px inset;
  right: -15px;

div {
  background: #EEEEEE;
  height: 100px;
  margin: 0 50px;
  width: 100px;
  position: relative;


Depending on your design, you may be able to use clip-path, as shown in @Luke's answer. However, note that in many cases this still results in the shadow tapering off at the top and bottom as you can see in this example:

div {
  width: 100px;
  height: 100px;
  background: #EEE;
  box-shadow: 0 0 15px 0px #000;
  clip-path: inset(0px -15px 0px -15px);
  position: relative;
  margin: 0 50px;

How to install Java SDK on CentOS?

The following command will return a list of all packages directly related to Java. They will be in the format of java-<version>.

$ yum search java | grep 'java-'

If there are no available packages, then you may need to download a new repository to search through. I suggest taking a look at Dag Wieers' repo. After downloading it, try the above command again.

You will see at least one version of Java packages available for download. Depending on when you read this, the lastest available version may be different.


The above package alone will only install JRE. To also install javac and JDK, the following command will do the trick:

$ yum install java-1.7.0-openjdk*

These packages will be installing (as well as their dependencies):


Test if executable exists in Python?

Easiest way I can think of:

def which(program):
    import os
    def is_exe(fpath):
        return os.path.isfile(fpath) and os.access(fpath, os.X_OK)

    fpath, fname = os.path.split(program)
    if fpath:
        if is_exe(program):
            return program
        for path in os.environ["PATH"].split(os.pathsep):
            exe_file = os.path.join(path, program)
            if is_exe(exe_file):
                return exe_file

    return None

Edit: Updated code sample to include logic for handling case where provided argument is already a full path to the executable, i.e. "which /bin/ls". This mimics the behavior of the UNIX 'which' command.

Edit: Updated to use os.path.isfile() instead of os.path.exists() per comments.

Edit: path.strip('"') seems like the wrong thing to do here. Neither Windows nor POSIX appear to encourage quoted PATH items.

Java: How to convert String[] to List or Set

It's a old code, anyway, try it:

import java.util.Arrays;
import java.util.List;
import java.util.ArrayList;
public class StringArrayTest
   public static void main(String[] args)
      String[] words = {"word1", "word2", "word3", "word4", "word5"};

      List<String> wordList = Arrays.asList(words);

      for (String e : wordList)

How to get number of rows inserted by a transaction

@@ROWCOUNT will give the number of rows affected by the last SQL statement, it is best to capture it into a local variable following the command in question, as its value will change the next time you look at it:

DECLARE @Rows int
DECLARE @TestTable table (col1 int, col2 int)
INSERT INTO @TestTable (col1, col2) select 1,2 union select 3,4


(2 row(s) affected)
Rows        ROWCOUNT
----------- -----------
2           1

(1 row(s) affected)

you get Rows value of 2, the number of inserted rows, but ROWCOUNT is 1 because the SELECT @Rows=@@ROWCOUNT command affected 1 row

if you have multiple INSERTs or UPDATEs, etc. in your transaction, you need to determine how you would like to "count" what is going on. You could have a separate total for each table, a single grand total value, or something completely different. You'll need to DECLARE a variable for each total you want to track and add to it following each operation that applies to it:

--note there is no error handling here, as this is a simple example
DECLARE @AppleTotal  int
DECLARE @PeachTotal  int

SELECT @AppleTotal=0,@PeachTotal=0


INSERT INTO Apple (col1, col2) Select col1,col2 from xyz where ...
SET @AppleTotal=@AppleTotal+@@ROWCOUNT

INSERT INTO Apple (col1, col2) Select col1,col2 from abc where ...
SET @AppleTotal=@AppleTotal+@@ROWCOUNT

INSERT INTO Peach (col1, col2) Select col1,col2 from xyz where ...
SET @PeachTotal=@PeachTotal+@@ROWCOUNT

INSERT INTO Peach (col1, col2) Select col1,col2 from abc where ...
SET @PeachTotal=@PeachTotal+@@ROWCOUNT


SELECT @AppleTotal AS AppleTotal, @PeachTotal AS PeachTotal

How to put data containing double-quotes in string variable?

You can escape (this is how this principle is called) the double quotes by prefixing them with another double quote. You can put them in a string as follows:

Dim MyVar as string = "some text ""hello"" "

This will give the MyVar variable a value of some text "hello".

Replace \n with <br />

I know this is an old thread but I tried the suggested answers and unfortunately simply replacing line breaks with <br /> didn't do what I needed it to. It simply rendered them literally as text.

One solution would have been to disable autoescape like this: {% autoescape false %}{{ mystring }}{% endautoescape %} and this works fine but this is no good if you have user-provided content. So this was also not a solution for me.

So this is what I used:

In Python:

newvar = mystring.split('\n')

And then, passing newvar into my Jinja template:

{% for line in newvar %}
    <br />{{ line }}
{% endfor %}

Extract value of attribute node via XPath

Here is the standard formula to extract the values of attribute and text using XPath-

  1. To extract attribute value for Web Element-


  2. To extract text value for Web Element-


In your case here is the xpath which will return


It will return:


Iterate Multi-Dimensional Array with Nested Foreach Statement

Here's how to visit each element in a 2-dimensional array. Is this what you were looking for?

for (int i=0;i<array.GetLength(0);i++)
    for (int j=0;j<array.GetLength(1);j++)
        int cell = array[i,j];

How to display pandas DataFrame of floats using a format string for columns?


    df = pd.DataFrame({'money': [100.456, 200.789], 'share': ['100,000', '200,000']})
    print(df.to_string(formatters={'money': '${:,.2f}'.format}))
    for col_name in ('share',):
        df[col_name] = df[col_name].map(lambda p: int(p.replace(',', '')))
        money    share
    0  100.456  100,000
    1  200.789  200,000

        money    share
    0 $100.46  100,000
    1 $200.79  200,000

         money   share
    0  100.456  100000
    1  200.789  200000

Best way to do nested case statement logic in SQL Server

I personally do it this way, keeping the embedded CASE expressions confined. I'd also put comments in to explain what is going on. If it is too complex, break it out into function.

    CASE WHEN condition THEN
      CASE WHEN condition1 THEN
        CASE WHEN condition2 THEN calculation1
        ELSE calculation2 END
        CASE WHEN condition2 THEN calculation3
        ELSE calculation4 END
    ELSE CASE WHEN condition1 THEN 
      CASE WHEN condition2 THEN calculation5
      ELSE calculation6 END
    ELSE CASE WHEN condition2 THEN calculation7
         ELSE calculation8 END
    END AS 'calculatedcol1',
    col5 -- etc
FROM table

Random number c++ in some range

Since nobody posted the modern C++ approach yet,

#include <iostream>
#include <random>
int main()
    std::random_device rd; // obtain a random number from hardware
    std::mt19937 gen(rd()); // seed the generator
    std::uniform_int_distribution<> distr(25, 63); // define the range

    for(int n=0; n<40; ++n)
        std::cout << distr(gen) << ' '; // generate numbers

Why can't I use the 'await' operator within the body of a lock statement?

I did try using a Monitor (code below) which appears to work but has a GOTCHA... when you have multiple threads it will give... System.Threading.SynchronizationLockException Object synchronization method was called from an unsynchronized block of code.

using System;
using System.Threading;
using System.Threading.Tasks;

namespace MyNamespace
    public class ThreadsafeFooModifier : 
        private readonly object _lockObject;

        public async Task<FooResponse> ModifyFooAsync()
            FooResponse result;
                result = await SomeFunctionToModifyFooAsync();
            return result;

Prior to this I was simply doing this, but it was in an ASP.NET controller so it resulted in a deadlock.

public async Task<FooResponse> ModifyFooAsync() { lock(lockObject) { return SomeFunctionToModifyFooAsync.Result; } }

Appending pandas dataframes generated in a for loop

Use pd.concat to merge a list of DataFrame into a single big DataFrame.

appended_data = []
for infile in glob.glob("*.xlsx"):
    data = pandas.read_excel(infile)
    # store DataFrame in list
# see pd.concat documentation for more info
appended_data = pd.concat(appended_data)
# write DataFrame to an excel sheet 

Failure during conversion to COFF: file invalid or corrupt

I am using Visual Studio 2010.

This happened to me when I installed .NET 4.5. Uninstall of .NET 4.5 and install of .NET 4.0 helped me and error messages disappeared.

What is the easiest way to push an element to the beginning of the array?

What about using the unshift method?

ary.unshift(obj, ...) ? ary
Prepends objects to the front of self, moving other elements upwards.

And in use:

irb>> a = [ 0, 1, 2]
=> [0, 1, 2]
irb>> a.unshift('x')
=> ["x", 0, 1, 2]
irb>> a.inspect
=> "["x", 0, 1, 2]"

Why doesn't Git ignore my specified file?

Another possible reasona few instances of git clients running at the same time. For example "git shell" + "GitHub Desktop", etc.

This happened to me, I was using "GitHub Desktop" as the main client and it was ignoring some new .gitignore settings: commit after commit:

  1. You commit something.
  2. Next, commit: it ignores .gitignore settings. Commit includes lots of temp files mentioned in the .gitignore.
  3. Clear git cache; check whether .gitignore is UTF8; remove files -> commit -> move files back; skip 1 commit – nothing helped.

Reason: the Visual Studio Code editor was running in the background with the same opened repository. VS Code has built-in git control, and this makes some conflicts.

Solution: double-check multiple, hidden git clients and use only one git client at once, especially while clearing git cache.

Understanding the difference between Object.create() and new SomeFunction()

Internally Object.create does this:

Object.create = function (o) {
    function F() {}
    F.prototype = o;
    return new F();

The syntax just takes away the illusion that JavaScript uses Classical Inheritance.

jquery append external html file into my page

        <script src="" type="text/javascript"></script>
        <script type="text/javascript">
            $(function () {
                $.get("banner.html", function (data) {
        <div id="appendToThis"></div>

Update value of a nested dictionary of varying depth

If you want to replace a "full nested dictionary with arrays" you can use this snippet :

It will replace any "old_value" by "new_value". It's roughly doing a depth-first rebuilding of the dictionary. It can even work with List or Str/int given as input parameter of first level.

def update_values_dict(original_dict, future_dict, old_value, new_value):
    # Recursively updates values of a nested dict by performing recursive calls

    if isinstance(original_dict, Dict):
        # It's a dict
        tmp_dict = {}
        for key, value in original_dict.items():
            tmp_dict[key] = update_values_dict(value, future_dict, old_value, new_value)
        return tmp_dict
    elif isinstance(original_dict, List):
        # It's a List
        tmp_list = []
        for i in original_dict:
            tmp_list.append(update_values_dict(i, future_dict, old_value, new_value))
        return tmp_list
        # It's not a dict, maybe a int, a string, etc.
        return original_dict if original_dict != old_value else new_value

Changing EditText bottom line color with appcompat v7

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>

    <item name="colorControlNormal">@color/colorAccent</item>
    <item name="colorControlActivated">@color/colorAccent</item>
    <item name="colorControlHighlight">@color/colorAccent</item>


How to get the index of a maximum element in a NumPy array along one axis

>>> import numpy as np
>>> a = np.array([[1,2,3],[4,3,1]])
>>> i,j = np.unravel_index(a.argmax(), a.shape)
>>> a[i,j]

Align button at the bottom of div using CSS

You can use position:absolute; to absolutely position an element within a parent div. When using position:absolute; the element will be positioned absolutely from the first positioned parent div, if it can't find one it will position absolutely from the window so you will need to make sure the content div is positioned.

To make the content div positioned, all position values that aren't static will work, but relative is the easiest since it doesn't change the divs positioning by itself.

So add position:relative; to the content div, remove the float from the button and add the following css to the button:

position: absolute;
right:    0;
bottom:   0;

How to find all links / pages on a website

Another alternative might be

Array.from(document.querySelectorAll("a")).map(x => x.href)

With your $$( its even shorter

Array.from($$("a")).map(x => x.href)

Service has zero application (non-infrastructure) endpoints

I had this error in a Windows Service when my WCF Service Library that I created was not connected for hosting, but was connected for connection. I was missing an endpoint. (I wanted both connection and hosting in my Windows Service so that I could serve up the WCF Service to other connections, as well as have the main process of my Windows Service use it as well to do various tasks on a timer/schedule.)

The fix was that I rightlcicked my App.config file and chose Edit WCF Configuration. Then, I did the steps for Create Service so that I could connect to my WCF Service. Now I had two endpoints in my App.config, not just one. One endpoint was for the connection to the WCF Service Library, and another was for the hosting of it.

Super-simple example of C# observer/observable with delegates

Something like this:

// interface implementation publisher
public delegate void eiSubjectEventHandler(eiSubject subject);

public interface eiSubject
    event eiSubjectEventHandler OnUpdate;

    void GenereteEventUpdate();


// class implementation publisher
class ecSubject : eiSubject
    private event eiSubjectEventHandler _OnUpdate = null;
    public event eiSubjectEventHandler OnUpdate
            lock (this)
                _OnUpdate -= value;
                _OnUpdate += value;
        remove { lock (this) { _OnUpdate -= value; } }

    public void GenereteEventUpdate()
        eiSubjectEventHandler handler = _OnUpdate;

        if (handler != null)


// interface implementation subscriber
public interface eiObserver
    void DoOnUpdate(eiSubject subject);


// class implementation subscriber
class ecObserver : eiObserver
    public virtual void DoOnUpdate(eiSubject subject)

. observer pattern C# with event . link to the repository

In WPF, what are the differences between the x:Name and Name attributes?

They are not the same thing.

x:Name is a xaml concept, used mainly to reference elements. When you give an element the x:Name xaml attribute, "the specified x:Name becomes the name of a field that is created in the underlying code when xaml is processed, and that field holds a reference to the object." (MSDN) So, it's a designer-generated field, which has internal access by default.

Name is the existing string property of a FrameworkElement, listed as any other wpf element property in the form of a xaml attribute.

As a consequence, this also means x:Name can be used on a wider range of objects. This is a technique to enable anything in xaml to be referenced by a given name.

How can I explicitly free memory in Python?

As other answers already say, Python can keep from releasing memory to the OS even if it's no longer in use by Python code (so gc.collect() doesn't free anything) especially in a long-running program. Anyway if you're on Linux you can try to release memory by invoking directly the libc function malloc_trim (man page). Something like:

import ctypes
libc = ctypes.CDLL("")

"&" meaning after variable type

The & means that the function accepts the address (or reference) to a variable, instead of the value of the variable.

For example, note the difference between this:

void af(int& g)

int main()
    int g = 123;
    cout << g;
    cout << g;
    return 0;

And this (without the &):

void af(int g)

int main()
    int g = 123;
    cout << g;
    cout << g;
    return 0;

Parsing JSON from URL

public static TargetClassJson downloadPaletteJson(String url) throws IOException {
        if (StringUtils.isBlank(url)) {
            return null;
        String genreJson = IOUtils.toString(new URL(url).openStream());
        return new Gson().fromJson(genreJson, TargetClassJson.class);

How to get the difference between two arrays in JavaScript?

Here is what I use:

var newArr = a1.filter(function(elem) {
            return a2.indexOf(elem) === -1;
        }).concat( a2.filter(function(elem) {
            return a1.indexOf(elem) === -1;

or this one

var newArr = a1.concat(a2);
        function check(item) {
            if (a1.indexOf(item) === -1 || a2.indexOf(item) === -1) {
                return item;
        return newArr.filter(check);

SQL, Postgres OIDs, What are they and why are they useful?

OID's are still in use for Postgres with large objects (though some people would argue large objects are not generally useful anyway). They are also used extensively by system tables. They are used for instance by TOAST which stores larger than 8KB BYTEA's (etc.) off to a separate storage area (transparently) which is used by default by all tables. Their direct use associated with "normal" user tables is basically deprecated.

The oid type is currently implemented as an unsigned four-byte integer. Therefore, it is not large enough to provide database-wide uniqueness in large databases, or even in large individual tables. So, using a user-created table's OID column as a primary key is discouraged. OIDs are best used only for references to system tables.

Apparently the OID sequence "does" wrap if it exceeds 4B 6. So in essence it's a global counter that can wrap. If it does wrap, some slowdown may start occurring when it's used and "searched" for unique values, etc.

See also

Makefiles with source files in different directories

I think it's better to point out that using Make (recursive or not) is something that usually you may want to avoid, because compared to today tools, it's difficult to learn, maintain and scale.

It's a wonderful tool but it's direct use should be considered obsolete in 2010+.

Unless, of course, you're working in a special environment i.e. with a legacy project etc.

Use an IDE, CMake or, if you're hard cored, the Autotools.

(edited due to downvotes, ty Honza for pointing out)

What in the world are Spring beans?

Well you understood it partially. You have to tailor the beans according to your need and inform Spring container to manage it when required, by using a methodology populalrly known as IoC (Inversion of Control) coined by Martin Fowler, also known as Dependency Injection (DI).

You wire the beans in a way, so that you do not have to take care of the instantiating or evaluate any dependency on the bean. This is popularly known as Hollywood Principle.

Google is the best tool to explore more on this in addition to the links you would get flooded with here in this question. :)

Filter dict to contain only certain keys?

This one liner lambda should work:

dictfilt = lambda x, y: dict([ (i,x[i]) for i in x if i in set(y) ])

Here's an example:

my_dict = {"a":1,"b":2,"c":3,"d":4}
wanted_keys = ("c","d")

# run it
In [10]: dictfilt(my_dict, wanted_keys)
Out[10]: {'c': 3, 'd': 4}

It's a basic list comprehension iterating over your dict keys (i in x) and outputs a list of tuple (key,value) pairs if the key lives in your desired key list (y). A dict() wraps the whole thing to output as a dict object.

Getting an option text/value with JavaScript

var option_user_selection = document.getElementById("maincourse").options[document.getElementById("maincourse").selectedIndex ].text

How to reload/refresh jQuery dataTable?

Very Simple answer

$("#table_name").DataTable().ajax.reload(null, false); 

CSS text-transform capitalize on all caps


var links = document.getElementsByClassName("link");
for (var i = 0; i < links.length; i++) {
  links[i].innerHTML = links[i].innerHTML.toLowerCase();


.link { text-transform: capitalize; }

What Khan "ended up doing" (which is cleaner and worked for me) is down in the comments of the post marked as the answer.

Apache HttpClient 4.0.3 - how do I set cookie with sessionID for POST request?

I did it by passing the cookie through the HttpContext:

HttpContext localContext = new BasicHttpContext();

localContext.setAttribute(ClientContext.COOKIE_STORE, cookieStore);

response = client.execute(httppost, localContext);

How to pip install a package with min and max version range?

You can do:

$ pip install "package>=0.2,<0.3"

And pip will look for the best match, assuming the version is at least 0.2, and less than 0.3.

This also applies to pip requirements files. See the full details on version specifiers in PEP 440.

CSS file not refreshing in browser

Have you tried renaming the new version of your CSS to CSSv2.css and then directing your page to use that? If that solves the stale-file issue, then you're just experiencing non-refreshing files. If not, you've got bigger issues.

Javascript How to define multiple variables on a single line?

Why not doing it in two lines?

var a, b, c, d;    // All in the same scope
a = b = c = d = 1; // Set value to all.

The reason why, is to preserve the local scope on variable declarations, as this:

var a = b = c = d = 1;

will lead to the implicit declarations of b, c and d on the window scope.

Static image src in Vue.js template

declare new variable that the value contain the path of image

const imgLink = require('../../assets/your-image.png')

then call the variable

export default {
    name: 'onepage',
            img: imgLink,

bind that on html, this the example:

<a href="#"><img v-bind:src="img" alt="" class="logo"></a>

hope it will help

What is the simplest SQL Query to find the second largest value?

It is the most esiest way:

      Column name
      Table name 
      Column name DESC

How to enable zoom controls and pinch zoom in a WebView?

Check if you don't have a ScrollView wrapping your Webview.

In my case that was the problem. It seems ScrollView gets in the way of the pinch gesture.

To fix it, just take your Webview outside the ScrollView.

Running Command Line in Java

Have you tried the exec command within the Runtime class?

Runtime.getRuntime().exec("java -jar map.jar time.rel test.txt debug")

Runtime - Java Documentation

How do you get a query string on Flask?

This can be done using request.args.get(). For example if your query string has a field date, it can be accessed using

date = request.args.get('date')

Don't forget to add "request" to list of imports from flask, i.e.

from flask import request

Server cannot set status after HTTP headers have been sent IIS7.5

I apologize, but I'm adding my 2 cents to the thread just in case anyone has the same problem.

  • I used Forms Authentication in my MVC app
  • But some controller-actions were "anonymous" i.e. allowed to non-authenticated users
  • Sometimes in those actions I would still want users to be redirected to the login form under some condition
  • to do that - I have this in my action method: return new HttpStatusCodeResult(401) - and ASP.NET is super nice to detect this, and it redirects the user to the login page! Magic, right? It even has the proper ReturnUrl parameter etc.

But you see where I'm getting here? I return 401. And ASP.NET redirects the user. Which is essentially returns 302. One status code is replaced with another.

And some IIS servers (just some!) throw this exception. Some don't. - I don't have it on my test serevr, only on my production server (ain't it always the case right o_O)

I know my answer is essentially repeating what's already said here, but sometimes it's just hard to figure out where this overwriting happens exactly.

Replace an element into a specific position of a vector

You can do that using at. You can try out the following simple example:

const size_t N = 20;
std::vector<int> vec(N);
try { - 1) = 7;
} catch (std::out_of_range ex) {
    std::cout << ex.what() << std::endl;
assert( - 1) == 7);

Notice that method at returns an allocator_type::reference, which is that case is a int&. Using at is equivalent to assigning values like vec[i]=....

There is a difference between at and insert as it can be understood with the following example:

const size_t N = 8;
std::vector<int> vec(N);
for (size_t i = 0; i<5; i++){
    vec[i] = i + 1;

vec.insert(vec.begin()+2, 10);

If we now print out vec we will get:

1 2 10 3 4 5 0 0 0

If, instead, we did = 10, or vec[2]=10, we would get

1 2 10 4 5 0 0 0

Querying Datatable with where condition

Something like this...

var res = from row in myDTable.AsEnumerable()
where row.Field<int>("EmpID") == 5 &&
(row.Field<string>("EmpName") != "abc" ||
row.Field<string>("EmpName") != "xyz")
select row;

See also LINQ query on a DataTable

Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]

Either you experienced database connection issue or you missed any of the hibernate configurations to connect to database such as database DIALECT.

Happens if your database server was disconnected due to network related issue.

If you're using spring boot along with hibernate connected to Oracle Db, use

entitymanager.packagesToScan: com

Get UserDetails object from Security Context in Spring MVC controller

Let Spring 3 injection take care of this.

Thanks to tsunade21 the easiest way is:

 @RequestMapping(method = RequestMethod.GET)   
 public ModelAndView anyMethodNameGoesHere(Principal principal) {
        final String loggedInUserName = principal.getName();


Center form submit buttons HTML / CSS

Input elements are inline by default. Add display:block to get the margins to apply. This will, however, break the buttons onto two separate lines. Use a wrapping <div> with text-align: center as suggested by others to get them on the same line.

Git: How to remove proxy

If you already unset the proxy from global and local level and still see the proxy details while you do

         git config -l

then unset the variable from system level, generally the configuration stored at below location

 C:\Program Files\Git\mingw64/etc/gitconfig

Open Facebook Page in Facebook App (if installed) on Android

you can use this:

try {
                Intent followIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("fb://facewebmodal/f?href=" +
                        ""+scoped user id+"/"));
            } catch (Exception e) {
                activity.startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("" + user name)));
                String errorMessage = (e.getMessage() == null) ? "Message is empty" : e.getMessage();

attention: you can get scoped user id from "link" permission facebook api

Concatenating strings in C, which method is more efficient?

Don't worry about efficiency: make your code readable and maintainable. I doubt the difference between these methods is going to matter in your program.

104, 'Connection reset by peer' socket error, or When does closing a socket result in a RST rather than FIN?

Normally, you'd get an RST if you do a close which doesn't linger (i.e. in which data can be discarded by the stack if it hasn't been sent and ACK'd) and a normal FIN if you allow the close to linger (i.e. the close waits for the data in transit to be ACK'd).

Perhaps all you need to do is set your socket to linger so that you remove the race condition between a non lingering close done on the socket and the ACKs arriving?

List passed by ref - help me explain this behaviour

You are passing a reference to the list, but your aren't passing the list variable by reference - so when you call ChangeList the value of the variable (i.e. the reference - think "pointer") is copied - and changes to the value of the parameter inside ChangeList aren't seen by TestMethod.


private void ChangeList(ref List<int> myList) {...}
ChangeList(ref myList);

This then passes a reference to the local-variable myRef (as declared in TestMethod); now, if you reassign the parameter inside ChangeList you are also reassigning the variable inside TestMethod.

400 BAD request HTTP error code meaning?

Using 400 status codes for any other purpose than indicating that the request is malformed is just plain wrong.

If the request payload contains a byte-sequence that could not be parsed as application/json (if the server expects that dataformat), the appropriate status code is 415:

The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method.

If the request payload is syntactically correct but semantically incorrect, the non-standard 422 response code may be used, or the standard 403 status code:

The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated.

Run an exe from C# code


Process process = Process.Start(@"Data\myApp.exe");
int id = process.Id;
Process tempProc = Process.GetProcessById(id);
this.Visible = false;
this.Visible = true;

Regular expression for checking if capital letters are found consecutively in a string?

Aside from tchrists excellent post concerning unicode, I think you don't need the complex solution with a negative lookahead... Your definition requires an Uppercase-letter followed by at least one group of (a lowercase letter optionally followed by an Uppercase-letter)

[A-Z]    // Start with an uppercase Letter
(        // A Group of:
  [a-z]  // mandatory lowercase letter
  [A-Z]? // an optional Uppercase Letter at the end
         // or in between lowercase letters
)+       // This group at least one time

Just a bit more compact and easier to read I think...

How to find controls in a repeater header or footer

You can take a reference on the control on the ItemCreated event, and then use it later.

Simple Android RecyclerView example

This will be the simplest version of the implementation of RecyclerView.

enter image description here


<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android=""




<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=""

        android:textSize="16dp" />


public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
  private List<String> data;
  public CustomAdapter (List<String> data){ = data;

  public CustomAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View rowItem = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_view, parent, false);
    return new ViewHolder(rowItem);

  public void onBindViewHolder(CustomAdapter.ViewHolder holder, int position) {

  public int getItemCount() {

  public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    private TextView textView;

    public ViewHolder(View view) {
      this.textView = view.findViewById(;

    public void onClick(View view) {
      Toast.makeText(view.getContext(), "position : " + getLayoutPosition() + " text : " + this.textView.getText(), Toast.LENGTH_SHORT).show();

public class MainActivity extends AppCompatActivity {

  protected void onCreate(Bundle savedInstanceState) {

    RecyclerView recyclerView = findViewById(;
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    recyclerView.setAdapter(new CustomAdapter(generateData()));
    recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));

  private List<String> generateData() {
    List<String> data = new ArrayList<>();
    for (int i = 0; i < 100; i++) {
      data.add(String.valueOf(i) + "th Element");
    return data;


How to sort alphabetically while ignoring case sensitive?

It is very unclear what you are trying to do, but you can sort a list like this:

List<String> fruits = new ArrayList<String>(7);


System.out.println("Unsorted: " + fruits);

Collections.sort(fruits, new Comparator<String>() {
    public int compare(String o1, String o2) {              
        return o1.compareToIgnoreCase(o2);

System.out.println("Sorted: " + fruits);

file_get_contents("php://input") or $HTTP_RAW_POST_DATA, which one is better to get the body of JSON request?

file_get_contents(php://input) - gets the raw POST data and you need to use this when you write APIs and need XML/JSON/... input that cannot be decoded to $_POST by PHP some example :

send by post JSON string

<input type="button" value= "click" onclick="fn()">
 function fn(){

    var js_obj = {plugin: 'jquery-json', version: 2.3};

    var encoded = JSON.stringify( js_obj );

var data= encoded

  type: "POST",
  url: '1.php',
  data: data,
  success: function(data){




//print_r($_POST); //empty!!! don't work ... 
var_dump( file_get_contents('php://input'));

How do I use Safe Area Layout programmatically?

Swift 4.2 and 5.0. Suppose you wan to add Leading, Trailing, Top and Bottom constraints on viewBg. So, you can use the below code.

let guide = self.view.safeAreaLayoutGuide
viewBg.trailingAnchor.constraint(equalTo: guide.trailingAnchor).isActive = true
viewBg.leadingAnchor.constraint(equalTo: guide.leadingAnchor).isActive = true
viewBg.topAnchor.constraint(equalTo: guide.topAnchor).isActive = true
viewBg.bottomAnchor.constraint(equalTo: guide.bottomAnchor).isActive = true

Which browser has the best support for HTML 5 currently?

To test your browser, go to The code is being maintained at: github dot com slash NielsLeenheer slash html5test.

List<String> to ArrayList<String> conversion issue

Cast works where the actual instance of the list is an ArrayList. If it is, say, a Vector (which is another extension of List) it will throw a ClassCastException.

The error when changing the definition of your HashMap is due to the elements later being processed, and that process expects a method that is defined only in ArrayList. The exception tells you that it did not found the method it was looking for.

Create a new ArrayList with the contents of the old one.

new ArrayList<String>(myList);

compareTo() vs. equals()

String.equals() requires invoking instanceof operator while compareTo() requires not. My colleague has noted large performance drop-down caused by excessive numbers of instanceof calls in equals() method, however my test has proved compareTo() to be only slightly faster.

I was using, however, Java 1.6. On other versions (or other JDK vendors) the difference could be larger.

The test compared each-to-each string in 1000 element arrays, repeated 10 times.

Check if object exists in JavaScript

If you care about its existence only ( has it been declared ? ), the approved answer is enough :

if (typeof maybeObject != "undefined") {
   alert("GOT THERE");

If you care about it having an actual value, you should add:

if (typeof maybeObject != "undefined" && maybeObject != null ) {
   alert("GOT THERE");

As typeof( null ) == "object"

e.g. bar = { x: 1, y: 2, z: null}

typeof( bar.z ) == "object" 
typeof( bar.not_present ) == "undefined" 

this way you check that it's neither null or undefined, and since typeof does not error if value does not exist plus && short circuits, you will never get a run-time error.

Personally, I'd suggest adding a helper fn somewhere (and let's not trust typeof() ):

function exists(data){
   data !== null && data !== undefined

if( exists( maybeObject ) ){
    alert("Got here!"); 

How to find Port number of IP address?

DNS server usually have a standard of ports used. But if it's different, you could try nmap and do a port scan like so:

> nmap

When to use the JavaScript MIME type application/javascript instead of text/javascript?

application because .js-Files aren't something a user wants to read but something that should get executed.

matplotlib savefig in jpeg format

To clarify and update @neo useful answer and the original question. A clean solution consists of installing Pillow, which is an updated version of the Python Imaging Library (PIL). This is done using

pip install pillow

Once Pillow is installed, the standard Matplotlib commands

import matplotlib.pyplot as plt

plt.plot([1, 2])

will save the figure into a JPEG file and will not generate a ValueError any more.

Contrary to @amillerrhodes answer, as of Matplotlib 3.1, JPEG files are still not supported. If I remove the Pillow package I still receive a ValueError about an unsupported file type.

What are ABAP and SAP?

SAP is a company and offers a full Enterprise Resource Planning (ERP) system, business platform, and the associated modules (financials, general ledger, &c).

ABAP is the primary programming language used to write SAP software and customizations. It would do it injustice to think of it as COBOL and SQL on steroids, but that gives you an idea. ABAP runs within the SAP system.

SAP and ABAP abstract the DB and run atop various underlying DBMSs.

SAP produces other things as well and even publicly says they dabble in Java and even produce a J2EE container, but tried-and-true SAP is ABAP through-and-through.

Convert a PHP script into a stand-alone windows executable

I tried most of solution given in the 1st answer, the only one that worked for me and is non-commercial is php-desktop.

I simply put my php files in the www/ folder, changed the name of .exe and was able to run my php as an exe !!

Also there is a complete documentation, up to date support, windows and linux (and soon mac) compatibility and options can easily be changed.

How to use basic authorization in PHP curl

Can you try this,

 $ch = curl_init($url);
 curl_setopt($ch, CURLOPT_USERPWD, $username . ":" . $password);  


Difference between webdriver.get() and webdriver.navigate()


In the below code I navigated to 3 different URLs and when the execution comes to navigate command, it navigated back to facebook home page.

public class FirefoxInvoke {
                public static void browserInvoke()
                    System.setProperty("webdriver.gecko.driver", "gecko-driver-path");
                WebDriver driver=new FirefoxDriver();

                public static void main(String[] args) {
                    // TODO Auto-generated method stub



In below code, I have used navigate() instead of get(), but both the snippets(Case-1 and Case-2) are working exactly the same, just the case-2 execution time is less than of case-1

public class FirefoxInvoke {
                public static void browserInvoke()
                    System.setProperty("webdriver.gecko.driver", "gecko-driver-path");
                WebDriver driver=new FirefoxDriver();

                public static void main(String[] args) {
                    // TODO Auto-generated method stub

  • So the main difference between get() and navigate() is, both are performing the same task but with the use of navigate() you can move back() or forward() in your session's history.
  • navigate() is faster than get() because navigate() does not wait for the page to load fully or completely.

How do I get the current date and time in PHP?

date(format, timestamp)

The date function returns a string formatted according to the given format string using the given integer timestamp or the current time if no timestamp is given. In other words, timestamp is optional and defaults to the value of time().

And the parameters are -

format - Required. Specifies the format of the timestamp

timestamp - (Optional) Specifies a timestamp. Default is the current date and time

How to get a simple date

The required format parameter of the date() function specifies how to format the date (or time).

Here are some characters that are commonly used for dates:

  1. d - Represents the day of the month (01 to 31)
  2. m - Represents a month (01 to 12)
  3. Y - Represents a year (in four digits)
  4. l (lowercase 'L') - Represents the day of the week

Other characters, like "/", ".", or "-" can also be inserted between the characters to add additional formatting.

The example below formats today's date in three different ways:

    echo "Today is " . date("Y/m/d") . "<br>";
    echo "Today is " . date("Y.m.d") . "<br>";
    echo "Today is " . date("Y-m-d") . "<br>";
    echo "Today is " . date("l");

Some useful links

Hash function for a string

Hash functions for algorithmic use have usually 2 goals, first they have to be fast, second they have to evenly distibute the values across the possible numbers. The hash function also required to give the all same number for the same input value.

if your values are strings, here are some examples for bad hash functions:

  1. string[0] - the ASCII characters a-Z are way more often then others
  2. string.lengh() - the most probable value is 1

Good hash functions tries to use every bit of the input while keeping the calculation time minimal. If you only need some hash code, try to multiply the bytes with prime numbers, and sum them.

Difference between adjustResize and adjustPan in android?

I was also a bit confused between adjustResize and adjustPan when I was a beginner. The definitions given above are correct.
AdjustResize : Main activity's content is resized to make room for soft input i.e keyboard
AdjustPan : Instead of resizing overall contents of the window, it only pans the content so that the user can always see what is he typing
AdjustNothing : As the name suggests nothing is resized or panned. Keyboard is opened as it is irrespective of whether it is hiding the contents or not.

I have a created a example for better understanding
Below is my xml file:

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""

        android:hint="Type Here"




Here is the design view of the xml
original view

AdjustResize Example below:
adjustResize example

AdjustPan Example below:
adjustPan example

AdjustNothing Example below:
adjustNothing example

setting multiple column using one update

UPDATE some_table 
   SET this_column=x, that_column=y 
   WHERE something LIKE 'them'

ImportError: no module named win32api

The following should work:

pip install pywin32

But it didn't for me. I fixed this by downloading and installing the exe from here:

clear table jquery

I needed this:

$('#myTable tbody > tr').remove();

It deletes all rows except the header.

What is the best place for storing uploaded images, SQL database or disk file system?

Option A.

Once the image is loaded you can verify the format and resize it before saving. There a number of .Net code samples to resize images on For instance:

Length of string in bash

To get the length of a string stored in a variable, say:

myvar="some string"

To confirm it was properly saved, echo it:

$ echo "$size"

Connecting to Postgresql in a docker container from outside

In case, it is a django backend application, you can do something like this.

docker exec -it container_id python dbshell

Authentication plugin 'caching_sha2_password' is not supported

I ran into the same problem as well. My problem was, that I accidentally installed the wrong connector version. Delete your currently installed version from your file system (my path looks like this: C:\Program Files\Python36\Lib\site-packages) and then execute "pip install mysql-connector-python". This should solve your problem

Tomcat: How to find out running tomcat version

Enter 404.jsp or non-existent.jsp.

Get Tomcat/JBoss version number at bottom of page.

Java command not found on Linux

I use the following script to update the default alternative after install jdk.

export JAVA_BIN_DIR=/usr/java/default/bin # replace with your installed directory
a=(java javac javadoc javah javap javaws)
for exe in ${a[@]}; do
    sudo update-alternatives --install "/usr/bin/${exe}" "${exe}" "${JAVA_BIN_DIR}/${exe}" 1
    sudo update-alternatives --set ${exe} ${JAVA_BIN_DIR}/${exe}

How to globally replace a forward slash in a JavaScript string?

Is this what you want?

'string with / in it'.replace(/\//g, '\\');

How to get the PID of a process by giving the process name in Mac OS X ?

The answer above was mostly correct, just needed some tweaking for the different parameters in Mac OSX.

ps -A | grep [f]irefox | awk '{print $1}'

type object 'datetime.datetime' has no attribute 'datetime'

I run into the same error maybe you have already imported the module by using only import datetime so change form datetime import datetime to only import datetime. It worked for me after I changed it back.

Pip freeze vs. pip list

For those looking for a solution. If you accidentally made pip requirements with pip list instead of pip freeze, and want to convert into pip freeze format. I wrote this R script to do so.


pip_list = read_lines("requirements.txt")

pip_freeze = pip_list %>%
  str_replace_all(" \\(", "==") %>%
  str_replace_all("\\)$", "")

pip_freeze %>% write_lines("requirements.txt")

Is it possible to append Series to rows of DataFrame without making a list first?

Maybe an easier way would be to add the pandas.Series into the pandas.DataFrame with ignore_index=True argument to DataFrame.append(). Example -

DF = DataFrame()
for sample,data in D_sample_data.items():
    SR_row = pd.Series(data.D_key_value)
    DF = DF.append(SR_row,ignore_index=True)

Demo -

In [1]: import pandas as pd

In [2]: df = pd.DataFrame([[1,2],[3,4]],columns=['A','B'])

In [3]: df
   A  B
0  1  2
1  3  4

In [5]: s = pd.Series([5,6],index=['A','B'])

In [6]: s
A    5
B    6
dtype: int64

In [36]: df.append(s,ignore_index=True)
   A  B
0  1  2
1  3  4
2  5  6

Another issue in your code is that DataFrame.append() is not in-place, it returns the appended dataframe, you would need to assign it back to your original dataframe for it to work. Example -

DF = DF.append(SR_row,ignore_index=True)

To preserve the labels, you can use your solution to include name for the series along with assigning the appended DataFrame back to DF. Example -

DF = DataFrame()
for sample,data in D_sample_data.items():
    SR_row = pd.Series(data.D_key_value,name=sample)
    DF = DF.append(SR_row)

Find all files in a folder

You can try with Directory.GetFiles and fix your pattern

 string[] files = Directory.GetFiles(@"c:\", "*.txt");

 foreach (string file in files)
    File.Copy(file, "....");

 Or Move

 foreach (string file in files)
    File.Move(file, "....");

Why does 'git commit' not save my changes?

As the message says:

no changes added to commit (use "git add" and/or "git commit -a")

Git has a "staging area" where files need to be added before being committed, you can read an explanation of it here.

For your specific example, you can use:

git commit -am "save arezzo files"

(note the extra a in the flags, can also be written as git commit -a -m "message" - both do the same thing)

Alternatively, if you want to be more selective about what you add to the commit, you use the git add command to add the appropriate files to the staging area, and git status to preview what is about to be added (remembering to pay attention to the wording used).

You can also find general documentation and tutorials for how to use git on the git documentation page which will give more detail about the concept of staging/adding files.

One other thing worth knowing about is interactive staging - this allows you to add parts of a file to the staging area, so if you've made three distinct code changes (for related but different functionality), you can use interactive mode to split the changes and add/commit each part in turn. Having smaller specific commits like this can be helpful.

What is the difference between procedural programming and functional programming?

If you have a chance, I would recommand getting a copy of Lisp/Scheme, and doing some projects in it. Most of the ideas that have lately become bandwagons were expressed in Lisp decades ago: functional programming, continuations (as closures), garbage collection, even XML.

So that would be a good way to get a head start on all these current ideas, and a few more besides, like symbolic computation.

You should know what functional programming is good for, and what it isn't good for. It isn't good for everything. Some problems are best expressed in terms of side-effects, where the same question gives differet answers depending on when it is asked.

Build error, This project references NuGet

This problem appeared for me when I was creating folders in the filesystem (not in my solution) and moved some projects around.

Turns out that the package paths are relative from the csproj files. So I had to change the "HintPath" of my references:

<Reference Include="EntityFramework, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL">


<Reference Include="EntityFramework, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL">

Notice the double "..\" in 'HintPath'.

I also had to change my error conditions, for example I had to change:

<Error Condition="!Exists('..\packages\Microsoft.Net.Compilers.1.1.1\build\Microsoft.Net.Compilers.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Microsoft.Net.Compilers.1.1.1\build\Microsoft.Net.Compilers.props'))" />


<Error Condition="!Exists('..\..\packages\Microsoft.Net.Compilers.1.1.1\build\Microsoft.Net.Compilers.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\Microsoft.Net.Compilers.1.1.1\build\Microsoft.Net.Compilers.props'))" />

Again, notice the double "..\".