Programs & Examples On #Path dependent type

Java - How to create a custom dialog box?

This lesson from the Java tutorial explains each Swing component in detail, with examples and API links.

Convert generic list to dataset in C#

Brute force code to answer your question:

DataTable dt = new DataTable();

//for each of your properties
dt.Columns.Add("PropertyOne", typeof(string));

foreach(Entity entity in entities)
  DataRow row = dt.NewRow();

  //foreach of your properties
  row["PropertyOne"] = entity.PropertyOne;


DataSet ds = new DataSet();
return ds;

Now for the actual question. Why would you want to do this? As mentioned earlier, you can bind directly to an object list. Maybe a reporting tool that only takes datasets?

How to Replace dot (.) in a string in Java

Use Apache Commons Lang:

String a= "\\*\\";
str = StringUtils.replace(xpath, ".", a);

or with standalone JDK:

String a = "\\*\\"; // or: String a = "/*/";
String replacement = Matcher.quoteReplacement(a);
String searchString = Pattern.quote(".");
String str = xpath.replaceAll(searchString, replacement);

How are echo and print different in PHP?


  1. Speed. There is a difference between the two, but speed-wise it should be irrelevant which one you use. echo is marginally faster since it doesn't set a return value if you really want to get down to the nitty gritty.

  2. Expression. print() behaves like a function in that you can do: $ret = print "Hello World"; And $ret will be 1. That means that print can be used as part of a more complex expression where echo cannot. An example from the PHP Manual:

$b ? print "true" : print "false";

print is also part of the precedence table which it needs to be if it is to be used within a complex expression. It is just about at the bottom of the precedence list though. Only , AND OR XOR are lower.

  1. Parameter(s). The grammar is: echo expression [, expression[, expression] ... ] But echo ( expression, expression ) is not valid. This would be valid: echo ("howdy"),("partner"); the same as: echo "howdy","partner"; (Putting the brackets in that simple example serves no purpose since there is no operator precedence issue with a single term like that.)

So, echo without parentheses can take multiple parameters, which get concatenated:

   echo  "and a ", 1, 2, 3;   // comma-separated without parentheses
   echo ("and a 123");        // just one parameter with parentheses

print() can only take one parameter:

   print ("and a 123");
   print  "and a 123";

PHP Function Comments

You can get the comments of a particular method by using the ReflectionMethod class and calling ->getDocComment().

Only local connections are allowed Chrome and Selenium webdriver


    ChromeOptions options = new ChromeOptions();

    options.AddArgument("C:/Users/username/Documents/Visual Studio 2012/Projects/Interaris.Test/Interaris.Tes/bin/Debug/chromedriver.exe");

    ChromeDriver chrome = new ChromeDriver(options);

Worked for me.

How to get a web page's source code from Java

URL yahoo = new URL("");
BufferedReader in = new BufferedReader(
            new InputStreamReader(

String inputLine;

while ((inputLine = in.readLine()) != null)


Can I pass a JavaScript variable to another browser window?

Alternatively, you can add it to the URL and let the scripting language (PHP, Perl, ASP, Python, Ruby, whatever) handle it on the other side. Something like:

var x = 10;'mypage.php?x='+x);

What port is used by Java RMI connection?

Depends how you implement the RMI, you can set the registry port (registry is a "unique point of services"). If you don't set a explicit port, the registry will assume the port 1099 by default. In some cases, you have a firewall, and the firewall don't allow your rmi-client to see the stubs and objects behind the registry, because this things are running in randomically port, a different port that the registry use, and this port is blocked by firewall - of course. If you use RmiServiceExporter to configure your RmiServer, you can use the method rmiServiceExporter.setServicePort(port) to fixed the rmi port, and open this port in the firewall.

Edit: I resolve this issue with this post:

How to get numbers after decimal point?

See what I often do to obtain numbers after the decimal point in python 3:

dec= int(dec[1])

Remove gutter space for a specific div only

To add to Skelly's Bootstrap 3 no-gutter answer above (

Add the following to prevent gutters on a row containing only one column (useful when using column-wrapping: [class*='col-']:only-child, [class*='col-']:only-child
    padding-right: 0;
    padding-left: 0;

How to make unicode string with python3

the easiest way in python 3.x

text = "hi , I'm text"

Create an array or List of all dates between two dates

list = list.Where(s => s.startDate >= Input_startDate && s.endDate <= Input_endDate);


How do I remove objects from a JavaScript associative array?

var myArray = newmyArray = new Object();
myArray["firstname"] = "Bob";
myArray["lastname"] = "Smith";
myArray["age"] = 25;

var s = JSON.stringify(myArray);

s.replace(/"lastname[^,}]+,/g, '');
newmyArray = JSON.parse(p);

Without looping/iterates we get the same result.

Named colors in matplotlib

To get a full list of colors to use in plots:

import matplotlib.colors as colors
colors_list = list(colors._colors_full_map.values())

So, you can use in that way quickly:

scatter(X,Y, color=colors_list[0])
scatter(X,Y, color=colors_list[1])
scatter(X,Y, color=colors_list[2])
scatter(X,Y, color=colors_list[-1])

Vue.js dynamic images not working

I also hit this problem and it seems that both most upvoted answers work but there is a tiny problem, webpack throws an error into browser console (Error: Cannot find module './undefined' at webpackContextResolve) which is not very nice.

So I've solved it a bit differently. The whole problem with variable inside require statement is that require statement is executed during bundling and variable inside that statement appears only during app execution in browser. So webpack sees required image as undefined either way, as during compilation that variable doesn't exist.

What I did is place random image into require statement and hiding that image in css, so nobody sees it.

// template
<img class="user-image-svg" :class="[this.hidden? 'hidden' : '']" :src="userAvatar" alt />

data() {
  return {
    userAvatar: require('@/assets/avatar1.svg'),
    hidden: true

.hidden {display: none}

Image comes as part of information from database via Vuex and is mapped to component as a computed

computed: {
  user() {
    return this.$store.state.auth.user;

So once this information is available I swap initial image to the real one

watch: {
  user(userData) {
    this.userAvatar = require(`@/assets/${userData.avatar}`);
    this.hidden = false;

Div Size Automatically size of content

The easiest is:

width: fit-content;

Bootstrap 4 - Responsive cards in card-columns

Update 2019 - Bootstrap 4

You can simply use the SASS mixin to change the number of cards across in each breakpoint / grid tier.

.card-columns {
  @include media-breakpoint-only(xl) {
    column-count: 5;
  @include media-breakpoint-only(lg) {
    column-count: 4;
  @include media-breakpoint-only(md) {
    column-count: 3;
  @include media-breakpoint-only(sm) {
    column-count: 2;

SASS Demo:

Or, CSS only like this...

@media (min-width: 576px) {
    .card-columns {
        column-count: 2;

@media (min-width: 768px) {
    .card-columns {
        column-count: 3;

@media (min-width: 992px) {
    .card-columns {
        column-count: 4;

@media (min-width: 1200px) {
    .card-columns {
        column-count: 5;

CSS-only Demo:

How to retry image pull in a kubernetes Pods?

Usually in case of "ImagePullBackOff" it's retried after few seconds/minutes. In case you want to try again manually you can delete the old pod and recreate the pod. The one line command to delete and recreate the pod would be:

kubectl replace --force -f <yml_file_describing_pod>

How do you rotate a two dimensional array?

    public static void rotateMatrix(int[,] matrix)
        //C#, to rotate an N*N matrix in place
        int n = matrix.GetLength(0);
        int layers =  n / 2;
        int temp, temp2;

        for (int i = 0; i < layers; i++) // for a 5 * 5 matrix, layers will be 2, since at layer three there would be only one element, (2,2), and we do not need to rotate it with itself 
            int offset = 0;
            while (offset < n - 2 * i - 1)
                // top right <- top left 
                temp = matrix[i + offset, n - i - 1]; //top right value when offset is zero
                matrix[i + offset, n - i - 1] = matrix[i, i + offset];   

                //bottom right <- top right 
                temp2 = matrix[n - i - 1, n - i - 1 - offset]; //bottom right value when offset is zero
                matrix[n - i - 1, n - i - 1 - offset] = temp;  

                //bottom left <- bottom right 
                temp = matrix[n - i - 1 - offset, i];
                matrix[n - i - 1 - offset, i] = temp2;  

                //top left <- bottom left 
                matrix[i, i + offset] = temp; 


Concatenating date with a string in Excel

This is the numerical representation of the date. The thing you get when referring to dates from formulas like that.

You'll have to do:

= A1 & TEXT(A2, "mm/dd/yyyy")

The biggest problem here is that the format specifier is locale-dependent. It will not work/produce not what expected if the file is opened with a differently localized Excel.

Now, you could have a user-defined function:

public function AsDisplayed(byval c as range) as string
  AsDisplayed = c.Text
end function

and then

= A1 & AsDisplayed(A2)

But then there's a bug (feature?) in Excel because of which the .Text property is suddenly not available during certain stages of the computation cycle, and your formulas display #VALUE instead of what they should.

That is, it's bad either way.

How to concatenate string variables in Bash

You can concatenate without the quotes. Here is an example:

$Variable1 Open
$Variable2 Systems
$Variable3 $Variable1$Variable2
$echo $Variable3

This last statement would print "OpenSystems" (without quotes).

This is an example of a Bash script:

v3="$v1       $v2"
echo $v3            # Output: hello world
echo "$v3"          # Output: hello       world

Video auto play is not working in Safari and Chrome desktop browser

After using jQuery play() or DOM maniupulation as suggested by the other answers, it was not still working (Video wasn't autoplaying) in the Chrome for Android (Version 56.0).

As per this post in, From Chrome 53, the autoplay option is respected by the browser, if the video is muted.

So using autoplay muted attributes in video tag enables the video to be autoplayed in Chrome browsers from version 53.

Excerpt from the above link:

Muted autoplay for video is supported by Chrome for Android as of version 53. Playback will start automatically for a video element once it comes into view if both autoplay and muted are set[...]

<video autoplay muted>
    <source src="video.webm" type="video/webm" />
    <source src="video.mp4" type="video/mp4" />
  • Muted autoplay is supported by Safari on iOS 10 and later.
  • Autoplay, whether muted or not, is already supported on Android by Firefox and UC Browser: they do not block any kind of autoplay.

Does Typescript support the ?. operator? (And, what's it called?)

Operator ?. is not supported in TypeScript version 2.0.

So I use the following function:

export function o<T>(someObject: T, defaultValue: T = {} as T) : T {
    if (typeof someObject === 'undefined' || someObject === null)
        return defaultValue;
        return someObject;

the usage looks like this:


plus, you can set a default value:

o(o(o(o(test).prop1).prop2, "none")

It works really well with IntelliSense in Visual Studio.

How can I see CakePHP's SQL dump in the controller?

for cakephp 2.0 Write this function in AppModel.php

function getLastQuery()
    $dbo = $this->getDatasource();
    $logs = $dbo->getLog();
    $lastLog = end($logs['log']);
    return $lastLog['query'];

To use this in Controller Write : echo $this->YourModelName->getLastQuery();

Insert multiple rows WITHOUT repeating the "INSERT INTO ..." part of the statement?

Corresponding to INSERT (Transact-SQL) (SQL Server 2005) you can't omit INSERT INTO dbo.Blah and have to specify it every time or use another syntax/approach,

Display loading image while post with ajax

    type: 'post',
    url: 'mail.php',
    data: form.serialize(),
    beforeSend: function()
    success: function(data)
    error: function()

have fun playing arround!

if you should have quick loading times which prevent te loading showing, you can add a timeout of some sort.

I want to get the type of a variable at runtime

I think the question is incomplete. if you meant that you wish to get the type information of some typeclass then below:

If you wish to print as you have specified then:

scala>  def manOf[T: Manifest](t: T): Manifest[T] = manifest[T]
manOf: [T](t: T)(implicit evidence$1: Manifest[T])Manifest[T]

scala> val x = List(1,2,3)
x: List[Int] = List(1, 2, 3)

scala> println(manOf(x))

If you are in repl mode then

scala> :type List(1,2,3)

Or if you just wish to know what the class type then as @monkjack explains "string".getClass might solve the purpose

Setting the selected attribute on a select list using jQuery

This can be a solution

$(document).on('change', 'select', function () {
            var value = $(this).val();
            $(this).find('option[value="' + value + '"]').attr("selected", "selected");

Evaluate if list is empty JSTL

There's also the function tags, a bit more flexible:

<%@ taglib uri="" prefix="fn" %>
<c:if test="${fn:length(list) > 0}">

And here's the tag documentation.

How do I make an auto increment integer field in Django?

In Django

1 : we have default field with name "id" which is auto increment.
2 : You can define a auto increment field using AutoField field.

class Order(models.Model):
    auto_increment_id = models.AutoField(primary_key=True)
    #you use primary_key = True if you do not want to use default field "id" given by django to your model

db design

| Table      | Create Table                                                                                                                                                  |
| core_order | CREATE TABLE `core_order` (
  `auto_increment_id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`auto_increment_id`)
1 row in set (0.01 sec)

If you want to use django's default id as increment field .

class Order(models.Model):
    dd_date = models.DateTimeField(auto_now_add=True)

db design

| Table       | Create Table                                                                                                                                                    |
| core_order | CREATE TABLE `core_order` (
  `dd_date` datetime NOT NULL,
  PRIMARY KEY (`id`)

How to prevent http file caching in Apache httpd (MAMP)

Without mod_expires it will be harder to set expiration headers on your files. For anything generated you can certainly set some default headers on the answer, doing the job of mod_expires like that:

<?php header('Expires: '.gmdate('D, d M Y H:i:s \G\M\T', time() + 3600)); ?>

(taken from: Stack Overflow answer from @brianegge, where the mod_expires solution is also explained)

Now this won't work for static files, like your javascript files. As for static files there is only apache (without any expiration module) between the browser and the source file. To prevent caching of javascript files, which is done on your browser, you can use a random token at the end of the js url, something like ?rd=45642111, so the url looks like:

<script type="texte/javascript" src="my/url/myjs.js?rd=4221159546">

If this url on the page is generated by a PHP file you can simply add the random part with PHP. This way of randomizing url by simply appending random query string parameters is the base thing upôn no-cache setting of ajax jQuery request for example. The browser will never consider 2 url having different query strings to be the same, and will never use the cached version.


Note that you should alos test mod_headers. If you have mod_headers you can maybe set the Expires headers directly with the Header keyword.

Batch Renaming of Files in a Directory

Such renaming is quite easy, for example with os and glob modules:

import glob, os

def rename(dir, pattern, titlePattern):
    for pathAndFilename in glob.iglob(os.path.join(dir, pattern)):
        title, ext = os.path.splitext(os.path.basename(pathAndFilename))
                  os.path.join(dir, titlePattern % title + ext))

You could then use it in your example like this:

rename(r'c:\temp\xx', r'*.doc', r'new(%s)')

The above example will convert all *.doc files in c:\temp\xx dir to new(%s).doc, where %s is the previous base name of the file (without extension).

Store output of subprocess.Popen call in a string

import subprocess
output = str(subprocess.Popen("ntpq -p",shell = True,stdout = subprocess.PIPE, 
stderr = subprocess.STDOUT).communicate()[0])

This is one line solution

Deleting objects from an ArrayList in Java

There is a hidden cost in removing elements from an ArrayList. Each time you delete an element, you need to move the elements to fill the "hole". On average, this will take N / 2 assignments for a list with N elements.

So removing M elements from an N element ArrayList is O(M * N) on average. An O(N) solution involves creating a new list. For example.

List data = ...;
List newData = new ArrayList(data.size()); 

for (Iterator i = data.iterator(); i.hasNext(); ) {
    Object element =;

    if ((...)) {

If N is large, my guess is that this approach will be faster than the remove approach for values of M as small as 3 or 4.

But it is important to create newList large enough to hold all elements in list to avoid copying the backing array when it is expanded.

Properties order in Margin

<object Margin="left,top,right,bottom"/>
- or - 
<object Margin="left,top"/>
- or - 
<object Margin="thicknessReference"/>

See here:

How to check if a key exists in Json Object and get its value


private boolean hasKey(JSONObject jsonObject, String key) {
    return jsonObject != null && jsonObject.has(key);

  try {
        JSONObject jsonObject = new JSONObject(yourJson);
        if (hasKey(jsonObject, "labelData")) {
            JSONObject labelDataJson = jsonObject.getJSONObject("LabelData");
            if (hasKey(labelDataJson, "video")) {
                String video = labelDataJson.getString("video");
    } catch (JSONException e) {


Rotating a Vector in 3D Space

If you want to rotate a vector you should construct what is known as a rotation matrix.

Rotation in 2D

Say you want to rotate a vector or a point by ?, then trigonometry states that the new coordinates are

    x' = x cos ? - y sin ?
    y' = x sin ? + y cos ?

To demo this, let's take the cardinal axes X and Y; when we rotate the X-axis 90° counter-clockwise, we should end up with the X-axis transformed into Y-axis. Consider

    Unit vector along X axis = <1, 0>
    x' = 1 cos 90 - 0 sin 90 = 0
    y' = 1 sin 90 + 0 cos 90 = 1
    New coordinates of the vector, <x', y'> = <0, 1>  ?  Y-axis

When you understand this, creating a matrix to do this becomes simple. A matrix is just a mathematical tool to perform this in a comfortable, generalized manner so that various transformations like rotation, scale and translation (moving) can be combined and performed in a single step, using one common method. From linear algebra, to rotate a point or vector in 2D, the matrix to be built is

    |cos ?   -sin ?| |x| = |x cos ? - y sin ?| = |x'|
    |sin ?    cos ?| |y|   |x sin ? + y cos ?|   |y'|

Rotation in 3D

That works in 2D, while in 3D we need to take in to account the third axis. Rotating a vector around the origin (a point) in 2D simply means rotating it around the Z-axis (a line) in 3D; since we're rotating around Z-axis, its coordinate should be kept constant i.e. 0° (rotation happens on the XY plane in 3D). In 3D rotating around the Z-axis would be

    |cos ?   -sin ?   0| |x|   |x cos ? - y sin ?|   |x'|
    |sin ?    cos ?   0| |y| = |x sin ? + y cos ?| = |y'|
    |  0       0      1| |z|   |        z        |   |z'|

around the Y-axis would be

    | cos ?    0   sin ?| |x|   | x cos ? + z sin ?|   |x'|
    |   0      1       0| |y| = |         y        | = |y'|
    |-sin ?    0   cos ?| |z|   |-x sin ? + z cos ?|   |z'|

around the X-axis would be

    |1     0           0| |x|   |        x        |   |x'|
    |0   cos ?    -sin ?| |y| = |y cos ? - z sin ?| = |y'|
    |0   sin ?     cos ?| |z|   |y sin ? + z cos ?|   |z'|

Note 1: axis around which rotation is done has no sine or cosine elements in the matrix.

Note 2: This method of performing rotations follows the Euler angle rotation system, which is simple to teach and easy to grasp. This works perfectly fine for 2D and for simple 3D cases; but when rotation needs to be performed around all three axes at the same time then Euler angles may not be sufficient due to an inherent deficiency in this system which manifests itself as Gimbal lock. People resort to Quaternions in such situations, which is more advanced than this but doesn't suffer from Gimbal locks when used correctly.

I hope this clarifies basic rotation.

Rotation not Revolution

The aforementioned matrices rotate an object at a distance r = v(x² + y²) from the origin along a circle of radius r; lookup polar coordinates to know why. This rotation will be with respect to the world space origin a.k.a revolution. Usually we need to rotate an object around its own frame/pivot and not around the world's i.e. local origin. This can also be seen as a special case where r = 0. Since not all objects are at the world origin, simply rotating using these matrices will not give the desired result of rotating around the object's own frame. You'd first translate (move) the object to world origin (so that the object's origin would align with the world's, thereby making r = 0), perform the rotation with one (or more) of these matrices and then translate it back again to its previous location. The order in which the transforms are applied matters. Combining multiple transforms together is called concatenation or composition.


I urge you to read about linear and affine transformations and their composition to perform multiple transformations in one shot, before playing with transformations in code. Without understanding the basic maths behind it, debugging transformations would be a nightmare. I found this lecture video to be a very good resource. Another resource is this tutorial on transformations that aims to be intuitive and illustrates the ideas with animation (caveat: authored by me!).

Rotation around Arbitrary Vector

A product of the aforementioned matrices should be enough if you only need rotations around cardinal axes (X, Y or Z) like in the question posted. However, in many situations you might want to rotate around an arbitrary axis/vector. The Rodrigues' formula (a.k.a. axis-angle formula) is a commonly prescribed solution to this problem. However, resort to it only if you’re stuck with just vectors and matrices. If you're using Quaternions, just build a quaternion with the required vector and angle. Quaternions are a superior alternative for storing and manipulating 3D rotations; it's compact and fast e.g. concatenating two rotations in axis-angle representation is fairly expensive, moderate with matrices but cheap in quaternions. Usually all rotation manipulations are done with quaternions and as the last step converted to matrices when uploading to the rendering pipeline. See Understanding Quaternions for a decent primer on quaternions.

How can I get an object's absolute position on the page in Javascript?

I would definitely suggest using element.getBoundingClientRect().


Returns a text rectangle object that encloses a group of text rectangles.


var rectObject = object.getBoundingClientRect();


The returned value is a TextRectangle object which is the union of the rectangles returned by getClientRects() for the element, i.e., the CSS border-boxes associated with the element.

The returned value is a TextRectangle object, which contains read-only left, top, right and bottom properties describing the border-box, in pixels, with the top-left relative to the top-left of the viewport.

Here's a browser compatibility table taken from the linked MDN site:

|    Feature    | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
| Basic support | 1.0    | 3.0 (1.9)       | 4.0               | (Yes) | 4.0    |

It's widely supported, and is really easy to use, not to mention that it's really fast. Here's a related article from John Resig:

You can use it like this:

var logo = document.getElementById('hlogo');
var logoTextRectangle = logo.getBoundingClientRect();

console.log("logo's left pos.:", logoTextRectangle.left);
console.log("logo's right pos.:", logoTextRectangle.right);

Here's a really simple example: (you can view and edit the code by clicking "Edit in JS Bin" in the upper right corner).

Or here's another one using Chrome's console: Using element.getBoundingClientRect() in Chrome


I have to mention that the width and height attributes of the getBoundingClientRect() method's return value are undefined in Internet Explorer 8. It works in Chrome 26.x, Firefox 20.x and Opera 12.x though. Workaround in IE8: for width, you could subtract the return value's right and left attributes, and for height, you could subtract bottom and top attributes (like this).

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

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

See also here: and in a comment the given link

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

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

How can I delete a query string parameter in JavaScript?

This is a clean version remove query parameter with the URL class for today browsers:

function removeUrlParameter(url, paramKey)
  var r = new URL(url);
  return r.href;

URLSearchParams not supported on old browsers

IE, Edge (below 17) and Safari (below 10.3) do not support URLSearchParams inside URL class.


URLSearchParams only polyfill

Complete Polyfill URL and URLSearchParams to match last WHATWG specifications

How to create relationships in MySQL

Adding onto the comment by ehogue, you should make the size of the keys on both tables match. Rather than

customer_id INT( 4 ) NOT NULL ,

make it

customer_id INT( 10 ) NOT NULL ,

and make sure your int column in the customers table is int(10) also.

How to print pandas DataFrame without index

If you just want a string/json to print it can be solved with:


Buf if you want to serialize the data too or even send to a MongoDB, would be better to do something like:

document = df.to_dict(orient='list')

There are 6 ways by now to orient the data, check more in the panda docs which better fits you.

Java ArrayList of Arrays?

BTW. you should prefer coding against an Interface.

private ArrayList<String[]> action = new ArrayList<String[]>();

Should be

private List<String[]> action = new ArrayList<String[]>();

Is it not possible to stringify an Error using JSON.stringify?

We needed to serialise an arbitrary object hierarchy, where the root or any of the nested properties in the hierarchy could be instances of Error.

Our solution was to use the replacer param of JSON.stringify(), e.g.:

function jsonFriendlyErrorReplacer(key, value) {_x000D_
  if (value instanceof Error) {_x000D_
    return {_x000D_
      // Pull all enumerable properties, supporting properties on custom Errors_x000D_
      // Explicitly pull Error's non-enumerable properties_x000D_
      message: value.message,_x000D_
      stack: value.stack,_x000D_
  return value_x000D_
let obj = {_x000D_
    error: new Error('nested error message')_x000D_
console.log('Result WITHOUT custom replacer:', JSON.stringify(obj))_x000D_
console.log('Result WITH custom replacer:', JSON.stringify(obj, jsonFriendlyErrorReplacer))

ActionBarActivity is deprecated

Since the version 22.1.0, the class ActionBarActivity is deprecated. You should use AppCompatActivity.

Read here and here for more information.

What's the bad magic number error?

This is much more efficent than above.

find {directory-of-.pyc-files} -name "*.pyc" -print0 | xargs -0 rm -rf

where {directory-of-.pyc-files} is the directory that contains the compiled python files.

Programmatically navigate using react router V4

If you are targeting browser environments, you need to use react-router-dom package, instead of react-router. They are following the same approach as React did, in order to separate the core, (react) and the platform specific code, (react-dom, react-native ) with the subtle difference that you don't need to install two separate packages, so the environment packages contain everything you need. You can add it to your project as:

yarn add react-router-dom


npm i react-router-dom

The first thing you need to do is to provide a <BrowserRouter> as the top most parent component in your application. <BrowserRouter> uses the HTML5 history API and manages it for you, so you don't have to worry about instantiating it yourself and passing it down to the <BrowserRouter> component as a prop (as you needed to do in previous versions).

In V4, for navigating programatically you need to access the history object, which is available through React context, as long as you have a <BrowserRouter> provider component as the top most parent in your application. The library exposes through context the router object, that itself contains history as a property. The history interface offers several navigation methods, such as push, replace and goBack, among others. You can check the whole list of properties and methods here.

Important Note to Redux/Mobx users

If you are using redux or mobx as your state management library in your application, you may have come across issues with components that should be location-aware but are not re-rendered after triggering an URL update

That's happening because react-router passes location to components using the context model.

Both connect and observer create components whose shouldComponentUpdate methods do a shallow comparison of their current props and their next props. Those components will only re-render when at least one prop has changed. This means that in order to ensure they update when the location changes, they will need to be given a prop that changes when the location changes.

The 2 approaches for solving this are:

  • Wrap your connected component in a pathless <Route />. The current location object is one of the props that a <Route> passes to the component it renders
  • Wrap your connected component with the withRouter higher-order component, that in fact has the same effect and injects location as a prop

Setting that aside, there are four ways to navigate programatically, ordered by recommendation:

1.- Using a <Route> Component

It promotes a declarative style. Prior to v4, <Route /> components were placed at the top of your component hierarchy, having to think of your routes structure beforehand. However, now you can have <Route> components anywhere in your tree, allowing you to have a finer control for conditionally rendering depending on the URL. Route injects match, location and history as props into your component. The navigation methods (such as push, replace, goBack...) are available as properties of the history object.

There are 3 ways to render something with a Route, by using either component, render or children props, but don't use more than one in the same Route. The choice depends on the use case, but basically the first two options will only render your component if the path matches the url location, whereas with children the component will be rendered whether the path matches the location or not (useful for adjusting the UI based on URL matching).

If you want to customise your component rendering output, you need to wrap your component in a function and use the render option, in order to pass to your component any other props you desire, apart from match, location and history. An example to illustrate:

import { BrowserRouter as Router } from 'react-router-dom'

const ButtonToNavigate = ({ title, history }) => (
    onClick={() => history.push('/my-new-location')}

const SomeComponent = () => (
  <Route path="/" render={(props) => <ButtonToNavigate {...props} title="Navigate elsewhere" />} />

const App = () => (
    <SomeComponent /> // Notice how in v4 we can have any other component interleaved
    <AnotherComponent />

2.- Using withRouter HoC

This higher order component will inject the same props as Route. However, it carries along the limitation that you can have only 1 HoC per file.

import { withRouter } from 'react-router-dom'

const ButtonToNavigate = ({ history }) => (
    onClick={() => history.push('/my-new-location')}

ButtonToNavigate.propTypes = {
  history: React.PropTypes.shape({
    push: React.PropTypes.func.isRequired,

export default withRouter(ButtonToNavigate);

3.- Using a Redirect component

Rendering a <Redirect> will navigate to a new location. But keep in mind that, by default, the current location is replaced by the new one, like server-side redirects (HTTP 3xx). The new location is provided by to prop, that can be a string (URL to redirect to) or a location object. If you want to push a new entry onto the history instead, pass a push prop as well and set it to true

<Redirect to="/your-new-location" push />

4.- Accessing router manually through context

A bit discouraged because context is still an experimental API and it is likely to break/change in future releases of React

const ButtonToNavigate = (props, context) => (
    onClick={() => context.router.history.push('/my-new-location')}
    Navigate to a new location

ButtonToNavigate.contextTypes = {
  router: React.PropTypes.shape({
    history: React.PropTypes.object.isRequired,

Needless to say there are also other Router components that are meant to be for non browser ecosystems, such as <NativeRouter> that replicates a navigation stack in memory and targets React Native platform, available through react-router-native package.

For any further reference, don't hesitate to take a look at the official docs. There is also a video made by one of the co-authors of the library that provides a pretty cool introduction to react-router v4, highlighting some of the major changes.

How to get progress from XMLHttpRequest

<!DOCTYPE html>_x000D_
<p id="demo">result</p>_x000D_
<button type="button" onclick="get_post_ajax();">Change Content</button>_x000D_
<script type="text/javascript">_x000D_
 function update_progress(e)_x000D_
   if (e.lengthComputable)_x000D_
     var percentage = Math.round((e.loaded/*100);_x000D_
     console.log("percent " + percentage + '%' );_x000D_
   else _x000D_
    console.log("Unable to compute progress information since the total size is unknown");_x000D_
 function transfer_complete(e){console.log("The transfer is complete.");}_x000D_
 function transfer_failed(e){console.log("An error occurred while transferring the file.");}_x000D_
 function transfer_canceled(e){console.log("The transfer has been canceled by the user.");}_x000D_
 function get_post_ajax()_x000D_
    var xhttp;_x000D_
    if (window.XMLHttpRequest){xhttp = new XMLHttpRequest();}//code for modern browsers} _x000D_
   else{xhttp = new ActiveXObject("Microsoft.XMLHTTP");}// code for IE6, IE5    _x000D_
    xhttp.onprogress = update_progress;_x000D_
  xhttp.addEventListener("load", transfer_complete, false);_x000D_
  xhttp.addEventListener("error", transfer_failed, false);_x000D_
  xhttp.addEventListener("abort", transfer_canceled, false);    _x000D_
    xhttp.onreadystatechange = function()_x000D_
      if (xhttp.readyState == 4 && xhttp.status == 200)_x000D_
         document.getElementById("demo").innerHTML = xhttp.responseText;_x000D_
    };_x000D_"GET", "", true);_x000D_


Force drop mysql bypassing foreign key constraint

Drop database exist in all versions of MySQL. But if you want to keep the table structure, here is an idea

mysqldump --no-data --add-drop-database --add-drop-table -hHOSTNAME -uUSERNAME -p > dump.sql

This is a program, not a mysql command

Then, log into mysql and

source dump.sql;

What is the difference between char * const and const char *?

Rule of thumb: read the definition from right to left!

const int *foo;

Means "foo points (*) to an int that cannot change (const)".
To the programmer this means "I will not change the value of what foo points to".

  • *foo = 123; or foo[0] = 123; would be invalid.
  • foo = &bar; is allowed.

int *const foo;

Means "foo cannot change (const) and points (*) to an int".
To the programmer this means "I will not change the memory address that foo refers to".

  • *foo = 123; or foo[0] = 123; is allowed.
  • foo = &bar; would be invalid.

const int *const foo;

Means "foo cannot change (const) and points (*) to an int that cannot change (const)".
To the programmer this means "I will not change the value of what foo points to, nor will I change the address that foo refers to".

  • *foo = 123; or foo[0] = 123; would be invalid.
  • foo = &bar; would be invalid.

SQL Server: Multiple table joins with a WHERE clause

try this

INSERT @Application ( Id, NAME )
VALUES  ( 1,'Word' ), ( 2,'Excel' ), ( 3,'PowerPoint' )
DECLARE @software TABLE(Id INT PRIMARY KEY, ApplicationId INT, Version INT)
INSERT @software ( Id, ApplicationId, Version )
VALUES  ( 1,1, 2003 ), ( 2,1,2007 ), ( 3,2, 2003 ), ( 4,2,2007 ),( 5,3, 2003 ), ( 6,3,2007 )

INSERT @Computer ( Id, NAME )
VALUES  ( 1,'Name1' ), ( 2,'Name2' )

DECLARE @Software_Computer  TABLE(Id INT PRIMARY KEY, SoftwareId int, ComputerId int)
INSERT @Software_Computer ( Id, SoftwareId, ComputerId )
VALUES  ( 1,1, 1 ), ( 2,4,1 ), ( 3,2, 2 ), ( 4,5,2 )

SELECT Computer.Name ComputerName, Application.Name ApplicationName, MAX(Software2.Version) Version
FROM @Application Application 
JOIN @Software Software
    ON Application.ID = Software.ApplicationID
CROSS JOIN @Computer Computer
LEFT JOIN @Software_Computer Software_Computer
    ON Software_Computer.ComputerId = Computer.Id AND Software_Computer.SoftwareId = Software.Id
LEFT JOIN @Software Software2
    ON Software2.ID = Software_Computer.SoftwareID
WHERE Computer.ID = 1 
GROUP BY Computer.Name, Application.Name

CSS3 100vh not constant in mobile browser

For many of the sites I build the client will ask for a 100vh banner and just as you have found, it results in a bad "jumpy" experience on mobile when you begin to scroll. This is how I solve the problem for a smooth consistent experience across all devices:

I first set my banner element CSS to height:100vh

Then I use jQuery to get the height in pixels of my banner element and apply an inline style using this height.

var viewportHeight = $('.banner').outerHeight();
$('.banner').css({ height: viewportHeight });

Doing this solves the issue on mobile devices as when the page loads, the banner element is set to 100vh using CSS and then jQuery overrides this by putting inline CSS on my banner element which stops it from resizing when a user begins to scroll.

However, on desktop if a user resizes their browser window my banner element won't resize because it now has a fixed height set in pixels due to the above jQuery. To address this I use Mobile Detect to add a 'mobile' class to the body of my document. And then I wrap the above jQuery in an if statement:

if ($('body').hasClass('mobile')) {
  var viewportHeight = $('.banner').outerHeight();
  $('.banner').css({ height: viewportHeight });

As a result, if a user is on a mobile device the class 'mobile' is present on the body of my page and the above jQuery is executed. So my banner element will only get the inline CSS applied on mobile devices meanwhile on desktop the original 100vh CSS rule remains in place.

JavaFX Location is not set error message

This worked for me well :

 public static void main(String[] args) {

    public void start(Stage primaryStage) throws IOException {

        FXMLLoader loader = new FXMLLoader(getClass().getResource("/fxml/TestDataGenerator.fxml"));
        Parent root = loader.load();
        primaryStage.setScene(new Scene(root));;

Python string prints as [u'String']

[u'String'] is a text representation of a list that contains a Unicode string on Python 2.

If you run print(some_list) then it is equivalent to
print'[%s]' % ', '.join(map(repr, some_list)) i.e., to create a text representation of a Python object with the type list, repr() function is called for each item.

Don't confuse a Python object and its text representationrepr('a') != 'a' and even the text representation of the text representation differs: repr(repr('a')) != repr('a').

repr(obj) returns a string that contains a printable representation of an object. Its purpose is to be an unambiguous representation of an object that can be useful for debugging, in a REPL. Often eval(repr(obj)) == obj.

To avoid calling repr(), you could print list items directly (if they are all Unicode strings) e.g.: print ",".join(some_list)—it prints a comma separated list of the strings: String

Do not encode a Unicode string to bytes using a hardcoded character encoding, print Unicode directly instead. Otherwise, the code may fail because the encoding can't represent all the characters e.g., if you try to use 'ascii' encoding with non-ascii characters. Or the code silently produces mojibake (corrupted data is passed further in a pipeline) if the environment uses an encoding that is incompatible with the hardcoded encoding.

Sending a JSON to server and retrieving a JSON in return, without JQuery

Sending and receiving data in JSON format using POST method

// Sending and receiving data in JSON format using POST method
var xhr = new XMLHttpRequest();
var url = "url";"POST", url, true);
xhr.setRequestHeader("Content-Type", "application/json");
xhr.onreadystatechange = function () {
    if (xhr.readyState === 4 && xhr.status === 200) {
        var json = JSON.parse(xhr.responseText);
        console.log( + ", " + json.password);
var data = JSON.stringify({"email": "[email protected]", "password": "101010"});

Sending and receiving data in JSON format using GET method

// Sending a receiving data in JSON format using GET method
var xhr = new XMLHttpRequest();
var url = "url?data=" + encodeURIComponent(JSON.stringify({"email": "[email protected]", "password": "101010"}));"GET", url, true);
xhr.setRequestHeader("Content-Type", "application/json");
xhr.onreadystatechange = function () {
    if (xhr.readyState === 4 && xhr.status === 200) {
        var json = JSON.parse(xhr.responseText);
        console.log( + ", " + json.password);

Handling data in JSON format on the server-side using PHP

// Handling data in JSON format on the server-side using PHP
header("Content-Type: application/json");
// build a PHP variable from JSON sent using POST method
$v = json_decode(stripslashes(file_get_contents("php://input")));
// build a PHP variable from JSON sent using GET method
$v = json_decode(stripslashes($_GET["data"]));
// encode the PHP variable to JSON and send it back on client-side
echo json_encode($v);

The limit of the length of an HTTP Get request is dependent on both the server and the client (browser) used, from 2kB - 8kB. The server should return 414 (Request-URI Too Long) status if an URI is longer than the server can handle.

Note Someone said that I could use state names instead of state values; in other words I could use xhr.readyState === xhr.DONE instead of xhr.readyState === 4 The problem is that Internet Explorer uses different state names so it's better to use state values.

How to make a SIMPLE C++ Makefile

Why does everyone like to list out source files? A simple find command can take care of that easily.

Here's an example of a dirt simple C++ Makefile. Just drop it in a directory containing .C files and then type make...

appname := myapp

CXX := clang++
CXXFLAGS := -std=c++11

srcfiles := $(shell find . -name "*.C")
objects  := $(patsubst %.C, %.o, $(srcfiles))

all: $(appname)

$(appname): $(objects)
    $(CXX) $(CXXFLAGS) $(LDFLAGS) -o $(appname) $(objects) $(LDLIBS)

depend: .depend

.depend: $(srcfiles)
    rm -f ./.depend
    $(CXX) $(CXXFLAGS) -MM $^>>./.depend;

    rm -f $(objects)

dist-clean: clean
    rm -f *~ .depend

include .depend

"No Content-Security-Policy meta tag found." error in my phonegap application

There is an another issue about connection. Some android versions can connect but some cannot. So there is an another solution

in AndroidManifest.xml:

<application ... android:usesCleartextTraffic="true">_x000D_

Just add 'android:usesCleartextTraffic="true"'

and problem solved finally.

How to grep a text file which contains some binary data?

Here's what I used in a system that didn't have "strings" command installed

cat yourfilename | tr -cd "[:print:]"

This prints the text and removes unprintable characters in one fell swoop, unlike "cat -v filename" which requires some postprocessing to remove unwanted stuff. Note that some of the binary data may be printable so you'll still get some gibberish between the good stuff. I think strings removes this gibberish too if you can use that.

Get record counts for all tables in MySQL database

The code below generation the select query for all tales. Just delete last "UNION ALL" select all result and paste a new query window to run.

concat('select ''', table_name ,''' as TableName, COUNT(*) as RowCount from ' , table_name , ' UNION ALL ')  as TR FROM
information_schema.tables where 
table_schema = 'Database Name'

Changing color of Twitter bootstrap Nav-Pills

Step 1: Define a class named applycolor which can be used to apply the color you choose.

Step 2: Define what actions happens to it when it hovers. If your form background is white, then you must make sure that on hover the tab does not turn white. To achieve this use the !important clause to force this feature on hover property. We are doing this to override Bootstrap's default behavior.

Step 3: Apply the class to the Tabs which you are targetting.

CSS section:

    .nav-pills > > a, .nav-pills > > a:hover, .nav-pills > > a:focus {
        color: #fff;
        background-color: #337ab7 !important;

    .nav > li > a:hover, .nav > li > a:focus {
        text-decoration: none;
        background-color: none !important;

    .applycolor {
        background-color: #efefef;
        text-decoration: none;
        color: #fff;

    .applycolor:hover {
        background-color: #337ab7;
        text-decoration: none;
        color: #fff;

Tab Section :

<section class="form-toolbar row">
    <div class="form-title col-sm-12" id="tabs">
        <ul class="nav nav-pills nav-justified">
            <li class="applycolor"><a data-toggle="pill" href="#instance" style="font-size: 1.8rem; font-weight: 800;">My Apps</a></li>
            <li class="active applycolor"><a data-toggle="pill" href="#application" style="font-size: 1.8rem; font-weight: 800;">Apps Collection</a></li>

How to run functions in parallel?

You could use threading or multiprocessing.

Due to peculiarities of CPython, threading is unlikely to achieve true parallelism. For this reason, multiprocessing is generally a better bet.

Here is a complete example:

from multiprocessing import Process

def func1():
  print 'func1: starting'
  for i in xrange(10000000): pass
  print 'func1: finishing'

def func2():
  print 'func2: starting'
  for i in xrange(10000000): pass
  print 'func2: finishing'

if __name__ == '__main__':
  p1 = Process(target=func1)
  p2 = Process(target=func2)

The mechanics of starting/joining child processes can easily be encapsulated into a function along the lines of your runBothFunc:

def runInParallel(*fns):
  proc = []
  for fn in fns:
    p = Process(target=fn)
  for p in proc:

runInParallel(func1, func2)

SQL Server after update trigger

Try this (update, not after update)

CREATE TRIGGER [dbo].[xxx_update] ON [dbo].[MYTABLE]

        SET mytable.CHANGED_ON = GETDATE()
            ,CHANGED_BY = USER_NAME(USER_ID())
        FROM inserted
        WHERE MYTABLE.ID = inserted.ID


How to float 3 divs side by side using CSS?

I prefer this method, floats are poorly supported in older versions of IE (really?...)

.column-left{ position:absolute; left: 0px; width: 33.3%; background: red; }
.column-right{position:absolute; left:66.6%; width: 33.3%; background: green; }
.column-center{ position:absolute; left:33.3%; width: 33.3%; background: yellow; }

UPDATED : Of course, to use this technique and due to the absolute positioning you need to enclose the divs on a container and do a postprocessing to define the height of if, something like this:

    jQuery('.main').height( Math.max (

Not the most amazing thing in the world, but at least doesn't break on older IEs.

Is there a way to iterate over a range of integers?

Here's a benchmark to compare a Go for statement with a ForClause and a Go range statement using the iter package.


package main

import (


const loops = 1e6

func BenchmarkForClause(b *testing.B) {
    j := 0
    for i := 0; i < b.N; i++ {
        for j = 0; j < loops; j++ {
            j = j
    _ = j

func BenchmarkRangeIter(b *testing.B) {
    j := 0
    for i := 0; i < b.N; i++ {
        for j = range iter.N(loops) {
            j = j
    _ = j

// It does not cause any allocations.
func N(n int) []struct{} {
    return make([]struct{}, n)

func BenchmarkIterAllocs(b *testing.B) {
    var n []struct{}
    for i := 0; i < b.N; i++ {
        n = iter.N(loops)
    _ = n


$ go test -bench=. -run=.
testing: warning: no tests to run
BenchmarkForClause      2000       1260356 ns/op           0 B/op          0 allocs/op
BenchmarkRangeIter      2000       1257312 ns/op           0 B/op          0 allocs/op
BenchmarkIterAllocs 20000000            82.2 ns/op         0 B/op          0 allocs/op
ok      so/test 7.026s

Check line for unprintable characters while reading text file

While it's not hard to do this manually using BufferedReader and InputStreamReader, I'd use Guava:

List<String> lines = Files.readLines(file, Charsets.UTF_8);

You can then do whatever you like with those lines.

EDIT: Note that this will read the whole file into memory in one go. In most cases that's actually fine - and it's certainly simpler than reading it line by line, processing each line as you read it. If it's an enormous file, you may need to do it that way as per T.J. Crowder's answer.

How can I use PHP to dynamically publish an ical file to be read by Google Calendar?

  1. Exact ical format:
  2. According to the spec, it has to end in .ics

Edit: actually I'm not sure - line 6186 gives an example in .ics naming format, but it also states you can use url parameters. I don't think it matters, so long as the MIME type is correct.

Edit: Example from wikipedia:

PRODID:-//hacksw/handcal//NONSGML v1.0//EN
SUMMARY:Bastille Day Party

MIME type is configured on the server.

SQL select * from column where year = 2010

If i understand that you want all rows in the year 2010, then:

select * 
  from mytable 
 where Columnx >= '2010-01-01 00:00:00' 
       and Columnx < '2011-01-01 00:00:00'

NPM: npm-cli.js not found when running npm

It turns out the issue is due to the wrong path of node in system variable. The path is currently pointing to

(I really don't know when I modified it)

C:\Program Files\nodejs\node_modules\npm\bin

so I change to

C:\Program Files\nodejs

and it works like a charm.

ASP.NET postback with JavaScript

While Phairoh's solution seems theoretically sound, I have also found another solution to this problem. By passing the UpdatePanels id as a paramater (event target) for the doPostBack function the update panel will post back but not the entire page.


*note: second parameter is for addition event args

hope this helps someone!

EDIT: so it seems this same piece of advice was given above as i was typing :)

jquery - fastest way to remove all rows from a very large table

It's better to avoid any kind of loops, just remove all elements directly like this:

$("#mytable > tbody").html("");

Removing fields from struct or hiding them in JSON Response

Here is how I defined my structure.

type User struct {
    Username string  `json:"username" bson:"username"`
    Email    string  `json:"email" bson:"email"`
    Password *string `json:"password,omitempty" bson:"password"`
    FullName string  `json:"fullname" bson:"fullname"`

And inside my function set user.Password = nil for not to be Marshalled.

How to get current time in milliseconds in PHP?

$the_date_time = new DateTime($date_string);
$the_date_time_in_ms = ($the_date_time->format('U') * 1000) +
    ($the_date_time->format('u') / 1000);

Excel Create Collapsible Indented Row Hierarchies

A much easier way is to go to Data and select Group or Subtotal. Instant collapsible rows without messing with pivot tables or VBA.

How to download excel (.xls) file from API in postman?

If the endpoint really is a direct link to the .xls file, you can try the following code to handle downloading:

public static boolean download(final File output, final String source) {
    try {
        if (!output.createNewFile()) {
            throw new RuntimeException("Could not create new file!");
        URL url = new URL(source);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        // Comment in the code in the following line in case the endpoint redirects instead of it being a direct link
        // connection.setInstanceFollowRedirects(true);
        connection.setRequestProperty("AUTH-KEY-PROPERTY-NAME", "yourAuthKey");
        final ReadableByteChannel rbc = Channels.newChannel(connection.getInputStream());
        final FileOutputStream fos = new FileOutputStream(output);
        fos.getChannel().transferFrom(rbc, 0, 1 << 24);
        return true;
    } catch (final Exception e) {
    return false;

All you should need to do is set the proper name for the auth token and fill it in.

Example usage:

download(new File("C:\\output.xls"), "");

Creating a zero-filled pandas data frame

If you would like the new data frame to have the same index and columns as an existing data frame, you can just multiply the existing data frame by zero:

df_zeros = df * 0

Format cell if cell contains date less than today

Your first problem was you weren't using your compare symbols correctly.

< less than
> greater than
<= less than or equal to
>= greater than or equal to

To answer your other questions; get the condition to work on every cell in the column and what about blanks?

What about blanks?

Add an extra IF condition to check if the cell is blank or not, if it isn't blank perform the check. =IF(B2="","",B2<=TODAY())

Condition on every cell in column

enter image description here

How do I find out which keystore was used to sign an app?

You can do this with the apksigner tool that is part of the Android SDK:

apksigner verify --print-certs my_app.apk

You can find apksigner inside the build-tools directory. For example: ~/Library/Android/sdk/build-tools/29.0.1/apksigner

Calculate percentage saved between two numbers?

    function calculatePercentage($oldFigure, $newFigure)
    $percentChange = (($oldFigure - $newFigure) / $oldFigure) * 100;
    return round(abs($percentChange));

Copying a local file from Windows to a remote server using scp

I see this post is very old, but in my search for an answer to this very question, I was unable to unearth a solution from the vast internet super highway. I, therefore, hope I can contribute and help someone as they too find themselves stumbling for an answer. This simple, natural question does not seem to be documented anywhere.

On Windows 10 Pro connecting to Windows 10 Pro, both running OpenSSH (Windows version 7.7p1, LibreSSL 2.6.5), I was able to find a solution by trial and error. Though surprisingly simple, it took a while. I found the required syntax to be


Transferring securely from a remote system to your local system:

scp user@remotehost:\D\mySrcCode\ProjectFooBar\somefile.cpp C:\myRepo\ProjectFooBar

or going the other way around:

scp C:\myRepo\ProjectFooBar\somefile.cpp user@remotehost:\D\mySrcCode\ProjectFooBar

I also found that if spaces are in the path, the quotations should begin following the remote host name:

scp user@remotehost:"\D\My Long Folder Name\somefile.cpp" C:\myRepo\SimplerNamerBro

Also, for your particular case, I echo what Cornel says:

On Windows, use backslash, at least at conventional command console.

Kind Regards. RocketCityElectromagnetics

How to solve "The directory is not empty" error when running rmdir command in a batch script?

I had a similar problem, tried to delete an empty folder via windows explorer. Showed me the not empty error, so I thought I try it via admin cmd, but none of the answers here helped.

After I moved a file into the empty folder. I was able to delete the non empty folder

How to get selenium to wait for ajax response?

The code (C#) bellow ensures that the target element is displayed:

        internal static bool ElementIsDisplayed()
          IWebDriver driver = new ChromeDriver();
          driver.Url = "";
          WebDriverWait wait = new WebDriverWait(driver, TimeSpan.FromSeconds(10));
          By locator = By.CssSelector("input[value='csharp']:first-child");
          IWebElement myDynamicElement = wait.Until<IWebElement>((d) =>
            return d.FindElement(locator);
          return myDynamicElement.Displayed;

If the page supports jQuery it can be used the function to ensure that the target element is retrieved after all the ajax calls are finished:

 public static bool ElementIsDisplayed()
        IWebDriver driver = new ChromeDriver();
        driver.Url = "";
        WebDriverWait wait = new WebDriverWait(driver, TimeSpan.FromSeconds(10));
        By locator = By.CssSelector("input[value='csharp']:first-child");
        return wait.Until(d => ElementIsDisplayed(d, locator));

    public static bool ElementIsDisplayed(IWebDriver driver, By by)
            if (driver.FindElement(by).Displayed)
                //jQuery is supported.
                if ((bool)((IJavaScriptExecutor)driver).ExecuteScript("return window.$ != undefined"))
                    return (bool)((IJavaScriptExecutor)driver).ExecuteScript("return $.active == 0");
                    return true;
                return false;
        catch (Exception)
            return false;

How to use the read command in Bash?

To put my two cents here: on KSH, reading as is to a variable will work, because according to the IBM AIX documentation, KSH's read does affects the current shell environment:

The setting of shell variables by the read command affects the current shell execution environment.

This just resulted in me spending a good few minutes figuring out why a one-liner ending with read that I've used a zillion times before on AIX didn't work on Linux... it's because KSH does saves to the current environment and BASH doesn't!

unix - count of columns in file

Unless you're using spaces in there, you should be able to use | wc -w on the first line.

wc is "Word Count", which simply counts the words in the input file. If you send only one line, it'll tell you the amount of columns.

How can I add an item to a SelectList in MVC

I don't if anybody else has a better option...

<% if (Model.VariableName == "" || Model.VariableName== null) { %>
   <%= html.DropDpwnList("ListName", ((SelectList) ViewData["viewName"], "", 
        new{stlye=" "})%>
<% } else{ %>
<%= html.DropDpwnList("ListName", ((SelectList) ViewData["viewName"], 
        Model.VariableName, new{stlye=" "})%>
<% }>

How can I send an xml body using requests library?

Pass in the straight XML instead of a dictionary.

UICollectionView - Horizontal scroll, horizontal layout?

You can write a custom UICollectionView layout to achieve this, here is demo image of my implementation:

demo image

Here's code repository: KSTCollectionViewPageHorizontalLayout

@iPhoneDev (this maybe help you too)

Colors in JavaScript console

In Chrome & Firefox (+31) you can add CSS in console.log messages:

console.log('%c Oh my heavens! ', 'background: #222; color: #bada55');

Console color example in Chrome

The same can be applied for adding multiple CSS to same command. syntax for multi coloring chrome console messages


Why does C# XmlDocument.LoadXml(string) fail when an XML header is included?

I had the same problem when switching from absolute to relative path for my xml file. The following solves both loading and using relative source path issues. Using a XmlDataProvider, which is defined in xaml (should be possible in code too) :

        debug:PresentationTraceSources.TraceLevel="High"  /> </Window.Resources>

The data provider automatically loads the document once the source is set. Here's the code :

        m_DataProvider = this.FindResource("MyData") as XmlDataProvider;
        FileInfo file = new FileInfo("MyXmlFile.xml");

        m_DataProvider.Document = new XmlDocument();
        m_DataProvider.Source = new Uri(file.FullName);

whitespaces in the path of windows filepath

There is no problem with whitespaces in the path since you're not using the "shell" to open the file. Here is a session from the windows console to prove the point. You're doing something else wrong

Python 2.7.2 (default, Jun 12 2011, 14:24:46) [MSC v.1500 64 bit (AMD64)] on wi
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.makedirs("C:/ABC/SEM 2/testfiles")
>>> open("C:/ABC/SEM 2/testfiles/all.txt","w")
<open file 'C:/ABC/SEM 2/testfiles/all.txt', mode 'w' at 0x0000000001D95420>
>>> exit()

C:\Users\Gnibbler>dir "C:\ABC\SEM 2\testfiles"
 Volume in drive C has no label.
 Volume Serial Number is 46A0-BB64

 Directory of c:\ABC\SEM 2\testfiles

13/02/2013  10:20 PM    <DIR>          .
13/02/2013  10:20 PM    <DIR>          ..
13/02/2013  10:20 PM                 0 all.txt
               1 File(s)              0 bytes
               2 Dir(s)  78,929,309,696 bytes free


Python, add items from txt file into a list

names=[line.strip() for line in open('names.txt')]

Select values of checkbox group with jQuery

var values = $("input[name='user_group']:checked").map(function(){
      return $(this).val();

This will give you all the values of the checked boxed in an array.

How to style a checkbox using CSS

No, you still can't style the checkbox itself, but I (finally) figured out how to style an illusion while keeping the functionality of clicking a checkbox. It means that you can toggle it even if the cursor isn't perfectly still without risking selecting text or triggering drag-and-drop!

This solution probably also fits radio buttons.

The following works in Internet Explorer 9, Firefox 30.0 and Chrome 40.0.2214.91 and is just a basic example. You can still use it in combination with background images and pseudo-elements.

label {
    display: inline-block;
    position: relative; /* Needed for checkbox absolute positioning */
    background-color: #eee;
    padding: .5rem;
    border: 1px solid #000;
    border-radius: .375rem;
    font-family: "Courier New";
    font-size: 1rem;
    line-height: 1rem;

label > input[type="checkbox"] {
    display: block;
    position: absolute; /* Remove it from the flow */
    width: 100%;
    height: 100%;
    margin: -.5rem; /* Negative the padding of label to cover the "button" */
    cursor: pointer;
    opacity: 0; /* Make it transparent */
    z-index: 666; /* Place it on top of everything else */

label > input[type="checkbox"] + span {
    display: inline-block;
    width: 1rem;
    height: 1rem;
    border: 1px solid #000;
    margin-right: .5rem;

label > input[type="checkbox"]:checked + span {
    background-color: #666;

    <input type="checkbox" />
    <span>&nbsp;</span>Label text

Angular2 RC5: Can't bind to 'Property X' since it isn't a known property of 'Child Component'

If you use the Angular CLI to create your components, let's say CarComponent, it attaches app to the selector name (i.e app-car) and this throws the above error when you reference the component in the parent view. Therefore you either have to change the selector name in the parent view to let's say <app-car></app-car> or change the selector in the CarComponent to selector: 'car'

Jquery select change not firing

  // you desired code 

reference on

Vertical divider doesn't work in Bootstrap 3

I think this will bring it back using 3.0

.navbar .divider-vertical {
    height: 50px;
    margin: 0 9px;
    border-right: 1px solid #ffffff;
    border-left: 1px solid #f2f2f2;

.navbar-inverse .divider-vertical {
    border-right-color: #222222;
    border-left-color: #111111;

@media (max-width: 767px) {
    .navbar-collapse .nav > .divider-vertical {
        display: none;

Python error when trying to access list by index - "List indices must be integers, not str"

Were you expecting player to be a dict rather than a list?

>>> player=[1,2,3]
>>> player["score"]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list indices must be integers, not str
>>> player={'score':1, 'age': 2, "foo":3}
>>> player['score']

Is there a Sleep/Pause/Wait function in JavaScript?

You need to re-factor the code into pieces. This doesn't stop execution, it just puts a delay in between the parts.

function partA() {

function partB() {

How to coerce a list object to type 'double'

You can also use list subsetting to select the element you want to convert. It would be useful if your list had more than 1 element.


syntax error near unexpected token `('

Since you've got both the shell that you're typing into and the shell that sudo -s runs, you need to quote or escape twice. (EDITED fixed quoting)

sudo -su db2inst1 '/opt/ibm/db2/V9.7/bin/db2 force application \(1995\)'


sudo -su db2inst1 /opt/ibm/db2/V9.7/bin/db2 force application \\\(1995\\\)

Out of curiosity, why do you need -s? Can't you just do this:

sudo -u db2inst1 /opt/ibm/db2/V9.7/bin/db2 force application \(1995\)

Loop and get key/value pair for JSON array using jQuery

You have a string representing a JSON serialized JavaScript object. You need to deserialize it back to a JavaScript object before being able to loop through its properties. Otherwise you will be looping through each individual character of this string.

var resultJSON = '{"FirstName":"John","LastName":"Doe","Email":"[email protected]","Phone":"123 dead drive"}';
var result = $.parseJSON(resultJSON);
$.each(result, function(k, v) {
    //display the key and value pair
    alert(k + ' is ' + v);

Live demo.

public static const in TypeScript

Just simply 'export' variable and 'import' in your class

export var GOOGLE_API_URL = '';

// default err string message
export var errStringMsg = 'Something went wrong';

Now use it as,

import appConstants = require('../core/AppSettings');

error: ‘NULL’ was not declared in this scope

NULL isn't a keyword; it's a macro substitution for 0, and comes in stddef.h or cstddef, I believe. You haven't #included an appropriate header file, so g++ sees NULL as a regular variable name, and you haven't declared it.

How to make external HTTP requests with Node.js

You can use the built-in http module to do an http.request().

However if you want to simplify the API you can use a module such as superagent

Using sessions & session variables in a PHP Login Script

You need to begin the session at the top of a page or before you call session code


Set value of hidden field in a form using jQuery's ".val()" doesn't work


slots=''; hidden=''; basket = 0;

    cost_per_slot = $("#cost_per_slot").val();
    //cost_per_slot = parseFloat(cost_per_slot).toFixed(2)

    for (i=0; i< check_array.length; i++) {
        slots += check_array[i] + '\r\n';
        hidden += check_array[i].substring(0, 8) + '|';
        basket = (basket + parseFloat(cost_per_slot));

    // Populate the Selected Slots section

    // Update hidden slots_booked form element with booked slots

    // Update basket total box
    basket = basket.toFixed(2);

Replace only text inside a div using jquery

Text shouldn't be on its own. Put it into a span element.

Change it to this:

<div id="one">
       <div class="first"></div>
       <span>"Hi I am text"</span>
       <div class="second"></div>
       <div class="third"></div>
$('#one span').text('Hi I am replace');

Refresh/reload the content in Div using jquery/ajax

$("#myDiv").load(location.href+" #myDiv>*","");

Visual Studio Code always asking for git credentials

This is how I solved the issue on my computer:

  1. Open Visual Studio Code
  2. Go to File -> Preferences -> Settings
  3. Under User tab, expand Extensions and select Git

enter image description here

  1. Find Autofetch on the right pane and uncheck it

enter image description here

If '<selector>' is an Angular component, then verify that it is part of this module

Hope you are having app.module.ts. In your app.module.ts add below line-

 exports: [myComponentComponent],

Like this:

import { NgModule, Renderer } from '@angular/core';
import { HeaderComponent } from './headerComponent/header.component';
import { HeaderMainComponent } from './component';
import { RouterModule } from '@angular/router';

    declarations: [
    imports: [
    providers: [],
    bootstrap: [HeaderMainComponent],
    exports: [HeaderComponent],
export class HeaderModule { }

What are the rules for casting pointers in C?

You have a pointer to a char. So as your system knows, on that memory address there is a char value on sizeof(char) space. When you cast it up to int*, you will work with data of sizeof(int), so you will print your char and some memory-garbage after it as an integer.

Get a pixel from HTML Canvas?

// Get pixel data
var imageData = context.getImageData(x, y, width, height);

// Color at (x,y) position
var color = [];
color['red'] =[((y*(imageData.width*4)) + (x*4)) + 0];
color['green'] =[((y*(imageData.width*4)) + (x*4)) + 1];
color['blue'] =[((y*(imageData.width*4)) + (x*4)) + 2];
color['alpha'] =[((y*(imageData.width*4)) + (x*4)) + 3];

Link entire table row?

Unfortunately, no. Not with HTML and CSS. You need an a element to make a link, and you can't wrap an entire table row in one.

The closest you can get is linking every table cell. Personally I'd just link one cell and use JavaScript to make the rest clickable. It's good to have at least one cell that really looks like a link, underlined and all, for clarity anyways.

Here's a simple jQuery snippet to make all table rows with links clickable (it looks for the first link and "clicks" it)

$("table").on("click", "tr", function(e) {
    if ($("a,input")) // anything else you don't want to trigger the click

    location.href = $(this).find("a").attr("href");

Writing data into CSV file in C#


Back in my naïve days, I suggested doing this manually (it was a simple solution to a simple question), however due to this becoming more and more popular, I'd recommend using the library CsvHelper that does all the safety checks, etc.

CSV is way more complicated than what the question/answer suggests.

Original Answer

As you already have a loop, consider doing it like this:

//before your loop
    var csv = new StringBuilder();

//in your loop
    var first = reader[0].ToString();
    var second = image.ToString();
    //Suggestion made by KyleMit
    var newLine = string.Format("{0},{1}", first, second);

//after your loop
    File.WriteAllText(filePath, csv.ToString());

Or something to this effect. My reasoning is: you won't be need to write to the file for every item, you will only be opening the stream once and then writing to it.

You can replace

File.WriteAllText(filePath, csv.ToString());


File.AppendAllText(filePath, csv.ToString());

if you want to keep previous versions of csv in the same file

C# 6

If you are using c# 6.0 then you can do the following

var newLine = $"{first},{second}"


Here is a link to a question that explains what Environment.NewLine does.

How do I get the position selected in a RecyclerView?

To complement @tyczj answer:

Generic Adapter Pseido code:

public abstract class GenericRecycleAdapter<T, K extends RecyclerView.ViewHolder> extends RecyclerView.Adapter{ 

private List<T> mList;
//default implementation code 

public abstract int getLayout();

    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(getLayout(), parent, false);
        return getCustomHolder(v);

    public Holders.TextImageHolder getCustomHolder(View v) {
        return new Holders.TextImageHolder(v){
            public void onClick(View v) {

abstract void onItem(T t);

public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    onSet(mList.get(position), (K) holder);


public abstract void onSet(T item, K holder);



public class Holders  {

    public static class TextImageHolder extends RecyclerView.ViewHolder implements View.OnClickListener{

        public TextView text;

        public TextImageHolder(View itemView) {
            text = (TextView) itemView.findViewById(;


        public void onClick(View v) {



Adapter usage:

public class CategoriesAdapter extends GenericRecycleAdapter<Category, Holders.TextImageHolder> {

    public CategoriesAdapter(List<Category> list, Context context) {
        super(list, context);

    void onItem(Category category) {


    public int getLayout() {
        return R.layout.categories_row;

    public void onSet(Category item, Holders.TextImageHolder holder) {



Row names & column names in R

Just to expand a little on Dirk's example:

It helps to think of a data frame as a list with equal length vectors. That's probably why names works with a data frame but not a matrix.

The other useful function is dimnames which returns the names for every dimension. You will notice that the rownames function actually just returns the first element from dimnames.

Regarding rownames and row.names: I can't tell the difference, although rownames uses dimnames while row.names was written outside of R. They both also seem to work with higher dimensional arrays:

>a <- array(1:5, 1:4)
> a[1,,,]
> rownames(a) <- "a"
> row.names(a)
[1] "a"
> a
, , 1, 1    
  [,1] [,2]
a    1    2

> dimnames(a)
[1] "a"




Getting Class type from String

It should be:

Class.forName(String classname)

array_push() with key value pair

Just do that:

$data = [
    "dog" => "cat"

array_push($data, ['cat' => 'wagon']);

*In php 7 and higher, array is creating using [], not ()

error: Unable to find vcvarsall.bat

calling import setuptools will monkey patch distutils to force compatibility with Visual Studio. Calling vcvars32.bat manually will setup the virtual environment and prevent other common errors the compiler will throw. For VS 2017 the file is located at

"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat"

Here is the setup script I use to quickly compile .pyx files to .pyd: (Note: it uses the 3rd party module send2trash

import sys, os, time, platform, subprocess
from setuptools import setup, find_packages
from Cython.Build import cythonize
from traceback import format_exc

#   from cython_setup import run
#   run(pyx_path)

# vcvars = r"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat"

# NOTE: to use visual studio 2017 you must have setuptools version 34+
vcvars = r"C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars32.bat"

def _build_ext():
        pyx_path = sys.argv.pop(-1)
        pyx_path = os.path.abspath(pyx_path)
        if not os.path.exists(pyx_path):
            raise FileNotFoundError(f"{pyx_path} does not exist")
        project_name = sys.argv.pop(-1)

        print("cwd: %s" % os.getcwd())
            # cmdclass = {'build_ext': build_ext},
            # ext_modules=cythonize(extensions)
                                  compiler_directives={'language_level': 3, 'infer_types': True, 'binding': False},
            # include_dirs = [numpy.get_include()]

def retry(func):
    def wrapper(*args, **kw):
        tries = 0
        while True:
                return func(*args, **kw)
            except Exception:
                tries += 1
                if tries > 4:

    return wrapper

def cleanup(pyx_path):
    from send2trash import send2trash
    c_file = os.path.splitext(pyx_path)[0] + ".c"
    if os.path.exists(c_file):

    if os.path.exists("build"):

def move_pyd_files(pyx_path):
    pyx_dir = os.path.dirname(pyx_path)
    build_dir = os.path.join(pyx_dir, "build")
    if not os.path.exists(build_dir):
        raise RuntimeError(f"build_dir {build_dir} did not exist....")
    found_pyd = False
    for top, dirs, nondirs in os.walk(build_dir):
        for name in nondirs:
            if name.lower().endswith(".pyd") or name.lower().endswith(".so"):
                found_pyd = True
                old_path = os.path.join(top, name)
                new_path = os.path.join(pyx_dir, name)
                if os.path.exists(new_path):
                    print(f"removing {new_path}")
                print(f"file created at {new_path}")
                os.rename(old_path, new_path)
    if not found_pyd:
        raise RuntimeError("Never found .pyd file to move")

def run(pyx_path):
    :param pyx_path:
    :type pyx_path:
    :return: this function creates the batch file, which in turn calls this module, which calls cythonize, once done
    the batch script deletes itself... I'm sure theres a less convoluted way of doing this, but it works
        project_name = os.path.splitext(os.path.basename(pyx_path))[0]
        run_script(project_name, os.path.abspath(pyx_path))

def run_script(project_name, pyx_path):
    dirname = os.path.dirname(pyx_path)
    # ------------------------------
    if os.path.exists(vcvars):
        #  raise RuntimeError(
        # f"Could not find vcvars32.bat at {vcvars}\nis Visual Studio Installed?\nIs setuptools version > 34?")
        subprocess.check_call(f'call "{vcvars}"', shell=True)

    cmd = "python" if platform.system() == "Windows" else "python3"
    subprocess.check_call(f'{cmd} "{__file__}" build_ext "{project_name}" "{pyx_path}"', shell=True)

if len(sys.argv) > 2:

Add a reference column migration in Rails 4

Create a migration file

rails generate migration add_references_to_uploads user:references

Default foreign key name

This would create a user_id column in uploads table as a foreign key

class AddReferencesToUploads < ActiveRecord::Migration[5.2]
  def change
    add_reference :uploads, :user, foreign_key: true

user model:

class User < ApplicationRecord
  has_many :uploads

upload model:

class Upload < ApplicationRecord
  belongs_to :user

Customize foreign key name:

add_reference :uploads, :author, references: :user, foreign_key: true

This would create an author_id column in the uploads tables as the foreign key.

user model:

class User < ApplicationRecord
  has_many :uploads, foreign_key: 'author_id'

upload model:

class Upload < ApplicationRecord
  belongs_to :user

String.Format alternative in C++

You can just concatenate the strings and build a command line.

std::string command = a + ' ' + b + " > " + c;

You don't need any extra libraries for this.

Using an IF Statement in a MySQL SELECT query

try this code worked for me

SELECT user_display_image AS user_image,
       user_display_name AS user_name,
       (CASE WHEN invitee_status = 1 THEN "attending"
             WHEN invitee_status = 2 THEN "unsure"
             WHEN invitee_status = 3 THEN "declined"
             WHEN invitee_status = 0 THEN "notreviwed"
       END) AS invitee_status
  FROM your_table

How to extract text from an existing docx file using python-docx

It seems that there is no official solution for this problem, but there is a workaround posted here

just update this file "...\site-packages\docx\"

# add
import re
import sys

# add
def remove_hyperlink_tags(xml):
    if (sys.version_info > (3, 0)):
        xml = xml.decode('utf-8')
    xml = xml.replace('</w:hyperlink>', '')
    xml = re.sub('<w:hyperlink[^>]*>', '', xml)
    if (sys.version_info > (3, 0)):
        xml = xml.encode('utf-8')
    return xml
# update
def parse_xml(xml):
    Return root lxml element obtained by parsing XML character string in
    *xml*, which can be either a Python 2.x string or unicode. The custom
    parser is used, so custom element classes are produced for elements in
    *xml* that have them.
    root_element = etree.fromstring(remove_hyperlink_tags(xml), oxml_parser)
    return root_element

and of course don't forget to mention in the documentation that use are changing the official library

Java String new line

You can also use System.lineSeparator():

String x = "Hello," + System.lineSeparator() + "there";

How to use boolean datatype in C?

We can use enum type for this.We don't require a library. For example

           enum {false,true};

the value for false will be 0 and the value for true will be 1.

Copy file(s) from one project to another using post build event...VS2010

xcopy "$(TargetDir)*$(TargetExt)" "$(SolutionDir)\Scripts\MigrationScripts\Library\" /F /R /Y /I

/F – Displays full source & target file names

/R – This will overwrite read-only files

/Y – Suppresses prompting to overwrite an existing file(s)

/I – Assumes that destination is directory (but must ends with )

A little trick – in target you must end with character \ to tell xcopy that target is directory and not file!

How to preserve aspect ratio when scaling image using one (CSS) dimension in IE6?

Well, I can think of a CSS hack that will resolve this issue.

You could add the following line in your CSS file:

* html .blog_list div.postbody img { width:75px; height: SpecifyHeightHere; } 

The above code will only be seen by IE6. The aspect ratio won't be perfect, but you could make it look somewhat normal. If you really wanted to make it perfect, you would need to write some javascript that would read the original picture width, and set the ratio accordingly to specify a height.

Adding calculated column(s) to a dataframe in pandas

You could have is_hammer in terms of row["Open"] etc. as follows

def is_hammer(rOpen,rLow,rClose,rHigh):
    return lower_wick_at_least_twice_real_body(rOpen,rLow,rClose) \
       and closed_in_top_half_of_range(rHigh,rLow,rClose)

Then you can use map:

df["isHammer"] = map(is_hammer, df["Open"], df["Low"], df["Close"], df["High"])

Decimal number regular expression, where digit after decimal is optional

Try this regex:


\d+ digits before optional decimal
.? optional decimal(optional due to the ? quantifier)
\d* optional digits after decimal

Calling a Sub and returning a value

Private Sub Main()
    Dim value = getValue()
    'do something with value
End Sub

Private Function getValue() As Integer
    Return 3
End Function

jQuery scroll() detect when user stops scrolling

function scrolled() {
    //do by scroll start
        //do by scroll end
    }, 500)

very small Version with start and end ability

How do you synchronise projects to GitHub with Android Studio?

For existing project end existing repository with files:

git init
git remote add origin <.git>
git checkout -b master
git branch --set-upstream-to=origin/master master
git pull --allow-unrelated-histories

How to update PATH variable permanently from Windows command line?

This script

includes all the necessary Windows API calls which can be refactored for your needs. It is actually an AutoHotkey GUI to change the System PATH easily. Needs to be run as an Administrator.

Github permission denied: ssh add agent has no identities

Run the following commands:

ssh-keygen -t rsa
ssh-add /Users/*yourUserNameHere*/.ssh/id_rsa** 
pbcopy < ~/.ssh/**

Go to your Github account :

1) Click : SSH and GPG keys

2) New SSH Key and Past it there

3) Add SSH Key


Get the Query Executed in Laravel 3/4

Since the profiler is not yet out in Laravel 4, I've created this helper function to see the SQL being generated:

    public static function q($all = true) 
        $queries = DB::getQueryLog();

        if($all == false) {
            $last_query = end($queries);
            return $last_query;

        return $queries;

NOTE: Set the $all flag to false if you only want the last SQL query.

I keep this sort of functions in a class called DBH.php (short for Database Helper) so I can call it from anywhere like this:


Here is the output I get: enter image description here

In case you are wondering, I use Kint for the dd() formatting.

How can I include css files using node, express, and ejs?

1.Create a new folder named 'public' if none exists.

2.Create a new folder named 'css' under the newly created 'public' folder

3.create your css file under the public/css path

4.On your html link css i.e <link rel="stylesheet" type="text/css" href="/css/style.css">

// note the href uses a slash(/) before and you do not need to include the 'public'

5.On your app.js include : app.use(express.static('public'));

Boom.It works!!

Flexbox: 4 items per row

I believe this example is more barebones and easier to understand then @dowomenfart.

.child {
    display: inline-block;
    margin: 0 1em;
    flex-grow: 1;
    width: calc(25% - 2em);

This accomplishes the same width calculations while cutting straight to the meat. The math is way easier and em is the new standard due to its scalability and mobile-friendliness.

How to split() a delimited string to a List<String>

string.Split() returns an array - you can convert it to a list using ToList():

listStrLineElements = line.Split(',').ToList();

Note that you need to import System.Linq to access the .ToList() function.

How to manually set an authenticated user in Spring Security / SpringMVC

Turn on debug logging to get a better picture of what is going on.

You can tell if the session cookies are being set by using a browser-side debugger to look at the headers returned in HTTP responses. (There are other ways too.)

One possibility is that SpringSecurity is setting secure session cookies, and your next page requested has an "http" URL instead of an "https" URL. (The browser won't send a secure cookie for an "http" URL.)

javac : command not found

Install same version javac as your JRE

yum install java-devel

How do I fetch only one branch of a remote Git repository?

git version: 2.74

This is how I do it:

git remote add [REMOTE-NAME] [REMOTE-URL]
git fetch [REMOTE-NAME] -- [BRANCH]

How to get the mouse position without events (without moving the mouse)?

Real answer: No, it's not possible.

OK, I have just thought of a way. Overlay your page with a div that covers the whole document. Inside that, create (say) 2,000 x 2,000 <a> elements (so that the :hover pseudo-class will work in IE 6, see), each 1 pixel in size. Create a CSS :hover rule for those <a> elements that changes a property (let's say font-family). In your load handler, cycle through each of the 4 million <a> elements, checking currentStyle / getComputedStyle() until you find the one with the hover font. Extrapolate back from this element to get the co-ordinates within the document.


why is plotting with Matplotlib so slow?

For the first solution proposed by Joe Kington ( .copy_from_bbox & .draw_artist & canvas.blit), I had to capture the backgrounds after the fig.canvas.draw() line, otherwise the background had no effect and I got the same result as you mentioned. If you put it after the it still does not work as proposed by Michael Browne.

So just put the background line after the canvas.draw():


# We need to draw the canvas before we start animating...

# Let's capture the background of the figure
backgrounds = [fig.canvas.copy_from_bbox(ax.bbox) for ax in axes]

How can I extract all values from a dictionary in Python?

If you want all of the values, use this:


If you want all of the keys, use this:


IF you want all of the items (both keys and values), I would use this:


LDAP filter for blank (empty) attribute

I needed to do a query to get me all groups with a managedBy value set (not empty) and this gave some nice results:


Use curly braces to initialize a Set in Python

There are two obvious issues with the set literal syntax:

my_set = {'foo', 'bar', 'baz'}
  1. It's not available before Python 2.7

  2. There's no way to express an empty set using that syntax (using {} creates an empty dict)

Those may or may not be important to you.

The section of the docs outlining this syntax is here.

How to view method information in Android Studio?

If you just need a shortcut, then it is Ctrl + Q on Linux (and Windows). Just hover the mouse on the method and press Ctrl + Q to see the doc.

Basic Authentication Using JavaScript

After Spending quite a bit of time looking into this, i came up with the solution for this; In this solution i am not using the Basic authentication but instead went with the oAuth authentication protocol. But to use Basic authentication you should be able to specify this in the "setHeaderRequest" with minimal changes to the rest of the code example. I hope this will be able to help someone else in the future:

var token_ // variable will store the token
var userName = "clientID"; // app clientID
var passWord = "secretKey"; // app clientSecret
var caspioTokenUrl = ""; // Your application token endpoint  
var request = new XMLHttpRequest(); 

function getToken(url, clientID, clientSecret) {
    var key;      "POST", url, true); 
    request.setRequestHeader("Content-type", "application/json");
    request.send("grant_type=client_credentials&client_id="+clientID+"&"+"client_secret="+clientSecret); // specify the credentials to receive the token on request
    request.onreadystatechange = function () {
        if (request.readyState == request.DONE) {
            var response = request.responseText;
            var obj = JSON.parse(response); 
            key = obj.access_token; //store the value of the accesstoken
            token_ = key; // store token in your global variable "token_" or you could simply return the value of the access token from the function
// Get the token
getToken(caspioTokenUrl, userName, passWord);

If you are using the Caspio REST API on some request it may be imperative that you to encode the paramaters for certain request to your endpoint; see the Caspio documentation on this issue;

NOTE: encodedParams is NOT used in this example but was used in my solution.

Now that you have the token stored from the token endpoint you should be able to successfully authenticate for subsequent request from the caspio resource endpoint for your application

function CallWebAPI() {
    var request_ = new XMLHttpRequest();        
    var encodedParams = encodeURIComponent(params);"GET", "", true);
    request_.setRequestHeader("Authorization", "Bearer "+ token_);
    request_.onreadystatechange = function () {
        if (request_.readyState == 4 && request_.status == 200) {
            var response = request_.responseText;
            var obj = JSON.parse(response); 
            // handle data as needed... 


This solution does only considers how to successfully make the authenticated request using the Caspio API in pure javascript. There are still many flaws i am sure...

Difference between using Throwable and Exception in a try catch

The first one catches all subclasses of Throwable (this includes Exception and Error), the second one catches all subclasses of Exception.

Error is programmatically unrecoverable in any way and is usually not to be caught, except for logging purposes (which passes it through again). Exception is programmatically recoverable. Its subclass RuntimeException indicates a programming error and is usually not to be caught as well.

jQuery Scroll To bottom of the page


var el = document.getElementById("el");
el.scrollTop = el.scrollHeight - el.scrollTop;

C - casting int to char and append char to char

Casting int to char involves losing data and the compiler will probably warn you.

Extracting a particular byte from an int sounds more reasonable and can be done like this:

number & 0x000000ff; /* first byte */
(number & 0x0000ff00) >> 8; /* second byte */
(number & 0x00ff0000) >> 16; /* third byte */
(number & 0xff000000) >> 24; /* fourth byte */

How do I install imagemagick with homebrew?

brew install imagemagick

Don't forget to install also gs which is a dependency if you want to convert pdf to images for example :

brew install ghostscript

What is a segmentation fault?

There are enough definitions of segmentation fault, i would like to quote few examples which i came across while programming, which might seem silly mistakes, but will waste a lot of time.

  1. you can get segmentation fault in below case while argumet type mismatch in printf

    #include<stdio.h> int main(){
    int a = 5; printf("%s",a); return 0; }

output : Segmentation Fault (SIGSEGV)

  1. when you forgot to allocate memory to a pointer, but trying to use it.

     typedef struct{
       int a;
    int main(){
      myStruct *s;
      /* few lines of code */
      s->a = 5;
      return 0;

output : Segmentation Fault (SIGSEGV)

CSS : center form in page horizontally and vertically

How about using a grid? it's 2019 and support is reasonable

body {_x000D_
  margin: 0;_x000D_
  padding: 0;_x000D_
  background-color: red;_x000D_
.content {_x000D_
  display: grid;_x000D_
  background-color: bisque;_x000D_
  height: 100vh;_x000D_
  place-items: center;_x000D_
<!DOCTYPE html>_x000D_
<div class="content">_x000D_
  <form action="#" method="POST">_x000D_
      <label for="name">Name:</label>_x000D_
      <input type="text" id="name" name="user_name">_x000D_
    <button type="button" formmethod="POST" formaction="#">Submit</button>_x000D_

How to solve this java.lang.NoClassDefFoundError: org/apache/commons/io/output/DeferredFileOutputStream?

use maven dependency


or download commons-io.1.3.2.jar to your lib folder

How do I profile memory usage in Python?

Since the accepted answer and also the next highest voted answer have, in my opinion, some problems, I'd like to offer one more answer that is based closely on Ihor B.'s answer with some small but important modifications.

This solution allows you to run profiling on either by wrapping a function call with the profile function and calling it, or by decorating your function/method with the @profile decorator.

The first technique is useful when you want to profile some third-party code without messing with its source, whereas the second technique is a bit "cleaner" and works better when you are don't mind modifying the source of the function/method you want to profile.

I've also modified the output, so that you get RSS, VMS, and shared memory. I don't care much about the "before" and "after" values, but only the delta, so I removed those (if you're comparing to Ihor B.'s answer).

Profiling code

import time
import os
import psutil
import inspect

def elapsed_since(start):
    #return time.strftime("%H:%M:%S", time.gmtime(time.time() - start))
    elapsed = time.time() - start
    if elapsed < 1:
        return str(round(elapsed*1000,2)) + "ms"
    if elapsed < 60:
        return str(round(elapsed, 2)) + "s"
    if elapsed < 3600:
        return str(round(elapsed/60, 2)) + "min"
        return str(round(elapsed / 3600, 2)) + "hrs"

def get_process_memory():
    process = psutil.Process(os.getpid())
    mi = process.memory_info()
    return mi.rss, mi.vms, mi.shared

def format_bytes(bytes):
    if abs(bytes) < 1000:
        return str(bytes)+"B"
    elif abs(bytes) < 1e6:
        return str(round(bytes/1e3,2)) + "kB"
    elif abs(bytes) < 1e9:
        return str(round(bytes / 1e6, 2)) + "MB"
        return str(round(bytes / 1e9, 2)) + "GB"

def profile(func, *args, **kwargs):
    def wrapper(*args, **kwargs):
        rss_before, vms_before, shared_before = get_process_memory()
        start = time.time()
        result = func(*args, **kwargs)
        elapsed_time = elapsed_since(start)
        rss_after, vms_after, shared_after = get_process_memory()
        print("Profiling: {:>20}  RSS: {:>8} | VMS: {:>8} | SHR {"
              ":>8} | time: {:>8}"
            .format("<" + func.__name__ + ">",
                    format_bytes(rss_after - rss_before),
                    format_bytes(vms_after - vms_before),
                    format_bytes(shared_after - shared_before),
        return result
    if inspect.isfunction(func):
        return wrapper
    elif inspect.ismethod(func):
        return wrapper(*args,**kwargs)

Example usage, assuming the above code is saved as

from profile import profile
from time import sleep
from sklearn import datasets # Just an example of 3rd party function call

# Method 1
run_profiling = profile(datasets.load_digits)
data = run_profiling()

# Method 2
def my_function():
    # do some stuff
    a_list = []
    for i in range(1,100000):
    return a_list

res = my_function()

This should result in output similar to the below:

Profiling:        <load_digits>  RSS:   5.07MB | VMS:   4.91MB | SHR  73.73kB | time:  89.99ms
Profiling:        <my_function>  RSS:   1.06MB | VMS:   1.35MB | SHR       0B | time:   8.43ms

A couple of important final notes:

  1. Keep in mind, this method of profiling is only going to be approximate, since lots of other stuff might be happening on the machine. Due to garbage collection and other factors, the deltas might even be zero.
  2. For some unknown reason, very short function calls (e.g. 1 or 2 ms) show up with zero memory usage. I suspect this is some limitation of the hardware/OS (tested on basic laptop with Linux) on how often memory statistics are updated.
  3. To keep the examples simple, I didn't use any function arguments, but they should work as one would expect, i.e. profile(my_function, arg) to profile my_function(arg)

SMTP server response: 530 5.7.0 Must issue a STARTTLS command first

Problem Solved,

I edited the file /etc/postfix/

and commented

-o smtpd_relay_restrictions=permit_sasl_authenticated,reject

and changed the line from

-o smtpd_tls_security_level=encrypt 


-o smtpd_tls_security_level=may

And worked on fine

Execute a command line binary with Node.js

I just wrote a Cli helper to deal with Unix/windows easily.


define(["require", "exports"], function (require, exports) {
     * Helper to use the Command Line Interface (CLI) easily with both Windows and Unix environments.
     * Requires underscore or lodash as global through "_".
    var Cli = (function () {
        function Cli() {}
             * Execute a CLI command.
             * Manage Windows and Unix environment and try to execute the command on both env if fails.
             * Order: Windows -> Unix.
             * @param command                   Command to execute. ('grunt')
             * @param args                      Args of the command. ('watch')
             * @param callback                  Success.
             * @param callbackErrorWindows      Failure on Windows env.
             * @param callbackErrorUnix         Failure on Unix env.
        Cli.execute = function (command, args, callback, callbackErrorWindows, callbackErrorUnix) {
            if (typeof args === "undefined") {
                args = [];
  , args, callback, function () {

                try {
                    Cli.unix(command, args, callback, callbackErrorUnix);
                } catch (e) {
                    console.log('------------- Failed to perform the command: "' + command + '" on all environments. -------------');

         * Execute a command on Windows environment.
         * @param command       Command to execute. ('grunt')
         * @param args          Args of the command. ('watch')
         * @param callback      Success callback.
         * @param callbackError Failure callback.
         */ = function (command, args, callback, callbackError) {
            if (typeof args === "undefined") {
                args = [];
            try {
                Cli._execute(process.env.comspec, _.union(['/c', command], args));
                callback(command, args, 'Windows');
            } catch (e) {
                callbackError(command, args, 'Windows');

         * Execute a command on Unix environment.
         * @param command       Command to execute. ('grunt')
         * @param args          Args of the command. ('watch')
         * @param callback      Success callback.
         * @param callbackError Failure callback.
        Cli.unix = function (command, args, callback, callbackError) {
            if (typeof args === "undefined") {
                args = [];
            try {
                Cli._execute(command, args);
                callback(command, args, 'Unix');
            } catch (e) {
                callbackError(command, args, 'Unix');

         * Execute a command no matters what's the environment.
         * @param command   Command to execute. ('grunt')
         * @param args      Args of the command. ('watch')
         * @private
        Cli._execute = function (command, args) {
            var spawn = require('child_process').spawn;
            var childProcess = spawn(command, args);

            childProcess.stdout.on("data", function (data) {

            childProcess.stderr.on("data", function (data) {
        return Cli;
    exports.Cli = Cli;

Typescript original source file:

 * Helper to use the Command Line Interface (CLI) easily with both Windows and Unix environments.
 * Requires underscore or lodash as global through "_".
export class Cli {

     * Execute a CLI command.
     * Manage Windows and Unix environment and try to execute the command on both env if fails.
     * Order: Windows -> Unix.
     * @param command                   Command to execute. ('grunt')
     * @param args                      Args of the command. ('watch')
     * @param callback                  Success.
     * @param callbackErrorWindows      Failure on Windows env.
     * @param callbackErrorUnix         Failure on Unix env.
    public static execute(command: string, args: string[] = [], callback ? : any, callbackErrorWindows ? : any, callbackErrorUnix ? : any) {, args, callback, function () {

            try {
                Cli.unix(command, args, callback, callbackErrorUnix);
            } catch (e) {
                console.log('------------- Failed to perform the command: "' + command + '" on all environments. -------------');

     * Execute a command on Windows environment.
     * @param command       Command to execute. ('grunt')
     * @param args          Args of the command. ('watch')
     * @param callback      Success callback.
     * @param callbackError Failure callback.
    public static windows(command: string, args: string[] = [], callback ? : any, callbackError ? : any) {
        try {
            Cli._execute(process.env.comspec, _.union(['/c', command], args));
            callback(command, args, 'Windows');
        } catch (e) {
            callbackError(command, args, 'Windows');

     * Execute a command on Unix environment.
     * @param command       Command to execute. ('grunt')
     * @param args          Args of the command. ('watch')
     * @param callback      Success callback.
     * @param callbackError Failure callback.
    public static unix(command: string, args: string[] = [], callback ? : any, callbackError ? : any) {
        try {
            Cli._execute(command, args);
            callback(command, args, 'Unix');
        } catch (e) {
            callbackError(command, args, 'Unix');

     * Execute a command no matters what's the environment.
     * @param command   Command to execute. ('grunt')
     * @param args      Args of the command. ('watch')
     * @private
    private static _execute(command, args) {
        var spawn = require('child_process').spawn;
        var childProcess = spawn(command, args);

        childProcess.stdout.on("data", function (data) {

        childProcess.stderr.on("data", function (data) {

Example of use:

    Cli.execute(Grunt._command, args, function (command, args, env) {
        console.log('Grunt has been automatically executed. (' + env + ')');

    }, function (command, args, env) {
        console.error('------------- Windows "' + command + '" command failed, trying Unix... ---------------');

    }, function (command, args, env) {
        console.error('------------- Unix "' + command + '" command failed too. ---------------');

How to run console application from Windows Service?

I use this class:

class ProcessWrapper : Process, IDisposable
    public enum PipeType { StdOut, StdErr }

    public class Output
        public string Message { get; set; }
        public PipeType Pipe { get; set; }
        public override string ToString()
            return $"{Pipe}: {Message}";

    private readonly string _command;
    private readonly string _args;
    private readonly bool _showWindow;
    private bool _isDisposed;

    private readonly Queue<Output> _outputQueue = new Queue<Output>();

    private readonly ManualResetEvent[] _waitHandles = new ManualResetEvent[2];
    private readonly ManualResetEvent _outputSteamWaitHandle = new ManualResetEvent(false);

    public ProcessWrapper(string startCommand, string args, bool showWindow = false)
        _command = startCommand;
        _args = args;
        _showWindow = showWindow;

    public IEnumerable<string> GetMessages()
        while (!_isDisposed)
            if (_outputQueue.Any())
                yield return _outputQueue.Dequeue().ToString();

    public void SendCommand(string command)

    public new int Start()
        ProcessStartInfo startInfo = new ProcessStartInfo
            FileName = _command,
            Arguments = _args,
            UseShellExecute = false,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            RedirectStandardInput = true,
            CreateNoWindow = !_showWindow
        StartInfo = startInfo;

        OutputDataReceived += delegate (object sender, DataReceivedEventArgs args)
            if (args.Data == null)
            else if (args.Data.Length > 0)
                _outputQueue.Enqueue(new Output { Message = args.Data, Pipe = PipeType.StdOut });

        ErrorDataReceived += delegate (object sender, DataReceivedEventArgs args)
            if (args.Data == null)
            else if (args.Data.Length > 0)
                _outputQueue.Enqueue(new Output { Message = args.Data, Pipe = PipeType.StdErr });


        _waitHandles[0] = new ManualResetEvent(false);
        _waitHandles[1] = new ManualResetEvent(false);

        return Id;

    public new void Dispose()
        if (!WaitForExit(1000))
        if (WaitForExit(1000))
        _isDisposed = true;

Can I embed a .png image into an html page?

The 64base method works for large images as well, I use that method to embed all the images into my website, and it works every time. I've done with files up to 2Mb size, jpg and png.

Getting 404 Not Found error while trying to use ErrorDocument

The ErrorDocument directive, when supplied a local URL path, expects the path to be fully qualified from the DocumentRoot. In your case, this means that the actual path to the ErrorDocument is

ErrorDocument 404 /hellothere/error/404page.html

Height of an HTML select box (dropdown)


The part that drops down is set to either:

  1. The height needed to show all entries, or
  2. The height needed to show x entries (with scrollbars to see remaining), where x is
    • 20 in Firefox & Chrome
    • 30 in IE 6, 7, 8
    • 16 for Opera 10
    • 14 for Opera 11
    • 22 for Safari 4
    • 18 for Safari 5
    • 11 in IE 5.0, 5.5
  3. In IE/Edge, if there are no options, a stupidly high list of 11 blanks entries.

For (3) above you can see the results in this JSFiddle

Writelines writes lines without newline, Just fills the file

As others have mentioned, and counter to what the method name would imply, writelines does not add line separators. This is a textbook case for a generator. Here is a contrived example:

def item_generator(things):
    for item in things:
        yield item
        yield '\n'

def write_things_to_file(things):
    with open('path_to_file.txt', 'wb') as f:

Benefits: adds newlines explicitly without modifying the input or output values or doing any messy string concatenation. And, critically, does not create any new data structures in memory. IO (writing to a file) is when that kind of thing tends to actually matter. Hope this helps someone!

Setting Elastic search limit to "unlimited"

use the scan method e.g.

 curl -XGET 'localhost:9200/_search?search_type=scan&scroll=10m&size=50' -d '
    "query" : {
       "match_all" : {}

see here

surface plots in matplotlib

In Matlab I did something similar using the delaunay function on the x, y coords only (not the z), then plotting with trimesh or trisurf, using z as the height.

SciPy has the Delaunay class, which is based on the same underlying QHull library that the Matlab's delaunay function is, so you should get identical results.

From there, it should be a few lines of code to convert this Plotting 3D Polygons in python-matplotlib example into what you wish to achieve, as Delaunay gives you the specification of each triangular polygon.

Failed to load resource: the server responded with a status of 500 (Internal Server Error) in Bind function

The 500 code would normally indicate an error on the server, not anything with your code. Some thoughts

  • Talk to the server developer for more info. You can't get more info directly.
  • Verify your arguments into the call (values). Look for anything you might think could cause a problem for the server process. The process should not die and should return you a better code, but bugs happen there also.
  • Could be intermittent, like if the server database goes down. May be worth trying at another time.

CSS z-index not working (position absolute)

try this code:

.absolute {
    position: absolute;
    top: 0; left: 0;
    width: 200px;
    height: 50px;
    background: yellow;


Creating a JSON dynamically with each input value using jquery

May be this will help, I'd prefer pure JS wherever possible, it improves the performance drastically as you won't have lots of JQuery function calls.

var obj = [];
var elems = $("input[class=email]");

for (i = 0; i < elems.length; i += 1) {
    var id = this.getAttribute('title');
    var email = this.value;
    tmp = {
        'title': id,
        'email': email


How to get child element by ID in JavaScript?

Here is a pure JavaScript solution (without jQuery)

var _Utils = function ()
    this.findChildById = function (element, childID, isSearchInnerDescendant) // isSearchInnerDescendant <= true for search in inner childern 
        var retElement = null;
        var lstChildren = isSearchInnerDescendant ? Utils.getAllDescendant(element) : element.childNodes;

        for (var i = 0; i < lstChildren.length; i++)
            if (lstChildren[i].id == childID)
                retElement = lstChildren[i];

        return retElement;

    this.getAllDescendant = function (element, lstChildrenNodes)
        lstChildrenNodes = lstChildrenNodes ? lstChildrenNodes : [];

        var lstChildren = element.childNodes;

        for (var i = 0; i < lstChildren.length; i++) 
            if (lstChildren[i].nodeType == 1) // 1 is 'ELEMENT_NODE'
                lstChildrenNodes = Utils.getAllDescendant(lstChildren[i], lstChildrenNodes);

        return lstChildrenNodes;
var Utils = new _Utils;

Example of use:

var myDiv = document.createElement("div");
myDiv.innerHTML = "<table id='tableToolbar'>" +
                        "<tr>" +
                            "<td>" +
                                "<div id='divIdToSearch'>" +
                                "</div>" +
                            "</td>" +
                        "</tr>" +

var divToSearch = Utils.findChildById(myDiv, "divIdToSearch", true);

Invoke-WebRequest, POST with parameters

For some picky web services, the request needs to have the content type set to JSON and the body to be a JSON string. For example:

Invoke-WebRequest -UseBasicParsing -ContentType "application/json" -Method POST -Body "{ 'ItemID':3661515, 'Name':'test'}"

or the equivalent for XML, etc.

What is the first character in the sort order used by Windows Explorer?

I know there is already an answer - and this is an old question - but I was wondering the same thing and after finding this answer I did a little experimentation on my own and had (IMO) a worthwhile addition to the discussion.

The non-visible characters can still be used in a folder name - a placeholder is inserted - but the sort on ASCII value still seems to hold.

I tested on Windows7, holding down the alt-key and typing in the ASCII code using the numeric keypad. I did not test very many, but was successful creating foldernames that started with ASCII 1, ASCII 2, and ASCII 3. Those correspond with SOH, STX and ETX. Respectively it displayed happy face, filled happy face, and filled heart.

I'm not sure if I can duplicate that here - but I will type them in on the next lines and submit.




How to redirect user's browser URL to a different page in Nodejs?

For those who (unlike OP) are using the express lib:


WHERE Clause to find all records in a specific month

If you're using SQL Server, look into DATEPART.


You can then use normal integer logic with it. Same for year, just use yy instead of mm.

how can I connect to a remote mongo server from Mac OS terminal

With Mongo 3.2 and higher just use your connection string as is:

mongo mongodb://username:[email protected]:10011/my_database

How do I print bytes as hexadecimal?

This is a modified version of the Nibble to Hex method

void hexArrayToStr(unsigned char* info, unsigned int infoLength, char **buffer) {
    const char* pszNibbleToHex = {"0123456789ABCDEF"};
    int nNibble, i;
    if (infoLength > 0) {
        if (info != NULL) {
            *buffer = (char *) malloc((infoLength * 2) + 1);
            buffer[0][(infoLength * 2)] = 0;
            for (i = 0; i < infoLength; i++) {
                nNibble = info[i] >> 4;
                buffer[0][2 * i] = pszNibbleToHex[nNibble];
                nNibble = info[i] & 0x0F;
                buffer[0][2 * i + 1] = pszNibbleToHex[nNibble];
        } else {
            *buffer = NULL;
    } else {
        *buffer = NULL;

C++ getters/setters coding style

As an aside, in C++, it is somewhat odd to have a const reference member. You have to assign it in the constructor list. Who owns the actually memory of that object and what is it's lifetime?

As for style, I agree with the others that you don't want to expose your privates. :-) I like this pattern for setters/getters

class Foo
  const string& FirstName() const;
  Foo& FirstName(const string& newFirstName);

  const string& LastName() const;
  Foo& LastName(const string& newLastName);

  const string& Title() const;
  Foo& Title(const string& newTitle);

This way you can do something like:

Foo f;

Disable webkit's spin buttons on input type="number"?

It seems impossible to prevent spinners from appearing in Opera. As a temporary workaround, you can make room for the spinners. As far as I can tell, the following CSS adds just enough padding, only in Opera:

input[type=number] {
    padding-right: 1.2em;

Eloquent Collection: Counting and Detect Empty

You can do

$result = Model::where(...)->count(); 

to count the results.

You can also use

if ($result->isEmpty()){}

to check whether or not the result is empty.

Unable to resolve dependency for ':app@debug/compileClasspath': Could not resolve

If you have ever used a proxy, VPN, etc(or may not, I am not sure).....Then the solution below may help you...I don't know why (and if anybody can tell me why, I will appreciate that), but it works, pefectly. Have a try when you totally feel desperate about that issue.

Come to your project, and open or, comment out these codes about proxy:


enter image description here

Then, it might work.

PS: I met this problem when I try to use dataBinding library, and when I added the code

buildFeatures {
        dataBinding true

into gradle as the guide told me and Syns the project, I got such an error:"Unable to resolve dependency for ':app@debug/compileClasspath': Could not resolve ......". Finally I did what I described above, and I successed. What I experience may give you a hint, so I post the solution here and hope it might help.

Sync data between Android App and webserver

If you write this yourself these are some of the points to keep in mind

Proper authentication between the device and the Sync Server

A sync protocol between the device and the server. It will usually go in 3 phases, authentication, data exchange, status exchange (which operations worked and which failed)

Pick your payload format. I suggest SyncML based XML mixed with JSON based format to represent the actual data. So SyncML for the protocol, and JSON for the actual data being exchanged. Using JSON Array while manipulating the data is always preferred as it is easy to access data using JSON Array.

Keeping track of data changes on both client and server. You can maintain a changelog of ids that change and pick them up during a sync session. Also, clear the changelog as the objects are successfully synchronized. You can also use a boolean variable to confirm the synchronization status, i.e. last time of sync. It will be helpful for end users to identify the time when last sync is done.

Need to have a way to communicate from the server to the device to start a sync session as data changes on the server. You can use C2DM or write your own persistent tcp based communication. The tcp approach is a lot seamless

A way to replicate data changes across multiple devices

And last but not the least, a way to detect and handle conflicts

Hope this helps as a good starting point.

JavaScript Form Submit - Confirm or Cancel Submission Dialog Box

A simple inline JavaScript confirm would suffice:

<form onsubmit="return confirm('Do you really want to submit the form?');">

No need for an external function unless you are doing validation, which you can do something like this:

function validate(form) {

    // validation code here ...

    if(!valid) {
        alert('Please correct the errors in the form!');
        return false;
    else {
        return confirm('Do you really want to submit the form?');
<form onsubmit="return validate(this);">

Clone an image in cv2 python

My favorite method uses cv2.copyMakeBorder with no border, like so.

copy = cv2.copyMakeBorder(original,0,0,0,0,cv2.BORDER_REPLICATE)

std::enable_if to conditionally compile a member function

Here is my minimalist example, using a macro. Use double brackets enable_if((...)) when using more complex expressions.

template<bool b, std::enable_if_t<b, int> = 0>
using helper_enable_if = int;

#define enable_if(value) typename = helper_enable_if<value>

struct Test
     void run();

How to get phpmyadmin username and password

 Step 1:

    Locate phpMyAdmin installation path.

    Step 2:

    Open phpMyAdmin> in your favourite text editor.

    Step 3:

    $cfg['Servers'][$i]['auth_type'] = 'config';
    $cfg['Servers'][$i]['user'] = 'root';
    $cfg['Servers'][$i]['password'] = '';
    $cfg['Servers'][$i]['extension'] = 'mysqli';
    $cfg['Servers'][$i]['AllowNoPassword'] = true;
    $cfg['Lang'] = '';

How to properly use unit-testing's assertRaises() with NoneType objects?

The usual way to use assertRaises is to call a function:

self.assertRaises(TypeError, test_function, args)

to test that the function call test_function(args) raises a TypeError.

The problem with self.testListNone[:1] is that Python evaluates the expression immediately, before the assertRaises method is called. The whole reason why test_function and args is passed as separate arguments to self.assertRaises is to allow assertRaises to call test_function(args) from within a try...except block, allowing assertRaises to catch the exception.

Since you've defined self.testListNone = None, and you need a function to call, you might use operator.itemgetter like this:

import operator
self.assertRaises(TypeError, operator.itemgetter, (self.testListNone,slice(None,1)))



is a long-winded way of saying self.testListNone[:1], but which separates the function (operator.itemgetter) from the arguments.

How to Apply Corner Radius to LinearLayout

You would use a Shape Drawable as the layout's background and set its cornerRadius. Check this blog for a detailed tutorial

wordpress contactform7 textarea cols and rows change in smaller screens

I was able to get this work. I added the following to my custom CSS:

.wpcf7-form textarea{ 
    width: 100% !important;

Single Page Application: advantages and disadvantages

Try not to consider using a SPA without first defining how you will address security and API stability on the server side. Then you will see some of the true advantages to using a SPA. Specifically, if you use a RESTful server that implements OAUTH 2.0 for security, you will achieve two fundamental separation of concerns that can lower your development and maintenance costs.

  1. This will move the session (and it's security) onto the SPA and relieve your server from all of that overhead.
  2. Your API's become both stable and easily extensible.

Hinted to earlier, but not made explicit; If your goal is to deploy Android & Apple applications, writing a JavaScript SPA that is wrapped by a native call to host the screen in a browser (Android or Apple) eliminates the need to maintain both an Apple code base and an Android code base.

Text File Parsing with Python

From the accepted answer, it looks like your desired behaviour is to turn

skip 0
skip 1
skip 2
skip 3
"2012-06-23 03:09:13.23",4323584,-1.911224,-0.4657288,-0.1166382,-0.24823,0.256485,"NAN",-0.3489428,-0.130449,-0.2440527,-0.2942413,0.04944348,0.4337797,-1.105218,-1.201882,-0.5962594,-0.586636



If that's right, then I think something like

import csv

with open("test.dat", "rb") as infile, open("test.csv", "wb") as outfile:
    reader = csv.reader(infile)
    writer = csv.writer(outfile, quoting=False)
    for i, line in enumerate(reader):
        if i < 4: continue
        date = line[0].split()
        day = date[0].split('-')
        time = date[1].split(':')
        newline = day + time + line[1:]

would be a little simpler than the reps stuff.

How to view the dependency tree of a given npm module?

There is also a nice web app to see the dependencies in a weighted map kind of view.

For example:[email protected]

Error sending json in POST to web API service

  1. You have to must add header property Content-Type:application/json
  2. When you define any POST request method input parameter that should be annotated as [FromBody], e.g.:

    public HttpResponseMessage Post([FromBody]ActivityResult ar)
      return new HttpResponseMessage(HttpStatusCode.OK);
  3. Any JSON input data must be raw data.

How to include Authorization header in cURL POST HTTP Request in PHP?

You have most of the code…

CURLOPT_HTTPHEADER for curl_setopt() takes an array with each header as an element. You have one element with multiple headers.

You also need to add the Authorization header to your $header array.

$header = array();
$header[] = 'Content-length: 0';
$header[] = 'Content-type: application/json';
$header[] = 'Authorization: OAuth SomeHugeOAuthaccess_tokenThatIReceivedAsAString';

Why is my asynchronous function returning Promise { <pending> } instead of a value?

I had the same issue earlier, but my situation was a bit different in the front-end. I'll share my scenario anyway, maybe someone might find it useful.

I had an api call to /api/user/register in the frontend with email, password and username as request body. On submitting the form(register form), a handler function is called which initiates the fetch call to /api/user/register. I used the event.preventDefault() in the beginning line of this handler function, all other lines,like forming the request body as well the fetch call was written after the event.preventDefault(). This returned a pending promise.

But when I put the request body formation code above the event.preventDefault(), it returned the real promise. Like this:

    const data = {
        'email': email,
        'password': password

instead of :

     const data = {
            'email': email,
            'password': password

How to change the URL from "localhost" to something else, on a local system using wampserver?

for new version of Wamp

<VirtualHost *:80>
  ServerName domain.local
  DocumentRoot C:/wamp/www/domain/
  <Directory "C:/wamp/www/domain/">
      Options +Indexes +FollowSymLinks +MultiViews
      AllowOverride All
      Require local

How to get span tag inside a div in jQuery and assign a text?

function Errormessage(txt) {
    $("#message span:first").text(txt);
    // find the span inside the div and assign a text
    $("#message a.close-notify").click(function() {

Best way to incorporate Volley (or other library) into Android Studio project


compile ''

OLD ANSWER: You need the next in your build.gradle of your app module:

dependencies {
        compile 'com.mcxiaoke.volley:library:1.0.19'
        (Rest of your dependencies)


This is not the official repo but is a highly trusted one.