Programs & Examples On #Pageasynctask

Ways to eliminate switch in code

In a procedural language, like C, then switch will be better than any of the alternatives.

In an object-oriented language, then there are almost always other alternatives available that better utilise the object structure, particularly polymorphism.

The problem with switch statements arises when several very similar switch blocks occur at multiple places in the application, and support for a new value needs to be added. It is pretty common for a developer to forget to add support for the new value to one of the switch blocks scattered around the application.

With polymorphism, then a new class replaces the new value, and the new behaviour is added as part of adding the new class. Behaviour at these switch points is then either inherited from the superclass, overridden to provide new behaviour, or implemented to avoid a compiler error when the super method is abstract.

Where there is no obvious polymorphism going on, it can be well worth implementing the Strategy pattern.

But if your alternative is a big IF ... THEN ... ELSE block, then forget it.

What is an opaque response, and what purpose does it serve?

javascript is a bit tricky getting the answer, I fixed it by getting the api from the backend and then calling it to the frontend.

public function get_typechange () {

    $ url = "https://........";
    $ json = file_get_contents ($url);
    $ data = json_decode ($ json, true);
    $ resp = json_encode ($data);
    $ error = json_last_error_msg ();
    return $ resp;


How to Convert double to int in C?

int b;
double a;

this code gives the output as b=3669 only you check it clearly.

How to iterate over associative arrays in Bash

Use this higher order function to prevent the pyramid of doom

  arr="$(declare -p $1)" ; eval "declare -A f="${arr#*=}; 
  for i in ${!f[@]}; do $2 "$i" "${f[$i]}"; done


$ bar(){ echo "$1 -> $2"; }
$ declare -A foo["flap"]="three four" foo["flop"]="one two"
$ foreach foo bar
flap -> three four
flop -> one two

Get custom product attributes in Woocommerce

Use below code to get all attributes with details

    global $wpdb;

    $attribute_taxonomies = $wpdb->get_results( "SELECT * FROM " . $wpdb->prefix . "woocommerce_attribute_taxonomies WHERE attribute_name != '' ORDER BY attribute_name ASC;" );
    set_transient( 'wc_attribute_taxonomies', $attribute_taxonomies );

    $attribute_taxonomies = array_filter( $attribute_taxonomies  ) ;


Best way to select random rows PostgreSQL

select * from table order by random() limit 1000;

If you know how many rows you want, check out tsm_system_rows.


module provides the table sampling method SYSTEM_ROWS, which can be used in the TABLESAMPLE clause of a SELECT command.

This table sampling method accepts a single integer argument that is the maximum number of rows to read. The resulting sample will always contain exactly that many rows, unless the table does not contain enough rows, in which case the whole table is selected. Like the built-in SYSTEM sampling method, SYSTEM_ROWS performs block-level sampling, so that the sample is not completely random but may be subject to clustering effects, especially if only a small number of rows are requested.

First install the extension

CREATE EXTENSION tsm_system_rows;

Then your query,

FROM table

Specifying onClick event type with Typescript and React.Konva

As posted in my update above, a potential solution would be to use Declaration Merging as suggested by @Tyler-sebastion. I was able to define two additional interfaces and add the index property on the EventTarget in this way.

interface KonvaTextEventTarget extends EventTarget {
  index: number

interface KonvaMouseEvent extends React.MouseEvent<HTMLElement> {
  target: KonvaTextEventTarget

I then can declare the event as KonvaMouseEvent in my onclick MouseEventHandler function.

onClick={(event: KonvaMouseEvent) => {

I'm still not 100% if this is the best approach as it feels a bit Kludgy and overly verbose just to get past the tslint error.

PostgreSQL database service

  1. check conenctionstring
  2. check SSL
  3. check firewall
  4. if u use VS studio, check for db driver

How to merge specific files from Git branches

The simplest solution is:

git checkout the name of the source branch and the paths to the specific files that we want to add to our current branch

git checkout sourceBranchName pathToFile

How to validate a date?

Though this was raised long ago, still a most wanted validation. I found an interesting blog with few function.

/* Please use these function to check the reuslt only. do not check for otherewise. other than utiljs_isInvalidDate


utiljs_isFutureDate() retuns only true for future dates. false does not mean it is not future date. it may be an invalid date.

practice :

call utiljs_isInvalidDate first and then use the returned date for utiljs_isFutureDate()

var d = {};

if(!utiljs_isInvalidDate('32/02/2012', d))


//date is a future date


// date is not a future date


function utiljs_isInvalidDate(dateStr, returnDate) {

    /*dateStr | format should be dd/mm/yyyy, Ex:- 31/10/2017

     *returnDate will be in {date:js date object}.

     *Ex:- if you only need to check whether the date is invalid,

     * utiljs_isInvalidDate('03/03/2017')

     *Ex:- if need the date, if the date is valid,

     * var dt = {};

     * if(!utiljs_isInvalidDate('03/03/2017', dt)){

     *  //you can use

     * }


    if (!dateStr)
        return true;
    if (!dateStr.substring || !dateStr.length || dateStr.length != 10)
        return true;
    var day = parseInt(dateStr.substring(0, 2), 10);
    var month = parseInt(dateStr.substring(3, 5), 10);
    var year = parseInt(dateStr.substring(6), 10);
    var fullString = dateStr.substring(0, 2) + dateStr.substring(3, 5) + dateStr.substring(6);
    if (null == fullString.match(/^\d+$/)) //to check for whether there are only numbers
        return true;
    var dt = new Date(month + "/" + day + "/" + year);
    if (dt == 'Invalid Date' || isNaN(dt)) { //if the date string is not valid, new Date will create this string instead
        return true;
    if (dt.getFullYear() != year || dt.getMonth() + 1 != month || dt.getDate() != day) //to avoid 31/02/2018 like dates
        return true;
    if (returnDate) = dt;
    return false;

function utiljs_isFutureDate(dateStrOrObject, returnDate) {
    return utiljs_isFuturePast(dateStrOrObject, returnDate, true);

function utiljs_isPastDate(dateStrOrObject, returnDate) {
    return utiljs_isFuturePast(dateStrOrObject, returnDate, false);

function utiljs_isValidDateObjectOrDateString(dateStrOrObject, returnDate) { //this is an internal function
    var dt = {};
    if (!dateStrOrObject)
        return false;
    if (typeof dateStrOrObject.getMonth === 'function') = new Date(dateStrOrObject); //to avoid modifying original date
    else if (utiljs_isInvalidDate(dateStrOrObject, dt))
        return false;
    if (returnDate) =;
    return true;


function utiljs_isFuturePast(dateStrOrObject, returnDate, isFuture) { //this is an internal function, please use isFutureDate or isPastDate function
    if (!dateStrOrObject)
        return false;
    var dt = {};
    if (!utiljs_isValidDateObjectOrDateString(dateStrOrObject, dt))
        return false;
    today = new Date();
    today.setHours(0, 0, 0, 0);
    if (, 0, 0, 0);
    if (returnDate) =;
    //creating new date using only current d/m/y. as is created with string. otherwise same day selection will not be validated.
    if (isFuture && && && > today.getTime()) {
        return true;
    if (!isFuture && && && < today.getTime()) {
        return true;
    return false;

function utiljs_isLeapYear(dateStrOrObject, returnDate) {
    var dt = {};
    if (!dateStrOrObject)
        return false;
    if (utiljs_isValidDateObjectOrDateString(dateStrOrObject, dt)) {
        if (returnDate)
        return % 4 == 0;
    return false;

function utiljs_firstDateLaterThanSecond(firstDate, secondDate, returnFirstDate, returnSecondDate) {
    if (!firstDate || !secondDate)
        return false;
    var dt1 = {},
    dt2 = {};
    if (!utiljs_isValidDateObjectOrDateString(firstDate, dt1) || !utiljs_isValidDateObjectOrDateString(secondDate, dt2))
        return false;
    if (returnFirstDate) =;
    if (returnSecondDate) =;, 0, 0, 0);, 0, 0, 0);
    if ( && && >
        return true;
    return false;

function utiljs_isEqual(firstDate, secondDate, returnFirstDate, returnSecondDate) {
    if (!firstDate || !secondDate)
        return false;
    var dt1 = {},
    dt2 = {};
    if (!utiljs_isValidDateObjectOrDateString(firstDate, dt1) || !utiljs_isValidDateObjectOrDateString(secondDate, dt2))
        return false;
    if (returnFirstDate) =;
    if (returnSecondDate) =;, 0, 0, 0);, 0, 0, 0);
    if ( && && ==
        return true;
    return false;

function utiljs_firstDateEarlierThanSecond(firstDate, secondDate, returnFirstDate, returnSecondDate) {
    if (!firstDate || !secondDate)
        return false;
    var dt1 = {},
    dt2 = {};
    if (!utiljs_isValidDateObjectOrDateString(firstDate, dt1) || !utiljs_isValidDateObjectOrDateString(secondDate, dt2))
        return false;
    if (returnFirstDate) =;
    if (returnSecondDate) =;, 0, 0, 0);, 0, 0, 0);
    if ( && && <
        return true;
    return false;

copy the whole code into a file and include.

hope this helps.

jQuery 'each' loop with JSON array

Brief code but full-featured

The following is a hybrid jQuery solution that formats each data "record" into an HTML element and uses the data's properties as HTML attribute values.

The jquery each runs the inner loop; I needed the regular JavaScript for on the outer loop to be able to grab the property name (instead of value) for display as the heading. According to taste it can be modified for slightly different behaviour.

This is only 5 main lines of code but wrapped onto multiple lines for display:

$.get("data.php", function(data){

    for (var propTitle in data) {


            $(data[propTitle]).each(function(iRec, oRec) {

                    .attr('id', 'T'+oRec.textId)


Produces the output

(Note: I modified the JSON data text values by prepending a number to ensure I was displaying the proper records in the proper sequence - while "debugging")

<div class="heading">
<div id="T123" class="Greeting">
<div id="T514" class="Question">
    1What's up?
<div id="T122" class="Order">
    1Come over here
<div class="heading">
<div id="T1255" class="Greeting">
<div id="T6564" class="Question">
    2What's up?
<div id="T0192" class="Order">
    2Come over here
<div class="heading">
<div id="T5213" class="Greeting">
<div id="T9758" class="Question">
    3What's up?
<div id="T7655" class="Order">
    3Come over here
<div id="contentHere"></div>

Apply a style sheet

.heading { font-size: 24px; text-decoration:underline }
.Greeting { color: green; }
.Question { color: blue; }
.Order { color: red; }

to get a "beautiful" looking set of data

alt text

More Info
The JSON data was used in the following way:

for each category (key name the array is held under):

  • the key name is used as the section heading (e.g. justIn)

for each object held inside an array:

  • 'text' becomes the content of a div
  • 'textType' becomes the class of the div (hooked into a style sheet)
  • 'textId' becomes the id of the div
  • e.g. <div id="T122" class="Order">Come over here</div>

Mercurial stuck "waiting for lock"

I do not expect this to be a winning answer, but it is a fairly unusual situation. Mentioning in case someone other than me runs into it.

Today I got the "waiting for lock on repository" on an hg push command.

When I killed the hung hg command I could see no .hg/store/lock

When I looked for .hg/store/lock while the command was hung, it existed. But the lockfile was deleted when the hg command was killed.

When I went to the target of the push, and executed hg pull, no problem.

Eventually I realized that the process ID on the hg push was lock waiting message was changing each time. It turns out that the "hg push" was hanging waiting for a lock held by itself (or possibly a subprocess, I did not investigate further).

It turns out that the two workspaces, let's call them A and B, had .hg trees shared by symlink:

A/.hg --symlinked-to--> B/.hg

This is NOT a good thing to do with Mercurial. Mercurial does not understand the concept of two workspaces sharing the same repository. I do understand, however, how somebody coming to Mercurial from another VCS might want this (Perforce does, although not a DVCS; the Bazaar DVCS reportedly can do so). I am surprised that a symlinked REP-ROOT/.hg works at all, although it seems to except for this push.

How to get the path of the batch script in Windows?

I am working on a Windows 7 machine and I have ended up using the lines below to get the absolute folder path for my bash script.

I got to this solution after looking at

#Get the full aboslute filename.
#Remove everything after \. An extra \ seems to be necessary to escape something...
echo $filename
echo $folder

How to capitalize the first character of each word in a string

There are many way to convert the first letter of the first word being capitalized. I have an idea. It's very simple:

public String capitalize(String str){

     /* The first thing we do is remove whitespace from string */
     String c = str.replaceAll("\\s+", " ");
     String s = c.trim();
     String l = "";

     for(int i = 0; i < s.length(); i++){
          if(i == 0){                              /* Uppercase the first letter in strings */
              l += s.toUpperCase().charAt(i);
              i++;                                 /* To i = i + 1 because we don't need to add               
                                                    value i = 0 into string l */

          l += s.charAt(i);

          if(s.charAt(i) == 32){                   /* If we meet whitespace (32 in ASCII Code is whitespace) */
              l += s.toUpperCase().charAt(i+1);    /* Uppercase the letter after whitespace */
              i++;                                 /* Yo i = i + 1 because we don't need to add
                                                   value whitespace into string l */
     return l;

In-memory size of a Python structure

These answers all collect shallow size information. I suspect that visitors to this question will end up here looking to answer the question, "How big is this complex object in memory?"

There's a great answer here:

The punchline:

import sys

def get_size(obj, seen=None):
    """Recursively finds size of objects"""
    size = sys.getsizeof(obj)
    if seen is None:
        seen = set()
    obj_id = id(obj)
    if obj_id in seen:
        return 0
    # Important mark as seen *before* entering recursion to gracefully handle
    # self-referential objects
    if isinstance(obj, dict):
        size += sum([get_size(v, seen) for v in obj.values()])
        size += sum([get_size(k, seen) for k in obj.keys()])
    elif hasattr(obj, '__dict__'):
        size += get_size(obj.__dict__, seen)
    elif hasattr(obj, '__iter__') and not isinstance(obj, (str, bytes, bytearray)):
        size += sum([get_size(i, seen) for i in obj])
    return size

Used like so:

In [1]: get_size(1)
Out[1]: 24

In [2]: get_size([1])
Out[2]: 104

In [3]: get_size([[1]])
Out[3]: 184

If you want to know Python's memory model more deeply, there's a great article here that has a similar "total size" snippet of code as part of a longer explanation:

Split comma separated column data into additional columns

split_part() does what you want in one step:

SELECT split_part(col, ',', 1) AS col1
     , split_part(col, ',', 2) AS col2
     , split_part(col, ',', 3) AS col3
     , split_part(col, ',', 4) AS col4
FROM   tbl;

Add as many lines as you have items in col (the possible maximum). Columns exceeding data items will be empty strings ('').

How to change fonts in matplotlib (python)?

I prefer to employ:

from matplotlib import rc
rc('text', usetex=True)

How can I test that a variable is more than eight characters in PowerShell?

You can also use -match against a Regular expression. Ex:

if ($dbUserName -match ".{8}" )
    Write-Output " Please enter more than 8 characters "
    $dbUserName=read-host " Re-enter database user name"

Also if you're like me and like your curly braces to be in the same horizontal position for your code blocks, you can put that on a new line, since it's expecting a code block it will look on next line. In some commands where the first curly brace has to be in-line with your command, you can use a grave accent marker (`) to tell powershell to treat the next line as a continuation.

How to set username and password for SmtpClient object in .NET?

Use NetworkCredential

Yep, just add these two lines to your code.

var credentials = new System.Net.NetworkCredential("username", "password");

client.Credentials = credentials;

How can I delete Docker's images?

To delete some Docker image you must execute the following command:

$ docker rmi <docker_image_id>

So, to delete all Docker images you can execute the following command:

$ docker rmi $(docker images -q)

Now, if you want delete all Docker images (including images that are in use), you can add the flag -f, for example:

$ docker rmi -f $(docker images -q)

Sum of values in an array using jQuery

You can use reduce which works in all browser except IE8 and lower.

["20","40","80","400"].reduce(function(a, b) {
    return parseInt(a, 10) + parseInt(b, 10);

link_to method and click event in Rails

You can use link_to_function (removed in Rails 4.1):

link_to_function 'My link with obtrusive JavaScript', 'alert("Oh no!")'

Or, if you absolutely need to use link_to:

link_to 'Another link with obtrusive JavaScript', '#',
        :onclick => 'alert("Please no!")'

However, putting JavaScript right into your generated HTML is obtrusive, and is bad practice.

Instead, your Rails code should simply be something like this:

link_to 'Link with unobtrusive JavaScript',
        :id => 'my-link'

And assuming you're using the Prototype JS framework, JS like this in your application.js:

$('my-link').observe('click', function (event) {
  event.stop(); // Prevent link from following through to its given href

Or if you're using jQuery:

$('#my-link').click(function (event) {
  event.preventDefault(); // Prevent link from following its href

By using this third technique, you guarantee that the link will follow through to some other page—not just fail silently—if JavaScript is unavailable for the user. Remember, JS could be unavailable because the user has a poor internet connection (e.g., mobile device, public wifi), the user or user's sysadmin disabled it, or an unexpected JS error occurred (i.e., developer error).

Getting checkbox values on submit

(It's not action="get" or action="post" it's method="get" or method="post"

Try to do it using post method:

<form action="third.php" method="POST">
    Red<input type="checkbox" name="color[]" id="color" value="red">
    Green<input type="checkbox" name="color[]" id="color" value="green">
    Blue<input type="checkbox" name="color[]" id="color" value="blue">
    Cyan<input type="checkbox" name="color[]" id="color" value="cyan">
    Magenta<input type="checkbox" name="color[]" id="color" value="Magenta">
    Yellow<input type="checkbox" name="color[]" id="color" value="yellow">
    Black<input type="checkbox" name="color[]" id="color" value="black">
    <input type="submit" value="submit">

and in third.php

or for a pericular field you colud get value in:

$_POST['color'][0] //for RED
$_POST['color'][1] // for GREEN

How do I find the authoritative name-server for a domain name?

You can use the whois service. On a UNIX like operating system you would execute the following command. Alternatively you can do it on the web at


You would get the following response.

...text removed here...

Domain servers in listed order: NS51.DOMAINCONTROL.COM NS52.DOMAINCONTROL.COM

You can use nslookup or dig to find out more information about records for a given domain. This might help you resolve the conflicts you have described.

:before and background-image... should it work?

For some reason, I need float property of a pseudo-element to be set to left or right for the image to appear. height and width of the pseudo-element should be both set but not in percentage. I'm on Firefox 67.

Moment JS start and end of given month

const year = 2014;_x000D_
const month = 09;_x000D_
// months start at index 0 in momentjs, so we subtract 1_x000D_
const startDate = moment([year, month - 1, 01]).format("YYYY-MM-DD");_x000D_
// get the number of days for this month_x000D_
const daysInMonth = moment(startDate).daysInMonth();_x000D_
// we are adding the days in this month to the start date (minus the first day)_x000D_
const endDate = moment(startDate).add(daysInMonth - 1, 'days').format("YYYY-MM-DD");_x000D_
console.log(`start date: ${startDate}`);_x000D_
console.log(`end date:   ${endDate}`);

How to do a GitHub pull request

To learn how to make a pull request I just followed two separate help pages on Github (linked below as bullet points). The following command line commands are for Part 1. Part 2, the actual pull request, is done entirely on Github's website.

$ git clone
$ cd dwolla-php
$ git remote add upstream
$ git fetch upstream
// make your changes to this newly cloned, local repo 
$ git add .
$ git commit -m '1st commit to dwolla'
$ git push origin master
  • Part 1: fork someone's repo:

    1. click the 'fork' button on the repo you want to contribute to, in this case: Dwolla's PHP repo (Dwolla/dwolla-php)
    2. get the URL for your newly created fork, in this case: (tim-peterson/dwolla-php)
    3. type the git clone->cd dwolla-php->git remote->git fetch sequence above to clone your fork somewhere in your computer (i.e., "copy/paste" it to, in this case: third_party TimPeterson$) and sync it with the master repo (Dwolla/dwolla-php)
    4. make your changes to your local repo
    5. type the git add->git commit->git push sequence above to push your changes to the remote repo, i.e., your fork on Github (tim-peterson/dwolla-php)
  • Part 2: make pull-request:

    1. go to your fork's webpage on Github (
    2. click 'pull-request' button
    3. give pull-request a name, fill in details of what changes you made, click submit button.
    4. you're done!!

Can I access a form in the controller?

This answer is a little late, but I stumbled upon a solution that makes everything a LOT easier.

You can actually assign the form name directly to your controller if you're using the controllerAs syntax and then reference it from your "this" variable. Here's how I did it in my code:

I configured the controller via ui-router (but you can do it however you want, even in the HTML directly with something like <div ng-controller="someController as myCtrl">) This is what it might look like in a ui-router configuration:

views: {
            "": {
                templateUrl: "someTemplate.html",
                controller: "someController",
                controllerAs: "myCtrl"

and then in the HTML, you just set the form name as the "controllerAs"."name" like so:

<ng-form name="myCtrl.someForm">
    <!-- example form code here -->
    <input name="firstName" ng-model="myCtrl.user.firstName" required>

now inside your controller you can very simply do this:

        function ($scope) {
            var vm = this;
              // do something

Disable cross domain web security in Firefox

For anyone finding this question while using Nightwatch.js (1.3.4), there's an acceptInsecureCerts: true setting in the config file:

firefox: {_x000D_
      desiredCapabilities: {_x000D_
        browserName: 'firefox',_x000D_
        alwaysMatch: {_x000D_
          // Enable this if you encounter unexpected SSL certificate errors in Firefox_x000D_
          acceptInsecureCerts: true,_x000D_
          'moz:firefoxOptions': {_x000D_
            args: [_x000D_
              // '-headless',_x000D_
              // '-verbose'_x000D_

How to reset selected file with input tag file type in Angular 2?

you may use template reference variable and send to a method


<input #variable type="file" placeholder="File Name" name="filename" (change)="onChange($event, variable);">


onChange(event: any, element): void {
    // codes
    element.value = '';

Accessing a matrix element in the "Mat" object (not the CvMat object) in OpenCV C++

The ideas provided above are good. For fast access (in case you would like to make a real time application) you could try the following:

//suppose you read an image from a file that is gray scale
Mat image = imread("Your path", CV_8UC1);
// some processing
uint8_t *myData =;
int width = image.cols;
int height = image.rows;
int _stride = image.step;//in case cols != strides
for(int i = 0; i < height; i++)
    for(int j = 0; j < width; j++)
        uint8_t val = myData[ i * _stride + j];
        //do whatever you want with your value

Pointer access is much faster than the<> accessing. Hope it helps!

Word wrapping in phpstorm

  • File | Settings | Editor --> Use soft wraps in editor : to turn them on for all files by default.

  • File | Settings | Code Style | General --> Wrap when typing reaches right margin

    .. but that's different (it will make new line).

PHP: trying to create a new line with "\n"

Assuming you're viewing the output in a web browser you have at least two options:

  1. Surround your text block with <pre> statements

  2. Change your \n to an HTML <br> tag (<br/> will also do)

Writing an input integer into a cell

When asking a user for a response to put into a cell using the InputBox method, there are usually three things that can happen¹.

  1. The user types something in and clicks OK. This is what you expect to happen and you will receive input back that can be returned directly to a cell or a declared variable.
  2. The user clicks Cancel, presses Esc or clicks × (Close). The return value is a boolean False. This should be accounted for.
  3. The user does not type anything in but clicks OK regardless. The return value is a zero-length string.

If you are putting the return value into a cell, your own logic stream will dictate what you want to do about the latter two scenarios. You may want to clear the cell or you may want to leave the cell contents alone. Here is how to handle the various outcomes with a variant type variable and a Select Case statement.

    Dim returnVal As Variant

    returnVal = InputBox(Prompt:="Type a value:", Title:="Test Data")

    'if the user clicked Cancel, Close or Esc the False
    'is translated to the variant as a vbNullString
    Select Case True
        Case Len(returnVal) = 0
            'no value but user clicked OK - clear the target cell
        Case Else
            'returned a value with OK, save it
            Range("A2") = returnVal
    End Select

¹ There is a fourth scenario when a specific type of InputBox method is used. An InputBox can return a formula, cell range error or array. Those are special cases and requires using very specific syntax options. See the supplied link for more.

Java 8 stream's .min() and .max(): why does this compile?

Let me explain what is happening here, because it isn't obvious!

First, Stream.max() accepts an instance of Comparator so that items in the stream can be compared against each other to find the minimum or maximum, in some optimal order that you don't need to worry too much about.

So the question is, of course, why is Integer::max accepted? After all it's not a comparator!

The answer is in the way that the new lambda functionality works in Java 8. It relies on a concept which is informally known as "single abstract method" interfaces, or "SAM" interfaces. The idea is that any interface with one abstract method can be automatically implemented by any lambda - or method reference - whose method signature is a match for the one method on the interface. So examining the Comparator interface (simple version):

public Comparator<T> {
    T compare(T o1, T o2);

If a method is looking for a Comparator<Integer>, then it's essentially looking for this signature:

int xxx(Integer o1, Integer o2);

I use "xxx" because the method name is not used for matching purposes.

Therefore, both Integer.min(int a, int b) and Integer.max(int a, int b) are close enough that autoboxing will allow this to appear as a Comparator<Integer> in a method context.

How to modify values of JsonObject / JsonArray directly?

Another approach would be to deserialize into a java.util.Map, and then just modify the Java Map as wanted. This separates the Java-side data handling from the data transport mechanism (JSON), which is how I prefer to organize my code: using JSON for data transport, not as a replacement data structure.

How do I deploy Node.js applications as a single executable file?

JXcore will allow you to turn any nodejs application into a single executable, including all dependencies, in either Windows, Linux, or Mac OS X.

Here is a link to the installer:

And here is a link to how to set it up:

It is very easy to use and I have tested it in both Windows 8.1 and Ubuntu 14.04.

FYI: JXcore is a fork of NodeJS so it is 100% NodeJS compatible, with some extra features.

How do I get a range's address including the worksheet name, but not the workbook name, in Excel VBA?

Ben is right. I also can't think of any way to do this. I'd suggest either the method Ben recommends, or the following to strip the Workbook name off.

Dim cell As Range
Dim address As String
Set cell = Worksheets(1).Cells.Range("A1")
address = cell.address(External:=True)
address = Right(address, Len(address) - InStr(1, address, "]"))

INSERT and UPDATE a record using cursors in oracle

This is a highly inefficient way of doing it. You can use the merge statement and then there's no need for cursors, looping or (if you can do without) PL/SQL.

MERGE INTO studLoad l
USING ( SELECT studId, studName FROM student ) s
ON (l.studId = s.studId)
  UPDATE SET l.studName = s.studName
   WHERE l.studName != s.studName
INSERT (l.studID, l.studName)
VALUES (s.studId, s.studName)

Make sure you commit, once completed, in order to be able to see this in the database.

To actually answer your question I would do it something like as follows. This has the benefit of doing most of the work in SQL and only updating based on the rowid, a unique address in the table.

It declares a type, which you place the data within in bulk, 10,000 rows at a time. Then processes these rows individually.

However, as I say this will not be as efficient as merge.


   cursor c_data is
    select b.rowid as rid, a.studId, a.studName
      from student a
      left outer join studLoad b
        on a.studId = b.studId
       and a.studName <> b.studName

   type t__data is table of c_data%rowtype index by binary_integer;
   t_data t__data;


   open c_data;
      fetch c_data bulk collect into t_data limit 10000;

      exit when t_data.count = 0;

      for idx in t_data.first .. t_data.last loop
         if t_data(idx).rid is null then
            insert into studLoad (studId, studName)
            values (t_data(idx).studId, t_data(idx).studName);
            update studLoad
               set studName = t_data(idx).studName
             where rowid = t_data(idx).rid
         end if;
      end loop;

   end loop;
   close c_data;


Regular expression to match a dot

A . in regex is a metacharacter, it is used to match any character. To match a literal dot, you need to escape it, so \.

XSLT counting elements with a given value

Your xpath is just a little off:


Edit: Cerebrus quite rightly points out that the code in your OP (using the implicit value of a node) is absolutely fine for your purposes. In fact, since it's quite likely you want to work with the "Property" node rather than the "long" node, it's probably superior to ask for //Property[long=$parPropId] than the text() xpath, though you could make a case for the latter on readability grounds.

What can I say, I'm a bit tired today :)

SQL to LINQ Tool

I know that this isn't what you asked for but LINQPad is a really great tool to teach yourself LINQ (and it's free :o).

When time isn't critical, I have been using it for the last week or so instead or a query window in SQL Server and my LINQ skills are getting better and better.

It's also a nice little code snippet tool. Its only downside is that the free version doesn't have IntelliSense.

check if "it's a number" function in Oracle

I'm against using when others so I would use (returning an "boolean integer" due to SQL not suppporting booleans)

create or replace function is_number(param in varchar2) return integer
   ret number;
    ret := to_number(param);
    return 1; --true
    when invalid_number then return 0;

In the SQL call you would use something like

select case when ( is_number( and ( >'0') ) 
            then 'Is a number greater than 0' 
            else 'it is not a number or is not greater than 0' 
       end as valuetype  
  from table myTable

how to break the _.each function in underscore.js

You can't break from the each method—it emulates the native forEach method's behavior, and the native forEach doesn't provide to escape the loop (other than throwing an exception).

However, all hope is not lost! You can use the Array.every method. :)

From that link:

every executes the provided callback function once for each element present in the array until it finds one where callback returns a false value. If such an element is found, the every method immediately returns false.

In other words, you could do something convoluted like this (link to JSFiddle):

[1, 2, 3, 4].every(function(n) {
    return n !== 3;

This will alert 1 through 3, and then "break" out of the loop.

You're using underscore.js, so you'll be pleased to learn that it does provide an every method—they call it every, but as that link mentions, they also provide an alias called all.

Error: "an object reference is required for the non-static field, method or property..."

The error message means that you need to invoke volteado and siprimo on an instance of the Program class. E.g.:

Program p = new Program();
long av = p.volteado(a); // av is "a" but swapped

if (p.siprimo(a) == false && p.siprimo(av) == false)

They cannot be invoked directly from the Main method because Main is static while volteado and siprimo are not.

The easiest way to fix this is to make the volteado and siprimo methods static:

private static bool siprimo(long a)

private static bool volteado(long a)

C# static class constructor

A static constructor looks like this

static class Foo
    static Foo()
         // Static initialization code here

It is executed only once when the type is first used. All classes can have static constructors, not just static classes.

How to check if a user likes my Facebook Page or URL using Facebook's API

You can use (PHP)

$isFan = file_get_contents("" . USER_TOKEN . "&page_id=" . FB_FANPAGE_ID);

That will return one of three:

  • string true string false json
  • formatted response of error if token
  • or page_id are not valid

I guess the only not-using-token way to achieve this is with the signed_request Jason Siffring just posted. My helper using PHP SDK:

function isFan(){
    global $facebook;
    $request = $facebook->getSignedRequest();
    return $request['page']['liked'];

Insert and set value with max()+1 problems

SELECT MAX(col) +1 is not safe -- it does not ensure that you aren't inserting more than one customer with the same customer_id value, regardless if selecting from the same table or any others. The proper way to ensure a unique integer value is assigned on insertion into your table in MySQL is to use AUTO_INCREMENT. The ANSI standard is to use sequences, but MySQL doesn't support them. An AUTO_INCREMENT column can only be defined in the CREATE TABLE statement:

CREATE TABLE `customers` (
  `customer_id` int(11) NOT NULL AUTO_INCREMENT,
  `firstname` varchar(45) DEFAULT NULL,
  `surname` varchar(45) DEFAULT NULL,
  PRIMARY KEY (`customer_id`)

That said, this worked fine for me on 5.1.49:

CREATE TABLE `customers` (
  `customer_id` int(11) NOT NULL DEFAULT '0',
  `firstname` varchar(45) DEFAULT NULL,
  `surname` varchar(45) DEFAULT NULL,
  PRIMARY KEY (`customer_id`)

INSERT INTO customers VALUES (1, 'a', 'b');

INSERT INTO customers 
SELECT MAX(customer_id) + 1, 'jim', 'sock'

How do I make curl ignore the proxy?

Lame answer but: Remember to make sure no proxy is set in a ~/.curlrc file (...).

Change image source with JavaScript

You've got a few changes (this assumes you indeed still want to change the image with an ID of IMG, if not use Shadow Wizard's solution).

Remove a.src and replace with a:

<script type="text/javascript">
function changeImage(a) {

Change your onclick attributes to include a string of the new image source instead of a literal:

onclick='changeImage( "1772031_29_b.jpg" );'

How to count string occurrence in string?

Here is the fastest function!

Why is it faster?

  • Doesn't check char by char (with 1 exception)
  • Uses a while and increments 1 var (the char count var) vs. a for loop checking the length and incrementing 2 vars (usually var i and a var with the char count)
  • Uses WAY less vars
  • Doesn't use regex!
  • Uses an (hopefully) highly optimized function
  • All operations are as combined as they can be, avoiding slowdowns due to multiple operations

    String.prototype.timesCharExist=function(c){var t=0,l=0,c=(c+'')[0];while(l=this.indexOf(c,l)+1)++t;return t};

Here is a slower and more readable version:

    String.prototype.timesCharExist = function ( chr ) {
        var total = 0, last_location = 0, single_char = ( chr + '' )[0];
        while( last_location = this.indexOf( single_char, last_location ) + 1 )
            total = total + 1;
        return total;

This one is slower because of the counter, long var names and misuse of 1 var.

To use it, you simply do this:

    'The char "a" only shows up twice'.timesCharExist('a');

Edit: (2013/12/16)

DON'T use with Opera 12.16 or older! it will take almost 2.5x more than the regex solution!

On chrome, this solution will take between 14ms and 20ms for 1,000,000 characters.

The regex solution takes 11-14ms for the same amount.

Using a function (outside String.prototype) will take about 10-13ms.

Here is the code used:

    String.prototype.timesCharExist=function(c){var t=0,l=0,c=(c+'')[0];while(l=this.indexOf(c,l)+1)++t;return t};

    var x=Array(100001).join('1234567890');



    var timesCharExist=function(x,c){var t=0,l=0,c=(c+'')[0];while(l=x.indexOf(c,l)+1)++t;return t;};


The result of all the solutions should be 100,000!

Note: if you want this function to count more than 1 char, change where is c=(c+'')[0] into c=c+''

Manually map column names with class properties

Here is a simple solution that doesn't require attributes allowing you to keep infrastructure code out of your POCOs.

This is a class to deal with the mappings. A dictionary would work if you mapped all the columns, but this class allows you to specify just the differences. In addition, it includes reverse maps so you can get the field from the column and the column from the field, which can be useful when doing things such as generating sql statements.

public class ColumnMap
    private readonly Dictionary<string, string> forward = new Dictionary<string, string>();
    private readonly Dictionary<string, string> reverse = new Dictionary<string, string>();

    public void Add(string t1, string t2)
        forward.Add(t1, t2);
        reverse.Add(t2, t1);

    public string this[string index]
            // Check for a custom column map.
            if (forward.ContainsKey(index))
                return forward[index];
            if (reverse.ContainsKey(index))
                return reverse[index];

            // If no custom mapping exists, return the value passed in.
            return index;

Setup the ColumnMap object and tell Dapper to use the mapping.

var columnMap = new ColumnMap();
columnMap.Add("Field1", "Column1");
columnMap.Add("Field2", "Column2");
columnMap.Add("Field3", "Column3");

SqlMapper.SetTypeMap(typeof (MyClass), new CustomPropertyTypeMap(typeof (MyClass), (type, columnName) => type.GetProperty(columnMap[columnName])));

How do I prevent mails sent through PHP mail() from going to spam?

$fromMail = 'set your from mail';
$boundary = str_replace(" ", "", date('l jS \of F Y h i s A'));
$subjectMail = "New design submitted by " . $userDisplayName;

$contentHtml = '<div>Dear Admin<br /><br />The following design is submitted by '. $userName .'.<br /><br /><a href="'.$sdLink.'"><b>Click here</b></a> to check the design.</div>';
$contentHtml .= '<div><a href="'.$imageUrl.'"><img src="'.$imageUrl.'" width="250" height="95" border="0" alt="my picture"></a></div>';
$contentHtml .= '<div>Name : '.$name.'<br />Description : '. $description .'</div>';

$headersMail = '';
$headersMail .= 'From: ' . $fromMail . "\r\n" . 'Reply-To: ' . $fromMail . "\r\n";
$headersMail .= 'Return-Path: ' . $fromMail . "\r\n";
$headersMail .= 'MIME-Version: 1.0' . "\r\n";
$headersMail .= "Content-Type: multipart/alternative; boundary = \"" . $boundary . "\"\r\n\r\n";
$headersMail .= '--' . $boundary . "\r\n";
$headersMail .= 'Content-Type: text/html; charset=ISO-8859-1' . "\r\n";
$headersMail .= 'Content-Transfer-Encoding: base64' . "\r\n\r\n";
$headersMail .= rtrim(chunk_split(base64_encode($contentHtml)));

try {
    if (mail($toMail, $subjectMail, "", $headersMail)) {
        $status = 'success';
        $msg = 'Mail sent successfully.';
    } else {
        $status = 'failed';
        $msg = 'Unable to send mail.';
} catch(Exception $e) {
    $msg = $e->getMessage();

This works fine for me.It includes mail with image and a link and works for all sorts of mail ids. The clue is to use all the header perfectly.

If you are testing it from localhost, then set the below before checking:

How to set mail send from localhost xampp:

  1. comment everything in D:/xampp/sendmail/sendmail.ini and mention the below under

    [sendmail] smtp_port=587 error_logfile=error.log debug_logfile=debug.log [email protected] auth_password=your-mail-password [email protected]

  2. In D:/xampp/php/php.ini a. Under

    [mail function]

    SMTP = smtp_port = 587

b. set sendmail_from = [email protected] c. uncomment sendmail_path = "\"D:\xamp\sendmail\sendmail.exe\" -t" Hence it should be look like below

sendmail_path = "\"D:\xamp\sendmail\sendmail.exe\" -t"

d. comment sendmail_path="D:\xamp\mailtodisk\mailtodisk.exe" Hence it should be look like below


e. mail.add_x_header=Off

Error: Uncaught SyntaxError: Unexpected token <

It usually works when you change the directory name, where the file is. It worked for me when I moved it from "js/" to "../js"

How to call a stored procedure from Java and JPA

From JPA 2.1 , JPA supports to call stored procedures using the dynamic StoredProcedureQuery, and the declarative @NamedStoredProcedureQuery.

Vertical align middle with Bootstrap responsive grid

Add !important rule to display: table of your .v-center class.

.v-center {
    display:table !important;
    border:2px solid gray;

Your display property is being overridden by bootstrap to display: block.


How to create <input type=“text”/> dynamically

You could use createElement() method for creating that textbox

ssh script returns 255 error

I was stumped by this. Once I got passed the 255 problem... I ended up with a mysterious error code 1. This is the foo to get that resolved:

 pssh -x '-tt' -h HOSTFILELIST -P "sudo yum -y install glibc"

-P means write the output out as you go and is optional. But the -x '-tt' trick is what forces a psuedo tty to be allocated.

You can get a clue what the error code 1 means this if you try:

ssh AHOST "sudo yum -y install glibc"

You may see:

[slc@bastion-ci ~]$ ssh MYHOST "sudo yum -y install glibc"
sudo: sorry, you must have a tty to run sudo
[slc@bastion-ci ~]$ echo $?

Notice the return code for this is 1, which is what pssh is reporting to you.

I found this -x -tt trick here. Also note that turning on verbose mode (pssh --verbose) for these cases does nothing to help you.

How to clear all input fields in bootstrap modal when clicking data-dismiss button?

enclose your modal body inside a form with an id="myform"

and then


should do the trick

How do I create a ListView with rounded corners in Android?


For those having issues with selection highlight for the top and bottom row where the background rectangle shows up on selection you need to set the selector for your listview to transparent color.


In color.xml just add the following -

<color name="transparent">#00000000</color>

Java - Including variables within strings?

You can always use String.format(....). i.e.,

String string = String.format("A String %s %2d", aStringVar, anIntVar);

I'm not sure if that is attractive enough for you, but it can be quite handy. The syntax is the same as for printf and java.util.Formatter. I've used it much especially if I want to show tabular numeric data.

How to normalize a NumPy array to within a certain range?

A simple solution is using the scalers offered by the sklearn.preprocessing library.

scaler = sk.MinMaxScaler(feature_range=(0, 250))
scaler =
X_scaled = scaler.transform(X)
# Checking reconstruction
X_rec = scaler.inverse_transform(X_scaled)

The error X_rec-X will be zero. You can adjust the feature_range for your needs, or even use a standart scaler sk.StandardScaler()

Check to see if cURL is installed locally?

To extend the answer above and if the case is you are using XAMPP. In the current version of the xampp you cannot locate the curl_exec in the php.ini, just try using

echo '<pre>';
echo '</pre>';

and save to your htdocs. Next go to your browser and paste


if the result looks like this

array(9) {
  string(6) "7.43.0"
  string(13) "i386-pc-win32"
  string(14) "OpenSSL/1.0.2e"
  string(5) "1.2.8"
  array(19) {
    string(4) "dict"
    string(4) "file"
    string(3) "ftp"
    string(4) "ftps"
    string(6) "gopher"
    string(4) "http"
    string(5) "https"
    string(4) "imap"
    string(5) "imaps"
    string(4) "ldap"
    string(4) "pop3"
    string(5) "pop3s"
    string(4) "rtsp"
    string(3) "scp"
    string(4) "sftp"
    string(4) "smtp"
    string(5) "smtps"
    string(6) "telnet"
    string(4) "tftp"

curl is enable

Export MySQL data to Excel in PHP

Just Try With The Following :

PHP Part :

/*******EDIT LINES 3-8*******/
$DB_Server = "localhost"; //MySQL Server    
$DB_Username = "username"; //MySQL Username     
$DB_Password = "password";             //MySQL Password     
$DB_DBName = "databasename";         //MySQL Database Name  
$DB_TBLName = "tablename"; //MySQL Table Name   
$filename = "excelfilename";         //File Name
//create MySQL connection   
$sql = "Select * from $DB_TBLName";
$Connect = @mysql_connect($DB_Server, $DB_Username, $DB_Password) or die("Couldn't connect to MySQL:<br>" . mysql_error() . "<br>" . mysql_errno());
//select database   
$Db = @mysql_select_db($DB_DBName, $Connect) or die("Couldn't select database:<br>" . mysql_error(). "<br>" . mysql_errno());   
//execute query 
$result = @mysql_query($sql,$Connect) or die("Couldn't execute query:<br>" . mysql_error(). "<br>" . mysql_errno());    
$file_ending = "xls";
//header info for browser
header("Content-Type: application/xls");    
header("Content-Disposition: attachment; filename=$filename.xls");  
header("Pragma: no-cache"); 
header("Expires: 0");
/*******Start of Formatting for Excel*******/   
//define separator (defines columns in excel & tabs in word)
$sep = "\t"; //tabbed character
//start of printing column names as names of MySQL fields
for ($i = 0; $i < mysql_num_fields($result); $i++) {
echo mysql_field_name($result,$i) . "\t";
//end of printing column names  
//start while loop to get data
    while($row = mysql_fetch_row($result))
        $schema_insert = "";
        for($j=0; $j<mysql_num_fields($result);$j++)
                $schema_insert .= "NULL".$sep;
            elseif ($row[$j] != "")
                $schema_insert .= "$row[$j]".$sep;
                $schema_insert .= "".$sep;
        $schema_insert = str_replace($sep."$", "", $schema_insert);
        $schema_insert = preg_replace("/\r\n|\n\r|\n|\r/", " ", $schema_insert);
        $schema_insert .= "\t";
        print "\n";

I think this may help you to resolve your problem.

Pad left or right with string.format (not padleft or padright) with arbitrary string

There is another solution.

Implement IFormatProvider to return a ICustomFormatter that will be passed to string.Format :

public class StringPadder : ICustomFormatter
  public string Format(string format, object arg,
       IFormatProvider formatProvider)
     // do padding for string arguments
     // use default for others

public class StringPadderFormatProvider : IFormatProvider
  public object GetFormat(Type formatType)
     if (formatType == typeof(ICustomFormatter))
        return new StringPadder();

     return null;
  public static readonly IFormatProvider Default =
     new StringPadderFormatProvider();

Then you can use it like this :

string.Format(StringPadderFormatProvider.Default, "->{0:x20}<-", "Hello");

why windows 7 task scheduler task fails with error 2147942667

This can happen for more than one reason. In my case this happened due to a permissions issue. The user that the task was running as didn't have permission to write to the logs directory so it failed with this error.

VBA shorthand for x=x+1?

If you want to call the incremented number directly in a function, this solution works bettter:

Function inc(ByRef data As Integer)
    data = data + 1
    inc = data
End Function

for example:

Wb.Worksheets(mySheet).Cells(myRow, inc(myCol))

If the function inc() returns no value, the above line will generate an error.

How do I initialize the base (super) class?


SuperClass.__init__(self, x)


super(SubClass,self).__init__( x )

will work (I prefer the 2nd one, as it adheres more to the DRY principle).

See here:

Cross-Domain Cookies

Cross-site cookies are allowed if:

  1. the Set-Cookie response header includes SameSite=None; Secure as seen here and here
  2. and your browser hasn't disabled 3rd-party cookies.*

Let's clarify a "domain" vs a "site"; I always find a quick reminder of "anatomy of a URL" helps me. In this URL, remember these main parts (got from this paper):

  • the "protocol": https://
  • the "hostname/host":
  • the "port": 8888
  • the "path":/examples/index.html.

Notice the difference between "path" and "site" for Cookie purposes. "path" is not security-related; "site" is security-related:


Servers can set a Path attribute in the Set-Cookie, but it doesn't seem security related:

Note that path was intended for performance, not security. Web pages having the same origin still can access cookie via document.cookie even though the paths are mismatched.


The SameSite attribute, according to article, can restrict or allow cross-site cookies; but what is a "site"?

It's helpful to understand exactly what 'site' means here. The site is the combination of the domain suffix and the part of the domain just before it. For example, the domain is part of the site.

This means what's to the left of is a subdomain; yep, www is the subdomain (but the subdomain is a part of the host; see the BONUS reply in this answer)

In this URL, remember these parts:

  • the "protocol": https://
  • the "hostname" aka "host":
  • (in cases like "", the entire "" is also a hostname)
  • the "port": 8888
  • the "site":
  • the "domain":
  • the "subdomain": www
  • the "path": /examples/index.html

Useful links:

(Be careful; I was testing my feature in Chrome Incognito tab; according to my chrome://settings/cookies; my settings were "Block third party cookies in Incognito", so I can't test Cross-site cookies in Incognito.)

a browser is open to the URL chrome://settings/cookies, which shows that "Block third-party cookies in Incognito" setting is set, choose a setting in your browser that will allow third-party cookies

How to turn off caching on Firefox?

There is no specific option to disable caching only for JavaScript, you will have to disable caching entirely.

FireBug has an option to disable the browser cache on the Network tab's drop down menu.

Changing the text on a label

There are many ways to tackle a problem like this. There are many ways to do this. I'm going to give you the most simple solution to this question I know. When changing the text of a label or any kind of wiget really. I would do it like this.

Name_Of_Label["text"] = "Your New Text"

So when I apply this knowledge to your code. It would look something like this.

from tkinter import*

class MyGUI:
   def __init__(self):
    self.__mainWindow = Tk()
    #self.fram1 = Frame(self.__mainWindow)
    self.labelText = 'Enter amount to deposit'
    self.depositLabel = Label(self.__mainWindow, text = self.labelText)
    self.depositEntry = Entry(self.__mainWindow, width = 10)
    self.depositEntry.bind('<Return>', self.depositCallBack)


  def depositCallBack(self,event):
    self.labelText["text"] = 'change the value'

myGUI = MyGUI()

If this helps please let me know!

How do I remove  from the beginning of a file?

Three words for you:

Byte Order Mark (BOM)

That's the representation for the UTF-8 BOM in ISO-8859-1. You have to tell your editor to not use BOMs or use a different editor to strip them out.

To automatize the BOM's removal you can use awk as shown in this question.

As another answer says, the best would be for PHP to actually interpret the BOM correctly, for that you can use mb_internal_encoding(), like this:

   //Storing the previous encoding in case you have some other piece 
   //of code sensitive to encoding and counting on the default value.      
   $previous_encoding = mb_internal_encoding();

   //Set the encoding to UTF-8, so when reading files it ignores the BOM       

   //Process the CSS files...

   //Finally, return to the previous encoding

   //Rest of the code...

When to create variables (memory management)

It's really a matter of opinion. In your example, System.out.println(5) would be slightly more efficient, as you only refer to the number once and never change it. As was said in a comment, int is a primitive type and not a reference - thus it doesn't take up much space. However, you might want to set actual reference variables to null only if they are used in a very complicated method. All local reference variables are garbage collected when the method they are declared in returns.

Counting unique values in a column in pandas dataframe like in Qlik?

Count distinct values, use nunique:


Count only non-null values, use count:


Count total values including null values, use the size attribute:


Edit to add condition

Use boolean indexing:


OR using query:

df.query('mID == "A"')['hID'].agg(['nunique','count','size'])


nunique    5
count      5
size       5
Name: hID, dtype: int64

MySQL error code: 1175 during UPDATE in MySQL Workbench

I too got the same issue but when I off 'safe updates' in Edit -> Preferences -> SQL Editor -> Safe Updates, still I use to face the error as "Error code 1175 disable safe mode"

My solution for this error is just given the primary key to the table if not given and update the column using those primary key value.

Eg: UPDATE [table name] SET Empty_Column = 'Value' WHERE [primary key column name] = value;

How Do I 'git fetch' and 'git merge' from a Remote Tracking Branch (like 'git pull')

Are you sure you are on the local an-other-branch when you merge?

git fetch origin an-other-branch
git checkout an-other-branch
git merge origin/an-other-branch

The other explanation:

all the changes from the branch you’re trying to merge have already been merged to the branch you’re currently on.
More specifically it means that the branch you’re trying to merge is a parent of your current branch

if you're ahead of the remote repo by one commit, it's the remote repo that's out of date, not you.

But in your case, if git pull works, that just means you are not on the right branch.

Custom toast on Android: a simple example

val inflater = layoutInflater
val container: ViewGroup = findViewById(
val layout: ViewGroup = inflater.inflate(R.layout.custom_toast, container)
val text: TextView = layout.findViewById(
text.text = "This is a custom toast"
with (Toast(applicationContext)) {
    setGravity(Gravity.CENTER_VERTICAL, 0, 0)
    duration = Toast.LENGTH_LONG
    view = layout

<LinearLayout xmlns:android=""
    <ImageView android:src="@drawable/droid"
    <TextView android:id="@+id/text"

Reference :

Controlling a USB power supply (on/off) with Linux

echo '2-1' |sudo tee /sys/bus/usb/drivers/usb/unbind

works for ubuntu

Recursively find all files newer than a given time

So there's another way (and it is portable to some extent_

(python <<EOF
import fnmatch
import os
import os.path as path
import time

matches = []
def find(dirname=None, newerThan=3*24*3600, olderThan=None):
    for root, dirnames, filenames in os.walk(dirname or '.'):
        for filename in fnmatch.filter(filenames, '*'):
            filepath = os.path.join(root, filename)
            ts_now = time.time()
            newer = ts_now - path.getmtime(filepath) < newerThan
            older = ts_now - path.getmtime(filepath) > newerThan
            if newerThan and newer or olderThan and older: print filepath
    for dirname in dirnames:
        if dirname not in ['.', '..']:
            print 'dir:', dirname
) | xargs -I '{}' echo found file modified within 3 days '{}'

How to specify new GCC path for CMake

This question is quite old but still turns up on Google Search. The accepted question wasn't working for me anymore and seems to be aged. The latest information about cmake is written in the cmake FAQ.

There are various ways to change the path of your compiler. One way would be

Set the appropriate CMAKE_FOO_COMPILER variable(s) to a valid compiler name or full path on the command-line using cmake -D. For example:

cmake -G "Your Generator" -D CMAKE_C_COMPILER=gcc-4.2 -D CMAKE_CXX_COMPILER=g++-4.2 path/to/your/source

instead of gcc-4.2 you can write the path/to/your/compiler like this

 cmake -D CMAKE_C_COMPILER=/path/to/gcc/bin/gcc -D CMAKE_CXX_COMPILER=/path/to/gcc/bin/g++ .

Loop code for each file in a directory

Looks for the function glob():

$files = glob("dir/*.jpg");
foreach($files as $jpg){
    echo $jpg, "\n";

Get the system date and split day, month and year

You can split date month year from current date as follows:

DateTime todaysDate = DateTime.Now.Date;


int day = todaysDate.Day;


int month = todaysDate.Month;


int year = todaysDate.Year;

Find all tables containing column with specified name - MS SQL Server

I wanted something for tables and views that didn't make my eyes bleed.


    t.TABLE_TYPE AS [Type],
    c.TABLE_NAME AS [Object],
    c.COLUMN_NAME AS [Column]
    c.COLUMN_NAME LIKE '%myName%'


Type        Object   Column
BASE TABLE  Table1   myName1
BASE TABLE  Table2   myName2
VIEW        View1    myName1
VIEW        View2    myName2

How to print the data in byte array as characters?

If you want to print the bytes as chars you can use the String constructor.

byte[] bytes = new byte[] { -1, -128, 1, 127 };
System.out.println(new String(bytes, 0));

Best way to get user GPS location in background in Android

I have try to my code and got success try this

package com.mobeyosoft.latitudelongitude;

import android.content.Context;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.widget.Toast;

 * Created by 5943 6417 on 14-09-2016.
public class LocationService extends Service
    public static final String BROADCAST_ACTION = "Hello World";
    private static final int TWO_MINUTES = 1000 * 60 * 1;
    public LocationManager locationManager;
    public MyLocationListener listener;
    public Location previousBestLocation = null;

    Context context;

    Intent intent;
    int counter = 0;

    public void onCreate() {
        intent = new Intent(BROADCAST_ACTION);

    public void onStart(Intent intent, int startId) {
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        listener = new MyLocationListener();
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 4000, 0, listener);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 4000, 0, listener);

    public IBinder onBind(Intent intent){
        return null;

    protected boolean isBetterLocation(Location location, Location currentBestLocation) {
        if (currentBestLocation == null) {
            // A new location is always better than no location
            return true;

        // Check whether the new location fix is newer or older
        long timeDelta = location.getTime() - currentBestLocation.getTime();
        boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
        boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
        boolean isNewer = timeDelta > 0;

        // If it's been more than two minutes since the current location, use the new location
        // because the user has likely moved
        if (isSignificantlyNewer) {
            return true;
            // If the new location is more than two minutes older, it must be worse
        } else if (isSignificantlyOlder) {
            return false;

        // Check whether the new location fix is more or less accurate
        int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
        boolean isLessAccurate = accuracyDelta > 0;
        boolean isMoreAccurate = accuracyDelta < 0;
        boolean isSignificantlyLessAccurate = accuracyDelta > 200;

        // Check if the old and new location are from the same provider
        boolean isFromSameProvider = isSameProvider(location.getProvider(),

        // Determine location quality using a combination of timeliness and accuracy
        if (isMoreAccurate) {
            return true;
        } else if (isNewer && !isLessAccurate) {
            return true;
        } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
            return true;
        return false;

    /** Checks whether two providers are the same */
    private boolean isSameProvider(String provider1, String provider2) {
        if (provider1 == null) {
            return provider2 == null;
        return provider1.equals(provider2);

    public void onDestroy() {
        // handler.removeCallbacks(sendUpdatesToUI);
        Log.v("STOP_SERVICE", "DONE");

    public static Thread performOnBackgroundThread(final Runnable runnable) {
        final Thread t = new Thread() {
            public void run() {
                try {
                } finally {

        return t;

    public class MyLocationListener implements LocationListener{

        public void onLocationChanged(final Location loc)
            Log.i("**********", "Location changed");
            if(isBetterLocation(loc, previousBestLocation)) {
                Toast.makeText(context, "Latitude" + loc.getLatitude() + "\nLongitude"+loc.getLongitude(),Toast.LENGTH_SHORT).show();
                intent.putExtra("Latitude", loc.getLatitude());
                intent.putExtra("Longitude", loc.getLongitude());
                intent.putExtra("Provider", loc.getProvider());


        public void onProviderDisabled(String provider)
            Toast.makeText( getApplicationContext(), "Gps Disabled", Toast.LENGTH_SHORT ).show();

        public void onProviderEnabled(String provider)
            Toast.makeText( getApplicationContext(), "Gps Enabled", Toast.LENGTH_SHORT).show();

        public void onStatusChanged(String provider, int status, Bundle extras)



Python sys.argv lists and indexes

As explained in the different asnwers already, sys.argv contains the command line arguments that called your Python script.

However, Python comes with libraries that help you parse command line arguments very easily. Namely, the new standard argparse. Using argparse would spare you the need to write a lot of boilerplate code.

How do you create vectors with specific intervals in R?

In R the equivalent function is seq and you can use it with the option by:

seq(from = 5, to = 100, by = 5)
# [1]   5  10  15  20  25  30  35  40  45  50  55  60  65  70  75  80  85  90  95 100

In addition to by you can also have other options such as length.out and along.with.

length.out: If you want to get a total of 10 numbers between 0 and 1, for example:

seq(0, 1, length.out = 10)
# gives 10 equally spaced numbers from 0 to 1

along.with: It takes the length of the vector you supply as input and provides a vector from 1:length(input).

# [1] 1 2 3

Although, instead of using the along.with option, it is recommended to use seq_along in this case. From the documentation for ?seq

seq is generic, and only the default method is described here. Note that it dispatches on the class of the first argument irrespective of argument names. This can have unintended consequences if it is called with just one argument intending this to be taken as along.with: it is much better to use seq_along in that case.

seq_along: Instead of seq(along.with(.))

# [1] 1 2 3

Hope this helps.

Edit a specific Line of a Text File in C#

the easiest way is :

static void lineChanger(string newText, string fileName, int line_to_edit)
     string[] arrLine = File.ReadAllLines(fileName);
     arrLine[line_to_edit - 1] = newText;
     File.WriteAllLines(fileName, arrLine);

usage :

lineChanger("new content for this line" , "sample.text" , 34);

variable or field declared void

The thing is that, when you call a function you should not write the type of the function, that means you should call the funnction just like


Subprocess changing directory

I guess these days you would do:

import subprocess["pwd"], cwd="sub-dir")

ImportError: No module named six

If pip "says" six is installed but you're still getting:

ImportError: No module named six.moves

try re-installing six (worked for me):

pip uninstall six
pip install six

Why check both isset() and !empty()

This is completely redundant. empty is more or less shorthand for !isset($foo) || !$foo, and !empty is analogous to isset($foo) && $foo. I.e. empty does the reverse thing of isset plus an additional check for the truthiness of a value.

Or in other words, empty is the same as !$foo, but doesn't throw warnings if the variable doesn't exist. That's the main point of this function: do a boolean comparison without worrying about the variable being set.

The manual puts it like this:

empty() is the opposite of (boolean) var, except that no warning is generated when the variable is not set.

You can simply use !empty($vars[1]) here.

Android ListView not refreshing after notifyDataSetChanged

Try like this:


instead of:


You have to notifyDataSetChanged() to the ListView not to the adapter class.

How can I get a precise time, for example in milliseconds in Objective-C?

Functions based on mach_absolute_time are good for short measurements.
But for long measurements important caveat is that they stop ticking while device is asleep.

There is a function to get time since boot. It doesn't stop while sleeping. Also, gettimeofday is not monotonic, but in my experiments I've always see that boot time changes when system time changes, so I think it should work fine.

func timeSinceBoot() -> TimeInterval
    var bootTime = timeval()
    var currentTime = timeval()
    var timeZone = timezone()

    let mib = UnsafeMutablePointer<Int32>.allocate(capacity: 2)
    mib[0] = CTL_KERN
    mib[1] = KERN_BOOTTIME
    var size = MemoryLayout.size(ofValue: bootTime)

    var timeSinceBoot = 0.0

    gettimeofday(&currentTime, &timeZone)

    if sysctl(mib, 2, &bootTime, &size, nil, 0) != -1 && bootTime.tv_sec != 0 {
        timeSinceBoot = Double(currentTime.tv_sec - bootTime.tv_sec)
        timeSinceBoot += Double(currentTime.tv_usec - bootTime.tv_usec) / 1000000.0
    return timeSinceBoot

And since iOS 10 and macOS 10.12 we can use CLOCK_MONOTONIC:

if #available(OSX 10.12, *) {
    var uptime = timespec()
    if clock_gettime(CLOCK_MONOTONIC_RAW, &uptime) == 0 {
        return Double(uptime.tv_sec) + Double(uptime.tv_nsec) / 1000000000.0

To sum it up:

  • Date.timeIntervalSinceReferenceDate — changes when system time changes, not monotonic
  • CFAbsoluteTimeGetCurrent() — not monotonic, may go backward
  • CACurrentMediaTime() — stops ticking when device is asleep
  • timeSinceBoot() — doesn't sleep, but might be not monotonic
  • CLOCK_MONOTONIC — doesn't sleep, monotonic, supported since iOS 10

Error in Chrome only: XMLHttpRequest cannot load file URL No 'Access-Control-Allow-Origin' header is present on the requested resource

If your problem is like the following while using Google Chrome:

[XMLHttpRequest cannot load file. Received an invalid response. Origin 'null' is therefore not allowed access.]

Then create a batch file by following these steps:

Open notepad in Desktop.

  1. Just copy and paste the followings in your currently opened notepad file:

start "chrome" "C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --allow-file-access-from-files exit

  1. Note: In the previous line, Replace the full absolute address with your location of chrome installation. [To find it...Right click your short cut of chrome.exe link or icon and Click on Properties and copy-paste the target link][Remember : start to files in one line, & exit in another line by pressing enter]
  2. Save the file as fileName.bat [Very important: .bat]
  3. If you want to change the file later then right-click on the .bat file and click on edit. After modifying, save the file.

This will do what? It will open Chrome.exe with file access. Now, from any location in your computer, browse your html files with Google Chrome. I hope this will solve the XMLHttpRequest problem.

Keep in mind : Just use the shortcut bat file to open Chrome when you require it. Tell me if it solves your problem. I had a similar problem and I solved it in this way. Thanks.

JSON.parse unexpected token s

Because JSON has a string data type (which is practically anything between " and "). It does not have a data type that matches something

Delete all lines starting with # or ; in Notepad++



Replace with nothing. The ^ indicates the start of a line, the [#;] is a character class to match either # or ;, and .* matches anything else in the line.

In versions of Notepad++ before 6.0, you won't be able to actually remove the lines due to a limitation in its regex engine; the replacement results in blank lines for each line matched. In other words, this:

# foo
; bar

Will turn into:


However, the replacement will work in Notepad++ 6.0 if you add \r, \n or \r\n to the end of the pattern, depending on which line ending your file is using, resulting in:


How to top, left justify text in a <td> cell that spans multiple rows

 <td rowspan="2" style="text-align:left;vertical-align:top;padding:0">Save a lot</td>

That should do it.

Unsupported major.minor version 52.0 when rendering in Android Studio

Unsupported major.minor version 52.0

When a higher JDK is used for compilation it creates class file with higher version and when a lower JDK is used to run the program it found that higher version of class file not supported at JVM level and results in java.lang.UnsupportedClassVersionError.

How to fix

  • Increase the JAVA version you are using to run your program

You can follow some tricks

  • Call stable version classpath '' // 2.3.0

Configuring Gradle

To enable the Java 8 language features and Jack for your project, enter the following in your module-level build.gradle file:

android {
  defaultConfig {
    jackOptions {
      enabled true
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8

Courtesy goes to Java 8 Language Features

Just select "API 23: Android 6.0" from preview section .

enter image description here

Angular: Cannot Get /

Generally it is a versioning issue. Node.js v8 cannot compile with angular-cli 6.0 or later. angularcli v6 and above will work for lastest node versions. Please make sure if your node version is v8, then you need to install angular-cli upto 1.7.4. enter ng -v command in cmd and check the cli and node versions.

SQL QUERY replace NULL value in a row with a value from the previous known value

This is the solution for MS Access.

The example table is called tab, with fields id and val.

SELECT (SELECT last(val)
          FROM tab AS temp
          WHERE >= AND temp.val IS NOT NULL) AS val2, *
  FROM tab;

Convert String to double in Java

This is what I would do

    public static double convertToDouble(String temp){
       String a = temp;
       //replace all commas if present with no comma
       String s = a.replaceAll(",","").trim(); 
      // if there are any empty spaces also take it out.          
      String f = s.replaceAll(" ", ""); 
      //now convert the string to double
      double result = Double.parseDouble(f); 
    return result; // return the result

For example you input the String "4 55,63. 0 " the output will the double number 45563.0

Vim and Ctags tips and tricks

I adapted the SetTags() search function above (which should be replaced by the equivalent set tags+=./tags;/) to work for cscope. Seems to work!

"cscope file-searching alternative
function SetCscope()
    let curdir = getcwd()

    while !filereadable("cscope.out") && getcwd() != "/"
            cd ..

    if filereadable("cscope.out")
            execute "cs add " . getcwd() . "/cscope.out"

    execute "cd " . curdir

call SetCscope()

Can I get a patch-compatible output from git-diff?

If you want to use patch you need to remove the a/ b/ prefixes that git uses by default. You can do this with the --no-prefix option (you can also do this with patch's -p option):

git diff --no-prefix [<other git-diff arguments>]

Usually though, it is easier to use straight git diff and then use the output to feed to git apply.

Most of the time I try to avoid using textual patches. Usually one or more of temporary commits combined with rebase, git stash and bundles are easier to manage.

For your use case I think that stash is most appropriate.

# save uncommitted changes
git stash

# do a merge or some other operation
git merge some-branch

# re-apply changes, removing stash if successful
# (you may be asked to resolve conflicts).
git stash pop

What is the easiest way to get the current day of the week in Android?

public String weekdays[] = new      DateFormatSymbols(Locale.ITALIAN).getWeekdays();
 Calendar c = Calendar.getInstance();
 Date date = new Date();
 int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);

How to make a div with no content have a width?

Either use padding , height or &nbsp for width to take effect with empty div


Non zero min-height also works great

Cannot create cache directory .. or directory is not writable. Proceeding without cache in Laravel

I had a similar problem recently, and needed to change the permissions of my vendor folder

By running following commands :

  1. php artisan cache:clear
  2. chmod -R 777 storage vendor
  3. composer dump-autoload

I need to give all the permissions required to open and write vendor files to solve this issue

How to test enum types?

I agree with aberrant80.

For enums, I test them only when they actually have methods in them. If it's a pure value-only enum like your example, I'd say don't bother.

But since you're keen on testing it, going with your second option is much better than the first. The problem with the first is that if you use an IDE, any renaming on the enums would also rename the ones in your test class.

I would expand on it by adding that unit testings an Enum can be very useful. If you work in a large code base, build time starts to mount up and a unit test can be a faster way to verify functionality (tests only build their dependencies). Another really big advantage is that other developers cannot change the functionality of your code unintentionally (a huge problem with very large teams).

And with all Test Driven Development, tests around an Enums Methods reduce the number of bugs in your code base.

Simple Example

public enum Multiplier {

    private final double multiplier;

    Multiplier(double multiplier) {
        this.multiplier = multiplier;

    Double applyMultiplier(Double value) {
        return multiplier * value;


public class MultiplierTest {

    public void should() {
        assertThat(Multiplier.DOUBLE.applyMultiplier(1.0), is(2.0));
        assertThat(Multiplier.TRIPLE.applyMultiplier(1.0), is(3.0));

How to know if a Fragment is Visible?

If you want to know when use is looking at the fragment you should use


instead of


First of all isVisible() already checks for isAdded() so no need for calling both. Second, non-of these two means that user is actually seeing your fragment. Only isResumed() makes sure that your fragment is in front of the user and user can interact with it if thats whats you are looking for.

How to check if a windows form is already open, and close it if it is?

 private static Form IsFormAlreadyOpen(Type formType)
     return Application.OpenForms.Cast<Form>().FirstOrDefault(openForm => openForm.GetType() == formType);

C# 4.0: Convert pdf to byte[] and vice versa

using (FileStream fs = new FileStream("sample.pdf", FileMode.Open, FileAccess.Read))
                byte[] bytes = new byte[fs.Length];
                int numBytesToRead = (int)fs.Length;
                int numBytesRead = 0;
                while (numBytesToRead > 0)
                    // Read may return anything from 0 to numBytesToRead.
                    int n = fs.Read(bytes, numBytesRead, numBytesToRead);

                    // Break when the end of the file is reached.
                    if (n == 0)

                    numBytesRead += n;
                    numBytesToRead -= n;
                numBytesToRead = bytes.Length;

Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints

I also had this issue and it was resolved after modifying the *.xsd to reflect the revised size of the column changed in the underlying SQL server.

Print to the same line and not a new line?

for Console you'll probably need


to force update. I think using , in print will block stdout from flushing and somehow it won't update

java.lang.NoClassDefFoundError: org/hamcrest/SelfDescribing

It sounds like a classpath issue, so there are a few different ways to go about it. Where does org/hamcret/SelfDescribing come from? Is that your class or in a different jar?

Try going to your project Build Path and on the Libraries tab, add a Library. You should be able to choose JUnit to your project. This is a little bit different than just having the JUnit jar file In your project.

In your Run Configuration for the JUnit test, check the Classpath. You could probably fix this by adding making sure your Classpath can see that SelfDescribing class there. The Run option in Eclipse has a different set of options for the JUnit options.

Get the Selected value from the Drop down box in PHP

You have to give a name attribute on your <select /> element, and then use it from the $_POST or $_GET (depending on how you transmit data) arrays in PHP. Be sure to sanitize user input, though.

How can I compare two strings in java and define which of them is smaller than the other alphabetically?

Haven't you heard about the Comparable interface being implemented by String ? If no, try to use


And it will output a good root for a solution to your problem.

Can't bind to 'routerLink' since it isn't a known property

You need to add RouterMoudle into imports sections of the module containing the Header component

C# getting its own class name

Try this:


Disable button after click in JQuery

Consider also .attr()

$("#roommate_but").attr("disabled", true); worked for me.

What does `return` keyword mean inside `forEach` function?

The return exits the current function, but the iterations keeps on, so you get the "next" item that skips the if and alerts the 4...

If you need to stop the looping, you should just use a plain for loop like so:

$('button').click(function () {
   var arr = [1, 2, 3, 4, 5];
   for(var i = 0; i < arr.length; i++) {
     var n = arr[i]; 
     if (n == 3) {

You can read more about js break & continue here:

What is a practical, real world example of the Linked List?

I remember, many years ago, in one of my first college classes, wondering where I would ever , ever use a linked list. Today, I don't think there is a single project I work on where I haven't used one, and in many places. It's an incredibly fundamental data structure, and believe me, it's used heavily in the real world.

For example:

  • A list of images that need to be burned to a CD in a medical imaging application
  • A list of users of a website that need to be emailed some notification
  • A list of objects in a 3D game that need to be rendered to the screen

It may seem slightly useless to you now, but a few years from now, ask yourself the same question, you'll find yourself surprised that you ever wondered where it would be used.

Edit: I noticed in one of your comments you asked about why the pointer matters. Someone rightly answered that the pointer doesn't really matter to a user of a linked list. A user just wants a list that contains a, well, list of things. How that list "contains" that list of things doesn't really matter to the user. The pointer is part of that "how". Imagine a line, drawn on the floor, that leads to a teller. People need to be standing on that line to be able to get to the teller. That line is a (and I admit, this is a bit of a stretch) analogy for the pointer a linked list uses. The first person, at the teller, on the line, is the head of the list. The person directly behind them on the line is the next in the list. And finally, the last person in the line, on the line, is the tail of the list.

How do I round a float upwards to the nearest int in C#?

The easiest is to just add 0.5f to it and then cast this to an int.

How to convert UTC timestamp to device local time in android

The answer from @prgDevelop returns 0 on my Android Marsmallow. Must return 7200000. These changes make it work fine:

int offset = TimeZone.getTimeZone(Time.getCurrentTimezone()).getRawOffset() + TimeZone.getTimeZone(Time.getCurrentTimezone()).getDSTSavings();

How to disable/enable select field using jQuery?

You would like to use code like this:

  <input type="checkbox" id="pizza" name="pizza" value="yes">
  <label for="pizza">I would like to order a</label>
  <select id="pizza_kind" name="pizza_kind">
    <option>(choose one)</option>
    <option value="margaritha">Margaritha</option>
    <option value="hawai">Hawai</option>

<script src=""></script>
  var update_pizza = function () {
    if ($("#pizza").is(":checked")) {
        $('#pizza_kind').prop('disabled', false);
    else {
        $('#pizza_kind').prop('disabled', 'disabled');

?Here is working example

How do I make jQuery wait for an Ajax call to finish before it returns?

The underlying XMLHttpRequest object (used by jQuery to make the request) supports the asynchronous property. Set it to false. Like

async: false

Update row values where certain condition is met in pandas

You can do the same with .ix, like this:

In [1]: df = pd.DataFrame(np.random.randn(5,4), columns=list('abcd'))

In [2]: df
          a         b         c         d
0 -0.323772  0.839542  0.173414 -1.341793
1 -1.001287  0.676910  0.465536  0.229544
2  0.963484 -0.905302 -0.435821  1.934512
3  0.266113 -0.034305 -0.110272 -0.720599
4 -0.522134 -0.913792  1.862832  0.314315

In [3]: df.ix[df.a>0, ['b','c']] = 0

In [4]: df
          a         b         c         d
0 -0.323772  0.839542  0.173414 -1.341793
1 -1.001287  0.676910  0.465536  0.229544
2  0.963484  0.000000  0.000000  1.934512
3  0.266113  0.000000  0.000000 -0.720599
4 -0.522134 -0.913792  1.862832  0.314315


After the extra information, the following will return all columns - where some condition is met - with halved values:

>> condition = df.a > 0
>> df[condition][[i for i in df.columns.values if i not in ['a']]].apply(lambda x: x/2)

I hope this helps!

Using grep to search for hex strings in a file

I just used this:

grep -c $'\x0c' filename

To search for and count a page control character in the file..

So to include an offset in the output:

grep -b -o $'\x0c' filename | less

I am just piping the result to less because the character I am greping for does not print well and the less displays the results cleanly. Output example:


Git clone without .git directory


git clone --depth=1 --branch=master git://someserver/somerepo dirformynewrepo
rm -rf ./dirformynewrepo/.git
  • The depth option will make sure to copy the least bit of history possible to get that repo.
  • The branch option is optional and if not specified would get master.
  • The second line will make your directory dirformynewrepo not a Git repository any more.
  • If you're doing recursive submodule clone, the depth and branch parameter don't apply to the submodules.


Here's an approach that doesn't require the brute-force 'ignore' which would only work if there was a key violation. This way works based on any conditions you specify in the update.

Try this...

-- Try to update any existing row
UPDATE players
SET age=32
WHERE user_name='steven';

-- If no update happened (i.e. the row didn't exist) then insert one
INSERT INTO players (user_name, age)
SELECT 'steven', 32
WHERE (Select Changes() = 0);

How It Works

The 'magic sauce' here is using Changes() in the Where clause. Changes() represents the number of rows affected by the last operation, which in this case is the update.

In the above example, if there are no changes from the update (i.e. the record doesn't exist) then Changes() = 0 so the Where clause in the Insert statement evaluates to true and a new row is inserted with the specified data.

If the Update did update an existing row, then Changes() = 1 (or more accurately, not zero if more than one row was updated), so the 'Where' clause in the Insert now evaluates to false and thus no insert will take place.

The beauty of this is there's no brute-force needed, nor unnecessarily deleting, then re-inserting data which may result in messing up downstream keys in foreign-key relationships.

Additionally, since it's just a standard Where clause, it can be based on anything you define, not just key violations. Likewise, you can use Changes() in combination with anything else you want/need anywhere expressions are allowed.

List of zeros in python


you can replace 4 in the above example with whatever number you want.

Drop data frame columns by name

If you have a large data.frame and are low on memory use [ . . . . or rm and within to remove columns of a data.frame, as subset is currently (R 3.6.2) using more memory - beside the hint of the manual to use subset interactively.

getData <- function() {
  n <- 1e7
  data.frame(a = runif(n), b = runif(n), c = runif(n), d = runif(n))

DF <- getData()
tt <- sum(.Internal(gc(FALSE, TRUE, TRUE))[13:14])
DF <- DF[setdiff(names(DF), c("a", "c"))] ##
#DF <- DF[!(names(DF) %in% c("a", "c"))] #Alternative
#DF <- DF[-match(c("a","c"),names(DF))]  #Alternative
sum(.Internal(gc(FALSE, FALSE, TRUE))[13:14]) - tt
#0.1 MB are used

DF <- getData()
tt <- sum(.Internal(gc(FALSE, TRUE, TRUE))[13:14])
DF <- subset(DF, select = -c(a, c)) ##
sum(.Internal(gc(FALSE, FALSE, TRUE))[13:14]) - tt
#357 MB are used

DF <- getData()
tt <- sum(.Internal(gc(FALSE, TRUE, TRUE))[13:14])
DF <- within(DF, rm(a, c)) ##
sum(.Internal(gc(FALSE, FALSE, TRUE))[13:14]) - tt
#0.1 MB are used

DF <- getData()
tt <- sum(.Internal(gc(FALSE, TRUE, TRUE))[13:14])
DF[c("a", "c")]  <- NULL ##
sum(.Internal(gc(FALSE, FALSE, TRUE))[13:14]) - tt
#0.1 MB are used

MySQL Incorrect datetime value: '0000-00-00 00:00:00'

I wasn't able to do this:

UPDATE users SET created = NULL WHERE created = '0000-00-00 00:00:00'

(on MySQL 5.7.13).

I kept getting the Incorrect datetime value: '0000-00-00 00:00:00' error.

Strangely, this worked: SELECT * FROM users WHERE created = '0000-00-00 00:00:00'. I have no idea why the former fails and the latter works... maybe a MySQL bug?

At any case, this UPDATE query worked:

UPDATE users SET created = NULL WHERE CAST(created AS CHAR(20)) = '0000-00-00 00:00:00'

C++ Remove new line from multiline string

Another way to do it in the for loop

void rm_nl(string &s) {
    for (int p = s.find("\n"); p != (int) string::npos; p = s.find("\n"))


string data = "\naaa\nbbb\nccc\nddd\n";
cout << data; // data = aaabbbcccddd

Expand a div to fill the remaining width

Here, this might help...

  <style type="text/css">_x000D_ {_x000D_
      background: #EEE;_x000D_
      height: 100px;_x000D_
      width: 500px;_x000D_
    div.left {_x000D_
      background: #999;_x000D_
      float: left;_x000D_
      height: 100%;_x000D_
      width: auto;_x000D_
    div.right {_x000D_
      background: #666;_x000D_
      height: 100%;_x000D_
    div.clear {_x000D_
      clear: both;_x000D_
      height: 1px;_x000D_
      overflow: hidden;_x000D_
      font-size: 0pt;_x000D_
      margin-top: -1px;_x000D_
  <div class="box">_x000D_
    <div class="left">Tree</div>_x000D_
    <div class="right">View</div>_x000D_
    <div class="clear" />_x000D_

How can I check whether an array is null / empty?

Method to check array for null or empty also is present on org.apache.commons.lang:

import org.apache.commons.lang.ArrayUtils;


Setting max width for body using Bootstrap

Unfortunately none of the above solved the problem for me.

I didn't want to edit the bootstrap-responsive.css so I went the easy way:

  1. Create a css with priority over bootstrap-responsive.css
  2. Copy all the content of the @media (min-width: 768px) and (max-width: 979px) (line 461 with latest bootstrap version 2.3.1 as of today)
  3. Paste it in your high priority css
  4. In your css, put @media (min-width: 979px) in the place where it said @media (min-width: 768px) and (max-width: 979px) before. This sets the from 768 to 979 style to everything above 768.

That's it. It's not optimal, you will have duplicated css, but it works 100% perfect!

Get a pixel from HTML Canvas?

Note that getImageData returns a snapshot. Implications are:

  • Changes will not take effect until subsequent putImageData
  • getImageData and putImageData calls are relatively slow

How to view the roles and permissions granted to any database user in Azure SQL server instance?

Per the MSDN documentation for sys.database_permissions, this query lists all permissions explicitly granted or denied to principals in the database you're connected to:

SELECT DISTINCT pr.principal_id,, pr.type_desc, 
    pr.authentication_type_desc, pe.state_desc, pe.permission_name
FROM sys.database_principals AS pr
JOIN sys.database_permissions AS pe
    ON pe.grantee_principal_id = pr.principal_id;

Per Managing Databases and Logins in Azure SQL Database, the loginmanager and dbmanager roles are the two server-level security roles available in Azure SQL Database. The loginmanager role has permission to create logins, and the dbmanager role has permission to create databases. You can view which users belong to these roles by using the query you have above against the master database. You can also determine the role memberships of users on each of your user databases by using the same query (minus the filter predicate) while connected to them.

Changing SqlConnection timeout

You need to use command.CommandTimeout

Need to find element in selenium by css

By.cssSelector(".ban") or By.cssSelector(".hot") or By.cssSelector("") should all select it unless there is another element that has those classes.

In CSS, .name means find an element that has a class with name. means to find an element that has all of those classes (in the same element).

However, each of those selectors will select only the first element that matches it on the page. If you need something more specific, please post the HTML of the other elements that have those classes.

TypeError: string indices must be integers, not str // working with dict

time1 is the key of the most outer dictionary, eg, feb2012. So then you're trying to index the string, but you can only do this with integers. I think what you wanted was:

for info in courses[time1][course]:

As you're going through each dictionary, you must add another nest.

update query with join on two tables

Using table aliases in the join condition:

update addresses a
set cid = 
from customers b 
where =

How to install 2 Anacondas (Python 2 and 3) on Mac OS

There is no need to install Anaconda again. Conda, the package manager for Anaconda, fully supports separated environments. The easiest way to create an environment for Python 2.7 is to do

conda create -n python2 python=2.7 anaconda

This will create an environment named python2 that contains the Python 2.7 version of Anaconda. You can activate this environment with

source activate python2

This will put that environment (typically ~/anaconda/envs/python2) in front in your PATH, so that when you type python at the terminal it will load the Python from that environment.

If you don't want all of Anaconda, you can replace anaconda in the command above with whatever packages you want. You can use conda to install packages in that environment later, either by using the -n python2 flag to conda, or by activating the environment.

Removing all non-numeric characters from string in Python

Not sure if this is the most efficient way, but:

>>> ''.join(c for c in "abc123def456" if c.isdigit())

The ''.join part means to combine all the resulting characters together without any characters in between. Then the rest of it is a list comprehension, where (as you can probably guess) we only take the parts of the string that match the condition isdigit.

Set Google Maps Container DIV width and height 100%

You can set height to -webkit-fill-available

<!-- Maps Container -->
<div id="map_canvas" style="height:-webkit-fill-available;width:100px;"></div>

What is the list of valid @SuppressWarnings warning names in Java?

I noticed that //noinspection can be auto-generated in IntelliJ

  • make sure you have not already a plan @SuppressWarninigs before the statement
  • Now you can auto-generate the specific //noinspection by hitting Alt+Enter when you have the warning selected and then use the right arrow key to see the Suppress for ... option

Ended up here when I wanted to suppress a "switch has too few case labels" warning from IntelliJ. I did not find a complete List for IntelliJ's @SuppressWarning support but //noinspection did the trick for me.

Where can I find System.Web.Helpers, System.Web.WebPages, and System.Web.Razor?

You will find these assemblies in the Extensions group under Assemblies in Visual Studio 2010, 2012 & 2013 (Reference Manager)

Create a txt file using batch file in a specific folder

This code written above worked for me as well. Although, you can use the code I am writing here:

@echo off


If you want to write some text to dblank.txt then add the following line in the end of your code

@echo Writing text to dblank.txt> dblank.txt

Use Excel pivot table as data source for another Pivot Table

You have to convert the pivot to values first before you can do that:

  • Remove the subtotals
  • Repeat the row items
  • Copy / Paste values
  • Insert a new pivot table

What is the meaning of "$" sign in JavaScript

As all the other answers say; it can be almost anything but is usually "JQuery".

However, in ES6 it is a string interpolation operator in a template "literal" eg.

var s = "new" ; // you can put whatever you think appropriate here.
var s2 = `There are so many ${s} ideas these days !!` ; //back-ticks not quotes
console.log(s2) ;


There are so many new ideas these days !!

Get public/external IP address?

In theory your router should be able to tell you the public IP address of the network, but the way of doing this will necessarily be inconsistent/non-straightforward, if even possible with some router devices.

The easiest and still a very reliable method is to send a request to a web page that returns your IP address as the web server sees it. provides a good service for this:

What is returned is an extremely simple/short HTML document, containing the text Current IP Address: (fake IP), which is trivial to extract from the HTTP response.

How to do SELECT MAX in Django?

I've tested this for my project, it finds the max/min in O(n) time:

from django.db.models import Max

# Find the maximum value of the rating and then get the record with that rating. 
# Notice the double underscores in rating__max
max_rating = App.objects.aggregate(Max('rating'))['rating__max']
return App.objects.get(rating=max_rating)

This is guaranteed to get you one of the maximum elements efficiently, rather than sorting the whole table and getting the top (around O(n*logn)).

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.

How do you change the formatting options in Visual Studio Code?

Same thing happened to me just now. I set prettier as the Default Formatter in Settings and it started working again. My Default Formatter was null.

To set VSCODE Default Formatter

File -> Preferences -> Settings (for Windows) Code -> Preferences -> Settings (for Mac)

Search for "Default Formatter". In the dropdown, prettier will show as esbenp.prettier-vscode.

VSCODE Editor Option

OS X: equivalent of Linux's wget

brew install wget

Homebrew is a package manager for OSX analogous to yum, apt-get, choco, emerge, etc. Be aware that you will also need to install Xcode and the Command Line Tools. Virtually anyone who uses the command line in OSX will want to install these things anyway.

If you can't or don't want to use homebrew, you could also:

Install wget manually:

curl -# "" -o "wget.tar.xz"
tar xf wget.tar.xz
cd wget-1.17.1
./configure --with-ssl=openssl -with-libssl-prefix=/usr/local/ssl && make -j8 && make install

Or, use a bash alias:

function _wget() { curl "${1}" -o $(basename "${1}") ; };
alias wget='_wget'

ImportError: No module named tensorflow

I had a more basic problem when I received this error.

The "Validate your installation" instructions say to type: python

However, I have both 2.7 and 3.6 installed. Because I used pip3 to install tensorflow, I needed to type: python3

Using the correct version, I could import the "tensorflow" module.

Getting new Twitter API consumer and secret keys

consumer_key = API key

consumer_secret = API key secret

Found it hidden in Twitter API Docs

Twitter Docs screenshot

Twitter's naming is just too confusing.

Locate Git installation folder on Mac OS X

You can also try with /usr/local/bin/git it worked for me

How to get element by class name?

you can use


suppose you have some elements and applied a class name 'test', so, you can get elements like as following

var tests = document.getElementsByClassName('test');

its returns an instance NodeList, or its superset: HTMLCollection (FF).

Read more

how to read xml file from url using php

$url = ''; $xml = simpleXML_load_file($url,"SimpleXMLElement",LIBXML_NOCDATA);

$url can be php file, as long as the file generate xml format data as output.

How can I expand and collapse a <div> using javascript?

Take a look at toggle() jQuery function :

Also, innerHTML jQuery Function is .html().

How to use Lambda in LINQ select statement

Why not just use all Lambda syntax?

database.Stores.Where(s => s.CompanyID == curCompany.ID)
               .Select(s => new SelectListItem
                       Value = s.Name,
                       Text = s.ID

How do I connect to a specific Wi-Fi network in Android programmatically?

Before connecting WIFI network you need to check security type of the WIFI network ScanResult class has a capabilities. This field gives you type of network


There are three types of WIFI networks.

First, instantiate a WifiConfiguration object and fill in the network’s SSID (note that it has to be enclosed in double quotes), set the initial state to disabled, and specify the network’s priority (numbers around 40 seem to work well).

WifiConfiguration wfc = new WifiConfiguration();

wfc.SSID = "\"".concat(ssid).concat("\"");
wfc.status = WifiConfiguration.Status.DISABLED;
wfc.priority = 40;

Now for the more complicated part: we need to fill several members of WifiConfiguration to specify the network’s security mode. For open networks.


For networks using WEP; note that the WEP key is also enclosed in double quotes.


if (isHexString(password)) wfc.wepKeys[0] = password;
else wfc.wepKeys[0] = "\"".concat(password).concat("\"");
wfc.wepTxKeyIndex = 0;

For networks using WPA and WPA2, we can set the same values for either.


wfc.preSharedKey = "\"".concat(password).concat("\"");

Finally, we can add the network to the WifiManager’s known list

WifiManager wfMgr = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
int networkId = wfMgr.addNetwork(wfc);
if (networkId != -1) {
 // success, can call wfMgr.enableNetwork(networkId, true) to connect

Force SSL/https using .htaccess and mod_rewrite

I'd just like to point out that Apache has the worst inheritance rules when using multiple .htaccess files across directory depths. Two key pitfalls:

  • Only the rules contained in the deepest .htaccess file will be performed by default. You must specify the RewriteOptions InheritDownBefore directive (or similar) to change this. (see question)
  • The pattern is applied to the file path relative to the subdirectory and not the upper directory containing the .htaccess file with the given rule. (see discussion)

This means the suggested global solution on the Apache Wiki does not work if you use any other .htaccess files in subdirectories. I wrote a modified version that does:

RewriteEngine On
# This will enable the Rewrite capabilities

RewriteOptions InheritDownBefore
# This prevents the rule from being overrided by .htaccess files in subdirectories.

RewriteCond %{HTTPS} !=on
# This checks to make sure the connection is not already HTTPS

RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [QSA,R,L]
# This rule will redirect users from their original location, to the same location but using HTTPS.
# i.e. to

Error handling in getJSON calls

Someone give Luciano these points :) I just tested his answer -had a similar question- and worked perfectly...

I even add my 50 cents:

.error(function(jqXHR, textStatus, errorThrown) {
        console.log("error " + textStatus);
        console.log("incoming Text " + jqXHR.responseText);

Regular expression to check if password is "8 characters including 1 uppercase letter, 1 special character, alphanumeric characters"

Best is not using regex for everything. Those requirements are very light. On CPU-wise string operations for checking the criteria/validation is much cheaper and faster than regex!

Oracle SQL escape character (for a '&')

The real answer is you need to set the escape character to '\': SET ESCAPE ON

The problem may have occurred either because escaping was disabled, or the escape character was set to something other than '\'. The above statement will enable escaping and set it to '\'.

None of the other answers previously posted actually answer the original question. They all work around the problem but don't resolve it.

pull out p-values and r-squared from a linear regression

For the final p-value displayed at the end of summary(), the function uses pf() to calculate from the summary(fit)$fstatistic values.

fstat <- summary(fit)$fstatistic
pf(fstat[1], fstat[2], fstat[3], lower.tail=FALSE)

Source: [1], [2]

When should I use a trailing slash in my URL?

The trailing slash does not matter for your root domain or subdomain. Google sees the two as equivalent.

But trailing slashes do matter for everything else because Google sees the two versions (one with a trailing slash and one without) as being different URLs. Conventionally, a trailing slash (/) at the end of a URL meant that the URL was a folder or directory.

A URL without a trailing slash at the end used to mean that the URL was a file.

Read more

Google recommendation class path resource cannot be opened because it does not exist

The file location/path has to relative to your classpath locations. If resources directory is in your classpath you just need "app-context.xml" as file location.

How to remove/ignore :hover css style on touch devices

2020 Solution - CSS only - No Javascript

Use media hover with media pointer will help you guys resolve this issue. Tested on chrome Web and android mobile. I known this old question but I didn't find any solution like this.

@media (hover: hover) and (pointer: fine) {
  a:hover { color: red; }
<a href="#" >Some Link</a>

Configuring ObjectMapper in Spring

To configure a message converter in plain spring-web, in this case to enable the Java 8 JSR-310 JavaTimeModule, you first need to implement WebMvcConfigurer in your @Configuration class and then override the configureMessageConverters method:

public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().modules(new JavaTimeModule(), new Jdk8Module()).build()
            .configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
    converters.add(new MappingJackson2HttpMessageConverter(objectMapper));

Like this you can register any custom defined ObjectMapper in a Java-based Spring configuration.

Accessing elements by type in javascript

In plain-old JavaScript you can do this:

var inputs = document.getElementsByTagName('input');

for(var i = 0; i < inputs.length; i++) {
    if(inputs[i].type.toLowerCase() == 'text') {

In jQuery, you would just do:

// select all inputs of type 'text' on the page

// hide all text inputs which are descendants of div class="foo"
$(" input:text").hide();

Lodash .clone and .cloneDeep behaviors

Thanks to Gruff Bunny and Louis' comments, I found the source of the issue.

As I use Backbone.js too, I loaded a special build of Lodash compatible with Backbone and Underscore that disables some features. In this example:

var clone = _.clone(data, true);

data[1].values.d = 'x';

I just replaced the Underscore build with the Normal build in my Backbone application and the application is still working. So I can now use the Lodash .clone with the expected behaviour.

Edit 2018: the Underscore build doesn't seem to exist anymore. If you are reading this in 2018, you could be interested by this documentation (Backbone and Lodash).

How to get ° character in a string in python?

just use \xb0 (in a string); python will convert it automatically

Turn off warnings and errors on PHP and MySQL

PHP error_reporting reference:

// Turn off all error reporting

// Report simple running errors
error_reporting(E_ERROR | E_WARNING | E_PARSE);

// Reporting E_NOTICE can be good too (to report uninitialized
// variables or catch variable name misspellings ...)
error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE);

// Report all errors except E_NOTICE
// This is the default value set in php.ini
error_reporting(E_ALL ^ E_NOTICE);

// Report all PHP errors (see changelog)

// Report all PHP errors

// Same as error_reporting(E_ALL);
ini_set('error_reporting', E_ALL);

Using GroupBy, Count and Sum in LINQ Lambda Expressions

    var ListByOwner = list.GroupBy(l => l.Owner)
                          .Select(lg => 
                                new { 
                                    Owner = lg.Key, 
                                    Boxes = lg.Count(),
                                    TotalWeight = lg.Sum(w => w.Weight), 
                                    TotalVolume = lg.Sum(w => w.Volume) 

How to return multiple values?

You can do something like this:

public class Example
    public String name;
    public String location;

    public String[] getExample()
        String ar[] = new String[2];
        ar[0]= name;
        ar[1] =  location;
        return ar; //returning two values at once

How to enable curl in Wamp server

Left Click on the WAMP icon the system try -> PHP -> PHP Extensions -> Enable php_curl

How to allow only integers in a textbox?

we can use javascript code

function validateAlphaNumericCode(event) {
    keyEntry = (event.which) ? event.which : event.keyCode

    if (((keyEntry >= '65') && (keyEntry <= '90')) || ((keyEntry >= '97') && (keyEntry <= '122')) || (keyEntry == '37') || (keyEntry == '39') || (keyEntry == '46') || (keyEntry == '8') || (keyEntry == '9') || (keyEntry == '95') || ((keyEntry >= '48') && (keyEntry <= '57')))
        return true;
        return false;

validate this code with your textbox.

package does not exist ; in Android studio 0.8

My solution was creating a project with Use legacy support library option checked. after the project creation is successfully completed, just delete the src folder in the app directory and copy the src folder from your main project. Finally, Sync project with Gradle files.

Installing PG gem on OS X - failure to build native extension

For those who are not interested to use brew.

  1. Download PostgreSQL application.
  2. Follow the macOS default instruction to install it.
  3. It is advisable to run PostgreSQl.
  4. Run gem install pg -- --with-pg-config=/path/to/postgress/in/your/applications/folder/`
    • For example, in my machine it is /Applications/

How to SELECT by MAX(date)?

Workaround but working solution

Only if ID is autoincrement, you can search for the maximum id instead of the max date. So, by the ID you can find all others fields.

select *
from table
where id IN ( 
              select max(id)
              from table
              group by #MY_FIELD#

NuGet auto package restore does not work with MSBuild

If you are using Visual Studio 2017 or later which ships with MSBuild 15 or later, and your .csproj files are in the new PackageReference format, the simplest method is to use the new MSBuild Restore target.

No-one has actually answered the original question, which is "how do I get NuGet packages to auto-restore when building from the command-line with MSBuild?" The answer is: unless you are using the "Enable NuGet package restore" option (which is now deprecated as per this reference), you can't (but see below). If you are trying to do e.g. automated builds on a CI server, this sucks.

However there is a slightly roundabout way to get the desired behaviour:

  1. Download the latest NuGet executable from and place it somewhere in your PATH. (You can do this as a pre-build step.)
  2. Run nuget restore which will auto-download all the missing packages.
  3. Run msbuild to build your solution.

Aside: while the new and recommended way to do auto package restore involves less clutter in your version control, it also makes command-line package restore impossible unless you jump through the extra hoop of downloading and running nuget.exe. Progress?

How can I format DateTime to web UTC format?

This code is working for me:

var datetime = new DateTime(2017, 10, 27, 14, 45, 53, 175, DateTimeKind.Local);
var text = datetime.ToString("o");
--  2017-10-27T14:45:53.1750000+03:00

// datetime from string
var newDate = DateTime.ParseExact(text, "o", null);

How to vertically center a <span> inside a div?

See my article on understanding vertical alignment. There are multiple techniques to accomplish what you want at the end of the discussion.

(Super-short summary: either set the line-height of the child equal to the height of the container, or set positioning on the container and absolutely position the child at top:50% with margin-top:-YYYpx, YYY being half the known height of the child.)

Position last flex item at the end of container

Flexible Box Layout Module - 8.1. Aligning with auto margins

Auto margins on flex items have an effect very similar to auto margins in block flow:

  • During calculations of flex bases and flexible lengths, auto margins are treated as 0.

  • Prior to alignment via justify-content and align-self, any positive free space is distributed to auto margins in that dimension.

Therefore you could use margin-top: auto to distribute the space between the other elements and the last element.

This will position the last element at the bottom.

p:last-of-type {
  margin-top: auto;

.container {
  display: flex;
  flex-direction: column;
  border: 1px solid #000;
  min-height: 200px;
  width: 100px;
p {
  height: 30px;
  background-color: blue;
  margin: 5px;
p:last-of-type {
  margin-top: auto;
<div class="container">

vertical example

Likewise, you can also use margin-left: auto or margin-right: auto for the same alignment horizontally.

p:last-of-type {
  margin-left: auto;

.container {
  display: flex;
  width: 100%;
  border: 1px solid #000;
p {
  height: 50px;
  width: 50px;
  background-color: blue;
  margin: 5px;
p:last-of-type {
  margin-left: auto;
<div class="container">

horizontal example

How do I resolve a TesseractNotFoundError?

You can download tesseract-ocr setup using the following link,

Tesseract for windows

Then add new variable with name tesseract in environment variables with value C:\Program Files (x86)\Tesseract-OCR\tesseract.exe

MongoDB what are the default user and password?

For MongoDB earlier than 2.6, the command to add a root user is addUser (e.g.)


Java - What does "\n" mean?

In the specific case of the code example from the original question, the


is there to move to a new line between incrementing i.

So the first print statement prints all of the elements of Grid[0][j]. When the innermost for loop has completed, the "\n" gets printed and then all of the elements of Grid[1][j] are printed on the next line, and this is repeated until you have a 10x10 grid of the elements of the 2-dimensional array, Grid.

I am getting Failed to load resource: net::ERR_BLOCKED_BY_CLIENT with Google chrome

As other people have mentioned, this issue is common when using adblock or similar extensions.

The source of my issues was my Privacy Badger extension.

Mixing a PHP variable with a string literal


$test = "chees";

It will output:


It is exactly what you are looking for.

Update value of a nested dictionary of varying depth

@FM's answer has the right general idea, i.e. a recursive solution, but somewhat peculiar coding and at least one bug. I'd recommend, instead:

Python 2:

import collections

def update(d, u):
    for k, v in u.iteritems():
        if isinstance(v, collections.Mapping):
            d[k] = update(d.get(k, {}), v)
            d[k] = v
    return d

Python 3:


def update(d, u):
    for k, v in u.items():
        if isinstance(v,
            d[k] = update(d.get(k, {}), v)
            d[k] = v
    return d

The bug shows up when the "update" has a k, v item where v is a dict and k is not originally a key in the dictionary being updated -- @FM's code "skips" this part of the update (because it performs it on an empty new dict which isn't saved or returned anywhere, just lost when the recursive call returns).

My other changes are minor: there is no reason for the if/else construct when .get does the same job faster and cleaner, and isinstance is best applied to abstract base classes (not concrete ones) for generality.