Programs & Examples On #Using directives

The `using` directive, available in several languages including C# and C++, introduces members of a namespace into the current identifier search scope.

The type or namespace cannot be found (are you missing a using directive or an assembly reference?)

This error comes because compile does not know where to find the it occurs mainly when u copy or import item solve this .. 1.change the namespace in the formname.cs and formname.designer.cs to the name of your project .

Why is "using namespace std;" considered bad practice?

The problem with putting using namespace in the header files of your classes is that it forces anyone who wants to use your classes (by including your header files) to also be 'using' (i.e. seeing everything in) those other namespaces.

However, you may feel free to put a using statement in your (private) *.cpp files.

Beware that some people disagree with my saying "feel free" like this -- because although a using statement in a cpp file is better than in a header (because it doesn't affect people who include your header file), they think it's still not good (because depending on the code it could make the implementation of the class more difficult to maintain). This C++ Super-FAQ entry says,

The using-directive exists for legacy C++ code and to ease the transition to namespaces, but you probably shouldn’t use it on a regular basis, at least not in your new C++ code.

The FAQ suggests two alternatives:

  • A using-declaration:

    using std::cout; // a using-declaration lets you use cout without qualification
    cout << "Values:";
  • Just typing std::

    std::cout << "Values:";

The type or namespace name could not be found

I had the same issue. The target frameworks were fine for me. Still it was not working. I installed VS2010 sp1, and did a "Rebuild" on the PrjTest. Then it started working for me.

Setting equal heights for div's with jQuery


        var highestBox = 0;

            if($(this).height() > highestBox){  
                highestBox = $(this).height();  



MS-access reports - The search key was not found in any record - on save

Another potential cause for this error is Sandbox Mode, which prevents MS Access from running certain statements that are considered unsafe. This can be disabled by setting the following registry key...

HKLM\Software\Microsoft\Office\12.0\Access Connectivity Engine\Engines
    SandboxMode (DWORD Value) either 0 or 2:

   0    Sandbox mode is disabled at all times.
   1    Sandbox mode is used for Access, but not for non-Access programs.
   2    Sandbox mode is used for non-Access programs, but not for Access.
   3    Sandbox mode is used at all times. This is the default value.

How to handle onchange event on input type=file in jQuery?

It should work fine, are you wrapping the code in a $(document).ready() call? If not use that or use live i.e.

$('#fileupload1').live('change', function(){ 

Here is a jsFiddle of this working against jQuery 1.4.4

JFrame background image

This is a simple example for adding the background image in a JFrame:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class BackgroundImageJFrame extends JFrame
    JButton b1;
    JLabel l1;

    public BackgroundImageJFrame()
        setTitle("Background Color for JFrame");

        One way
        setLayout(new BorderLayout());
        JLabel background=new JLabel(new ImageIcon("C:\\Users\\Computer\\Downloads\\colorful design.png"));
        background.setLayout(new FlowLayout());
        l1=new JLabel("Here is a button");
        b1=new JButton("I am a button");

        // Another way
        setLayout(new BorderLayout());
        setContentPane(new JLabel(new ImageIcon("C:\\Users\\Computer\\Downloads\\colorful design.png")));
        setLayout(new FlowLayout());
        l1=new JLabel("Here is a button");
        b1=new JButton("I am a button");
        // Just for refresh :) Not optional!

    public static void main(String args[])
        new BackgroundImageJFrame();
  • Click here for more info

How do you programmatically set an attribute?

setattr(x, attr, 'magic')

For help on it:

>>> help(setattr)
Help on built-in function setattr in module __builtin__:

    setattr(object, name, value)

    Set a named attribute on an object; setattr(x, 'y', v) is equivalent to
    ``x.y = v''.

Edit: However, you should note (as pointed out in a comment) that you can't do that to a "pure" instance of object. But it is likely you have a simple subclass of object where it will work fine. I would strongly urge the O.P. to never make instances of object like that.

jQuery if statement, syntax

I little sophisticated way:

$(selector).is(condition)? alert('true') : alert('false');


$("#btn-primary").is(":disabled")? alert('button disabled') : alert('button disabled');

Read Content from Files which are inside Zip file

Sample code you can use to let Tika take care of container files for you.

Form what I can tell, the accepted solution will not work for cases where there are nested zip files. Tika, however will take care of such situations as well.

Check if input value is empty and display an alert

You could create a function that checks every input in an input class like below

 function validateForm() {
    var anyFieldIsEmpty = jQuery(".myclass").filter(function () {
        return $.trim(this.value).length === 0;
    }).length > 0

    if (anyFieldIsEmpty) {
        alert("Fill all the necessary fields");
        var empty = $(".myclass").filter(function () {
            return $.trim(this.value).length === 0;
        empty.css("border", "1px solid red");
        return false;
    } else {
        return true;

What this does is it checks every input in 'myclass' and if empty it gives alert and colour the border of the input and user will recognize which input is not filled.

SQL MERGE statement to update data

SET ed.kWh = ted.kWh
FROM energydata ed
INNER JOIN temp_energydata ted ON ted.webmeterID = ed.webmeterID

$(document).on("click"... not working?

An old post, but I love to share as I have the same case but I finally knew the problem :

Problem is : We make a function to work with specified an HTML element, but the HTML element related to this function is not yet created (because the element was dynamically generated). To make it works, we should make the function at the same time we create the element. Element first than make function related to it.

Simply word, a function will only works to the element that created before it (him). Any elements that created dynamically means after him.

But please inspect this sample that did not heed the above case :

<div class="btn-list" id="selected-country"></div>

Dynamically appended :

<button class="btn-map" data-country="'+country+'">'+ country+' </button>

This function is working good by clicking the button :

$(document).ready(function() {    
        $('#selected-country').on('click','.btn-map', function(){ 
        var datacountry = $(this).data('country'); console.log(datacountry);

or you can use body like :

$('body').on('click','.btn-map', function(){ 
            var datacountry = $(this).data('country'); console.log(datacountry);

compare to this that not working :

$(document).ready(function() {     
$('.btn-map').on("click", function() { 
        var datacountry = $(this).data('country'); alert(datacountry);

hope it will help

Maximum size of a varchar(max) variable

EDIT: After further investigation, my original assumption that this was an anomaly (bug?) of the declare @var datatype = value syntax is incorrect.

I modified your script for 2005 since that syntax is not supported, then tried the modified version on 2008. In 2005, I get the Attempting to grow LOB beyond maximum allowed size of 2147483647 bytes. error message. In 2008, the modified script is still successful.

declare @KMsg varchar(max); set @KMsg = REPLICATE('a',1024);
declare @MMsg varchar(max); set @MMsg = REPLICATE(@KMsg,1024);
declare @GMsg varchar(max); set @GMsg = REPLICATE(@MMsg,1024);
declare @GGMMsg varchar(max); set @GGMMsg = @GMsg + @GMsg + @MMsg;
select LEN(@GGMMsg)

Where does Vagrant download its .box files to?

In addition to



You have to delete the files in VirtualBox/OtherVMprovider to make a clean start.

How do I show a console output/window in a forms application?

using System;
using System.Runtime.InteropServices;

namespace SomeProject
    class GuiRedirect
    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern bool AttachConsole(int dwProcessId);
    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern IntPtr GetStdHandle(StandardHandle nStdHandle);
    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern bool SetStdHandle(StandardHandle nStdHandle, IntPtr handle);
    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern FileType GetFileType(IntPtr handle);

    private enum StandardHandle : uint
        Input = unchecked((uint)-10),
        Output = unchecked((uint)-11),
        Error = unchecked((uint)-12)

    private enum FileType : uint
        Unknown = 0x0000,
        Disk = 0x0001,
        Char = 0x0002,
        Pipe = 0x0003

    private static bool IsRedirected(IntPtr handle)
        FileType fileType = GetFileType(handle);

        return (fileType == FileType.Disk) || (fileType == FileType.Pipe);

    public static void Redirect()
        if (IsRedirected(GetStdHandle(StandardHandle.Output)))
            var initialiseOut = Console.Out;

        bool errorRedirected = IsRedirected(GetStdHandle(StandardHandle.Error));
        if (errorRedirected)
            var initialiseError = Console.Error;


        if (!errorRedirected)
            SetStdHandle(StandardHandle.Error, GetStdHandle(StandardHandle.Output));

Convert char to int in C#

This converts to an integer and handles unicode


You can read more here.

Select Tag Helper in ASP.NET Core MVC

You can also use IHtmlHelper.GetEnumSelectList.

    // Summary:
    //     Returns a select list for the given TEnum.
    // Type parameters:
    //   TEnum:
    //     Type to generate a select list for.
    // Returns:
    //     An System.Collections.Generic.IEnumerable`1 containing the select list for the
    //     given TEnum.
    // Exceptions:
    //   T:System.ArgumentException:
    //     Thrown if TEnum is not an System.Enum or if it has a System.FlagsAttribute.
    IEnumerable<SelectListItem> GetEnumSelectList<TEnum>() where TEnum : struct;

Convert Datetime column from UTC to local time in select statement

This can be done without a function. Code below will convert a UTC time to Mountain time accounting for daylight savings. Adjust all the -6 and -7 numbers to your timezone accordingly (i.e. for EST you would adjust to -4 and -5 respectively)

--Adjust a UTC value, in the example the UTC field is identified as UTC.Field, to account for daylight savings time when converting out of UTC to Mountain time.
    --When it's between March and November, it is summer time which is -6 from UTC
    WHEN MONTH ( UTC.Field ) > 3 AND MONTH ( UTC.Field ) < 11 
        THEN DATEADD ( HOUR , -6 , UTC.Field )
    --When its March and the day is greater than the 14, you know it's summer (-6)
    WHEN MONTH ( UTC.Field ) = 3
        AND DATEPART ( DAY , UTC.Field ) >= 14 
            --However, if UTC is before 9am on that Sunday, then it's before 2am Mountain which means it's still Winter daylight time.
                WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1 
                    AND UTC.Field < '9:00'
                    --Before 2am mountain time so it's winter, -7 hours for Winter daylight time
                    THEN DATEADD ( HOUR , -7 , UTC.Field )
                --Otherwise -6 because it'll be after 2am making it Summer daylight time
                ELSE DATEADD ( HOUR , -6 , UTC.Field )
    WHEN MONTH ( UTC.Field ) = 3
        AND ( DATEPART ( WEEKDAY , UTC.Field ) + 7 ) <= DATEPART ( day , UTC.Field ) 
            --According to the date, it's moved onto Summer daylight, but we need to account for the hours leading up to 2am if it's Sunday
                WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1 
                    AND UTC.Field < '9:00'
                    --Before 9am UTC is before 2am Mountain so it's winter Daylight, -7 hours
                    THEN DATEADD ( HOUR , -7 , UTC.Field )
                --Otherwise, it's summer daylight, -6 hours
                ELSE DATEADD ( HOUR , -6 , UTC.Field )
    --When it's November and the weekday is greater than the calendar date, it's still Summer so -6 from the time
    WHEN MONTH ( UTC.Field ) = 11
        AND DATEPART ( WEEKDAY , UTC.Field ) > DATEPART ( DAY , UTC.Field ) 
        THEN DATEADD ( HOUR , -6 , UTC.Field )
    WHEN MONTH ( UTC.Field ) = 11
        AND DATEPART ( WEEKDAY , UTC.Field ) <= DATEPART ( DAY , UTC.Field ) 
            --If the weekday is less than or equal to the calendar day it's Winter daylight but we need to account for the hours leading up to 2am.
                WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1 
                    AND UTC.Field < '8:00'
                    --If it's before 8am UTC and it's Sunday in the logic outlined, then it's still Summer daylight, -6 hours
                    THEN DATEADD ( HOUR , -6 , UTC.Field )
                --Otherwise, adjust for Winter daylight at -7
                ELSE DATEADD ( HOUR , -7 , UTC.Field )
    --If the date doesn't fall into any of the above logic, it's Winter daylight, -7
        DATEADD ( HOUR , -7 , UTC.Field )

..The underlying connection was closed: An unexpected error occurred on a receive

  • .NET 4.6 and above. You don’t need to do any additional work to support TLS 1.2, it’s supported by default.
  • .NET 4.5. TLS 1.2 is supported, but it’s not a default protocol. You need to opt-in to use it. The following code will make TLS 1.2 default, make sure to execute it before making a connection to secured resource:
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

  • .NET 4.0. TLS 1.2 is not supported, but if you have .NET 4.5 (or above) installed on the system then you still can opt in for TLS 1.2 even if your application framework doesn’t support it. The only problem is that SecurityProtocolType in .NET 4.0 doesn’t have an entry for TLS1.2, so we’d have to use a numerical representation of this enum value:
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

  • .NET 3.5 or below. TLS 1.2 is not supported. Upgrade your application to more recent version of the framework.

How to maintain state after a page refresh in React.js?

I may be late but actual code for react-create-app for react > 16 ver. After each change state is saved in sessionStorage (not localStorage) and is crypted via crypto-js. On refresh (when user demands refresh of the page by clicking refresh button) state is loaded from the storage. I also recommend not to use sourceMaps in build to avoid readablility of the key phrases.

my index.js

import React from "react";
import ReactDOM from "react-dom";
import './index.css';
import App from './containers/App';
import * as serviceWorker from './serviceWorker';
import {createStore} from "redux";
import {Provider} from "react-redux"
import {BrowserRouter} from "react-router-dom";
import rootReducer from "./reducers/rootReducer";
import CryptoJS from 'crypto-js';

const key = CryptoJS.enc.Utf8.parse("someRandomText_encryptionPhase");
const iv = CryptoJS.enc.Utf8.parse("someRandomIV");
const persistedState = loadFromSessionStorage();

let store = createStore(rootReducer, persistedState,

function loadFromSessionStorage() {
    try {
        const serializedState = sessionStorage.getItem('state');
        if (serializedState === null) {
            return undefined;
        const decrypted = CryptoJS.AES.decrypt(serializedState, key, {iv: iv}).toString(CryptoJS.enc.Utf8);
        return JSON.parse(decrypted);
    } catch {
        return undefined;

function saveToSessionStorage(state) {
        try {
            const serializedState = JSON.stringify(state);
            const encrypted = CryptoJS.AES.encrypt(serializedState, key, {iv: iv});
            sessionStorage.setItem('state', encrypted)
        } catch (e) {

        <Provider store={store}>

store.subscribe(() => saveToSessionStorage(store.getState()));


Access iframe elements in JavaScript

Make sure your iframe is already loaded. Old but reliable way without jQuery:

<iframe src="" id="iframe" onload="access()"></iframe>

function access() {
   var iframe = document.getElementById("iframe");
   var innerDoc = iframe.contentDocument || iframe.contentWindow.document;

CASE (Contains) rather than equal statement

CASE WHEN ', ' + dbo.Table.Column +',' LIKE '%, lactulose,%' 
  THEN 'BP Medication' ELSE '' END AS [BP Medication]

The leading ', ' and trailing ',' are added so that you can handle the match regardless of where it is in the string (first entry, last entry, or anywhere in between).

That said, why are you storing data you want to search on as a comma-separated string? This violates all kinds of forms and best practices. You should consider normalizing your schema.

In addition: don't use 'single quotes' as identifier delimiters; this syntax is deprecated. Use [square brackets] (preferred) or "double quotes" if you must. See "string literals as column aliases" here:

EDIT If you have multiple values, you can do this (you can't short-hand this with the other CASE syntax variant or by using something like IN()):

  WHEN ', ' + dbo.Table.Column +',' LIKE '%, lactulose,%' 
  WHEN ', ' + dbo.Table.Column +',' LIKE '%, amlodipine,%' 
  THEN 'BP Medication' ELSE '' END AS [BP Medication]

If you have more values, it might be worthwhile to use a split function, e.g.

USE tempdb;

       ( SELECT Item = x.i.value('(./text())[1]', 'nvarchar(max)')
         FROM ( SELECT [XML] = CONVERT(XML, '<i>'
         + REPLACE(@List,',', '</i><i>') + '</i>').query('.')
           ) AS a CROSS APPLY [XML].nodes('i') AS x(i) ) AS y

CREATE TABLE dbo.[Table](ID INT, [Column] VARCHAR(255));

(1,'lactulose, Lasix (furosemide), oxazepam, propranolol, rabeprazole, sertraline,'),
(2,'lactulite, Lasix (furosemide), lactulose, propranolol, rabeprazole, sertraline,'),
(3,'lactulite, Lasix (furosemide), oxazepam, propranolol, rabeprazole, sertraline,'),
(4,'lactulite, Lasix (furosemide), lactulose, amlodipine, rabeprazole, sertraline,');

  FROM dbo.[Table] AS t
  INNER JOIN dbo.SplitStrings('lactulose,amlodipine') AS s
  ON ', ' + t.[Column] + ',' LIKE '%, ' + s.Item + ',%'



Print array to a file

I just wrote this function to output an array as text:

Should output nicely formatted array.


Beware of user input.

This script was created for internal use.

If you intend to use this for public use you will need to add some additional data validation to prevent script injection.

This is not fool proof and should be used with trusted data only.

The following function will output something like:

$var = array(
  'primarykey' => array(
    'test' => array(
      'var' => array(
        1 => 99,
        2 => 500,
    'abc' => 'd',

here is the function (note: function is currently formatted for oop implementation.)

  public function outArray($array, $lvl=0){
    $sub = $lvl+1;
    $return = "";
      $return = "\t\$var = array(\n";  
      foreach($array as $key => $mixed){
        $key = trim($key);
          $mixed = trim($mixed);
        if(empty($key) && empty($mixed)){continue;}
        if(!is_numeric($key) && !empty($key)){
          if($key == "[]"){
            $key = null;
          } else {
            $key = "'".addslashes($key)."'";

        if($mixed === null){
          $mixed = 'null';
        } elseif($mixed === false){
          $mixed = 'false';
        } elseif($mixed === true){
          $mixed = 'true';
        } elseif($mixed === ""){
          $mixed = "''";

        //CONVERT STRINGS 'true', 'false' and 'null' TO true, false and null
        //uncomment if needed
        //elseif(!is_numeric($mixed) && !is_array($mixed) && !empty($mixed)){
        //  if($mixed != 'false' && $mixed != 'true' && $mixed != 'null'){
        //    $mixed = "'".addslashes($mixed)."'";
        //  }

          if($key !== null){
            $return .= "\t".str_repeat("\t", $sub)."$key => array(\n";
            $return .= $this->outArray($mixed, $sub);
            $return .= "\t".str_repeat("\t", $sub)."),\n";
          } else {
            $return .= "\t".str_repeat("\t", $sub)."array(\n";
            $return .= $this->outArray($mixed, $sub);
            $return .= "\t".str_repeat("\t", $sub)."),\n";            
        } else {
          if($key !== null){
            $return .= "\t".str_repeat("\t", $sub)."$key => $mixed,\n";
          } else {
            $return .= "\t".str_repeat("\t", $sub).$mixed.",\n";
      $return .= "\t);\n";
    return $return;

Alternately you can use this script I also wrote a while ago:

This one is nice to copy and paste parts of an array.

( Would be near impossible to do that with serialized output )

Not the cleanest function but it gets the job done.

This one will output as follows:

$array['key']['key2'] = 'value';
$array['key']['key3'] = 'value2';
$array['x'] = 7;
$array['y']['z'] = 'abc';

Also take care for user input. Here is the code.

public static function prArray($array, $path=false, $top=true) {
    $data = "";
    $delimiter = "~~|~~";
    $p = null;
      foreach($array as $key => $a){
        if(!is_array($a) || empty($a)){
            $data .= $path."['{$key}'] = array();".$delimiter;
          } else {
            $data .= $path."['{$key}'] = \"".htmlentities(addslashes($a))."\";".$delimiter;
        } else {
          $data .= self::prArray($a, $path."['{$key}']", false);
      $return = "";
      foreach(explode($delimiter, $data) as $value){
          $return .= '$array'.$value."<br>";
      echo $return;
    return $data;

Check if key exists and iterate the JSON array using Python

I wrote a tiny function for this purpose. Feel free to repurpose,

def is_json_key_present(json, key):
        buf = json[key]
    except KeyError:
        return False

    return True

Total Number of Row Resultset getRow Method

BalusC's answer is right! but I have to mention according to the user instance variable such as:

total = rSet.getRow();

and then which you are missing


the remaining code is same you will get your desire result.

How to compare values which may both be null in T-SQL

You create a primary key on your fields and let the engine enforce the uniqueness. Doing IF EXISTS logic is incorrect anyway as is flawed with race conditions.

How do I read CSV data into a record array in NumPy?

In [329]: %time my_data = genfromtxt('one.csv', delimiter=',')
CPU times: user 19.8 s, sys: 4.58 s, total: 24.4 s
Wall time: 24.4 s

In [330]: %time df = pd.read_csv("one.csv", skiprows=20)
CPU times: user 1.06 s, sys: 312 ms, total: 1.38 s
Wall time: 1.38 s

Execute a file with arguments in Python shell

Actually, wouldn't we want to do this?

import sys
sys.argv = ['','arg1', 'arg2']

jQuery removing '-' character from string

$mylabel.text( $mylabel.text().replace('-', '') );

Since text() gets the value, and text( "someValue" ) sets the value, you just place one inside the other.

Would be the equivalent of doing:

var newValue = $mylabel.text().replace('-', '');
$mylabel.text( newValue );


I hope I understood the question correctly. I'm assuming $mylabel is referencing a DOM element in a jQuery object, and the string is in the content of the element.

If the string is in some other variable not part of the DOM, then you would likely want to call the .replace() function against that variable before you insert it into the DOM.

Like this:

var someVariable = "-123456";
$mylabel.text( someVariable.replace('-', '') );

or a more verbose version:

var someVariable = "-123456";
someVariable = someVariable.replace('-', '');
$mylabel.text( someVariable );

SQL Server find and replace specific word in all rows of specific column

You can also export the database and then use a program like notepad++ to replace words and then inmport aigain.

Link to add to Google calendar

I've also been successful with this URL structure:

Base URL:

And let's say this is my event details:

Title: Event Title
Description: Example of some description. See more at
Location: 123 Some Place
Date: February 22, 2020
Start Time: 10:00am
End Time: 11:30am
Timezone: America/New York (GMT -5)

I'd convert my details into these parameters (URL encoded):


Example link:

Please note that since I've specified a timezone with the "ctz" parameter, I used the local times for the start and end dates. Alternatively, you can use UTC dates and exclude the timezone parameter, like this:


Example link:

Bootstrap 3 Flush footer to bottom. not fixed

Or this

<footer class="navbar navbar-default navbar-fixed-bottom">
    <p class="text-muted" align="center">This is a footer</p>

Superscript in Python plots

You just need to have the full expression inside the $. Basically, you need "meters $10^1$". You don't need usetex=True to do this (or most any mathematical formula).

You may also want to use a raw string (e.g. r"\t", vs "\t") to avoid problems with things like \n, \a, \b, \t, \f, etc.

For example:

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.set(title=r'This is an expression $e^{\sin(\omega\phi)}$',
       xlabel='meters $10^1$', ylabel=r'Hertz $(\frac{1}{s})$')

enter image description here

If you don't want the superscripted text to be in a different font than the rest of the text, use \mathregular (or equivalently \mathdefault). Some symbols won't be available, but most will. This is especially useful for simple superscripts like yours, where you want the expression to blend in with the rest of the text.

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.set(title=r'This is an expression $\mathregular{e^{\sin(\omega\phi)}}$',
       xlabel='meters $\mathregular{10^1}$',
       ylabel=r'Hertz $\mathregular{(\frac{1}{s})}$')

enter image description here

For more information (and a general overview of matplotlib's "mathtext"), see:

How to retrieve the dimensions of a view?

I'll just add an alternative solution, override your activity's onWindowFocusChanged method and you will be able to get the values of getHeight(), getWidth() from there.

public void onWindowFocusChanged (boolean hasFocus) {
        // the height will be set at this point
        int height = myEverySoTallView.getMeasuredHeight(); 

How to access local files of the filesystem in the Android emulator?

In Android Studio 3.0 and later do this:

View > Tool Windows > Device File Explorer

Replace substring with another substring C++

There is no one built-in function in C++ to do this. If you'd like to replace all instances of one substring with another, you can do so by intermixing calls to string::find and string::replace. For example:

size_t index = 0;
while (true) {
     /* Locate the substring to replace. */
     index = str.find("abc", index);
     if (index == std::string::npos) break;

     /* Make the replacement. */
     str.replace(index, 3, "def");

     /* Advance index forward so the next iteration doesn't pick it up as well. */
     index += 3;

In the last line of this code, I've incremented index by the length of the string that's been inserted into the string. In this particular example - replacing "abc" with "def" - this is not actually necessary. However, in a more general setting, it is important to skip over the string that's just been replaced. For example, if you want to replace "abc" with "abcabc", without skipping over the newly-replaced string segment, this code would continuously replace parts of the newly-replaced strings until memory was exhausted. Independently, it might be slightly faster to skip past those new characters anyway, since doing so saves some time and effort by the string::find function.

Hope this helps!

filtering a list using LINQ

var filtered = projects;
foreach (var tag in filteredTags) {
  filtered = filtered.Where(p => p.Tags.Contains(tag))

The nice thing with this approach is that you can refine search results incrementally.

How to dynamically create generic C# object using reflection?

I know this question is resolved but, for the benefit of anyone else reading it; if you have all of the types involved as strings, you could do this as a one liner:

IYourInterface o = (Activator.CreateInstance(Type.GetType("Namespace.TaskA`1[OtherNamespace.TypeParam]") as IYourInterface);

Whenever I've done this kind of thing, I've had an interface which I wanted subsequent code to utilise, so I've casted the created instance to an interface.

How to compare two dates to find time difference in SQL Server 2005, date manipulation

Declare the Start and End date DECLARE @SDATE AS DATETIME

DECLARE @END_-- Set Start and End date

-- Get the Result in HH:MI:SS:MMM(24H) format SELECT CONVERT(VARCHAR(12), DATEADD(MS, DATEDIFF(MS, @START_DATE, @END_DATE), 0), 114) AS TimeDiff

Selenium IDE - Command to wait for 5 seconds

Before the command clickAndWait add the following code so the script will wait until the specific link to be visible:

        <td>link=do something</td>

The practice of using the wait commands instead of pause is most of the times more efficient and more stable.

XAMPP Apache won't start

i had the same problem but after i went into the readme, i realised that i didn't have Microsoft Visual C++ 2008 Redistributable installed. after i instaled it, all worked just fine

How to call Makefile from another Makefile?

I'm not really too clear what you are asking, but using the -f command line option just specifies a file - it doesn't tell make to change directories. If you want to do the work in another directory, you need to cd to the directory:

    cd gtest-1.4.0 && $(MAKE) clean

Note that each line in Makefile runs in a separate shell, so there is no need to change the directory back.

auto run a bat script in windows 7 at login

To run the batch file when the VM user logs in:

Drag the shortcut--the one that's currently on your desktop--(or the batch file itself) to Start - All Programs - Startup. Now when you login as that user, it will launch the batch file.

Another way to do the same thing is to save the shortcut or the batch file in %AppData%\Microsoft\Windows\Start Menu\Programs\Startup\.

As far as getting it to run full screen, it depends a bit what you mean. You can have it launch maximized by editing your batch file like this:

start "" /max "C:\Program Files\Oracle\VirtualBox\VirtualBox.exe" --comment "VM" --startvm "12dada4d-9cfd-4aa7-8353-20b4e455b3fa"

But if VirtualBox has a truly full-screen mode (where it hides even the taskbar), you'll have to look for a command-line parameter on VirtualBox.exe. I'm not familiar with that product.

How do I get bit-by-bit data from an integer value in C?

Here's one way to do it—there are many others:

bool b[4];
int v = 7;  // number to dissect

for (int j = 0;  j < 4;  ++j)
   b [j] =  0 != (v & (1 << j));

It is hard to understand why use of a loop is not desired, but it is easy enough to unroll the loop:

bool b[4];
int v = 7;  // number to dissect

b [0] =  0 != (v & (1 << 0));
b [1] =  0 != (v & (1 << 1));
b [2] =  0 != (v & (1 << 2));
b [3] =  0 != (v & (1 << 3));

Or evaluating constant expressions in the last four statements:

b [0] =  0 != (v & 1);
b [1] =  0 != (v & 2);
b [2] =  0 != (v & 4);
b [3] =  0 != (v & 8);

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!

Compare a string using sh shell

-eq is a mathematical comparison operator. I've never used it for string comparison, relying on == and != for compares.

if [ 'XYZ' == 'ABC' ]; then   # Double equal to will work in Linux but not on HPUX boxes it should be if [ 'XYZ' = 'ABC' ] which will work on both
  echo "Match"
  echo "No Match"

Auto insert date and time in form input field?

It sounds like you are going to be storing the value that input field contains after the form is submitted, which means you are using a scripting language. I would use it instead of JavaScript as most scripting languages have better time/date formatting options. In PHP you could do something like this:

<input id="date" name="date" value="<?php echo date("M j, Y - g:i"); ?>"/>

Which would fill the field with "Jun 16, 2009 - 8:58"

What is a web service endpoint?

In past projects I worked on, the endpoint was a relative property. That is to say it may or may not have been appended to, but it always contained the protocol://host:port/partOfThePath.

If the service being called had a dynamic part to it, for example a ?param=dynamicValue, then that part would get added to the endpoint. But many times the endpoint could be used as is without having to be amended.

Whats important to understand is what an endpoint is not and how it helps. For example an alternative way to pass the information stored in an endpoint would be to store the different parts of the endpoint in separate properties. For example:


Or if the same host and port across multiple services:


In those cases the full URL would need to be constructed in your code as such:

String url = "http://" + host + ":" + port + pathForServiceA  + "?" + dynamicParam + "=" + dynamicValue;

In contract this can be stored as an endpoint as such


And yes many times we stored the endpoint up to and including the '='. This lead to code like this:

String url = serviceAEndpoint + dynamicValue;

Hope that sheds some light.

Fixing npm path in Windows 8 and 10

Installed Node Version Manager (NVM) for Windows:

I'm using Windows 10 - 64 bit so I run... Commands:

  • nvm arch 64 (to make default the 64 bit executable)
  • nvm list (to list all available node versions)
  • nvm install 8.0.0 (to download node version 8.0.0 - you can pick any)
  • nvm use 8.0.0 (to use that specific version)

In my case I had to just switch to version 8.5.0 and then switch back again to 8.0.0 and it was fixed. Apparently NVM sets the PATH variables whenever you do that switch.

How to install PyQt5 on Windows?

First try this in your Windows cmd window:

pip3 install pyqt5

If that is successful, it will look something like this:

C:\Windows\System32>pip3 install pyqt5
Collecting pyqt5
  Downloading PyQt5-5.9-5.9.1-cp35.cp36.cp37-none-win_amd64.whl (77.2MB)
    100% |################################| 77.2MB 13kB/s
Collecting sip<4.20,>=4.19.3 (from pyqt5)
  Downloading sip-4.19.3-cp35-none-win_amd64.whl (49kB)
    100% |################################| 51kB 984kB/s
Installing collected packages: sip, pyqt5
Successfully installed pyqt5-5.9 sip-4.19.3

If that did not work, you might try this link from SourceForge.

PyQt5 .exe installers for Windows

How to find the installer that's right for you?

First, determine what version of Python you have and whether you have 32-bit or 64-bit Python. Next, open one of the directories. I'm on Python 3.5 64-bit so I'm looking for a .exe with those specs. When you open a directory on SourceForge, you will see some directories with ONLY .zip or .tar.gz. That's not what you're looking for. A good indication of which directory you should click is given by the "Downloads/Week" column. I'll open the PyQt-5.6 directory in my case.

Here we notice some .exe files:


I know these are Python 3.5 by Py3.5 in the file name. I am also looking for the 64-bit version so I'll download PyQt5-5.6-gpl-Py3.5-Qt5.6.0-x64-2.exe. Final answer!

Note: if you try to install a version that's not compatible with your system, a dialog box will appear immediately after running the .exe. That's an indication that you've chosen the wrong one. I'm not trying to sound like a dbag... I did that several times!

To test a successful install, in your Python interpreter, try to import:

from PyQt5 import QtCore, QtGui, QtWidgets

How to format dateTime in django template?

{{ wpis.entry.lastChangeDate|date:"SHORT_DATETIME_FORMAT" }}

How can I delete one element from an array by value

Compiling all the different options for delete in ruby

delete - Deletes matching elements by value. If more than one value matches it will remove all. If you don't care about the number of occurrence or sure about single occurrence, use this method.

a = [2, 6, 3, 5, 3, 7]
a.delete(3)  # returns 3
puts a       # return [2, 6, 5, 7]

delete_at - Deletes element at given index. If you know the index use this method.

# continuing from the above example
a.delete_at(2) # returns 5
puts a         # returns [2, 6, 7]

delete_if - Deletes every element for which block is true. This will modify the array. Array changes instantly as the block is called.

b = [1, 2, 5, 4, 9, 10, 11]
b.delete_if {|n| n >= 10}.  # returns [1, 2, 5, 4, 9]

reject - This will return new array with the elements for which the given block is false. The ordering is maintained with this.

c = [1, 2, 5, 4, 9, 10, 11]
c.reject {|n| n >= 10}.  # returns [1, 2, 5, 4, 9]

reject! - same as delete_if. Array may not change instantly as the block is called.

If you want to delete multiple values from array, the best option is as bellow.

a = [2, 3, 7, 4, 6, 21, 13]
b = [7, 21]
a = a - b    # a - [2, 3, 4, 6, 13]

How to use nan and inf in C?


/* IEEE positive infinity.  */

#if __GNUC_PREREQ(3,3)
# define INFINITY   (__builtin_inff())


#ifndef _MATH_H
# error "Never use <bits/nan.h> directly; include <math.h> instead."

/* IEEE Not A Number.  */

#if __GNUC_PREREQ(3,3)

# define NAN    (__builtin_nanf (""))

#elif defined __GNUC__

# define NAN \
  (__extension__                                  \
   ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
    { __l: 0x7fc00000UL }).__d)


# include <endian.h>

#  define __nan_bytes       { 0x7f, 0xc0, 0, 0 }
# endif
#  define __nan_bytes       { 0, 0, 0xc0, 0x7f }
# endif

static union { unsigned char __c[4]; float __d; } __nan_union
    __attribute_used__ = { __nan_bytes };
# define NAN    (__nan_union.__d)

#endif  /* GCC.  */

How to use classes from .jar files?

You need to put the .jar file into your classpath when compiling/running your code. Then you just use standard imports of the classes in the .jar.

Pad a string with leading zeros so it's 3 characters long in SQL Server 2008

I have always found the following method to be very helpful.

REPLICATE('0', 5 - LEN(Job.Number)) + CAST(Job.Number AS varchar) as 'NumberFull'

Difference between Interceptor and Filter in Spring MVC

Filter: - A filter as the name suggests is a Java class executed by the servlet container for each incoming HTTP request and for each http response. This way, is possible to manage HTTP incoming requests before them reach the resource, such as a JSP page, a servlet or a simple static page; in the same way is possible to manage HTTP outbound response after resource execution.

Interceptor: - Spring Interceptors are similar to Servlet Filters but they acts in Spring Context so are many powerful to manage HTTP Request and Response but they can implement more sophisticated behavior because can access to all Spring context.

Difference between DOM parentNode and parentElement

Just like with nextSibling and nextElementSibling, just remember that, properties with "element" in their name always returns Element or null. Properties without can return any other kind of node.

console.log(document.body.parentNode, "is body's parent node");    // returns <html>
console.log(document.body.parentElement, "is body's parent element"); // returns <html>

var html = document.body.parentElement;
console.log(html.parentNode, "is html's parent node"); // returns document
console.log(html.parentElement, "is html's parent element"); // returns null

Why not use Double or Float to represent currency?

I'll risk being downvoted, but I think the unsuitability of floating point numbers for currency calculations is overrated. As long as you make sure you do the cent-rounding correctly and have enough significant digits to work with in order to counter the binary-decimal representation mismatch explained by zneak, there will be no problem.

People calculating with currency in Excel have always used double precision floats (there is no currency type in Excel) and I have yet to see anyone complaining about rounding errors.

Of course, you have to stay within reason; e.g. a simple webshop would probably never experience any problem with double precision floats, but if you do e.g. accounting or anything else that requires adding a large (unrestricted) amount of numbers, you wouldn't want to touch floating point numbers with a ten foot pole.

Pretty print in MongoDB shell as default

Oh so i guess .pretty() is equal to:


Map vs Object in JavaScript

One aspect of the Map that is not given much press here is lookup. According to the spec:

A Map object must be implemented using either hash tables or other mechanisms that, on average, provide access times that are sublinear on the number of elements in the collection. The data structures used in this Map objects specification is only intended to describe the required observable semantics of Map objects. It is not intended to be a viable implementation model.

For collections that have a huge number of items and require item lookups, this is a huge performance boost.

TL;DR - Object lookup is not specified, so it can be on order of the number of elements in the object, i.e., O(n). Map lookup must use a hash table or similar, so Map lookup is the same regardless of Map size, i.e. O(1).

How to display activity indicator in middle of the iphone screen?

If you want to center the spinner using AutoLayout, do:

UIActivityIndicatorView *activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
[activityView startAnimating];
[self.view addSubview:activityView];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:activityView
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:activityView

Spring Boot and how to configure connection details to MongoDB?

Just to quote Boot Docs:

You can set property to change the url, or alternatively specify a host/port. For example, you might declare the following in your

All available options for prefix are fields of MongoProperties:

private String host;

private int port = DBPort.PORT;

private String uri = "mongodb://localhost/test";

private String database;

private String gridFsDatabase;

private String username;

private char[] password;

How do I make Git use the editor of my choice for commits?

For Windows, Neovim:

# .gitconfig


More than one file was found with OS independent path 'META-INF/LICENSE'




to worked for me.

Android canvas draw rectangle

Don't know if this is too late, but the way I solved this was to draw four thin rectangles that together made up a one big border. Drawing the border with one rectangle seems to be undoable since they're all opaque, so you should draw each edge of the border separately.

Getting full-size profile picture

found a way:

$albums = $facebook->api('/' . $user_id . '/albums');
foreach($albums['data'] as $album){
    if ($album['name'] == "Profile Pictures"){
        $photos = $facebook->api('/' . $album['id'] . '/photos');
        $profile_pic = $photos['data'][0]['source'];

batch file to check 64bit or 32bit OS


Will appear on Win32, and


will appear for Win64.

If you are perversely running the 32-bit cmd.exe process then Windows presents two environment variables:


Best way to compare dates in Android

SimpleDateFormat sdf=new SimpleDateFormat("d/MM/yyyy");
Date date=null;
Date date1=null;
try {
    }  catch (ParseException e) {
if (date1.after(date) && date1.equals(date)) {
// your work..//

Using gradle to find dependency tree

Things have moved forward in Gradle so I believe this question merits another answer.
Since Gradle 4.3, "build scans" were introduced. All relevant info is available in the Gradle docs (1, 2). For me, this seems to now be the easiest way to check your dependencies (and generally your build) in a clear, organized way.

They are very easy to create, just execute:

gradle build --scan  

(or ./gradlew build --scan if you use a wrapper)

This produces a randomly generated link where you can see your scan. When opening that link, you enter your email and gain full control of the link: eg. share it or delete it. It has got a lot of info about your build, not just dependencies. You can see your dependencies, their hierarchies, the repository used to obtain them but also a lot of other stuff about your build, namely, its performance (which is of interest in big complex builds), your tests, even your console output and your system configuration, which JDK and JVM was used, max heap size etc.

This is a printscreen from a mock project:

Build scan example

A build scan is a shareable record of a build that provides insights into what happened and why. You can create a build scan at for free.

Note however, that info for your build process will be sent to the Gradle servers. You have full control to delete it when you are finished with your inspection.

Finally, you can use build scans with Gradle versions earlier than 4.3 too, you just have to manually add the scans plugin in your buildscript.

Incorporating some feedback from the comments some extra notes:
1) It is very difficult to do this by mistake or without understanding that some info for your build will be online (private to you, with the ability to delete it, but still online).

When executing gradle build --scan the following message appears:

Publishing a build scan to requires accepting the Gradle
Terms of Service defined at Do you
accept these terms? [yes, no]

You have to explicitly write yes and then the message continues:

Publishing build scan...

2) In Gradle Enterprise you can host gradle build scans in your own servers. However I have no experience in this and my proposed approach was about the standard Gradle distribution, using Gradle's servers for your build scans.

3) Gradle itself promotes the build scans as the way to deal with most your build problems.

Re-doing a reverted merge in Git

I would suggest you to follow below steps to revert a revert, say SHA1.

git checkout develop #go to develop branch
git pull             #get the latest from remote/develop branch
git branch users/yourname/revertOfSHA1 #having HEAD referring to develop
git checkout users/yourname/revertOfSHA1 #checkout the newly created branch
git log --oneline --graph --decorate #find the SHA of the revert in the history, say SHA1
git revert SHA1
git push --set-upstream origin users/yourname/revertOfSHA1 #push the changes to remote

Now create PR for the branch users/yourname/revertOfSHA1

Android, ListView IllegalStateException: "The content of the adapter has changed but ListView did not receive a notification"

I faced a similar problem, here's how I solved in my case. I verify if the task already is RUNNING or FINISHED because an task can run only once. Below you will see a partial and adapted code from my solution.

public class MyActivity... {
    private MyTask task;

    protected void onCreate(Bundle savedInstanceState) {
       // your code
       task = new MyTask();

    private void setList() {
    if (task != null)
        if (task.getStatus().equals(AsyncTask.Status.RUNNING)){
            task = new MyTask();
        } else if (task.getStatus().equals(AsyncTask.Status.FINISHED)) {
            task = new MyTask();
        } else 

    class MyTask extends AsyncTask<Void, Item, Void>{
       List<Item> Itens;

       protected void onPreExecute() {

        //your code

        adapterItem= new MyListAdapter(MyActivity.this, R.layout.item, new ArrayList<Item>());


    protected Void doInBackground(Void... params) {

        Itens = getItens();
        for (Item item : Itens) {
            publishProgress(item );

        return null;

    protected void onProgressUpdate(Item ... item ) {           

    protected void onPostExecute(Void result) {
        //your code



arranging div one below the other

The default behaviour of divs is to take the full width available in their parent container.
This is the same as if you'd give the inner divs a width of 100%.

By floating the divs, they ignore their default and size their width to fit the content. Everything behind it (in the HTML), is placed under the div (on the rendered page).
This is the reason that they align theirselves next to each other.

The float CSS property specifies that an element should be taken from the normal flow and placed along the left or right side of its container, where text and inline elements will wrap around it. A floating element is one where the computed value of float is not none.


Get rid of the float, and the divs will be aligned under each other.
If this does not happen, you'll have some other css on divs or children of wrapper defining a floating behaviour or an inline display.

If you want to keep the float, for whatever reason, you can use clear on the 2nd div to reset the floating properties of elements before that element.
clear has 5 valid values: none | left | right | both | inherit. Clearing no floats (used to override inherited properties), left or right floats or both floats. Inherit means it'll inherit the behaviour of the parent element

Also, because of the default behaviour, you don't need to set the width and height on auto.
You only need this is you want to set a hardcoded height/width. E.g. 80% / 800px / 500em / ...

<div id="wrapper">
    <div id="inner1"></div>
    <div id="inner2"></div>

CSS is

    height:auto; // this is not needed, as parent container, this div will size automaticly
    width:auto; // this is not needed, as parent container, this div will size automaticly

You can get rid of the inner divs in the css, unless you want to style them.
If you want to style them identicly, you can use concatenation
#inner1, #inner2 {
    border: 1px solid black;

How to access array elements in a Django template?

You can access sequence elements with arr.0 arr.1 and so on. See The Django template system chapter of the django book for more information.

Shell script to check if file exists

One approach:

  shopt -s nullglob
  if [[ "${#files[@]}" -gt 0 ]] ; then
    echo found one
    echo found none


  • shopt -s nullglob will cause /home/edward/bank1/fiche/Test* to expand to nothing if no file matches that pattern. (Without it, it will be left intact.)
  • ( ... ) sets up a subshell, preventing shopt -s nullglob from "escaping".
  • files=(/home/edward/bank1/fiche/Test*) puts the file-list in an array named files. (Note that this is within the subshell only; files will not be accessible after the subshell exits.)
  • "${#files[@]}" is the number of elements in this array.

Edited to address subsequent question ("What if i also need to check that these files have data in them and are not zero byte files"):

For this version, we need to use -s (as you did in your question), which also tests for the file's existence, so there's no point using shopt -s nullglob anymore: if no file matches the pattern, then -s on the pattern will be false. So, we can write:

  for file in /home/edward/bank1/fiche/Test* ; do
    if [[ -s "$file" ]] ; then
  if [[ "$found_nonempty" ]] ; then
    echo found one
    echo found none

(Here the ( ... ) is to prevent file and found_file from "escaping".)

Default values for Vue component props & how to check if a user did not set the prop?

Also something important to add here, in order to set default values for arrays and objects we must use the default function for props:

propE: {
      type: Object,
      // Object or array defaults must be returned from
      // a factory function
      default: function () {
        return { message: 'hello' }

Git log to get commits only for a specific branch

This will output the commits on the current branch. If any argument is passed, it just outputs the hashes.


function show_help()
  ME=$(basename $0)
  IT=$(cat <<EOF
  Compares 2 different branches, and lists the commits found only 
  in the first branch (newest branch). 

  $ME         -> default. compares current branch to master
  $ME B1      -> compares branch B1 to master
  $ME B1 B2   -> compares branch B1 to B2
  $ME B1 B2 V -> compares branch B1 to B2, and displays commit messages
  echo "$IT"

if [ "$1" == "help" ]

# Show commit msgs if any arg passed for arg 3
if [ "$3" ]

# get branch names
if [ -z "$1" ]
  NEWER_BRANCH=$(git rev-parse --abbrev-ref HEAD)

  echo "  Please supply 2 different branches to compare!"


if [ -z "$OUT" ]
  echo "No differences found. The branches $NEWER_BRANCH and $OLDER_BRANCH are in sync."

if [ "$OPT" == "-v" ]
  echo "$OUT"
  echo "$OUT" | awk '{print $2}'

Bash script processing limited number of commands in parallel

See parallel. Its syntax is similar to xargs, but it runs the commands in parallel.

Cannot open output file, permission denied

Make sure to run 7zip in 'Administrator mode' for extracting to Program Files.

Also, temporarily turning off virus protection worked for some people in the past.

ASP.Net MVC Redirect To A Different View

The simplest way is use return View.

return View("ViewName");

Remember, the physical name of the "ViewName" should be something like ViewName.cshtml in your project, if your are using MVC C# / .NET.

How to filter empty or NULL names in a QuerySet?

this is another simple way to do it .


how to fix the issue "Command /bin/sh failed with exit code 1" in iphone

I did all above and spent an hour on the issue.

Tried everything above as well as restarted Xcode.

Finally, restarted computer and everything working normally again!

How to specify jackson to only use fields - preferably globally

for jackson 1.9.10 I use

ObjectMapper mapper = new ObjectMapper();

mapper.setVisibility(JsonMethod.ALL, Visibility.NONE);
mapper.setVisibility(JsonMethod.FIELD, Visibility.ANY);

to turn of auto dedection.

Django - how to create a file and save it to a model's FileField?

You want to have a look at FileField and FieldFile in the Django docs, and especially

Basically, a field declared as a FileField, when accessed, gives you an instance of class FieldFile, which gives you several methods to interact with the underlying file. So, what you need to do is:, new_contents)

where new_name is the filename you wish assigned and new_contents is the content of the file. Note that new_contents must be an instance of either django.core.files.File or django.core.files.base.ContentFile (see given links to manual for the details).

The two choices boil down to:

from django.core.files.base import ContentFile, File

# Using File
with open('/path/to/file') as f:, File(f))

# Using ContentFile, ContentFile('A string with the file content'))

How do I display Ruby on Rails form validation error messages one at a time?

I resolved it like this:

<% @user.errors.each do |attr, msg| %>
    <%= @user.errors.full_messages_for(attr).first if @user.errors[attr].first == msg %>
<% end %>

This way you are using the locales for the error messages.

Locking pattern for proper use of .NET MemoryCache

This is my 2nd iteration of the code. Because MemoryCache is thread safe you don't need to lock on the initial read, you can just read and if the cache returns null then do the lock check to see if you need to create the string. It greatly simplifies the code.

const string CacheKey = "CacheKey";
static readonly object cacheLock = new object();
private static string GetCachedData()

    //Returns null if the string does not exist, prevents a race condition where the cache invalidates between the contains check and the retreival.
    var cachedString = MemoryCache.Default.Get(CacheKey, null) as string;

    if (cachedString != null)
        return cachedString;

    lock (cacheLock)
        //Check to see if anyone wrote to the cache while we where waiting our turn to write the new value.
        cachedString = MemoryCache.Default.Get(CacheKey, null) as string;

        if (cachedString != null)
            return cachedString;

        //The value still did not exist so we now write it in to the cache.
        var expensiveString = SomeHeavyAndExpensiveCalculation();
        CacheItemPolicy cip = new CacheItemPolicy()
                                  AbsoluteExpiration = new DateTimeOffset(DateTime.Now.AddMinutes(20))
        MemoryCache.Default.Set(CacheKey, expensiveString, cip);
        return expensiveString;

EDIT: The below code is unnecessary but I wanted to leave it to show the original method. It may be useful to future visitors who are using a different collection that has thread safe reads but non-thread safe writes (almost all of classes under the System.Collections namespace is like that).

Here is how I would do it using ReaderWriterLockSlim to protect access. You need to do a kind of "Double Checked Locking" to see if anyone else created the cached item while we where waiting to to take the lock.

const string CacheKey = "CacheKey";
static readonly ReaderWriterLockSlim cacheLock = new ReaderWriterLockSlim();
static string GetCachedData()
    //First we do a read lock to see if it already exists, this allows multiple readers at the same time.
        //Returns null if the string does not exist, prevents a race condition where the cache invalidates between the contains check and the retreival.
        var cachedString = MemoryCache.Default.Get(CacheKey, null) as string;

        if (cachedString != null)
            return cachedString;

    //Only one UpgradeableReadLock can exist at one time, but it can co-exist with many ReadLocks
        //We need to check again to see if the string was created while we where waiting to enter the EnterUpgradeableReadLock
        var cachedString = MemoryCache.Default.Get(CacheKey, null) as string;

        if (cachedString != null)
            return cachedString;

        //The entry still does not exist so we need to create it and enter the write lock
        var expensiveString = SomeHeavyAndExpensiveCalculation();
        cacheLock.EnterWriteLock(); //This will block till all the Readers flush.
            CacheItemPolicy cip = new CacheItemPolicy()
                AbsoluteExpiration = new DateTimeOffset(DateTime.Now.AddMinutes(20))
            MemoryCache.Default.Set(CacheKey, expensiveString, cip);
            return expensiveString;

ASP.NET Web Api: The requested resource does not support http method 'GET'

Have the same Setup as OP. One controller with many actions... less "messy" :-)

In my case i forgot the "[HttpGet]" when adding a new action.

public IEnumerable<string> TestApiCall()
    return new string[] { "aa", "bb" };

Best practice for instantiating a new Android Fragment

Best practice to instance fragments with arguments in android is to have static factory method in your fragment.

public static MyFragment newInstance(String name, int age) {
    Bundle bundle = new Bundle();
    bundle.putString("name", name);
    bundle.putInt("age", age);

    MyFragment fragment = new MyFragment();

    return fragment;

You should avoid setting your fields with the instance of a fragment. Because whenever android system recreate your fragment, if it feels that the system needs more memory, than it will recreate your fragment by using constructor with no arguments.

You can find more info about best practice to instantiate fragments with arguments here.

CodeIgniter PHP Model Access "Unable to locate the model you have specified"

If you are on Linux then make sure your File name must match with the string passed in the load model methods the first argument.


You can use the second argument using that you can call methods from your model and it will work on Linux and windows as well

$result = $this->order_model->get_order_details($orderID);

Can you have multiple $(document).ready(function(){ ... }); sections?

Yes, it's perfectly ok.but avoid doing it without a reason. For example I used it to declare global site rules seperately than indivual pages when my javascript files were generated dynamically but if you just keep doing it over and over it will make it hard to read.

Also you can not access some methods from another jQuery(function(){}); call so that's another reason you don't wanna do that.

With the old window.onload though you will replace the old one every time you specified a function.

How to format DateTime to 24 hours time?


How to convert FormData (HTML5 object) to JSON

If you need support for serializing nested fields, similar to how PHP handles form fields, you can use the following function

function update(data, keys, value) {_x000D_
  if (keys.length === 0) {_x000D_
    // Leaf node_x000D_
    return value;_x000D_
  let key = keys.shift();_x000D_
  if (!key) {_x000D_
    data = data || [];_x000D_
    if (Array.isArray(data)) {_x000D_
      key = data.length;_x000D_
  // Try converting key to a numeric value_x000D_
  let index = +key;_x000D_
  if (!isNaN(index)) {_x000D_
    // We have a numeric index, make data a numeric array_x000D_
    // This will not work if this is a associative array _x000D_
    // with numeric keys_x000D_
    data = data || [];_x000D_
    key = index;_x000D_
  // If none of the above matched, we have an associative array_x000D_
  data = data || {};_x000D_
  let val = update(data[key], keys, value);_x000D_
  data[key] = val;_x000D_
  return data;_x000D_
function serializeForm(form) {_x000D_
  return Array.from((new FormData(form)).entries())_x000D_
    .reduce((data, [field, value]) => {_x000D_
      let [_, prefix, keys] = field.match(/^([^\[]+)((?:\[[^\]]*\])*)/);_x000D_
      if (keys) {_x000D_
        keys = Array.from(keys.matchAll(/\[([^\]]*)\]/g), m => m[1]);_x000D_
        value = update(data[prefix], keys, value);_x000D_
      data[prefix] = value;_x000D_
      return data;_x000D_
    }, {});_x000D_
document.getElementById('output').textContent = JSON.stringify(serializeForm(document.getElementById('form')), null, 2);
<form id="form">_x000D_
  <input name="field1" value="Field 1">_x000D_
  <input name="field2[]" value="Field 21">_x000D_
  <input name="field2[]" value="Field 22">_x000D_
  <input name="field3[a]" value="Field 3a">_x000D_
  <input name="field3[b]" value="Field 3b">_x000D_
  <input name="field3[c]" value="Field 3c">_x000D_
  <input name="field4[x][a]" value="Field xa">_x000D_
  <input name="field4[x][b]" value="Field xb">_x000D_
  <input name="field4[x][c]" value="Field xc">_x000D_
  <input name="field4[y][a]" value="Field ya">_x000D_
  <input name="field5[z][0]" value="Field z0">_x000D_
  <input name="field5[z][]" value="Field z1">_x000D_
  <input name="field6.z" value="Field 6Z0">_x000D_
  <input name="field6.z" value="Field 6Z1">_x000D_
<pre id="output">_x000D_

Vlookup referring to table data in a different sheet

I faced this problem and when i started searching the important point i found is, the value u are looking up i.e M3 column should be present in the first column of the table u want to search check in lookup_value

TypeError: int() argument must be a string, a bytes-like object or a number, not 'list'

What the error is telling, is that you can't convert an entire list into an integer. You could get an index from the list and convert that into an integer:

x = ["0", "1", "2"] 
y = int(x[0]) #accessing the zeroth element

If you're trying to convert a whole list into an integer, you are going to have to convert the list into a string first:

x = ["0", "1", "2"]
y = ''.join(x) # converting list into string
z = int(y)

If your list elements are not strings, you'll have to convert them to strings before using str.join:

x = [0, 1, 2]
y = ''.join(map(str, x))
z = int(y)

Also, as stated above, make sure that you're not returning a nested list.

Bootstrap close responsive menu "on click"


Difference between a user and a schema in Oracle?

From Ask Tom

You should consider a schema to be the user account and collection of all objects therein as a schema for all intents and purposes.

SCOTT is a schema that includes the EMP, DEPT and BONUS tables with various grants, and other stuff.

SYS is a schema that includes tons of tables, views, grants, etc etc etc.

SYSTEM is a schema.....

Technically -- A schema is the set of metadata (data dictionary) used by the database, typically generated using DDL. A schema defines attributes of the database, such as tables, columns, and properties. A database schema is a description of the data in a database.

Why there is no ConcurrentHashSet against ConcurrentHashMap

import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

public class ConcurrentHashSet<E> extends AbstractSet<E> implements Set<E>{
   private final ConcurrentMap<E, Object> theMap;

   private static final Object dummy = new Object();

   public ConcurrentHashSet(){
      theMap = new ConcurrentHashMap<E, Object>();

   public int size() {
      return theMap.size();

   public Iterator<E> iterator(){
      return theMap.keySet().iterator();

   public boolean isEmpty(){
      return theMap.isEmpty();

   public boolean add(final E o){
      return theMap.put(o, ConcurrentHashSet.dummy) == null;

   public boolean contains(final Object o){
      return theMap.containsKey(o);

   public void clear(){

   public boolean remove(final Object o){
      return theMap.remove(o) == ConcurrentHashSet.dummy;

   public boolean addIfAbsent(final E o){
      Object obj = theMap.putIfAbsent(o, ConcurrentHashSet.dummy);
      return obj == null;

IntelliJ does not show 'Class' when we right click and select 'New'

Another possible solution is that the project name is not acceptable. For example, creating a project with spaces in the name does not block the project creation but the proper sources are not marked and when those are marked manually, I still was unable to create classes. Recreating the project with hyphens (-) instead of spaces corrected the problem for me.

round up to 2 decimal places in java?

String roundOffTo2DecPlaces(float val)
    return String.format("%.2f", val);

List of <p:ajax> events

Here's what I found during debug.

enter image description here

WebSockets protocol vs HTTP

Why is the WebSockets protocol better?

I don't think we can compare them side by side like who is better. That won't be a fair comparison simply because they are solving two different problems. Their requirements are different. It will be like comparing apples to oranges. They are different.

HTTP is a request-response protocol. The client (browser) wants something, the server gives it. That is. If the data client wants is big, the server might send streaming data to void unwanted buffer problems. Here the main requirement or problem is how to make the request from clients and how to response the resources(hypertext) they request. That is where HTTP shine.

In HTTP, only client requests. The server only responds.

WebSocket is not a request-response protocol where only the client can request. It is a socket(very similar to TCP socket). Mean once the connection is open, either side can send data until the underlining TCP connection is closed. It is just like a normal socket. The only difference with TCP socket is WebSocket can be used on the web. On the web, we have many restrictions on a normal socket. Most firewalls will block other ports than 80 and 433 that HTTP used. Proxies and intermediaries will be problematic as well. So to make the protocol easier to deploy to existing infrastructures WebSocket use HTTP handshake to upgrade. That means when the first time connection is going to open, the client sent an HTTP request to tell the server saying "That is not HTTP request, please upgrade to WebSocket protocol".

Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13

Once the server understands the request and upgraded to WebSocket protocol, none of the HTTP protocols applied anymore.

So my answer is Neither one is better than each other. They are completely different.

Why was it implemented instead of updating the HTTP protocol?

Well, we can make everything under the name called HTTP as well. But shall we? If they are two different things, I will prefer two different names. So do Hickson and Michael Carter .

How can I check if a file exists in Perl?

You might want a variant of exists ... perldoc -f "-f"

       -X EXPR
       -X      A file test, where X is one of the letters listed below.  This unary operator takes one argument,
               either a filename, a filehandle, or a dirhandle, and tests the associated file to see if something is
               true about it.  If the argument is omitted, tests $_, except for "-t", which tests STDIN.  Unless
               otherwise documented, it returns 1 for true and '' for false, or the undefined value if the file
               doesn’t exist.  Despite the funny names, precedence is the same as any other named unary operator.
               The operator may be any of:

                   -r  File is readable by effective uid/gid.
                   -w  File is writable by effective uid/gid.
                   -x  File is executable by effective uid/gid.
                   -o  File is owned by effective uid.

                   -R  File is readable by real uid/gid.
                   -W  File is writable by real uid/gid.
                   -X  File is executable by real uid/gid.
                   -O  File is owned by real uid.

                   -e  File exists.
                   -z  File has zero size (is empty).
                   -s  File has nonzero size (returns size in bytes).

                   -f  File is a plain file.
                   -d  File is a directory.
                   -l  File is a symbolic link.
                   -p  File is a named pipe (FIFO), or Filehandle is a pipe.
                   -S  File is a socket.
                   -b  File is a block special file.
                   -c  File is a character special file.
                   -t  Filehandle is opened to a tty.

                   -u  File has setuid bit set.
                   -g  File has setgid bit set.
                   -k  File has sticky bit set.

                   -T  File is an ASCII text file (heuristic guess).
                   -B  File is a "binary" file (opposite of -T).

                   -M  Script start time minus file modification time, in days.

JQuery Event for user pressing enter in a textbox?

If your input is search, you also can use on 'search' event. Example

<input type="search" placeholder="Search" id="searchTextBox">


$("#searchPostTextBox").on('search', function () {
    alert("search value: "+$(this).val());

Select subset of columns in data.table R

Option using dplyr

dt <- select(dt, -V1, -V2, -V3, -V4)

Get element inside element by class and ID - JavaScript

Well, first you need to select the elements with a function like getElementById.

var targetDiv = document.getElementById("foo").getElementsByClassName("bar")[0];

getElementById only returns one node, but getElementsByClassName returns a node list. Since there is only one element with that class name (as far as I can tell), you can just get the first one (that's what the [0] is for—it's just like an array).

Then, you can change the html with .textContent.

targetDiv.textContent = "Goodbye world!";

var targetDiv = document.getElementById("foo").getElementsByClassName("bar")[0];_x000D_
targetDiv.textContent = "Goodbye world!";
<div id="foo">_x000D_
    <div class="bar">_x000D_
        Hello world!_x000D_

Conditionally formatting cells if their value equals any value of another column

I was looking into this and loved the approach from peege using a for loop! (because I'm learning VBA at the moment)

However, if we are trying to match "any" value of another column, how about using nested loops like the following?

Sub MatchAndColor()

Dim lastRow As Long
Dim sheetName As String

sheetName = "Sheet1"            'Insert your sheet name here
lastRow = Sheets(sheetName).Range("A" & Rows.Count).End(xlUp).Row

For lRowA = 1 To lastRow         'Loop through all rows
    For lRowB = 1 To lastRow
        If Sheets(sheetName).Cells(lRowA, "A") = Sheets(sheetName).Cells(lRowB, "B") Then

        Sheets(sheetName).Cells(lRowA, "A").Interior.ColorIndex = 3  'Set Color to RED
    End If

Next lRowB
Next lRowA

End Sub

Jar mismatch! Fix your dependencies

Actionbarsherlock has the support library in it. This probably causes a conflict if the support library is also in your main project.

Remove android-support-v4.jar from your project's libs directory.

Also Remove android-support-v4.jar from your second library and then try again.

Jar Mismatch Found 2 versions of android-support-v4.jar in the dependency list

How to create an on/off switch with Javascript/CSS?

Initial answer from 2013

If you don't mind something related to Bootstrap, an excellent (unofficial) Bootstrap Switch is available.

Classic 2013 Switch

It uses radio types or checkboxes as switches. A type attribute has been added since V.1.8.

Source code is available on Github.

Note from 2018

I would not recommend to use those kind of old Switch buttons now, as they always seemed to suffer of usability issues as pointed by many people.

Please consider having a look at modern Switches like those.

Modern 2018 Switch

Maven build debug in Eclipse

if you are using Maven 2.0.8+, then it will be very simple, run mvndebug from the console, and connect to it via Remote Debug Java Application with port 8000.

How to convert String to DOM Document object in java?

Either escape the double quotes with \

String xmlString = "<element attribname=\"value\" attribname1=\"value1\"> pcdata</element>"

or use single quotes instead

String xmlString = "<element attribname='value' attribname1='value1'> pcdata</element>"

Mean of a column in a data frame, given the column's name

Any of the following should work!!

df <- data.frame(x=1:3,y=4:6)


What is <scope> under <dependency> in pom.xml for?

added good images with explain scopes

enter image description here

enter image description here

Fetching distinct values on a column using Spark DataFrame

This solution demonstrates how to transform data with Spark native functions which are better than UDFs. It also demonstrates how dropDuplicates which is more suitable than distinct for certain queries.

Suppose you have this DataFrame:

|country|    continent|
|  china|         asia|
| brazil|south america|
| france|       europe|
|  china|         asia|

Here's how to take all the distinct countries and run a transformation:

  .withColumn("country", concat(col("country"), lit(" is fun!")))
|       country|
|brazil is fun!|
|france is fun!|
| china is fun!|

You can use dropDuplicates instead of distinct if you don't want to lose the continent information:

  .withColumn("description", concat(col("country"), lit(" is a country in "), col("continent")))
|country|continent    |description                         |
|brazil |south america|brazil is a country in south america|
|france |europe       |france is a country in europe       |
|china  |asia         |china is a country in asia          |

See here for more information about filtering DataFrames and here for more information on dropping duplicates.

Ultimately, you'll want to wrap your transformation logic in custom transformations that can be chained with the Dataset#transform method.

Should I use scipy.pi, numpy.pi, or math.pi?

One thing to note is that not all libraries will use the same meaning for pi, of course, so it never hurts to know what you're using. For example, the symbolic math library Sympy's representation of pi is not the same as math and numpy:

import math
import numpy
import scipy
import sympy

print(math.pi == numpy.pi)
> True
print(math.pi == scipy.pi)
> True
print(math.pi == sympy.pi)
> False

What is the best way to calculate a checksum for a file that is on my machine?

In HPUX ( hp UNIX)

Please install the md5sum package on your UNIX machine for example, if there is a file called a.txt

shell > md5sum a.txt

Google Recaptcha v3 example demo

if you are newly implementing recaptcha on your site, I would suggest adding api.js and let google collect behavioral data of your users 1-2 days. It is much fail-safe this way, especially before starting to use score.

Invoke JSF managed bean action on page load

Another easy way is to use fire the method before the view is rendered. This is better than postConstruct because for sessionScope, postConstruct will fire only once every session. This will fire every time the page is loaded. This is ofcourse only for JSF 2.0 and not for JSF 1.2.

This is how to do it -

<html xmlns:f="">
          <f:event type="preRenderView" listener="#{myController.onPageLoad}"/>

And in the

 public void onPageLoad(){
    // Do something

EDIT - Though this is not a solution for the question on this page, I add this just for people using higher versions of JSF.

JSF 2.2 has a new feature which performs this task using viewAction.

    <f:viewAction action="#{myController.onPageLoad}" />

MySql Inner Join with WHERE clause

You are using two WHERE clauses but only one is allowed. Use it like this:

SELECT table1.f_id FROM table1
INNER JOIN table2 ON table2.f_id = table1.f_id
  table1.f_com_id = '430'
  AND table1.f_status = 'Submitted'
  AND table2.f_type = 'InProcess'

Creating object with dynamic keys

In the new ES2015 standard for JavaScript (formerly called ES6), objects can be created with computed keys: Object Initializer spec.

The syntax is:

var obj = {
  [myKey]: value,

If applied to the OP's scenario, it would turn into:

stuff = function (thing, callback) {
  var inputs  = $('div.quantity > input').map(function(){
    return {
      [this.attr('name')]: this.attr('value'),

  callback(null, inputs);

Note: A transpiler is still required for browser compatiblity.

Using Babel or Google's traceur, it is possible to use this syntax today.

In earlier JavaScript specifications (ES5 and below), the key in an object literal is always interpreted literally, as a string.

To use a "dynamic" key, you have to use bracket notation:

var obj = {};
obj[myKey] = value;

In your case:

stuff = function (thing, callback) {
  var inputs  = $('div.quantity > input').map(function(){
    var key   = this.attr('name')
     ,  value = this.attr('value')
     ,  ret   = {};

     ret[key] = value;
     return ret;

  callback(null, inputs);

Why do I get an error instantiating an interface?

Imagine if one went into a store and asked for a device with a power switch. You didn't say whether you wanted a copier, television, vacuum cleaner, desk lamp, waffle maker, or anything. You asked for a device with a power switch. Would you expect the clerk to offer you something that could only be described as "a device with a power switch"?

A typical interface would be analogous to the description "a device with a power switch". Knowing that a piece of equipment is " a device with a power switch" would allow one to do some operations with it (i.e. turn it on and off), and one might plausibly want a list of e.g. "devices with power switches that will need to be turned off at the end of the day", without the devices having to share any characteristic beyond having a power switch, but such situations generally only apply when applying some common operation to devices that were created for some more specific purpose. When creating something from scratch, one would more likely wand a "copier", "television", "vacuum cleaner", or other particular type of device, than some random "device with a power switch".

There are some circumstances where one may want a vaguely-defined object, and really not care about what exactly it is. "Give me your cheapest device that can boil water". It would be nice if one could specify that when someone asks for an arbitrary object with "water boiling" ability, they should be offered an Acme 359 Electric Teakettle, and indeed when using classes it's possible to do that. Note, however, that someone who asks for a "device to boil water" would not be given a "device to boil water", but an "Acme 359 Electric Teakettle".

Trying to detect browser close event

jQuery .bind() has been deprecated. Use .on() instead

$(window).on("beforeunload", function() {

Unable to install pyodbc on Linux

I know this is an old question, but the maintainer has a pyodbc GitHub Repo.

I also found a very good example for installing FreeTDS and setting up the config files.

Following the instructions on the GitHub docs seems to me to always be the best option. As of February, 2018, for CentOs7 (they have all flavors at the link) they say:

# Add the RHEL 6 library for Centos-7 of MSSQL driver. Centos7 uses RHEL-6 Libraries.
sudo su 
curl > /etc/yum.repos.d/mssql-release.repo

# Uninstall if already installed Unix ODBC driver
sudo yum remove unixODBC-utf16 unixODBC-utf16-devel #to avoid conflicts

# Install the  msodbcsql unixODBC-utf16 unixODBC-utf16-devel driver
sudo ACCEPT_EULA=Y yum install msodbcsql

#optional: for bcp and sqlcmd
sudo ACCEPT_EULA=Y yum install mssql-tools
echo 'export PATH="$PATH:/opt/mssql-tools/bin"' >> ~/.bash_profile
echo 'export PATH="$PATH:/opt/mssql-tools/bin"' >> ~/.bashrc
source ~/.bashrc

# optional: for unixODBC development headers
sudo yum install unixODBC-devel

# the Microsoft driver expects unixODBC to be here /usr/lib64/, so add soft links to the '.so.2' files
cd /usr/lib64
sudo ln -s
sudo ln -s
sudo ln -s

# Set the path for unixODBC
export ODBCINI=/usr/local/etc/odbc.ini
export ODBCSYSINI=/usr/local/etc
source ~/.bashrc

# Prepare a temp file for defining the DSN to your database server
vi /home/user/odbcadd.txt

Driver      = ODBC Driver 13 for SQL Server
Description = My MS SQL Server
Trace       = No
Server      =

# register the SQL Server database DSN information in /etc/odbc.ini
sudo odbcinst -i -s -f /home/user/odbcadd.txt -l

# check the DSN installation with:
odbcinst -j
cat /etc/odbc.ini

# should contain a section called [MyMSSQLServer]

# install the python driver for database connection
pip install pyodbc

Java Interfaces/Implementation naming convention

I use both conventions:

If the interface is a specific instance of a a well known pattern (e.g. Service, DAO), then it may not need an "I" (e.g UserService, AuditService, UserDao) all work fine without the "I", because the post-fix determines the meta pattern.

But, if you have something one-off or two-off (usually for a callback pattern), then it helps to distinguish it from a class (e.g. IAsynchCallbackHandler, IUpdateListener, IComputeDrone). These are special purpose interfaces designed for internal use, occasionally the IInterface calls out attention to the fact that an operand is actually an interface, so at first glance it is immediately clear.

In other cases you can use the I to avoid colliding with other commonly known concrete classes (ISubject, IPrincipal vs Subject or Principal).

How do I convert this list of dictionaries to a csv file?

Here is another, more general solution assuming you don't have a list of rows (maybe they don't fit in memory) or a copy of the headers (maybe the write_csv function is generic):

def gen_rows():
    yield OrderedDict(name='bob', age=25, weight=200)
    yield OrderedDict(name='jim', age=31, weight=180)

def write_csv():
    it = genrows()
    first_row =  # __next__ in py3
    with open("people.csv", "w") as outfile:
        wr = csv.DictWriter(outfile, fieldnames=list(first_row))

Note: the OrderedDict constructor used here only preserves order in python >3.4. If order is important, use the OrderedDict([('name', 'bob'),('age',25)]) form.

Forking vs. Branching in GitHub

Forking creates an entirely new repository from existing repository (simply doing git clone on gitHub/bitbucket)

Forks are best used: when the intent of the ‘split’ is to create a logically independent project, which may never reunite with its parent.

Branch strategy creates a new branch over the existing/working repository

Branches are best used: when they are created as temporary places to work through a feature, with the intent to merge the branch with the origin.

More Specific :- In open source projects it is the owner of the repository who decides who can push to the repository. However, the idea of open source is that everybody can contribute to the project.

This problem is solved by forks: any time a developer wants to change something in an open source project, they don’t clone the official repository directly. Instead, they fork it to create a copy. When the work is finished, they make a pull request so that the owner of the repository can review the changes and decide whether to merge them to his project.

At its core forking is similar to feature branching, but instead of creating branches a fork of the repository is made, and instead of doing a merge request you create a pull request.

The below links provide the difference in a well-explained manner :

Is there a Social Security Number reserved for testing/examples?

Please look at this document

The SSA is instituting a new policy the where all previously unused sequences are will be available for use.

Goes into affect June 25, 2011.

Taken from the new FAQ:

What changes will result from randomization?

The SSA will eliminate the geographical significance of the first three digits of the SSN, currently referred to as the area number, by no longer allocating the area numbers for assignment to individuals in specific states. The significance of the highest group number (the fourth and fifth digits of the SSN) for validation purposes will be eliminated. Randomization will also introduce previously unassigned area numbers for assignment excluding area numbers 000, 666 and 900-999. Top

Will SSN randomization assign group number (the fourth and fifth digits of the SSN) 00 or serial number (the last four digits of the SSN) 0000?

SSN randomization will not assign group number 00 or serial number 0000. SSNs containing group number 00 or serial number 0000 will continue to be invalid.

How do I revert an SVN commit?

First, revert the working copy to 1943.

> svn merge -c -1943 .

Second, check what is about to be commited.

> svn status

Third, commit version 1945.

> svn commit -m "Fix bad commit."

Fourth, look at the new log.

> svn log -l 4

1945 | myname | 2015-04-20 19:20:51 -0700 (Mon, 20 Apr 2015) | 1 line

Fix bad commit.
1944 | myname | 2015-04-20 19:09:58 -0700 (Mon, 20 Apr 2015) | 1 line

This is the bad commit that I made.
1943 | myname | 2015-04-20 18:36:45 -0700 (Mon, 20 Apr 2015) | 1 line

This was a good commit.

JAVA_HOME is set to an invalid directory:

Try the following:

  • Remove \bin from JAVA_HOME path.
  • Open new command line window.
  • Run your command as an administrator.

ImportError: No module named Crypto.Cipher

If you are using this module with Python3 and having trouble with import. try this.

pip uninstall crypto
pip uninstall pycryptodome
pip install pycryptodome

Good Luck!

Select entries between dates in doctrine 2

Look how I format my date $jour in the parameters. It depends if you use a expr()->like or a expr()->lte

        ->from('LdbPlanningBundle:EventEntity', 'e')
                    $qb->expr()->like('e.start', ':jour1'),
                    $qb->expr()->like('e.end', ':jour1'),
                        $qb->expr()->lte('e.start', ':jour2'),
                        $qb->expr()->gte('e.end', ':jour2')
                $qb->expr()->eq('e.user', ':user')
        ->andWhere('e.user = :user ')
        ->setParameter('user', $user)
        ->setParameter('jour1', '%'.$jour->format('Y-m-d').'%')
        ->setParameter('jour2', $jour->format('Y-m-d'))

Disable scrolling when touch moving certain element

There is a little "hack" on CSS that also allows you to disable scrolling:

.lock-screen {
    height: 100%;
    overflow: hidden;
    width: 100%;
    position: fixed;

Adding that class to the body will prevent scrolling.

Generate random string/characters in JavaScript

The npm module anyid provides flexible API to generate various kinds of string ID / code.

const id = anyid().encode('Aa0').length(5).random().id();

How to have Java method return generic list of any type?

No need to even pass the class:

public <T> List<T> magicalListGetter() {
    return new ArrayList<T>();

How to find a whole word in a String in java

A much simpler way to do this is to use split():

String match = "123woods";
String text = "I will come and meet you at the 123woods";

String[] sentence = text.split();
for(String word: sentence)
        return true;
return false;

This is a simpler, less elegant way to do the same thing without using tokens, etc.

How to tell if a JavaScript function is defined

If you look at the source of the library @Venkat Sudheer Reddy Aedama mentioned, underscorejs, you can see this:

_.isFunction = function(obj) {
  return typeof obj == 'function' || false;

This is just my HINT, HINT answer :>

How to run SQL in shell script



           select count(*) from table;


PL_CONNECT_STRING carry database username, password and it service name

sqlplus is used to connect the Database with PL_CONNECT_STRING details

END-OF-SQL tag contain the query which you want to execute

echo is used to print the output of the query

NOTE: You can give multiple Query inside the END-OF-SQL tag, so its useful for batch execution as well

Apply CSS styles to an element depending on its child elements

On top of @kp's answer:

I'm dealing with this and in my case, I have to show a child element and correct the height of the parent object accordingly (auto-sizing is not working in a bootstrap header for some reason I don't have time to debug).

But instead of using javascript to modify the parent, I think I'll dynamically add a CSS class to the parent and CSS-selectively show the children accordingly. This will maintain the decisions in the logic and not based on a CSS state.

tl;dr; apply the a and b styles to the parent <div>, not the child (of course, not everyone will be able to do this. i.e. Angular components making decisions of their own).

  .parent            { height: 50px; }
  .parent div        { display: none; }
  .with-children     { height: 100px; }
  .with-children div { display: block; }

<div class="parent">

  // to show the children

jQuery toggle animation

I dont think adding dual functions inside the toggle function works for a registered click event (Unless I'm missing something)

For example:

$('.btnName').click(function() {
 top.$('#panel').toggle(function() {
     // style change
   }, 500);
   function() {
     // style change back
   }, 500);

HTTPS connections over proxy servers

as far as i can remember, you need to use a HTTP CONNECT query on the proxy. this will convert the request connection to a transparent TCP/IP tunnel.

so you need to know if the proxy server you use support this protocol.

How to change the JDK for a Jenkins job?

There is a JDK dropdown in "job name" -> Configure in Jenkins web ui. It will list all JDKs available in Jenkins configuration.

How to set breakpoints in inline Javascript in Google Chrome?

You also can give a name to your script:

<script> ... (your code here) //# sourceURL=somename.js </script>

ofcourse replace "somename" by some name ;) and then you will see it in the chrome debugger at "Sources > top > (no domain) > somename.js" as a normal script and you will be able to debug it like other scripts

Including a .js file within a .js file

A popular method to tackle the problem of reducing JavaScript references from HTML files is by using a concatenation tool like Sprockets, which preprocesses and concatenates JavaScript source files together.

Apart from reducing the number of references from the HTML files, this will also reduce the number of hits to the server.

You may then want to run the resulting concatenation through a minification tool like jsmin to have it minified.

Simplest way to read json from a URL in java

Here are couple of alternatives versions with Jackson (since there are more than one ways you might want data as):

  ObjectMapper mapper = new ObjectMapper(); // just need one
  // Got a Java class that data maps to nicely? If so:
  FacebookGraph graph = mapper.readValue(url, FaceBookGraph.class);
  // Or: if no class (and don't need one), just map to Map.class:
  Map<String,Object> map = mapper.readValue(url, Map.class);

And specifically the usual (IMO) case where you want to deal with Java objects, can be made one liner:

FacebookGraph graph = new ObjectMapper().readValue(url, FaceBookGraph.class);

Other libs like Gson also support one-line methods; why many examples show much longer sections is odd. And even worse is that many examples use obsolete org.json library; it may have been the first thing around, but there are half a dozen better alternatives so there is very little reason to use it.

What is AndroidX?

androidx will replace support library after 28.0.0. You should migrate your project to use it. androidx uses Semantic Versioning. Using AndroidX will not be confused by version that is presented in library name and package name. Life becomes easier

[AndroidX and support compatibility]

How can I read SMS messages from the device programmatically in Android?

        final String myPackageName = getPackageName();
        if (!Telephony.Sms.getDefaultSmsPackage(this).equals(myPackageName)) {

            Intent intent = new Intent(Telephony.Sms.Intents.ACTION_CHANGE_DEFAULT);
            intent.putExtra(Telephony.Sms.Intents.EXTRA_PACKAGE_NAME, myPackageName);
            startActivityForResult(intent, 1);
        }else {
            List<Sms> lst = getAllSms();
    }else {
        List<Sms> lst = getAllSms();

Set app as default SMS app

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 1) {
    if (resultCode == RESULT_OK) {

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            final String myPackageName = getPackageName();
            if (Telephony.Sms.getDefaultSmsPackage(mActivity).equals(myPackageName)) {

                List<Sms> lst = getAllSms();

Function to get SMS

public List<Sms> getAllSms() {
    List<Sms> lstSms = new ArrayList<Sms>();
    Sms objSms = new Sms();
    Uri message = Uri.parse("content://sms/");
    ContentResolver cr = mActivity.getContentResolver();

    Cursor c = cr.query(message, null, null, null, null);
    int totalSMS = c.getCount();

    if (c.moveToFirst()) {
        for (int i = 0; i < totalSMS; i++) {

            objSms = new Sms();
            if (c.getString(c.getColumnIndexOrThrow("type")).contains("1")) {
            } else {

    // else {
    // throw new RuntimeException("You have no SMS");
    // }

    return lstSms;

Sms class is below:

public class Sms{
private String _id;
private String _address;
private String _msg;
private String _readState; //"0" for have not read sms and "1" for have read sms
private String _time;
private String _folderName;

public String getId(){
return _id;
public String getAddress(){
return _address;
public String getMsg(){
return _msg;
public String getReadState(){
return _readState;
public String getTime(){
return _time;
public String getFolderName(){
return _folderName;

public void setId(String id){
_id = id;
public void setAddress(String address){
_address = address;
public void setMsg(String msg){
_msg = msg;
public void setReadState(String readState){
_readState = readState;
public void setTime(String time){
_time = time;
public void setFolderName(String folderName){
_folderName = folderName;


Don't forget to define permission in your AndroidManifest.xml

<uses-permission android:name="android.permission.READ_SMS" />

Among $_REQUEST, $_GET and $_POST which one is the fastest?

if (isset($_GET['s'])) {
  $temp = $_GET['s'];
else {
  $temp = $_POST['s'];

Use that because it is safer and it won't make noticeable speed difference

How to read a text file?

It depends on what you are trying to do.

file, err := os.Open("file.txt")

The reason it outputs &{0xc082016240}, is because you are printing the pointer value of a file-descriptor (*os.File), not file-content. To obtain file-content, you may READ from a file-descriptor.

To read all file content(in bytes) to memory, ioutil.ReadAll

package main

import (

func main() {
    file, err := os.Open("file.txt")
    if err != nil {
    defer func() {
        if err = f.Close(); err != nil {

  b, err := ioutil.ReadAll(file)

But sometimes, if the file size is big, it might be more memory-efficient to just read in chunks: buffer-size, hence you could use the implementation of io.Reader.Read from *os.File

func main() {
    file, err := os.Open("file.txt")
    if err != nil {
    defer func() {
        if err = f.Close(); err != nil {

    buf := make([]byte, 32*1024) // define your buffer size here.

    for {
        n, err := file.Read(buf)

        if n > 0 {
            fmt.Print(buf[:n]) // your read buffer.

        if err == io.EOF {
        if err != nil {
            log.Printf("read %d bytes: %v", n, err)


Otherwise, you could also use the standard util package: bufio, try Scanner. A Scanner reads your file in tokens: separator.

By default, scanner advances the token by newline (of course you can customise how scanner should tokenise your file, learn from here the bufio test).

package main

import (

func main() {
    file, err := os.Open("file.txt")
    if err != nil {
    defer func() {
        if err = f.Close(); err != nil {

    scanner := bufio.NewScanner(file)

    for scanner.Scan() {             // internally, it advances token based on sperator
        fmt.Println(scanner.Text())  // token in unicode-char
        fmt.Println(scanner.Bytes()) // token in bytes


Lastly, I would also like to reference you to this awesome site: go-lang file cheatsheet. It encompassed pretty much everything related to working with files in go-lang, hope you'll find it useful.

The PowerShell -and conditional operator

Another option:

if( ![string]::IsNullOrEmpty($user_sam) -and ![string]::IsNullOrEmpty($user_case) )

If using maven, usually you put under java or resources?

Some "data mining" accounts for that src/main/resources is the typical place.

Results on Google Code Search:

  • src/main/resources/ 4877
  • src/main/java/ 215

Why does git say "Pull is not possible because you have unmerged files"?

You are attempting to add one more new commits into your local branch while your working directory is not clean. As a result, Git is refusing to do the pull. Consider the following diagrams to better visualize the scenario:

remote: A <- B <- C <- D
local: A <- B*
(*indicates that you have several files which have been modified but not committed.)

There are two options for dealing with this situation. You can either discard the changes in your files, or retain them.

Option one: Throw away the changes
You can either use git checkout for each unmerged file, or you can use git reset --hard HEAD to reset all files in your branch to HEAD. By the way, HEAD in your local branch is B, without an asterisk. If you choose this option, the diagram becomes:

remote: A <- B <- C <- D
local: A <- B

Now when you pull, you can fast-forward your branch with the changes from master. After pulling, you branch would look like master:

local: A <- B <- C <- D

Option two: Retain the changes
If you want to keep the changes, you will first want to resolve any merge conflicts in each of the files. You can open each file in your IDE and look for the following symbols:

<<<<<<< HEAD
// your version of the code
// the remote's version of the code

Git is presenting you with two versions of code. The code contained within the HEAD markers is the version from your current local branch. The other version is what is coming from the remote. Once you have chosen a version of the code (and removed the other code along with the markers), you can add each file to your staging area by typing git add. The final step is to commit your result by typing git commit -m with an appropriate message. At this point, our diagram looks like this:

remote: A <- B <- C <- D
local: A <- B <- C'

Here I have labelled the commit we just made as C' because it is different from the commit C on the remote. Now, if you try to pull you will get a non-fast forward error. Git cannot play the changes in remote on your branch, because both your branch and the remote have diverged from the common ancestor commit B. At this point, if you want to pull you can either do another git merge, or git rebase your branch on the remote.

Getting a mastery of Git requires being able to understand and manipulate uni-directional linked lists. I hope this explanation will get you thinking in the right direction about using Git.

Table header to stay fixed at the top when user scrolls it out of view with jQuery

Pure CSS (without IE11 support):

table th {
    position: -webkit-sticky; // this is for all Safari (Desktop & iOS), not for Chrome
    position: sticky;
    top: 0;
    z-index: 10; // any positive value, layer order is global
    background: #fff;

How to use TLS 1.2 in Java 6

I think that the solution of @Azimuts ( is for HTTP only connection. For FTPS connection you can use Bouncy Castle with without the need for rewrite FTPS protocol.

I have a program running on JRE 1.6.0_04 and I can not update the JRE.

The program has to connect to an FTPS server that work only with TLS 1.2 (IIS server).

I struggled for days and finally I have understood that there are few versions of bouncy castle library right in my use case: bctls-jdk15on-1.60.jar and bcprov-jdk15on-1.60.jar are ok, but 1.64 versions are not.

The version of apache commons-net is 3.1 .

Following is a small snippet of code that should work:



import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.jsse.provider.BouncyCastleJsseProvider;
import org.junit.Test;

public class FtpsTest {

// Create a trust manager that does not validate certificate chains
TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() {

    public[] getAcceptedIssuers() {
        return null;

    public void checkClientTrusted([] certs, String authType) {

    public void checkServerTrusted([] certs, String authType) {
} };

@Test public void test() throws Exception {

    Security.insertProviderAt(new BouncyCastleProvider(), 1);
    Security.addProvider(new BouncyCastleJsseProvider());

    SSLContext sslContext = SSLContext.getInstance("TLS", new BouncyCastleJsseProvider());
    sslContext.init(null, trustAllCerts, new SecureRandom()); ftpClient = new FTPSClient(sslContext);
    ByteArrayOutputStream out = null;
    try {

        ftpClient.connect("hostaname", 21);
        if (!FTPReply.isPositiveCompletion(ftpClient.getReplyCode())) {
            String msg = "Il server ftp ha rifiutato la connessione.";
            throw new Exception(msg);
        if (!ftpClient.login("username", "pwd")) {
            String msg = "Il server ftp ha rifiutato il login con username:  username  e pwd:  password  .";
            throw new Exception(msg);

        ftpClient.execPBSZ(0); // Set protection buffer size
        ftpClient.execPROT("P"); // Set data channel protection to private
        int bufSize = 1024 * 1024; // 1MB
        out = new ByteArrayOutputStream(bufSize);
        ftpClient.retrieveFile("remoteFileName", out);
    finally {
        if (out != null) {




Case Insensitive String comp in C

int strcmpInsensitive(char* a, char* b)
    return strcmp(lowerCaseWord(a), lowerCaseWord(b));

char* lowerCaseWord(char* a)
    char *b=new char[strlen(a)];
    for (int i = 0; i < strlen(a); i++)
        b[i] = tolower(a[i]);   
    return b;

good luck

Edit-lowerCaseWord function get a char* variable with, and return the lower case value of this char*. For example "AbCdE" for value of char*, will return "abcde".

Basically what it does is to take the two char* variables, after being transferred to lower case, and make use the strcmp function on them.

For example- if we call the strcmpInsensitive function for values of "AbCdE", and "ABCDE", it will first return both values in lower case ("abcde"), and then do strcmp function on them.

Change background position with jQuery

rebellion's answer above won't actually work, because to CSS, 'background-position' is actually shorthand for 'background-position-x' and 'background-position-y' so the correct version of his code would be:

    $('#submenu li').hover(function(){
        $('#carousel').css('background-position-x', newValueX);
        $('#carousel').css('background-position-y', newValue);
    }, function(){
        $('#carousel').css('background-position-x', oldValueX);
        $('#carousel').css('background-position-y', oldValueY);

It took about 4 hours of banging my head against it to come to that aggravating realization.

Is a Python list guaranteed to have its elements stay in the order they are inserted in?

You are confusing 'sets' and 'lists'. A set does not guarantee order, but lists do.

Sets are declared using curly brackets: {}. In contrast, lists are declared using square brackets: [].

mySet = {a, b, c, c}

Does not guarantee order, but list does:

myList = [a, b, c]

Python lookup hostname from IP with 1 second timeout

What you're trying to accomplish is called Reverse DNS lookup.

# => (hostname, alias-list, IP)

However, for the timeout part I have read about people running into problems with this. I would check out PyDNS or this solution for more advanced treatment.

How to delete items from a dictionary while iterating over it?

I tried the above solutions in Python3 but this one seems to be the only one working for me when storing objects in a dict. Basically you make a copy of your dict() and iterate over that while deleting the entries in your original dictionary.

        tmpDict = realDict.copy()
        for key, value in tmpDict.items():
            if value:

Soft Edges using CSS?

Another option is to use one of my personal favorite CSS tools: box-shadow.

A box shadow is really a drop-shadow on the node. It looks like this:

-moz-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
-webkit-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
box-shadow: 1px 2px 3px rgba(0,0,0,.5);

The arguments are:

1px: Horizontal offset of the effect. Positive numbers shift it right, negative left.
2px: Vertical offset of the effect. Positive numbers shift it down, negative up.
3px: The blur effect.  0 means no blur.
color: The color of the shadow.

So, you could leave your current design, and add a box-shadow like:

box-shadow: 0px -2px 2px rgba(34,34,34,0.6);

This should give you a 'blurry' top-edge.

This website will help with more information:

Where is Java Installed on Mac OS X?

Try This, It's easy way to find java installed path in Mac OS X,


1 ) /Library i.e Macintosh HD/Library

enter image description here

2) Click on Library in that we find Java folder.

enter image description here

3) So final path is


Hope so this is help for someone .

angular 2 how to return data from subscribe

You just can't return the value directly because it is an async call. An async call means it is running in the background (actually scheduled for later execution) while your code continues to execute.

You also can't have such code in the class directly. It needs to be moved into a method or the constructor.

What you can do is not to subscribe() directly but use an operator like map()

export class DataComponent{
    someMethod() {
      return this.http.get(path).map(res => {
        return res.json();

In addition, you can combine multiple .map with the same Observables as sometimes this improves code clarity and keeps things separate. Example:

validateResponse = (response) => validate(response);

parseJson = (json) => JSON.parse(json);

fetchUnits() {
    return this.http.get(requestUrl).map(this.validateResponse).map(this.parseJson);

This way an observable will be return the caller can subscribe to

export class DataComponent{
    someMethod() {
      return this.http.get(path).map(res => {
        return res.json();

    otherMethod() {
      this.someMethod().subscribe(data => = data);

The caller can also be in another class. Here it's just for brevity.

data => = data


res => return res.json()

are arrow functions. They are similar to normal functions. These functions are passed to subscribe(...) or map(...) to be called from the observable when data arrives from the response. This is why data can't be returned directly, because when someMethod() is completed, the data wasn't received yet.

AngularJS Error: $injector:unpr Unknown Provider

I was getting this problem and it turned out I had included my controller both in ui.router and in the html template as in

  function($stateProvider) {
    $stateProvider.state('dashboard', {
      url: '/dashboard',
      templateUrl: 'dashboard/views/index.html',
      controller: 'DashboardController'


<section data-ng-controller="DashboardController">

C# Numeric Only TextBox Control

You might want to try int.TryParse(string, out int) in the KeyPress(object, KeyPressEventArgs) event to check for numeric values. For the other problem you could use regular expressions instead.

Is there a simple way to use button to navigate page as a link does in angularjs

With bootstrap you can use

<a href="#/new-page.html" class="btn btn-primary">

How do I pull my project from github?

You Can do by Two ways,

1. Cloning the Remote Repo to your Local host

example: git clone

2. Pulling the Remote Repo to your Local host

First you have to create a git local repo by,

example: git init or git init repo-name then, git pull

That's all, All commits and branch in the remote repo now available in the local repository of your computer.

Happy Coding, cheers -:)

How to convert image file data in a byte array to a Bitmap?

The answer of Uttam didnt work for me. I just got null when I do:

Bitmap bitmap = BitmapFactory.decodeByteArray(bitmapdata, 0, bitmapdata.length);

In my case, bitmapdata only has the buffer of the pixels, so it is imposible for the function decodeByteArray to guess which the width, the height and the color bits use. So I tried this and it worked:

//Create bitmap with width, height, and 4 bytes color (RGBA)    
Bitmap bmp = Bitmap.createBitmap(imageWidth, imageHeight, Bitmap.Config.ARGB_8888);
ByteBuffer buffer = ByteBuffer.wrap(bitmapdata);

Check for different color options

In Python, can I call the main() of an imported module?

I had the same need using argparse too. The thing is parse_args function of an argparse.ArgumentParser object instance implicitly takes its arguments by default from sys.args. The work around, following Martijn line, consists of making that explicit, so you can change the arguments you pass to parse_args as desire.

def main(args):
    # some stuff
    parser = argparse.ArgumentParser()
    # some other stuff
    parsed_args = parser.parse_args(args)
    # more stuff with the args

if __name__ == '__main__':
    import sys

The key point is passing args to parse_args function. Later, to use the main, you just do as Martijn tell.

Python OpenCV2 (cv2) wrapper to get image size?

cv2 uses numpy for manipulating images, so the proper and best way to get the size of an image is using numpy.shape. Assuming you are working with BGR images, here is an example:

>>> import numpy as np
>>> import cv2
>>> img = cv2.imread('foo.jpg')
>>> height, width, channels = img.shape
>>> print height, width, channels
  600 800 3

In case you were working with binary images, img will have two dimensions, and therefore you must change the code to: height, width = img.shape

How to use a PHP class from another file?

You can use include/include_once or require/require_once


Alternatively, use autoloading by adding to page.php

function my_autoloader($class) {
    include 'classes/' . $class . '.class.php';


$vars = new IUarts(); 

It also works adding that __autoload function in a lib that you include on every file like utils.php.

There is also this post that has a nice and different approach.

Efficient PHP auto-loading and naming strategies

CSS Circle with border

Here is a jsfiddle so you can see an example of this working.

HTML code:

<div class="circle"></div>

CSS code:

.circle {_x000D_
        /*This creates a 1px solid red border around your element(div) */_x000D_
        border:1px solid red;_x000D_
        background-color: #FFFFFF;_x000D_
        height: 100px;_x000D_
        /* border-radius 50% will make it fully rounded. */_x000D_
        border-radius: 50%;_x000D_
        -webkit-border-radius: 50%;_x000D_
        width: 100px;_x000D_
<div class='circle'></div>

jQuery javascript regex Replace <br> with \n

Not really anything to do with jQuery, but if you want to trim a pattern from a string, then use a regular expression:

<textarea id="ta0"></textarea>
<button onclick="
  var ta = document.getElementById('ta0');
  var text = 'some<br>text<br />to<br/>replace';
  var re = /<br *\/?>/gi;
  ta.value = text.replace(re, '\n');
">Add stuff to text area</button>

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". in a Maven Project

I am assuming you are using Eclipse as your developing environment.

Eclipse Juno, Indigo and Kepler when using the bundled maven version(m2e), are not suppressing the message SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". This behaviour is present from the m2e version and onwards.

Although, this is indicated as an error your logs will be saved normally. The highlighted error will still be present until there is a fix of this bug. More about this in the m2e support site.

The current available solution is to use an external maven version rather than the bundled version of Eclipse. You can find about this solution and more details regarding this bug in the question below which i believe describes the same problem you are facing.

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". error

How to initailize byte array of 100 bytes in java with all 0's

A new byte array will automatically be initialized with all zeroes. You don't have to do anything.

The more general approach to initializing with other values, is to use the Arrays class.

import java.util.Arrays;

byte[] bytes = new byte[100];
Arrays.fill( bytes, (byte) 1 );

Difference between const reference and normal parameter

The first method passes n by value, i.e. a copy of n is sent to the function. The second one passes n by reference which basically means that a pointer to the n with which the function is called is sent to the function.

For integral types like int it doesn't make much sense to pass as a const reference since the size of the reference is usually the same as the size of the reference (the pointer). In the cases where making a copy is expensive it's usually best to pass by const reference.

'ssh-keygen' is not recognized as an internal or external command

Are you running msysgit, or some other form of Windows git installation? msysgit is only one possible way to run git on Windows but it's probably also the simplest one. It's also the way recommended by the git website at .

If you are using msysgit, then you need to run the command in Git Bash, not in a standard Windows command line prompt. Git Bash is a prompt that is installed for you by msysgit, and is basically the most common Linux command line shell (bash) packaged for Windows to facilitate command line usage of git. msysgit should also install the ssh-keygen program in a place where it is accessible from Git Bash, but not necessarily from your usual Windows command line prompt.

Bootstrap trying to load map file. How to disable it? Do I need to do it?

Remove the line /*# */ in bootstrap.css

If the error persists, clean the cache of the browser (CTRL + F5).

List all tables in postgresql information_schema

For private schema 'xxx' in postgresql :

SELECT table_name FROM information_schema.tables 
 WHERE table_schema = 'xxx' AND table_type = 'BASE TABLE'

Without table_type = 'BASE TABLE' , you will list tables and views

How do I manually create a file with a . (dot) prefix in Windows? For example, .htaccess

You could also use Command Prompt with move: move x.extension .extension

Is there a cross-browser onload event when clicking the back button?

jQuery's ready event was created for just this sort of issue. You may want to dig into the implementation to see what is going on under the covers.

SQL: sum 3 columns when one column has a null value?

If the column has a 0 value, you are fine, my guess is that you have a problem with a Null value, in that case you would need to use IsNull(Column, 0) to ensure it is always 0 at minimum.

Creating threads - Task.Factory.StartNew vs new Thread()

Your first block of code tells CLR to create a Thread (say. T) for you which is can be run as background (use thread pool threads when scheduling T ). In concise, you explicitly ask CLR to create a thread for you to do something and call Start() method on thread to start.

Your second block of code does the same but delegate (implicitly handover) the responsibility of creating thread (background- which again run in thread pool) and the starting thread through StartNew method in the Task Factory implementation.

This is a quick difference between given code blocks. Having said that, there are few detailed difference which you can google or see other answers from my fellow contributors.

What is the difference between "Rollback..." and "Back Out Submitted Changelist #####" in Perforce P4V

Both of these operations restore a set of files to a previous state and are essentially faster, safer ways of undoing mistakes than using the p4 obliterate command (and you don't need admin access to use them).

In the case of "Rollback...", this could be any number of files, even an entire depot. You can tell it to rollback to a specific revision, changelist, or label. The files are restored to the state they were in at the time of creation of that revision, changelist, or label.

In the case of "Back Out Submitted Changelist #####", the restore operation is restricted to the files that were submitted in changelist #####. Those files are restored to the state they were in before you submitted that changelist, provided no changes have been made to those files since. If subsequent changes have been made to any of those files, Perforce will tell you that those files are now out of date. You will have to sync to the head revision and then resolve the differences. This way you don't inadvertently clobber any changes that you actually want to keep.

Both operations work by essentially submitting old revisions as new revisions. When you perform a "Rollback...", you are restoring the files to the state they were in at a specific point in time, regardless of what has happened to them since. When you perform a "Back out...", you are attempting to undo the changes you made at a specific point in time, while maintaining the changes that have occurred since.

Difference between nVidia Quadro and Geforce cards?

I have read that while the underlying chips are essentially the same, the design of the board is different.

Gamers want performance, and tend to favor overclocking and other things to get high frame rates but which maybe burn out the hardware occasionally.

Businesses want reliability, and tend to favor underclocking so they can be sure that their people can keep working.

Also, I have read that the quadro boards use ECC memory.

If you don't know what ECC memory is about: it's a [relatively] well known fact that sometimes memory "flips bits (experiences errors)". This does not happen too often, but is an unavoidable consequence of the underlying physics of the memory cards and the world we live in. ECC memory adds a small percentage to the cost and a small penalty to the performance and has enough redundancy to correct occasional errors and to detect (but not correct) somewhat rarer errors. Gamers don't care about that kind of accuracy because for gamers those are just very rare visual glitches. Companies do care about that kind of accuracy because those glitches would wind up as glitches in their products or else would require more double or triple checking (which winds up being a 2x or 3x performance penalty for some part of their business).

Another issue I have read about has to do with hooking up the graphics card to third party hardware. In other words: sending the images to another card or to another machine instead of to the screen. Most gamers are just using canned software that doesn't have any use for such capabilities. Companies that use that kind of thing get orders of magnitude performance gains from the more direct connections.

Set value for particular cell in pandas DataFrame with iloc

Extending Jianxun's answer, using set_value mehtod in pandas. It sets value for a column at given index.

From pandas documentations:

DataFrame.set_value(index, col, value)

To set value at particular index for a column, do:

df.set_value(index, 'COL_NAME', x)

Hope it helps.

How do I use Wget to download all images into a single folder, from a URL?

wget utility retrieves files from World Wide Web (WWW) using widely used protocols like HTTP, HTTPS and FTP. Wget utility is freely available package and license is under GNU GPL License. This utility can be install any Unix-like Operating system including Windows and MAC OS. It’s a non-interactive command line tool. Main feature of Wget is it’s robustness. It’s designed in such way so that it works in slow or unstable network connections. Wget automatically start download where it was left off in case of network problem. Also downloads file recursively. It’ll keep trying until file has be retrieved completely.

Install wget in linux machine sudo apt-get install wget

Create a folder where you want to download files . sudo mkdir myimages cd myimages

Right click on the webpage and for example if you want image location right click on image and copy image location. If there are multiple images then follow the below:

If there are 20 images to download from web all at once, range starts from 0 to 19.


How can I create a product key for my C# application?

I have to admit I'd do something rather insane.

  1. Find a CPU bottleneck and extract it to a P/Invokeable DLL file.
  2. As a post build action, encrypt part of the DLL file with an XOR encryption key.
  3. Select a public/private key scheme, include public key in the DLL file
  4. Arrange so that decrypting the product key and XORing the two halves together results in the encryption key for the DLL.
  5. In the DLL's DllMain code, disable protection (PAGE_EXECUTE_READWRITE) and decrypt it with the key.
  6. Make a LicenseCheck() method that makes a sanity check of the license key and parameters, then checksums entire DLL file, throwing license violation on either. Oh, and do some other initialization here.

When they find and remove the LicenseCheck, what fun will follow when the DLL starts segmentation faulting.

How can I concatenate a string within a loop in JSTL/JSP?

Perhaps this will work?

<c:forEach items="${myParams.items}" var="currentItem" varStatus="stat">
  <c:set var="myVar" value="${stat.first ? '' : myVar} ${currentItem}" />

Calendar Recurring/Repeating Events - Best Storage Method

RRULE standard is built for exactly this requirement i.e. saving and understanding recurrences. Microsoft and google both use it in their calendar events. Please go through this document for more details.

How to determine the installed webpack version

webpack 4 now offers a version property that can be used!

Init method in Spring Controller (annotation version)

public class InitHelloWorld implements BeanPostProcessor {

   public Object postProcessBeforeInitialization(Object bean,
             String beanName) throws BeansException {
       System.out.println("BeforeInitialization : " + beanName);
       return bean;  // you can return any other object as well

   public Object postProcessAfterInitialization(Object bean,
             String beanName) throws BeansException {
       System.out.println("AfterInitialization : " + beanName);
       return bean;  // you can return any other object as well


Error: The 'brew link' step did not complete successfully

My problem had a slightly different solution. The directory in which brew wanted to create the symlinks were not owned by the current user.

ls -la /usr/local/bin/lib/node | grep node yielded:

drwxr-xr-x    3 24561  wheel   102 May  4  2012 node
drwxr-xr-x    7 24561  wheel   238 Sep 18 16:37 node_modules

For me, the following fixed it:

sudo chown $(users) /usr/local/bin/lib/node_modules
sudo chown $(users) /usr/local/bin/lib/node

ps. $(users) will get expanded to your username, went a little out of my way to help out lazy copy pasters ;)

How can I split a text into sentences?

Was working on similar task and came across this query, by following few links and working on few exercises for nltk the below code worked for me like magic.

from nltk.tokenize import sent_tokenize 
text = "Hello everyone. Welcome to GeeksforGeeks. You are studying NLP article"


['Hello everyone.',
 'Welcome to GeeksforGeeks.',
 'You are studying NLP article']


How to retrieve unique count of a field using Kibana + Elastic Search

Now Kibana 4 allows you to use aggregations. Apart from building a panel like the one that was explained in this answer for Kibana 3, now we can see the number of unique IPs in different periods, that was (IMO) what the OP wanted at the first place.

To build a dashboard like this you should go to Visualize -> Select your Index -> Select a Vertical Bar chart and then in the visualize panel:

  • In the Y axis we want the unique count of IPs (select the field where you stored the IP) and in the X axis we want a date histogram with our timefield.

Building a visualization

  • After pressing the Apply button, we should have a graph that shows the unique count of IP distributed on time. We can change the time interval on the X axis to see the unique IPs hourly/daily...

Final plot

Just take into account that the unique counts are approximate. For more information check also this answer.

Angular2 get clicked element id

If you want to have access to the id attribute of the button you can leverage the srcElement property of the event:

import {Component} from 'angular2/core';

  selector: 'my-app',
  template: `
    <button (click)="onClick($event)" id="test">Click</button>
export class AppComponent {
  onClick(event) {
    var target = || event.srcElement || event.currentTarget;
    var idAttr =;
    var value = idAttr.nodeValue;

See this plunkr:

See this question:

In, how to get the column names from a datatable

You can loop through the columns collection of the datatable.


Dim dt As New DataTable()
For Each column As DataColumn In dt.Columns


DataTable dt = new DataTable();
foreach (DataColumn column in dt.Columns)

Hope this helps!

With block equivalent in C#?

As the Visual C# Program Manager linked above says, there are limited situations where the With statement is more efficient, the example he gives when it is being used as a shorthand to repeatedly access a complex expression.

Using an extension method and generics you can create something that is vaguely equivalent to a With statement, by adding something like this:

    public static T With<T>(this T item, Action<T> action)
        return item;

Taking a simple example of how it could be used, using lambda syntax you can then use it to change something like this:

    updateRoleFamily.RoleFamilyDescription = roleFamilyDescription;
    updateRoleFamily.RoleFamilyCode = roleFamilyCode;

To this:

    updateRoleFamily.With(rf =>
              rf.RoleFamilyDescription = roleFamilyDescription;
              rf.RoleFamilyCode = roleFamilyCode;

On an example like this, the only advantage is perhaps a nicer layout, but with a more complex reference and more properties, it could well give you more readable code.

How do you hide the Address bar in Google Chrome for Chrome Apps?

On macs chrome browser:

1st toggle on Full screen:


2nd toggle on hide address bar, tabs and all

Just repeat to undo or hover above top


Undo by repeating backwards:

  • cmd-shift-f undo hide
  • cmd-ctrl-f undo full screen

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

you can do

strings test.log | grep -i

this will convert give output as a readable string to grep.

How to create streams from string in Node.Js?

Edit: Garth's answer is probably better.

My old answer text is preserved below.

To convert a string to a stream, you can use a paused through stream:

through().pause().queue('your string').end()


var through = require('through')

// Create a paused stream and buffer some data into it:
var stream = through().pause().queue('your string').end()

// Pass stream around:
callback(null, stream)

// Now that a consumer has attached, remember to resume the stream:

How to add an auto-incrementing primary key to an existing table, in PostgreSQL?

(Updated - Thanks to the people who commented)

Modern Versions of PostgreSQL

Suppose you have a table named test1, to which you want to add an auto-incrementing, primary-key id (surrogate) column. The following command should be sufficient in recent versions of PostgreSQL:


Older Versions of PostgreSQL

In old versions of PostgreSQL (prior to 8.x?) you had to do all the dirty work. The following sequence of commands should do the trick:

  ALTER TABLE test ALTER COLUMN id SET DEFAULT nextval('test_id_seq');
  UPDATE test1 SET id = nextval('test_id_seq');

Again, in recent versions of Postgres this is roughly equivalent to the single command above.

Check if key exists in JSON object using jQuery

if you have an array

var subcategories=[{name:"test",desc:"test"}];

function hasCategory(nameStr) {
        for(let i=0;i<subcategories.length;i++){
                return true;
        return false;

if you have an object

var category={name:"asd",test:""};

   return true;
   return false;

How to inject window into a service?

As of today (April 2016), the code in the previous solution doesn't work, I think it is possible to inject window directly into App.ts and then gather the values you need into a service for global access in the App, but if you prefer to create and inject your own service, a way simpler solution is this.

// Imports Section:
import {Injectable} from 'angular2/core'
import {window} from 'angular2/src/facade/browser';

// Service Class:
export class WindowService
    // Constructor Method Section:

    // Public Properties Section:
    get nativeWindow() : Window
        return window;

How to obfuscate Python code effectively?

The best way to do this is to first generate a .c file, and then compile it with tcc to a .pyd file
Note: Windows-only


  1. tcc
  2. pyobfuscate
  3. Cython


sudo pip install -U cython

To obfuscate your .py file: >

To generate a .c file,

  1. Add an init<filename>() function to your .py file Optional

  2. cython --embed

  3. cp Python.h tcc\include

  4. tcc file.c -o file.pyd -shared -I\path\to\Python\include -L\path\to\Python\lib

  5. import .pyd file into app.exe