Programs & Examples On #Php mode

How to Correctly handle Weak Self in Swift Blocks with Arguments

Swift 4.2

let closure = { [weak self] (_ parameter:Int) in
    guard let self = self else { return }


How to handle iframe in Selenium WebDriver using java

To get back to the parent frame, use:


To get back to the first/main frame, use:


how to run or install a *.jar file in windows?

To run usually click and it should run, that is if you have java installed. If not get java from here Sorry thought it was more general open a command prompt and type java -jar jbpm-installer-3.2.7.jar

How does the keyword "use" work in PHP and can I import classes with it?

use doesn't include anything. It just imports the specified namespace (or class) to the current scope

If you want the classes to be autoloaded - read about autoloading

"element.dispatchEvent is not a function" js error caught in firebug of FF3.0

check for this by calling the library jquery after the noconflict.js or that this calling more than once jquery library after the noconflict.js

Is there a command to undo git init?

Git keeps all of its files in the .git directory. Just remove that one and init again.

This post well show you how to find the hide .git file on Windows, Mac OSX, Ubuntu

Setting the JVM via the command line on Windows

You should be able to do this via the command line arguments, assuming these are Sun VMs installed using the usual Windows InstallShield mechanisms with the JVM finder EXE in system32.

Type java -help for the options. In particular, see:

              require the specified version to run
-jre-restrict-search | -jre-no-restrict-search
              include/exclude user private JREs in the version search

Clear listview content?

Simple its works me:)


How do I remove the passphrase for the SSH key without having to create a new key?

You might want to add the following to your .bash_profile (or equivalent), which starts ssh-agent on login.

if [ -f ~/.agent.env ] ; then
    . ~/.agent.env > /dev/null
    if ! kill -0 $SSH_AGENT_PID > /dev/null 2>&1; then
        echo "Stale agent file found. Spawning new agent… "
        eval `ssh-agent | tee ~/.agent.env`
    echo "Starting ssh-agent"
    eval `ssh-agent | tee ~/.agent.env`

On some Linux distros (Ubuntu, Debian) you can use:

ssh-copy-id -i ~/.ssh/ username@host

This will copy the generated id to a remote machine and add it to the remote keychain.

You can read more here and here.

Perl - Multiple condition if statement without duplicating code?

if (   ($name eq "tom" and $password eq "123!")
    or ($name eq "frank" and $password eq "321!")) {

    print "You have gained access.";
else {
    print "Access denied!";

What GRANT USAGE ON SCHEMA exactly do?

Well, this is my final solution for a simple db, for Linux:

# Read this before!
# * roles in postgres are users, and can be used also as group of users
# * $ROLE_LOCAL will be the user that access the db for maintenance and
#   administration. $ROLE_REMOTE will be the user that access the db from the webapp
# * you have to change '$ROLE_LOCAL', '$ROLE_REMOTE' and '$DB'
#   strings with your desired names
# * it's preferable that $ROLE_LOCAL == $DB



cd /etc/postgresql/$VERSION/main
sudo cp pg_hba.conf pg_hba.conf_bak
sudo -e pg_hba.conf

# change all `md5` with `scram-sha-256`
# save and exit


sudo -u postgres psql

# in psql:
create role $ROLE_LOCAL login createdb;
\password $ROLE_LOCAL
create role $ROLE_REMOTE login;
\password $ROLE_REMOTE

create database $DB owner $ROLE_LOCAL encoding "utf8";
\connect $DB $ROLE_LOCAL

# Create all tables and objects, and after that:

\connect $DB postgres

revoke connect on database $DB from public;
revoke all on schema public from public;
revoke all on all tables in schema public from public;

grant connect on database $DB to $ROLE_LOCAL;
grant all on schema public to $ROLE_LOCAL;
grant all on all tables in schema public to $ROLE_LOCAL;
grant all on all sequences in schema public to $ROLE_LOCAL;
grant all on all functions in schema public to $ROLE_LOCAL;

grant connect on database $DB to $ROLE_REMOTE;
grant usage on schema public to $ROLE_REMOTE;
grant select, insert, update, delete on all tables in schema public to $ROLE_REMOTE;
grant usage, select on all sequences in schema public to $ROLE_REMOTE;
grant execute on all functions in schema public to $ROLE_REMOTE;

alter default privileges for role $ROLE_LOCAL in schema public
    grant all on tables to $ROLE_LOCAL;

alter default privileges for role $ROLE_LOCAL in schema public
    grant all on sequences to $ROLE_LOCAL;

alter default privileges for role $ROLE_LOCAL in schema public
    grant all on functions to $ROLE_LOCAL;

alter default privileges for role $ROLE_REMOTE in schema public
    grant select, insert, update, delete on tables to $ROLE_REMOTE;

alter default privileges for role $ROLE_REMOTE in schema public
    grant usage, select on sequences to $ROLE_REMOTE;

alter default privileges for role $ROLE_REMOTE in schema public
    grant execute on functions to $ROLE_REMOTE;


How can I get all a form's values that would be submitted without submitting

Depending on the type of input types you're using on your form, you should be able to grab them using standard jQuery expressions.


// change forms[0] to the form you're trying to collect elements from...  or remove it, if you need all of them
var input_elements = $("input, textarea", document.forms[0]);

Check out the documentation for jQuery expressions on their site for more info:

How do I use select with date condition?

Another feature is between:

Select * from table where date between '2009/01/30' and '2009/03/30'

How to capture a list of specific type with mockito

Yeah, this is a general generics problem, not mockito-specific.

There is no class object for ArrayList<SomeType>, and thus you can't type-safely pass such an object to a method requiring a Class<ArrayList<SomeType>>.

You can cast the object to the right type:

Class<ArrayList<SomeType>> listClass =
ArgumentCaptor<ArrayList<SomeType>> argument = ArgumentCaptor.forClass(listClass);

This will give some warnings about unsafe casts, and of course your ArgumentCaptor can't really differentiate between ArrayList<SomeType> and ArrayList<AnotherType> without maybe inspecting the elements.

(As mentioned in the other answer, while this is a general generics problem, there is a Mockito-specific solution for the type-safety problem with the @Captor annotation. It still can't distinguish between an ArrayList<SomeType> and an ArrayList<OtherType>.)


Take also a look at tenshis comment. You can change the original code from Paulo Ebermann to this (much simpler)

final ArgumentCaptor<List<SomeType>> listCaptor
        = ArgumentCaptor.forClass((Class) List.class);

MongoDB: exception in initAndListen: 20 Attempted to create a lock file on a read-only directory: /data/db, terminating

If you do not need to have the database directories in root, you can create data/db in your home directory (mkdir -p ~/data/db).

Then you can start the MongoDB server with the --dbpath option:

mongod --dbpath=$(echo ~)/data/db

(This is assuming you're starting it from a terminal. For some strange reason, mongod does not accept ~ as the home directory path, hence the bash echo substitution trickery, you may as well write /home/yourusername/data/db)

In fact, it does not have to be ~/data/db, it can be anywhere you want and this way you can have multiple database paths and organize everything nicely. May not be the best option for production (depending on what you want to do), but for developing works fine.

Does WhatsApp offer an open API?

1) It looks possible. This info on Github describes how to create a java program to send a message using the whatsapp encryption protocol from WhisperSystems.

2) No. See the whatsapp security white paper.

3) See #1.

Displaying the Error Messages in Laravel after being Redirected from controller

to Make it look nice you can use little bootstrap help

@if(count($errors) > 0 )
<div class="alert alert-danger alert-dismissible fade show" role="alert">
    <button type="button" class="close" data-dismiss="alert" aria-label="Close">
        <span aria-hidden="true">&times;</span>
    <ul class="p-0 m-0" style="list-style: none;">
        @foreach($errors->all() as $error)

In git how is fetch different than pull and how is merge different than rebase?

pull vs fetch:

The way I understand this, is that git pull is simply a git fetch followed by git merge. I.e. you fetch the changes from a remote branch and then merge it into the current branch.

merge vs rebase:

A merge will do as the command says; merge the differences between current branch and the specified branch (into the current branch). I.e. the command git merge another_branch will the merge another_branch into the current branch.

A rebase works a bit differently and is kind of cool. Let's say you perform the command git rebase another_branch. Git will first find the latest common version between the current branch and another_branch. I.e. the point before the branches diverged. Then git will move this divergent point to the head of the another_branch. Finally, all the commits in the current branch since the original divergent point are replayed from the new divergent point. This creates a very clean history, with fewer branches and merges.

However, it is not without pitfalls! Since the version history is "rewritten", you should only do this if the commits only exists in your local git repo. That is: Never do this if you have pushed the commits to a remote repo.

The explanation on rebasing given in this online book is quite good, with easy-to-understand illustrations.

pull with rebasing instead of merge

I'm actually using rebase quite a lot, but usually it is in combination with pull:

git pull --rebase

will fetch remote changes and then rebase instead of merge. I.e. it will replay all your local commits from the last time you performed a pull. I find this much cleaner than doing a normal pull with merging, which will create an extra commit with the merges.

MySQL: Insert record if not exists in table

Worked :

INSERT INTO users (full_name, login, password) 
  SELECT 'Mahbub Tito','tito',SHA1('12345') FROM DUAL
  (SELECT login FROM users WHERE login='tito');

Free Online Team Foundation Server

VSO is now Azure DevOps

Recently Microsoft Visual Studio Online (VSO) is now Azure DevOps

How to add checkboxes to JTABLE swing

1) JTable knows JCheckbox with built-in Boolean TableCellRenderers and TableCellEditor by default, then there is contraproductive declare something about that,

2) AbstractTableModel should be useful, where is in the JTable required to reduce/restrict/change nested and inherits methods by default implemented in the DefaultTableModel,

3) consider using DefaultTableModel, (if you are not sure about how to works) instead of AbstractTableModel,


could be generated from simple code:

import javax.swing.*;
import javax.swing.table.*;

public class TableCheckBox extends JFrame {

    private static final long serialVersionUID = 1L;
    private JTable table;

    public TableCheckBox() {
        Object[] columnNames = {"Type", "Company", "Shares", "Price", "Boolean"};
        Object[][] data = {
            {"Buy", "IBM", new Integer(1000), new Double(80.50), false},
            {"Sell", "MicroSoft", new Integer(2000), new Double(6.25), true},
            {"Sell", "Apple", new Integer(3000), new Double(7.35), true},
            {"Buy", "Nortel", new Integer(4000), new Double(20.00), false}
        DefaultTableModel model = new DefaultTableModel(data, columnNames);
        table = new JTable(model) {

            private static final long serialVersionUID = 1L;

            public Class getColumnClass(int column) {
            return getValueAt(0, column).getClass();
            public Class getColumnClass(int column) {
                switch (column) {
                    case 0:
                        return String.class;
                    case 1:
                        return String.class;
                    case 2:
                        return Integer.class;
                    case 3:
                        return Double.class;
                        return Boolean.class;
        JScrollPane scrollPane = new JScrollPane(table);

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                TableCheckBox frame = new TableCheckBox();
                frame.setLocation(150, 150);

.NET data structures: ArrayList, List, HashTable, Dictionary, SortedList, SortedDictionary -- Speed, memory, and when to use each?

I found "Choose a Collection" section of Microsoft Docs on Collection and Data Structure page really useful

C# Collections and Data Structures : Choose a collection

enter image description here

And also the following matrix to compare some other features

enter image description here

onchange event for html.dropdownlist

You can try this if you are passing a value to the action method.

@Html.DropDownList("Sortby", new SelectListItem[] { new SelectListItem() { Text = "Newest to Oldest", Value = "0" }, new SelectListItem() { Text = "Oldest to Newest", Value = "1" }},new { onchange = "document.location.href = '/ControllerName/ActionName?id=' + this.options[this.selectedIndex].value;" })

Remove the query string in case of no parameter passing.

Submit form with Enter key without submit button?

$("input").keypress(function(event) {
    if (event.which == 13) {

How to use JNDI DataSource provided by Tomcat in Spring?

If using Spring's XML schema based configuration, setup in the Spring context like this:

<beans xmlns=""
  xmlns:jee="" xsi:schemaLocation="">
<jee:jndi-lookup id="dbDataSource"
   expected-type="javax.sql.DataSource" />

Alternatively, setup using simple bean configuration like this:

<bean id="DatabaseName" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="java:comp/env/jdbc/DatabaseName"/>

You can declare the JNDI resource in tomcat's server.xml using something like this:

    <Resource name="jdbc/DatabaseName"
              validationQuery="select 1"

And reference the JNDI resource from Tomcat's web context.xml like this:

  <ResourceLink name="jdbc/DatabaseName"

Reference documentation:

Edit: This answer has been updated for Tomcat 8 and Spring 4. There have been a few property name changes for Tomcat's default datasource resource pool setup.

Calculating the SUM of (Quantity*Price) from 2 different tables

I had the same problem as Marko and come across a solution like this:

/*Create a Table*/
CREATE TABLE tableGrandTotal
columnGrandtotal int

/*Create a Stored Procedure*/

/*Delete the 'tableGrandTotal' table for another usage of the stored procedure*/
DROP TABLE tableGrandTotal

/*Create a new Table which will include just one column*/
CREATE TABLE tableGrandTotal
columnGrandtotal int

/*Insert the query which returns subtotal for each orderitem row into tableGrandTotal*/
INSERT INTO tableGrandTotal
    SELECT oi.Quantity * p.Price AS columnGrandTotal
        FROM OrderItem oi
        JOIN Product p ON oi.Id = p.Id

/*And return the sum of columnGrandTotal from the newly created table*/    
SELECT SUM(columnGrandTotal) as [Grand Total]
    FROM tableGrandTotal

And just simply use the GetGrandTotal Stored Procedure to retrieve the Grand Total :)

EXEC GetGrandTotal

Does :before not work on img elements?

Try ::after on previous element.

Not Equal to This OR That in Lua

Your problem stems from a misunderstanding of the or operator that is common to people learning programming languages like this. Yes, your immediate problem can be solved by writing x ~= 0 and x ~= 1, but I'll go into a little more detail about why your attempted solution doesn't work.

When you read x ~=(0 or 1) or x ~= 0 or 1 it's natural to parse this as you would the sentence "x is not equal to zero or one". In the ordinary understanding of that statement, "x" is the subject, "is not equal to" is the predicate or verb phrase, and "zero or one" is the object, a set of possibilities joined by a conjunction. You apply the subject with the verb to each item in the set.

However, Lua does not parse this based on the rules of English grammar, it parses it in binary comparisons of two elements based on its order of operations. Each operator has a precedence which determines the order in which it will be evaluated. or has a lower precedence than ~=, just as addition in mathematics has a lower precedence than multiplication. Everything has a lower precedence than parentheses.

As a result, when evaluating x ~=(0 or 1), the interpreter will first compute 0 or 1 (because of the parentheses) and then x ~= the result of the first computation, and in the second example, it will compute x ~= 0 and then apply the result of that computation to or 1.

The logical operator or "returns its first argument if this value is different from nil and false; otherwise, or returns its second argument". The relational operator ~= is the inverse of the equality operator ==; it returns true if its arguments are different types (x is a number, right?), and otherwise compares its arguments normally.

Using these rules, x ~=(0 or 1) will decompose to x ~= 0 (after applying the or operator) and this will return 'true' if x is anything other than 0, including 1, which is undesirable. The other form, x ~= 0 or 1 will first evaluate x ~= 0 (which may return true or false, depending on the value of x). Then, it will decompose to one of false or 1 or true or 1. In the first case, the statement will return 1, and in the second case, the statement will return true. Because control structures in Lua only consider nil and false to be false, and anything else to be true, this will always enter the if statement, which is not what you want either.

There is no way that you can use binary operators like those provided in programming languages to compare a single variable to a list of values. Instead, you need to compare the variable to each value one by one. There are a few ways to do this. The simplest way is to use De Morgan's laws to express the statement 'not one or zero' (which can't be evaluated with binary operators) as 'not one and not zero', which can trivially be written with binary operators:

if x ~= 1 and x ~= 0 then
    print( "X must be equal to 1 or 0" )

Alternatively, you can use a loop to check these values:

local x_is_ok = false
for i = 0,1 do 
    if x == i then
        x_is_ok = true
if not x_is_ok then
    print( "X must be equal to 1 or 0" )

Finally, you could use relational operators to check a range and then test that x was an integer in the range (you don't want 0.5, right?)

if not (x >= 0 and x <= 1 and math.floor(x) == x) then
    print( "X must be equal to 1 or 0" )

Note that I wrote x >= 0 and x <= 1. If you understood the above explanation, you should now be able to explain why I didn't write 0 <= x <= 1, and what this erroneous expression would return!

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

What if you want to do a comparison for values that ARE NOT equal? Just using a "NOT" in front of the previously mentioned comparisons does not work. The best I could come up with is:

(Field1 <> Field2) OR (NULLIF(Field1, Field2) IS NOT NULL) OR (NULLIF(Field2, Field1) IS NOT NULL)

How to POST form data with Spring RestTemplate?

How to POST mixed data: File, String[], String in one request.

You can use only what you need.

private String doPOST(File file, String[] array, String name) {
    RestTemplate restTemplate = new RestTemplate(true);

    //add file
    LinkedMultiValueMap<String, Object> params = new LinkedMultiValueMap<>();
    params.add("file", new FileSystemResource(file));

    //add array
    UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl("https://my_url");
    for (String item : array) {
        builder.queryParam("array", item);

    //add some String
    builder.queryParam("name", name);

    //another staff
    String result = "";
    HttpHeaders headers = new HttpHeaders();

    HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity =
            new HttpEntity<>(params, headers);

    ResponseEntity<String> responseEntity =

    HttpStatus statusCode = responseEntity.getStatusCode();
    if (statusCode == HttpStatus.ACCEPTED) {
        result = responseEntity.getBody();
    return result;

The POST request will have File in its Body and next structure:

POST https://my_url?array=your_value1&array=your_value2&name=bob 

How to Change Font Size in drawString Java

code example below:

g.setFont(new Font("TimesRoman", Font.PLAIN, 30));
g.drawString("Welcome to the Java Applet", 20 , 20);

How do I add comments to package.json for npm install?

As duplicate comment keys are removed running package.json tools (npm, yarn, etc.), I came to using a hashed version which allows for better reading as multiple lines and keys like:

"//": {
  "alpaca": "we use the bootstrap version",
  "eonasdan-bootstrap-datetimepicker": "instead of bootstrap-datetimepicker",
  "moment-with-locales": "is part of moment"

which is 'valid' according to my IDE as a root key, but within dependencies it complains expecting a string value.

HttpClient won't import in Android Studio

HttpClient was deprecated in API Level 22 and removed in API Level 23. You can still use it in API Level 23 and onwards if you must, however it is best to move to supported methods to handle HTTP. So, if you're compiling with 23, add this in your build.gradle:

android {
    useLibrary 'org.apache.http.legacy'

Sorting A ListView By Column

My solution is a class to sort listView items when you click on column header.

You can specify the type of each column.

listView.ListViewItemSorter = new ListViewColumnSorter();
listView.ListViewItemSorter.ColumnsTypeComparer.Add(0, DateTime);
listView.ListViewItemSorter.ColumnsTypeComparer.Add(1, int);

That's it !

The C# class :

using System.Collections;
using System.Collections.Generic;
using EDV;

namespace System.Windows.Forms
    /// <summary>
    /// Cette classe est une implémentation de l'interface 'IComparer' pour le tri des items de ListView. Adapté de
    /// </summary>
    /// <remarks>Intégré par EDVariables.</remarks>
    public class ListViewColumnSorter : IComparer
        /// <summary>
        /// Spécifie la colonne à trier
        /// </summary>
        private int ColumnToSort;
        /// <summary>
        /// Spécifie l'ordre de tri (en d'autres termes 'Croissant').
        /// </summary>
        private SortOrder OrderOfSort;
        /// <summary>
        /// Objet de comparaison ne respectant pas les majuscules et minuscules
        /// </summary>
        private CaseInsensitiveComparer ObjectCompare;

        /// <summary>
        /// Constructeur de classe.  Initialise la colonne sur '0' et aucun tri
        /// </summary>
        public ListViewColumnSorter()
            : this(0, SortOrder.None) { }

        /// <summary>
        /// Constructeur de classe.  Initializes various elements
        /// <param name="columnToSort">Spécifie la colonne à trier</param>
        /// <param name="orderOfSort">Spécifie l'ordre de tri</param>
        /// </summary>
        public ListViewColumnSorter(int columnToSort, SortOrder orderOfSort)
            // Initialise la colonne
            ColumnToSort = columnToSort;

            // Initialise l'ordre de tri
            OrderOfSort = orderOfSort;

            // Initialise l'objet CaseInsensitiveComparer
            ObjectCompare = new CaseInsensitiveComparer();

            // Dictionnaire de comparateurs
            ColumnsComparer = new Dictionary<int, IComparer>();
            ColumnsTypeComparer = new Dictionary<int, Type>();


        /// <summary>
        /// Cette méthode est héritée de l'interface IComparer.  Il compare les deux objets passés en effectuant une comparaison 
        ///qui ne tient pas compte des majuscules et des minuscules.
        /// <br/>Si le comparateur n'existe pas dans ColumnsComparer, CaseInsensitiveComparer est utilisé.
        /// </summary>
        /// <param name="x">Premier objet à comparer</param>
        /// <param name="x">Deuxième objet à comparer</param>
        /// <returns>Le résultat de la comparaison. "0" si équivalent, négatif si 'x' est inférieur à 'y' 
        ///et positif si 'x' est supérieur à 'y'</returns>
        public int Compare(object x, object y)
            int compareResult;
            ListViewItem listviewX, listviewY;

            // Envoit les objets à comparer aux objets ListViewItem
            listviewX = (ListViewItem)x;
            listviewY = (ListViewItem)y;

            if (listviewX.SubItems.Count < ColumnToSort + 1 || listviewY.SubItems.Count < ColumnToSort + 1)
                return 0;

            IComparer objectComparer = null;
            Type comparableType = null;
            if (ColumnsComparer == null || !ColumnsComparer.TryGetValue(ColumnToSort, out objectComparer))
                if (ColumnsTypeComparer == null || !ColumnsTypeComparer.TryGetValue(ColumnToSort, out comparableType))
                    objectComparer = ObjectCompare;

            // Compare les deux éléments
            if (comparableType != null) {
                //Conversion du type
                object valueX = listviewX.SubItems[ColumnToSort].Text;
                object valueY = listviewY.SubItems[ColumnToSort].Text;
                if (!edvTools.TryParse(ref valueX, comparableType) || !edvTools.TryParse(ref valueY, comparableType))
                    return 0;
                compareResult = (valueX as IComparable).CompareTo(valueY);
                compareResult = objectComparer.Compare(listviewX.SubItems[ColumnToSort].Text, listviewY.SubItems[ColumnToSort].Text);

            // Calcule la valeur correcte d'après la comparaison d'objets
            if (OrderOfSort == SortOrder.Ascending) {
                // Le tri croissant est sélectionné, renvoie des résultats normaux de comparaison
                return compareResult;
            else if (OrderOfSort == SortOrder.Descending) {
                // Le tri décroissant est sélectionné, renvoie des résultats négatifs de comparaison
                return (-compareResult);
            else {
                // Renvoie '0' pour indiquer qu'ils sont égaux
                return 0;

        /// <summary>
        /// Obtient ou définit le numéro de la colonne à laquelle appliquer l'opération de tri (par défaut sur '0').
        /// </summary>
        public int SortColumn
                ColumnToSort = value;
                return ColumnToSort;

        /// <summary>
        /// Obtient ou définit l'ordre de tri à appliquer (par exemple, 'croissant' ou 'décroissant').
        /// </summary>
        public SortOrder Order
                OrderOfSort = value;
                return OrderOfSort;

        /// <summary>
        /// Dictionnaire de comparateurs par colonne.
        /// <br/>Pendant le tri, si le comparateur n'existe pas dans ColumnsComparer, CaseInsensitiveComparer est utilisé.
        /// </summary>
        public Dictionary<int, IComparer> ColumnsComparer { get; set; }

        /// <summary>
        /// Dictionnaire de comparateurs par colonne.
        /// <br/>Pendant le tri, si le comparateur n'existe pas dans ColumnsTypeComparer, CaseInsensitiveComparer est utilisé.
        /// </summary>
        public Dictionary<int, Type> ColumnsTypeComparer { get; set; }

Initializing a ListView :

    <var>Visual.WIN.ctrlListView.OnShown</var>  : 
    eventSender.SmallImageList = edvWinForm.ImageList16;
    eventSender.ListViewItemSorter = new ListViewColumnSorter();
    var col = eventSender.Columns.Add("Répertoire");
    col.Width = 160;
    col.ImageKey = "Domain";
    col = eventSender.Columns.Add("Fichier");
    col.Width = 180;
    col.ImageKey = "File";
    col = eventSender.Columns.Add("Date");
    col.Width = 120;
    col.ImageKey = "DateTime";
    eventSender.ListViewItemSorter.ColumnsTypeComparer.Add(col.Index, DateTime);
    col = eventSender.Columns.Add("Position");
    col.TextAlign = HorizontalAlignment.Right;
    col.Width = 80;
    col.ImageKey = "Num";
    eventSender.ListViewItemSorter.ColumnsTypeComparer.Add(col.Index, Int32);

Fill a ListView :

<var>Visual.WIN.cmdSearch.OnClick</var>  : 
//non récursif et sans fonction
    ..ctrlListView:Sorting = SortOrder.None;
    var group = ..ctrlListView:Groups.Add(DateTime.Now.ToString()
                , Path.Combine(..cboDir:Text, ..ctrlPattern1:Text) + " contenant " + ..ctrlSearch1:Text);
    var perf =  Environment.TickCount;

    var files = new DirectoryInfo(..cboDir:Text).GetFiles(..ctrlPattern1:Text)
    var search = ..ctrlSearch1:Text;
    var ignoreCase = ..Search.IgnoreCase;
    //var result = new StringBuilder();
    var dirLength : int = ..cboDir:Text.Length;
    var position : int;
    var added : int = 0;
    for(var i : int = 0; i &lt; files.Length; i++){
        var file = files[i];
        if(search == ""
        || (position = File.ReadAllText(file.FullName).IndexOf(String(search)
                            , StringComparison(ignoreCase ? StringComparison.InvariantCultureIgnoreCase : StringComparison.InvariantCulture))) &gt; =0) {

        //  result.AppendLine(file.FullName.Substring(dirLength) + "\tPos : " + pkvFile.Value);
            var item = ..ctrlListView:Items.Add(file.FullName.Substring(dirLength));
            item.SubItems.Add(position.ToString("# ### ##0"));
            item.Group = group;
    group.Header += " : " + added + "/" + files.Length + " fichier(s)"
                + "  en " + (Environment.TickCount - perf).ToString("# ##0 msec");

On ListView column click :

<var>Visual.WIN.ctrlListView.OnColumnClick</var>  : 
// Déterminer si la colonne sélectionnée est déjà la colonne triée.
var sorter = eventSender.ListViewItemSorter;
if ( eventArgs.Column == sorter .SortColumn )
    // Inverser le sens de tri en cours pour cette colonne.
    if (sorter.Order == SortOrder.Ascending)
        sorter.Order = SortOrder.Descending;
        sorter.Order = SortOrder.Ascending;
    // Définir le numéro de colonne à trier ; par défaut sur croissant.
    sorter.SortColumn = eventArgs.Column;
    sorter.Order = SortOrder.Ascending;

// Procéder au tri avec les nouvelles options.

Function edvTools.TryParse used above

class edvTools {
    /// <summary>
    /// Tente la conversion d'une valeur suivant un type EDVType
    /// </summary>
    /// <param name="pValue">Référence de la valeur à convertir</param>
    /// <param name="pType">Type EDV en sortie</param>
    /// <returns></returns>
    public static bool TryParse(ref object pValue, System.Type pType)
        int lIParsed;
        double lDParsed;
        string lsValue;
        if (pValue == null) return false;
        if (pType.Equals(typeof(bool))) {
            bool lBParsed;
            if (pValue is bool) return true;
            if (double.TryParse(pValue.ToString(), out lDParsed)) {
                pValue = lDParsed != 0D;
                return true;
            if (bool.TryParse(pValue.ToString(), out lBParsed)) {
                pValue = lBParsed;
                return true;
                return false;
        if (pType.Equals(typeof(Double))) {
            if (pValue is Double) return true;
            if (double.TryParse(pValue.ToString(), out lDParsed)
                || double.TryParse(pValue.ToString().Replace(NumberDecimalSeparatorNOT, NumberDecimalSeparator), out lDParsed)) {
                pValue = lDParsed;
                return true;
                return false;
        if (pType.Equals(typeof(int))) {
            if (pValue is int) return true;
            if (Int32.TryParse(pValue.ToString(), out lIParsed)) {
                pValue = lIParsed;
                return true;
            else if (double.TryParse(pValue.ToString(), out lDParsed)) {
                pValue = (int)lDParsed;
                return true;
                return false;
        if (pType.Equals(typeof(Byte))) {
            if (pValue is byte) return true;
            byte lByte;
            if (Byte.TryParse(pValue.ToString(), out lByte)) {
                pValue = lByte;
                return true;
            else if (double.TryParse(pValue.ToString(), out lDParsed)) {
                pValue = (byte)lDParsed;
                return true;
                return false;
        if (pType.Equals(typeof(long))) {
            long lLParsed;
            if (pValue is long) return true;
            if (long.TryParse(pValue.ToString(), out lLParsed)) {
                pValue = lLParsed;
                return true;
            else if (double.TryParse(pValue.ToString(), out lDParsed)) {
                pValue = (long)lDParsed;
                return true;
                return false;
        if (pType.Equals(typeof(Single))) {
            if (pValue is float) return true;
            Single lSParsed;
            if (Single.TryParse(pValue.ToString(), out lSParsed)
                || Single.TryParse(pValue.ToString().Replace(NumberDecimalSeparatorNOT, NumberDecimalSeparator), out lSParsed)) {
                pValue = lSParsed;
                return true;
                return false;
        if (pType.Equals(typeof(DateTime))) {
            if (pValue is DateTime) return true;
            DateTime lDTParsed;
            if (DateTime.TryParse(pValue.ToString(), out lDTParsed)) {
                pValue = lDTParsed;
                return true;
            else if (pValue.ToString().Contains("UTC")) //Date venant de JScript
                if (_MonthsUTC == null) InitMonthsUTC();
                string[] lDateParts = pValue.ToString().Split(' ');
                lDTParsed = new DateTime(int.Parse(lDateParts[5]), _MonthsUTC[lDateParts[1]], int.Parse(lDateParts[2]));
                lDateParts = lDateParts[3].ToString().Split(':');
                pValue = lDTParsed.AddSeconds(int.Parse(lDateParts[0]) * 3600 + int.Parse(lDateParts[1]) * 60 + int.Parse(lDateParts[2]));
                return true;
                return false;

        if (pType.Equals(typeof(Array))) {
            if (pValue is System.Collections.ICollection || pValue is System.Collections.ArrayList)
                return true;
            return pValue is System.Data.DataTable
                || pValue is string && (pValue as string).StartsWith("<");
        if (pType.Equals(typeof(DataTable))) {
            return pValue is System.Data.DataTable
                || pValue is string && (pValue as string).StartsWith("<");

        if (pType.Equals(typeof(System.Drawing.Bitmap))) {
            return pValue is System.Drawing.Image || pValue is byte[];

        if (pType.Equals(typeof(System.Drawing.Image))) {
            return pValue is System.Drawing.Image || pValue is byte[];

        if (pType.Equals(typeof(System.Drawing.Color))) {
            if (pValue is System.Drawing.Color) return true;
            if (pValue is System.Drawing.KnownColor) {
                pValue = System.Drawing.Color.FromKnownColor((System.Drawing.KnownColor)pValue);
                return true;

            int lARGB;
            if (!int.TryParse(lsValue = pValue.ToString(), out lARGB)) {
                if (lsValue.StartsWith("Color [A=", StringComparison.InvariantCulture)) {
                    foreach (string lsARGB in lsValue.Substring("Color [".Length, lsValue.Length - "Color []".Length).Split(','))
                        switch (lsARGB.TrimStart().Substring(0, 1)) {
                            case "A":
                                lARGB = int.Parse(lsARGB.Substring(2)) * 0x1000000;
                            case "R":
                                lARGB += int.Parse(lsARGB.TrimStart().Substring(2)) * 0x10000;
                            case "G":
                                lARGB += int.Parse(lsARGB.TrimStart().Substring(2)) * 0x100;
                            case "B":
                                lARGB += int.Parse(lsARGB.TrimStart().Substring(2));
                    pValue = System.Drawing.Color.FromArgb(lARGB);
                    return true;
                if (lsValue.StartsWith("Color [", StringComparison.InvariantCulture)) {
                    pValue = System.Drawing.Color.FromName(lsValue.Substring("Color [".Length, lsValue.Length - "Color []".Length));
                    return true;
                return false;
            pValue = System.Drawing.Color.FromArgb(lARGB);
            return true;
        if (pType.IsEnum) {
            try {
                if (pValue == null) return false;
                if (pValue is int || pValue is byte || pValue is ulong || pValue is long || pValue is double)
                    pValue = Enum.ToObject(pType, pValue);
                    pValue = Enum.Parse(pType, pValue.ToString());
            catch {
                return false;
        return true;

Simplest/cleanest way to implement a singleton in JavaScript

function Unicode()
  var i = 0, unicode = {}, zero_padding = "0000", max = 9999;

  // Loop through code points
  while (i < max) {
    // Convert decimal to hex value, find the character,
    // and then pad zeroes to the code point
    unicode[String.fromCharCode(parseInt(i, 16))] = ("u" + zero_padding + i).substr(-4);
    i = i + 1;

  // Replace this function with the resulting lookup table
  Unicode = unicode;

// Usage

// Lookup
Unicode["%"]; // Returns 0025

"import datetime" v.s. "from datetime import datetime"

try this:

import datetime
from datetime import datetime as dt

today_date =
date_time = dt.strptime(date_time_string, '%Y-%m-%d %H:%M')

strp() doesn't exist. I think you mean strptime.

Prevent text selection after double click

To prevent text selection ONLY after a double click:

You could use MouseEvent#detail property. For mousedown or mouseup events, it is 1 plus the current click count.

document.addEventListener('mousedown', function (event) {
  if (event.detail > 1) {
    // of course, you still do not know what you prevent here...
    // You could also check event.ctrlKey/event.shiftKey/event.altKey
    // to not prevent something useful.
}, false);


Ignore case in Python strings

You could subclass str and create your own case-insenstive string class but IMHO that would be extremely unwise and create far more trouble than it's worth.

PDF to image using Java

Apache PDF Box can convert PDFs to jpg,bmp,wbmp,png, and gif.

The library even comes with a command line utility called PDFToImage to do this.

If you download the source code and look at the PDFToImage class you should be able to figure out how to use PDF Box to convert PDFs to images from your own Java code.

Lambda function in list comprehensions

This question touches a very stinking part of the "famous" and "obvious" Python syntax - what takes precedence, the lambda, or the for of list comprehension.

I don't think the purpose of the OP was to generate a list of squares from 0 to 9. If that was the case, we could give even more solutions:

squares = []
for x in range(10): squares.append(x*x)
  • this is the good ol' way of imperative syntax.

But it's not the point. The point is W(hy)TF is this ambiguous expression so counter-intuitive? And I have an idiotic case for you at the end, so don't dismiss my answer too early (I had it on a job interview).

So, the OP's comprehension returned a list of lambdas:

[(lambda x: x*x) for x in range(10)]

This is of course just 10 different copies of the squaring function, see:

>>> [lambda x: x*x for _ in range(3)]
[<function <lambda> at 0x00000000023AD438>, <function <lambda> at 0x00000000023AD4A8>, <function <lambda> at 0x00000000023AD3C8>]

Note the memory addresses of the lambdas - they are all different!

You could of course have a more "optimal" (haha) version of this expression:

>>> [lambda x: x*x] * 3
[<function <lambda> at 0x00000000023AD2E8>, <function <lambda> at 0x00000000023AD2E8>, <function <lambda> at 0x00000000023AD2E8>]

See? 3 time the same lambda.

Please note, that I used _ as the for variable. It has nothing to do with the x in the lambda (it is overshadowed lexically!). Get it?

I'm leaving out the discussion, why the syntax precedence is not so, that it all meant:

[lambda x: (x*x for x in range(10))]

which could be: [[0, 1, 4, ..., 81]], or [(0, 1, 4, ..., 81)], or which I find most logical, this would be a list of 1 element - a generator returning the values. It is just not the case, the language doesn't work this way.

BUT What, If...

What if you DON'T overshadow the for variable, AND use it in your lambdas???

Well, then crap happens. Look at this:

[lambda x: x * i for i in range(4)]

this means of course:

[(lambda x: x * i) for i in range(4)]

BUT it DOESN'T mean:

[(lambda x: x * 0), (lambda x: x * 1), ... (lambda x: x * 3)]

This is just crazy!

The lambdas in the list comprehension are a closure over the scope of this comprehension. A lexical closure, so they refer to the i via reference, and not its value when they were evaluated!

So, this expression:

[(lambda x: x * i) for i in range(4)]

IS roughly EQUIVALENT to:

[(lambda x: x * 3), (lambda x: x * 3), ... (lambda x: x * 3)]

I'm sure we could see more here using a python decompiler (by which I mean e.g. the dis module), but for Python-VM-agnostic discussion this is enough. So much for the job interview question.

Now, how to make a list of multiplier lambdas, which really multiply by consecutive integers? Well, similarly to the accepted answer, we need to break the direct tie to i by wrapping it in another lambda, which is getting called inside the list comprehension expression:


>>> a = [(lambda x: x * i) for i in (1, 2)]
>>> a[1](1)
>>> a[0](1)


>>> a = [(lambda y: (lambda x: y * x))(i) for i in (1, 2)]
>>> a[1](1)
>>> a[0](1)

(I had the outer lambda variable also = i, but I decided this is the clearer solution - I introduced y so that we can all see which witch is which).

Edit 2019-08-30:

Following a suggestion by @josoler, which is also present in an answer by @sheridp - the value of the list comprehension "loop variable" can be "embedded" inside an object - the key is for it to be accessed at the right time. The section "After" above does it by wrapping it in another lambda and calling it immediately with the current value of i. Another way (a little bit easier to read - it produces no 'WAT' effect) is to store the value of i inside a partial object, and have the "inner" (original) lambda take it as an argument (passed supplied by the partial object at the time of the call), i.e.:

After 2:

>>> from functools import partial
>>> a = [partial(lambda y, x: y * x, i) for i in (1, 2)]
>>> a[0](2), a[1](2)
(2, 4)

Great, but there is still a little twist for you! Let's say we wan't to make it easier on the code reader, and pass the factor by name (as a keyword argument to partial). Let's do some renaming:

After 2.5:

>>> a = [partial(lambda coef, x: coef * x, coef=i) for i in (1, 2)]
>>> a[0](1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: <lambda>() got multiple values for argument 'coef'


>>> a[0]()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: <lambda>() missing 1 required positional argument: 'x'

Wait... We're changing the number of arguments by 1, and going from "too many" to "too few"?

Well, it's not a real WAT, when we pass coef to partial in this way, it becomes a keyword argument, so it must come after the positional x argument, like so:

After 3:

>>> a = [partial(lambda x, coef: coef * x, coef=i) for i in (1, 2)]
>>> a[0](2), a[1](2)
(2, 4)

I would prefer the last version over the nested lambda, but to each their own...

Edit 2020-08-18:

Thanks to commenter dasWesen, I found out that this stuff is covered in the Python documentation: - it deals with loops instead of list comprehensions, but the idea is the same - global or nonlocal variable access in the lambda function. There's even a solution - using default argument values (like for any function):

>>> a = [lambda x, coef=i: coef * x for i in (1, 2)]
>>> a[0](2), a[1](2)
(2, 4)

This way the coef value is bound to the value of i at the time of function definition (see James Powell's talk "Top To Down, Left To Right", which also explains why mutable default values are shunned).

Remove border from buttons

Try using: border:0; or border:none;

Specifying width and height as percentages without skewing photo proportions in HTML

Note: it is invalid to provide percentages directly as <img> width or height attribute unless you're using HTML 4.01 (see current spec, obsolete spec and this answer for more details). That being said, browsers will often tolerate such behaviour to support backwards-compatibility.

Those percentage widths in your 2nd example are actually applying to the container your <img> is in, and not the image's actual size. Say you have the following markup:

<div style="width: 1000px; height: 600px;">
    <img src="#" width="50%" height="50%">

Your resulting image will be 500px wide and 300px tall.

jQuery Resize

If you're trying to reduce an image to 50% of its width, you can do it with a snippet of jQuery:

$( "img" ).each( function() {
    var $img = $( this );
    $img.width( $img.width() * .5 );

Just make sure you take off any height/width = 50% attributes first.

Check if argparse optional argument is set or not

I think that optional arguments (specified with --) are initialized to None if they are not supplied. So you can test with is not None. Try the example below:

import argparse as ap

def main():
    parser = ap.ArgumentParser(description="My Script")
    args, leftovers = parser.parse_known_args()

    if args.myArg is not None:
        print "myArg has been set (value is %s)" % args.myArg

phpmyadmin #1045 Cannot log in to the MySQL server. after installing mysql command line client

After like three (3) hours of is the solution to the problem: First, I run this command;

$mysqladmin -u root -p[your root password here] version Which outputs:

    Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

    Oracle is a registered trademark of Oracle Corporation and/or its
    affiliates. Other names may be trademarks of their respective

    Server version      5.5.49-0ubuntu0.14.04.1
    Protocol version    10
    Connection      Localhost via UNIX socket
    UNIX socket     /var/run/mysqld/mysqld.sock
    Uptime:         1 hour 54 min 3 sec

Finally, I changed the connect_type parameter from tcp to socket and added the parameter socket in

    $cfg['Servers'][$i]['host'] = 'localhost';
    $cfg['Servers'][$i]['connect_type'] = 'socket';
    $cfg['Servers'][$i]['socket'] = '/var/run/mysqld/mysqld.sock';

All credit goes to this person: This is the correct solution

REST, HTTP DELETE and parameters

In addition to Alex's answer:

Note that http://server/resource/id?force_delete=true identifies a different resource than http://server/resource/id. For example, it is a huge difference whether you delete /customers/?status=old or /customers/.

Read input from console in Ruby?

if you want to hold the arguments from Terminal, try the following code:

A = ARGV[0].to_i
B = ARGV[1].to_i

puts "#{A} + #{B} = #{A + B}"

$(this).val() not working to get text from span using jquery

.val() is for input elements, use .html() instead

How to get text of an input text box during onKeyPress?

None of the answers so far offer a complete solution. There are quite a few issues to address:

  1. Not all keypresses are passed onto keydown and keypress handlers (e.g. backspace and delete keys are suppressed by some browsers).
  2. Handling keydown is not a good idea. There are situations where a keydown does NOT result in a keypress!
  3. setTimeout() style solutions get delayed under Google Chrome/Blink web browsers until the user stops typing.
  4. Mouse and touch events may be used to perform actions such as cut, copy, and paste. Those events will not trigger keyboard events.
  5. The browser, depending on the input method, may not deliver notification that the element has changed until the user navigates away from the field.

A more correct solution will handle the keypress, keyup, input, and change events.


<p><input id="editvalue" type="text"></p>
<p>The text box contains: <span id="labelvalue"></span></p>

function UpdateDisplay()
    var inputelem = document.getElementById("editvalue");
    var s = inputelem.value;

    var labelelem = document.getElementById("labelvalue");
    labelelem.innerText = s;

// Initial update.

// Register event handlers.
var inputelem = document.getElementById("editvalue");
inputelem.addEventListener('keypress', UpdateDisplay);
inputelem.addEventListener('keyup', UpdateDisplay);
inputelem.addEventListener('input', UpdateDisplay);
inputelem.addEventListener('change', UpdateDisplay);


Handling all four events catches all of the edge cases. When working with input from a user, all types of input methods should be considered and cross-browser and cross-device functionality should be verified. The above code has been tested in Firefox, Edge, and Chrome on desktop as well as the mobile devices I own.

What is the cleanest way to ssh and run multiple commands in Bash?

I see two ways:

First you make a control socket like this:

 ssh -oControlMaster=yes -oControlPath=~/.ssh/ssh-%r-%h-%p <yourip>

and run your commands

 ssh -oControlMaster=no -oControlPath=~/.ssh/ssh-%r-%h-%p <yourip> -t <yourcommand>

This way you can write an ssh command without actually reconnecting to the server.

The second would be to dynamically generate the script, scping it and running.

How to do logging in React Native?

Use console.log, console.warn etc.

As of React Native 0.29 you can simply run the following to see logs in the console:

$ react-native log-ios
$ react-native log-android

Can I delete a git commit but keep the changes?

2020 Simple way :

git reset <commit_hash>

(The commit hash of the last commit you want to keep).

If the commit was pushed, you can then do :

git push -f

You will keep the now uncommitted changes locally

What are .iml files in Android Studio?

What are iml files in Android Studio project?

A Google search on iml file turns up:

IML is a module file created by IntelliJ IDEA, an IDE used to develop Java applications. It stores information about a development module, which may be a Java, Plugin, Android, or Maven component; saves the module paths, dependencies, and other settings.

(from this page)

why not to use gradle scripts to integrate with external modules that you add to your project.

You do "use gradle scripts to integrate with external modules", or your own modules.

However, Gradle is not IntelliJ IDEA's native project model — that is separate, held in .iml files and the metadata in .idea/ directories. In Android Studio, that stuff is largely generated out of the Gradle build scripts, which is why you are sometimes prompted to "sync project with Gradle files" when you change files like build.gradle. This is also why you don't bother putting .iml files or .idea/ in version control, as their contents will be regenerated.

If I have a team that work in different IDE's like Eclipse and AS how to make project IDE agnostic?

To a large extent, you can't.

You are welcome to have an Android project that uses the Eclipse-style directory structure (e.g., resources and manifest in the project root directory). You can teach Gradle, via build.gradle, how to find files in that structure. However, other metadata (compileSdkVersion, dependencies, etc.) will not be nearly as easily replicated.

Other alternatives include:

  • Move everybody over to another build system, like Maven, that is equally integrated (or not, depending upon your perspective) to both Eclipse and Android Studio

  • Hope that Andmore takes off soon, so that perhaps you can have an Eclipse IDE that can build Android projects from Gradle build scripts

  • Have everyone use one IDE

JavaScript chop/slice/trim off last character in string

Using JavaScript's slice function:

let string = 'foo_bar';_x000D_
string = string.slice(0, -4); // Slice off last four characters here_x000D_

This could be used to remove '_bar' at end of a string, of any length.

How to define object in array in Mongoose schema correctly with 2d geo index

I had a similar issue with mongoose :

    [ '[object Object]',
     '[object Object]',
     '[object Object]',
     '[object Object]' ] }

In fact, I was using "type" as a property name in my schema :

fields: [
      name: String,
      type: {
        type: String
      registrationEnabled: Boolean,
      checkinEnabled: Boolean

To avoid that behavior, you have to change the parameter to :

fields: [
      name: String,
      type: {
        type: { type: String }
      registrationEnabled: Boolean,
      checkinEnabled: Boolean

What is the most robust way to force a UIView to redraw?

The money-back guaranteed, reinforced-concrete-solid way to force a view to draw synchronously (before returning to the calling code) is to configure the CALayer's interactions with your UIView subclass.

In your UIView subclass, create a displayNow() method that tells the layer to “set course for display” then to “make it so”:


/// Redraws the view's contents immediately.
/// Serves the same purpose as the display method in GLKView.
public func displayNow()
    let layer = self.layer


/// Redraws the view's contents immediately.
/// Serves the same purpose as the display method in GLKView.
- (void)displayNow
    CALayer *layer = self.layer;
    [layer setNeedsDisplay];
    [layer displayIfNeeded];

Also implement a draw(_: CALayer, in: CGContext) method that'll call your private/internal drawing method (which works since every UIView is a CALayerDelegate):


/// Called by our CALayer when it wants us to draw
///     (in compliance with the CALayerDelegate protocol).
override func draw(_ layer: CALayer, in context: CGContext)


/// Called by our CALayer when it wants us to draw
///     (in compliance with the CALayerDelegate protocol).
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)context
    [self internalDrawWithRect:self.bounds];

And create your custom internalDraw(_: CGRect) method, along with fail-safe draw(_: CGRect):


/// Internal drawing method; naming's up to you.
func internalDraw(_ rect: CGRect)
    // @FILLIN: Custom drawing code goes here.
    //  (Use `UIGraphicsGetCurrentContext()` where necessary.)

/// For compatibility, if something besides our display method asks for draw.
override func draw(_ rect: CGRect) {


/// Internal drawing method; naming's up to you.
- (void)internalDrawWithRect:(CGRect)rect
    // @FILLIN: Custom drawing code goes here.
    //  (Use `UIGraphicsGetCurrentContext()` where necessary.)

/// For compatibility, if something besides our display method asks for draw.
- (void)drawRect:(CGRect)rect {
    [self internalDrawWithRect:rect];

And now just call myView.displayNow() whenever you really-really need it to draw (such as from a CADisplayLink callback).  Our displayNow() method will tell the CALayer to displayIfNeeded(), which will synchronously call back into our draw(_:,in:) and do the drawing in internalDraw(_:), updating the visual with what's drawn into the context before moving on.

This approach is similar to @RobNapier's above, but has the advantage of calling displayIfNeeded() in addition to setNeedsDisplay(), which makes it synchronous.

This is possible because CALayers expose more drawing functionality than UIViews do— layers are lower-level than views and designed explicitly for the purpose of highly-configurable drawing within the layout, and (like many things in Cocoa) are designed to be used flexibly (as a parent class, or as a delegator, or as a bridge to other drawing systems, or just on their own). Proper usage of the CALayerDelegate protocol makes all this possible.

More information about the configurability of CALayers can be found in the Setting Up Layer Objects section of the Core Animation Programming Guide.

How to perform case-insensitive sorting in JavaScript?

arr.sort(function(a,b) {
    a = a.toLowerCase();
    b = b.toLowerCase();
    if( a == b) return 0;
    if( a > b) return 1;
    return -1;

In above function, if we just compare when lower case two value a and b, we will not have the pretty result.

Example, if array is [A, a, B, b, c, C, D, d, e, E] and we use the above function, we have exactly that array. It's not changed anything.

To have the result is [A, a, B, b, C, c, D, d, E, e], we should compare again when two lower case value is equal:

function caseInsensitiveComparator(valueA, valueB) {
    var valueALowerCase = valueA.toLowerCase();
    var valueBLowerCase = valueB.toLowerCase();

    if (valueALowerCase < valueBLowerCase) {
        return -1;
    } else if (valueALowerCase > valueBLowerCase) {
        return 1;
    } else { //valueALowerCase === valueBLowerCase
        if (valueA < valueB) {
            return -1;
        } else if (valueA > valueB) {
            return 1;
        } else {
            return 0;

Pros/cons of using redux-saga with ES6 generators vs redux-thunk with ES2017 async/await

I'd just like to add some comments from my personal experience (using both sagas and thunk):

Sagas are great to test:

  • You don't need to mock functions wrapped with effects
  • Therefore tests are clean, readable and easy to write
  • When using sagas, action creators mostly return plain object literals. It is also easier to test and assert unlike thunk's promises.

Sagas are more powerful. All what you can do in one thunk's action creator you can also do in one saga, but not vice versa (or at least not easily). For example:

  • wait for an action/actions to be dispatched (take)
  • cancel existing routine (cancel, takeLatest, race)
  • multiple routines can listen to the same action (take, takeEvery, ...)

Sagas also offers other useful functionality, which generalize some common application patterns:

  • channels to listen on external event sources (e.g. websockets)
  • fork model (fork, spawn)
  • throttle
  • ...

Sagas are great and powerful tool. However with the power comes responsibility. When your application grows you can get easily lost by figuring out who is waiting for the action to be dispatched, or what everything happens when some action is being dispatched. On the other hand thunk is simpler and easier to reason about. Choosing one or another depends on many aspects like type and size of the project, what types of side effect your project must handle or dev team preference. In any case just keep your application simple and predictable.

@Directive vs @Component in Angular

If you refer the official angular docs

There are three kinds of directives in Angular:

  1. Components—directives with a template.
  2. Structural directives—change the DOM layout by adding and removing DOM elements. e.g *ngIf
  3. Attribute directives—change the appearance or behavior of an element, component, or another directive. e.g [ngClass].

As the Application grows we find difficulty in maintaining all these codes. For reusability purpose, we separate our logic in smart components and dumb components and we use directives (structural or attribute) to make changes in the DOM.

Convert PEM to PPK file format

PuTTYgen for Ubuntu/Linux and PEM to PPK

sudo apt install putty-tools
puttygen -t rsa -b 2048 -C "user@host" -o keyfile.ppk

Maven build failed: "Unable to locate the Javac Compiler in: jre or jdk issue"

Go to the Properties dialog and right click on the project.

In Linked resources, add a new path called JAVA_HOME and put in your JDK location, something like "C:\Program Files\Java\jdk1.8.0_73".

That's all!!

Best practices when running Node.js with port 80 (Ubuntu / Linode)

Give Safe User Permission To Use Port 80

Remember, we do NOT want to run your applications as the root user, but there is a hitch: your safe user does not have permission to use the default HTTP port (80). You goal is to be able to publish a website that visitors can use by navigating to an easy to use URL like http://ip:port/

Unfortunately, unless you sign on as root, you’ll normally have to use a URL like http://ip:port - where port number > 1024.

A lot of people get stuck here, but the solution is easy. There a few options but this is the one I like. Type the following commands:

sudo apt-get install libcap2-bin
sudo setcap cap_net_bind_service=+ep `readlink -f \`which node\``

Now, when you tell a Node application that you want it to run on port 80, it will not complain.

Check this reference link

Why is volatile needed in C?

I'll mention another scenario where volatiles are important.

Suppose you memory-map a file for faster I/O and that file can change behind the scenes (e.g. the file is not on your local hard drive, but is instead served over the network by another computer).

If you access the memory-mapped file's data through pointers to non-volatile objects (at the source code level), then the code generated by the compiler can fetch the same data multiple times without you being aware of it.

If that data happens to change, your program may become using two or more different versions of the data and get into an inconsistent state. This can lead not only to logically incorrect behavior of the program but also to exploitable security holes in it if it processes untrusted files or files from untrusted locations.

If you care about security, and you should, this is an important scenario to consider.

How to increment a datetime by one day?

date = datetime.datetime(2003,8,1,12,4,5)
for i in range(5): 
    date += datetime.timedelta(days=1)

How can I convert string to datetime with format specification in JavaScript?

Just to give my 5 cents.

My date format is (UK format) and none of the above examples were working for me. All the parsers were considering mm as day and dd as month.

I've found this library: and it worked, because you can say the order of the fields like this:

>>console.log(new Date(Date.fromString('09.05.2012', {order: 'DMY'})));
Wed May 09 2012 00:00:00 GMT+0300 (EEST)

I hope that helps someone.

Install php-mcrypt on CentOS 6

There are two ways you can address this:

How can I set the aspect ratio in matplotlib?

A simple option using plt.gca() to get current axes and set aspect


in place of your last line

C# ListView Column Width Auto

You gave the answer: -2 will autosize the column to the length of the text in the column header, -1 will autosize to the longest item in the column. All according to MSDN. Note though that in the case of -1, you will need to set the column width after adding the item(s). So if you add a new item, you will also need to assign the width property of the column (or columns) that you want to autosize according to data in ListView control.

Simple 3x3 matrix inverse code (C++)

A rather nice (I think) header file containing macros for most 2x2, 3x3 and 4x4 matrix operations has been available with most OpenGL toolkits. Not as standard but I've seen it at various places.

You can check it out here. At the end of it you will find both inverse of 2x2, 3x3 and 4x4.


WampServer: php-win.exe The program can't start because MSVCR110.dll is missing

What solves my problem: I am using 64 bit Windows 7, so I thought I could install 64 bit Wamp. After I Installed the 32-bit version the error does not appear. So something in the developing process at Wamp went wrong...

Dynamically add item to jQuery Select2 control that uses AJAX

This provided a simple solution: Set data in Select2 after insert with AJAX

$("#select2").select2('data', {id: newID, text: newText});      

how to insert value into DataGridView Cell?

You can access any DGV cell as follows :

dataGridView1.Rows[rowIndex].Cells[columnIndex].Value = value;

But usually it's better to use databinding : you bind the DGV to a data source (DataTable, collection...) through the DataSource property, and only work on the data source itself. The DataGridView will automatically reflect the changes, and changes made on the DataGridView will be reflected on the data source

Javascript swap array elements

This seems ok....

var b = list[y];
list[y] = list[x];
list[x] = b;

Howerver using

var b = list[y];

means a b variable is going to be to be present for the rest of the scope. This can potentially lead to a memory leak. Unlikely, but still better to avoid.

Maybe a good idea to put this into Array.prototype.swap

Array.prototype.swap = function (x,y) {
  var b = this[x];
  this[x] = this[y];
  this[y] = b;
  return this;

which can be called like:

list.swap( x, y )

This is a clean approach to both avoiding memory leaks and DRY.

Numpy matrix to array

First, Mv = numpy.asarray(M.T), which gives you a 4x1 but 2D array.

Then, perform A = Mv[0,:], which gives you what you want. You could put them together, as numpy.asarray(M.T)[0,:].

PHP code to remove everything but numbers

a much more practical way for those who do not want to use regex:

$data = filter_var($data, FILTER_SANITIZE_NUMBER_INT);

note: it works with phone numbers too.

IIS Request Timeout on long ASP.NET operation

Great and exhaustive answerby @Kev!

Since I did long processing only in one admin page in a WebForms application I used the code option. But to allow a temporary quick fix on production I used the config version in a <location> tag in web.config. This way my admin/processing page got enough time, while pages for end users and such kept their old time out behaviour.

Below I gave the config for you Googlers needing the same quick fix. You should ofcourse use other values than my '4 hour' example, but DO note that the session timeOut is in minutes, while the request executionTimeout is in seconds!

And - since it's 2015 already - for a NON- quickfix you should use .Net 4.5's async/await now if at all possible, instead of the .NET 2.0's ASYNC page that was state of the art when KEV answered in 2010 :).

    <compilation debug="false" ...>
    ... other stuff ..

    <location path="~/Admin/SomePage.aspx">
            <sessionState timeout="240" />
            <httpRuntime executionTimeout="14400" />

How to align an indented line in a span that wraps into multiple lines?


then you've got a block element and the margin is added to all lines.

While it's true that a span is semantically not a block element, there are cases where you don't have control of the pages DOM. This answer is inteded for those.

How to convert a "dd/mm/yyyy" string to datetime in SQL Server?

You can convert a string to a date easily by:


Unable to load config info from /usr/local/ssl/openssl.cnf on Windows

In Windows 7 I didn't have to restart, simply run command prompt in administrator mode.

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

define a String variable using the JSP tags

String test = new String();

then refer to that variable in your loop as

<c:forEach items="${myParams.items}" var="currentItem" varStatus="stat">
test+= whaterver_value

How do I execute a string containing Python code in Python?

The most logical solution would be to use the built-in eval() function .Another solution is to write that string to a temporary python file and execute it.

MATLAB, Filling in the area between two sets of data, lines in one figure

Personally, I find it both elegant and convenient to wrap the fill function. To fill between two equally sized row vectors Y1 and Y2 that share the support X (and color C):

fill_between_lines = @(X,Y1,Y2,C) fill( [X fliplr(X)],  [Y1 fliplr(Y2)], C );

How to validate Google reCAPTCHA v3 on server side?

I'm not a fan of any of these solutions. I use this instead:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "");
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
    'secret' => $privatekey,
    'response' => $_POST['g-recaptcha-response'],
    'remoteip' => $_SERVER['REMOTE_ADDR']

$resp = json_decode(curl_exec($ch));

if ($resp->success) {
    // Success
} else {
    // failure

I'd argue that this is superior because you ensure it is being POSTed to the server and it's not making an awkward 'file_get_contents' call. This is compatible with recaptcha 2.0 described here:

I find this cleaner. I see most solutions are file_get_contents, when I feel curl would suffice.

How to set the margin or padding as percentage of height of parent container?

To make the child element positioned absolutely from its parent element you need to set relative position on the parent element AND absolute position on the child element.

Then on the child element 'top' is relative to the height of the parent. So you also need to 'translate' upward the child 50% of its own height.

    background-color: green;_x000D_
    width: 200px;_x000D_
    height: 200px;_x000D_
    overflow: auto;_x000D_
    position: relative;_x000D_
.vert-align {_x000D_
    position: absolute;_x000D_
    top: 50%;_x000D_
    transform: translate(0, -50%);_x000D_
    <div class="base">_x000D_
        <div class="vert-align">_x000D_
            Content Here_x000D_

There is another a solution using flex box.

    width: 200px;_x000D_
    height: 200px;_x000D_
    overflow: auto;_x000D_
    display: flex;_x000D_
    align-items: center;_x000D_
<div class="base">_x000D_
    <div class="vert-align">_x000D_
        Content Here_x000D_

You will find advantages/disavantages for both.

Free easy way to draw graphs and charts in C++?

My favourite has always been gnuplot. It's very extensive, so it might be a bit too complex for your needs though. It is cross-platform and there is a C++ API.

How to format strings using printf() to get equal length in the output

You can specify a width on string fields, e.g.

printf("%-20s", "initialization...");

And then whatever's printed with that field will be blank-padded to the width you indicate.

The - left-justifies your text in that field.

Set value of textarea in jQuery

I think there is missing one important aspect:


works only when there is an ID selector (#)

for class selector there is an option to use native value like:

$('.some-text-area')[0].value = 'test';

Jquery Setting Value of Input Field


Using scanner.nextLine()

It's because when you enter a number then press Enter, input.nextInt() consumes only the number, not the "end of line". Primitive data types like int, double etc do not consume "end of line", therefore the "end of line" remains in buffer and When executes, it consumes the "end of line" from buffer from the first input. That's why, your String sentence = only consumes the "end of line" and does not wait to read from keyboard.

Tip: use scanner.nextLine() instead of because does not read white spaces from the keyboard. (Truncate the string after giving some space from keyboard, only show string before space.)

Html.EditorFor Set Default Value

The clean way to do so is to pass a new instance of the created entity through the controller:

public ActionResult CreateNewMyEntity(string default_value)
    MyEntity newMyEntity = new MyEntity();
    newMyEntity._propertyValue = default_value;

    return View(newMyEntity);

If you want to pass the default value through ActionLink

@Html.ActionLink("Create New", "CreateNewMyEntity", new { default_value = "5" })

Div Background Image Z-Index Issue

To solve the issue, you are using the z-index on the footer and header, but you forgot about the position, if a z-index is to be used, the element must have a position:

Add to your footer and header this CSS:

position: relative; 


Also noticed that the background image on the #backstretch has a negative z-index, don't use that, some browsers get really weird...

Remove From the #backstretch:

z-index: -999999;

Read a little bit about Z-Index here!

Uncaught ReferenceError: <function> is not defined at HTMLButtonElement.onclick

Place your script inside the body tag

  // Rest of html
  function hideButton() {
function showButton() {
< /body>

If you check this JSFIDDLE and click on javascript, you will see the load Type body is selected

How do I print my Java object without getting "SomeType@2f92e0f4"?


All Java objects have a toString() method, which is invoked when you try to print the object.

System.out.println(myObject);  // invokes myObject.toString()

This method is defined in the Object class (the superclass of all Java objects). The Object.toString() method returns a fairly ugly looking string, composed of the name of the class, an @ symbol and the hashcode of the object in hexadecimal. The code for this looks like:

// Code of Object.toString()
public String toString() {
    return getClass().getName() + "@" + Integer.toHexString(hashCode());

A result such as can therefore be explained as:

  • - the name of the class, i.e. the class is MyType in the package
  • @ - joins the string together
  • 2f92e0f4 the hashcode of the object.

The name of array classes look a little different, which is explained well in the Javadocs for Class.getName(). For instance, [Ljava.lang.String means:

  • [ - an single-dimensional array (as opposed to [[ or [[[ etc.)
  • L - the array contains a class or interface
  • java.lang.String - the type of objects in the array

Customizing the Output

To print something different when you call System.out.println(myObject), you must override the toString() method in your own class. Here's a simple example:

public class Person {

  private String name;
  // constructors and other methods omitted
  public String toString() {
    return name;

Now if we print a Person, we see their name rather than

Bear in mind that toString() is just one way for an object to be converted to a string. Typically this output should fully describe your object in a clear and concise manner. A better toString() for our Person class might be:

public String toString() {
  return getClass().getSimpleName() + "[name=" + name + "]";

Which would print, e.g., Person[name=Henry]. That's a really useful piece of data for debugging/testing.

If you want to focus on just one aspect of your object or include a lot of jazzy formatting, you might be better to define a separate method instead, e.g. String toElegantReport() {...}.

Auto-generating the Output

Many IDEs offer support for auto-generating a toString() method, based on the fields in the class. See docs for Eclipse and IntelliJ, for example.

Several popular Java libraries offer this feature as well. Some examples include:

Printing groups of objects

So you've created a nice toString() for your class. What happens if that class is placed into an array or a collection?


If you have an array of objects, you can call Arrays.toString() to produce a simple representation of the contents of the array. For instance, consider this array of Person objects:

Person[] people = { new Person("Fred"), new Person("Mike") };

// Prints: [Fred, Mike]

Note: this is a call to a static method called toString() in the Arrays class, which is different to what we've been discussing above.

If you have a multi-dimensional array, you can use Arrays.deepToString() to achieve the same sort of output.


Most collections will produce a pretty output based on calling .toString() on every element.

List<Person> people = new ArrayList<>();
people.add(new Person("Alice"));
people.add(new Person("Bob"));    

// Prints [Alice, Bob]

So you just need to ensure your list elements define a nice toString() as discussed above.


While all of the answers here are a really good explanation of what cors is but the direct answer to your question would be because of the following differences postman and browser.

Browser: Sends OPTIONS call to check the server type and getting the headers before sending any new request to the API endpoint. Where it checks for Access-Control-Allow-Origin. Taking this into account Access-Control-Allow-Origin header just specifies which all CROSS ORIGINS are allowed, although by default browser will only allow the same origin.

Postman: Sends direct GET, POST, PUT, DELETE etc. request without checking what type of server is and getting the header Access-Control-Allow-Origin by using OPTIONS call to the server.

How to check if a file is a valid image file?

format = [".jpg",".png",".jpeg"]
 for (path,dirs,files) in os.walk(path):
     for file in files:
         if file.endswith(tuple(format)):
             print ("Valid",file)

Centering the pagination in bootstrap

In v4.0.0-alpha.6:

<div class="text-center text-sm-right">
    <ul class="pagination d-inline-flex">...</ul>

Display all post meta keys and meta values of the same post ID in wordpress

$myvals = get_post_meta( get_the_ID());
foreach($myvals as $key=>$val){
  foreach($val as $vals){
    if ($key=='Youtube'){
       echo $vals 

Key = Youtube videos all meta keys for youtube videos and value

"Debug certificate expired" error in Eclipse Android plugins

On Ubuntu, this worked:

I went to home/username/.android and I renamed keystore.debug to keystoreold.debug. I then closed Eclipse, started Eclipse, and SDK created new certificate keystore.debug in that folder.

You then have to uninstall/reinstall apps you installed via USB Debugging or an unsigned APK ("unsigned" APK = signed with debug certificate).

how to download file in react js

You can use FileSaver.js to achieve this goal:

const saveFile = () => {
  process.env.REACT_APP_CLIENT_URL + "/resources/cv.pdf",


<button className="cv" onClick={saveFile}>
    Download File

Change class on mouseover in directive

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

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

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

with some styling:

.red {
  background-color: red;

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

See running example here: jsfiddle sample

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

How do I change Bootstrap 3 column order on mobile layout?

October 2017

I would like to add another Bootstrap 4 solution. One that worked for me.

The CSS "Order" property, combined with a media query, can be used to re-order columns when they get stacked in smaller screens.

Something like this:

@media only screen and (max-width: 768px) {
    #first {
        order: 2;
    #second {
        order: 4;
    #third {
        order: 1;
    #fourth {
        order: 3;

CodePen Link:

Adjust the screen size and you'll see the columns get stacked in a different order.

I'll tie this in with the original poster's question. With CSS, the navbar, sidebar, and content can be targeted and then order properties applied within a media query.

How to create a Java / Maven project that works in Visual Studio Code?

An alternative way is to install the Maven for Java plugin and create a maven project within Visual Studio. The steps are described in the official documentation:

  1. From the Command Palette (Crtl+Shift+P), select Maven: Generate from Maven Archetype and follow the instructions, or
  2. Right-click on a folder and select Generate from Maven Archetype.

How to restore the permissions of files and directories within git if they have been modified?

The easiest thing to do is to just change the permissions back. As @kroger noted git only tracks executable bits. So you probably just need to run chmod -x filename to fix it (or +x if that's what's needed.

MySQL > Table doesn't exist. But it does (or it should)

After having to reinstall MySQL I had this same problem, it seems that during the install, some configuration files that store data about the InnoDB log files, these files ib_logfile* (they are log files right?), are overwriten. To solve this problem I just deleted the ib_logfile* files.

jQuery if Element has an ID?

You can use jQuery's .is() function.

if ( $(".parent a").is("#idSelector") ) {

//Do stuff


It will return true if the parent anchor has #idSelector id.

How does a Linux/Unix Bash script know its own PID?

The variable '$$' contains the PID.

How can we convert an integer to string in AngularJs

.toString() is available, or just add "" to the end of the int

var x = 3,
    toString = x.toString(),
    toConcat = x + "";

Angular is simply JavaScript at the core.

What is the difference between Linear search and Binary search?

Linear Search looks through items until it finds the searched value.

Efficiency: O(n)

Example Python Code:

test_list = [1, 3, 9, 11, 15, 19, 29]
test_val1 = 25
test_val2 = 15

def linear_search(input_array, search_value):
    index = 0
    while (index < len(input_array)) and (input_array[index] < search_value):
        index += 1
    if index >= len(input_array) or input_array[index] != search_value:
        return -1

    return index

print linear_search(test_list, test_val1)
print linear_search(test_list, test_val2)

Binary Search finds the middle element of the array. Checks that middle value is greater or lower than the search value. If it is smaller, it gets the left side of the array and finds the middle element of that part. If it is greater, gets the right part of the array. It loops the operation until it finds the searched value. Or if there is no value in the array finishes the search.

Efficiency: O(logn)

Example Python Code:

test_list = [1, 3, 9, 11, 15, 19, 29]
test_val1 = 25
test_val2 = 15

def binary_search(input_array, value):
    low = 0
    high = len(input_array) - 1
    while low <= high:
        mid = (low + high) / 2
        if input_array[mid] == value:
            return mid
        elif input_array[mid] < value:
            low = mid + 1
            high = mid - 1

    return -1

print binary_search(test_list, test_val1)
print binary_search(test_list, test_val2)

Also you can see visualized information about Linear and Binary Search here:

Could not load dynamic library 'cudart64_101.dll' on tensorflow CPU-only installation

A simpler way would be to create a link called cudart64_101.dll to point to cudart64_102.dll. This is not very orthodox but since TensorFlow is looking for cudart64_101.dll exported symbols and the nvidia folks are not amateurs, they would most likely not remove symbols from 101 to 102. It works, based on this assumption (mileage may vary).

Injecting @Autowired private field during testing

You can absolutely inject mocks on MyLauncher in your test. I am sure if you show what mocking framework you are using someone would be quick to provide an answer. With mockito I would look into using @RunWith(MockitoJUnitRunner.class) and using annotations for myLauncher. It would look something like what is below.

public class MyLauncherTest
    private MyLauncher myLauncher = new MyLauncher();

    private MyService myService;

    public void someTest() {


How do I change the figure size for a seaborn plot?

You can set the context to be poster or manually set fig_size.

import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt

n, p = 40, 8
d = np.random.normal(0, 2, (n, p))
d += np.log(np.arange(1, p + 1)) * -5 + 10

# plot
fig, ax = plt.subplots()
# the size of A4 paper
fig.set_size_inches(11.7, 8.27)
sns.violinplot(data=d, inner="points", ax=ax)    


enter image description here

Reading values from DataTable

You can do it using the foreach loop

DataTable dr_art_line_2 = ds.Tables["QuantityInIssueUnit"];

  foreach(DataRow row in dr_art_line_2.Rows)
     QuantityInIssueUnit_value = Convert.ToInt32(row["columnname"]);

Appending to an object

Now with ES6 we have a very powerful spread operator (...Object) which can make this job very easy. It can be done as follows:

let alerts = { 
   1: { app: 'helloworld', message: 'message' },
   2: { app: 'helloagain', message: 'another message' }

//now suppose you want to add another key called alertNo. with value 2 in the alerts object. 

alerts = {
   alertNo: 2

Thats it. It will add the key you want. Hope this helps!!

jquery: animate scrollLeft

First off I should point out that css animations would probably work best if you are doing this a lot but I ended getting the desired effect by wrapping .scrollLeft inside .animate


    $('.swipeBox').animate( { scrollLeft: '+=460' }, 1000);

    $('.swipeBox').animate( { scrollLeft: '-=460' }, 1000);

The second parameter is speed, and you can also add a third parameter if you are using smooth scrolling of some sort.

What are the differences between "git commit" and "git push"?

A very crude analogy: if we compare git commit to saving an edited file, then git push would be copying that file to another location.

Please don't take this analogy out of this context -- committing and pushing are not quite like saving an edited file and copying it. That said, it should hold for comparisons sake.

How to create an empty file at the command line in Windows?

For creating any type of file you can use the following code

type nul > (file_name).(file_type)

Eg. If you want to create a text file then

type nul > demo.txt

If you want to create a javascript file then

type nul > demo.js

Using SVG as background image

Set Background svg with content/cart at center

.login-container {
  justify-content: center;
  align-items: center;
  display: flex;
  height: 100vh; 
  background-image: url(/assets/images/login-bg.svg);
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;

Java JSON serialization - best practice

Are you tied to this library? Google Gson is very popular. I have myself not used it with Generics but their front page says Gson considers support for Generics very important.

Java optional parameters

VarArgs and overloading have been mentioned. Another option is a Bloch Builder pattern, which would look something like this:

 MyObject my = new MyObjectBuilder().setParam1(value)

Although that pattern would be most appropriate for when you need optional parameters in a constructor.

Putting an if-elif-else statement on one line?

No, it's not possible (at least not with arbitrary statements), nor is it desirable. Fitting everything on one line would most likely violate PEP-8 where it is mandated that lines should not exceed 80 characters in length.

It's also against the Zen of Python: "Readability counts". (Type import this at the Python prompt to read the whole thing).

You can use a ternary expression in Python, but only for expressions, not for statements:

>>> a = "Hello" if foo() else "Goodbye"


Your revised question now shows that the three statements are identical except for the value being assigned. In that case, a chained ternary operator does work, but I still think that it's less readable:

>>> i=100
>>> a = 1 if i<100 else 2 if i>100 else 0
>>> a
>>> i=101
>>> a = 1 if i<100 else 2 if i>100 else 0
>>> a
>>> i=99
>>> a = 1 if i<100 else 2 if i>100 else 0
>>> a

how to convert `content://media/external/images/media/Y` to `file:///storage/sdcard0/Pictures/X.jpg` in android?

Will something like this work for you? What this does is query the content resolver to find the file path data that is stored for that content entry

public static String getRealPathFromUri(Context context, Uri contentUri) {
    Cursor cursor = null;
    try {
        String[] proj = { MediaStore.Images.Media.DATA };
        cursor = context.getContentResolver().query(contentUri, proj, null, null, null);
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        return cursor.getString(column_index);
    } finally {
        if (cursor != null) {

This will end up giving you an absolute file path that you can construct a file uri from

Can't push to remote branch, cannot be resolved to branch

Had the same problem with different casing.

Did a checkout to development (or master) then changed the name (the wrong name) to something else like test.

  • git checkout development
  • git branch -m wrong-name test

then change the name back to the right name

  • git branch -m test right-name

then checkout to the right-name branch

  • git checkout right-name

then it worked to push to the remote branch

  • git push origin right-name

How to compare two JSON have the same properties without order?

This question reminds of how to determine equality for two JavaScript objects. So, I would choose this general function

Compares JS objects:

function objectEquals(x, y) {
    // if both are function
    if (x instanceof Function) {
        if (y instanceof Function) {
            return x.toString() === y.toString();
        return false;
    if (x === null || x === undefined || y === null || y === undefined) { return x === y; }
    if (x === y || x.valueOf() === y.valueOf()) { return true; }

    // if one of them is date, they must had equal valueOf
    if (x instanceof Date) { return false; }
    if (y instanceof Date) { return false; }

    // if they are not function or strictly equal, they both need to be Objects
    if (!(x instanceof Object)) { return false; }
    if (!(y instanceof Object)) { return false; }

    var p = Object.keys(x);
    return Object.keys(y).every(function (i) { return p.indexOf(i) !== -1; }) ?
            p.every(function (i) { return objectEquals(x[i], y[i]); }) : false;

Auto Increment after delete in MySQL

I came here looking for an answer to the Title question "MySQL - Auto Increment after delete" but I could only find an answer for that in the questions

By using something like:


Note that Darin Dimitrov's answer explain really well AUTO_INCREMENT and it's usage. Take a look there before doing something you might regret.

PS: The question itself is more "Why you need to recycle key values?" and Dolph's answer cover that.

How to use ng-repeat for dictionaries in AngularJs?

JavaScript developers tend to refer to the above data-structure as either an object or hash instead of a Dictionary.

Your syntax above is wrong as you are initializing the users object as null. I presume this is a typo, as the code should read:

// Initialize users as a new hash.
var users = {};
users["182982"] = "...";

To retrieve all the values from a hash, you need to iterate over it using a for loop:

function getValues (hash) {
    var values = [];
    for (var key in hash) {

        // Ensure that the `key` is actually a member of the hash and not
        // a member of the `prototype`.
        // see:
        if (hash.hasOwnProperty(key)) {
    return values;

If you plan on doing a lot of work with data-structures in JavaScript then the underscore.js library is definitely worth a look. Underscore comes with a values method which will perform the above task for you:

var values = _.values(users);

I don't use Angular myself, but I'm pretty sure there will be a convenience method build in for iterating over a hash's values (ah, there we go, Artem Andreev provides the answer above :))

How to change onClick handler dynamically?

Use .onclick (all lowercase). Like so:

document.getElementById("foo").onclick = function () {
  alert('foo'); // do your stuff
  return false; // <-- to suppress the default link behaviour

Actually, you'll probably find yourself way better off using some good library (I recommend jQuery for several reasons) to get you up and running, and writing clean javascript.

Cross-browser (in)compatibilities are a right hell to deal with for anyone - let alone someone who's just starting.

Parsing JSON Object in Java

Thank you so much to @Code in another answer. I can read any JSON file thanks to your code. Now, I'm trying to organize all the elements by levels, for could use them!

I was working with Android reading a JSON from an URL and the only I had to change was the lines

Set<Object> set = jsonObject.keySet(); Iterator<Object> iterator = set.iterator();


Iterator<?> iterator = jsonObject.keys();

I share my implementation, to help someone:

public void parseJson(JSONObject jsonObject) throws ParseException, JSONException {

    Iterator<?> iterator = jsonObject.keys();
    while (iterator.hasNext()) {
        String obj =;

        if (jsonObject.get(obj) instanceof JSONArray) {
            //Toast.makeText(MainActivity.this, "Objeto: JSONArray", Toast.LENGTH_SHORT).show();
            TextView txtView = new TextView(this);
        } else {
            if (jsonObject.get(obj) instanceof JSONObject) {
                //Toast.makeText(MainActivity.this, "Objeto: JSONObject", Toast.LENGTH_SHORT).show();
                parseJson((JSONObject) jsonObject.get(obj));
            } else {
                //Toast.makeText(MainActivity.this, "Objeto: Value", Toast.LENGTH_SHORT).show();
                //System.out.println(obj.toString() + "\t"+ jsonObject.get(obj));
                TextView txtView = new TextView(this);
                txtView.setText(obj.toString() + "\t"+ jsonObject.get(obj));

functional way to iterate over range (ES6/7)

One can create an empty array, fill it (otherwise map will skip it) and then map indexes to values:

Array(8).fill().map((_, i) => i * i);

what innerHTML is doing in javascript?

Each HTML element has an innerHTML property that defines both the HTML code and the text that occurs between that element's opening and closing tag. By changing an element's innerHTML after some user interaction, you can make much more interactive pages.

However, using innerHTML requires some preparation if you want to be able to use it easily and reliably. First, you must give the element you wish to change an id. With that id in place you will be able to use the getElementById function, which works on all browsers.

Live Video Streaming with PHP

There are a lot of "off-the-shelf" 'servers' that will run in your environment. Most of these utilize the aforementioned Flex or Silverlight to implement the actual video itself but I'm pretty sure all will run under LAMP/PHP.

The challenges will picking the best software from everything that's available and getting your hosting-provider to let you stream video (it goes without saying that streaming is heavy on bandwidth).

Pure JavaScript equivalent of jQuery's $.ready() - how to call a function when the page/DOM is ready for it

document.ondomcontentready=function(){} should do the trick, but it doesn't have full browser compatibility.

Seems like you should just use jQuery min

How can I take a screenshot with Selenium WebDriver?



The above method will take a screenshot and also store it as a file in the location provided as a parameter.

Passive Link in Angular 2 - <a href=""> equivalent

You have prevent the default browser behaviour. But you don’t need to create a directive to accomplish that.

It’s easy as the following example:


<a href="" (click)="goToPage(pageIndex, $event)">Link</a>


goToPage(pageIndex, event) {

Check whether a string contains a substring

To find out if a string contains substring you can use the index function:

if (index($str, $substr) != -1) {
    print "$str contains $substr\n";

It will return the position of the first occurrence of $substr in $str, or -1 if the substring is not found.

How to move a marker in Google Maps API

Just try to create the marker and set the draggable property to true. The code will be something as follows:

Marker = new google.maps.Marker({
    position: latlon,
    map: map,            
    draggable: true,
    title: "Drag me!"

I hope this helps!

How should I import data from CSV into a Postgres table using pgAdmin 3?

pgAdmin has GUI for data import since 1.16. You have to create your table first and then you can import data easily - just right-click on the table name and click on Import.

enter image description here

enter image description here

Why is PHP session_destroy() not working?

Perhaps is way too late to respond but, make sure your session is initialized before destroying it.

session_start() ;
session_destroy() ;

i.e. you cannot destroy a session in logout.php if you initialized your session in index.php. You must start the session in logout.php before destroying it.

Git cli: get user info from username

Use this to see the logged in user (the actual git account):

git config credential.username

And as other answers the user email and user name (this is differenct from user credentials):

git config
git config

To see the list of all configs:

git config --list

Choose newline character in Notepad++

For a new document: Settings -> Preferences -> New Document/Default Directory -> New Document -> Format -> Windows/Mac/Unix

And for an already-open document: Edit -> EOL Conversion

The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)

For those using Telerik as mentioned by Ovar, make sure you wrap your javascript in

 <telerik:RadScriptBlock ID="radSript1" runat="server">
   <script type="text/javascript">
        //Your javascript

Since Telerik doesn't recognize <%# %> when looking for an element and <%= %> will give you an error if your javascript code isn't wrapped.

In ASP.NET, when should I use Session.Clear() rather than Session.Abandon()?

I had this issue and tried both, but had to settle for removing crap like "pageEditState", but not removing user info lest I have to look it up again.

public static void RemoveEverythingButUserInfo()
    foreach (String o in HttpContext.Current.Session.Keys)
        if (o != "UserInfoIDontWantToAskForAgain")

Node/Express file upload

If you are using Node.js Express and Typescript here is a working example, this works with javascript also, just change the let to var and the import to includes etc...

first import the following make sure you install formidable by running the following command:

npm install formidable

than import the following:

  import * as formidable from 'formidable';
  import * as fs from 'fs';

then your function like bellow:

    uploadFile(req, res) {
    let form = new formidable.IncomingForm();
    form.parse(req, function (err, fields, files) {
        let oldpath = files.file.path;
        let newpath = 'C:/test/' +;
        fs.rename(oldpath, newpath, function (err) {
            if (err) throw err;
            res.write('File uploaded and moved!');

What is the time complexity of indexing, inserting and removing from common data structures?

Keep in mind that unless you're writing your own data structure (e.g. linked list in C), it can depend dramatically on the implementation of data structures in your language/framework of choice. As an example, take a look at the benchmarks of Apple's CFArray over at Ridiculous Fish. In this case, the data type, a CFArray from Apple's CoreFoundation framework, actually changes data structures depending on how many objects are actually in the array - changing from linear time to constant time at around 30,000 objects.

This is actually one of the beautiful things about object-oriented programming - you don't need to know how it works, just that it works, and the 'how it works' can change depending on requirements.

How do I drag and drop files into an application?

You need to be aware of a gotcha. Any class that you pass around as the DataObject in the drag/drop operation has to be Serializable. So if you try and pass an object, and it is not working, ensure it can be serialized as that is almost certainly the problem. This has caught me out a couple of times!

Ajax Upload image

Image upload using ajax and check image format and upload max size   

<form class='form-horizontal' method="POST"  id='document_form' enctype="multipart/form-data">
                                    <div class='optionBox1'>
                                        <div class='row inviteInputWrap1 block1'>
                                            <div class='col-3'>
                                                <label class='col-form-label'>Name</label>
                                                <input type='text' class='form-control form-control-sm' name='name[]' id='name' Value=''>
                                            <div class='col-3'>
                                                <label class='col-form-label'>File</label>
                                                <input type='file' class='form-control form-control-sm' name='file[]' id='file' Value=''>
                                            <div class='col-3'>
                                                <span class='deleteInviteWrap1 remove1 d-none'>
                                                    <i class='fas fa-trash'></i>
                                        <div class='row'>
                                             <div class='col-8 pl-3 pb-4 mt-4'>
                                                <span class='btn btn-info add1 pr-3'>+ Add More</span>
                                                 <button class='btn btn-primary'>Submit</button> 
       submitHandler: function (form) 
                    url : "action1.php",
                    type : "POST",
                    data : new FormData(form),
                    mimeType: "multipart/form-data",
                    contentType: false,
                    cache: false,
                    processData: false,
                    success: function(data)
                        if(data.status =='success')
                                 swal("Document has been successfully uploaded!", {
                                    icon: "success",
                                swal('Oh noes!', "Error in document upload. Please contact to administrator", "error");
                        swal ( "Ops!" ,  "error in document upload." ,  "error" );
        rules: {
            "name[]": {
              required: true
          "file[]": {
              required: true,
              extension: "jpg,jpeg,png,pdf,doc",
              filesize :2000000 
        messages: {
            "name[]": {
            required: "Please enter name"
          "file[]": {
            required: "Please enter file",
            extension :'Please upload only jpg,jpeg,png,pdf,doc'
        errorElement: 'span',
        errorPlacement: function (error, element) {
        highlight: function (element, errorClass, validClass) {
        unhighlight: function (element, errorClass, validClass) {
      $.validator.addMethod('filesize', function(value, element, param) {
         return this.optional(element) || (element.files[0].size <= param)
        }, 'File size must be less than 2 MB');

Concrete Javascript Regex for Accented Characters (Diacritics)



  • \pL - matches any kind of letter from any language
  • \pM - atches a character intended to be combined with another character (e.g. accents, umlauts, enclosing boxes, etc.)
  • \p{Zs} - matches a whitespace character that is invisible, but does take up space
  • u - Pattern and subject strings are treated as UTF-8

Unlike other proposed regex (such as [A-Za-zÀ-ÖØ-öø-ÿ]), this will work with all language specific characters, e.g. Šš is matched by this rule, but not matched by others on this page.

Unfortunately, natively JavaScript does not support these classes. However, you can use xregexp, e.g.

const XRegExp = require('xregexp');

const isInputRealHumanName = (input: string): boolean => {
  return XRegExp('^[\\pL\\pM-]+ [\\pL\\pM-]+$', 'u').test(input);

Selecting all text in HTML text input when clicked

I was looking for a CSS-only solution and found this works for iOS browsers (tested safari and chrome).

It does not have the same behavior on desktop chrome, but the pain of selecting is not as great there because you have a lot more options as a user (double-click, ctrl-a, etc):

.select-all-on-touch {
    -webkit-user-select: all;
    user-select: all;

NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)' on a null object reference

called_from must be null. Add a test against that condition like

if (called_from != null && called_from.equalsIgnoreCase("add")) {

or you could use Yoda conditions (per the Advantages in the linked Wikipedia article it can also solve some types of unsafe null behavior they can be described as placing the constant portion of the expression on the left side of the conditional statement)

if ("add".equalsIgnoreCase(called_from)) { // <-- safe if called_from is null

blur() vs. onblur()

Contrary to what pointy says, the blur() method does exist and is a part of the w3c standard. The following exaple will work in every modern browser (including IE):

        <title>Javascript test</title>
        <script type="text/javascript" language="javascript">
            window.onload = function()
                var field = document.getElementById("field");
                var link = document.getElementById("link");
                var output = document.getElementById("output");

                field.onfocus = function() { output.innerHTML += "<br/>field.onfocus()"; };
                field.onblur = function() { output.innerHTML += "<br/>field.onblur()"; };
                link.onmouseover = function() { field.blur(); };
        <form name="MyForm">
            <input type="text" name="field" id="field" />
            <a href="javascript:void(0);" id="link">Blur field on hover</a>
            <div id="output"></div>

Note that I used link.onmouseover instead of link.onclick, because otherwise the click itself would have removed the focus.

How to check the exit status using an if statement

Every command that runs has an exit status.

That check is looking at the exit status of the command that finished most recently before that line runs.

If you want your script to exit when that test returns true (the previous command failed) then you put exit 1 (or whatever) inside that if block after the echo.

That being said if you are running the command and wanting to test its output using the following is often more straight-forward.

if some_command; then
    echo command returned true
    echo command returned some error

Or to turn that around use ! for negation

if ! some_command; then
    echo command returned some error
    echo command returned true

Note though that neither of those cares what the error code is. If you know you only care about a specific error code then you need to check $? manually.

'if' statement in jinja2 template

We need to remember that the {% endif %} comes after the {% else %}.

So this is an example:

{% if someTest %}
     <p> Something is True </p>
{% else %}
     <p> Something is False </p>
{% endif %}

Fully custom validation error message with Rails

A unique approach I haven't seen anyone mention!

The only way I was able to get all the customisation I wanted was to use an after_validation callback to allow me to manipulate the error message.

  1. Allow the validation message to be created as normal, you don't need to try and change it in the validation helper.

  2. create an after_validation callback that will replace that validation message in the back-end before it gets to the view.

  3. In the after_validation method you can do anything you want with the validation message, just like a normal string! You can even use dynamic values and insert them into the validation message.

#this could be any validation
validates_presence_of :song_rep_xyz, :message => "whatever you want - who cares - we will replace you later"

after_validation :replace_validation_message

def replace_validation_message
    custom_value = #any value you would like
    errors.messages[:name_of_the_attribute] = ["^This is the replacement message where 
    you can now add your own dynamic values!!! #{custom_value}"]

The after_validation method will have far greater scope than the built in rails validation helper, so you will be able to access the object you are validating like you are trying to do with object.file_name. Which does not work in the validation helper where you are trying to call it.

Note: we use the ^ to get rid of the attribute name at the beginning of the validation as @Rystraum pointed out referencing this gem

TypeError: can't use a string pattern on a bytes-like object in re.findall()

You want to convert html (a byte-like object) into a string using .decode, e.g. html ='utf-8').

See Convert bytes to a Python String

How to determine total number of open/active connections in ms sql server 2005

I know this is old, but thought it would be a good idea to update. If an accurate count is needed, then column ECID should probably be filtered as well. A SPID with parallel threads can show up multiple times in sysprocesses and filtering ECID=0 will return the primary thread for each SPID.

    DB_NAME(dbid) as DBName, 
    COUNT(dbid) as NumberOfConnections,
    loginame as LoginName
    sys.sysprocesses with (nolock)
    dbid > 0
    and ecid=0
    dbid, loginame

Name attribute in @Entity and @Table

@Table's name attribute is the actual table name. @Entitiy's name is useful if you have two @Entity classes with the same name and you need a way to differentiate them when running queries.

Python : How to parse the Body from a raw email , given that raw email does not have a "Body" tag or anything

There is very good package available to parse the email contents with proper documentation.

import mailparser

mail = mailparser.parse_from_file(f)
mail = mailparser.parse_from_file_obj(fp)
mail = mailparser.parse_from_string(raw_mail)
mail = mailparser.parse_from_bytes(byte_mail)

How to Use:

mail.attachments: list of all attachments

Prompt for user input in PowerShell

Place this at the top of your script. It will cause the script to prompt the user for a password. The resulting password can then be used elsewhere in your script via $pw.

     [Parameter(Mandatory=$true, Position=0, HelpMessage="Password?")]

   $pw = [Runtime.InteropServices.Marshal]::PtrToStringAuto([Runtime.InteropServices.Marshal]::SecureStringToBSTR($password))

If you want to debug and see the value of the password you just read, use:

   write-host $pw

Your project contains error(s), please fix it before running it

That usually comes from errors in the build path.

If you're using eclipse, there is a view you can add that lists all the errors called "Problems":

enter image description here

Otherwise, you can try to clean the project, and that usually solves a few problems.

Finally, if you add or alter resources from outside your IDE, you'll want to reload the resources and clean.

EDIT (Comment by anonymous user)

This can also be caused by an out of date "Debug Certificate" fixed as follows:


Delete your debug certificate under ~/.android/debug.keystore (on Linux and Mac OS X); the directory is something like %USERPROFILE%/.androidon Windows.

The Eclipse plugin should then generate a new certificate when you next try to build a debug package. You may need to clean and then build to generate the certificate.

This is also another fix for the "setContentView(R.layout.main);" error that says it cannot find R.layout.main when it is actually generated. (R cannot be resolved to a variable).

This is also another fix for the error "Your project has errors..." and you cannot find any. Clean and rebuild are still necessary after generating a new debug certificate.

How to generate the JPA entity Metamodel?

For eclipselink, only the following dependency is sufficient to generate metamodel. Nothing else is needed.


How to suspend/resume a process in Windows?

PsSuspend command line utility from SysInternals suite. It suspends / resumes a process by its id.

iOS 7.0 No code signing identities found

Obviously this issue has different causes. :)

For my case, my account log in expired... I solved it by simply:

XCode -> Preferences -> Account -> Apple IDs -> Select the related ID and renew the log in...

Hope this helps!

Encoding as Base64 in Java

You can also convert using Base64 encoding. To do this, you can use the javax.xml.bind.DatatypeConverter#printBase64Binary method.

For example:

byte[] salt = new byte[] { 50, 111, 8, 53, 86, 35, -19, -47 };

Close window automatically after printing dialog closes

setTimeout(function () { window.print(); }, 500);
        window.onfocus = function () { setTimeout(function () { window.close(); }, 500); }

It's work perfectly for me. Hope it helps

How to write multiple line string using Bash with variables?

The heredoc solutions are certainly the most common way to do this. Other common solutions are:

echo 'line 1, '"${kernel}"'
line 2,
line 3, '"${distro}"'
line 4' > /etc/myconfig.conf


exec 3>&1 # Save current stdout
exec > /etc/myconfig.conf
echo line 1, ${kernel}
echo line 2, 
echo line 3, ${distro}
exec 1>&3  # Restore stdout

What is setContentView(R.layout.main)?

You can set content view (or design) of an activity. For example you can do it like this too :

public void onCreate(Bundle savedinstanceState) {

    Button testButon = new Button(this);


Also watch this tutorial too.

Decode Hex String in Python 3

Something like:

>>> bytes.fromhex('4a4b4c').decode('utf-8')

Just put the actual encoding you are using.

Can I apply multiple background colors with CSS3?

You can use as many colors and images as you desire.

Please note that the priority with which the background images are rendered is FILO, the first specified image is on the top layer, the last specified image is on the bottom layer (see the snippet).

#composition {_x000D_
    width: 400px;_x000D_
    height: 200px;_x000D_
        linear-gradient(to right, #FF0000, #FF0000), /* gradient 1 as solid color */_x000D_
        linear-gradient(to right, #00FF00, #00FF00), /* gradient 2 as solid color */_x000D_
        linear-gradient(to right, #0000FF, #0000FF), /* gradient 3 as solid color */_x000D_
        url(''); /* image */_x000D_
    background-repeat: no-repeat; /* same as no-repeat, no-repeat, no-repeat */_x000D_
        0 0, /* gradient 1 */_x000D_
        20px 0, /* gradient 2 */_x000D_
        40px 0, /* gradient 3 */_x000D_
        0 0; /* image position */_x000D_
        30px 30px,_x000D_
        30px 30px,_x000D_
        30px 30px,_x000D_
        100% 100%;_x000D_
<div id="composition">_x000D_

why is plotting with Matplotlib so slow?

This may not apply to many of you, but I'm usually operating my computers under Linux, so by default I save my matplotlib plots as PNG and SVG. This works fine under Linux but is unbearably slow on my Windows 7 installations [MiKTeX under Python(x,y) or Anaconda], so I've taken to adding this code, and things work fine over there again:

import platform     # Don't save as SVG if running under Windows.
# Plot code goes here.
fig.savefig('figure_name.png', dpi = 200)
if platform.system() != 'Windows':
    # In my installations of Windows 7, it takes an inordinate amount of time to save
    # graphs as .svg files, so on that platform I've disabled the call that does so.
    # The first run of a script is still a little slow while everything is loaded in,
    # but execution times of subsequent runs are improved immensely.

CronJob not running

Sometimes the command that cron needs to run is in a directory where cron has no access, typically on systems where users' home directories' permissions are 700 and the command is in that directory.

Changing image size in Markdown

The sheer <img ... width="50%"> said above, did work on my Github document.

However my real issue was, that the image was inside a table cell, just compressing the text in the beside cell. So the other way was to set columns width in Markdown tables, but the solutions did not really seem enough markdownish for my morning.

At last I solved both problems by simply forcing the beside text cell with as much "& nbsp;" as I needed.

I hope this helps. Bye and thanks everybody.

Passing variable from Form to Module in VBA

Don't declare the variable in the userform. Declare it as Public in the module.

Public pass As String

In the Userform

Private Sub CommandButton1_Click()
    pass = UserForm1.TextBox1
    Unload UserForm1
End Sub

In the Module

Public pass As String

Public Sub Login()
    '~~> Rest of the code
    driver.findElementByName("PASSWORD").SendKeys pass
    '~~> Rest of the code
End Sub

You might want to also add an additional check just before calling the driver.find... line?

If Len(Trim(pass)) <> 0 Then

This will ensure that a blank string is not passed.

Skip rows during csv import pandas

Also be sure that your file is actually a CSV file. For example, if you had an .xls file, and simply changed the file extension to .csv, the file won't import and will give the error above. To check to see if this is your problem open the file in excel and it will likely say:

"The file format and extension of 'Filename.csv' don't match. The file could be corrupted or unsafe. Unless you trust its source, don't open it. Do you want to open it anyway?"

To fix the file: open the file in Excel, click "Save As", Choose the file format to save as (use .cvs), then replace the existing file.

This was my problem, and fixed the error for me.

How to overcome "datetime.datetime not JSON serializable"?

def j_serial(o):     # self contained
    from datetime import datetime, date
    return str(o).split('.')[0] if isinstance(o, (datetime, date)) else None

Usage of above utility:

import datetime
serial_d = j_serial(
if serial_d:
    print(serial_d)  # output: 2018-02-28 02:23:15

How to set time to midnight for current day?

You can use the Date property of the DateTime object - eg

DateTime midnight = DateTime.Now.Date;

So your code example becomes

private DateTime _Begin = DateTime.Now.Date;
public DateTime Begin { get { return _Begin; } set { _Begin = value; } }

PS. going back to your original code setting the hours to 12 will give you time of noon for the current day, so instead you could have used 0...

var now = DateTime.Now;
new DateTime(now.Year, now.Month, now.Day, 0, 0, 0);

Rails 4: assets not loading in production

In rails 4 you need to make the changes below:

config.assets.compile = true
config.assets.precompile =  ['*.js', '*.css', '*.css.erb'] 

This works with me. use following command to pre-compile assets

RAILS_ENV=production bundle exec rake assets:precompile

Best of luck!

How do I style (css) radio buttons and labels?

For any CSS3-enabled browser you can use an adjacent sibling selector for styling your labels

input:checked + label {
    color: white;

MDN's browser compatibility table says essentially all of the current, popular browsers (Chrome, IE, Firefox, Safari), on both desktop and mobile, are compatible.

ORACLE: Updating multiple columns at once

I guess the issue here is that you are updating INV_DISCOUNT and the INV_TOTAL uses the INV_DISCOUNT. so that is the issue here. You can use returning clause of update statement to use the new INV_DISCOUNT and use it to update INV_TOTAL.

this is a generic example let me know if this explains the point i mentioned

    empName VARCHAR2(50);
    empSalary NUMBER(7,2);      
    UPDATE emp
    SET sal = sal + 1000
    WHERE empno = 7499
    RETURNING ename, sal
    INTO empName, empSalary;

    DBMS_OUTPUT.put_line('Name of Employee: ' || empName);
    DBMS_OUTPUT.put_line('New Salary: ' || empSalary);

curl_init() function not working

function curl_int(); cause server error,install sudo apt-get install php5-curl restart apache2 server .. it will work like charm

MySQL select all rows from last month until (now() - 1 month), for comparative purposes

FROM table 

See the docs for info on DATE_SUB, ADDDATE, LAST_DAY and other useful datetime functions.

How to export specific request to file using postman?

The workaround is to export the collection as explained in other answers or references. This will export all requests in that collection to JSON file.

Then edit the JSON file to remove the requests you do not want using any editor; this is very simple.

Look for "item" collection in file. This contains all your requests; one in each item. Remove the items you do not want to keep.

If you import this edited file in Postman where original collection already exists, Postman will ask you if you want to replace it or create a copy. If you want to avoid this, you may consider changing "_postman_id" and "name" under "info". If original collection will not exist while importing edited collection, then this change is not needed.


What is an AssertionError? In which case should I throw it from my own code?

AssertionError is an Unchecked Exception which rises explicitly by programmer or by API Developer to indicate that assert statement fails.




If x is not greater than 10 then you will get runtime exception saying AssertionError.

How to resolve symbolic links in a shell script

readlink -e [filepath]

seems to be exactly what you're asking for - it accepts an arbirary path, resolves all symlinks, and returns the "real" path - and it's "standard *nix" that likely all systems already have

Exiting from python Command Line

This message is the __str__ attribute of exit

look at these examples :


>>> print exit
Use exit() or Ctrl-D (i.e. EOF) to exit


>>> exit.__str__()
'Use exit() or Ctrl-D (i.e. EOF) to exit'


>>> getattr(exit, '__str__')()
'Use exit() or Ctrl-D (i.e. EOF) to exit'

How do I get user IP address in django?

No More confusion In the recent versions of Django it is mentioned clearly that the Ip address of the client is available at


for more info check the Django Docs

How do you give iframe 100% height

You can do it with CSS:

<iframe style="position: absolute; height: 100%; border: none"></iframe>

Be aware that this will by default place it in the upper-left corner of the page, but I guess that is what you want to achieve. You can position with the left,right, top and bottom CSS properties.

TypeError: document.getElementbyId is not a function

JavaScript is case-sensitive. The b in getElementbyId should be capitalized.

var content = document.getElementById("edit").innerHTML;

Is there a good Valgrind substitute for Windows?

We are just completing a Memory Safety checking tool for Windows, that handles GCC and Micrsoft Visual C (not C++ yet), and are looking for Beta testers.

EDIT June 12, 2011: Not Beta anymore, now production for GCC and Microsoft Visual Studio C.

Calling a Function defined inside another function in Javascript

The scoping is correct as you've noted. However, you are not calling the inner function anywhere.

You can do either:

function outer() { 

    // when you define it this way, the inner function will be accessible only from 
    // inside the outer function

    function inner() {
    inner(); // call it


function outer() { 
    this.inner = function() {

<input type="button" onclick="(new outer()).inner();" value="ACTION">?

Pass a data.frame column name to a function

Personally I think that passing the column as a string is pretty ugly. I like to do something like:

get.max <- function(column,data=NULL){
    column<-eval(substitute(column),data, parent.frame())

which will yield:

> get.max(mpg,mtcars)
[1] 33.9
> get.max(c(1,2,3,4,5))
[1] 5

Notice how the specification of a data.frame is optional. you can even work with functions of your columns:

> get.max(1/mpg,mtcars)
[1] 0.09615385

How to lose margin/padding in UITextView?

In case anyone looking for latest Swift version then below code is working fine with Xcode 10.2 and Swift 4.2

yourTextView.textContainerInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)

Checking for a null int value from a Java ResultSet

Another nice way of checking, if you have control the SQL, is to add a default value in the query itself for your int column. Then just check for that value.

e.g for an Oracle database, use NVL


then check

if (rs.getInt('ID_PARENT') != -999)

Of course this also is under the assumption that there is a value that wouldn't normally be found in the column.

Find the IP address of the client in an SSH session

Simplest command to get the last 10 users logged in to the machine is last|head. To get all the users, simply use last command

Reading a column from CSV file using JAVA

You are not changing the value of line. It should be something like this.


public class InsertValuesIntoTestDb {

  public static void main(String[] args) throws Exception {
      String splitBy = ",";
      BufferedReader br = new BufferedReader(new FileReader("test.csv"));
      while((line = br.readLine()) != null){
           String[] b = line.split(splitBy);


readLine returns each line and only returns null when there is nothing left. The above code sets line and then checks if it is null.

Youtube iframe wmode issue

Try adding ?wmode=transparent to the end of the URL. Worked for me.

Java: How to convert List to Map

Short and sweet.

Using Java 8 you can do following :

Map<Key, Value> result= results

Value can be any object you use.

printf \t option

A tab is a tab. How many spaces it consumes is a display issue, and depends on the settings of your shell.

If you want to control the width of your data, then you could use the width sub-specifiers in the printf format string. Eg. :

printf("%5d", 2);

It's not a complete solution (if the value is longer than 5 characters, it will not be truncated), but might be ok for your needs.

If you want complete control, you'll probably have to implement it yourself.

Utilizing multi core for tar+gzip/bzip compression/decompression

You can use pigz instead of gzip, which does gzip compression on multiple cores. Instead of using the -z option, you would pipe it through pigz:

tar cf - paths-to-archive | pigz > archive.tar.gz

By default, pigz uses the number of available cores, or eight if it could not query that. You can ask for more with -p n, e.g. -p 32. pigz has the same options as gzip, so you can request better compression with -9. E.g.

tar cf - paths-to-archive | pigz -9 -p 32 > archive.tar.gz

Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop

Since the question has been already answered i.e. the best way is to use the remove method of the iterator object, I would go into the specifics of the place where the error "java.util.ConcurrentModificationException" is thrown.

Every collection class has a private class which implements the Iterator interface and provides methods like next(), remove() and hasNext().

The code for next looks something like this...

public E next() {
    try {
        E next = get(cursor);
        lastRet = cursor++;
        return next;
    } catch(IndexOutOfBoundsException e) {
        throw new NoSuchElementException();

Here the method checkForComodification is implemented as

final void checkForComodification() {
    if (modCount != expectedModCount)
        throw new ConcurrentModificationException();

So, as you can see, if you explicitly try to remove an element from the collection. It results in modCount getting different from expectedModCount, resulting in the exception ConcurrentModificationException.

Why my $.ajax showing "preflight is invalid redirect error"?

My problem was that POST requests need trailing slashes '/'.