Programs & Examples On #Vcdiff

Python 3 Online Interpreter / Shell

I recently came across Python 3 interpreter at CompileOnline.

TypeError: argument of type 'NoneType' is not iterable

If a function does not return anything, e.g.:

def test():

it has an implicit return value of None.

Thus, as your pick* methods do not return anything, e.g.:

def pickEasy():
    word = random.choice(easyWords)
    word = str(word)
    for i in range(1, len(word) + 1):

the lines that call them, e.g.:

word = pickEasy()

set word to None, so wordInput in getInput is None. This means that:

if guess in wordInput:

is the equivalent of:

if guess in None:

and None is an instance of NoneType which does not provide iterator/iteration functionality, so you get that type error.

The fix is to add the return type:

def pickEasy():
    word = random.choice(easyWords)
    word = str(word)
    for i in range(1, len(word) + 1):
    return word

How do I measure separate CPU core usage for a process?

The ps solution was nearly what I needed and with some bash thrown in does exactly what the original question asked for: to see per-core usage of specific processes

This shows per-core usage of multi-threaded processes too.

Use like: cpustat `pgrep processname` `pgrep otherprocessname` ...


while [ $# != 0 ]; do
        pids=("${pids[@]}" "$1")

if [ -z "${pids[0]}" ]; then
        echo "Usage: $0 <pid1> [pid2] ..."
        exit 1

for pid in "${pids[@]}"; do
        if [ ! -e /proc/$pid ]; then
                echo "Error: pid $pid doesn't exist"
                exit 1

while [ true ]; do
        echo -e "\033[H\033[J"
        for pid in "${pids[@]}"; do
                ps -p $pid -L -o pid,tid,psr,pcpu,comm=
        sleep 1

Note: These stats are based on process lifetime, not the last X seconds, so you'll need to restart your process to reset the counter.

How to change the text color of first select option

You can do this by using CSS: JSFiddle


    <option>Text 1</option>
    <option>Text 2</option>
    <option>Text 3</option>


select option:first-child { color:red; }

Or if you absolutely need to use JavaScript (not adviced for this): JSFiddle


$(function() {
    $("select option:first-child").addClass("highlight");


.highlight { color:red; }

Disable time in bootstrap date time picker

Check the below snippet

<div class="container">
<div class="row">
    <div class='col-sm-6'>
        <div class="form-group">
            <div class='input-group date' id='datetimepicker4'>
                <input type='text' class="form-control" />
                <span class="input-group-addon"><span class="glyphicon glyphicon-time"></span>
    <script type="text/javascript">
        $(function() {              
           // Bootstrap DateTimePicker v4
                 format: 'DD/MM/YYYY'

You can refer for documentation and other functions in detail. This should work.

Update to support i18n

Use localized formats of moment.js:

  • L for date only
  • LT for time only
  • L LT for date and time

See other localized formats in the moment.js documentation (

Laravel: How to Get Current Route Name? (v5 ... v7)

Shortest way is Route facade \Route::current()->getName()

This also works in laravel 5.4.*

When does System.gc() do something?

I can't think of a specific example when it is good to run explicit GC.

In general, running explicit GC can actually cause more harm than good, because an explicit gc will trigger a full collection, which takes significantly longer as it goes through every object. If this explicit gc ends up being called repeatedly it could easily lead to a slow application as a lot of time is spent running full GCs.

Alternatively if going over the heap with a heap analyzer and you suspect a library component to be calling explicit GC's you can turn it off adding: gc=-XX:+DisableExplicitGC to the JVM parameters.

Center Div inside another (100% width) div

Just add margin: 0 auto; to the inside div.

Change header text of columns in a GridView

You should do that in GridView's RowDataBound event which is triggered for every GridViewRow after it was databound.

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    if (e.Row.RowType == DataControlRowType.Header)
        e.Row.Cells[0].Text = "Date";

or you can set AutogenerateColumns to false and add the columns declaratively on aspx:

<asp:gridview id="GridView1" 
  emptydatatext="No data available." 
         <asp:BoundField DataField="DateField" HeaderText="Date" 
            SortExpression="DateField" />

How to sum all values in a column in Jaspersoft iReport Designer?

iReports Custom Fields for columns (sum, average, etc)

  1. Right-Click on Variables and click Create Variable

  2. Click on the new variable

    a. Notice the properties on the right

  3. Rename the variable accordingly

  4. Change the Value Class Name to the correct Data Type

    a. You can search by clicking the 3 dots

  5. Select the correct type of calculation

  6. Change the Expression

    a. Click the little icon

    b. Select the column you are looking to do the calculation for

    c. Click finish

  7. Set Initial Value Expression to 0

  8. Set the increment type to none

  9. Leave Incrementer Factory Class Name blank
  10. Set the Reset Type (usually report)

  11. Drag a new Text Field to stage (Usually in Last Page Footer, or Column Footer)

  12. Double Click the new Text Field
  13. Clear the expression “Text Field”
  14. Select the new variable

  15. Click finish

  16. Put the new text in a desirable position ?

For Restful API, can GET method use json data?

To answer your question, yes you may pass JSON in the URI as part of a GET request (provided you URL-encode). However, considering your reason for doing this is due to the length of the URI, using JSON will be self-defeating (introducing more characters than required).

I suggest you send your parameters in body of a POST request, either in regular CGI style (param1=val1&param2=val2) or JSON (parsed by your API upon receipt)

Combine [NgStyle] With Condition (if..else)

You can use this as follows:

<div [style.background-image]="value ? 'url(' + imgLink + ')' : 'url(' + defaultLink + ')'"></div>

Should I use the datetime or timestamp data type in MySQL?

If you want to GUARANTEE your application will NOT function in February, 2038, use TIMESTAMP. Refer to your REFMAN for the RANGE of dates supported.

How to convert a Kotlin source file to a Java source file

I compile Kotlin to byte code and then de-compile that to Java. I compile with the Kotlin compiler and de-compile with cfr.

My project is here.

This allows me to compile this:

package functionsiiiandiiilambdas.functions.p01tailiiirecursive

tailrec fun findFixPoint(x: Double = 1.0): Double =
        if (x == Math.cos(x)) x else findFixPoint(Math.cos(x))

To this:

package functionsiiiandiiilambdas.functions.p01tailiiirecursive;

public final class ExampleKt {
  public static final double findFixPoint(double x) {
    while (x != Math.cos(x)) {
      x = Math.cos(x);
    return x;

  public static /* bridge */ /* synthetic */ double findFixPoint$default(
      double d, int n, Object object) {
    if ((n & 1) != 0) {
      d = 1.0;
    return ExampleKt.findFixPoint(d);

mysql datatype for telephone number and address

i would use a varchar for telephone numbers. that way you can also store + and (), which is sometimes seen in tel numbers (as you mentioned yourself). and you don't have to worry about using up all bits in integers.

Configuring Git over SSH to login once

Extending Muein's thoughts for those who prefer to edit files directly over running commands in git-bash or terminal.

Go to the .git directory of your project (project root on your local machine) and open the 'config' file. Then look for [remote "origin"] and set the url config as follows:

[remote "origin"]
    #the address part will be different depending upon the service you're using github, bitbucket, unfuddle etc.
    url = [email protected]:<username>/<projectname>.git

How to kill all active and inactive oracle sessions for user

  FOR r IN (select sid,serial# from v$session where username='user')
      EXECUTE IMMEDIATE 'alter system kill session ''' || r.sid  || ',' 
        || r.serial# || ''' immediate';

This should work - I just changed your script to add the immediate keyword. As the previous answers pointed out, the kill session only marks the sessions for killing; it does not do so immediately but later when convenient.

From your question, it seemed you are expecting to see the result immediately. So immediate keyword is used to force this.

TypeScript: Creating an empty typed container array

Okay you got the syntax wrong here, correct way to do this is:

var arr: Criminal[] = [];

I'm assuming you are using var so that means declaring it somewhere inside the func(),my suggestion would be use let instead of var.

If declaring it as c class property usse acces modifiers like private, public, protected.

In jQuery, how do I get the value of a radio button when they all have the same name?

There is another way also. Try below code


      $("input[name='gender']").on("click", function() {

Convert array of strings into a string in Java

Try the Arrays.deepToString method.

Returns a string representation of the "deep contents" of the specified array. If the array contains other arrays as elements, the string representation contains their contents and so on. This method is designed for converting multidimensional arrays to strings

Remove part of a string

Here's the strsplit solution if s is a vector:

> s <- c("TGAS_1121", "MGAS_1432")
> s1 <- sapply(strsplit(s, split='_', fixed=TRUE), function(x) (x[2]))
> s1
[1] "1121" "1432"

Open Bootstrap Modal from code-behind


I've seen this strange behavior before in jQuery widgets. Part of the key is to put the updatepanel inside the modal. This allows the DOM of the updatepanel to "stay with" the modal (however it works with bootstrap).

Sort divs in jQuery based on attribute 'data-sort'?

Use this function

   var result = $('div').sort(function (a, b) {

      var contentA =parseInt( $(a).data('sort'));
      var contentB =parseInt( $(b).data('sort'));
      return (contentA < contentB) ? -1 : (contentA > contentB) ? 1 : 0;


You can call this function just after adding new divs.

If you want to preserve javascript events within the divs, DO NOT USE html replace as in the above example. Instead use:

$(targetSelector).sort(function (a, b) {
    // ...

How to add anchor tags dynamically to a div in Javascript?

var newA = document.createElement('a');
newA.innerHTML = "link text";

A method to count occurrences in a list

Your outer loop is looping over all the words in the list. It's unnecessary and will cause you problems. Remove it and it should work properly.

Iterating through map in template

Check the Variables section in the Go template docs. A range may declare two variables, separated by a comma. The following should work:

{{ range $key, $value := . }}
   <li><strong>{{ $key }}</strong>: {{ $value }}</li>
{{ end }}

What is the proper declaration of main in C++?

The two valid mains are int main() and int main(int, char*[]). Any thing else may or may not compile. If main doesn't explicitly return a value, 0 is implicitly returned.

Angular cli generate a service and include the provider in one step

run the below code in Terminal

makesure You are inside your project folder in terminal

ng g s servicename --module=app.module

How to pass html string to webview on android

I was using some buttons with some events, converted image file coming from server. Loading normal data wasn't working for me, converting into Base64 working just fine.

String unencodedHtml ="<html><body>'%28' is the code for '('</body></html>";
tring encodedHtml = Base64.encodeToString(unencodedHtml.getBytes(), Base64.NO_PADDING);
webView.loadData(encodedHtml, "text/html", "base64");

Find details on WebView

Spring Boot - Loading Initial Data

This will also work.

    CommandLineRunner init (StudentRepo studentRepo){
        return args -> {
            // Adding two students objects
            List<String> names = Arrays.asList("udara", "sampath");
            names.forEach(name -> Student(name)));

How to set default value for form field in Symfony2?

If you need to set default value and your form relates to the entity, then you should use following approach:

// buildForm() method
public function buildForm(FormBuilderInterface $builder, array $options) {
            'data' => isset($options['data']) ? $options['data']->getMyField() : 'my default value'

Otherwise, myField always will be set to default value, instead of getting value from entity.

What is a Python egg?

Note: Egg packaging has been superseded by Wheel packaging.

Same concept as a .jar file in Java, it is a .zip file with some metadata files renamed .egg, for distributing code as bundles.

Specifically: The Internal Structure of Python Eggs

A "Python egg" is a logical structure embodying the release of a specific version of a Python project, comprising its code, resources, and metadata. There are multiple formats that can be used to physically encode a Python egg, and others can be developed. However, a key principle of Python eggs is that they should be discoverable and importable. That is, it should be possible for a Python application to easily and efficiently find out what eggs are present on a system, and to ensure that the desired eggs' contents are importable.

The .egg format is well-suited to distribution and the easy uninstallation or upgrades of code, since the project is essentially self-contained within a single directory or file, unmingled with any other projects' code or resources. It also makes it possible to have multiple versions of a project simultaneously installed, such that individual programs can select the versions they wish to use.

What's the difference between Instant and LocalDateTime?

Table of all date-time types in Java, both modern and legacy


Instant and LocalDateTime are two entirely different animals: One represents a moment, the other does not.

  • Instant represents a moment, a specific point in the timeline.
  • LocalDateTime represents a date and a time-of-day. But lacking a time zone or offset-from-UTC, this class cannot represent a moment. It represents potential moments along a range of about 26 to 27 hours, the range of all time zones around the globe. A LocalDateTime value is inherently ambiguous.

Incorrect Presumption

LocalDateTime is rather date/clock representation including time-zones for humans.

Your statement is incorrect: A LocalDateTime has no time zone. Having no time zone is the entire point of that class.

To quote that class’ doc:

This class does not store or represent a time-zone. Instead, it is a description of the date, as used for birthdays, combined with the local time as seen on a wall clock. It cannot represent an instant on the time-line without additional information such as an offset or time-zone.

So Local… means “not zoned, no offset”.


enter image description here

An Instant is a moment on the timeline in UTC, a count of nanoseconds since the epoch of the first moment of 1970 UTC (basically, see class doc for nitty-gritty details). Since most of your business logic, data storage, and data exchange should be in UTC, this is a handy class to be used often.

Instant instant = ;  // Capture the current moment in UTC.


enter image description here

The class OffsetDateTime class represents a moment as a date and time with a context of some number of hours-minutes-seconds ahead of, or behind, UTC. The amount of offset, the number of hours-minutes-seconds, is represented by the ZoneOffset class.

If the number of hours-minutes-seconds is zero, an OffsetDateTime represents a moment in UTC the same as an Instant.


enter image description here

The ZoneOffset class represents an offset-from-UTC, a number of hours-minutes-seconds ahead of UTC or behind UTC.

A ZoneOffset is merely a number of hours-minutes-seconds, nothing more. A zone is much more, having a name and a history of changes to offset. So using a zone is always preferable to using a mere offset.


enter image description here

A time zone is represented by the ZoneId class.

A new day dawns earlier in Paris than in Montréal, for example. So we need to move the clock’s hands to better reflect noon (when the Sun is directly overhead) for a given region. The further away eastward/westward from the UTC line in west Europe/Africa the larger the offset.

A time zone is a set of rules for handling adjustments and anomalies as practiced by a local community or region. The most common anomaly is the all-too-popular lunacy known as Daylight Saving Time (DST).

A time zone has the history of past rules, present rules, and rules confirmed for the near future.

These rules change more often than you might expect. Be sure to keep your date-time library's rules, usually a copy of the 'tz' database, up to date. Keeping up-to-date is easier than ever now in Java 8 with Oracle releasing a Timezone Updater Tool.

Specify a proper time zone name in the format of Continent/Region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 2-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

Time Zone = Offset + Rules of Adjustments

ZoneId z = ZoneId.of( “Africa/Tunis” ) ; 


enter image description here

Think of ZonedDateTime conceptually as an Instant with an assigned ZoneId.

ZonedDateTime = ( Instant + ZoneId )

To capture the current moment as seen in the wall-clock time used by the people of a particular region (a time zone):

ZonedDateTime zdt = z ) ;  // Pass a `ZoneId` object such as `ZoneId.of( "Europe/Paris" )`. 

Nearly all of your backend, database, business logic, data persistence, data exchange should all be in UTC. But for presentation to users you need to adjust into a time zone expected by the user. This is the purpose of the ZonedDateTime class and the formatter classes used to generate String representations of those date-time values.

ZonedDateTime zdt = instant.atZone( z ) ;
String output = zdt.toString() ;                 // Standard ISO 8601 format.

You can generate text in localized format using DateTimeFormatter.

DateTimeFormatter f = DateTimeFormatter.ofLocalizedDateTime( FormatStyle.FULL ).withLocale( Locale.CANADA_FRENCH ) ; 
String outputFormatted = zdt.format( f ) ;

mardi 30 avril 2019 à 23 h 22 min 55 s heure de l’Inde

LocalDate, LocalTime, LocalDateTime

Diagram showing only a calendar for a LocalDate.

Diagram showing only a clock for a LocalTime.

Diagram showing a calendar plus clock for a LocalDateTime.

The "local" date time classes, LocalDateTime, LocalDate, LocalTime, are a different kind of critter. The are not tied to any one locality or time zone. They are not tied to the timeline. They have no real meaning until you apply them to a locality to find a point on the timeline.

The word “Local” in these class names may be counter-intuitive to the uninitiated. The word means any locality, or every locality, but not a particular locality.

So for business apps, the "Local" types are not often used as they represent just the general idea of a possible date or time not a specific moment on the timeline. Business apps tend to care about the exact moment an invoice arrived, a product shipped for transport, an employee was hired, or the taxi left the garage. So business app developers use Instant and ZonedDateTime classes most commonly.

So when would we use LocalDateTime? In three situations:

  • We want to apply a certain date and time-of-day across multiple locations.
  • We are booking appointments.
  • We have an intended yet undetermined time zone.

Notice that none of these three cases involve a single certain specific point on the timeline, none of these are a moment.

One time-of-day, multiple moments

Sometimes we want to represent a certain time-of-day on a certain date, but want to apply that into multiple localities across time zones.

For example, "Christmas starts at midnight on the 25th of December 2015" is a LocalDateTime. Midnight strikes at different moments in Paris than in Montréal, and different again in Seattle and in Auckland.

LocalDate ld = LocalDate.of( 2018 , Month.DECEMBER , 25 ) ;
LocalTime lt = LocalTime.MIN ;   // 00:00:00
LocalDateTime ldt = LocalDateTime.of( ld , lt ) ;  // Christmas morning anywhere. 

Another example, "Acme Company has a policy that lunchtime starts at 12:30 PM at each of its factories worldwide" is a LocalTime. To have real meaning you need to apply it to the timeline to figure the moment of 12:30 at the Stuttgart factory or 12:30 at the Rabat factory or 12:30 at the Sydney factory.

Booking appointments

Another situation to use LocalDateTime is for booking future events (ex: Dentist appointments). These appointments may be far enough out in the future that you risk politicians redefining the time zone. Politicians often give little forewarning, or even no warning at all. If you mean "3 PM next January 23rd" regardless of how the politicians may play with the clock, then you cannot record a moment – that would see 3 PM turn into 2 PM or 4 PM if that region adopted or dropped Daylight Saving Time, for example.

For appointments, store a LocalDateTime and a ZoneId, kept separately. Later, when generating a schedule, on-the-fly determine a moment by calling LocalDateTime::atZone( ZoneId ) to generate a ZonedDateTime object.

ZonedDateTime zdt = ldt.atZone( z ) ;  // Given a date, a time-of-day, and a time zone, determine a moment, a point on the timeline.

If needed, you can adjust to UTC. Extract an Instant from the ZonedDateTime.

Instant instant = zdt.toInstant() ;  // Adjust from some zone to UTC. Same moment, same point on the timeline, different wall-clock time.

Unknown zone

Some people might use LocalDateTime in a situation where the time zone or offset is unknown.

I consider this case inappropriate and unwise. If a zone or offset is intended but undetermined, you have bad data. That would be like storing a price of a product without knowing the intended currency (dollars, pounds, euros, etc.). Not a good idea.

All date-time types

For completeness, here is a table of all the possible date-time types, both modern and legacy in Java, as well as those defined by the SQL standard. This might help to place the Instant & LocalDateTime classes in a larger context.

Table of all date-time types in Java (both modern & legacy) as well as SQL standard.

Notice the odd choices made by the Java team in designing JDBC 4.2. They chose to support all the java.time times… except for the two most commonly used classes: Instant & ZonedDateTime.

But not to worry. We can easily convert back and forth.

Converting Instant.

// Storing
OffsetDateTime odt = instant.atOffset( ZoneOffset.UTC ) ;
myPreparedStatement.setObject( … , odt ) ;

// Retrieving
OffsetDateTime odt = myResultSet.getObject( … , OffsetDateTime.class ) ;
Instant instant = odt.toInstant() ;

Converting ZonedDateTime.

// Storing
OffsetDateTime odt = zdt.toOffsetDateTime() ;
myPreparedStatement.setObject( … , odt ) ;

// Retrieving
OffsetDateTime odt = myResultSet.getObject( … , OffsetDateTime.class ) ;
ZoneId z = ZoneId.of( "Asia/Kolkata" ) ;
ZonedDateTime zdt = odt.atZone( z ) ; 

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

Table of which java.time library to use with which version of Java or Android

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

How to get multiple selected values from select box in JSP?

It would seem overkill but Spring Forms handles this elegantly. That is of course if you are already using Spring MVC and you want to take advantage of the Spring Forms feature.

// jsp form
    <form:select path="friendlyNumber" items="${friendlyNumberItems}" />

    // the command class
    public class NumberCmd {
      private String[] friendlyNumber;

    // in your Spring MVC controller submit method
    public String manageOrders(@ModelAttribute("nbrCmd") NumberCmd nbrCmd){

       String[] selectedNumbers = nbrCmd.getFriendlyNumber();


How to define static constant in a class in swift

Tried on Playground

class MyClass {

struct Constants { static let testStr = "test" static let testStrLen = testStr.characters.count //testInt will not be accessable by other classes in different swift files private static let testInt = 1 static func singletonFunction() { //accessable print("Print singletonFunction testInt=\(testInt)") var newInt = testStrLen newInt = newInt + 1 print("Print singletonFunction testStr=\(testStr)") } } func ownFunction() { //not accessable //var newInt1 = Constants.testInt + 1 var newInt2 = Constants.testStrLen newInt2 = newInt2 + 1 print("Print ownFunction testStr=\(Constants.testStr)") print("Print ownFunction newInt2=\(newInt2)") } } let newInt = MyClass.Constants.testStrLen print("Print testStr=\(MyClass.Constants.testStr)") print("Print testInt=\(newInt)") let myClass = MyClass() myClass.ownFunction() MyClass.Constants.singletonFunction()

How to programmatically add controls to a form in VB.NET

Dim numberOfButtons As Integer
Dim buttons() as Button

Private Sub MyForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Redim buttons(numberOfbuttons)
    for counter as integer = 0 to numberOfbuttons
        With buttons(counter)
           .Size = (10, 10)
           .Visible = False
           .Location = (55, 33 + counter*13)
           .Text = "Button "+(counter+1).ToString ' or some name from an array you pass from main
           'any other property
        End With
End Sub

If you want to check which of the textboxes have information, or which radio button was clicked, you can iterate through a loop in an OK button.

If you want to be able to click individual array items and have them respond to events, add in the Form_load loop the following:

AddHandler buttons(counter).Clicked AddressOf All_Buttons_Clicked 

then create

Private Sub All_Buttons_Clicked(ByVal sender As System.Object, ByVal e As System.EventArgs)
     'some code here, can check to see which checkbox was changed, which button was clicked, by number or text
End Sub

when you call: objectYouCall.numberOfButtons = initial_value_from_main_program

response_yes_or_no_or_other = objectYouCall.ShowDialog()

For radio buttons, textboxes, same story, different ending.

Completely removing phpMyAdmin

I had same problem. Try the following command. This solved my problem.

sudo apt-get install libapache2-mod-php5

How to call a REST web service API from JavaScript?

I'm surprised nobody has mentioned the new Fetch API, supported by all browsers except IE11 at the time of writing. It simplifies the XMLHttpRequest syntax you see in many of the other examples.

The API includes a lot more, but start with the fetch() method. It takes two arguments:

  1. A URL or an object representing the request.
  2. Optional init object containing the method, headers, body etc.

Simple GET:

const userAction = async () => {
  const response = await fetch('');
  const myJson = await response.json(); //extract JSON from the http response
  // do something with myJson

Recreating the previous top answer, a POST:

const userAction = async () => {
  const response = await fetch('', {
    method: 'POST',
    body: myBody, // string or object
    headers: {
      'Content-Type': 'application/json'
  const myJson = await response.json(); //extract JSON from the http response
  // do something with myJson

Synchronous Requests in Node.js

You should take a look at library called async

and try to use async.series call for your problem.

How do I convert an integer to string as part of a PostgreSQL query?

You can cast an integer to a string in this way


and so in your case

SELECT * FROM table WHERE <some integer>::text = 'string of numbers'

Wireshark vs Firebug vs Fiddler - pros and cons?

None of the above, if you are on a Mac. Use Charles Proxy. It's the best network/request information collecter that I have ever come across. You can view and edit all outgoing requests, and see the responses from those requests in several forms, depending on the type of the response. It costs 50 dollars for a license, but you can download the trial version and see what you think.

If your on Windows, then I would just stay with Fiddler.

Which characters need to be escaped when using Bash?

I presume that you're talking about bash strings. There are different types of strings which have a different set of requirements for escaping. eg. Single quotes strings are different from double quoted strings.

The best reference is the Quoting section of the bash manual.

It explains which characters needs escaping. Note that some characters may need escaping depending on which options are enabled such as history expansion.

How to use store and use session variables across pages?

All you want to do is write --- session_start(); ----- on both pages..

<!-- first page -->
  $_SESSION['myvar'] = 'hello';

<!-- second page -->
    echo $_SESSION['myvar']; // it will print hello 


SEVERE: ContainerBase.addChild: start:org.apache.catalina.LifecycleException: Failed to start error

I had the same error statement following a "Failed to access resource" error message:


#cat callflow-java-logger-1.log.0


Dec 09, 2015 8:09:03 AM org.apache.catalina.loader.WebappLoader startInternal
SEVERE: LifecycleException Failed to access resource /WEB-INF/lib/ojdbc14.jar

In my case the solution was changing the connector permissions

-rw------- 1 owner creator size date ojdbc14.jar

This file in question wasn't initially located at /WEB-INF/lib, which was probably due to how BIRT works. It can be tricky if you are dealing with a higher number of files.


Try this:

select CONVERT(datetime, convert(varchar(10), 20120103))

Regex Until But Not Including

A lookahead regex syntax can help you to achieve your goal. Thus a regex for your example is


And it's important to notice the .*? lazy matching before the (?=z) lookahead: the expression matches a substring until a first occurrence of the z letter.

Here is C# code sample:

const string text = "The quick red fox jumped over the lazy brown dogz";

string lazy = new Regex(".*?quick.*?(?=z)").Match(text).Value;
Console.WriteLine(lazy); // The quick red fox jumped over the la

string greedy = new Regex(".*?quick.*(?=z)").Match(text).Value;
Console.WriteLine(greedy); // The quick red fox jumped over the lazy brown dog

Google Maps API: open url by clicking on marker

google.maps.event.addListener(marker, 'click', (function(marker, i) {
  return function() {
    window.location.href = marker.url;
})(marker, i));

"ssl module in Python is not available" when installing package with pip3

In the case of using pyenv to manage python installations on Mac OS Catalina, I had to install openssl with brew first and then after that run pyenv install 3.7.8 which seemed to build the python installation using the openssl from homebrew (it even said as such in the installation output). Then pyenv global 3.7.8 and I was away.

Twitter Bootstrap vs jQuery UI?

We have used both and we like Bootstrap for its simplicity and the pace at which it's being developed and enhanced. The problem with jQuery UI is that it's moving at a snail's pace. It's taking years to roll out common features like Menubar, Tree control and DataGrid which are in planning/development stage for ever. We waited waited waited and finally given up and used other libraries like ExtJS for our product

Bootstrap has come up with quite a comprehensive set of features in a very short period of time and I am sure it will outpace jQuery UI pretty soon.

So I see no point in using something that will eventually be outdated...

How to completely uninstall kubernetes

If you are clearing the cluster so that you can start again, then, in addition to what @rib47 said, I also do the following to ensure my systems are in a state ready for kubeadm init again:

kubeadm reset -f
rm -rf /etc/cni /etc/kubernetes /var/lib/dockershim /var/lib/etcd /var/lib/kubelet /var/run/kubernetes ~/.kube/*
iptables -F && iptables -X
iptables -t nat -F && iptables -t nat -X
iptables -t raw -F && iptables -t raw -X
iptables -t mangle -F && iptables -t mangle -X
systemctl restart docker

You then need to re-install, kubeadm, kubectl, and kubelet to make sure they are at the latest versions for your distribution before you re-initialize the cluster.

EDIT: Discovered that calico adds firewall rules to the raw table so that needs clearing out as well.

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

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

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

How to adjust layout when soft keyboard appears

Easy way in kotlin

In your fragment

requireActivity().window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE or WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN)

In your layout :


Django: Get list of model fields?

At least with Django 1.9.9 -- the version I'm currently using --, note that .get_fields() actually also "considers" any foreign model as a field, which may be problematic. Say you have:

class Parent(models.Model):
    id = UUIDField(primary_key=True)

class Child(models.Model):
    parent = models.ForeignKey(Parent)

It follows that

>>> map(lambda, Parent._model._meta.get_fields())
['id', 'child']

while, as shown by @Rockallite

>>> map(lambda, Parent._model._meta.local_fields)

How are ssl certificates verified?

The client has a pre-seeded store of SSL certificate authorities' public keys. There must be a chain of trust from the certificate for the server up through intermediate authorities up to one of the so-called "root" certificates in order for the server to be trusted.

You can examine and/or alter the list of trusted authorities. Often you do this to add a certificate for a local authority that you know you trust - like the company you work for or the school you attend or what not.

The pre-seeded list can vary depending on which client you use. The big SSL certificate vendors insure that their root certs are in all the major browsers ($$$).

Monkey-in-the-middle attacks are "impossible" unless the attacker has the private key of a trusted root certificate. Since the corresponding certificates are widely deployed, the exposure of such a private key would have serious implications for the security of eCommerce generally. Because of that, those private keys are very, very closely guarded.

ERROR: Error 1005: Can't create table (errno: 121)

Something I noticed was that I had "other_database" and "Other_Database" in my databases. That caused this problem as I actually had same reference in other database which caused this mysterious error!

Change the mouse pointer using JavaScript

With regards to @CrazyJugglerDrummer second method it would be: = "";

How to play video with AVPlayerViewController (AVKit) in Swift

Try this, definitely works for Swift 2.0

 let player = AVPlayer(URL: url)
    let playerController = AVPlayerViewController()

    playerController.player = player
    playerController.view.frame = self.view.frame  

How do you add multi-line text to a UIButton?

These days, if you really need this sort of thing to be accessible in interface builder on a case-by-case basis, you can do it with a simple extension like this:

extension UIButton {
    @IBInspectable var numberOfLines: Int {
        get { return titleLabel?.numberOfLines ?? 1 }
        set { titleLabel?.numberOfLines = newValue }

Then you can simply set numberOfLines as an attribute on any UIButton or UIButton subclass as if it were a label. The same goes for a whole host of other usually-inaccessible values, such as the corner radius of a view's layer, or the attributes of the shadow that it casts.

How do I calculate the MD5 checksum of a file in Python?

In regards to your error and what's missing in your code. m is a name which is not defined for getmd5() function.

No offence, I know you are a beginner, but your code is all over the place. Let's look at your issues one by one :)

First, you are not using hashlib.md5.hexdigest() method correctly. Please refer explanation on hashlib functions in Python Doc Library. The correct way to return MD5 for provided string is to do something like this:

>>> import hashlib
>>> hashlib.md5("filename.exe").hexdigest()

However, you have a bigger problem here. You are calculating MD5 on a file name string, where in reality MD5 is calculated based on file contents. You will need to basically read file contents and pipe it though MD5. My next example is not very efficient, but something like this:

>>> import hashlib
>>> hashlib.md5(open('filename.exe','rb').read()).hexdigest()

As you can clearly see second MD5 hash is totally different from the first one. The reason for that is that we are pushing contents of the file through, not just file name.

A simple solution could be something like that:

# Import hashlib library (md5 method is part of it)
import hashlib

# File to check
file_name = 'filename.exe'

# Correct original md5 goes here
original_md5 = '5d41402abc4b2a76b9719d911017c592'  

# Open,close, read file and calculate MD5 on its contents 
with open(file_name) as file_to_check:
    # read contents of the file
    data =    
    # pipe contents of the file through
    md5_returned = hashlib.md5(data).hexdigest()

# Finally compare original MD5 with freshly calculated
if original_md5 == md5_returned:
    print "MD5 verified."
    print "MD5 verification failed!."

Please look at the post Python: Generating a MD5 checksum of a file. It explains in detail a couple of ways how it can be achieved efficiently.

Best of luck.

How does the class_weight parameter in scikit-learn work?

The first answer is good for understanding how it works. But I wanted to understand how I should be using it in practice.


  • for moderately imbalanced data WITHOUT noise, there is not much of a difference in applying class weights
  • for moderately imbalanced data WITH noise and strongly imbalanced, it is better to apply class weights
  • param class_weight="balanced" works decent in the absence of you wanting to optimize manually
  • with class_weight="balanced" you capture more true events (higher TRUE recall) but also you are more likely to get false alerts (lower TRUE precision)
    • as a result, the total % TRUE might be higher than actual because of all the false positives
    • AUC might misguide you here if the false alarms are an issue
  • no need to change decision threshold to the imbalance %, even for strong imbalance, ok to keep 0.5 (or somewhere around that depending on what you need)


The result might differ when using RF or GBM. sklearn does not have class_weight="balanced" for GBM but lightgbm has LGBMClassifier(is_unbalance=False)


# scikit-learn==0.21.3
from sklearn import datasets
from sklearn.linear_model import LogisticRegression
from sklearn.metrics import roc_auc_score, classification_report
import numpy as np
import pandas as pd

# case: moderate imbalance
X, y = datasets.make_classification(n_samples=50*15, n_features=5, n_informative=2, n_redundant=0, random_state=1, weights=[0.8]) #,flip_y=0.1,class_sep=0.5)
np.mean(y) # 0.2

LogisticRegression(C=1e9).fit(X,y).predict(X).mean() # 0.184
(LogisticRegression(C=1e9).fit(X,y).predict_proba(X)[:,1]>0.5).mean() # 0.184 => same as first
LogisticRegression(C=1e9,class_weight={0:0.5,1:0.5}).fit(X,y).predict(X).mean() # 0.184 => same as first
LogisticRegression(C=1e9,class_weight={0:2,1:8}).fit(X,y).predict(X).mean() # 0.296 => seems to make things worse?
LogisticRegression(C=1e9,class_weight="balanced").fit(X,y).predict(X).mean() # 0.292 => seems to make things worse?

roc_auc_score(y,LogisticRegression(C=1e9).fit(X,y).predict(X)) # 0.83
roc_auc_score(y,LogisticRegression(C=1e9,class_weight={0:2,1:8}).fit(X,y).predict(X)) # 0.86 => about the same
roc_auc_score(y,LogisticRegression(C=1e9,class_weight="balanced").fit(X,y).predict(X)) # 0.86 => about the same

# case: strong imbalance
X, y = datasets.make_classification(n_samples=50*15, n_features=5, n_informative=2, n_redundant=0, random_state=1, weights=[0.95])
np.mean(y) # 0.06

LogisticRegression(C=1e9).fit(X,y).predict(X).mean() # 0.02
(LogisticRegression(C=1e9).fit(X,y).predict_proba(X)[:,1]>0.5).mean() # 0.02 => same as first
LogisticRegression(C=1e9,class_weight={0:0.5,1:0.5}).fit(X,y).predict(X).mean() # 0.02 => same as first
LogisticRegression(C=1e9,class_weight={0:1,1:20}).fit(X,y).predict(X).mean() # 0.25 => huh??
LogisticRegression(C=1e9,class_weight="balanced").fit(X,y).predict(X).mean() # 0.22 => huh??
(LogisticRegression(C=1e9,class_weight="balanced").fit(X,y).predict_proba(X)[:,1]>0.5).mean() # same as last

roc_auc_score(y,LogisticRegression(C=1e9).fit(X,y).predict(X)) # 0.64
roc_auc_score(y,LogisticRegression(C=1e9,class_weight={0:1,1:20}).fit(X,y).predict(X)) # 0.84 => much better
roc_auc_score(y,LogisticRegression(C=1e9,class_weight="balanced").fit(X,y).predict(X)) # 0.85 => similar to manual
roc_auc_score(y,(LogisticRegression(C=1e9,class_weight="balanced").fit(X,y).predict_proba(X)[:,1]>0.5).astype(int)) # same as last

pd.crosstab(y,LogisticRegression(C=1e9).fit(X,y).predict(X),margins=True,normalize='index') # few prediced TRUE with only 28% TRUE recall and 86% TRUE precision so 6%*28%~=2%

pd.crosstab(y,LogisticRegression(C=1e9,class_weight="balanced").fit(X,y).predict(X),margins=True,normalize='index') # 88% TRUE recall but also lot of false positives with only 23% TRUE precision, making total predicted % TRUE > actual % TRUE

jQuery .live() vs .on() method for adding a click event after loading dynamic html

I used 'live' in my project but one of my friend suggested that i should use 'on' instead of live. And when i tried to use that i experienced a problem like you had.

On my pages i create buttons table rows and many dom stuff dynamically. but when i use on the magic disappeared.

The other solutions like use it like a child just calls your functions every time on every click. But i find a way to make it happen again and here is the solution.

Write your code as:

function caller(){
    $('.ObjectYouWntToCall').on("click", function() {...magic...});

Call caller(); after you create your object in the page like this.

$('<dom class="ObjectYouWntToCall">bla... bla...<dom>').appendTo("#whereeveryouwant");

By this way your function is called when it is supposed to not every click on the page.

Extracting the top 5 maximum values in excel

To my mind the case for a PT (as @Nathan Fisher) is a 'no brainer', but I would add a column to facilitate ordering by rank (up or down):

SO18528624 first example

OPS is entered as VALUES (Sum of) twice so I have renamed the column labels to make clearer which is which. The PT is in a different sheet from the data but could be in the same sheet.

Rank is set with a right click on a data point selected in that column and Show Values As... and Rank Largest to Smallest (there are other options) with the Base field as Player and the filter is a Value Filters, Top 10... one:

SO18528624 second example

Once in a PT the power of that feature can very easily be applied to view the data in many other ways, with no change of formula (there isn't one!).

In the case of a tie for the last position included in the filter both results are included (Top 5 would show six or more results). A tie for top rank between just two players would show as 1 1 3 4 5 for Top 5.

AlertDialog.Builder with custom layout and EditText; cannot access view

editText is a part of alertDialog layout so Just access editText with reference of alertDialog

EditText editText = (EditText) alertDialog.findViewById(;


Because in code line dialogBuilder.setView(inflater.inflate(R.layout.alert_label_editor, null));

inflater is Null.

update your code like below, and try to understand the each code line

AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
// ...Irrelevant code for customizing the buttons and title
LayoutInflater inflater = this.getLayoutInflater();
View dialogView = inflater.inflate(R.layout.alert_label_editor, null);

EditText editText = (EditText) dialogView.findViewById(;
editText.setText("test label");
AlertDialog alertDialog = dialogBuilder.create();;

Update 2:

As you are using View object created by Inflater to update UI components else you can directly use setView(int layourResId) method of AlertDialog.Builder class, which is available from API 21 and onwards.

Drop all tables whose names begin with a certain string

In case of temporary tables, you might want to try

SELECT 'DROP TABLE "' + + '"' 
FROM tempdb.sys.tables t
WHERE LIKE '[prefix]%'

ERROR: Cannot open source file " "

One thing that caught me out and surprised me was, in an inherited project, the files it was referring to were referred to on a relative path outside of the project folder but yet existed in the project folder.

In solution explorer, single click each file with the error, bring up the Properties window (right-click, Properties), and ensure the "Relative Path" is just the file name (e.g. MyMissingFile.cpp) if it is in the project folder. In my case it was set to: ..\..\Some Other Folder\MyMissingFile.cpp.

Creating a div element in jQuery

I've just made a small jQuery plugin for that.

It follows your syntax:

var myDiv = $.create("div");

DOM node ID can be specified as second parameter:

var secondItem = $.create("div","item2");

Is it serious? No. But this syntax is better than $("<div></div>"), and it's a very good value for that money.

(Answer partially copied from: jQuery document.createElement equivalent?)

How to use setInterval and clearInterval?

Use setTimeout(drawAll, 20) instead. That only executes the function once.

default value for struct member in C

you can not do it in this way

Use the following instead

typedef struct
   int id;
   char* name;

employee emp = {
.id = 0, 
.name = "none"

You can use macro to define and initialize your instances. this will make easiier to you each time you want to define new instance and initialize it.

typedef struct
   int id;
   char* name;

#define INIT_EMPLOYEE(X) employee X = {.id = 0, .name ="none"}

and in your code when you need to define new instance with employee type, you just call this macro like:


.NET: Simplest way to send POST with data and read response

Given other answers are a few years old, currently here are my thoughts that may be helpful:

Simplest way

private async Task<string> PostAsync(Uri uri, HttpContent dataOut)
    var client = new HttpClient();
    var response = await client.PostAsync(uri, dataOut);
    return await response.Content.ReadAsStringAsync();
    // For non strings you can use other Content.ReadAs...() method variations

A More Practical Example

Often we are dealing with known types and JSON, so you can further extend this idea with any number of implementations, such as:

public async Task<T> PostJsonAsync<T>(Uri uri, object dtoOut)
    var content = new StringContent(JsonConvert.SerializeObject(dtoOut));
    content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");

    var results = await PostAsync(uri, content); // from previous block of code

    return JsonConvert.DeserializeObject<T>(results); // using Newtonsoft.Json

An example of how this could be called:

var dataToSendOutToApi = new MyDtoOut();
var uri = new Uri("");
var dataFromApi = await PostJsonAsync<MyDtoIn>(uri, dataToSendOutToApi);

Convert decimal to hexadecimal in UNIX shell script

Hexidecimal to decimal:

$ echo $((0xfee10000))

Decimal to hexadecimal:

$ printf '%x\n' 26

Check if an object belongs to a class in Java

Use the instanceof operator:

if(a instanceof MyClass)
    //do something

Correct Semantic tag for copyright info - html5

it is better to include it in a <small> tag The HTML <small> tag is used for specifying small print.

Small print (also referred to as "fine print" or "mouseprint") usually refers to the part of a document that contains disclaimers, caveats, or legal restrictions, such as copyrights. And this tag is supported in all major browsers.

 <small>&copy; Copyright 2058, Example Corporation</small>

Extract year from date

When you convert your variable to Date:

date <-  as.Date('10/30/2018','%m/%d/%Y')

you can then cut out the elements you want and make new variables, like year:

year <- as.numeric(format(date,'%Y'))

or month:

month <- as.numeric(format(date,'%m'))

How do I add slashes to a string in Javascript?

var myNewString = myOldString.replace(/'/g, "\\'");

How to change menu item text dynamically in Android

You can do it like this, and no need to dedicate variable:

Toolbar toolbar = findViewById(;
Menu menu = toolbar.getMenu();
MenuItem menuItem = menu.findItem(;
menuItem.setTitle("New title");

Or a little simplified:

MenuItem menuItem = ((Toolbar)findViewById(;
menuItem.setTitle("New title");

It works only - after the menu created.

Python pip install fails: invalid command egg_info

try the following command:

pip install setuptools==28.8.0

How do you do the "therefore" (?) symbol on a Mac or in Textmate?

If you are trying to insert the therefore symbol into a WORD DOCUMENT

Hold down the ALT key and type 8756

Hope the answer ur question Regards Al~Hash.

Replace HTML Table with Divs

Please be aware that although tables are discouraged as a primary means of page layout, they still have their place. Tables can and should be used when and where appropriate and until some of the more popular browsers (ahem, IE, ahem) become more standards compliant, tables are sometimes the best route to a solution.

Getting a 500 Internal Server Error on Laravel 5+ Ubuntu 14.04

First allow all permissions for your project folder (let say it's called laravel), for the storage subfolder and its logs subsubfolder and for the vendor subfolder (laravel/storage, laravel/storage/logs and laravel/vendor).

Then check if your have .env file - if not you can run:

$ mv .env.example .env

to rename your build-in .env.example to the needed .env.

Otherwise turn on the debug mode - open .env and set


and open laravel/config/app.php and change

'debug' => env('APP_DEBUG', false), 


'debug' => env('APP_DEBUG', true),

so you can find out what is the reason for your error.

Reading local text file into a JavaScript array

Using Node.js

sync mode:

var fs = require("fs");
var text = fs.readFileSync("./mytext.txt");
var textByLine = text.split("\n")

async mode:

var fs = require("fs");
fs.readFile("./mytext.txt", function(text){
    var textByLine = text.split("\n")


As of at least Node 6, readFileSync returns a Buffer, so it must first be converted to a string in order for split to work:

var text = fs.readFileSync("./mytext.txt").toString('utf-8');


var text = fs.readFileSync("./mytext.txt", "utf-8");

where is create-react-app webpack config and files?

The files are located in your node_modules/react-scripts folder:

Webpack config:

Start Script:

Build Script:

Test Script:

and so on ...

Now, the purpose of CRA is not to worry about these.

From the documentation:

You don’t need to install or configure tools like Webpack or Babel. They are preconfigured and hidden so that you can focus on the code.

If you want to have access to the config files, you need to eject by running:

npm run eject

Note: this is a one-way operation. Once you eject, you can’t go back!

In most scenarios, it is best not to eject and try to find a way to make it work for you in another way.

If you need to override some of the config options, you can have a look at

Converting a string to JSON object

Let's us consider you have string like

example : "name:lucy,age:21,gender:female"

function getJsonData(query){_x000D_
    let arrayOfKeyValues = query.split(',');_x000D_
    let modifiedArray =  new Array();_x000D_
    for(let i=0;i< arrayOfKeyValues.length;i++){_x000D_
        let arrayValues = arrayOfKeyValues[i].split(':');_x000D_
        let arrayString ='"'+arrayValues[0]+'"'+':'+'"'+arrayValues[1]+'"';_x000D_
    let jsonDataString = '{'+modifiedArray.toString()+'}';_x000D_
    let jsonData = JSON.parse(jsonDataString);_x000D_
    console.log(typeof jsonData);_x000D_
    return jsonData;_x000D_
let query = "name:lucy,age:21,gender:female";_x000D_
let response = getJsonData(query);_x000D_


How do I do redo (i.e. "undo undo") in Vim?

Practically speaking, the :undolist is hard to use and Vim’s :earlier and :later time tracking of changes is only usable for course-grain fixes.

Given that, I resort to a plug-in that combines these features to provide a visual tree of browsable undos, called “Gundo.”

Obviously, this is something to use only when you need a fine-grained fix, or you are uncertain of the exact state of the document you wish to return to. See: Gundo. Graph your Vim undo tree in style

Select Tag Helper in ASP.NET Core MVC

I created an Interface and a <options> tag helper for this. So I didn't have to convert the IEnumerable<T> items into IEnumerable<SelectListItem> every time I have to populate the <select> control.

And I think it works beautifully...

The usage is something like:

<select asp-for="EmployeeId">
    <option value="">Please select...</option>
    <options asp-items="@Model.EmployeesList" />

And to make it work with the tag helper you have to implement that interface in your class:

public class Employee : IIntegerListItem
   public int Id { get; set; }
   public string FullName { get; set; }

   public int Value { return Id; }
   public string Text{ return FullName ; }

These are the needed codes:

The interface:

public interface IIntegerListItem
    int Value { get; }
    string Text { get; }

The <options> tag helper:

[HtmlTargetElement("options", Attributes = "asp-items")]
public class OptionsTagHelper : TagHelper
    public OptionsTagHelper(IHtmlGenerator generator)
        Generator = generator;

    public IHtmlGenerator Generator { get; set; }

    public object Items { get; set; }

    public override void Process(TagHelperContext context, TagHelperOutput output)
        // Is this <options /> element a child of a <select/> element the SelectTagHelper targeted?
        object formDataEntry;
        context.Items.TryGetValue(typeof(SelectTagHelper), out formDataEntry);

        var selectedValues = formDataEntry as ICollection<string>;
        var encodedValues = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
        if (selectedValues != null && selectedValues.Count != 0)
            foreach (var selectedValue in selectedValues)

        IEnumerable<SelectListItem> items = null;
        if (Items != null)
            if (Items is IEnumerable)
                var enumerable = Items as IEnumerable;
                if (Items is IEnumerable<SelectListItem>)
                    items = Items as IEnumerable<SelectListItem>;
                else if (Items is IEnumerable<IIntegerListItem>)
                    items = ((IEnumerable<IIntegerListItem>)Items).Select(x => new SelectListItem() { Selected = false, Value = ((IIntegerListItem)x).Value.ToString(), Text = ((IIntegerListItem)x).Text });
                    throw new InvalidOperationException(string.Format("The {2} was unable to provide metadata about '{1}' expression value '{3}' for <options>.",
                throw new InvalidOperationException("Invalid items for <options>");

            foreach (var item in items)
                bool selected = (selectedValues != null && selectedValues.Contains(item.Value)) || encodedValues.Contains(item.Value);
                var selectedAttr = selected ? "selected='selected'" : "";

                if (item.Value != null)
                    output.Content.AppendHtml($"<option value='{item.Value}' {selectedAttr}>{item.Text}</option>");

There may be some typo but the aim is clear I think. I had to edit a little bit.

Why don't Java's +=, -=, *=, /= compound assignment operators require casting?

In Java type conversions are performed automatically when the type of the expression on the right hand side of an assignment operation can be safely promoted to the type of the variable on the left hand side of the assignment. Thus we can safely assign:

 byte -> short -> int -> long -> float -> double. 

The same will not work the other way round. For example we cannot automatically convert a long to an int because the first requires more storage than the second and consequently information may be lost. To force such a conversion we must carry out an explicit conversion.
Type - Conversion

for or while loop to do something n times

but on the other hand it creates a completely useless list of integers just to loop over them. Isn't it a waste of memory, especially as far as big numbers of iterations are concerned?

That is what xrange(n) is for. It avoids creating a list of numbers, and instead just provides an iterator object.

In Python 3, xrange() was renamed to range() - if you want a list, you have to specifically request it via list(range(n)).

Query-string encoding of a Javascript Object

A small amendment to the accepted solution by user187291:

serialize = function(obj) {
   var str = [];
   for(var p in obj){
       if (obj.hasOwnProperty(p)) {
           str.push(encodeURIComponent(p) + "=" + encodeURIComponent(obj[p]));
   return str.join("&");

Checking for hasOwnProperty on the object makes JSLint/JSHint happy, and it prevents accidentally serializing methods of the object or other stuff if the object is anything but a simple dictionary. See the paragraph on for statements in this page:

Delimiter must not be alphanumeric or backslash and preg_match

You must specify a delimiter for your expression. A delimiter is a special character used at the start and end of your expression to denote which part is the expression. This allows you to use modifiers and the interpreter to know which is an expression and which are modifiers. As the error message states, the delimiter cannot be a backslash because the backslash is the escape character.

$pattern = "/My name is '(.*)' and im fine/";

and below the same example but with the i modifier to match without being case sensitive.

$pattern = "/My name is '(.*)' and im fine/i";

As you can see, the i is outside of the slashes and therefore is interpreted as a modifier.

Also bear in mind that if you use a forward slash character (/) as a delimiter you must then escape further uses of / in the regular expression, if present.

How do you strip a character out of a column in SQL Server?

Take a look at the following function - REPLACE():

select replace(DataColumn, StringToReplace, NewStringValue)

//example to replace the s in test with the number 1
select replace('test', 's', '1')
//yields te1t

If you want to remove a string, simple use the replace function with an empty string as the third parameter like:

select replace(DataColumn, 'StringToRemove', '')

How to write a link like <a href="#id"> which link to the same page in PHP?

try this

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
        <a href="#name">click me</a>
        <div name="name" id="name">here</div>

"Could not find a part of the path" error message

There can be one of the two cause for this error:

  1. Path is not correct - but it is less likely as CreateDirectory should create any path unless path itself is not valid, read invalid characters
  2. Account through which your application is running don't have rights to create directory at path location, like if you are trying to create directory on shared drive with not enough privileges etc

Angular update object in object array

You can try this also to replace existing object

toDoTaskList = [
                {id:'abcd', name:'test'},
                {id:'abcdc', name:'test'},
                {id:'abcdtr', name:'test'}

newRecordToUpdate = {id:'abcdc', name:'xyz'};, i) => {
         if ( == newRecordToUpdate .id){
            this.toDoTaskList[i] = updatedVal;

Update Git branches from master

to update your branch from the master:

  git checkout master
  git pull
  git checkout your_branch
  git merge master

How to set Android camera orientation properly?

From the Javadocs for setDisplayOrientation(int) (Requires API level 9):

 public static void setCameraDisplayOrientation(Activity activity,
         int cameraId, android.hardware.Camera camera) {
     android.hardware.Camera.CameraInfo info =
             new android.hardware.Camera.CameraInfo();
     android.hardware.Camera.getCameraInfo(cameraId, info);
     int rotation = activity.getWindowManager().getDefaultDisplay()
     int degrees = 0;
     switch (rotation) {
         case Surface.ROTATION_0: degrees = 0; break;
         case Surface.ROTATION_90: degrees = 90; break;
         case Surface.ROTATION_180: degrees = 180; break;
         case Surface.ROTATION_270: degrees = 270; break;

     int result;
     if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
         result = (info.orientation + degrees) % 360;
         result = (360 - result) % 360;  // compensate the mirror
     } else {  // back-facing
         result = (info.orientation - degrees + 360) % 360;

How to compare two Dates without the time portion?

If you're using Java 8, you should use the java.time.* classes to compare dates - it's preferred to the various java.util.* classes


LocalDate date1 = LocalDate.of(2016, 2, 14);
LocalDate date2 = LocalDate.of(2015, 5, 23);

shorthand If Statements: C#

Use the ternary operator

direction == 1 ? dosomething () : dosomethingelse ();

What is the difference between a "function" and a "procedure"?

There's a term subroutine or subprogram which stands for a parameterized piece of code that can be called from different places.

Functions and procedures are implementations of those. Usually functions return values and procedures don't return anything.

Object of class stdClass could not be converted to string

You mentioned in another comment that you aren't expecting your get_userdata() function to return an stdClass object? If that is the case, you should mind this line in that function:

return $query->row();

Here, the CodeIgniter database object "$query" has its row() method called which returns an stdClass. Alternately, you could run row_array() which returns the same data in array form.

Anyway, I strongly suspect that this isn't the root cause of the problem. Can you give us some more details, perhaps? Play around with some things and let us know how it goes. We can't play with your code, so it's hard to say exactly what's going on.

Simplest way to restart service on a remote computer

I recommend the method given by doofledorfer.

If you really want to do it via a direct API call, then look at the OpenSCManager function. Below are sample functions to take a machine name and service, and stop or start them.

function ServiceStart(sMachine, sService : string) : boolean;  //start service, return TRUE if successful
var schm, schs : SC_Handle;
    ss         : TServiceStatus;
    psTemp     : PChar;
    dwChkP     : DWord;
  ss.dwCurrentState := 0;
  schm := OpenSCManager(PChar(sMachine),Nil,SC_MANAGER_CONNECT);  //connect to the service control manager

  if(schm > 0)then begin // if successful...
    schs := OpenService( schm,PChar(sService),SERVICE_START or SERVICE_QUERY_STATUS);    // open service handle, start and query status
    if(schs > 0)then begin     // if successful...
      psTemp := nil;
      if (StartService(schs,0,psTemp)) and (QueryServiceStatus(schs,ss)) then
        while(SERVICE_RUNNING <> ss.dwCurrentState)do begin
          dwChkP := ss.dwCheckPoint;  //dwCheckPoint contains a value incremented periodically to report progress of a long operation.  Store it.
          Sleep(ss.dwWaitHint);  //Sleep for recommended time before checking status again
          if(not QueryServiceStatus(schs,ss))then
            break;  //couldn't check status
          if(ss.dwCheckPoint < dwChkP)then
            Break;  //if QueryServiceStatus didn't work for some reason, avoid infinite loop
        end;  //while not running
    end;  //if able to get service handle
  end;  //if able to get svc mgr handle
  Result := SERVICE_RUNNING = ss.dwCurrentState;  //if we were able to start it, return true

function ServiceStop(sMachine, sService : string) : boolean;  //stop service, return TRUE if successful
var schm, schs : SC_Handle;
    ss         : TServiceStatus;
    dwChkP     : DWord;
  schm := OpenSCManager(PChar(sMachine),nil,SC_MANAGER_CONNECT);

  if(schm > 0)then begin
    schs := OpenService(schm,PChar(sService),SERVICE_STOP or SERVICE_QUERY_STATUS);
    if(schs > 0)then begin
      if (ControlService(schs,SERVICE_CONTROL_STOP,ss)) and (QueryServiceStatus(schs,ss)) then
        while(SERVICE_STOPPED <> ss.dwCurrentState) do begin
          dwChkP := ss.dwCheckPoint;
          if(not QueryServiceStatus(schs,ss))then

          if(ss.dwCheckPoint < dwChkP)then
        end;  //while
    end;  //if able to get svc handle
  end;  //if able to get svc mgr handle
  Result := SERVICE_STOPPED = ss.dwCurrentState;

Why am I suddenly getting a "Blocked loading mixed active content" issue in Firefox?

I had this same problem because I bought a CSS template and it grabbed a javascript an external javascript file through I went to that page in my browser and then changed it to https://whatever... using SSL and it worked, so in my HTML javascript tag I just changed the URL to use https instead of http and it worked.

How to force table cell <td> content to wrap?

Just add: word-break: break-word; to you table class.

How do I kill an Activity when the Back button is pressed?

Well, if you study the structure of how the application life-cycle works,here , then you'll come to know that onPause() is called when another activity gains focus, and onStop() is called when the activity is no longer visible.

From what I have learned yet, you can call finish() only from the activity which is active and/or has the focus. If you're calling finish() from the onPause() method that means you're calling it when the activity is no longer active. thus an exception is thrown.

When you're calling finish() from onStop() then the activity is being sent to background, thus will no longer be visible, then this exception.

When you press the back button, onStop() is called.

Most probably, Android will automatically do for you what you are currently wanting to do.

Microsoft Azure: How to create sub directory in a blob container

As @Egon mentioned above, there is no real folder management in BLOB storage.

You can achieve some features of a file system using '/' in the file name, but this has many limitations (for example, what happen if you need to rename a "folder"?).

As a general rule, I would keep my files as flat as possible in a container, and have my application manage whatever structure I want to expose to the end users (for example manage a nested folder structure in my database, have a record for each file, referencing the BLOB using container-name and file-name).

Windows batch: call more than one command in a FOR loop?

SilverSkin and Anders are both correct. You can use parentheses to execute multiple commands. However, you have to make sure that the commands themselves (and their parameters) do not contain parentheses. cmd greedily searches for the first closing parenthesis, instead of handling nested sets of parentheses gracefully. This may cause the rest of the command line to fail to parse, or it may cause some of the parentheses to get passed to the commands (e.g. DEL myfile.txt)).

A workaround for this is to split the body of the loop into a separate function. Note that you probably need to jump around the function body to avoid "falling through" into it.

FOR /r %%X IN (*.txt) DO CALL :loopbody %%X
REM Don't "fall through" to :loopbody.

DEL %1


While writing queries using inner joins the records will fetches from both tables if the condition satisfied on both tables, i.e. exact match of the common column in both tables.

While writing query using cross join the result is like cartesian product of the no of records in both tables. example if table1 contains 2 records and table2 contains 3 records then result of the query is 2*3 = 6 records.

So dont go for cross join until you need that.

Laravel stylesheets and javascript don't load for non-base routes

Vinsa almost had it right you should add

<base href="{{URL::asset('/')}}" target="_top">

and scripts should go in their regular path

<script src="js/jquery/jquery-1.11.1.min.js"></script>

the reason for this is because Images and other things with relative path like image source or ajax requests won't work correctly without the base path attached.

How can you float: right in React Native?

You can directly specify the item's alignment, for example:

textright: {    
  alignSelf: 'flex-end',  

Can you append strings to variables in PHP?

In PHP use .= to append strings, and not +=.

Why does this output 0? [...] Does PHP not like += with strings?

+= is an arithmetic operator to add a number to another number. Using that operator with strings leads to an automatic type conversion. In the OP's case the strings have been converted to integers of the value 0.

More about operators in PHP:

Converting a float to a string without rounding it

I know this is too late but for those who are coming here for the first time, I'd like to post a solution. I have a float value index and a string imgfile and I had the same problem as you. This is how I fixed the issue

index = 1.0
imgfile = 'data/2.jpg'
out = '%.1f,%s' % (index,imgfile)
print out

The output is


You may modify this formatting example as per your convenience.

At runtime, find all classes in a Java application that extend a base class

One way is to make the classes use a static initializers... I don't think these are inherited (it won't work if they are):

public class Dog extends Animal{

   Animal a = new Dog();
   //add a to the List

It requires you to add this code to all of the classes involved. But it avoids having a big ugly loop somewhere, testing every class searching for children of Animal.

Disable html5 video autoplay

Remove ALL attributes that say autoplay as its presence in your tag is a boolean shorthand for true.

Also, make sure you always use video or audio elements. Do not use object or embed as those elements autoplay using 3rd part plugins by default and cannot be stopped without changing settings in the browser.

How do I get current scope dom-element in AngularJS controller?

The better and correct solution is to have a directive. The scope is the same, whether in the controller of the directive or the main controller. Use $element to do DOM operations. The method defined in the directive controller is accessible in the main controller.

Example, finding a child element:

var app = angular.module('myapp', []);
app.directive("testDir", function () {
    function link(scope, element) { 

    return {
        restrict: "AE", 
        link: link, 
            $scope.name2 = 'this is second name';
            var barGridSection = $element.find('#barGridSection'); //helps to find the child element.

app.controller('mainController', function ($scope) {
$'this is first name'

Make XAMPP / Apache serve file outside of htdocs folder

You can set Apache to serve pages from anywhere with any restrictions but it's normally distributed in a more secure form.

Editing your apache files (http.conf is one of the more common names) will allow you to set any folder so it appears in your webroot.


alias myapp c:\myapp\

I've edited my answer to include the format for creating an alias in the http.conf file which is sort of like a shortcut in windows or a symlink under un*x where Apache 'pretends' a folder is in the webroot. This is probably going to be more useful to you in the long term.

How to call a function from a string stored in a variable?

One unconventional approach, that came to my mind is, unless you are generating the whole code through some super ultra autonomous AI which writes itself, there are high chances that the functions which you want to "dynamically" call, are already defined in your code base. So why not just check for the string and do the infamous ifelse dance to summon the get my point.


if($functionName == 'foo'){
} else if($functionName == 'bar'){

Even switch-case can be used if you don't like the bland taste of ifelse ladder.

I understand that there are cases where the "dynamically calling the function" would be an absolute necessity (Like some recursive logic which modifies itself). But most of the everyday trivial use-cases can just be dodged.

It weeds out a lot of uncertainty from your application, while giving you a chance to execute a fallback function if the string doesn't match any of the available functions' definition. IMHO.

How can I export a GridView.DataSource to a datatable or dataset?


I was having the same issue as you, and this is the code I used to figure it out. Although, I don't use the footer row section for my purposes, I did include it in this code.

    DataTable dt = new DataTable();

    // add the columns to the datatable            
    if (GridView1.HeaderRow != null)

        for (int i = 0; i < GridView1.HeaderRow.Cells.Count; i++)

    //  add each of the data rows to the table
    foreach (GridViewRow row in GridView1.Rows)
        DataRow dr;
        dr = dt.NewRow();

        for (int i = 0; i < row.Cells.Count; i++)
            dr[i] = row.Cells[i].Text.Replace("&nbsp;","");

    //  add the footer row to the table
    if (GridView1.FooterRow != null)
        DataRow dr;
        dr = dt.NewRow();

        for (int i = 0; i < GridView1.FooterRow.Cells.Count; i++)
            dr[i] = GridView1.FooterRow.Cells[i].Text.Replace("&nbsp;","");

What is SELF JOIN and when would you use it?

A self join is simply when you join a table with itself. There is no SELF JOIN keyword, you just write an ordinary join where both tables involved in the join are the same table. One thing to notice is that when you are self joining it is necessary to use an alias for the table otherwise the table name would be ambiguous.

It is useful when you want to correlate pairs of rows from the same table, for example a parent - child relationship. The following query returns the names of all immediate subcategories of the category 'Kitchen'.

FROM category T1
JOIN category T2
ON T2.parent =
WHERE = 'Kitchen'

mysql server port number

If your MySQL server runs on default settings, you don't need to specify that.

Default MySQL port is 3306.

[updated to show mysql_error() usage]

$conn = mysql_connect($dbhost, $dbuser, $dbpass)
    or die('Error connecting to mysql: '.mysql_error());

Laravel 5 Carbon format datetime

Just use the date() and strtotime() function and save your time

$suborder['payment_date'] = date('d-m-Y', strtotime($item['created_at']));

Don't stress!!!

Substring in VBA



How to customize message box

You can't restyle the default MessageBox as that's dependant on the current Windows OS theme, however you can easily create your own MessageBox. Just add a new form (i.e. MyNewMessageBox) to your project with these settings:

FormBorderStyle    FixedToolWindow
ShowInTaskBar      False
StartPosition      CenterScreen

To show it use myNewMessageBoxInstance.ShowDialog();. And add a label and buttons to your form, such as OK and Cancel and set their DialogResults appropriately, i.e. add a button to MyNewMessageBox and call it btnOK. Set the DialogResult property in the property window to DialogResult.OK. When that button is pressed it would return the OK result:

MyNewMessageBox myNewMessageBoxInstance = new MyNewMessageBox();
DialogResult result = myNewMessageBoxInstance.ShowDialog();
if (result == DialogResult.OK)
    // etc

It would be advisable to add your own Show method that takes the text and other options you require:

public DialogResult Show(string text, Color foreColour)
     lblText.Text = text;
     lblText.ForeColor = foreColour;
     return this.ShowDialog();

MySQL IF ELSEIF in select query

As per Nawfal's answer, IF statements need to be in a procedure. I found this post that shows a brilliant example of using your script in a procedure while still developing and testing. Basically, you create, call then drop the procedure:

Android Studio does not show layout preview

This problem occurs due to theme compatibility issue. All you have to do is first navigate to res/values/styles.xml in the project view.There look for base application theme which by default should be the fourth line. It'd look similar to the following:

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

Now, you just have to add 'Base. to the parent.

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

jQuery autocomplete with callback ajax json

I used the construction of $.each (data [i], function (key, value) But you must pre-match the names of the selection fields with the names of the form elements. Then, in the loop after "success", autocomplete elements from the "data" array. Did this: autocomplete form with ajax success

Can HTTP POST be limitless?

Quite amazing how all answers talk about IIS, as if that were the only web server that mattered. Even back in 2010 when the question was asked, Apache had between 60% and 70% of the market share. Anyway,

  • The HTTP protocol does not specify a limit.
  • The POST method allows sending far more data than the GET method, which is limited by the URL length - about 2KB.
  • The maximum POST request body size is configured on the HTTP server and typically ranges from
    1MB to 2GB
  • The HTTP client (browser or other user agent) can have its own limitations. Therefore, the maximum POST body request size is min(serverMaximumSize, clientMaximumSize).

Here are the POST body sizes for some of the more popular HTTP servers:

CodeIgniter: Create new helper?

A CodeIgniter helper is a PHP file with multiple functions. It is not a class

Create a file and put the following code into it.

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

if ( ! function_exists('test_method'))
    function test_method($var = '')
        return $var;

Save this to application/helpers/ . We shall call it "new_helper.php"

The first line exists to make sure the file cannot be included and ran from outside the CodeIgniter scope. Everything after this is self explanatory.

Using the Helper

This can be in your controller, model or view (not preferable)


echo test_method('Hello World');

If you use this helper in a lot of locations you can have it load automatically by adding it to the autoload configuration file i.e. <your-web-app>\application\config\autoload.php.

$autoload['helper'] = array('new_helper');


How to display a jpg file in Python?

Don't forget to include

import Image

In order to show it use this :'pathToFile').show()

What is a faster alternative to Python's http.server (or SimpleHTTPServer)?

If you have PHP installed you could use the builtin server.

php -S 0:8080

C++ String Declaring

In C++ you can declare a string like this:

#include <string>

using namespace std;

int main()
    string str1("argue2000"); //define a string and Initialize str1 with "argue2000"    
    string str2 = "argue2000"; // define a string and assign str2 with "argue2000"
    string str3;  //just declare a string, it has no value
    return 1;

How to View Oracle Stored Procedure using SQLPlus?

check your casing, the name is typically stored in upper case


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

There is no sure shot trick. You need to explore the reasons why your mails are classified as spam. SpamAssassin hase a page describing Some Tips for Legitimate Senders to Avoid False Positives. See also Coding Horror: So You'd Like to Send Some Email (Through Code)

Laravel 5 Class 'form' not found

Begin by installing this package through Composer. Run the following from the terminal:

composer require "laravelcollective/html":"^5.3.0"

Next, add your new provider to the providers array of config/app.php:

'providers' => [
    // ...
    // ...

Finally, add two class aliases to the aliases array of config/app.php:

'aliases' => [
    // ...
      'Form' => Collective\Html\FormFacade::class,
      'Html' => Collective\Html\HtmlFacade::class,
    // ...


HTML5 pattern for formatting input box to take date mm/dd/yyyy?

Try to use:


"Data too long for column" - why?

I try to create a table with a field as 200 characters and I've added two rows with early 160 characters and it's OK. Are you sure your rows are less than 200 characters?

Show SqlFiddle

Resolving LNK4098: defaultlib 'MSVCRT' conflicts with

Right-click the project, select Properties then under 'Configuration properties | Linker | Input | Ignore specific Library and write msvcrtd.lib

Python: List vs Dict for look up table

As a new set of tests to show @EriF89 is still right after all these years:

$ python -m timeit -s "l={k:k for k in xrange(5000)}"    "[i for i in xrange(10000) if i in l]"
1000 loops, best of 3: 1.84 msec per loop
$ python -m timeit -s "l=[k for k in xrange(5000)]"    "[i for i in xrange(10000) if i in l]"
10 loops, best of 3: 573 msec per loop
$ python -m timeit -s "l=tuple([k for k in xrange(5000)])"    "[i for i in xrange(10000) if i in l]"
10 loops, best of 3: 587 msec per loop
$ python -m timeit -s "l=set([k for k in xrange(5000)])"    "[i for i in xrange(10000) if i in l]"
1000 loops, best of 3: 1.88 msec per loop

Here we also compare a tuple, which are known to be faster than lists (and use less memory) in some use cases. In the case of lookup table, the tuple faired no better .

Both the dict and set performed very well. This brings up an interesting point tying into @SilentGhost answer about uniqueness: if the OP has 10M values in a data set, and it's unknown if there are duplicates in them, then it would be worth keeping a set/dict of its elements in parallel with the actual data set, and testing for existence in that set/dict. It's possible the 10M data points only have 10 unique values, which is a much smaller space to search!

SilentGhost's mistake about dicts is actually illuminating because one could use a dict to correlate duplicated data (in values) into a nonduplicated set (keys), and thus keep one data object to hold all data, yet still be fast as a lookup table. For example, a dict key could be the value being looked up, and the value could be a list of indices in an imaginary list where that value occurred.

For example, if the source data list to be searched was l=[1,2,3,1,2,1,4], it could be optimized for both searching and memory by replacing it with this dict:

>>> from collections import defaultdict
>>> d = defaultdict(list)
>>> l=[1,2,3,1,2,1,4]
>>> for i, e in enumerate(l):
...     d[e].append(i)
>>> d
defaultdict(<class 'list'>, {1: [0, 3, 5], 2: [1, 4], 3: [2], 4: [6]})

With this dict, one can know:

  1. If a value was in the original dataset (ie 2 in d returns True)
  2. Where the value was in the original dataset (ie d[2] returns list of indices where data was found in original data list: [1, 4])

disable editing default value of text input

Probably due to the fact that I could not explain well you do not really understand my question. In general, I found the solution.

Sorry for my english

Attaching click event to a JQuery object not yet added to the DOM

Does using .live work for you?

$("#my-button").live("click", function(){ alert("yay!"); });


As of jQuery 1.7, the .live() method is deprecated. Use .on() to attach event handlers. Users of older versions of jQuery should use .delegate() in preference to .live().

Iterate a certain number of times without storing the iteration number anywhere

Although I agree completely with delnan's answer, it's not impossible:

loop = range(NUM_ITERATIONS+1)
while loop.pop():

Note, however, that this will not work for an arbitrary list: If the first value in the list (the last one popped) does not evaluate to False, you will get another iteration and an exception on the next pass: IndexError: pop from empty list. Also, your list (loop) will be empty after the loop.

Just for curiosity's sake. ;)

Getting year in moment.js

The year() function just retrieves the year component of the underlying Date object, so it returns a number.

Calling format('YYYY') will invoke moment's string formatting functions, which will parse the format string supplied, and build a new string containing the appropriate data. Since you only are passing YYYY, then the result will be a string containing the year.

If all you need is the year, then use the year() function. It will be faster, as there is less work to do.

Do note that while years are the same in this regard, months are not! Calling format('M') will return months in the range 1-12. Calling month() will return months in the range 0-11. This is due to the same behavior of the underlying Date object.

How to use jquery $.post() method to submit form values

Yor $.post has no data. You need to pass the form data. You can use serialize() to post the form data. Try this

    $.post("process.php", $('#reg-form').serialize() ,function(data){

Powershell's Get-date: How to get Yesterday at 22:00 in a variable?

I saw in at least one other place that people don't realize Date-Time takes in times as well, so I figured I'd share it here since it's really short to do so:

Get-Date # Following the OP's example, let's say it's Friday, March 12, 2010 9:00:00 AM
(Get-Date '22:00').AddDays(-1) # Thursday, March 11, 2010 10:00:00 PM

It's also the shortest way to strip time information and still use other parameters of Get-Date. For instance you can get seconds since 1970 this way (Unix timestamp):

Get-Date '0:00' -u '%s' # 1268352000

Or you can get an ISO 8601 timestamp:

Get-Date '0:00' -f 's' # 2010-03-12T00:00:00

Then again if you reverse the operands, it gives you a little more freedom with formatting with any date object:

'The sortable timestamp: {0:s}Z{1}Vs measly human format: {0:D}' -f (Get-Date '0:00'), "`r`n"
# The sortable timestamp: 2010-03-12T00:00:00Z
# Vs measly human format: Friday, March 12, 2010

However if you wanted to both format a Unix timestamp (via -u aka -UFormat), you'll need to do it separately. Here's an example of that:

'ISO 8601: {0:s}Z{1}Unix: {2}' -f (Get-Date '0:00'), "`r`n", (Get-Date '0:00' -u '%s')
# ISO 8601: 2010-03-12T00:00:00Z
# Unix: 1268352000

Hope this helps!

Date Conversion from String to sql Date in Java giving different output?

mm is minutes. You want MM for months:

SimpleDateFormat sdf1 = new SimpleDateFormat("dd-MM-yyyy");

Don't feel bad - this exact mistake comes up a lot.

Change image onmouseover

You can do that just using CSS.

You'll need to place another tag inside the <a> and then you can change the CSS background-image attribute on a:hover.



<a href="#" id="name">


a#name span{

a#name:hover span{

Python "TypeError: unhashable type: 'slice'" for encoding categorical data

X is a dataframe and can't be accessed via slice terminology like X[:, 3]. You must access via iloc or X.values. However, the way you constructed X made it a copy... so. I'd use values

# Importing the libraries
import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

# Importing the dataset
# dataset = pd.read_csv('50_Startups.csv')

dataset = pd.DataFrame(np.random.rand(10, 10))
y=dataset.iloc[:, 4]
X=dataset.iloc[:, 0:4]

# Encoding categorical data
from sklearn.preprocessing import LabelEncoder, OneHotEncoder
labelencoder_X = LabelEncoder()

#  I changed this line
X.values[:, 3] = labelencoder_X.fit_transform(X.values[:, 3])

Oracle SQL convert date format from DD-Mon-YY to YYYYMM

As offer_date is an number, and is of lower accuracy than your real dates, this may work...
- Convert your real date to a string of format YYYYMM
- Conver that value to an INT
- Compare the result you your offer_date

    offer_date = (SELECT CAST(to_char(create_date, 'YYYYMM') AS INT) FROM customers where id = '12345678')
AND offer_rate > 0 

Also, by doing all the manipulation on the create_date you only do the processing on one value.

Additionally, had you manipulated the offer_date you would not be able to utilise any index on that field, and so force SCANs instead of SEEKs.

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

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

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

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

entitymanager.packagesToScan: com

How to filter rows in pandas by regex

Multiple column search with dataframe:

frame[frame.filename.str.match('*.'+MetaData+'.*') & frame.file_path.str.match('C:\test\test.txt')]

Sorting a tab delimited file

By default the field delimiter is non-blank to blank transition so tab should work just fine.

However, the columns are indexed base 1 and base 0 so you probably want

sort -k4nr file.txt

to sort file.txt by column 4 numerically in reverse order. (Though the data in the question has even 5 fields so the last field would be index 5.)

Split bash string by newline characters

There is another way if all you want is the text up to the first line feed:



After that y will contain some and nothing else (no line feed).

What is happening here?

We perform a parameter expansion substring removal (${PARAMETER%PATTERN}) for the shortest match up to the first ANSI C line feed ($'\n') and drop everything that follows (*).

Convert DateTime in C# to yyyy-MM-dd format and Store it to MySql DateTime Field

We can use the below its very simple.


How do you use window.postMessage across domains?

You should post a message from frame to parent, after loaded.

frame script:

$(document).ready(function() {
    window.parent.postMessage("I'm loaded", "*");

And listen it in parent:

function listenMessage(msg) {

if (window.addEventListener) {
    window.addEventListener("message", listenMessage, false);
} else {
    window.attachEvent("onmessage", listenMessage);

Use this link for more info:

What are good grep tools for Windows?

Update July 2013:

Another grep tool I now use all the time on Windows is AstroGrep:

AstroGrep awesomeness

Its ability to show me more than just the line search (i.e. the --context=NUM of a command-line grep) is invaluable.
And it is fast. Very fast, even on an old computer with non-SSD drive (I know, they used to do this hard drive with spinning disks, called platters, crazy right?)

It is free.
It is portable (simple zip archive to unzip).

Original answer October 2008

alt textGnu Grep is alright

You can download it for example here: (site ftp)

All the usual options are here.

That, combined with gawk and xargs (includes 'find', from GnuWin32), and you can really script like you were on Unix!

See also the options I am using to grep recursively:

grep --include "*.xxx" -nRHI "my Text to grep" *

How do I get a human-readable file size in bytes abbreviation using .NET?

One more approach, for what it's worth. I liked @humbads optimized solution referenced above, so have copied the principle, but I've implemented it a little differently.

I suppose it's debatable as to whether it should be an extension method (since not all longs are necessarily byte sizes), but I like them, and it's somewhere I can find the method when I next need it!

Regarding the units, I don't think I've ever said 'Kibibyte' or 'Mebibyte' in my life, and while I'm skeptical of such enforced rather than evolved standards, I suppose it'll avoid confusion in the long term.

public static class LongExtensions
    private static readonly long[] numberOfBytesInUnit;
    private static readonly Func<long, string>[] bytesToUnitConverters;

    static LongExtensions()
        numberOfBytesInUnit = new long[6]    
            1L << 10,    // Bytes in a Kibibyte
            1L << 20,    // Bytes in a Mebibyte
            1L << 30,    // Bytes in a Gibibyte
            1L << 40,    // Bytes in a Tebibyte
            1L << 50,    // Bytes in a Pebibyte
            1L << 60     // Bytes in a Exbibyte

        // Shift the long (integer) down to 1024 times its number of units, convert to a double (real number), 
        // then divide to get the final number of units (units will be in the range 1 to 1023.999)
        Func<long, int, string> FormatAsProportionOfUnit = (bytes, shift) => (((double)(bytes >> shift)) / 1024).ToString("0.###");

        bytesToUnitConverters = new Func<long,string>[7]
            bytes => bytes.ToString() + " B",
            bytes => FormatAsProportionOfUnit(bytes, 0) + " KiB",
            bytes => FormatAsProportionOfUnit(bytes, 10) + " MiB",
            bytes => FormatAsProportionOfUnit(bytes, 20) + " GiB",
            bytes => FormatAsProportionOfUnit(bytes, 30) + " TiB",
            bytes => FormatAsProportionOfUnit(bytes, 40) + " PiB",
            bytes => FormatAsProportionOfUnit(bytes, 50) + " EiB",

    public static string ToReadableByteSizeString(this long bytes)
        if (bytes < 0)
            return "-" + Math.Abs(bytes).ToReadableByteSizeString();

        int counter = 0;
        while (counter < numberOfBytesInUnit.Length)
            if (bytes < numberOfBytesInUnit[counter])
                return bytesToUnitConverters[counter](bytes);
        return bytesToUnitConverters[counter](bytes);

Interface naming in Java

There is also another convention, used by many open source projects including Spring.

interface User {

class DefaultUser implements User {

class AnotherClassOfUser implements User {

I personally do not like the "I" prefix for the simple reason that its an optional convention. So if I adopt this does IIOPConnection mean an interface for IOPConnection? What if the class does not have the "I" prefix, do I then know its not an interface..the answer here is no, because conventions are not always followed, and policing them will create more work that the convention itself saves.

jquery multiple checkboxes array

var checked = []
$("input[name='options[]']:checked").each(function ()

Get index of a key/value pair in a C# dictionary based on the value

You can use LINQ to help you with this.

Dictionary<int, string> dict = new Dictionary<int, string>();
dict.Add(1, "hi");
dict.Add(2, "NotHi");
dict.Add(3, "Bah");

var item = (from d in dict
            where d.Value == "hi"
            select d.Key).FirstOrDefault();

Console.WriteLine(item); //Prints 1

How to run .sh on Windows Command Prompt?

New feature in Windows - run bash on ubuntu on windows - available in Windows 10 "Insiders" builds after the Build conference:

How do I discover memory usage of my application in Android?

This is a work in progress, but this is what I don't understand:

ActivityManager activityManager = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);
MemoryInfo memoryInfo = new ActivityManager.MemoryInfo();

Log.i(TAG, " memoryInfo.availMem " + memoryInfo.availMem + "\n" );
Log.i(TAG, " memoryInfo.lowMemory " + memoryInfo.lowMemory + "\n" );
Log.i(TAG, " memoryInfo.threshold " + memoryInfo.threshold + "\n" );

List<RunningAppProcessInfo> runningAppProcesses = activityManager.getRunningAppProcesses();

Map<Integer, String> pidMap = new TreeMap<Integer, String>();
for (RunningAppProcessInfo runningAppProcessInfo : runningAppProcesses)
    pidMap.put(, runningAppProcessInfo.processName);

Collection<Integer> keys = pidMap.keySet();

for(int key : keys)
    int pids[] = new int[1];
    pids[0] = key;
    android.os.Debug.MemoryInfo[] memoryInfoArray = activityManager.getProcessMemoryInfo(pids);
    for(android.os.Debug.MemoryInfo pidMemoryInfo: memoryInfoArray)
        Log.i(TAG, String.format("** MEMINFO in pid %d [%s] **\n",pids[0],pidMap.get(pids[0])));
        Log.i(TAG, " pidMemoryInfo.getTotalPrivateDirty(): " + pidMemoryInfo.getTotalPrivateDirty() + "\n");
        Log.i(TAG, " pidMemoryInfo.getTotalPss(): " + pidMemoryInfo.getTotalPss() + "\n");
        Log.i(TAG, " pidMemoryInfo.getTotalSharedDirty(): " + pidMemoryInfo.getTotalSharedDirty() + "\n");

Why isn't the PID mapped to the result in activityManager.getProcessMemoryInfo()? Clearly you want to make the resulting data meaningful, so why has Google made it so difficult to correlate the results? The current system doesn't even work well if I want to process the entire memory usage since the returned result is an array of android.os.Debug.MemoryInfo objects, but none of those objects actually tell you what pids they are associated with. If you simply pass in an array of all pids, you will have no way to understand the results. As I understand it's use, it makes it meaningless to pass in more than one pid at a time, and then if that's the case, why make it so that activityManager.getProcessMemoryInfo() only takes an int array?

Send mail via CMD console

Scenario: Your domain: Domain you wish to send to:

1. Determine the mail server you're sending to. Open a CMD prompt Type

 set q=mx


Non-authoritative answer: MX preference = 50, mail exchanger = 

EDIT Be sure to type exit to terminate NSLOOKUP.

2. Connect to their mail server

SMTP communicates over port 25. We will now try to use TELNET to connect to their mail server ""

Open a CMD prompt


You should see something like this as a response:

220 ESMTP 6si6253627yxg.6

Be aware that different servers will come up with different greetings but you should get SOMETHING. If nothing comes up at this point there are 2 possible problems. Port 25 is being blocked at your firewall, or their server is not responding. Try a different domain, if that works then it's not you.

3. Send an Email

Now, use simple SMTP commands to send a test email. This is very important, you CANNOT use the backspace key, it will work onscreen but not be interpreted correctly. You have to type these commands perfectly.

mail from:<[email protected]> 
rcpt to:<[email protected]> 
This is a test, please do not respond

So, what does that all mean? EHLO - introduce yourself to the mail server HELO can also be used but EHLO tells the server to use the extended command set (not that we're using that).

MAIL FROM - who's sending the email. Make sure to place this is the greater than/less than brackets as many email servers will require this (Postini).

RCPT TO - who you're sending it to. Again you need to use the brackets. See Step #4 on how to test relaying mail!

DATA - tells the SMTP server that what follows is the body of your email. Make sure to hit "Enter" at the end.

. - the period alone on the line tells the SMTP server you're all done with the data portion and it's clear to send the email.

quit - exits the TELNET session.

4. Test SMTP relay Testing SMTP relay is very easy, and simply requires a small change to the above commands. See below:

mail from:<[email protected]> 
rcpt to:<[email protected]> 
This is a test, please do not respond 

See the difference? On the RCPT TO line, we're sending to a domain that is not controlled by the SMTP server we're sending to. You will get an immediate error is SMTP relay is turned off. If you're able to continue and send an email, then relay is allowed by that server.

How can I load webpage content into a div on page load?

This is possible to do without an iframe specifically. jQuery is utilised since it's mentioned in the title.

<!doctype html>
    <meta charset="utf-8">
    <title>Load remote content into object element</title>
    <div id="siteloader"></div>?
    <script src=""></script>
      $("#siteloader").html('<object data="">');

Installing SetupTools on 64-bit Windows

Yes, you are correct, the issue is with 64-bit Python and 32-bit installer for setuptools.

The best way to get 64-bit setuptools installed on Windows is to download to C:\Python27\Scripts and run it. It will download appropriate 64-bit .egg file for setuptools and install it for you.


P.S. I'd recommend against using 3rd party 64-bit .exe setuptools installers or manipulating registry

how to pass parameters to query in SQL (Excel)

It depends on the database to which you're trying to connect, the method by which you created the connection, and the version of Excel that you're using. (Also, most probably, the version of the relevant ODBC driver on your computer.)

The following examples are using SQL Server 2008 and Excel 2007, both on my local machine.

When I used the Data Connection Wizard (on the Data tab of the ribbon, in the Get External Data section, under From Other Sources), I saw the same thing that you did: the Parameters button was disabled, and adding a parameter to the query, something like select field from table where field2 = ?, caused Excel to complain that the value for the parameter had not been specified, and the changes were not saved.

When I used Microsoft Query (same place as the Data Connection Wizard), I was able to create parameters, specify a display name for them, and enter values each time the query was run. Bringing up the Connection Properties for that connection, the Parameters... button is enabled, and the parameters can be modified and used as I think you want.

I was also able to do this with an Access database. It seems reasonable that Microsoft Query could be used to create parameterized queries hitting other types of databases, but I can't easily test that right now.

Android Studio was unable to find a valid Jvm (Related to MAC OS)

On Mac OS X Yosemite just install:

Java SE Development Kit 8


Java Version 8 Update 25

It's all, work for me too! like gehev said , so simple !

Display all items in array using jquery

Original from Sept. 13, 2015:
Quick and easy.

$.each(yourArray, function(index, value){
    $('.element').html( $('.element').html() + '<span>' + value +'</span>')

Update Sept 9, 2019: No jQuery is needed to iterate the array.

yourArray.forEach((value) => {

/* --- Or without jQuery at all --- */

yourArray.forEach((value) => {
    document.querySelector(".element").innerHTML += `<span>${value}</span>`;

Get IP address of an interface on Linux

My 2 cents: the same code works even if iOS:

#include <arpa/inet.h>
#include <sys/socket.h>
#include <netdb.h>
#include <ifaddrs.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#import "ViewController.h"

@interface ViewController ()


@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

void showIP()
    struct ifaddrs *ifaddr, *ifa;
    int family, s;
    char host[NI_MAXHOST];

    if (getifaddrs(&ifaddr) == -1)

    for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next)
        if (ifa->ifa_addr == NULL)

        s=getnameinfo(ifa->ifa_addr,sizeof(struct sockaddr_in),host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);

        if( /*(strcmp(ifa->ifa_name,"wlan0")==0)&&( */ ifa->ifa_addr->sa_family==AF_INET) // )
            if (s != 0)
                printf("getnameinfo() failed: %s\n", gai_strerror(s));
            printf("\tInterface : <%s>\n",ifa->ifa_name );
            printf("\t  Address : <%s>\n", host);



I simply removed the test against wlan0 to see data. ps You can remove "family"

CodeIgniter 500 Internal Server Error

This probably isn't relevant any more to this thread, but hopefully helpful to somebody. I've had 500 errors for the past hour as I had a controller return an array not supported by the php version ran on my (crappy) server. Seems trivial but had the hallmarks of a codeigniter error.

I had to use:

class emck_model extends CI_Model {

    public function getTiles(){

        return array(...);



Instead of

class emck_model extends CI_Model {

    public function getTiles(){

        return [...];




Is iterating ConcurrentHashMap values thread safe?

What does it mean?

That means that each iterator you obtain from a ConcurrentHashMap is designed to be used by a single thread and should not be passed around. This includes the syntactic sugar that the for-each loop provides.

What happens if I try to iterate the map with two threads at the same time?

It will work as expected if each of the threads uses it's own iterator.

What happens if I put or remove a value from the map while iterating it?

It is guaranteed that things will not break if you do this (that's part of what the "concurrent" in ConcurrentHashMap means). However, there is no guarantee that one thread will see the changes to the map that the other thread performs (without obtaining a new iterator from the map). The iterator is guaranteed to reflect the state of the map at the time of it's creation. Futher changes may be reflected in the iterator, but they do not have to be.

In conclusion, a statement like

for (Object o : someConcurrentHashMap.entrySet()) {
    // ...

will be fine (or at least safe) almost every time you see it.

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'MyController':

Change from @Controller to @Service to CompteController and add @Service annotation to CompteDAOHib. Let me know if you still face this issue.

Is it possible to pull just one file in Git?

git checkout master -- myplugin.js

master = branch name

myplugin.js = file name

Warning: #1265 Data truncated for column 'pdd' at row 1

As the message error says, you need to Increase the length of your column to fit the length of the data you are trying to insert (0000-00-00)


Following your comment, I run a test table:

mysql> create table testDate(id int(2) not null auto_increment, pdd date default null, primary key(id));
Query OK, 0 rows affected (0.20 sec)


mysql> insert into testDate values(1,'0000-00-00');
Query OK, 1 row affected (0.06 sec)


So, aparently you want to insert a NULL value to pdd field as your comment states ? You can do that in 2 ways like this:

Method 1:

mysql> insert into testDate values(2,'');
Query OK, 1 row affected, 1 warning (0.06 sec)

Method 2:

mysql> insert into testDate values(3,NULL);
Query OK, 1 row affected (0.07 sec)


You failed to change the default value of pdd field. Here is the syntax how to do it (in my case, I set it to NULL in the start, now I will change it to NOT NULL)

mysql> alter table testDate modify pdd date not null;
Query OK, 3 rows affected, 1 warning (0.60 sec)
Records: 3  Duplicates: 0  Warnings: 1

Install IPA with iTunes 11

For iTunes 12, drag the .ipa file from the Finder to the Apps area NOT inside your device (in iTunes)... alternately, you can just double click on the .ipa in the Finder.

Important note: you have to change Version and/or Build number. Otherwise, you get no notice from iTunes at all...

Then switch to your device in iTunes, and install or update the application.

Then hit sync.

Xcode couldn't find any provisioning profiles matching


  1. Unique name (across all Apple Apps)
  2. Have to sign in while your phone is connected (mine had a large warning here)

Worked great without restart on Xcode 10


How to join two JavaScript Objects, without using JQUERY

This simple function recursively merges JSON objects, please notice that this function merges all JSON into first param (target), if you need new object modify this code.

var mergeJSON = function (target, add) {
    function isObject(obj) {
        if (typeof obj == "object") {
            for (var key in obj) {
                if (obj.hasOwnProperty(key)) {
                    return true; // search for first object prop
        return false;
    for (var key in add) {
        if (add.hasOwnProperty(key)) {
            if (target[key] && isObject(target[key]) && isObject(add[key])) {
                this.mergeJSON(target[key], add[key]);
            } else {
                target[key] = add[key];
    return target;

BTW instead of isObject() function may be used condition like this:

JSON.stringify(add[key])[0] == "{"

but this is not good solution, because it's will take a lot of resources if we have large JSON objects.

Font Awesome 5 font-family issue

Strangely you have to include the font-family and the font-weight for it to work. Here is what worked for me:

.second-section-header::after {
    content: "\f259";
    font-family: 'Font Awesome\ 5 Free';
    font-weight: 900;

From there, you can begin adding any styles that you want.

Let's say:

.second-section-header::after {
    content: "\f259";
    font-family: 'Font Awesome\ 5 Free';
    font-weight: 900;
    font-size: 100px;
    color: white;
    z-index: 1;
    position: absolute;

I hope this helps.

iOS / Android cross platform development

If you've ever used LUA, you might try Corona SDK can create apps that run on IOS and Android

I've downloaded it and messed around some, I find LUA a very easy to learn scripting language without the usual scripting language hassles/limitations....

Java Desktop application: SWT vs. Swing

I whould choose swing just because it's "native" for java.

Plus, have a look at

How to my "exe" from PyCharm project

You cannot directly save a Python file as an exe and expect it to work -- the computer cannot automatically understand whatever code you happened to type in a text file. Instead, you need to use another program to transform your Python code into an exe.

I recommend using a program like Pyinstaller. It essentially takes the Python interpreter and bundles it with your script to turn it into a standalone exe that can be run on arbitrary computers that don't have Python installed (typically Windows computers, since Linux tends to come pre-installed with Python).

To install it, you can either download it from the linked website or use the command:

pip install pyinstaller

...from the command line. Then, for the most part, you simply navigate to the folder containing your source code via the command line and run:


You can find more information about how to use Pyinstaller and customize the build process via the documentation.

You don't necessarily have to use Pyinstaller, though. Here's a comparison of different programs that can be used to turn your Python code into an executable.

Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported for @RequestBody MultiValueMap

@PostMapping(path = "/my/endpoint", consumes = { MediaType.APPLICATION_FORM_URLENCODED_VALUE })
public ResponseEntity<Void> handleBrowserSubmissions(MyDTO dto) throws Exception {

That way works for me

Plot a line graph, error in xy.coords(x, y, xlabel, ylabel, log) : 'x' and 'y' lengths differ

plot(t) is in this case the same as

plot(t[[1]], t[[2]])

As the error message says, x and y differ in length and that is because you plot a list with length 4 against 1:

> length(t)
[1] 4
> length(1)
[1] 1

In your second example you plot a list with elements named x and y, both vectors of length 2, so plot plots these two vectors.


If you want to plot lines use

plot(t, type="l")

Setting active profile and config location from command line in spring boot

I had to add this:

bootRun {
    String activeProfile =['']
    String confLoc =['spring.config.location']
    systemProperty "", activeProfile
    systemProperty "spring.config.location", "file:$confLoc"

And now bootRun picks up the profile and config locations.

Thanks a lot @jst for the pointer.

Get PHP class property by string

If you want to access the property without creating an intermediate variable, use the {} notation:

$something = $object->{'something'};

That also allows you to build the property name in a loop for example:

for ($i = 0; $i < 5; $i++) {
    $something = $object->{'something' . $i};
    // ...

Saving and loading objects and using pickle

It seems you want to save your class instances across sessions, and using pickle is a decent way to do this. However, there's a package called klepto that abstracts the saving of objects to a dictionary interface, so you can choose to pickle objects and save them to a file (as shown below), or pickle the objects and save them to a database, or instead of use pickle use json, or many other options. The nice thing about klepto is that by abstracting to a common interface, it makes it easy so you don't have to remember the low-level details of how to save via pickling to a file, or otherwise.

Note that It works for dynamically added class attributes, which pickle cannot do...

dude@hilbert>$ python
Python 2.7.6 (default, Nov 12 2013, 13:26:39) 
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from klepto.archives import file_archive 
>>> db = file_archive('fruits.txt')
>>> class Fruits: pass
>>> banana = Fruits()
>>> banana.color = 'yellow'
>>> banana.value = 30
>>> db['banana'] = banana 
>>> db.dump()

Then we restart…

dude@hilbert>$ python
Python 2.7.6 (default, Nov 12 2013, 13:26:39) 
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from klepto.archives import file_archive
>>> db = file_archive('fruits.txt')
>>> db.load()
>>> db['banana'].color

Klepto works on python2 and python3.

Get the code here:

When maven says "resolution will not be reattempted until the update interval of MyRepo has elapsed", where is that interval specified?

What basically happens is,According to default updatePolicy of maven.Maven will fetch the jars from repo on daily basis.So if during 1st attempt your internet was not working then it would not try to fetch this jar again untill 24hours spent.

Resolution :

Either use

mvn -U clean install

where -U will force update the repo

or use

          <name>My Repository</name>

in your settings.xml

Laravel 5.1 API Enable Cors

After wasting a lot of time I finally found this silly mistake which might help you as well.

If you can't return response from your route either through function closure or through controller action then it won't work.



Route::post('login', function () {
    return response()->json(['key' => 'value'], 200); //Make sure your response is there.

Controller Action


class AuthController extends Controller {


     public function login() {
          return response()->json(['key' => 'value'], 200); //Make sure your response is there.




Chrome -> Developer Tools -> Network tab

enter image description here

If anything goes wrong then your response headers won't be here.

Image overlay on responsive sized images bootstrap

When you specify position:absolute it positions itself to the next-highest element with position:relative. In this case, that's the .project div.

If you give the image's immediate parent div a style of position:relative, the overlay will key to that instead of the div which includes the text. For example:

 <div class="parent">
    <img src="" class="img-responsive"/>
    <div class="fa fa-plus project-overlay"></div>

.parent {
   position: relative;

Connect multiple devices to one device via Bluetooth

Bluetooth 4.0 Allows you in a Bluetooth piconet one master can communicate up to 7 active slaves, there can be some other devices up to 248 devices which sleeping.

Also you can use some slaves as bridge to participate with more devices.

What's the difference between event.stopPropagation and event.preventDefault?

 alert("parent click event fired !");_x000D_
<script src=""></script>_x000D_
<div id="foo">_x000D_
  <button id="but">button</button>_x000D_

Setting focus to iframe contents

Here is code to create an iframe using jQuery, append it to the document, poll it until it is loaded, then focus it. This is better than setting an arbitrary timeout which may or may not work depending on how long the iframe takes to load.

var jqueryIframe = $('<iframe>', {
    src: ""
focusWhenReady = function(){
    var iframe = jqueryIframe[0],
    doc = iframe.contentDocument || iframe.contentWindow.document;
    if (doc.readyState == "complete") {
    } else {
        setTimeout(focusWhenReady, 100)
setTimeout(focusWhenReady, 10);

The code for detecting when the iframe is loaded was adapted from Biranchi's answer to How to check if iframe is loaded or it has a content?

How do you replace double quotes with a blank space in Java?

Use String#replace().

To replace them with spaces (as per your question title):

System.out.println("I don't like these \"double\" quotes".replace("\"", " "));

The above can also be done with characters:

System.out.println("I don't like these \"double\" quotes".replace('"', ' '));

To remove them (as per your example):

System.out.println("I don't like these \"double\" quotes".replace("\"", ""));

Get local IP address

I know this may be kicking a dead horse, but maybe this can help someone. I have looked all over the place for a way to find my local IP address, but everywhere I find it says to use:


I don't like this at all because it just gets all the addresses assigned to your computer. If you have multiple network interfaces (which pretty much all computers do now-a-days) you have no idea which address goes with which network interface. After doing a bunch of research I created a function to use the NetworkInterface class and yank the information out of it. This way I can tell what type of interface it is (Ethernet, wireless, loopback, tunnel, etc.), whether it is active or not, and SOOO much more.

public string GetLocalIPv4(NetworkInterfaceType _type)
    string output = "";
    foreach (NetworkInterface item in NetworkInterface.GetAllNetworkInterfaces())
        if (item.NetworkInterfaceType == _type && item.OperationalStatus == OperationalStatus.Up)
            foreach (UnicastIPAddressInformation ip in item.GetIPProperties().UnicastAddresses)
                if (ip.Address.AddressFamily == AddressFamily.InterNetwork)
                    output = ip.Address.ToString();
    return output;

Now to get the IPv4 address of your Ethernet network interface call:


Or your Wireless interface:


If you try to get an IPv4 address for a wireless interface, but your computer doesn't have a wireless card installed it will just return an empty string. Same thing with the Ethernet interface.

Hope this helps someone! :-)


It was pointed out (thanks @NasBanov) that even though this function goes about extracting the IP address in a much better way than using Dns.GetHostEntry(Dns.GetHostName()) it doesn't do very well at supporting multiple interfaces of the same type or multiple IP addresses on a single interface. It will only return a single IP address when there may be multiple addresses assigned. To return ALL of these assigned addresses you could simply manipulate the original function to always return an array instead of a single string. For example:

public static string[] GetAllLocalIPv4(NetworkInterfaceType _type)
    List<string> ipAddrList = new List<string>();
    foreach (NetworkInterface item in NetworkInterface.GetAllNetworkInterfaces())
        if (item.NetworkInterfaceType == _type && item.OperationalStatus == OperationalStatus.Up)
            foreach (UnicastIPAddressInformation ip in item.GetIPProperties().UnicastAddresses)
                if (ip.Address.AddressFamily == AddressFamily.InterNetwork)
    return ipAddrList.ToArray();

Now this function will return ALL assigned addresses for a specific interface type. Now to get just a single string, you could use the .FirstOrDefault() extension to return the first item in the array or, if it's empty, return an empty string.


Converting to UTC timestamp in Python

If d = date(2011, 1, 1) is in UTC:

>>> from datetime import datetime, date
>>> import calendar
>>> timestamp1 = calendar.timegm(d.timetuple())
>>> datetime.utcfromtimestamp(timestamp1)
datetime.datetime(2011, 1, 1, 0, 0)

If d is in local timezone:

>>> import time
>>> timestamp2 = time.mktime(d.timetuple()) # DO NOT USE IT WITH UTC DATE
>>> datetime.fromtimestamp(timestamp2)
datetime.datetime(2011, 1, 1, 0, 0)

timestamp1 and timestamp2 may differ if midnight in the local timezone is not the same time instance as midnight in UTC.

mktime() may return a wrong result if d corresponds to an ambiguous local time (e.g., during DST transition) or if d is a past(future) date when the utc offset might have been different and the C mktime() has no access to the tz database on the given platform. You could use pytz module (e.g., via tzlocal.get_localzone()) to get access to the tz database on all platforms. Also, utcfromtimestamp() may fail and mktime() may return non-POSIX timestamp if "right" timezone is used.

To convert object that represents date in UTC without calendar.timegm():

DAY = 24*60*60 # POSIX day in seconds (exact value)
timestamp = (utc_date.toordinal() - date(1970, 1, 1).toordinal()) * DAY
timestamp = (utc_date - date(1970, 1, 1)).days * DAY

How can I get a date converted to seconds since epoch according to UTC?

To convert datetime.datetime (not object that already represents time in UTC to the corresponding POSIX timestamp (a float).

Python 3.3+


from datetime import timezone

timestamp = dt.replace(tzinfo=timezone.utc).timestamp()

Note: It is necessary to supply timezone.utc explicitly otherwise .timestamp() assume that your naive datetime object is in local timezone.

Python 3 (< 3.3)

From the docs for datetime.utcfromtimestamp():

There is no method to obtain the timestamp from a datetime instance, but POSIX timestamp corresponding to a datetime instance dt can be easily calculated as follows. For a naive dt:

timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)

And for an aware dt:

timestamp = (dt - datetime(1970,1,1, tzinfo=timezone.utc)) / timedelta(seconds=1)

Interesting read: Epoch time vs. time of day on the difference between What time is it? and How many seconds have elapsed?

See also: datetime needs an "epoch" method

Python 2

To adapt the above code for Python 2:

timestamp = (dt - datetime(1970, 1, 1)).total_seconds()

where timedelta.total_seconds() is equivalent to (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6) / 10**6 computed with true division enabled.


from __future__ import division
from datetime import datetime, timedelta

def totimestamp(dt, epoch=datetime(1970,1,1)):
    td = dt - epoch
    # return td.total_seconds()
    return (td.microseconds + (td.seconds + td.days * 86400) * 10**6) / 10**6 

now = datetime.utcnow()
print now
print totimestamp(now)

Beware of floating-point issues.


2012-01-08 15:34:10.022403

How to convert an aware datetime object to POSIX timestamp

assert dt.tzinfo is not None and dt.utcoffset() is not None
timestamp = dt.timestamp() # Python 3.3+

On Python 3:

from datetime import datetime, timedelta, timezone

epoch = datetime(1970, 1, 1, tzinfo=timezone.utc)
timestamp = (dt - epoch) / timedelta(seconds=1)
integer_timestamp = (dt - epoch) // timedelta(seconds=1)

On Python 2:

# utc time = local time              - utc offset
utc_naive  = dt.replace(tzinfo=None) - dt.utcoffset()
timestamp = (utc_naive - datetime(1970, 1, 1)).total_seconds()

How to make a UILabel clickable?

Good and convenient solution:

In your ViewController:

@IBOutlet weak var label: LabelButton!

override func viewDidLoad() {

    self.label.onClick = {
        // TODO

You can place this in your ViewController or in another .swift file(e.g. CustomView.swift):

@IBDesignable class LabelButton: UILabel {
    var onClick: () -> Void = {}
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {

In Storyboard select Label and on right pane in "Identity Inspector" in field class select LabelButton.

Don't forget to enable in Label Attribute Inspector "User Interaction Enabled"

Replace or delete certain characters from filenames of all files in a folder

This batch file can help, but it has some limitations. The filename characters = and % cannot be replaced (going from memory here) and an ^ in the filenames might be a problem too.

In this portion %newname: =_% on every line in the lower block it replaces the character after : with the character after = so as it stands the bunch of characters are going to be replaced with an underscore.

Remove the echo to activate the ren command as it will merely print the commands to the console window until you do.

It will only process the current folder, unless you add /s to the DIR command portion and then it will process all folders under the current one too.

To delete a certain character, remove the character from after the = sign. In %newname:z=% an entry like this would remove all z characters (case insensitive).

@echo off
for /f "delims=" %%a in ('dir /a:-d /o:n /b') do call :next "%%a"
set "newname=%~nx1"

set "newname=%newname: =_%"
set "newname=%newname:)=_%"
set "newname=%newname:(=_%"
set "newname=%newname:&=_%"
set "newname=%newname:^=_%"
set "newname=%newname:$=_%"
set "newname=%newname:#=_%"
set "newname=%newname:@=_%"
set "newname=%newname:!=_%"
set "newname=%newname:-=_%"
set "newname=%newname:+=_%"
set "newname=%newname:}=_%"
set "newname=%newname:{=_%"
set "newname=%newname:]=_%"
set "newname=%newname:[=_%"
set "newname=%newname:;=_%"
set "newname=%newname:'=_%"
set "newname=%newname:`=_%"
set "newname=%newname:,=_%"

echo ren %1 "%newname%

What is "android.R.layout.simple_list_item_1"?

Zakaria, that is a reference to an built-in XML layout document that is part of the Android OS, rather than one of your own XML layouts.

Here is a further list of layouts that you can use:
(Updated link thanks @Estel: )

You can actually view the code for the layouts.

Subset dataframe by multiple logical conditions of rows to remove

data <- data[-which(data[,1] %in% c("b","d","e")),]

How do I revert my changes to a git submodule?

do 4 steps sequential:

git submodule foreach git reset --hard HEAD
git submodule update
git submodule foreach "git checkout master; git pull"
git submodule foreach git clean -f

What does 'super' do in Python?

What's the difference?


means to call SomeBaseClass's __init__. while

super(Child, self).__init__()

means to call a bound __init__ from the parent class that follows Child in the instance's Method Resolution Order (MRO).

If the instance is a subclass of Child, there may be a different parent that comes next in the MRO.

Explained simply

When you write a class, you want other classes to be able to use it. super() makes it easier for other classes to use the class you're writing.

As Bob Martin says, a good architecture allows you to postpone decision making as long as possible.

super() can enable that sort of architecture.

When another class subclasses the class you wrote, it could also be inheriting from other classes. And those classes could have an __init__ that comes after this __init__ based on the ordering of the classes for method resolution.

Without super you would likely hard-code the parent of the class you're writing (like the example does). This would mean that you would not call the next __init__ in the MRO, and you would thus not get to reuse the code in it.

If you're writing your own code for personal use, you may not care about this distinction. But if you want others to use your code, using super is one thing that allows greater flexibility for users of the code.

Python 2 versus 3

This works in Python 2 and 3:

super(Child, self).__init__()

This only works in Python 3:


It works with no arguments by moving up in the stack frame and getting the first argument to the method (usually self for an instance method or cls for a class method - but could be other names) and finding the class (e.g. Child) in the free variables (it is looked up with the name __class__ as a free closure variable in the method).

I prefer to demonstrate the cross-compatible way of using super, but if you are only using Python 3, you can call it with no arguments.

Indirection with Forward Compatibility

What does it give you? For single inheritance, the examples from the question are practically identical from a static analysis point of view. However, using super gives you a layer of indirection with forward compatibility.

Forward compatibility is very important to seasoned developers. You want your code to keep working with minimal changes as you change it. When you look at your revision history, you want to see precisely what changed when.

You may start off with single inheritance, but if you decide to add another base class, you only have to change the line with the bases - if the bases change in a class you inherit from (say a mixin is added) you'd change nothing in this class. Particularly in Python 2, getting the arguments to super and the correct method arguments right can be difficult. If you know you're using super correctly with single inheritance, that makes debugging less difficult going forward.

Dependency Injection

Other people can use your code and inject parents into the method resolution:

class SomeBaseClass(object):
    def __init__(self):
        print('SomeBaseClass.__init__(self) called')

class UnsuperChild(SomeBaseClass):
    def __init__(self):
        print('UnsuperChild.__init__(self) called')

class SuperChild(SomeBaseClass):
    def __init__(self):
        print('SuperChild.__init__(self) called')
        super(SuperChild, self).__init__()

Say you add another class to your object, and want to inject a class between Foo and Bar (for testing or some other reason):

class InjectMe(SomeBaseClass):
    def __init__(self):
        print('InjectMe.__init__(self) called')
        super(InjectMe, self).__init__()

class UnsuperInjector(UnsuperChild, InjectMe): pass

class SuperInjector(SuperChild, InjectMe): pass

Using the un-super child fails to inject the dependency because the child you're using has hard-coded the method to be called after its own:

>>> o = UnsuperInjector()
UnsuperChild.__init__(self) called
SomeBaseClass.__init__(self) called

However, the class with the child that uses super can correctly inject the dependency:

>>> o2 = SuperInjector()
SuperChild.__init__(self) called
InjectMe.__init__(self) called
SomeBaseClass.__init__(self) called

Addressing a comment

Why in the world would this be useful?

Python linearizes a complicated inheritance tree via the C3 linearization algorithm to create a Method Resolution Order (MRO).

We want methods to be looked up in that order.

For a method defined in a parent to find the next one in that order without super, it would have to

  1. get the mro from the instance's type
  2. look for the type that defines the method
  3. find the next type with the method
  4. bind that method and call it with the expected arguments

The UnsuperChild should not have access to InjectMe. Why isn't the conclusion "Always avoid using super"? What am I missing here?

The UnsuperChild does not have access to InjectMe. It is the UnsuperInjector that has access to InjectMe - and yet cannot call that class's method from the method it inherits from UnsuperChild.

Both Child classes intend to call a method by the same name that comes next in the MRO, which might be another class it was not aware of when it was created.

The one without super hard-codes its parent's method - thus is has restricted the behavior of its method, and subclasses cannot inject functionality in the call chain.

The one with super has greater flexibility. The call chain for the methods can be intercepted and functionality injected.

You may not need that functionality, but subclassers of your code may.


Always use super to reference the parent class instead of hard-coding it.

What you intend is to reference the parent class that is next-in-line, not specifically the one you see the child inheriting from.

Not using super can put unnecessary constraints on users of your code.

Angular - Set headers for every request

After some investigation, I found the final and the most easy way is to extend BaseRequestOptions which I prefer.
The following are the ways I tried and give up for some reason:
1. extend BaseRequestOptions, and add dynamic headers in constructor(). It can not work if I login. It will be created once. So it is not dynamic.
2. extend Http. Same reason as above, I can not add dynamic headers in constructor(). And if I rewrite request(..) method, and set headers, like this:

request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {
 let token = localStorage.getItem(AppConstants.tokenName);
 if (typeof url === 'string') { // meaning we have to add the token to the options, not in url
  if (!options) {
    options = new RequestOptions({});
  options.headers.set('Authorization', 'token_value');
 } else {
  url.headers.set('Authorization', 'token_value');
 return super.request(url, options).catch(this.catchAuthError(this));

You just need to overwrite this method, but not every get/post/put methods.

3.And my preferred solution is extend BaseRequestOptions and overwrite merge() :

export class AuthRequestOptions extends BaseRequestOptions {

 merge(options?: RequestOptionsArgs): RequestOptions {
  var newOptions = super.merge(options);
  let token = localStorage.getItem(AppConstants.tokenName);
  newOptions.headers.set(AppConstants.authHeaderName, token);
  return newOptions;

this merge() function will be called for every request.

R: `which` statement with multiple conditions

The && function is not vectorized. You need the & function:

EUR <- PCs[which(PCs$V13 < 9 & PCs$V13 > 3), ]

Find all table names with column name?

You could do this:

SELECT AS table_name,
SCHEMA_NAME(schema_id) AS schema_name, AS column_name
FROM sys.tables AS t
WHERE LIKE '%MyColumn%'
ORDER BY schema_name, table_name;