Programs & Examples On #Testautomationfx

Gradle Sync failed could not find constraint-layout:1.0.0-alpha2


constraint layout dependency

works for me

What are the differences between Deferred, Promise and Future in JavaScript?

A Promise represents a proxy for a value not necessarily known when the promise is created. It allows you to associate handlers to an asynchronous action's eventual success value or failure reason. This lets asynchronous methods return values like synchronous methods: instead of the final value, the asynchronous method returns a promise of having a value at some point in the future.

The deferred.promise() method allows an asynchronous function to prevent other code from interfering with the progress or status of its internal request. The Promise exposes only the Deferred methods needed to attach additional handlers or determine the state (then, done, fail, always, pipe, progress, state and promise), but not ones that change the state (resolve, reject, notify, resolveWith, rejectWith, and notifyWith).

If target is provided, deferred.promise() will attach the methods onto it and then return this object rather than create a new one. This can be useful to attach the Promise behavior to an object that already exists.

If you are creating a Deferred, keep a reference to the Deferred so that it can be resolved or rejected at some point. Return only the Promise object via deferred.promise() so other code can register callbacks or inspect the current state.

Simply we can say that a Promise represents a value that is not yet known where as a Deferred represents work that is not yet finished.

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How to add color to Github's file

I added some color to a GitHub markup page using emoji Enicode chars, e.g. or -- some emoji characters are colored in some browsers.

There are also some colored emoji alphabets: blood types ???; parking sign ?; Metro sign ??; a few others with two or more letters, such as , and boxed digits such as 0??. Flag emojis will show as letters (often colored) if the flag is not available: .

However, I don't think there is a complete colored alphabet defined in emoji.

HttpServletRequest to complete URL


public static String getUrl(HttpServletRequest req) {
    String reqUrl = req.getRequestURL().toString();
    String queryString = req.getQueryString();   // d=789
    if (queryString != null) {
        reqUrl += "?"+queryString;
    return reqUrl;

.gitignore for Visual Studio Projects and Solutions

Late to the party here, but I also find that I use the following. Some may only be useful for hiding sensitive files when pushing to a public remote.

#Ignore email files delivered to specified pickup directory

#Allow NuGet.exe (do not ignore)

#Ignore WebDeploy publish profiles

#Ignore Azure build csdef & Pubxml files

#Allow ReSharper .DotSettings (for non-namespace-provider properties)

#Ignore private folder

HTTPS setup in Amazon EC2

You need to register a domain(on GoDaddy for example) and put a load balancer in front of your ec2 instance - as DigaoParceiro said in his answer.

The issue is that domains generated by amazon on your ec2 instances are ephemeral. Today the domain is belonging to you, tomorrow it may not.

For that reason, let's encrypt throws an error when you try to register a certificate on amazon generated domain that states:

The ACME server refuses to issue a certificate for this domain name, because it is forbidden by policy

More details about this here:

Convert between UIImage and Base64 string

Decoding using convenience initialiser - Swift 5

extension UIImage {
    convenience init?(base64String: String) {
        guard let data = Data(base64Encoded: base64String) else { return nil }
        self.init(data: data)

Fragment Inside Fragment

That may help those who works on Kotlin you can use extension function so create a kotlin file let's say "util.kt" and add this piece of code

fun Fragment.addChildFragment(fragment: Fragment, frameId: Int) {

    val transaction = childFragmentManager.beginTransaction()
    transaction.replace(frameId, fragment).commit()

Let's say this is the class of the child

class InputFieldPresentation: Fragment()
    var views: View? = null
    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        views = inflater!!.inflate(R.layout.input_field_frag, container, false)
        return views

    override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

Now you can add the children to the father fragment like this


    override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        val fieldFragment= InputFieldPresentation()

where is the id of the layout which will contain the fragment.This lyout is inside the father fragment of course. Here is an example


<LinearLayout android:layout_width="match_parent"




Sending message through WhatsApp

To check if WhatsApp is installed in device and initiate "click to chat" in WhatsApp:


try {
    // Check if whatsapp is installed
    context?.packageManager?.getPackageInfo("com.whatsapp", PackageManager.GET_META_DATA)
    val intent = Intent(Intent.ACTION_VIEW, Uri.parse("$internationalPhoneNumber"))
} catch (e: NameNotFoundException) {
    Toast.makeText(context, "WhatsApp not Installed", Toast.LENGTH_SHORT).show()


try {
    // Check if whatsapp is installed
    getPackageManager().getPackageInfo("com.whatsapp", PackageManager.GET_META_DATA);
    Intent intent = Intent(Intent.ACTION_VIEW, Uri.parse("" + internationalPhoneNumber));
} catch (NameNotFoundException e) {
    Toast.makeText(context, "WhatsApp not Installed", Toast.LENGTH_SHORT).show();

getPackageInfo() throws NameNotFoundException if WhatsApp is not installed.

The internationalPhoneNumber variable is used to access the phone number.


Android 6.0 multiple permissions

Use helper like this (permissions names do not matter).

public class MyPermission {

private static final int PERMISSION_REQUEST_ALL = 127;
private MainActivity mMainActivity;

MyPermission(MainActivity mainActivity) {
    mMainActivity = mainActivity;

public static boolean hasPermission(String permission, Context context) {
    if (isNewPermissionModel()) {
        return (ActivityCompat.checkSelfPermission(context, permission) == PackageManager.PERMISSION_GRANTED);
    return true;

private static boolean hasPermissions(Context context, String... permissions) {
    if (isNewPermissionModel() && context != null && permissions != null) {
        for (String permission : permissions) {
            if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
                return false;
    return true;

private static boolean shouldShowRationale(Activity activity, String permission) {
    return isNewPermissionModel() && ActivityCompat.shouldShowRequestPermissionRationale(activity, permission);

private static boolean isNewPermissionModel() {

 * check all permissions
void checkAll() {
    //check dangerous permissions, make request if need (Android will ask only for the ones it needs)
    String[] PERMISSIONS = {

    if (!hasPermissions(mMainActivity, PERMISSIONS)) {
        ActivityCompat.requestPermissions(mMainActivity, PERMISSIONS, PERMISSION_REQUEST_ALL);

void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    if (requestCode == PERMISSION_REQUEST_ALL) {
        if (grantResults.length > 0) {
            //for not granted
            for (int i = 0; i < permissions.length; i++) {

                if (permissions[i].equals(permission.READ_CALENDAR)) {
                    if (grantResults[i] != PackageManager.PERMISSION_GRANTED) {
                        smartRequestPermissions(permission.READ_CALENDAR, R.string.permission_required_dialog_read_calendar);
                } else if (permissions[i].equals(permission.ACCESS_COARSE_LOCATION)) {
                    if (grantResults[i] != PackageManager.PERMISSION_GRANTED) {
                        smartRequestPermissions(permission.ACCESS_COARSE_LOCATION, R.string.permission_required_dialog_access_coarse_location);


private void smartRequestPermissions(final String permissionName, int permissionRequiredDialog) {
    if (shouldShowRationale(mMainActivity, permissionName)) {// If the user turned down the permission request in the past and chose the Don't ask again option in the permission request system dialog, this method returns false.

        //Show an explanation to the user with action
                new SnackProgressBar(
                        SnackProgressBar.TYPE_ACTION, mMainActivity.getString(permissionRequiredDialog)
                        .setAction("OK", new OnActionClickListener() {
                            public void onActionClick() {
                , MainActivity.SNACKBAR_WARNING_DURATION

    } // else do nothing


Rounding to 2 decimal places in SQL

Try using the COLUMN command with the FORMAT option for that:


How do I parse a HTML page with Node.js

November 2020 Update

I searched for the top NodeJS html parser libraries.

Because my use cases didn't require a library with many features, I could focus on stability and performance.

By stability I mean that I want the library to be used long enough by the community in order to find bugs and that it will be still maintained and that open issues will be closed.

Its hard to understand the future of an open source library, but I did a small summary based on the top 10 libraries in openbase.

I divided into 2 groups according to the last commit (and on each group the order is according to Github starts):

Last commit is in the last 6 months:

jsdom - Last commit: 3 Months, Open issues: 331, Github stars: 14.9K.

htmlparser2 - Last commit: 8 days, Open issues: 2, Github stars: 2.7K.

parse5 - Last commit: 2 Months, Open issues: 21, Github stars: 2.5K.

swagger-parser - Last commit: 2 Months, Open issues: 48, Github stars: 663.

html-parse-stringify - Last commit: 4 Months, Open issues: 3, Github stars: 215.

node-html-parser - Last commit: 7 days, Open issues: 15, Github stars: 205.

Last commit is 6 months and above:

cheerio - Last commit: 1 year, Open issues: 174, Github stars: 22.9K.

koa-bodyparser - Last commit: 6 months, Open issues: 9, Github stars: 1.1K.

sax-js - Last commit: 3 Years, Open issues: 65, Github stars: 941.

draftjs-to-html - Last commit: 1 Year, Open issues: 27, Github stars: 233.

I picked Node-html-parser because it seems quiet fast and very active at this moment.

(*) Openbase adds much more information regarding each library like the number of contributors (with +3 commits), weekly downloads, Monthly commits, Version etc'.

(**) The table above is a snapshot according to the specific time and date - I would check the reference again and as a first step check the level of recent activity and then dive into the smaller details.

show/hide a div on hover and hover out

Here are different method of doing this. And i found your code is even working fine.

Your code:

Jquery toggle class demo:

Jquery fade toggle:

Jquery slide toggle:

And you can do this with CSS as answered by Sandeep

When do you use Git rebase instead of Git merge?

Before merge/rebase:

A <- B <- C    [master]
  D <- E       [branch]

After git merge master:

A <- B <- C
^         ^
 \         \
  D <- E <- F

After git rebase master:

A <- B <- C <- D' <- E'

(A, B, C, D, E and F are commits)

This example and much more well illustrated information about Git can be found in Git The Basics Tutorial.

How to concatenate strings in django templates?

From the docs:

This tag can be used in two ways:

  • {% extends "base.html" %} (with quotes) uses the literal value "base.html" as the name of the parent template to extend.
  • {% extends variable %} uses the value of variable. If the variable evaluates to a string, Django will use that string as the name of the parent template. If the variable evaluates to a Template object, Django will use that object as the parent template.

So seems like you can't use a filter to manipulate the argument. In the calling view you have to either instantiate the ancestor template or create an string variable with the correct path and pass it with the context.

How do I divide so I get a decimal value?

You can do like,

int a = 3;
int b = 2;
int quotient = a / b;
int remainder = a % b;

To get quotient in real numbers

System.out.println((double) a / b);

To get quotient in integer numbers

System.out.println("Quotient: " + quotient);
System.out.println("Remainder: " + remainder);

To get quotient in real number such that one number after decimal

System.out.println(a / b + "." + a % b * 10 / b);

Note: In the last method it will not round the number up after the decimal.

Drop rows with all zeros in pandas data frame

You can use a quick lambda function to check if all the values in a given row are 0. Then you can use the result of applying that lambda as a way to choose only the rows that match or don't match that condition:

import pandas as pd
import numpy as np


df = pd.DataFrame(np.random.randn(5,3), 
                  index=['one', 'two', 'three', 'four', 'five'],

df.loc[['one', 'three']] = 0

print df
print df.loc[~df.apply(lambda row: (row==0).all(), axis=1)]


              a         b         c
one    0.000000  0.000000  0.000000
two    2.240893  1.867558 -0.977278
three  0.000000  0.000000  0.000000
four   0.410599  0.144044  1.454274
five   0.761038  0.121675  0.443863

[5 rows x 3 columns]
             a         b         c
two   2.240893  1.867558 -0.977278
four  0.410599  0.144044  1.454274
five  0.761038  0.121675  0.443863

[3 rows x 3 columns]

How can I execute PHP code from the command line?

Using PHP from the command line

Use " instead of ' on Windows when using the CLI version with -r:

php -r "echo 1;"

-- correct

php -r 'echo 1;'

-- incorrect

  PHP Parse error:  syntax error, unexpected ''echo' (T_ENCAPSED_AND_WHITESPACE), expecting end of file in Command line code on line 1

Don't forget the semicolon to close the line.

How do I find numeric columns in Pandas?

def is_type(df, baseType):
    import numpy as np
    import pandas as pd
    test = [issubclass(np.dtype(d).type, baseType) for d in df.dtypes]
    return pd.DataFrame(data = test, index = df.columns, columns = ["test"])
def is_float(df):
    import numpy as np
    return is_type(df, np.float)
def is_number(df):
    import numpy as np
    return is_type(df, np.number)
def is_integer(df):
    import numpy as np
    return is_type(df, np.integer)

Deep copy in ES6 using the spread syntax

I myself landed on these answers last day, trying to find a way to deep copy complex structures, which may include recursive links. As I wasn't satisfied with anything being suggested before, I implemented this wheel myself. And it works quite well. Hope it helps someone.

Example usage:

OriginalStruct.deep_copy = deep_copy; // attach the function as a method

TheClone = OriginalStruct.deep_copy();

Please look at for live examples how to use it, and also deep_print() is there.

If you need it quick, right here's the source of deep_copy() function:

function deep_copy() {
    'use strict';   // required for undef test of 'this' below

    // Copyright (c) 2019, Leonid Titov, Mentions Highly Appreciated.

    var id_cnt = 1;
    var all_old_objects = {};
    var all_new_objects = {};
    var root_obj = this;

    if (root_obj === undefined) {
        console.log(`deep_copy() error: wrong call context`);

    var new_obj = copy_obj(root_obj);

    for (var id in all_old_objects) {
        delete all_old_objects[id].__temp_id;

    return new_obj;

    function copy_obj(o) {
        var new_obj = {};
        if (o.__temp_id === undefined) {
            o.__temp_id = id_cnt;
            all_old_objects[id_cnt] = o;
            all_new_objects[id_cnt] = new_obj;
            id_cnt ++;

            for (var prop in o) {
                if (o[prop] instanceof Array) {
                    new_obj[prop] = copy_array(o[prop]);
                else if (o[prop] instanceof Object) {
                    new_obj[prop] = copy_obj(o[prop]);
                else if (prop === '__temp_id') {
                else {
                    new_obj[prop] = o[prop];
        else {
            new_obj = all_new_objects[o.__temp_id];
        return new_obj;
    function copy_array(a) {
        var new_array = [];
        if (a.__temp_id === undefined) {
            a.__temp_id = id_cnt;
            all_old_objects[id_cnt] = a;
            all_new_objects[id_cnt] = new_array;
            id_cnt ++;

            a.forEach((v,i) => {
                if (v instanceof Array) {
                    new_array[i] = copy_array(v);
                else if (v instanceof Object) {
                    new_array[i] = copy_object(v);
                else {
                    new_array[i] = v;
        else {
            new_array = all_new_objects[a.__temp_id];
        return new_array;


wamp server does not start: Windows 7, 64Bit

Check your apache error log. I had this error "[error] (OS 5)Access is denied. : could not open transfer log file C:/wamp/logs/access.log. Unable to open logs" Then I rename my "access.log" to other name, you can delete if you don't need/never see your access log. Then restart your apache service. This happen because the file size too big. I think if you trying to open this file using notepad, it will not open, I tried to open that before. Hope it help.

Sorting by date & time in descending order?

If you mean you want to sort by date first then by names

SELECT id, name, form_id, DATE(updated_at) as date
  FROM wp_frm_items
  WHERE user_id = 11 && form_id=9
  ORDER BY updated_at DESC,name ASC

This will sort the records by date first, then by names

Display JSON Data in HTML Table

check below link to convert JSON data to standard HTML table in the simplest and fastest way.

How can I convert a dictionary into a list of tuples?

>>> d = { 'a': 1, 'b': 2, 'c': 3 }
>>> d.items()
[('a', 1), ('c', 3), ('b', 2)]
>>> [(v, k) for k, v in d.iteritems()]
[(1, 'a'), (3, 'c'), (2, 'b')]

It's not in the order you want, but dicts don't have any specific order anyway.1 Sort it or organize it as necessary.

See: items(), iteritems()

In Python 3.x, you would not use iteritems (which no longer exists), but instead use items, which now returns a "view" into the dictionary items. See the What's New document for Python 3.0, and the new documentation on views.

1: Insertion-order preservation for dicts was added in Python 3.7

How do I get AWS_ACCESS_KEY_ID for Amazon?

  1. Open the AWS Console
  2. Click on your username near the top right and select My Security Credentials
  3. Click on Users in the sidebar
  4. Click on your username
  5. Click on the Security Credentials tab
  6. Click Create Access Key
  7. Click Show User Security Credentials

Could not load file or assembly ... The parameter is incorrect

Clearing C:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files worked for me. Thinking of automating the deletion process to avoid the issue in future.

How to get to Model or Viewbag Variables in a Script Tag

Use single quotation marks ('):

var val = '@ViewBag.ForSection';

converting epoch time with milliseconds to datetime

Use datetime.datetime.fromtimestamp:

>>> import datetime
>>> s = 1236472051807 / 1000.0
>>> datetime.datetime.fromtimestamp(s).strftime('%Y-%m-%d %H:%M:%S.%f')
'2009-03-08 09:27:31.807000'

%f directive is only supported by datetime.datetime.strftime, not by time.strftime.

UPDATE Alternative using %, str.format:

>>> import time
>>> s, ms = divmod(1236472051807, 1000)  # (1236472051, 807)
>>> '%s.%03d' % (time.strftime('%Y-%m-%d %H:%M:%S', time.gmtime(s)), ms)
'2009-03-08 00:27:31.807'
>>> '{}.{:03d}'.format(time.strftime('%Y-%m-%d %H:%M:%S', time.gmtime(s)), ms)
'2009-03-08 00:27:31.807'

How to change a particular element of a C++ STL vector

at and operator[] both return a reference to the indexed element, so you can simply use: = -1;


l[4] = -1;

Could not find 3.2.25 4.0.30 4.1.32 4.2.40 4.2.42 4.3.23 4.4.52 5.0.77 5.0.89 5.2.08 6.1.11 6.1.71 6.5.87

I had the same problem because I had:

compile ''

and I solved changing the version numbers for a '+'. so the lines has to be:

compile ''

Get all child views inside LinearLayout at once

Get all views of a view plus its children recursively in Kotlin:

private fun View.getAllViews(): List<View> {
    if (this !is ViewGroup || childCount == 0) return listOf(this)

    return children
            .flatMap { it.getAllViews() }
            .plus(this as View)

In angular $http service, How can I catch the "status" of error?

UPDATED: As of angularjs 1.5, promise methods success and error have been deprecated. (see this answer)

from current docs:

$http.get('/someUrl', config).then(successCallback, errorCallback);
$'/someUrl', data, config).then(successCallback, errorCallback);

you can use the function's other arguments like so:

error(function(data, status, headers, config) {

see $http docs:

// Simple GET request example :
  success(function(data, status, headers, config) {
    // this callback will be called asynchronously
    // when the response is available
  error(function(data, status, headers, config) {
    // called asynchronously if an error occurs
    // or server returns response with an error status.

Styles.Render in MVC4

src="@url.content("~/Folderpath/*.css")" should render styles

What is the use of static variable in C#? When to use it? Why can't I declare the static variable inside method?

Static classes don't require you to create an object of that class/instantiate them, you can prefix the C# keyword static in front of the class name, to make it static.

Remember: we're not instantiating the Console class, String class, Array Class.

class Book
    public static int myInt = 0;

public class Exercise
    static void Main()
        Book book = new Book();
       //Use the class name directly to call the property myInt, 
      //don't use the object to access the value of property myInt




Excel Date to String conversion

Here is a VBA approach:

Sub change()
    toText Sheets(1).Range("A1:F20")
End Sub

Sub toText(target As Range)
Dim cell As Range
    For Each cell In target
        cell.Value = cell.Text
        cell.NumberFormat = "@"
    Next cell
End Sub

If you are looking for a solution without programming, the Question should be moved to SuperUser.

syntax error near unexpected token `('


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

How to pass variable from jade template file to a script file?

If you're like me and you use this method of passing variables a lot, here's a write-less-code solution.

In your node.js route, pass the variables in an object called window, like this:

router.get('/', function (req, res, next) {
    res.render('index', {
        window: {
            instance: instance

Then in your pug/jade layout file (just before the block content), you get them out like this:

if window
    each object, key in window
            window.!{key} = !{JSON.stringify(object)};

As my layout.pug file gets loaded with each pug file, I don't need to 'import' my variables over and over.

This way all variables/objects passed to window 'magically' end up in the real window object of your browser where you can use them in Reactjs, Angular, ... or vanilla javascript.

Scanner vs. BufferedReader

Scanner is used for parsing tokens from the contents of the stream while BufferedReader just reads the stream and does not do any special parsing.

In fact you can pass a BufferedReader to a scanner as the source of characters to parse.

Sorted array list in Java

Just make a new class like this:

public class SortedList<T> extends ArrayList<T> {

private final Comparator<? super T> comparator;

public SortedList() {
    this.comparator = null;

public SortedList(Comparator<T> comparator) {
    this.comparator = comparator;

public boolean add(T item) {
    int index = comparator == null ? Collections.binarySearch((List<? extends Comparable<? super T>>)this, item) :
            Collections.binarySearch(this, item, comparator);
    if (index < 0) {
        index = index * -1 - 2;
    super.add(index+1, item);
    return true;

public void add(int index, T item) {
    throw new UnsupportedOperationException("'add' with an index is not supported in SortedArrayList");

public boolean addAll(Collection<? extends T> items) {
    boolean allAdded = true;
    for (T item : items) {
        allAdded = allAdded && add(item);
    return allAdded;

public boolean addAll(int index, Collection<? extends T> items) {
    throw new UnsupportedOperationException("'addAll' with an index is not supported in SortedArrayList");


You can test it like this:

    List<Integer> list = new SortedArrayList<>((Integer i1, Integer i2) -> i1.compareTo(i2));
    for (Integer i : Arrays.asList(4, 7, 3, 8, 9, 25, 20, 23, 52, 3)) {

apache not accepting incoming connections from outside of localhost

this would work: -- for REDHAT use : cat "/etc/sysconfig/iptables"

iptables -I  RH-Firewall-1-INPUT -s  -p tcp -m tcp --dport 80 -j ACCEPT

followed by

sudo /etc/init.d/iptables save

Getting all selected checkboxes in an array

This should do the trick:


I don't think you've got other elements that can be checked, but if you do, you'd have to make it more specific:



spring PropertyPlaceholderConfigurer and context:property-placeholder

Following worked for me:
<context:property-placeholder location="file:src/resources/spring/"/>

Somehow "classpath:xxx" is not picking the file.

Web API Routing - api/{controller}/{action}/{id} "dysfunctions" api/{controller}/{id}

The route engine uses the same sequence as you add rules into it. Once it gets the first matched rule, it will stop checking other rules and take this to search for controller and action.

So, you should:

  1. Put your specific rules ahead of your general rules(like default), which means use RouteTable.Routes.MapHttpRoute to map "WithActionApi" first, then "DefaultApi".

  2. Remove the defaults: new { id = System.Web.Http.RouteParameter.Optional } parameter of your "WithActionApi" rule because once id is optional, url like "/api/{part1}/{part2}" will never goes into "DefaultApi".

  3. Add an named action to your "DefaultApi" to tell the route engine which action to enter. Otherwise once you have more than one actions in your controller, the engine won't know which one to use and throws "Multiple actions were found that match the request: ...". Then to make it matches your Get method, use an ActionNameAttribute.

So your route should like this:

// Map this rule first

    new { action="DefaultAction", id = System.Web.Http.RouteParameter.Optional }

And your controller:

[ActionName("DefaultAction")] //Map Action and you can name your method with any text
public string Get(int id)
    return "object of id id";

public IEnumerable<string> ByCategoryId(int id)
    return new string[] { "byCategory1", "byCategory2" };

Draw radius around a point in Google map

It seems that the most common method of achieving this is to draw a GPolygon with enough points to simulate a circle. The example you referenced uses this method. This page has a good example - look for the function drawCircle in the source code.

Why is "npm install" really slow?

I was able to resolve this from the comments section; outlining the process below.

From the comments

AndreFigueiredo stated :

I installed modules here in less than 1 min with your package.json with npm v3.5.2 and node v4.2.6. I suggest you update node and npm.

v1.3.0 didn't even have flattened dependencies introduced on v3 that resolved a lot of annoying issues

LINKIWI stated :

Generally speaking, don't rely on package managers like apt to maintain up-to-date software. I would strongly recommend purging the node/npm combo you installed from apt and following the instructions on to install the latest release.


Following their advice, I noticed that CentOS, Ubuntu, and Debian all use very outdated versions of nodejs and npm when retrieving the current version using apt or yum (depending on operating systems primary package manager).

Get rid of the outdated nodejs and npm

To resolve this with as minimal headache as possible, I ran the following command (on Ubuntu) :

apt-get purge --auto-remove nodejs npm

This purged the system of the archaic nodejs and npm as well as all dependencies which were no longer required

Install current nodejs and compatible npm

The next objective was to get a current version of both nodejs and npm which I can snag nodejs directly from here and either compile or use the binary, however this would not make it easy to swap versions as I need to (depending on age of project).

I came across a great package called nvm which (so far) seems to manage this task quite well. To install the current stable latest build of version 7 of nodejs :

Install nvm

curl -o- | bash

Source .bashrc

source ~/.bashrc

Use nvm to install nodejs 7.x

nvm install 7

After installation I was pleasantly surprised by much faster performance of npm, that it also now showed a pretty progress bar while snagging packages.

For those curious, the current (as of this date) version of npm should look like the following (and if it doesn't, you likely need to update it):

current npm running


DO NOT USE YOUR OS PACKAGE MANAGER TO INSTALL NODE.JS OR NPM - You will get very bad results as it seems no OS is keeping these packages (not even close to) current. If you find that npm is running slow and it isn't your computer or internet, it is most likely because of a severely outdated version.

BeautifulSoup: extract text from anchor tag

All the above answers really help me to construct my answer, because of this I voted for all the answers that other users put it out: But I finally put together my own answer to exact problem I was dealing with:

As question clearly defined I had to access some of the siblings and its children in a dom structure: This solution will iterate over the images in the dom structure and construct image name using product title and save the image to the local directory.

import urlparse
from urllib2 import urlopen
from urllib import urlretrieve
from BeautifulSoup import BeautifulSoup as bs
import requests

def getImages(url):
    #Download the images
    r = requests.get(url)
    html = r.text
    soup = bs(html)
    output_folder = '~/amazon'
    #extracting the images that in div(s)
    for div in soup.findAll('div', attrs={'class':'image'}):
        modified_file_name = None
            #getting the data div using findNext
            nextDiv =  div.findNext('div', attrs={'class':'data'})
            #use findNext again on previous object to get to the anchor tag
            fileName = nextDiv.findNext('a').text
            modified_file_name = fileName.replace(' ','-') + '.jpg'
        except TypeError:
            print 'skip'
        imageUrl = div.find('img')['src']
        outputPath = os.path.join(output_folder, modified_file_name)
        urlretrieve(imageUrl, outputPath)

if __name__=='__main__':
    url = r''

Meaning of "n:m" and "1:n" in database design

To explain the two concepts by example, imagine you have an order entry system for a bookstore. The mapping of orders to items is many to many (n:m) because each order can have multiple items, and each item can be ordered by multiple orders. On the other hand, a lookup between customers and order is one to many (1:n) because a customer can place more than one order, but an order is never for more than one customer.

MongoDB query multiple collections at once

Here is answer for your question.

    {$match : {admin : 1}},
    {$lookup: {from: "posts",localField: "_id",foreignField: "owner_id",as: "posts"}},
    {$project : {
            posts : { $filter : {input : "$posts"  , as : "post", cond : { $eq : ['$$post.via' , 'facebook'] } } },
            admin : 1



Or either you can go with mongodb group option.

    {$match : {admin : 1}},
    {$lookup: {from: "posts",localField: "_id",foreignField: "owner_id",as: "posts"}},
    {$unwind : "$posts"},
    {$match : {"posts.via":"facebook"}},
    { $group : {
            _id : "$_id",
            posts : {$push : "$posts"}

What is the meaning of 'No bundle URL present' in react-native?

export FORCE_BUNDLING=true worked for me. There was a warning in the console that it was not getting bundled.

How to hide the Google Invisible reCAPTCHA badge

I decided to hide the badge on all pages except my contact page (using Wordpress):

/* Hides the reCAPTCHA on every page */
.grecaptcha-badge {
    visibility: hidden !important;

/* Shows the reCAPTCHA on the Contact page */
/* Obviously change the page number to your own */
.page-id-17 .grecaptcha-badge {
    visibility: visible !important;

I'm not a web developer so please correct me if there's something wrong.

EDIT: Updated to use visibility instead of display.

What is the purpose of the : (colon) GNU Bash builtin?

It's also useful for polyglot programs:

#!/usr/bin/env sh
':' //; exec "$(command -v node)" "$0" "$@"
~function(){ ... }

This is now both an executable shell-script and a JavaScript program: meaning ./filename.js, sh filename.js, and node filename.js all work.

(Definitely a little bit of a strange usage, but effective nonetheless.)

Some explication, as requested:

  • Shell-scripts are evaluated line-by-line; and the exec command, when run, terminates the shell and replaces it's process with the resultant command. This means that to the shell, the program looks like this:

    #!/usr/bin/env sh
    ':' //; exec "$(command -v node)" "$0" "$@"
  • As long as no parameter expansion or aliasing is occurring in the word, any word in a shell-script can be wrapped in quotes without changing its' meaning; this means that ':' is equivalent to : (we've only wrapped it in quotes here to achieve the JavaScript semantics described below)

  • ... and as described above, the first command on the first line is a no-op (it translates to : //, or if you prefer to quote the words, ':' '//'. Notice that the // carries no special meaning here, as it does in JavaScript; it's just a meaningless word that's being thrown away.)

  • Finally, the second command on the first line (after the semicolon), is the real meat of the program: it's the exec call which replaces the shell-script being invoked, with a Node.js process invoked to evaluate the rest of the script.

  • Meanwhile, the first line, in JavaScript, parses as a string-literal (':'), and then a comment, which is deleted; thus, to JavaScript, the program looks like this:

    ~function(){ ... }

    Since the string-literal is on a line by itself, it is a no-op statement, and is thus stripped from the program; that means that the entire line is removed, leaving only your program-code (in this example, the function(){ ... } body.)

Post a json object to mvc controller with jquery and ajax

What am I doing incorrectly?

You have to convert html to javascript object, and then as a second step to json throug JSON.Stringify.

How can I receive a json object in the controller?


<script src=""></script>
<script src=""></script>

var obj = $("#form1").serializeJSON({ useIntKeysAsArrayIndex: true });
$.post("http://localhost:52161/Default/PostRawJson/", { json: JSON.stringify(obj) });

<form id="form1" method="post">
<input name="OrderDate" type="text" /><br />
<input name="Item[0][Id]" type="text" /><br />
<input name="Item[1][Id]" type="text" /><br />
<button id="btn" onclick="btnClick()">Button</button>


public void PostRawJson(string json)
    var order = System.Web.Helpers.Json.Decode(json);
    var orderDate = order.OrderDate;
    var secondOrderId = order.Item[1].Id;

Iterate Multi-Dimensional Array with Nested Foreach Statement

You can also use enumerators. Every array-type of any dimension supports the Array.GetEnumerator method. The only caveat is that you will have to deal with boxing/unboxing. However, the code you need to write will be quite trivial.

Here's the sample code:

class Program
    static void Main(string[] args)
        int[,] myArray = new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 } };
        var e = myArray.GetEnumerator();


        while (e.MoveNext())
            // this will output each number from 1 to 6. 


Android set bitmap to Imageview

    //decode base64 string to image
    imageBytes = Base64.decode(encodedImage, Base64.DEFAULT);
    Bitmap decodedImage = BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.length);

  //setImageBitmap is imp

CSS3 Spin Animation

HTML with font-awesome glyphicon.

<span class="fa fa-spinner spin"></span>


@-moz-keyframes spin {
    to { -moz-transform: rotate(360deg); }
@-webkit-keyframes spin {
    to { -webkit-transform: rotate(360deg); }
@keyframes spin {
    to {transform:rotate(360deg);}

.spin {
    animation: spin 1000ms linear infinite;

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

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

apksigner verify --print-certs my_app.apk

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

R apply function with multiple parameters

To further generalize @Alexander's example, outer is relevant in cases where a function must compute itself on each pair of vector values:



> outer(vars1, vars2, mult_one)
     [,1] [,2] [,3]
[1,]   10   20   30
[2,]   20   40   60
[3,]   30   60   90

Convert a Unicode string to a string in Python (containing extra symbols)

file contain unicode-esaped string

\"message\": \"\\u0410\\u0432\\u0442\\u043e\\u0437\\u0430\\u0446\\u0438\\u044f .....\",

for me

 f = open("56ad62-json.log", encoding="utf-8")

 {"log":\"message\": \"\\u0410\\u0432\\u0442\\u043e\\u0440\\u0438\\u0437\\u0430\\u0446\\u0438\\u044f \\u043f\\u043e\\u043b\\u044c\\u0437\\u043e\\u0432\\u0430\\u0442\\u0435\\u043b\\u044f\"}

# '{"log":"message": "??????????? ????????????"}\n'

How can I check whether a variable is defined in Node.js?

It sounds like you're doing property checking on an object! If you want to check a property exists (but can be values such as null or 0 in addition to truthy values), the in operator can make for some nice syntax.

var foo = { bar: 1234, baz: null };
console.log("bar in foo:", "bar" in foo); // true
console.log("baz in foo:", "baz" in foo); // true
console.log("otherProp in foo:", "otherProp" in foo) // false
console.log("__proto__ in foo:", "__proto__" in foo) // true

As you can see, the __proto__ property is going to be thrown here. This is true for all inherited properties. For further reading, I'd recommend the MDN page:

Python WindowsError: [Error 123] The filename, directory name, or volume label syntax is incorrect:

As it solved the problem, I put it as an answer.

Don't use single and double quotes, especially when you define a raw string with r in front of it.

The correct call is then

path = r"C:\Apps\CorVu\DATA\Reports\AlliD\Monthly Commission Reports\Output\pdcom1"


path = r'C:\Apps\CorVu\DATA\Reports\AlliD\Monthly Commission Reports\Output\pdcom1'

GIT clone repo across local file system in windows

I was successful in doing this using file://, but with one additional slash to denote an absolute path.

git clone file:///cygdrive/c/path/to/repository/

In my case I'm using Git on Cygwin for Windows, which you can see because of the /cygdrive/c part in my paths. With some tweaking to the path it should work with any git installation.

Adding a remote works the same way

git remote add remotename file:///cygdrive/c/path/to/repository/

Android: keep Service running when app is killed

All the answers seem correct so I'll go ahead and give a complete answer here.

Firstly, the easiest way to do what you are trying to do is launch a Broadcast in Android when the app is killed manually, and define a custom BroadcastReceiver to trigger a service restart following that.

Now lets jump into code.

Create your Service in

Note the onCreate() method, where we are starting a foreground service differently for Build versions greater than Android Oreo. This because of the strict notification policies introduced recently where we have to define our own notification channel to display them correctly.

The this.sendBroadcast(broadcastIntent); in the onDestroy() method is the statement which asynchronously sends a broadcast with the action name "restartservice". We'll be using this later as a trigger to restart our service.

Here we have defined a simple Timer task, which prints a counter value every 1 second in the Log while incrementing itself every time it prints.

public class YourService extends Service {
public int counter=0;

    public void onCreate() {
        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.O)
            startForeground(1, new Notification());

    private void startMyOwnForeground()
        String NOTIFICATION_CHANNEL_ID = "example.permanence";
        String channelName = "Background Service";
        NotificationChannel chan = new NotificationChannel(NOTIFICATION_CHANNEL_ID, channelName, NotificationManager.IMPORTANCE_NONE);
        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        assert manager != null;

        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
        Notification notification = notificationBuilder.setOngoing(true)
                .setContentTitle("App is running in background")
        startForeground(2, notification);

    public int onStartCommand(Intent intent, int flags, int startId) {
        super.onStartCommand(intent, flags, startId);
        return START_STICKY;

    public void onDestroy() {

        Intent broadcastIntent = new Intent();
        broadcastIntent.setClass(this, Restarter.class);

    private Timer timer;
    private TimerTask timerTask;
    public void startTimer() {
        timer = new Timer();
        timerTask = new TimerTask() {
            public void run() {
                Log.i("Count", "=========  "+ (counter++));
        timer.schedule(timerTask, 1000, 1000); //

    public void stoptimertask() {
        if (timer != null) {
            timer = null;

    public IBinder onBind(Intent intent) {
        return null;

Create a Broadcast Receiver to respond to your custom defined broadcasts in

The broadcast with the action name "restartservice" which you just defined in is now supposed to trigger a method which will restart your service. This is done using BroadcastReceiver in Android.

We override the built-in onRecieve() method in BroadcastReceiver to add the statement which will restart the service. The startService() will not work as intended in and above Android Oreo 8.1, as strict background policies will soon terminate the service after restart once the app is killed. Therefore we use the startForegroundService() for higher versions and show a continuous notification to keep the service running.

public class Restarter extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
        Log.i("Broadcast Listened", "Service tried to stop");
        Toast.makeText(context, "Service restarted", Toast.LENGTH_SHORT).show();

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            context.startForegroundService(new Intent(context, YourService.class));
        } else {
            context.startService(new Intent(context, YourService.class));

Define your to call the service on app start.

Here we define a separate isMyServiceRunning() method to check the current status of the background service. If the service is not running, we start it by using startService().

Since the app is already running in foreground, we need not launch the service as a foreground service to prevent itself from being terminated.

Note that in onDestroy() we are dedicatedly calling stopService(), so that our overridden method gets invoked. If this was not done, then the service would have ended automatically after app is killed without invoking our modified onDestroy() method in

public class MainActivity extends AppCompatActivity {
    Intent mServiceIntent;
    private YourService mYourService;

    protected void onCreate(Bundle savedInstanceState) {

        mYourService = new YourService();
        mServiceIntent = new Intent(this, mYourService.getClass());
        if (!isMyServiceRunning(mYourService.getClass())) {

    private boolean isMyServiceRunning(Class<?> serviceClass) {
        ActivityManager manager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        for (ActivityManager.RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
            if (serviceClass.getName().equals(service.service.getClassName())) {
                Log.i ("Service status", "Running");
                return true;
        Log.i ("Service status", "Not running");
        return false;

    protected void onDestroy() {
        Intent broadcastIntent = new Intent();
        broadcastIntent.setClass(this, Restarter.class);

Finally register them in your AndroidManifest.xml

All of the above three classes need to be separately registered in AndroidManifest.xml.

Note that we define an intent-filter with the action name as "restartservice" where the is registered as a receiver. This ensures that our custom BroadcastReciever is called whenever the system encounters a broadcast with the given action name.


            <action android:name="restartservice" />

    <activity android:name="MainActivity">
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />

        android:enabled="true" >

This should now restart your service again if the app was killed from the task-manager. This service will keep on running in background as long as the user doesn't Force Stop the app from Application Settings.

UPDATE: Kudos to Dr.jacky for pointing it out. The above mentioned way will only work if the onDestroy() of the service is called, which might not be the case certain times, which I was unaware of. Thanks.

jQuery UI - Close Dialog When Clicked Outside

This is the only method that worked for me for my NON-MODAL dialog

$(document).mousedown(function(e) {
    var clicked = $(; // get the element clicked
    if ('#dlg') || clicked.parents().is('#dlg') ||'.ui-dialog-titlebar')) {
        return; // click happened within the dialog, do nothing here
    } else { // click was outside the dialog, so close it

All credit goes to Axle
Click outside non-modal dialog to close

repaint() in Java

If you added JComponent to already visible Container, then you have call


for example

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class Main {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setSize(460, 500);
        frame.setTitle("Circles generator");

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {

        String input = JOptionPane.showInputDialog("Enter n:");
        CustomComponents0 component = new CustomComponents0();

    static class CustomComponents0 extends JLabel {

        private static final long serialVersionUID = 1L;

        public Dimension getMinimumSize() {
            return new Dimension(200, 100);

        public Dimension getPreferredSize() {
            return new Dimension(300, 200);

        public void paintComponent(Graphics g) {
            int margin = 10;
            Dimension dim = getSize();
            g.fillRect(margin, margin, dim.width - margin * 2, dim.height - margin * 2);

Build error: You must add a reference to System.Runtime

install Microsoft .NET Framework 4.6.1 Developer Pack and add this line of code in Web.config file

<compilation debug="true" targetFramework="4.5">
            <add assembly="System.Runtime, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>

Do not want scientific notation on plot axis

You can use the axis() command for that, eg :

x <- 1:100000
y <- 1:100000
marks <- c(0,20000,40000,60000,80000,100000)

gives :

enter image description here

EDIT : if you want to have all of them in the same format, you can use the solution of @Richie to get them :

x <- 1:100000
y <- 1:100000

Accessing a Shared File (UNC) From a Remote, Non-Trusted Domain With Credentials

Most SFTP servers support SCP as well which can be a lot easier to find libraries for. You could even just call an existing client from your code like pscp included with PuTTY.

If the type of file you're working with is something simple like a text or XML file, you could even go so far as to write your own client/server implementation to manipulate the file using something like .NET Remoting or web services.

AmazonS3 putObject with InputStream length example

Just passing the file object to the putobject method worked for me. If you are getting a stream, try writing it to a temp file before passing it on to S3.

amazonS3.putObject(bucketName, id,fileObject);

I am using Aws SDK v1.11.414

The answer at helped me

jquery get all input from specific form

Use HTML Form "elements" attribute:

$.each($("form").elements, function(){ 

Now it's not necessary to provide such names as "input, textarea, select ..." etc.

How to get file path in iPhone app

You need to add your tiles into your resource bundle. I mean add all those files to your project make sure to copy all files to project directory option checked.

Use child_process.execSync but keep output in console


 try {
    const cmd = 'git rev-parse --is-inside-work-tree';
 } catch (error) {
    console.log(`Status Code: ${error.status} with '${error.message}'`;


// nodejs
var execSync = require('child_process').execSync;

// typescript
const { execSync } = require("child_process");

 try {
    const cmd = 'git rev-parse --is-inside-work-tree';
 } catch (error) {
    error.status;  // 0 : successful exit, but here in exception it has to be greater than 0
    error.message; // Holds the message you typically want.
    error.stderr;  // Holds the stderr output. Use `.toString()`.
    error.stdout;  // Holds the stdout output. Use `.toString()`.

enter image description here

enter image description here

When command runs successful: enter image description here

No value accessor for form control

For UnitTest angular 2 with angular material you have to add MatSelectModule module in imports section.

import { MatSelectModule } from '@angular/material';

beforeEach(async(() => {
      declarations: [ CreateUserComponent ],
      imports : [ReactiveFormsModule,        

      providers: [.........]

Get the correct week number of a given date

If you don't have .NET 5.0, extend the DateTime class to include week number.

public static class Extension {
    public static int Week(this DateTime date) {
        var day = (int)CultureInfo.CurrentCulture.Calendar.GetDayOfWeek(date);
        return CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(date.AddDays(4 - (day == 0 ? 7 : day)), CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

How to resolve ORA-011033: ORACLE initialization or shutdown in progress

This error can also occur in the normal situation when a database is starting or stopping. Normally on startup you can wait until the startup completes, then connect as usual. If the error persists, the service (on a Windows box) may be started without the database being started. This may be due to startup issues, or because the service is not configured to automatically start the database. In this case you will have to connect as sysdba and physically start the database using the "startup" command.

405 method not allowed Web API

This does not answer your specific question, but when I had the same problem I ended up here and I figured that more people might do the same.

The problem I had was that I had indeliberately declared my Get method as static. I missed this an entire forenoon, and it caused no warnings from attributes or similar.


public class EchoController : ApiController
    public static string Get()
        return string.Empty;


public class EchoController : ApiController
    public string Get()
        return string.Empty;

How to limit the number of dropzone.js files uploaded?

I thought that the most intuitive single file upload process was to replace the previous file upon a new entry.

    url: '/cart?upload-engraving=true',
    maxFiles: 1,
    maxfilesexceeded: function(file) {

How can I fix MySQL error #1064?

For my case, I was trying to execute procedure code in MySQL, and due to some issue with server in which Server can't figure out where to end the statement I was getting Error Code 1064. So I wrapped the procedure with custom DELIMITER and it worked fine.

For example, Before it was:

CREATE PROCEDURE `getStats` (param_id INT, param_offset INT, param_startDate datetime, param_endDate datetime)
    /*Procedure Code Here*/

After putting DELIMITER it was like this:

CREATE PROCEDURE `getStats` (param_id INT, param_offset INT, param_startDate datetime, param_endDate datetime)
    /*Procedure Code Here*/

Count Rows in Doctrine QueryBuilder

To count items after some number of items (offset), $qb->setFirstResults() cannot be applied in this case, as it works not as a condition of query, but as an offset of query result for a range of items selected (i. e. setFirstResult cannot be used togather with COUNT at all). So to count items, which are left I simply did the following:

   //in repository class:
   $count = $qb->select('count(')
      ->from('Products', 'p')

    return $count;

    //in controller class:
    $count = $this->em->getRepository('RepositoryBundle')->...

    return $count-$offset;

Anybody knows more clean way to do it?

Why can I not switch branches?

If you don't care about the changes that git says are outstanding, then you can do a force checkout.

git checkout -f {{insert your branch name here}}

How to set JVM parameters for Junit Unit Tests?

You can use systemPropertyVariables (java.protocol.handler.pkgs is your JVM argument name):


Stop handler.postDelayed()

this may be old, but for those looking for answer you can use this...

public void stopHandler() {


PHP - iterate on string characters

// Unicode Codepoint Escape Syntax in PHP 7.0
$str = "cat!\u{1F431}";

// IIFE (Immediately Invoked Function Expression) in PHP 7.0
$gen = (function(string $str) {
    for ($i = 0, $len = mb_strlen($str); $i < $len; ++$i) {
        yield mb_substr($str, $i, 1);

    true === $gen instanceof Traversable,
    // PHP 7.1
    true === is_iterable($gen)

foreach ($gen as $char) {
    echo $char, PHP_EOL;

MySQL select with CONCAT condition


SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
  FROM users 
WHERE CONCAT(firstname, ' ', lastname) = "Bob Michael Jones"

Your alias firstlast is not available in the where clause of the query unless you do the query as a sub-select.

MongoDB Show all contents from all collections

step 1: Enter into the MongoDB shell.


step 2: for the display all the databases.

show dbs;

step 3: for a select database :

use 'databases_name'

step 4: for statistics of your database.


step 5: listing out all the collections(tables).

show collections

step 6:print the data from a particular collection.


Introducing FOREIGN KEY constraint may cause cycles or multiple cascade paths - why?

Because Stage is required, all one-to-many relationships where Stage is involved will have cascading delete enabled by default. It means, if you delete a Stage entity

  • the delete will cascade directly to Side
  • the delete will cascade directly to Card and because Card and Side have a required one-to-many relationship with cascading delete enabled by default again it will then cascade from Card to Side

So, you have two cascading delete paths from Stage to Side - which causes the exception.

You must either make the Stage optional in at least one of the entities (i.e. remove the [Required] attribute from the Stage properties) or disable cascading delete with Fluent API (not possible with data annotations):

    .HasRequired(c => c.Stage)

    .HasRequired(s => s.Stage)

How to deal with ModalDialog using selenium webdriver?

I have tried it, it works for you.

String mainWinHander = webDriver.getWindowHandle();

// code for clicking button to open new window is ommited

//Now the window opened. So here reture the handle with size = 2
Set<String> handles = webDriver.getWindowHandles();

for(String handle : handles)
        // Here will block for ever. No exception and timeout!
        WebDriver popup = webDriver.switchTo().window(handle);
        // do something with popup

How to cast an object in Objective-C

Casting for inclusion is just as important as casting for exclusion for a C++ programmer. Type casting is not the same as with RTTI in the sense that you can cast an object to any type and the resulting pointer will not be nil.

Getting indices of True values in a boolean list

You can use filter for it:

filter(lambda x: self.states[x], range(len(self.states)))

The range here enumerates elements of your list and since we want only those where self.states is True, we are applying a filter based on this condition.

For Python > 3.0:

list(filter(lambda x: self.states[x], range(len(self.states))))

What is the most efficient way to loop through dataframes with pandas?

As @joris pointed out, iterrows is much slower than itertuples and itertuples is approximately 100 times fater than iterrows, and I tested speed of both methods in a DataFrame with 5027505 records the result is for iterrows, it is 1200it/s, and itertuples is 120000it/s.

If you use itertuples, note that every element in the for loop is a namedtuple, so to get the value in each column, you can refer to the following example code

>>> df = pd.DataFrame({'col1': [1, 2], 'col2': [0.1, 0.2]},
                      index=['a', 'b'])
>>> df
   col1  col2
a     1   0.1
b     2   0.2
>>> for row in df.itertuples():
...     print(row.col1, row.col2)
1, 0.1
2, 0.2

Plugin with id '' not found

You can find the correct dependencies here apply changes to app.gradle and project.gradle and tell me about this, greetings!

Your apply plugin: '' in app.gradle looks like this:

apply plugin: ''

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.2"

    defaultConfig {
        applicationId "com.example.personal.numbermania"
        minSdkVersion 10
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"

        multiDexEnabled true

    dexOptions {
        incremental true
        javaMaxHeapSize "4g" //Here stablished how many cores you want to use your android studi 4g = 4 cores

    buildTypes {
                    debuggable true
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), ''

dependencies {
        compile fileTree(include: ['*.jar'], dir: 'libs')
        testCompile 'junit:junit:4.12'
        compile ''
        compile ''
        compile ''
        compile ''
        compile ''

apply plugin: ''

Add classpath to the project's gradle:

classpath ''

Google play services library on SDK Manager:

enter image description here

What is the regex pattern for datetime (2008-09-01 12:35:45 )?

A simple version that will work for the format mentioned, but not all the others as per @Espos:

(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}) 

ASP.NET: Session.SessionID changes between requests

There is another, more insidious reason, why this may occur even when the Session object has been initialized as demonstrated by Cladudio.

In the Web.config, if there is an <httpCookies> entry that is set to requireSSL="true" but you are not actually using HTTPS: for a specific request, then the session cookie is not sent (or maybe not returned, I'm not sure which) which means that you end up with a brand new session for each request.

I found this one the hard way, spending several hours going back and forth between several commits in my source control, until I found what specific change had broken my application.

Error checking for NULL in VBScript

I will just add a blank ("") to the end of the variable and do the comparison. Something like below should work even when that variable is null. You can also trim the variable just in case of spaces.

If provider & "" <> "" Then 
    url = url & "&provider=" & provider 
End if

How do I download a file using VBA (without Internet Explorer)

A modified version of above solution to make it more dynamic.

Private Declare Function URLDownloadToFile Lib "urlmon" Alias "URLDownloadToFileA" (ByVal pCaller As Long, ByVal szURL As String, ByVal szFileName As String, ByVal dwReserved As Long, ByVal lpfnCB As Long) As Long

Public Function DownloadFileA(ByVal URL As String, ByVal DownloadPath As String) As Boolean
    On Error GoTo Failed
    DownloadFileA = False
    'As directory must exist, this is a check
    If CreateObject("Scripting.FileSystemObject").FolderExists(CreateObject("Scripting.FileSystemObject").GetParentFolderName(DownloadPath)) = False Then Exit Function
    Dim returnValue As Long
    returnValue = URLDownloadToFile(0, URL, DownloadPath, 0, 0)
    'If return value is 0 and the file exist, then it is considered as downloaded correctly
    DownloadFileA = (returnValue = 0) And (Len(Dir(DownloadPath)) > 0)
    Exit Function

End Function

Catching exceptions from Guzzle

I want to update the answer for exception handling in Psr-7 Guzzle, Guzzle7 and HTTPClient(expressive, minimal API around the Guzzle HTTP client provided by laravel).

Guzzle7 (same works for Guzzle 6 as well)

Using RequestException, RequestException catches any exception that can be thrown while transferring requests.

  $client = new \GuzzleHttp\Client(['headers' => ['Authorization' => 'Bearer ' . $token]]);
  $guzzleResponse = $client->get('/foobar');
  // or can use
  // $guzzleResponse = $client->request('GET', '/foobar')
    if ($guzzleResponse->getStatusCode() == 200) {
         $response = json_decode($guzzleResponse->getBody(),true);
         //perform your action with $response 
catch(\GuzzleHttp\Exception\RequestException $e){
   // you can catch here 400 response errors and 500 response errors
   // You can either use logs here use Illuminate\Support\Facades\Log;
   $error['error'] = $e->getMessage();
   $error['request'] = $e->getRequest();
       if ($e->getResponse()->getStatusCode() == '400'){
           $error['response'] = $e->getResponse(); 
   Log::error('Error occurred in get request.', ['error' => $error]);
}catch(Exception $e){
   //other errors 

Psr7 Guzzle

use GuzzleHttp\Psr7;
use GuzzleHttp\Exception\RequestException;

try {
    $client->request('GET', '/foo');
} catch (RequestException $e) {
    $error['error'] = $e->getMessage();
    $error['request'] = Psr7\Message::toString($e->getRequest());
    if ($e->hasResponse()) {
        $error['response'] = Psr7\Message::toString($e->getResponse());
    Log::error('Error occurred in get request.', ['error' => $error]);

For HTTPClient

use Illuminate\Support\Facades\Http;
    $response = Http::get('');
        $reply = $response->json();
            //catch all 400 exceptions
            Log::debug('client Error occurred in get request.');
            //catch all 500 exceptions
            Log::debug('server Error occurred in get request.');
 }catch(Exception $e){
     //catch the exception here

How can I list all cookies for the current page with Javascript?

function listCookies() {
    let cookies = document.cookie.split(';'), n) => console.log(`${n}:`, decodeURIComponent(cookie)))

function findCookie(e) {
  let cookies = document.cookie.split(';'), n) => cookie.includes(e) && console.log(decodeURIComponent(cookie), n))

This is specifically for the window you're in. Tried to keep it clean and concise.

Why can't overriding methods throw exceptions broader than the overridden method?

Let us take an interview Question. There is a method that throws NullPointerException in the superclass. Can we override it with a method that throws RuntimeException?

To answer this question, let us know what is an Unchecked and Checked exception.

  1. Checked exceptions must be explicitly caught or propagated as described in Basic try-catch-finally Exception Handling. Unchecked exceptions do not have this requirement. They don't have to be caught or declared thrown.

  2. Checked exceptions in Java extend the java.lang.Exception class. Unchecked exceptions extend the java.lang.RuntimeException.

public class NullPointerException extends RuntimeException

Unchecked exceptions extend the java.lang.RuntimeException. Thst's why NullPointerException is an Uncheked exception.

Let's take an example: Example 1 :

    public class Parent {
       public void name()  throws NullPointerException {
           System.out.println(" this is parent");

public class Child  extends Parent{
     public  void name() throws RuntimeException{
             System.out.println(" child ");

     public static void main(String[] args) {
        Parent parent  = new Child();;// output => child

The program will compile successfully. Example 2:

    public class Parent {
       public void name()  throws RuntimeException {
           System.out.println(" this is parent");

public class Child  extends Parent{
     public  void name() throws  NullPointerException {
             System.out.println(" child ");

     public static void main(String[] args) {
        Parent parent  = new Child();;// output => child

The program will also compile successfully. Therefore it is evident, that nothing happens in case of Unchecked exceptions. Now, let's take a look what happens in case of Checked exceptions. Example 3: When base class and child class both throws a checked exception

    public class Parent {
       public void name()  throws IOException {
           System.out.println(" this is parent");
public class Child  extends Parent{
     public  void name() throws IOException{
             System.out.println(" child ");

     public static void main(String[] args) {
        Parent parent  = new Child();

        try {
  ;// output=> child
        }catch( Exception e) {


The program will compile successfully. Example 4: When child class method is throwing border checked exception compared to the same method of base class.


public class Parent {
       public void name()  throws IOException {
           System.out.println(" this is parent");
public class Child  extends Parent{
     public  void name() throws Exception{ // broader exception
             System.out.println(" child ");

     public static void main(String[] args) {
        Parent parent  = new Child();

        try {
  ;//output=> Compilation failure
        }catch( Exception e) {


The program will fail to compile. So, we have to be careful when we are using Checked exceptions.

How do I import modules or install extensions in PostgreSQL 9.1+?

The extensions available for each version of Postgresql vary. An easy way to check which extensions are available is, as has been already mentioned:

SELECT * FROM pg_available_extensions;

If the extension that you are looking for is available, you can install it using:

CREATE EXTENSION 'extensionName';

or if you want to drop it use:

DROP EXTENSION 'extensionName';

With psql you can additionally check if the extension has been successfully installed using \dx, and find more details about the extension using \dx+ extensioName. It returns additional information about the extension, like which packages are used with it.

If the extension is not available in your Postgres version, then you need to download the necessary binary files and libraries and locate it them at /usr/share/conrib

_tkinter.TclError: no display name and no $DISPLAY environment variable

Another solution is to install Xvfb, and export your display to it. ie:

exec Xvfb $disp -screen $screen $geom 2>/tmp/Xvfb.log &


$ export DISPLAY=:8

$ ./

XAMPP keeps showing Dashboard/Welcome Page instead of the Configuration Page

The old version, but the desired function will be sufficient.

Uninstall version 5.6.11 and downgrade to version 5.6.8.

$.ajax - dataType

  • contentType is the HTTP header sent to the server, specifying a particular format.
    Example: I'm sending JSON or XML
  • dataType is you telling jQuery what kind of response to expect.
    Expecting JSON, or XML, or HTML, etc. The default is for jQuery to try and figure it out.

The $.ajax() documentation has full descriptions of these as well.

In your particular case, the first is asking for the response to be in UTF-8, the second doesn't care. Also the first is treating the response as a JavaScript object, the second is going to treat it as a string.

So the first would be:

success: function(data) {
  // get data, e.g. data.title;

The second:

success: function(data) {
  alert("Here's lots of data, just a string: " + data);

Convert to absolute value in Objective-C

You can use this function to get the absolute value:

+(NSNumber *)absoluteValue:(NSNumber *)input {
  return [NSNumber numberWithDouble:fabs([input doubleValue])];

Programmatically set left drawable in a TextView

static private Drawable **scaleDrawable**(Drawable drawable, int width, int height) {

    int wi = drawable.getIntrinsicWidth();
    int hi = drawable.getIntrinsicHeight();
    int dimDiff = Math.abs(wi - width) - Math.abs(hi - height);
    float scale = (dimDiff > 0) ? width / (float)wi : height /
    Rect bounds = new Rect(0, 0, (int)(scale * wi), (int)(scale * hi));
    return drawable;

How to show full height background image?

This worked for me (though it's for reactjs & tachyons used as inline CSS)

<div className="pa2 cf vh-100-ns" style={{backgroundImage: `url(${a6})`}}> 

This takes in css as height: 100vh

How do I force "git pull" to overwrite local files?

I read through all the answers but I was looking for a single command to do this. Here is what I did. Added a git alias to .gitconfig

      fp = "!f(){ git fetch ${1} ${2} && git reset --hard ${1}/${2};};f"

Run your command as

git fp origin master

equivalent to

git fetch origin master
git reset --hard origin/master

Check if all elements in a list are identical

Or use diff method of numpy:

import numpy as np
def allthesame(l):
    return np.all(np.diff(l)==0)

And to call:




What does enumerate() mean?

The enumerate() function adds a counter to an iterable.

So for each element in cursor, a tuple is produced with (counter, element); the for loop binds that to row_number and row, respectively.


>>> elements = ('foo', 'bar', 'baz')
>>> for elem in elements:
...     print elem
>>> for count, elem in enumerate(elements):
...     print count, elem
0 foo
1 bar
2 baz

By default, enumerate() starts counting at 0 but if you give it a second integer argument, it'll start from that number instead:

>>> for count, elem in enumerate(elements, 42):
...     print count, elem
42 foo
43 bar
44 baz

If you were to re-implement enumerate() in Python, here are two ways of achieving that; one using itertools.count() to do the counting, the other manually counting in a generator function:

from itertools import count

def enumerate(it, start=0):
    # return an iterator that adds a counter to each element of it
    return zip(count(start), it)


def enumerate(it, start=0):
    count = start
    for elem in it:
        yield (count, elem)
        count += 1

The actual implementation in C is closer to the latter, with optimisations to reuse a single tuple object for the common for i, ... unpacking case and using a standard C integer value for the counter until the counter becomes too large to avoid using a Python integer object (which is unbounded).

How do I trim whitespace?

    something = "\t  please_     \t remove_  all_    \n\n\n\nwhitespaces\n\t  "

    something = "".join(something.split())



Adding Le Droid's comment to the answer. To separate with a space:

    something = "\t  please     \t remove  all   extra \n\n\n\nwhitespaces\n\t  "
    something = " ".join(something.split())


please remove all extra whitespaces

How to force remounting on React components?

Change the key of the component.

<Component key="1" />
<Component key="2" />

Component will be unmounted and a new instance of Component will be mounted since the key has changed.

edit: Documented on You Probably Don't Need Derived State:

When a key changes, React will create a new component instance rather than update the current one. Keys are usually used for dynamic lists but are also useful here.

Get IFrame's document, from JavaScript in main document

In case you get a cross-domain error:

If you have control over the content of the iframe - that is, if it is merely loaded in a cross-origin setup such as on Amazon Mechanical Turk - you can circumvent this problem with the <body onload='my_func(my_arg)'> attribute for the inner html.

For example, for the inner html, use the this html parameter (yes - this is defined and it refers to the parent window of the inner body element):

<body onload='changeForm(this)'>

In the inner html :

    function changeForm(window) {
        console.log('inner window loaded: do whatever you want with the inner html');
        window.document.getElementById('mturk_form').style.display = 'none';

In AVD emulator how to see sdcard folder? and Install apk to AVD?

//in linux

// in your home folder .android hidden folder is there go to that there you can find the avd folder open that and check your avd name that you created open that and you can see the sdcard.img that is your sdcard file.

//To install apk in linux

$adb install ./yourfolder/myapkfile.apk

Is it possible to have placeholders in strings.xml for runtime values?

In your string file use this

<string name="redeem_point"> You currently have %s points(%s points = 1 %s)</string>

And in your code use as accordingly

coinsTextTV.setText(String.format(getContext().getString(R.string.redeem_point), rewardPoints.getReward_points()
                        , rewardPoints.getConversion_rate(), getString(;

How to increase Neo4j's maximum file open limit (ulimit) in Ubuntu?

tl;dr set both the soft and hard limits

I'm sure it's working as intended but I'll add it here just in case. For completeness the limit is set here (see below for syntax): /etc/security/limits.conf

some_user       soft    nofile          60000
some_user       hard    nofile          60000

and activated with the following in /etc/pam.d/common-session:

session required

If you set only the hard limit, ulimit -a will show the default (1024): If you set only the soft the limit ulimit -a will show (4096)

If you set them both ulimit -a will show the soft limit (up to the hard limit of course)

How can I find the version of php that is running on a distinct domain name?

I use redbot, a great tool to see php version, but also many other useful infos like headers, encoding, keepalive and many more, try it on

I loveit !

I also upvote Neil answer : curl -I

How to fit a smooth curve to my data in R?

I like loess() a lot for smoothing:

x <- 1:10
y <- c(2,4,6,8,7,12,14,16,18,20)
lo <- loess(y~x)
lines(predict(lo), col='red', lwd=2)

Venables and Ripley's MASS book has an entire section on smoothing that also covers splines and polynomials -- but loess() is just about everybody's favourite.

Form Submit jQuery does not work

If you are doing form validation such as

type="submit" onsubmit="return validateForm(this)"

validateForm = function(form) {
if ($('input#company').val() === "" || $('input#company').val() === "Company")  {
        $('input#company').val("Company").css('color','red'); finalReturn = false; 
        $('input#company').on('mouseover',(function() { 
            finalReturn = true; 

    return finalReturn; 

Double check you are returning true. This seems simple but I had

var finalReturn = false;

When the form was correct it was not being corrected by validateForm and so not being submitted as finalReturn was still initialized to false instead of true. By the way, above code works nicely with address, city, state and so on.

How to install python modules without root access?

If you have to use a distutils script, there are some commandline options for forcing an installation destination. See If this problem repeats, you can setup a distutils configuration file, see

Setting the PYTHONPATH variable is described in tihos post.

What is Hash and Range Primary Key?

"Hash and Range Primary Key" means that a single row in DynamoDB has a unique primary key made up of both the hash and the range key. For example with a hash key of X and range key of Y, your primary key is effectively XY. You can also have multiple range keys for the same hash key but the combination must be unique, like XZ and XA. Let's use their examples for each type of table:

Hash Primary Key – The primary key is made of one attribute, a hash attribute. For example, a ProductCatalog table can have ProductID as its primary key. DynamoDB builds an unordered hash index on this primary key attribute.

This means that every row is keyed off of this value. Every row in DynamoDB will have a required, unique value for this attribute. Unordered hash index means what is says - the data is not ordered and you are not given any guarantees into how the data is stored. You won't be able to make queries on an unordered index such as Get me all rows that have a ProductID greater than X. You write and fetch items based on the hash key. For example, Get me the row from that table that has ProductID X. You are making a query against an unordered index so your gets against it are basically key-value lookups, are very fast, and use very little throughput.

Hash and Range Primary Key – The primary key is made of two attributes. The first attribute is the hash attribute and the second attribute is the range attribute. For example, the forum Thread table can have ForumName and Subject as its primary key, where ForumName is the hash attribute and Subject is the range attribute. DynamoDB builds an unordered hash index on the hash attribute and a sorted range index on the range attribute.

This means that every row's primary key is the combination of the hash and range key. You can make direct gets on single rows if you have both the hash and range key, or you can make a query against the sorted range index. For example, get Get me all rows from the table with Hash key X that have range keys greater than Y, or other queries to that affect. They have better performance and less capacity usage compared to Scans and Queries against fields that are not indexed. From their documentation:

Query results are always sorted by the range key. If the data type of the range key is Number, the results are returned in numeric order; otherwise, the results are returned in order of ASCII character code values. By default, the sort order is ascending. To reverse the order, set the ScanIndexForward parameter to false

I probably missed some things as I typed this out and I only scratched the surface. There are a lot more aspects to take into consideration when working with DynamoDB tables (throughput, consistency, capacity, other indices, key distribution, etc.). You should take a look at the sample tables and data page for examples.

Default background color of SVG root element

Let me report a very simple solution I found, that is not written in previous answers. I also wanted to set background in an SVG, but I also want that this works in a standalone SVG file.

Well, this solution is really simple, in fact SVG supports style tags, so you can do something like

<svg xmlns="" width="50" height="50">
  <style>svg { background-color: red; }</style>

Working around MySQL error "Deadlock found when trying to get lock; try restarting transaction"

The answer is correct, however the perl documentation on how to handle deadlocks is a bit sparse and perhaps confusing with PrintError, RaiseError and HandleError options. It seems that rather than going with HandleError, use on Print and Raise and then use something like Try:Tiny to wrap your code and check for errors. The below code gives an example where the db code is inside a while loop that will re-execute an errored sql statement every 3 seconds. The catch block gets $_ which is the specific err message. I pass this to a handler function "dbi_err_handler" which checks $_ against a host of errors and returns 1 if the code should continue (thereby breaking the loop) or 0 if its a deadlock and should be retried...

$sth = $dbh->prepare($strsql);
my $db_res=0;
       print "caught $_ in insertion to hd_item_upc for upc $upc\n";
       if($db_res==0){sleep 3;}

dbi_err_handler should have at least the following:

sub dbi_err_handler
    my($message) = @_;
    if($message=~ m/DBD::mysql::st execute failed: Deadlock found when trying to get lock; try restarting transaction/)
       $retval=0; # we'll check this value and sleep/re-execute if necessary
    return $retval;

You should include other errors you wish to handle and set $retval depending on whether you'd like to re-execute or continue..

Hope this helps someone -

DateTime.ToString() format that can be used in a filename or extension?

The below list of time format specifiers most commonly used.,

dd -- day of the month, from 01 through 31.

MM -- month, from 01 through 12.

yyyy -- year as a four-digit number.

hh -- hour, using a 12-hour clock from 01 to 12.

mm -- minute, from 00 through 59.

ss -- second, from 00 through 59.

HH -- hour, using a 24-hour clock from 00 to 23.

tt -- AM/PM designator.

Using the above you will be able to form a unique name to your file name.

Here i have provided example

string fileName = "fileName_" + DateTime.Now.ToString("MM-dd-yyyy_hh-mm-ss-tt") + ".pdf";


If you don't prefer to use symbols you can try this also.,

string fileName = "fileName_" + DateTime.Now.ToString("MMddyyyyhhmmsstt") + ".pdf";

Hope this helps to someone now or in future. :)

Git log out user from command line

I was not able to clone a repository due to have logged on with other credentials.

To switch to another user, I >>desperate<< did:

git config --global --unset
git config --global --unset
git config --global --unset credential.helper

after, instead using ssh link, I used HTTPS link. It asked for credentials and it worked fine FOR ME!

'python3' is not recognized as an internal or external command, operable program or batch file

There is no python3.exe file, that is why it fails.




py is just a launcher for python.exe. If you have more than one python versions installed on your machine (2.x, 3.x) you can specify what version of python to launch by

py -2 or py -3

Optional Parameters in Go?

Go does not have optional parameters nor does it support method overloading:

Method dispatch is simplified if it doesn't need to do type matching as well. Experience with other languages told us that having a variety of methods with the same name but different signatures was occasionally useful but that it could also be confusing and fragile in practice. Matching only by name and requiring consistency in the types was a major simplifying decision in Go's type system.

css3 text-shadow in IE9

I was looking for a cross-browser text-stroke solution that works when overlaid on background images. think I have a solution for this that doesn't involve extra mark-up, js and works in IE7-9 (I haven't tested 6), and doesn't cause aliasing problems.

This is a combination of using CSS3 text-shadow, which has good support except IE (, then using a combination of filters for IE. CSS3 text-stroke support is poor at the moment.

IE Filters

The glow filter ( looks terrible, so I didn't use that.

David Hewitt's answer involved adding dropshadow filters in a combination of directions. ClearType is then removed unfortunately so we end up with badly aliased text.

I then combined some of the elements suggested on useragentman with the dropshadow filters.

Putting it together

This example would be black text with a white stroke. I'm using conditional html classes by the way to target IE (

#myelement {
    color: #000000;
    -1px -1px 0 #ffffff,  
    1px -1px 0 #ffffff,
    -1px 1px 0 #ffffff,
    1px 1px 0 #ffffff;

html.ie7 #myelement,
html.ie8 #myelement,
html.ie9 #myelement {
    background-color: white;
    filter: progid:DXImageTransform.Microsoft.Chroma(color='white') progid:DXImageTransform.Microsoft.Alpha(opacity=100) progid:DXImageTransform.Microsoft.dropshadow(color=#ffffff,offX=1,offY=1) progid:DXImageTransform.Microsoft.dropshadow(color=#ffffff,offX=-1,offY=1) progid:DXImageTransform.Microsoft.dropshadow(color=#ffffff,offX=1,offY=-1) progid:DXImageTransform.Microsoft.dropshadow(color=#ffffff,offX=-1,offY=-1);
    zoom: 1;

Enable IIS7 gzip

under windows 2012 r2 it can be found here:

enter image description here

Determining complexity for recursive functions (Big O notation)

We can prove it mathematically which is something I was missing in the above answers.

It can dramatically help you understand how to calculate any method. I recommend reading it from top to bottom to fully understand how to do it:

  1. T(n) = T(n-1) + 1 It means that the time it takes for the method to finish is equal to the same method but with n-1 which is T(n-1) and we now add + 1 because it's the time it takes for the general operations to be completed (except T(n-1)). Now, we are going to find T(n-1) as follow: T(n-1) = T(n-1-1) + 1. It looks like we can now form a function that can give us some sort of repetition so we can fully understand. We will place the right side of T(n-1) = ... instead of T(n-1) inside the method T(n) = ... which will give us: T(n) = T(n-1-1) + 1 + 1 which is T(n) = T(n-2) + 2 or in other words we need to find our missing k: T(n) = T(n-k) + k. The next step is to take n-k and claim that n-k = 1 because at the end of the recursion it will take exactly O(1) when n<=0. From this simple equation we now know that k = n - 1. Let's place k in our final method: T(n) = T(n-k) + k which will give us: T(n) = 1 + n - 1 which is exactly n or O(n).
  2. Is the same as 1. You can test it your self and see that you get O(n).
  3. T(n) = T(n/5) + 1 as before, the time for this method to finish equals to the time the same method but with n/5 which is why it is bounded to T(n/5). Let's find T(n/5) like in 1: T(n/5) = T(n/5/5) + 1 which is T(n/5) = T(n/5^2) + 1. Let's place T(n/5) inside T(n) for the final calculation: T(n) = T(n/5^k) + k. Again as before, n/5^k = 1 which is n = 5^k which is exactly as asking what in power of 5, will give us n, the answer is log5n = k (log of base 5). Let's place our findings in T(n) = T(n/5^k) + k as follow: T(n) = 1 + logn which is O(logn)
  4. T(n) = 2T(n-1) + 1 what we have here is basically the same as before but this time we are invoking the method recursively 2 times thus we multiple it by 2. Let's find T(n-1) = 2T(n-1-1) + 1 which is T(n-1) = 2T(n-2) + 1. Our next place as before, let's place our finding: T(n) = 2(2T(n-2)) + 1 + 1 which is T(n) = 2^2T(n-2) + 2 that gives us T(n) = 2^kT(n-k) + k. Let's find k by claiming that n-k = 1 which is k = n - 1. Let's place k as follow: T(n) = 2^(n-1) + n - 1 which is roughly O(2^n)
  5. T(n) = T(n-5) + n + 1 It's almost the same as 4 but now we add n because we have one for loop. Let's find T(n-5) = T(n-5-5) + n + 1 which is T(n-5) = T(n - 2*5) + n + 1. Let's place it: T(n) = T(n-2*5) + n + n + 1 + 1) which is T(n) = T(n-2*5) + 2n + 2) and for the k: T(n) = T(n-k*5) + kn + k) again: n-5k = 1 which is n = 5k + 1 that is roughly n = k. This will give us: T(n) = T(0) + n^2 + n which is roughly O(n^2).

I now recommend reading the rest of the answers which now, will give you a better perspective. Good luck winning those big O's :)

TypeError: 'dict' object is not callable

strikes  = [number_map[int(x)] for x in input_str.split()]

Use square brackets to explore dictionaries.

How to cache data in a MVC application

AppFabric Caching is distributed and an in-memory caching technic that stores data in key-value pairs using physical memory across multiple servers. AppFabric provides performance and scalability improvements for .NET Framework applications. Concepts and Architecture

Efficiently getting all divisors of a given number

int result_num;
bool flag;

cout << "Number          Divisors\n";

for (int number = 1; number <= 35; number++)
    flag = false;
    cout << setw(3) << number << setw(14);

    for (int i = 1; i <= number; i++) 
        result_num = number % i;

        if (result_num == 0 && flag == true)
            cout << "," << i;

        if (result_num == 0 && flag == false)
            cout << i;

        flag = true;

    cout << endl;   
cout << "Press enter to continue.....";
return 0;

Disable/Enable button in Excel/VBA

too good !!! it's working and resolved my one day old problem easily

Dim b1 As Button

Set b1 = ActiveSheet.Buttons("Button 1")

b1.Enabled = False

Case-insensitive search in Rails model

An alternative can be

c = Product.find_by("LOWER(name)= ?", name.downcase)

android lollipop toolbar: how to hide/show the toolbar while scrolling?





what is <meta charset="utf-8">?

That meta tag basically specifies which character set a website is written with.

Here is a definition of UTF-8:

UTF-8 (U from Universal Character Set + Transformation Format—8-bit) is a character encoding capable of encoding all possible characters (called code points) in Unicode. The encoding is variable-length and uses 8-bit code units.

Is there any option to limit mongodb memory usage?

Not really, there are a couple of tricks to limit memory, like on Windows you can use the Windows System Resource Manager (WSRM), but generally Mongo works best on a dedicated server when it's free to use memory without much contention with other systems.

Although the operating system will try to allocate memory to other processes as they need it, in practice this can lead to performance issues if other systems have high memory requirements too.

If you really need to limit memory, and only have a single server, then your best bet is virtualization.

How do I download NLTK data?

Install Pip: run in terminal : sudo easy_install pip

Install Numpy (optional): run : sudo pip install -U numpy

Install NLTK: run : sudo pip install -U nltk

Test installation: run: python

then type : import nltk

To download the corpus

run : python -m nltk.downloader all

How to print React component on click of a button?

If you're looking to print specific data that you already have access to, whether it's from a Store, AJAX, or available elsewhere, you can leverage my library react-print.

It makes creating print templates much easier (assuming you already have a dependency on react). You just need to tag your HTML appropriately.

This ID should be added higher up in your actual DOM tree to exclude everything except the "print mount" below.

<div id="react-no-print"> 

This is where your react-print component will mount and wrap your template that you create:

<div id="print-mount"></div>

An example looks something like this:

var PrintTemplate = require('react-print');
var ReactDOM = require('react-dom');
var React = require('react');

var MyTemplate = React.createClass({
    render() {
        return (
                <p>Your custom</p>
                <span>print stuff goes</span>

ReactDOM.render(<MyTemplate/>, document.getElementById('print-mount'));

It's worth noting that you can create new or utilize existing child components inside of your template, and everything should render fine for printing.

Using XAMPP, how do I swap out PHP 5.3 for PHP 5.2?

Thanks for the answer. I just got this working on Windows XP, with a few modifications. Here are my steps.

  1. Download and install latest xampp to G:\xampp. As of 2010/03/12, this is 1.7.3.
  2. Download the zip of, which is the latest xampp distro without php 5.3. Extract somewhere, e.g. G:\xampp-win32-1.7.0\
  3. Remove directory G:\xampp\php
  4. Remove G:\xampp\apache\modules\php5apache2_2.dll and php5apache2_2_filter.dll
  5. Copy G:\xampp-win32-1.7.0\xampp\php to G:\xampp\php.
  6. Copy G:\xampp-win32-1.7.0\xampp\apache\bin\php* to G:\xampp\apache\bin
  7. Edit G:\xampp\apache\conf\extra\httpd-xampp.conf.
    • Immediately after the line, <IfModule alias_module> add the lines


<IfModule mime_module>
  LoadModule php5_module "/xampp/apache/bin/php5apache2_2.dll"
  AddType application/x-httpd-php-source .phps
  AddType application/x-httpd-php .php .php5 .php4 .php3 .phtml .phpt
    <Directory "/xampp/htdocs/xampp">
      <IfModule php5_module>
        <Files "status.php">
            php_admin_flag safe_mode off

(Note that this is taken from the same file in the 1.7.0 xampp distribution. If you run into trouble, check that conf file and make the new one match it.)

You should then be able to start the apache server with PHP 5.2.8. You can tail the G:\xampp\apache\logs\error.log file to see whether there are any errors on startup. If not, you should be able to see the XAMPP splash screen when you navigate to localhost.

Hope this helps the next guy.



Remove multiple items from a Python list in just one statement

You can do it in one line by converting your lists to sets and using set.difference:

item_list = ['item', 5, 'foo', 3.14, True]
list_to_remove = ['item', 5, 'foo']

final_list = list(set(item_list) - set(list_to_remove))

Would give you the following output:

final_list = [3.14, True]

Note: this will remove duplicates in your input list and the elements in the output can be in any order (because sets don't preserve order). It also requires all elements in both of your lists to be hashable.

How to change the order of DataFrame columns?

import numpy as np
import pandas as pd
df = pd.DataFrame()
column_names = ['x','y','z','mean']
for col in column_names: 
    df[col] = np.random.randint(0,100, size=10000)

You can try out the following solutions :

Solution 1:

df = df[ ['mean'] + [ col for col in df.columns if col != 'mean' ] ]

Solution 2:

df = df[['mean', 'x', 'y', 'z']]

Solution 3:

col = df.pop("mean")
df = df.insert(0,, col)

Solution 4:

df.set_index(df.columns[-1], inplace=True)

Solution 5:

cols = list(df)
cols = [cols[-1]] + cols[:-1]
df = df[cols]

solution 6:

order = [1,2,3,0] # setting column's order
df = df[[df.columns[i] for i in order]]

Time Comparison:

Solution 1:

CPU times: user 1.05 ms, sys: 35 µs, total: 1.08 ms Wall time: 995 µs

Solution 2:

CPU times: user 933 µs, sys: 0 ns, total: 933 µs Wall time: 800 µs

Solution 3:

CPU times: user 0 ns, sys: 1.35 ms, total: 1.35 ms Wall time: 1.08 ms

Solution 4:

CPU times: user 1.23 ms, sys: 45 µs, total: 1.27 ms Wall time: 986 µs

Solution 5:

CPU times: user 1.09 ms, sys: 19 µs, total: 1.11 ms Wall time: 949 µs

Solution 6:

CPU times: user 955 µs, sys: 34 µs, total: 989 µs Wall time: 859 µs

How do I convert hex to decimal in Python?

>>> int("0xff", 16)


>>> int("FFFF", 16)

Read the docs.

Error parsing XHTML: The content of elements must consist of well-formed character data or markup

Facelets is a XML based view technology which uses XHTML+XML to generate HTML output. XML has five special characters which has special treatment by the XML parser:

  • < the start of a tag.
  • > the end of a tag.
  • " the start and end of an attribute value.
  • ' the alternative start and end of an attribute value.
  • & the start of an entity (which ends with ;).

In case of <, the XML parser is implicitly looking for the tag name and the end tag >. However, in your particular case, you were using < as a JavaScript operator, not as an XML entity. This totally explains the XML parsing error you got:

The content of elements must consist of well-formed character data or markup.

In essence, you're writing JavaScript code in the wrong place, a XML document instead of a JS file, so you should be escaping all XML special characters accordingly. The < must be escaped as &lt;.

So, essentially, the

for (var i = 0; i < length; i++) {

must become

for (var i = 0; i &lt; length; i++) {

to make it XML-valid.

However, this makes the JavaScript code harder to read and maintain. As stated in Mozilla Developer Network's excellent document Writing JavaScript for XHTML, you should be placing the JavaScript code in a character data (CDATA) block. Thus, in JSF terms, that would be:

        // ...

The XML parser will interpret the block's contents as "plain vanilla" character data and not as XML and hence interpret the XML special characters "as-is".

But, much better is to just put the JS code in its own JS file which you include by <script src>, or in JSF terms, the <h:outputScript>.

<h:outputScript name="functions.js" target="head" />

This way you don't need to worry about XML-special characters in your JS code. Additional advantage is that this gives the browser the opportunity to cache the JS file so that average response size is smaller.

See also:

How to find all positions of the maximum value in a list?

Also a solution, which gives only the first appearance, can be achieved by using numpy:

>>> import numpy as np
>>> a_np = np.array(a)
>>> np.argmax(a_np)

What's the difference between MyISAM and InnoDB?

The main differences between InnoDB and MyISAM ("with respect to designing a table or database" you asked about) are support for "referential integrity" and "transactions".

If you need the database to enforce foreign key constraints, or you need the database to support transactions (i.e. changes made by two or more DML operations handled as single unit of work, with all of the changes either applied, or all the changes reverted) then you would choose the InnoDB engine, since these features are absent from the MyISAM engine.

Those are the two biggest differences. Another big difference is concurrency. With MyISAM, a DML statement will obtain an exclusive lock on the table, and while that lock is held, no other session can perform a SELECT or a DML operation on the table.

Those two specific engines you asked about (InnoDB and MyISAM) have different design goals. MySQL also has other storage engines, with their own design goals.

So, in choosing between InnoDB and MyISAM, the first step is in determining if you need the features provided by InnoDB. If not, then MyISAM is up for consideration.

A more detailed discussion of differences is rather impractical (in this forum) absent a more detailed discussion of the problem space... how the application will use the database, how many tables, size of the tables, the transaction load, volumes of select, insert, updates, concurrency requirements, replication features, etc.

The logical design of the database should be centered around data analysis and user requirements; the choice to use a relational database would come later, and even later would the choice of MySQL as a relational database management system, and then the selection of a storage engine for each table.

Drag and drop elements from list into separate blocks

 function dragStart(event) {_x000D_
        function allowDrop(event) {_x000D_
        function drop(event) {_x000D_
            $("#maincontainer").append("<br/><table style='border:1px solid black; font-size:20px;'><tr><th>Name</th><th>Country</th><th>Experience</th><th>Technologies</th></tr><tr><td>  Bhanu Pratap   </td><td> India </td><td>  3 years   </td><td>  Javascript,Jquery,AngularJS,ASP.NET C#, XML,HTML,CSS,Telerik,XSLT,AJAX,etc...</td></tr></table>");_x000D_
 .droptarget {_x000D_
            float: left;_x000D_
            min-height: 100px;_x000D_
            min-width: 200px;_x000D_
            border: 1px solid black;_x000D_
            margin: 15px;_x000D_
            padding: 10px;_x000D_
            border: 1px solid #aaaaaa;_x000D_
        [contentEditable=true]:empty:not(:focus):before {_x000D_
            content: attr(data-text);_x000D_
<script src=""></script>_x000D_
<div class="droptarget" ondrop="drop(event)" ondragover="allowDrop(event)">_x000D_
        <p ondragstart="dragStart(event)" draggable="true" id="dragtarget">Drag Table</p>_x000D_
    <div id="maincontainer" contenteditable=true data-text="Drop here..." class="droptarget" ondrop="drop(event)" ondragover="allowDrop(event)"></div>

  1. this is just simple here i'm appending html table into a div at the end
  2. we can achieve this or any thing with a simple concept of calling a JavaScript function when we want (here on drop.)
  3. In this example you can drag & drop any number of tables, new table will be added below the last table exists in the div other wise it will be the first table in the div.
  4. here we can add text between tables or we can say the section where we drop tables is editable we can type text between tables. enter image description here

Thanks... :)

Programmatically get the version number of a DLL

Kris, your version works great when needing to load the assembly from the actual DLL file (and if the DLL is there!), however, one will get a much unwanted error if the DLL is EMBEDDED (i.e., not a file but an embedded DLL).

The other thing is, if one uses a versioning scheme with something like "1.2012.0508.0101", when one gets the version string you'll actually get "1.2012.518.101"; note the missing zeros.

So, here's a few extra functions to get the version of a DLL (embedded or from the DLL file):

    public static System.Reflection.Assembly GetAssembly(string pAssemblyName)
        System.Reflection.Assembly tMyAssembly = null;

        if (string.IsNullOrEmpty(pAssemblyName)) { return tMyAssembly; }
        tMyAssembly = GetAssemblyEmbedded(pAssemblyName);
        if (tMyAssembly == null) { GetAssemblyDLL(pAssemblyName); }

        return tMyAssembly;
    }//System.Reflection.Assembly GetAssemblyEmbedded(string pAssemblyDisplayName)

    public static System.Reflection.Assembly GetAssemblyEmbedded(string pAssemblyDisplayName)
        System.Reflection.Assembly tMyAssembly = null;

        if(string.IsNullOrEmpty(pAssemblyDisplayName)) { return tMyAssembly; }
        try //try #a
            tMyAssembly = System.Reflection.Assembly.Load(pAssemblyDisplayName);
        }// try #a
        catch (Exception ex)
            string m = ex.Message;
        }// try #a
        return tMyAssembly;
    }//System.Reflection.Assembly GetAssemblyEmbedded(string pAssemblyDisplayName)

    public static System.Reflection.Assembly GetAssemblyDLL(string pAssemblyNameDLL)
        System.Reflection.Assembly tMyAssembly = null;

        if (string.IsNullOrEmpty(pAssemblyNameDLL)) { return tMyAssembly; }
        try //try #a
            if (!pAssemblyNameDLL.ToLower().EndsWith(".dll")) { pAssemblyNameDLL += ".dll"; }
            tMyAssembly = System.Reflection.Assembly.LoadFrom(pAssemblyNameDLL);
        }// try #a
        catch (Exception ex)
            string m = ex.Message;
        }// try #a
        return tMyAssembly;
    }//System.Reflection.Assembly GetAssemblyFile(string pAssemblyNameDLL)

    public static string GetVersionStringFromAssembly(string pAssemblyDisplayName)
        string tVersion = "Unknown";
        System.Reflection.Assembly tMyAssembly = null;

        tMyAssembly = GetAssembly(pAssemblyDisplayName);
        if (tMyAssembly == null) { return tVersion; }
        tVersion = GetVersionString(tMyAssembly.GetName().Version.ToString());
        return tVersion;
    }//string GetVersionStringFromAssemblyEmbedded(string pAssemblyDisplayName)

    public static string GetVersionString(Version pVersion)
        string tVersion = "Unknown";
        if (pVersion == null) { return tVersion; }
        tVersion = GetVersionString(pVersion.ToString());
        return tVersion;
    }//string GetVersionString(Version pVersion)

    public static string GetVersionString(string pVersionString)
        string tVersion = "Unknown";
        string[] aVersion;

        if (string.IsNullOrEmpty(pVersionString)) { return tVersion; }
        aVersion = pVersionString.Split('.');
        if (aVersion.Length > 0) { tVersion = aVersion[0]; }
        if (aVersion.Length > 1) { tVersion += "." + aVersion[1]; }
        if (aVersion.Length > 2) { tVersion += "." + aVersion[2].PadLeft(4, '0'); }
        if (aVersion.Length > 3) { tVersion += "." + aVersion[3].PadLeft(4, '0'); }

        return tVersion;
    }//string GetVersionString(Version pVersion)

    public static string GetVersionStringFromAssemblyEmbedded(string pAssemblyDisplayName)
        string tVersion = "Unknown";
        System.Reflection.Assembly tMyAssembly = null;

        tMyAssembly = GetAssemblyEmbedded(pAssemblyDisplayName);
        if (tMyAssembly == null) { return tVersion; }
        tVersion = GetVersionString(tMyAssembly.GetName().Version.ToString());
        return tVersion;
    }//string GetVersionStringFromAssemblyEmbedded(string pAssemblyDisplayName)

    public static string GetVersionStringFromAssemblyDLL(string pAssemblyDisplayName)
        string tVersion = "Unknown";
        System.Reflection.Assembly tMyAssembly = null;

        tMyAssembly = GetAssemblyDLL(pAssemblyDisplayName);
        if (tMyAssembly == null) { return tVersion; }
        tVersion = GetVersionString(tMyAssembly.GetName().Version.ToString());
        return tVersion;
    }//string GetVersionStringFromAssemblyEmbedded(string pAssemblyDisplayName)

How do I load the contents of a text file into a javascript variable?

here is how I did it in jquery:

jQuery.get('http://localhost/foo.txt', function(data) {

Creating a "logical exclusive or" operator in Java

Because boolean data type is stored like an integer, bit operator ^ functions like a XOR operation if used with boolean values.

//©Mfpl -

    public class XOR_Test {
        public static void main (String args[]) {
            boolean a,b;

            a=false; b=false;
            System.out.println("a=false; b=false;  ->  " + (a^b));

            a=false; b=true;
            System.out.println("a=false; b=true;  ->  " + (a^b));

            a=true;  b=false;
            System.out.println("a=true;  b=false;  ->  " + (a^b));

            a=true; b=true;
            System.out.println("a=true; b=true;  ->  " + (a^b));

            /*  output of this program:
                    a=false; b=false;  ->  false
                    a=false; b=true;  ->  true
                    a=true;  b=false;  ->  true
                    a=true; b=true;  ->  false

How to increment an iterator by 2?

Assuming list size may not be an even multiple of step you must guard against overflow:

static constexpr auto step = 2;

// Guard against invalid initial iterator.
if (!list.empty())
    for (auto it = list.begin(); /*nothing here*/; std::advance(it, step))
        // do stuff...

        // Guard against advance past end of iterator.
        if (std::distance(it, list.end()) > step)

Depending on the collection implementation, the distance computation may be very slow. Below is optimal and more readable. The closure could be changed to a utility template with the list end value passed by const reference:

const auto advance = [&](list_type::iterator& it, size_t step)
    for (size_t i = 0; it != list.end() && i < step; std::next(it), ++i);

static constexpr auto step = 2;

for (auto it = list.begin(); it != list.end(); advance(it, step))
    // do stuff...

If there is no looping:

static constexpr auto step = 2;
auto it = list.begin();

if (step <= list.size())
    std::advance(it, step);

Get data from php array - AJAX - jQuery

you cannot access array (php array) from js try

$array = array(1,2,3,4,5,6);
echo json_encode($array);

and js

$(document).ready( function() {
    $('#prev').click(function() {
            type: 'POST',
            url: 'ajax.php',
            data: 'id=testdata',
            dataType: 'json',
            cache: false,
            success: function(result) {

Copying the cell value preserving the formatting from one cell to another in excel using VBA

Copying the Bold Text From one sheet to another sheet in excel By using VBScript 'Create instance Object

Set oXL = CreateObject("Excel.application")
oXL.Visible = True

Set oWB = oXL.Workbooks.Open("FilePath.xlsx")
Set oSheet = oWB.Worksheets("Sheet1")         'Source Sheet in workbook
Set oDestSheet = oWB.Worksheets("Sheet2")       'Destination sheet in workbook

r = oSheet.usedrange.rows.Count
c = oSheet.usedrange.columns.Count

For i = 1 To r
    For j = 1 To c
        If oSheet.Cells(i,j).font.Bold = True Then

        End If


How to create a number picker dialog?

A Simple Example:


<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android=""
    android:layout_height="match_parent" >

        android:layout_alignParentTop="true" />

        android:text="Apply" />



import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.NumberPicker;

public class NumberPickerActivity extends Activity 

  protected void onCreate(Bundle savedInstanceState) 

    NumberPicker np = (NumberPicker)findViewById(;
    np.setMinValue(1);// restricted number to minimum value i.e 1
    np.setMaxValue(31);// restricked number to maximum value i.e. 31

    np.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() 

      public void onValueChange(NumberPicker picker, int oldVal, int newVal) 

       // TODO Auto-generated method stub

       String Old = "Old Value : ";

       String New = "New Value : ";


     Log.d("NumberPicker", "NumberPicker");


}/* NumberPickerActivity */

AndroidManifest.xml : Specify theme for the activity as dialogue theme.

  android:label="@string/title_activity_number_picker" >

Hope it will help.

No provider for TemplateRef! (NgIf ->TemplateRef)

You missed the * in front of NgIf (like we all have, dozens of times):

<div *ngIf="answer.accepted">&#10004;</div>

Without the *, Angular sees that the ngIf directive is being applied to the div element, but since there is no * or <template> tag, it is unable to locate a template, hence the error.

If you get this error with Angular v5:

Error: StaticInjectorError[TemplateRef]:
    NullInjectorError: No provider for TemplateRef!

You may have <template>...</template> in one or more of your component templates. Change/update the tag to <ng-template>...</ng-template>.

ASP.NET MVC Page Won't Load and says "The resource cannot be found"

I found the solution for this problem, you don't have to delete the global.asax, as it contains some valuable info for your proyect to run smoothly, instead have a look at your controller's name, in my case, my controller was named something as MyController.cs and in the global.asax it's trying to reference a Home Controller.

Look for this lines in the global asax

   "Default", // Route name
   "{controller}/{action}/{id}", // URL with parameters
   new { controller = "Home", action = "Index", id = UrlParameter.Optional } 

in my case i had to get like this to work

    new { controller = "My", action = "Index", id = UrlParameter.Optional }

How to get these two divs side-by-side?

Best that works for me:



Django templates: If false?

You could write a custom template filter to do this in a half-dozen lines of code:

from django.template import Library

register = Library()

def is_false(arg): 
    return arg is False

Then in your template:

{% if myvar|is_false %}...{% endif %}

Of course, you could make that template tag much more generic... but this suits your needs specifically ;-)

How to set max and min value for Y axis

window.onload = function(){
var ctx = document.getElementById("canvas").getContext("2d");
window.myLine = new Chart(ctx ,{
          type: 'line',
          data: yourData,
          options: {
            scales: {
                yAxes: [{
                    ticks: {
                        min: 0,
                        max: 500    

I configure with 'options' in v2.

You should read documentation:

Getting datarow values into a string?

You can get a columns value by doing this


You will also have to cast to the appropriate type.

 output += (string)rows["ColumnName"]

Why are #ifndef and #define used in C++ header files?

Those are called #include guards.

Once the header is included, it checks if a unique value (in this case HEADERFILE_H) is defined. Then if it's not defined, it defines it and continues to the rest of the page.

When the code is included again, the first ifndef fails, resulting in a blank file.

That prevents double declaration of any identifiers such as types, enums and static variables.

How can I fix the form size in a C# Windows Forms application and not to let user change its size?

Check this:

// Define the border style of the form to a dialog box.
form1.FormBorderStyle = FormBorderStyle.FixedDialog;

// Set the MaximizeBox to false to remove the maximize box.
form1.MaximizeBox = false;

// Set the MinimizeBox to false to remove the minimize box.
form1.MinimizeBox = false;

// Set the start position of the form to the center of the screen.
form1.StartPosition = FormStartPosition.CenterScreen;

// Display the form as a modal dialog box.

How to check if an user is logged in Symfony2 inside a controller?

If you are using security annotation from the SensioFrameworkExtraBundle, you can use a few expressions (that are defined in \Symfony\Component\Security\Core\Authorization\ExpressionLanguageProvider):

  • @Security("is_authenticated()"): to check that the user is authed and not anonymous
  • @Security("is_anonymous()"): to check if the current user is the anonymous user
  • @Security("is_fully_authenticated()"): equivalent to is_granted('IS_AUTHENTICATED_FULLY')
  • @Security("is_remember_me()"): equivalent to is_granted('IS_AUTHENTICATED_REMEMBERED')

Is it possible to remove inline styles with jQuery?

Here is an inlineStyle selector filter I wrote that plugs into jQuery.

$("div:inlineStyle(display:block)") // will select all divs with an inline style of display: block set

In your case you could use this like:


How do I set Tomcat Manager Application User Name and Password for NetBeans?

Update the 'apache-tomcat-8.5.5\conf\tomcat-users.xml file. uncomment the roles and add/replace the following line.and restart server

tomcat-users.xml file

<role rolename="admin"/>
<role rolename="admin-gui"/>
<role rolename="manager-gui"/>
<user username="admin" password="admin" roles="standard,manager,admin,manager-gui,manager-script"/>

What data is stored in Ephemeral Storage of Amazon EC2 instance?

ephemeral is just another name of root volume when you launch Instance from AMI backed from Amazon EC2 instance store

So Everything will be stored on ephemeral.

if you have launched your instance from AMI backed by EBS volume then your instance does not have ephemeral.

How to enable LogCat/Console in Eclipse for Android?

Go to your desired perspective. Go to 'Window->show view' menu.

If you see logcat there, click it and you are done.

Else, click on 'other' (at the bottom), chose 'Android'->logcat.

Hope that helps :-)

jQuery find parent form

As of HTML5 browsers one can use inputElement.form - the value of the attribute must be an id of a <form> element in the same document. More info on MDN.

Execute write on doc: It isn't possible to write into a document from an asynchronously-loaded external script unless it is explicitly opened.

In case this is useful to anyone I had this same issue. I was bringing in a footer into a web page via jQuery. Inside that footer were some Google scripts for ads and retargeting. I had to move those scripts from the footer and place them directly in the page and that eliminated the notice.

C#: Printing all properties of an object

This is exactly what reflection is for. I don't think there's a simpler solution, but reflection isn't that code intensive anyway.

Setting UILabel text to bold

Use font property of UILabel:

label.font = UIFont(name:"HelveticaNeue-Bold", size: 16.0)

or use default system font to bold text:

label.font = UIFont.boldSystemFont(ofSize: 16.0)

How to animate button in android?

I can't comment on @omega's comment because I don't have enough reputation but the answer to that question should be something like:


<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android=""
    android:duration="100"          <!-- how long the animation lasts -->
    android:fromDegrees="-5"        <!-- how far to swing left -->
    android:pivotX="50%"            <!-- pivot from horizontal center -->
    android:pivotY="50%"            <!-- pivot from vertical center -->
    android:repeatCount="10"        <!-- how many times to swing back and forth -->
    android:repeatMode="reverse"    <!-- to make the animation go the other way -->
    android:toDegrees="5" />        <!-- how far to swing right -->

Animation shake = AnimationUtils.loadAnimation(this, R.anim.shake);

This is just one way of doing what you want, there may be better methods out there.

For each row in an R dataframe

You can try this, using apply() function

> d
  name plate value1 value2
1    A    P1      1    100
2    B    P2      2    200
3    C    P3      3    300

> f <- function(x, output) {
 wellName <- x[1]
 plateName <- x[2]
 wellID <- 1
 print(paste(wellID, x[3], x[4], sep=","))
 cat(paste(wellID, x[3], x[4], sep=","), file= output, append = T, fill = T)

> apply(d, 1, f, output = 'outputfile')

Can the Android drawable directory contain subdirectories?

Yes - it does suck :) However you can use the assets folder and have sub directories in there and load images that way.

What does request.getParameter return?

Both if (one.length() > 0) {} and if (!"".equals(one)) {} will check against an empty foo parameter, and an empty parameter is what you'd get if the the form is submitted with no value in the foo text field.

If there's any chance you can use the Expression Language to handle the parameter, you could access it with empty in an expression.

<c:if test='${not empty}'>
    This page code gets rendered.

How to replace a set of tokens in a Java String?

String.format("Hello %s Please find attached %s which is due on %s", name, invoice, date)

How to condense if/else into one line in Python?

There is the conditional expression:

a if cond else b

but this is an expression, not a statement.

In if statements, the if (or elif or else) can be written on the same line as the body of the block if the block is just one like:

if something: somefunc()
else: otherfunc()

but this is discouraged as a matter of formatting-style.

Slide up/down effect with ng-show and ng-animate

What's wrong with actually using ng-animate for ng-show as you mentioned?

<script src="lib/angulr.js"></script>
<script src="lib/angulr_animate.js"></script>
    var app=angular.module('ang_app', ['ngAnimate']);
    app.controller('ang_control01_main', function($scope) {

    #myDiv {
        transition: .5s;
        background-color: lightblue;
        height: 100px;
    } {
        height: 0;
<body ng-app="ang_app" ng-controller="ang_control01_main">
    <input type="checkbox" ng-model="myCheck">
    <div id="myDiv" ng-show="myCheck"></div>

Could not extract response: no suitable HttpMessageConverter found for response type

Here is a simple solution

try adding this dependency


<select> HTML element with height

I've used a few CSS hacks and targeted Chrome/Safari/Firefox/IE individually, as each browser renders selects a bit differently. I've tested on all browsers except IE.

For Safari/Chrome, set the height and line-height you want for your <select />.

For Firefox, we're going to kill Firefox's default padding and border, then set our own. Set padding to whatever you like.

For IE 8+, just like Chrome, we've set the height and line-height properties. These two media queries can be combined. But I kept it separate for demo purposes. So you can see what I'm doing.

Please note, for the height/line-height property to work in Chrome/Safari OSX, you must set the background to a custom value. I changed the color in my example.

Here's a jsFiddle of the below:

For the non-hack route, why not use a custom select plug-in via jQuery? Check out this:


    <option>Here's one option</option>
    <option>here's another option</option>


@media screen and (-webkit-min-device-pixel-ratio:0) {  /*safari and chrome*/
    select {
select::-moz-focus-inner { /*Remove button padding in FF*/ 
    border: 0;
    padding: 0;
@-moz-document url-prefix() { /* targets Firefox only */
    select {
        padding: 15px 0!important;
@media screen\0 { /* IE Hacks: targets IE 8, 9 and 10 */        
    select {

Resource blocked due to MIME type mismatch (X-Content-Type-Options: nosniff)

This might be because the browser cannot access a file. I stumbled with this type of error when creating application with node.js. You can try to directly request the script file (copying and pasting url) and see if you can retrieve it. You can see then what the real problem is. It can be because of permission of folder in which the file is located, or browser just cannot find it due to incorrect path to it. In node.js, after specifying route to file, all works.

Creating layout constraints programmatically

When using Auto Layout in code, setting the frame does nothing. So the fact that you specified a width of 200 on the view above, doesn't mean anything when you set constraints on it. In order for a view's constraint set to be unambiguous, it needs four things: an x-position, a y-position, a width, and a height for any given state.

Currently in the code above, you only have two (height, relative to the superview, and y-position, relative to the superview). In addition to this, you have two required constraints that could conflict depending on how the view's superview's constraints are setup. If the superview were to have a required constraint that specifies it's height be some value less than 748, you will get an "unsatisfiable constraints" exception.

The fact that you've set the width of the view before setting constraints means nothing. It will not even take the old frame into account and will calculate a new frame based on all of the constraints that it has specified for those views. When dealing with autolayout in code, I typically just create a new view using initWithFrame:CGRectZero or simply init.

To create the constraint set required for the layout you verbally described in your question, you would need to add some horizontal constraints to bound the width and x-position in order to give a fully-specified layout:

[self.view addConstraints:[NSLayoutConstraint

[self.view addConstraints:[NSLayoutConstraint

Verbally describing this layout reads as follows starting with the vertical constraint:

myView will fill its superview's height with a top and bottom padding equal to the standard space. myView's superview has a minimum height of 748pts. myView's width is 200pts and has a right padding equal to the standard space against its superview.

If you would simply like the view to fill the entire superview's height without constraining the superview's height, then you would just omit the (>=748) parameter in the visual format text. If you think that the (>=748) parameter is required to give it a height - you don't in this instance: pinning the view to the superview's edges using the bar (|) or bar with space (|-, -|) syntax, you are giving your view a y-position (pinning the view on a single-edge), and a y-position with height (pinning the view on both edges), thus satisfying your constraint set for the view.

In regards to your second question:

Using NSDictionaryOfVariableBindings(self.myView) (if you had an property setup for myView) and feeding that into your VFL to use self.myView in your VFL text, you will probably get an exception when autolayout tries to parse your VFL text. It has to do with the dot notation in dictionary keys and the system trying to use valueForKeyPath:. See here for a similar question and answer.

How to create dispatch queue in Swift 3

Compiled in XCode 8, Swift 3

 @IBAction func tap(_ sender: AnyObject) {

    let thisEmail = ""
    let thisPassword = "myPassword" .background).async {

        // Validate user input

        let result = self.validate(thisEmail, password: thisPassword)

        // Go back to the main thread to update the UI
        DispatchQueue.main.async {
            if !result



What's the difference between django OneToOneField and ForeignKey?

OneToOneField (one-to-one) realizes, in object orientation, the notion of composition, while ForeignKey (one-to-many) relates to agregation.

Cocoa: What's the difference between the frame and the bounds?

The bounds of an UIView is the rectangle, expressed as a location (x,y) and size (width,height) relative to its own coordinate system (0,0).

The frame of an UIView is the rectangle, expressed as a location (x,y) and size (width,height) relative to the superview it is contained within.

So, imagine a view that has a size of 100x100 (width x height) positioned at 25,25 (x,y) of its superview. The following code prints out this view's bounds and frame:

// This method is in the view controller of the superview
- (void)viewDidLoad {
    [super viewDidLoad];

    NSLog(@"bounds.origin.x: %f", label.bounds.origin.x);
    NSLog(@"bounds.origin.y: %f", label.bounds.origin.y);
    NSLog(@"bounds.size.width: %f", label.bounds.size.width);
    NSLog(@"bounds.size.height: %f", label.bounds.size.height);

    NSLog(@"frame.origin.x: %f", label.frame.origin.x);
    NSLog(@"frame.origin.y: %f", label.frame.origin.y);
    NSLog(@"frame.size.width: %f", label.frame.size.width);
    NSLog(@"frame.size.height: %f", label.frame.size.height);

And the output of this code is:

bounds.origin.x: 0
bounds.origin.y: 0
bounds.size.width: 100
bounds.size.height: 100

frame.origin.x: 25
frame.origin.y: 25
frame.size.width: 100
frame.size.height: 100

So, we can see that in both cases, the width and the height of the view is the same regardless of whether we are looking at the bounds or frame. What is different is the x,y positioning of the view. In the case of the bounds, the x and y coordinates are at 0,0 as these coordinates are relative to the view itself. However, the frame x and y coordinates are relative to the position of the view within the parent view (which earlier we said was at 25,25).

There is also a great presentation that covers UIViews. See slides 1-20 which not only explain the difference between frames and bounds but also show visual examples.

How to create a Multidimensional ArrayList in Java?

ArrayList<ArrayList<String>> array = new ArrayList<ArrayList<String>>();

Depending on your requirements, you might use a Generic class like the one below to make access easier:

import java.util.ArrayList;

class TwoDimentionalArrayList<T> extends ArrayList<ArrayList<T>> {
    public void addToInnerArray(int index, T element) {
        while (index >= this.size()) {
            this.add(new ArrayList<T>());

    public void addToInnerArray(int index, int index2, T element) {
        while (index >= this.size()) {
            this.add(new ArrayList<T>());

        ArrayList<T> inner = this.get(index);
        while (index2 >= inner.size()) {

        inner.set(index2, element);

How to round an average to 2 decimal places in PostgreSQL?

Try with this:

SELECT to_char (2/3::float, 'FM999999990.00');
-- RESULT: 0.67

Or simply:

SELECT round (2/3::DECIMAL, 2)::TEXT
-- RESULT: 0.67

indexOf Case Sensitive?

Yes, it is case-sensitive. You can do a case-insensitive indexOf by converting your String and the String parameter both to upper-case before searching.

String str = "Hello world";
String search = "hello";

Note that toUpperCase may not work in some circumstances. For instance this:

String str = "Feldbergstraße 23, Mainz";
String find = "mainz";
int idxU = str.toUpperCase().indexOf (find.toUpperCase ());
int idxL = str.toLowerCase().indexOf (find.toLowerCase ());

idxU will be 20, which is wrong! idxL will be 19, which is correct. What's causing the problem is tha toUpperCase() converts the "ß" character into TWO characters, "SS" and this throws the index off.

Consequently, always stick with toLowerCase()

How to write connection string in web.config file and read from it?

Are you sure that your configuration file (web.config) is at the right place and the connection string is really in the (generated) file? If you publish your file, the content of web.release.config might be copied.

The configuration and the access to the Connection string looks all right to me. I would always add a providername

  <add name="Dbconnection" 
       connectionString="Server=localhost; Database=OnlineShopping; 
       Integrated Security=True" providerName="System.Data.SqlClient" />

how to disable DIV element and everything inside

I think inline scripts are hard to stop instead you can try with this:

<div id="test">
    <div>Click Me</div>

and script:

$(function () {


Read More about .off()

How to specify non-default shared-library path in GCC Linux? Getting "error while loading shared libraries" when running

There are two ways to achieve that:

  • Use -rpath linker option:

gcc XXX.c -o xxx.out -L$HOME/.usr/lib -lXX -Wl,-rpath=/home/user/.usr/lib

  • Use LD_LIBRARY_PATH environment variable - put this line in your ~/.bashrc file:

    export LD_LIBRARY_PATH=/home/user/.usr/lib

This will work even for a pre-generated binaries, so you can for example download some packages from the, unpack the binaries and shared libraries into your home directory, and launch them without recompiling.

For a quick test, you can also do (in bash at least):

LD_LIBRARY_PATH=/home/user/.usr/lib ./xxx.out

which has the advantage of not changing your library path for everything else.

What's the difference between eval, exec, and compile?

exec is for statement and does not return anything. eval is for expression and returns value of expression.

expression means "something" while statement means "do something".

Git: cannot checkout branch - error: pathspec '...' did not match any file(s) known to git

I had the same issue for one of my branch.

These commands work for me.

git fetch --all
git checkout <branch-name>

ASP.NET MVC3 Razor - Html.ActionLink style

Here's the signature.

public static string ActionLink(this HtmlHelper htmlHelper, 
                                string linkText,
                                string actionName,
                                string controllerName,
                                object values, 
                                object htmlAttributes)

What you are doing is mixing the values and the htmlAttributes together. values are for URL routing.

You might want to do this.

@Html.ActionLink(Context.User.Identity.Name, "Index", "Account", null, 
     new { @style="text-transform:capitalize;" });

Checkout multiple git repos into same Jenkins workspace

Since Multiple SCMs Plugin is deprecated.

With Jenkins Pipeline its possible to checkout multiple git repos and after building it using gradle

node {   
def gradleHome

stage('Prepare/Checkout') { // for display purposes
    git branch: 'develop', url: ''

    dir('a-child-repo') {
       git branch: 'develop', url: ''

    env.JAVA_HOME="${tool 'JDK8'}"
    env.PATH="${env.JAVA_HOME}/bin:${env.PATH}" // set java home in jdk environment
    gradleHome = tool '3.4.1' 

stage('Build') {
  // Run the gradle build
  if (isUnix()) {
     sh "'${gradleHome}/bin/gradle' clean build"
  } else {
     bat(/"${gradleHome}\bin\gradle" clean build/)

You might want to consider using git submodules instead of a custom pipeline like this.

Remove whitespaces inside a string in javascript

You can use Strings replace method with a regular expression.

"Hello World ".replace(/ /g, "");

The replace() method returns a new string with some or all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp


  • / / - Regular expression matching spaces

  • g - Global flag; find all matches rather than stopping after the first match

const str = "H    e            l l       o  World! ".replace(/ /g, "");_x000D_
document.getElementById("greeting").innerText = str;
<p id="greeting"><p>

matplotlib: plot multiple columns of pandas data frame on the bar chart

Although the accepted answer works fine, since v0.21.0rc1 it gives a warning

UserWarning: Pandas doesn't allow columns to be created via a new attribute name

Instead, one can do

df[["X", "A", "B", "C"]].plot(x="X", kind="bar")

String Array object in Java

Currently you can't access the arrays named name and country, because they are member variables of your Athelete class.

Based on what it looks like you're trying to do, this will not work.

These arrays belong in your main class.