Programs & Examples On #Urlopen

Parsing HTTP Response in Python

You can also use python's requests library instead.

import requests

url = ''    
response = requests.get(url)    
dict = response.json()

Now you can manipulate the "dict" like a python dictionary.

Let JSON object accept bytes or let urlopen output strings

I have come to opinion that the question is the best answer :)

import json
from urllib.request import urlopen

response = urlopen("").read().decode('utf8')
obj = json.loads(response)

Python check if website exists

from urllib2 import Request, urlopen, HTTPError, URLError

user_agent = 'Mozilla/20.0.1 (compatible; MSIE 5.5; Windows NT)'
headers = { 'User-Agent':user_agent }
link = ""
req = Request(link, headers = headers)
        page_open = urlopen(req)
except HTTPError, e:
        print e.code
except URLError, e:
        print e.reason
        print 'ok'

To answer the comment of unutbu:

Because the default handlers handle redirects (codes in the 300 range), and codes in the 100-299 range indicate success, you will usually only see error codes in the 400-599 range. Source

Web-scraping JavaScript page with Python

I've been trying to find answer to this questions for two days. Many answers direct you to different issues. But serpentr's answer above is really to the point. It is the shortest, simplest solution. Just a reminder the last word "var" represents the variable name, so should be used as:

 result = driver.execute_script('var text = document.title ; return text')

How to use XMLReader in PHP?

For xml formatted with attributes...


<building address="some address" lat="28.902914" lng="-71.007235" />
<building address="some address" lat="48.892342" lng="-75.0423423" />
<building address="some address" lat="58.929753" lng="-79.1236987" />

php code:

$reader = new XMLReader();

if (!$reader->open("data.xml")) {
    die("Failed to open 'data.xml'");

while($reader->read()) {
  if ($reader->nodeType == XMLReader::ELEMENT && $reader->name == 'building') {
    $address = $reader->getAttribute('address');
    $latitude = $reader->getAttribute('lat');
    $longitude = $reader->getAttribute('lng');


Check if string matches pattern

regular expressions make this easy ...

[A-Z] will match exactly one character between A and Z

\d+ will match one or more digits

() group things (and also return things... but for now just think of them grouping)

+ selects 1 or more

set dropdown value by text using jquery

try this..

$(element).find("option:contains(" + theText+ ")").attr('selected', 'selected');

Meaning of @classmethod and @staticmethod for beginner?

Meaning of @classmethod and @staticmethod?

  • A method is a function in an object's namespace, accessible as an attribute.
  • A regular (i.e. instance) method gets the instance (we usually call it self) as the implicit first argument.
  • A class method gets the class (we usually call it cls) as the implicit first argument.
  • A static method gets no implicit first argument (like a regular function).

when should I use them, why should I use them, and how should I use them?

You don't need either decorator. But on the principle that you should minimize the number of arguments to functions (see Clean Coder), they are useful for doing just that.

class Example(object):

    def regular_instance_method(self):
        """A function of an instance has access to every attribute of that 
        instance, including its class (and its attributes.)
        Not accepting at least one argument is a TypeError.
        Not understanding the semantics of that argument is a user error.
        return some_function_f(self)

    def a_class_method(cls):
        """A function of a class has access to every attribute of the class.
        Not accepting at least one argument is a TypeError.
        Not understanding the semantics of that argument is a user error.
        return some_function_g(cls)

    def a_static_method():
        """A static method has no information about instances or classes
        unless explicitly given. It just lives in the class (and thus its 
        instances') namespace.
        return some_function_h()

For both instance methods and class methods, not accepting at least one argument is a TypeError, but not understanding the semantics of that argument is a user error.

(Define some_function's, e.g.:

some_function_h = some_function_g = some_function_f = lambda x=None: x

and this will work.)

dotted lookups on instances and classes:

A dotted lookup on an instance is performed in this order - we look for:

  1. a data descriptor in the class namespace (like a property)
  2. data in the instance __dict__
  3. a non-data descriptor in the class namespace (methods).

Note, a dotted lookup on an instance is invoked like this:

instance = Example()

and methods are callable attributes:


instance methods

The argument, self, is implicitly given via the dotted lookup.

You must access instance methods from instances of the class.

>>> instance = Example()
>>> instance.regular_instance_method()
<__main__.Example object at 0x00000000399524E0>

class methods

The argument, cls, is implicitly given via dotted lookup.

You can access this method via an instance or the class (or subclasses).

>>> instance.a_class_method()
<class '__main__.Example'>
>>> Example.a_class_method()
<class '__main__.Example'>

static methods

No arguments are implicitly given. This method works like any function defined (for example) on a modules' namespace, except it can be looked up

>>> print(instance.a_static_method())

Again, when should I use them, why should I use them?

Each of these are progressively more restrictive in the information they pass the method versus instance methods.

Use them when you don't need the information.

This makes your functions and methods easier to reason about and to unittest.

Which is easier to reason about?

def function(x, y, z): ...


def function(y, z): ...


def function(z): ...

The functions with fewer arguments are easier to reason about. They are also easier to unittest.

These are akin to instance, class, and static methods. Keeping in mind that when we have an instance, we also have its class, again, ask yourself, which is easier to reason about?:

def an_instance_method(self, arg, kwarg=None):
    cls = type(self)             # Also has the class of instance!

def a_class_method(cls, arg, kwarg=None):

def a_static_method(arg, kwarg=None):

Builtin examples

Here are a couple of my favorite builtin examples:

The str.maketrans static method was a function in the string module, but it is much more convenient for it to be accessible from the str namespace.

>>> 'abc'.translate(str.maketrans({'a': 'b'}))

The dict.fromkeys class method returns a new dictionary instantiated from an iterable of keys:

>>> dict.fromkeys('abc')
{'a': None, 'c': None, 'b': None}

When subclassed, we see that it gets the class information as a class method, which is very useful:

>>> class MyDict(dict): pass
>>> type(MyDict.fromkeys('abc'))
<class '__main__.MyDict'> 

My advice - Conclusion

Use static methods when you don't need the class or instance arguments, but the function is related to the use of the object, and it is convenient for the function to be in the object's namespace.

Use class methods when you don't need instance information, but need the class information perhaps for its other class or static methods, or perhaps itself as a constructor. (You wouldn't hardcode the class so that subclasses could be used here.)

How can I check which version of Angular I'm using?

For Angular 1 or 2 (but not for Angular 4+) :

you can also open the console on the developer tools of whatever browser you use and type angular.version to access the Javascript object that holds angular version.

Very useful when the script is minified with no header comment.

Validating a Textbox field for only numeric input.

I have this extension which is kind of multi-purpose:

    public static bool IsNumeric(this object value)
        if (value == null || value is DateTime)
            return false;

        if (value is Int16 || value is Int32 || value is Int64 || value is Decimal || value is Single || value is Double || value is Boolean)
            return true;

            if (value is string)
                Double.Parse(value as string);
            return true;
        catch { }
        return false;

It works for other data types. Should work fine for what you want to do.

What is the difference between XAMPP or WAMP Server & IIS?

WAMP is an acronym for Windows (OS), Apache (web-server), MySQL (database), PHP (language).

XAMPP and WampServer are both free packages of WAMP, with additional applications/tools, put together by different people. There are also other WAMPs such as UniformServer. And there are commercial WAMPs such as WampDeveloper (what I use).

Their differences are in the format/structure of the package, the configurations, and the included management applications.

IIS is a web-server application just like Apache is, except it's made by Microsoft and is Windows only (Apache runs on both Windows and Linux). IIS is also more geared towards using ASP.NET (vs. PHP) and "SQL Server" (vs. MySQL), though it can use PHP and MySQL too.

PHP-FPM and Nginx: 502 Bad Gateway

I made all this similar tweaks, but from time to time I was getting 501/502 errors (daily).

This are my settings on /etc/php5/fpm/pool.d/www.conf to avoid 501 and 502 nginx errors… The server has 16Gb RAM. This configuration is for a 8Gb RAM server so…

sudo nano /etc/php5/fpm/pool.d/www.conf

then set the following values for

pm.max_children = 70
pm.start_servers = 20
pm.min_spare_servers = 20
pm.max_spare_servers = 35
pm.max_requests = 500

After this changes restart php-fpm

sudo service php-fpm restart

Jackson with JSON: Unrecognized field, not marked as ignorable

it can be achieved 2 ways:

  1. Mark the POJO to ignore unknown properties

    @JsonIgnoreProperties(ignoreUnknown = true)
  2. Configure ObjectMapper that serializes/De-serializes the POJO/json as below:

    ObjectMapper mapper =new ObjectMapper();            
    // for Jackson version 1.X        
    mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    // for Jackson version 2.X
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) 

How to render a DateTime in a specific format in ASP.NET MVC 3?

Only View File Adjust like this. You may try this.

@Html.FormatValue( (object)Convert.ChangeType(item.transdate, typeof(object)), 
                            "{0: yyyy-MM-dd}")

item.transdate it is your DateTime type data.

Creating a Custom Event

You need to declare your event in the class from myObject :

public event EventHandler<EventArgs> myMethod; //you should name it as an event, like ObjectChanged.

then myNameEvent is the callback to handle the event, and it can be in any other class

Action bar navigation modes are deprecated in Android L

FragmentTabHost is also an option.

This code is from Android developer's site:

 * This demonstrates how you can implement switching between the tabs of a
 * TabHost through fragments, using FragmentTabHost.
public class FragmentTabs extends FragmentActivity {
    private FragmentTabHost mTabHost;

    protected void onCreate(Bundle savedInstanceState) {

    mTabHost = (FragmentTabHost)findViewById(;
    mTabHost.setup(this, getSupportFragmentManager(),;

            FragmentStackSupport.CountingFragment.class, null);
            LoaderCursorSupport.CursorLoaderListFragment.class, null);
            LoaderCustomSupport.AppListFragment.class, null);
            LoaderThrottleSupport.ThrottledLoaderListFragment.class, null);

How to prevent Google Colab from disconnecting?

The above answers with the help of some scripts maybe work well. I have a solution(or a kind of trick) for that annoying disconnection without scripts, especially when your program must read data from your google drive, like training a deep learning network model, where using scripts to do reconnect operation is of no use because once you disconnect with your colab, the program is just dead, you should manually connect to your google drive again to make your model able to read dataset again, but the scripts will not do that thing.
I've already test it many times and it works well.
When you run a program on the colab page with a browser(I use Chrome), just remember that don't do any operation to your browser once your program starts running, like: switch to other webpages, open or close another webpage, and so on, just just leave it alone there and waiting for your program finish running, you can switch to another software, like pycharm to keep writing your codes but not switch to another webpage. I don't know why open or close or switch to other pages will cause the connection problem of the google colab page, but each time I try to bothered my browser, like do some search job, my connection to colab will soon break down.

#1146 - Table 'phpmyadmin.pma_recent' doesn't exist

After I downloaded phpmyadmin from their website, I extracted the create_tables.sql file from the examples folder and then I imported it from the 'Import' tab of phpmyadmin.
It creates the database 'phpmyadmin' and the relevant table within.

This step might not be needed as the 12 tables were already there...
The problem seemed to be the double underscore in the tables' names.

I edited '' and added another underscore (__) after the 'pma_' prefix of the tables.


$cfg['Servers'][$i]['userconfig'] = 'pma_userconfig';


$cfg['Servers'][$i]['userconfig'] = 'pma__userconfig';

This solved the issue for me.

Android: Create a toggle button with image and no text

ToggleButton inherits from TextView so you can set drawables to be displayed at the 4 borders of the text. You can use that to display the icon you want on top of the text and hide the actual text

    android:textSize="0dp" />

The result compared to regular ToggleButton looks like

enter image description here

The seconds option is to use an ImageSpan to actually replace the text with an image. Looks slightly better since the icon is at the correct position but can't be done with layout xml directly.

You create a plain ToggleButton

    android:checked="false" />

Then set the "text" programmatially

ToggleButton button = (ToggleButton) findViewById(;
ImageSpan imageSpan = new ImageSpan(this, android.R.drawable.ic_menu_info_details);
SpannableString content = new SpannableString("X");
content.setSpan(imageSpan, 0, 1, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);

The result here in the middle - icon is placed slightly lower since it takes the place of the text.

enter image description here

Upload files with FTP using PowerShell

Goyuix's solution works great, but as presented it gives me this error: "The requested FTP command is not supported when using HTTP proxy."

Adding this line after $ftp.UsePassive = $true fixed the problem for me:

$ftp.Proxy = $null;

Difference between logical addresses, and physical addresses?

Logical address:- Logical address generated by the CPU . when we are give the problem to the computer then our computer pass the problem to the processor through logical address , which we are not seen this address called logical address .

Physical address :- when our processor create process and solve our problem then we store data in secondary memory through address called physical address

How to make picturebox transparent?

you can set the PictureBox BackColor proprty to Transparent

How to access the GET parameters after "?" in Express?

In my case with the given code, I was able to parse the value of the passed parameter in this way.

const express = require('express');
const bodyParser = require('body-parser');

const app = express(); 
app.use(bodyParser.urlencoded({ extended: false }));
let val1= req.body.par1;
let val2 = req.body.par2;

How to read file with space separated values in pandas

If you can't get text parsing to work using the accepted answer (e.g if your text file contains non uniform rows) then it's worth trying with Python's csv library - here's an example using a user defined Dialect:

 import csv

 csv.register_dialect('skip_space', skipinitialspace=True)
 with open(my_file, 'r') as f:
      reader=csv.reader(f , delimiter=' ', dialect='skip_space')
      for item in reader:

For homebrew mysql installs, where's my.cnf?

I believe the answer is no. Installing one in ~/.my.cnf or /usr/local/etc seems to be the preferred solution.

Command prompt won't change directory to another drive

The cd command on Windows is not intuitive for users of Linux systems. If you expect cd to go to another directory no matter whether it is in the current drive or another drive, you can create an alias for cd. Here is how to do it in Cmder:

  • Go to $CMDER_ROOT/config and open the file user_aliases.cmd
  • Add the following to the end of the file:
cd=cd /d $*

Restart Cmder and you should be able to cd to any directory you want. It is a small trick but works great and saves your time.

How to loop through all the properties of a class?

private void ResetAllProperties()
        Type type = this.GetType();
        PropertyInfo[] properties = (from c in type.GetProperties()
                                     where c.Name.StartsWith("Doc")
                                     select c).ToArray();
        foreach (PropertyInfo item in properties)
            if (item.PropertyType.FullName == "System.String")
                item.SetValue(this, "", null);

I used the code block above to reset all string properties in my web user control object which names are started with "Doc".

Email & Phone Validation in Swift

Swift 4 & Swift 5:

func isValidPhone(phone: String) -> Bool {
        let phoneRegex = "^[0-9+]{0,1}+[0-9]{5,16}$"
        let phoneTest = NSPredicate(format: "SELF MATCHES %@", phoneRegex)
        return phoneTest.evaluate(with: phone)

func isValidEmail(email: String) -> Bool {
        let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
        let emailTest = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
        return emailTest.evaluate(with: email)

How can I check if a directory exists in a Bash shell script?

More features using find

  • Check existence of the folder within sub-directories:

      found=`find -type d -name "myDirectory"`
      if [ -n "$found" ]
          # The variable 'found' contains the full path where "myDirectory" is.
          # It may contain several lines if there are several folders named "myDirectory".
  • Check existence of one or several folders based on a pattern within the current directory:

      found=`find -maxdepth 1 -type d -name "my*"`
      if [ -n "$found" ]
          # The variable 'found' contains the full path where folders "my*" have been found.
  • Both combinations. In the following example, it checks the existence of the folder in the current directory:

      found=`find -maxdepth 1 -type d -name "myDirectory"`
      if [ -n "$found" ]
          # The variable 'found' is not empty => "myDirectory"` exists.

Erase the current printed console line

under windows 10 one can use VT100 style by activating the VT100 mode in the current console to use escape sequences as follow :

#include <windows.h>
#include <iostream>


int main(){

  // enabling VT100 style in current console
  DWORD l_mode;
  HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
  SetConsoleMode( hStdout, l_mode |

  // create a waiting loop with changing text every seconds
  while(true) {
    // erase current line and go to line begining 
    std::cout << "\x1B[2K\r";
    std::cout << "wait a second .";
    std::cout << "\x1B[2K\r";
    std::cout << "wait a second ..";
    std::cout << "\x1B[2K\r";
    std::cout << "wait a second ...";
    std::cout << "\x1B[2K\r";
    std::cout << "wait a second ....";


see following link : windows VT100

Parsing Query String in node.js

There's also the QueryString module's parse() method:

var http = require('http'),
    queryString = require('querystring');

http.createServer(function (oRequest, oResponse) {

    var oQueryParams;

    // get query params as object
    if (oRequest.url.indexOf('?') >= 0) {
        oQueryParams = queryString.parse(oRequest.url.replace(/^.*\?/, ''));

        // do stuff

    oResponse.writeHead(200, {'Content-Type': 'text/plain'});
    oResponse.end('Hello world.');

}).listen(1337, '');

What is the difference between localStorage, sessionStorage, session and cookies?

  1. LocalStorage


    1. Web storage can be viewed simplistically as an improvement on cookies, providing much greater storage capacity. If you look at the Mozilla source code we can see that 5120KB (5MB which equals 2.5 Million chars on Chrome) is the default storage size for an entire domain. This gives you considerably more space to work with than a typical 4KB cookie.
    2. The data is not sent back to the server for every HTTP request (HTML, images, JavaScript, CSS, etc) - reducing the amount of traffic between client and server.
    3. The data stored in localStorage persists until explicitly deleted. Changes made are saved and available for all current and future visits to the site.


    1. It works on same-origin policy. So, data stored will only be available on the same origin.
  2. Cookies


    1. Compared to others, there's nothing AFAIK.


    1. The 4K limit is for the entire cookie, including name, value, expiry date etc. To support most browsers, keep the name under 4000 bytes, and the overall cookie size under 4093 bytes.
    2. The data is sent back to the server for every HTTP request (HTML, images, JavaScript, CSS, etc) - increasing the amount of traffic between client and server.

      Typically, the following are allowed:

      • 300 cookies in total
      • 4096 bytes per cookie
      • 20 cookies per domain
      • 81920 bytes per domain(Given 20 cookies of max size 4096 = 81920 bytes.)
  3. sessionStorage


    1. It is similar to localStorage.
    2. The data is not persistent i.e. data is only available per window (or tab in browsers like Chrome and Firefox). Data is only available during the page session. Changes made are saved and available for the current page, as well as future visits to the site on the same window. Once the window is closed, the storage is deleted.


    1. The data is available only inside the window/tab in which it was set.
    2. Like localStorage, it works on same-origin policy. So, data stored will only be available on the same origin.

Checkout across-tabs - how to facilitate easy communication between cross-origin browser tabs.

Comparing mongoose _id and strings

ObjectIDs are objects so if you just compare them with == you're comparing their references. If you want to compare their values you need to use the ObjectID.equals method:

if (results.userId.equals(AnotherMongoDocument._id)) {

Programmatically add new column to DataGridView

Here's a sample method that adds two extra columns programmatically to the grid view:

    private void AddColumnsProgrammatically()
        // I created these columns at function scope but if you want to access 
        // easily from other parts of your class, just move them to class scope.
        // E.g. Declare them outside of the function...
        var col3 = new DataGridViewTextBoxColumn();
        var col4 = new DataGridViewCheckBoxColumn();

        col3.HeaderText = "Column3";
        col3.Name = "Column3";

        col4.HeaderText = "Column4";
        col4.Name = "Column4";

        dataGridView1.Columns.AddRange(new DataGridViewColumn[] {col3,col4});

A great way to figure out how to do this kind of process is to create a form, add a grid view control and add some columns. (This process will actually work for ANY kind of form control. All instantiation and initialization happens in the Designer.) Then examine the form's Designer.cs file to see how the construction takes place. (Visual Studio does everything programmatically but hides it in the Form Designer.)

For this example I created two columns for the view named Column1 and Column2 and then searched Form1.Designer.cs for Column1 to see everywhere it was referenced. The following information is what I gleaned and, copied and modified to create two more columns dynamically:

// Note that this info scattered throughout the designer but can easily collected.

        System.Windows.Forms.DataGridViewTextBoxColumn Column1;
        System.Windows.Forms.DataGridViewCheckBoxColumn Column2;

        this.Column1 = new System.Windows.Forms.DataGridViewTextBoxColumn();
        this.Column2 = new System.Windows.Forms.DataGridViewCheckBoxColumn();

        this.dataGridView1.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] {

        this.Column1.HeaderText = "Column1";
        this.Column1.Name = "Column1";

        this.Column2.HeaderText = "Column2";
        this.Column2.Name = "Column2";

linux find regex

You should have a look on the -regextype argument of find, see manpage:

      -regextype type
          Changes the regular expression syntax understood by -regex and -iregex 
          tests which occur later on the command line.  Currently-implemented  
          types  are  emacs (this is the default), posix-awk, posix-basic, 
          posix-egrep and posix-extended. 

I guess the emacs type doesn't support the [[:digit:]] construct. I tried it with posix-extended and it worked as expected:

find -regextype posix-extended -regex '.*[1234567890]'
find -regextype posix-extended -regex '.*[[:digit:]]'

What's the difference between utf8_general_ci and utf8_unicode_ci?

For those people still arriving at this question in 2020 or later, there are newer options that may be better than both of these. For example, utf8mb4_0900_ai_ci.

All these collations are for the UTF-8 character encoding. The differences are in how text is sorted and compared.

_unicode_ci and _general_ci are two different sets of rules for sorting and comparing text according to the way we expect. Newer versions of MySQL introduce new sets of rules, too, such as _0900_ai_ci for equivalent rules based on Unicode 9.0 - and with no equivalent _general_ci variant. People reading this now should probably use one of these newer collations instead of either _unicode_ci or _general_ci. The description of those older collations below is provided for interest only.

MySQL is currently transitioning away from an older, flawed UTF-8 implementation. For now, you need to use utf8mb4 instead of utf8 for the character encoding part, to ensure you are getting the fixed version. The flawed version remains for backward compatibility, though it is being deprecated.

Key differences

  • utf8mb4_unicode_ci is based on the official Unicode rules for universal sorting and comparison, which sorts accurately in a wide range of languages.

  • utf8mb4_general_ci is a simplified set of sorting rules which aims to do as well as it can while taking many short-cuts designed to improve speed. It does not follow the Unicode rules and will result in undesirable sorting or comparison in some situations, such as when using particular languages or characters.

    On modern servers, this performance boost will be all but negligible. It was devised in a time when servers had a tiny fraction of the CPU performance of today's computers.

Benefits of utf8mb4_unicode_ci over utf8mb4_general_ci

utf8mb4_unicode_ci, which uses the Unicode rules for sorting and comparison, employs a fairly complex algorithm for correct sorting in a wide range of languages and when using a wide range of special characters. These rules need to take into account language-specific conventions; not everybody sorts their characters in what we would call 'alphabetical order'.

As far as Latin (ie "European") languages go, there is not much difference between the Unicode sorting and the simplified utf8mb4_general_ci sorting in MySQL, but there are still a few differences:

  • For examples, the Unicode collation sorts "ß" like "ss", and "Œ" like "OE" as people using those characters would normally want, whereas utf8mb4_general_ci sorts them as single characters (presumably like "s" and "e" respectively).

  • Some Unicode characters are defined as ignorable, which means they shouldn't count toward the sort order and the comparison should move on to the next character instead. utf8mb4_unicode_ci handles these properly.

In non-latin languages, such as Asian languages or languages with different alphabets, there may be a lot more differences between Unicode sorting and the simplified utf8mb4_general_ci sorting. The suitability of utf8mb4_general_ci will depend heavily on the language used. For some languages, it'll be quite inadequate.

What should you use?

There is almost certainly no reason to use utf8mb4_general_ci anymore, as we have left behind the point where CPU speed is low enough that the performance difference would be important. Your database will almost certainly be limited by other bottlenecks than this.

In the past, some people recommended to use utf8mb4_general_ci except when accurate sorting was going to be important enough to justify the performance cost. Today, that performance cost has all but disappeared, and developers are treating internationalization more seriously.

There's an argument to be made that if speed is more important to you than accuracy, you may as well not do any sorting at all. It's trivial to make an algorithm faster if you do not need it to be accurate. So, utf8mb4_general_ci is a compromise that's probably not needed for speed reasons and probably also not suitable for accuracy reasons.

One other thing I'll add is that even if you know your application only supports the English language, it may still need to deal with people's names, which can often contain characters used in other languages in which it is just as important to sort correctly. Using the Unicode rules for everything helps add peace of mind that the very smart Unicode people have worked very hard to make sorting work properly.

What the parts mean

Firstly, ci is for case-insensitive sorting and comparison. This means it's suitable for textual data, and case is not important. The other types of collation are cs (case-sensitive) for textual data where case is important, and bin, for where the encoding needs to match, bit for bit, which is suitable for fields which are really encoded binary data (including, for example, Base64). Case-sensitive sorting leads to some weird results and case-sensitive comparison can result in duplicate values differing only in letter case, so case-sensitive collations are falling out of favor for textual data - if case is significant to you, then otherwise ignorable punctuation and so on is probably also significant, and a binary collation might be more appropriate.

Next, unicode or general refers to the specific sorting and comparison rules - in particular, the way text is normalized or compared. There are many different sets of rules for the utf8mb4 character encoding, with unicode and general being two that attempt to work well in all possible languages rather than one specific one. The differences between these two sets of rules are the subject of this answer. Note that unicode uses rules from Unicode 4.0. Recent versions of MySQL add the rulesets unicode_520 using rules from Unicode 5.2, and 0900 (dropping the "unicode_" part) using rules from Unicode 9.0.

And lastly, utf8mb4 is of course the character encoding used internally. In this answer I'm talking only about Unicode based encodings.

How to resolve Error listenerStart when deploying web-app in Tomcat 5.5?


You should not have any server-specific libraries in the /WEB-INF/lib. Leave them in the appserver's own library. It would only lead to collisions in the classpath. Get rid of all appserver-specific libraries in /WEB-INF/lib (and also in JRE/lib and JRE/lib/ext if you have placed any of them there).

A common cause that the appserver-specific libraries are included in the webapp's library is that starters think that it is the right way to fix compilation errors of among others the javax.servlet classes not being resolveable. Putting them in webapp's library is the wrong solution. You should reference them in the classpath during compilation, i.e. javac -cp /path/to/server/lib/servlet.jar and so on, or if you're using an IDE, you should integrate the server in the IDE and associate the web project with the server. The IDE will then automatically take server-specific libraries in the classpath (buildpath) of the webapp project.

Vue - Deep watching an array of objects and calculating the change?

I have changed the implementation of it to get your problem solved, I made an object to track the old changes and compare it with that. You can use it to solve your issue.

Here I created a method, in which the old value will be stored in a separate variable and, which then will be used in a watch.

new Vue({
  methods: {
    setValue: function() {
      this.$data.oldPeople = _.cloneDeep(this.$data.people);
  mounted() {
  el: '#app',
  data: {
    people: [
      {id: 0, name: 'Bob', age: 27},
      {id: 1, name: 'Frank', age: 32},
      {id: 2, name: 'Joe', age: 38}
    oldPeople: []
  watch: {
    people: {
      handler: function (after, before) {
        // Return the object that changed
        var vm = this;
        let changed = after.filter( function( p, idx ) {
          return Object.keys(p).some( function( prop ) {
            return p[prop] !== vm.$data.oldPeople[idx][prop];
        // Log it
      deep: true,

See the updated codepen

Conditional WHERE clause in SQL Server

The problem with your query is that in CASE expressions, the THEN and ELSE parts have to have an expression that evaluates to a number or a varchar or any other datatype but not to a boolean value.

You just need to use boolean logic (or rather the ternary logic that SQL uses) and rewrite it:

    DateDropped = 0
AND ( @JobsOnHold = 1 AND DateAppr >= 0 
   OR (@JobsOnHold <> 1 OR @JobsOnHold IS NULL) AND DateAppr <> 0


nvl(value,defaultvalue) as Columnname

will set the missing values to defaultvalue specified

Query to get the names of all tables in SQL Server 2008 Database

To get the fields info too, you can use the following:

       COLUMN_NAME, substring(DATA_TYPE, 1,1) AS DATA_TYPE
FROM information_schema.COLUMNS 
WHERE TABLE_SCHEMA NOT IN("information_schema", "mysql", "performance_schema") 

How do I install and use the ASP.NET AJAX Control Toolkit in my .NET 3.5 web applications?

If you are using MasterPages and Content pages in your app - you also have the option of putting the ScriptManager on the Masterpage and then every ContentPage that uses that MasterPage will NOT need a script manager added. If you need some of the special configurations of the ScriptManager - like javascript file references - you can use a ScriptManagerProxy control on the content page that needs it.

Unable to show a Git tree in terminal


If you want a interactive tree, you can use tig. It can be installed by brew on OSX and apt-get in Linux.

brew install tig

This is what you get:

enter image description here

Deleting a local branch with Git

Switch to some other branch and delete Test_Branch, as follows:

$ git checkout master
$ git branch -d Test_Branch

If above command gives you error - The branch 'Test_Branch' is not fully merged. If you are sure you want to delete it and still you want to delete it, then you can force delete it using -D instead of -d, as:

$ git branch -D Test_Branch

To delete Test_Branch from remote as well, execute:

git push origin --delete Test_Branch

jQuery hasClass() - check for more than one class


if( ['class', 'class2'].some(c => [...element[0].classList].includes(c)) )

Vanilla JS

if( ['class', 'class2'].some(c => [...element.classList].includes(c)) )

Javascript Append Child AFTER Element

If you are looking for a plain JS solution, then you just use insertBefore() against nextSibling.

Something like:

parentGuest.parentNode.insertBefore(childGuest, parentGuest.nextSibling);

Note that default value of nextSibling is null, so, you don't need to do anything special for that.

Update: You don't even need the if checking presence of parentGuest.nextSibling like the currently accepted answer does, because if there's no next sibling, it will return null, and passing null to the 2nd argument of insertBefore() means: append at the end.



IF you are using jQuery (ignore otherwise, I have stated plain JS answer above), you can leverage the convenient after() method:

$("#one").after("<li id='two'>");


Vue js error: Component template should contain exactly one root element

You need to wrap all the html into one single element.

        <div class="form-group">
            <label for="avatar" class="control-label">Avatar</label>
            <input type="file" v-on:change="fileChange" id="avatar">
            <div class="help-block">
                Help block here updated 4  ...

        <div class="col-md-6">
            <input type="hidden" name="avatar_id">
            <img class="avatar" title="Current avatar">


    export default{
        methods: {
                console.log('Test of file input change')

Type.GetType("namespace.a.b.ClassName") returns null

I cheated. Since the types I want to create (by name) are all in In a dll I control, I just put a static method in the dll in the assembly that takes a simple name, and calls type.GetType from that context and returns the result.

The original purpose was so that the type could be specified by name in configuration data. I've since change the code so that the user specified a format to process. The format handler classes implement a interface that determines if the type can parse the specified format. I then use reflection to find types that implement the interface, and find one that handles the format. So now the configuration specifies a format name, a not a specific type. The reflection code can look at adjacent dlls and load, them so I have a sort poor man's plug-in architecture.

Multiple aggregate functions in HAVING clause

Something like this?

AND COUNT(caseID) < 4

Cannot connect to the Docker daemon on macOS

Docker for Mac is deprecated. And you don't need Homebrew to run Docker on Mac. Instead you'll likely want to install Docker Desktop or, if already installed, make sure it's up-to-date and running, then attempt to connect to the socket again.

enter image description here

What happens to C# Dictionary<int, int> lookup if the key does not exist?

The Dictionary throws a KeyNotFound exception in the event that the dictionary does not contain your key.

As suggested, ContainsKey is the appropriate precaution. TryGetValue is also effective.

This allows the dictionary to store a value of null more effectively. Without it behaving this way, checking for a null result from the [] operator would indicate either a null value OR the non-existance of the input key which is no good.

Adjust table column width to content size

If you want the table to still be 100% then set one of the columns to have a width:100%; That will extend that column to fill the extra space and allow the other columns to keep their auto width :)

Visual Studio loading symbols

In my case Visual Studio was looking for 3rd-party PDBs in paths that, on my machine, referenced an optical drive. Without a disc in the tray it took about Windows about ~30 to fail, which in turn slowed down Visual Studio as it tried to load the PDBs from that location. More detail is available in my complete answer here:

Authenticate Jenkins CI for Github private repository

One thing that got this working for me is to make sure that is in ~jenkins/.ssh/known_hosts.

Removing the first 3 characters from a string

Just use substring: "apple".substring(3); will return le

How to check if an email address is real or valid using PHP

You should check with SMTP.

That means you have to connect to that email's SMTP server.

After connecting to the SMTP server you should send these commands:

MAIL FROM: <no-[email protected]>
RCPT TO: <[email protected]>

If you get "<[email protected]> Relay access denied" that means this email is Invalid.

There is a simple PHP class. You can use it:

How to install MinGW-w64 and MSYS2?

MSYS has not been updated a long time, MSYS2 is more active, you can download from MSYS2, it has both mingw and cygwin fork package.

To install the MinGW-w64 toolchain (Reference):

  1. Open MSYS2 shell from start menu
  2. Run pacman -Sy pacman to update the package database
  3. Re-open the shell, run pacman -Syu to update the package database and core system packages
  4. Re-open the shell, run pacman -Su to update the rest
  5. Install compiler:
    • For 32-bit target, run pacman -S mingw-w64-i686-toolchain
    • For 64-bit target, run pacman -S mingw-w64-x86_64-toolchain
  6. Select which package to install, default is all
  7. You may also need make, run pacman -S make

Error TF30063: You are not authorized to access ... \DefaultCollection

I was also facing the same issue as you did. Here is what I did to solve:


  1. Click the 'Connect' icon just next to Home icon in Solution Explorer.
  2. Choose your project > Right Click > Connect.
  3. Try Check-in the project and this time it will happily proceed.

This is what I tried, and I did not need to logout from any sessions from TFS or VS Account.


  1. Just press refresh on the top of Team Explorer.
  2. Try to Check-in.

This is also easy method.

Hope this helps.

Boto3 to download all files from a S3 Bucket

I have a workaround for this that runs the AWS CLI in the same process.

Install awscli as python lib:

pip install awscli

Then define this function:

from awscli.clidriver import create_clidriver

def aws_cli(*cmd):
    old_env = dict(os.environ)

        # Environment
        env = os.environ.copy()
        env['LC_CTYPE'] = u'en_US.UTF'

        # Run awscli in the same process
        exit_code = create_clidriver().main(*cmd)

        # Deal with problems
        if exit_code > 0:
            raise RuntimeError('AWS CLI exited with code {}'.format(exit_code))

To execute:

aws_cli('s3', 'sync', '/path/to/source', 's3://bucket/destination', '--delete')

How to check if a Constraint exists in Sql server?

You can use the one above with one caveat:

    SELECT 1 FROM sys.foreign_keys 
    WHERE parent_object_id = OBJECT_ID(N'dbo.TableName') 
        AND name = 'CONSTRAINTNAME'

Need to use the name = [Constraint name] since a table may have multiple foreign keys and still not have the foreign key being checked for

R: Break for loop

your break statement should break out of the for (in in 1:n).

Personally I am always wary with break statements and double check it by printing to the console to double check that I am in fact breaking out of the right loop. So before you test add the following statement, which will let you know if you break before it reaches the end. However, I have no idea how you are handling the variable n so I don't know if it would be helpful to you. Make a n some test value where you know before hand if it is supposed to break out or not before reaching n.

for (in in 1:n)
    if (in == n)         #add this statement
        "sorry but the loop did not break"

    id_novo <- new_table_df$ID[in]
    else if(in == n)
        sold_df <- rbind(sold_df,old_table_df[out,])

Use Mockito to mock some methods but not others

To directly answer your question, yes, you can mock some methods without mocking others. This is called a partial mock. See the Mockito documentation on partial mocks for more information.

For your example, you can do something like the following, in your test:

Stock stock = mock(Stock.class);
when(stock.getPrice()).thenReturn(100.00);    // Mock implementation
when(stock.getQuantity()).thenReturn(200);    // Mock implementation
when(stock.getValue()).thenCallRealMethod();  // Real implementation

In that case, each method implementation is mocked, unless specify thenCallRealMethod() in the when(..) clause.

There is also a possibility the other way around with spy instead of mock:

Stock stock = spy(Stock.class);
when(stock.getPrice()).thenReturn(100.00);    // Mock implementation
when(stock.getQuantity()).thenReturn(200);    // Mock implementation
// All other method call will use the real implementations

In that case, all method implementation are the real one, except if you have defined a mocked behaviour with when(..).

There is one important pitfall when you use when(Object) with spy like in the previous example. The real method will be called (because stock.getPrice() is evaluated before when(..) at runtime). This can be a problem if your method contains logic that should not be called. You can write the previous example like this:

Stock stock = spy(Stock.class);
doReturn(100.00).when(stock).getPrice();    // Mock implementation
doReturn(200).when(stock).getQuantity();    // Mock implementation
// All other method call will use the real implementations

Another possibility may be to use org.mockito.Mockito.CALLS_REAL_METHODS, such as:

Stock MOCK_STOCK = Mockito.mock( Stock.class, CALLS_REAL_METHODS );

This delegates unstubbed calls to real implementations.

However, with your example, I believe it will still fail, since the implementation of getValue() relies on quantity and price, rather than getQuantity() and getPrice(), which is what you've mocked.

Another possibility is to avoid mocks altogether:

public void getValueTest() {
    Stock stock = new Stock(100.00, 200);
    double value = stock.getValue();
    assertEquals("Stock value not correct", 100.00*200, value, .00001);


You can simplify to:

WHERE a.Country = COALESCE(NULLIF(@Country,0), a.Country);

How can I see which Git branches are tracking which remote / upstream branch?

An alternative to kubi's answer is to have a look at the .git/config file which shows the local repository configuration:

cat .git/config

Recyclerview and handling different type of row inflation

We can achieve multiple view on single RecyclerView from below way :-

Dependencies on Gradle so add below code:-

compile ''
compile ''

RecyclerView in XML


Activity Code

private RecyclerView mRecyclerView;
private CustomAdapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private String[] mDataset = {“Data - one ”, “Data - two”,
    “Showing data three”, “Showing data four”};
private int mDatasetTypes[] = {DataOne, DataTwo, DataThree}; //view types
mRecyclerView = (RecyclerView) findViewById(;
mLayoutManager = new LinearLayoutManager(MainActivity.this);
//Adapter is created in the last step
mAdapter = new CustomAdapter(mDataset, mDataSetTypes);

First XML

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""
            android:textColor=“@color/white“ />
            android:textSize="30sp" />

Second XML

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""
            android:textColor="@color/white" />
            android:textSize="30sp" />

Third XML

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""
            android:text=“DataThree” />
            android:textSize="25sp" />
            android:text=“Show More” />

Now time to make adapter and this is main for showing different -2 view on same recycler view so please check this code focus fully :-

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
    private static final String TAG = "CustomAdapter";
    private String[] mDataSet;
    private int[] mDataSetTypes;
    public static final int dataOne = 0;
    public static final int dataTwo = 1;
    public static final int dataThree = 2;
    public static class ViewHolder extends RecyclerView.ViewHolder {
        public ViewHolder(View v) {
    public class DataOne extends ViewHolder {
        TextView temp;
        public DataOne(View v) {
            this.temp = (TextView) v.findViewById(;
    public class DataTwo extends ViewHolder {
        TextView score;
        public DataTwo(View v) {
            this.score = (TextView) v.findViewById(;
    public class DataThree extends ViewHolder {
        TextView headline;
        Button read_more;
        public DataThree(View v) {
            this.headline = (TextView) v.findViewById(;
            this.read_more = (Button) v.findViewById(;
    public CustomAdapter(String[] dataSet, int[] dataSetTypes) {
        mDataSet = dataSet;
        mDataSetTypes = dataSetTypes;
    public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
        View v;
        if (viewType == dataOne) {
            v = LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.weather_card, viewGroup, false);
            return new DataOne(v);
        } else if (viewType == dataTwo) {
            v = LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.news_card, viewGroup, false);
            return new DataThree(v);
        } else {
            v = LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.score_card, viewGroup, false);
            return new DataTwo(v);
    public void onBindViewHolder(ViewHolder viewHolder, final int position) {
        if (viewHolder.getItemViewType() == dataOne) {
            DataOne holder = (DataOne) viewHolder;
        else if (viewHolder.getItemViewType() == dataTwo) {
            DataThree holder = (DataTwo) viewHolder;
        else {
            DataTwo holder = (DataTwo) viewHolder;
    public int getItemCount() {
        return mDataSet.length;
    public int getItemViewType(int position) {
        return mDataSetTypes[position];

You can check also this link for more information.

Spring jUnit Testing properties file

As for the testing, you should use from Spring 4.1 which will overwrite the properties defined in other places:


Test property sources have higher precedence than those loaded from the operating system's environment or Java system properties as well as property sources added by the application like @PropertySource

Best way to track onchange as-you-type in input type="text"?

2018 here, this is what I do:

$(inputs).on('change keydown paste input propertychange click keyup blur',handler);

If you can point out flaws in this approach, I would be grateful.

AngularJS: How to make angular load script inside ng-include?

This won't work anymore from 1.2.0-rc1. See this issue for more about it, in which I posted a comment describing a quick workaround. I'll share it here as well :

// Quick fix : replace the script tag you want to load by a <div load-script></div>.
// Then write a loadScript directive that creates your script tag and appends it to your div.
// Took me one minute.

// This means that in your view, instead of :
<script src="/path/to/my/file.js"></script>

// You'll have :
<div ng-load-script></div>

// And then write a directive like :
angular.module('myModule', []).directive('loadScript', [function() {
    return function(scope, element, attrs) {
        angular.element('<script src="/path/to/my/file.js"></script>').appendTo(element);

Not the best solution ever, but hey, neither is putting script tags in subsequent views. In my case I have to do this is order to use Facebook/Twitter/etc. widgets.

Deserialize JSON to Array or List with HTTPClient .ReadAsAsync using .NET 4.0 Task pattern

Instead of handcranking your models try using something like the website. Paste In an example JSON response, the fuller the better and then pull in the resultant generated classes. This, at least, takes away some moving parts, will get you the shape of the JSON in csharp giving the serialiser an easier time and you shouldnt have to add attributes.

Just get it working and then make amendments to your class names, to conform to your naming conventions, and add in attributes later.

EDIT: Ok after a little messing around I have successfully deserialised the result into a List of Job (I used to create the class for me)

public class Job
        public string id { get; set; }
        public string position_title { get; set; }
        public string organization_name { get; set; }
        public string rate_interval_code { get; set; }
        public int minimum { get; set; }
        public int maximum { get; set; }
        public string start_date { get; set; }
        public string end_date { get; set; }
        public List<string> locations { get; set; }
        public string url { get; set; }

And an edit to your code:

        List<Job> model = null;
        var client = new HttpClient();
        var task = client.GetAsync("")
          .ContinueWith((taskwithresponse) =>
              var response = taskwithresponse.Result;
              var jsonString = response.Content.ReadAsStringAsync();
              model = JsonConvert.DeserializeObject<List<Job>>(jsonString.Result);


This means you can get rid of your containing object. Its worth noting that this isn't a Task related issue but rather a deserialisation issue.


There is a way to take a JSON object and generate classes in Visual Studio. Simply copy the JSON of choice and then Edit> Paste Special > Paste JSON as Classes. A whole page is devoted to this here:

SCRIPT5: Access is denied in IE9 on xmlhttprequest

This error message (SCRIPT5: Access is denied.) can also be encountered if the target page of a .replace method is not found (I had entered the page name incorrectly). I know because it just happened to me, which is why I went searching for some more information about the meaning of the error message.

Maximum size of an Array in Javascript

I have built a performance framework that manipulates and graphs millions of datasets, and even then, the javascript calculation latency was on order of tens of milliseconds. Unless you're worried about going over the array size limit, I don't think you have much to worry about.

Updating to latest version of CocoaPods?

Open the Terminal -> copy below command

sudo gem install cocoapods

It will install the latest stable version of cocoapods.

after that, you need to update pod using below command

pod setup

You can check pod version using below command

pod --version

How to select clear table contents without destroying the table?

I use this code to remove my data but leave the formulas in the top row. It also removes all rows except for the top row and scrolls the page up to the top.

Sub CleanTheTable()
    Application.ScreenUpdating = False
    'Remove the filters if one exists.
    If ActiveSheet.FilterMode Then
    End If
    'Clear all lines but the first one in the table leaving formulas for the next go round.
    With Worksheets("Data").ListObjects("TestTable")
    On Error Resume Next
    .DataBodyRange.Offset(1).Resize(.DataBodyRange.Rows.Count - 1, .DataBodyRange.Columns.Count).Rows.Delete
    ActiveWindow.SmallScroll Down:=-10000

    End With
Application.ScreenUpdating = True
End Sub

Expected initializer before function name

You are missing a semicolon at the end of your 'struct' definition.



needs to be


Function to calculate distance between two coordinates

Derek's solution worked fine for me, and I've just simply converted it to PHP, hope it helps somebody out there !

function calcCrow($lat1, $lon1, $lat2, $lon2){
        $R = 6371; // km
        $dLat = toRad($lat2-$lat1);
        $dLon = toRad($lon2-$lon1);
        $lat1 = toRad($lat1);
        $lat2 = toRad($lat2);

        $a = sin($dLat/2) * sin($dLat/2) +sin($dLon/2) * sin($dLon/2) * cos($lat1) * cos($lat2); 
        $c = 2 * atan2(sqrt($a), sqrt(1-$a)); 
        $d = $R * $c;
        return $d;

// Converts numeric degrees to radians
function toRad($Value) 
    return $Value * pi() / 180;

How to change default Anaconda python environment

I got this when installing a library using anaconda. My version went from Python 3.* to 2.7 and a lot of my stuff stopped working. The best solution I found was to first see the most recent version available:

conda search python

Then update to the version you want:

conda install python=3.*.*


Other helpful commands:

conda info
python --version

Android "Only the original thread that created a view hierarchy can touch its views."

I've been in this situation, but I found a solution with the Handler Object.

In my case, I want to update a ProgressDialog with the observer pattern. My view implements observer and overrides the update method.

So, my main thread create the view and another thread call the update method that update the ProgressDialop and....:

Only the original thread that created a view hierarchy can touch its views.

It's possible to solve the problem with the Handler Object.

Below, different parts of my code:

public class ViewExecution extends Activity implements Observer{

    static final int PROGRESS_DIALOG = 0;
    ProgressDialog progressDialog;
    int currentNumber;

    public void onCreate(Bundle savedInstanceState) {

        currentNumber = 0;
        final Button launchPolicyButton =  ((Button) this.findViewById(;
        launchPolicyButton.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {

    protected Dialog onCreateDialog(int id) {
        switch(id) {
        case PROGRESS_DIALOG:
            progressDialog = new ProgressDialog(this);
            return progressDialog;
            return null;

    protected void onPrepareDialog(int id, Dialog dialog) {
        switch(id) {
        case PROGRESS_DIALOG:


    // Define the Handler that receives messages from the thread and update the progress
    final Handler handler = new Handler() {
        public void handleMessage(Message msg) {
            int current = msg.arg1;
            if (current >= 100){
                removeDialog (PROGRESS_DIALOG);

    // The method called by the observer (the second thread)
    public void update(Observable obs, Object arg1) {

        Message msg = handler.obtainMessage();
        msg.arg1 = ++currentPluginNumber;

This explanation can be found on this page, and you must read the "Example ProgressDialog with a second thread".

Encoding URL query parameters in Java

if you have only space problem in url. I have used below code and it work fine

String url;
URL myUrl = new URL(url.replace(" ","%20"));

example : url is sir

then output of muUrl is

Unknown column in 'field list' error on MySQL Update query

Just sharing my experience on this. I was having this same issue. The insert or update statement is correct. And I also checked the encoding. The column does exist. Then! I found out that I was referencing the column in my Trigger. You should also check your trigger see if any script is referencing the column you are having the problem with.

java : convert float to String and String to float

Using Java’s Float class.

float f = Float.parseFloat("25");
String s = Float.toString(25.0f);

To compare it's always better to convert the string to float and compare as two floats. This is because for one float number there are multiple string representations, which are different when compared as strings (e.g. "25" != "25.0" != "25.00" etc.)

How do you create a Marker with a custom icon for google maps API v3?

LatLng hello = new LatLng(X, Y);          // whereX & Y are coordinates

Bitmap icon = BitmapFactory.decodeResource(getApplicationContext().getResources(),
      ;   // where university is the icon name that is used as a marker.

mMap.addMarker(new MarkerOptions().icon(BitmapDescriptorFactory.fromBitmap(icon)).position(hello).title("Hello World!"));


Replace duplicate spaces with a single space in T-SQL

I typically use this approach:

declare @s varchar(50)
set @s = 'TEST         TEST'
select REPLACE(REPLACE(REPLACE(@s,' ','[o][c]'),'[c][o]',''),'[o][c]',' ')

SQL Server - In clause with a declared variable

SET @IDQuery = 'SELECT ID FROM SomeTable WHERE Condition=Something'
INSERT INTO @ExcludedList EXEC(@IDQuery)    

I know I'm responding to an old post but I wanted to share an example of how to use Variable Tables when one wants to avoid using dynamic SQL. I'm not sure if its the most efficient way, however this has worked in the past for me when dynamic SQL was not an option.

Where is the user's Subversion config file stored on the major operating systems?

@Baxter's is mostly correct but it is missing one important Windows-specific detail.

Subversion's runtime configuration area is stored in the %APPDATA%\Subversion\ directory. The files are config and servers.

However, in addition to text-based configuration files, Subversion clients can use Windows Registry to store the client settings. It makes it possible to modify the settings with PowerShell in a convenient manner, and also distribute these settings to user workstations in Active Directory environment via AD Group Policy. See SVNBook | Configuration and the Windows Registry (you can find examples and a sample *.reg file there).

enter image description here

How to remove all .svn directories from my application directories

Try this:

find . -name .svn -exec rm -rf '{}' \;

Before running a command like that, I often like to run this first:

find . -name .svn -exec ls '{}' \;

How to check a not-defined variable in JavaScript

I've often done:

function doSomething(variable)
    var undef;

    if(variable === undef)
         alert('Hey moron, define this bad boy.');

Embed Google Map code in HTML with marker

The element that you posted looks like it's just copy-pasted from the Google Maps embed feature.

If you'd like to drop markers for the locations that you have, you'll need to write some JavaScript to do so. I'm learning how to do this as well.

Check out the following:

It has several examples and code samples that can be easily re-used and adapted to fit your current problem.

How to see indexes for a database or table in MySQL?

To get all indexed columns per index in one column in the sequence order.

SELECT table_name AS `Table`,
       index_name AS `Index`,
       GROUP_CONCAT(column_name ORDER BY seq_in_index) AS `Columns`
FROM information_schema.statistics
WHERE table_schema = 'sakila'


Maven: add a folder or jar file into current classpath

The classpath setting of the compiler plugin are two args. Changed it like this and it worked for me:


I used the gmavenplus-plugin to read the path and create the property 'cp':

      Use Groovy to read classpath and store into
      file named value of property <cpfile>

      In second step use Groovy to read the contents of
      the file into a new property named <cp>

      In the compiler plugin this is used to create a
      valid classpath
        <!-- any version of Groovy \>= 1.5.0 should work here -->

                def file = new File(
                /* create a new property named 'cp'*/
       = file.getText()
                println '<<< Retrieving classpath into new property named <cp> >>>'
                println 'cp = ' +

Element-wise addition of 2 lists?

If you need to handle lists of different sizes, worry not! The wonderful itertools module has you covered:

>>> from itertools import zip_longest
>>> list1 = [1,2,1]
>>> list2 = [2,1,2,3]
>>> [sum(x) for x in zip_longest(list1, list2, fillvalue=0)]
[3, 3, 3, 3]

In Python 2, zip_longest is called izip_longest.

See also this relevant answer and comment on another question.

Creating a simple configuration file and parser in C++

I've searched config parsing libraries for my project recently and found these libraries:

How do I put double quotes in a string in vba?

I prefer the answer of tabSF . implementing the same to your answer. here below is my approach

Worksheets("Sheet1").Range("A1").Value = "=IF(Sheet1!A1=0," & CHR(34) & CHR(34) & ",Sheet1!A1)"

Get Mouse Position

I am doing something like this to get mouse coordinates using Robot, I use these coordinates further in few of the games I am developing:

public class ForMouseOnly {
    public static void main(String[] args) throws InterruptedException {
        int x = MouseInfo.getPointerInfo().getLocation().x;
        int y = MouseInfo.getPointerInfo().getLocation().y;
        while (true) {

            if (x != MouseInfo.getPointerInfo().getLocation().x || y != MouseInfo.getPointerInfo().getLocation().y) {
                System.out.println("(" + MouseInfo.getPointerInfo().getLocation().x + ", "
                        + MouseInfo.getPointerInfo().getLocation().y + ")");
                x = MouseInfo.getPointerInfo().getLocation().x;
                y = MouseInfo.getPointerInfo().getLocation().y;

How can I store JavaScript variable output into a PHP variable?

You can solve this problem by using AJAX. You don't need to load JQuery for AJAX but it has a better error and success handling than native JS.

I would do it like so:

1) add an click eventlistener to all my anchors on the page. 2) on click, you can setup an ajax-request to your php, in the POST-DATA you set the anchor id or the text-value 3) the php gets the value and you can setup a request to your database. Then you return the value which you need and echo it to the ajax-request. 4) your success function of the ajax-request is doing some stuff

For more information about ajax-requests look back here:

-> Ajax-Request NATIVE

A simple JQuery examle:

  $.ajax({url: "demo_test.txt", success: function(result){

How can I get the concatenation of two lists in Python without modifying either one?

you could always create a new list which is a result of adding two lists.

>>> k = [1,2,3] + [4,7,9]
>>> k
[1, 2, 3, 4, 7, 9]

Lists are mutable sequences so I guess it makes sense to modify the original lists by extend or append.

what is the difference between XSD and WSDL

WSDL (Web Services Description Language) describes your service and its operations - what is the service called, which methods does it offer, what kind of in parameters and return values do these methods have?

It's a description of the behavior of the service - it's functionality.

XSD (Xml Schema Definition) describes the static structure of the complex data types being exchanged by those service methods. It describes the types, their fields, any restriction on those fields (like max length or a regex pattern) and so forth.

It's a description of datatypes and thus static properties of the service - it's about data.

How to register multiple implementations of the same interface in Asp.Net Core?

I know this post is a couple years old, but I keep running into this and I'm not happy with the service locator pattern.

Also, I know the OP is looking for an implementation which allows you to choose a concrete implementation based on a string. I also realize that the OP is specifically asking for an implementation of an identical interface. The solution I'm about to describe relies on adding a generic type parameter to your interface. The problem is that you don't have any real use for the type parameter other than service collection binding. I'll try to describe a situation which might require something like this.

Imagine configuration for such a scenario in appsettings.json which might look something like this (this is just for demonstration, your configuration can come from wherever you want as long as you have the correction configuration provider):

  "sqlDataSource": {
    "connectionString": "Data Source=localhost; Initial catalog=Foo; Connection Timeout=5; Encrypt=True;",
    "username": "foo",
    "password": "this normally comes from a secure source, but putting here for demonstration purposes"
  "mongoDataSource": {
    "hostName": "",
    "port": 27026,
    "collection": "foo"

You really need a type that represents each of your configuration options:

public class SqlDataSource
  public string ConnectionString { get;set; }
  public string Username { get;set; }
  public string Password { get;set; }

public class MongoDataSource
  public string HostName { get;set; }
  public string Port { get;set; }
  public string Collection { get;set; }

Now, I know that it might seem a little contrived to have two implementations of the same interface, but it I've definitely seen it in more than one case. The ones I usually come across are:

  1. When migrating from one data store to another, it's useful to be able to implement the same logical operations using the same interfaces so that you don't need to change the calling code. This also allows you to add configuration which swaps between different implementations at runtime (which can be useful for rollback).
  2. When using the decorator pattern. The reason you might use that pattern is that you want to add functionality without changing the interface and fall back to the existing functionality in certain cases (I've used it when adding caching to repository classes because I want circuit breaker-like logic around connections to the cache that fall back to the base repository -- this gives me optimal behavior when the cache is available, but behavior that still functions when it's not).

Anyway, you can reference them by adding a type parameter to your service interface so that you can implement the different implementations:

public interface IService<T> {
  void DoServiceOperation();

public class MongoService : IService<MongoDataSource> {
  private readonly MongoDataSource _options;

  public FooService(IOptionsMonitor<MongoDataSource> serviceOptions){
    _options = serviceOptions.CurrentValue

  void DoServiceOperation(){
    //do something with your mongo data source options (connect to database)
    throw new NotImplementedException();

public class SqlService : IService<SqlDataSource> {
  private readonly SqlDataSource_options;

  public SqlService (IOptionsMonitor<SqlDataSource> serviceOptions){
    _options = serviceOptions.CurrentValue

  void DoServiceOperation(){
    //do something with your sql data source options (connect to database)
    throw new NotImplementedException();

In startup, you'd register these with the following code:


services.AddTransient<IService<SqlDataSource>, SqlService>();
services.AddTransient<IService<MongoDataSource>, MongoService>();

Finally in the class which relies on the Service with a different connection, you just take a dependency on the service you need and the DI framework will take care of the rest:

public class ControllerWhichNeedsMongoService {  
  private readonly IService<MongoDataSource> _mongoService;
  private readonly IService<SqlDataSource> _sqlService ;

  public class ControllerWhichNeedsMongoService(
    IService<MongoDataSource> mongoService, 
    IService<SqlDataSource> sqlService
    _mongoService = mongoService;
    _sqlService = sqlService;

  public async Task GetStuff()
       await _mongoService.DoServiceOperation();
    await _sqlService.DoServiceOperation();

These implementations can even take a dependency on each other. The other big benefit is that you get compile-time binding so any refactoring tools will work correctly.

Hope this helps someone in the future.

How can I get a list of all functions stored in the database of a particular schema in PostgreSQL?

This function returns all user defined routines in current database.

SELECT pg_get_functiondef(p.oid) FROM pg_proc p
INNER JOIN pg_namespace ns ON p.pronamespace = ns.oid
WHERE ns.nspname = 'public';

Drawing an image from a data URL to a canvas

You might wanna clear the old Image before setting a new Image.

You also need to update the Canvas size for a new Image.

This is how I am doing in my project:

    // on image load update Canvas Image 
    this.image.onload = () => {

      // Clear Old Image and Reset Bounds
      canvasContext.clearRect(0, 0, this.canvas.width, this.canvas.height);
      this.canvas.height = this.image.height;
      this.canvas.width = this.image.width;

      // Redraw Image

Call an overridden method from super class in typescript

below is an generic example

    //base class
    class A {
        // The virtual method
        protected virtualStuff1?():void;
        public Stuff2(){
            //Calling overridden child method by parent if implemented
            this.virtualStuff1 && this.virtualStuff1();
            alert("Baseclass Stuff2");
    //class B implementing virtual method
    class B extends A{
        // overriding virtual method
        public virtualStuff1()
            alert("Class B virtualStuff1");
    //Class C not implementing virtual method
    class C extends A{
    var b1 = new B();
    var c1= new C();

Multiple actions were found that match the request in Web Api

I found that that when I have two Get methods, one parameterless and one with a complex type as a parameter that I got the same error. I solved this by adding a dummy parameter of type int, named Id, as my first parameter, followed by my complex type parameter. I then added the complex type parameter to the route template. The following worked for me.

First get:

public IEnumerable<SearchItem> Get()

Second get:

public IEnumerable<SearchItem> Get(int id, [FromUri] List<string> layers)


    name: "DefaultApi",
    routeTemplate: "api/{controller}/{id}/{layers}",
    defaults: new { id = RouteParameter.Optional, layers RouteParameter.Optional }

Can you hide the controls of a YouTube embed without enabling autoplay?

You can hide the "Watch Later" Button by using "Youtube-nocookie" (this will not hide the share Button)

Adding controls=0 will also remove the video control bar at the bottom of the screen and using modestbranding=1 will remove the youtube logo at bottom right of the screen

However using them both doesn't works as expected (it only hides the video control bar)

<iframe width="100%" height="100%" src="" frameborder="0" allowfullscreen></iframe>

Check if a string is palindrome

Note that reversing the whole string (either with the rbegin()/rend() range constructor or with std::reverse) and comparing it with the input would perform unnecessary work.

It's sufficient to compare the first half of the string with the latter half, in reverse:

#include <string>
#include <algorithm>
#include <iostream>
int main()
    std::string s;
    std::cin >> s;
    if( equal(s.begin(), s.begin() + s.size()/2, s.rbegin()) )
        std::cout << "is a palindrome.\n";
        std::cout << "is NOT a palindrome.\n";


How to open a folder in Windows Explorer from VBA?

Private Sub Command0_Click()

Application.FollowHyperlink "D:\1Zsnsn\SusuBarokah\20151008 Inventory.mdb"

End Sub

Printing the value of a variable in SQL Developer

Make server output on First of all


  2. Go to the DBMS Output window (View->DBMS Output)

  3. then Press Ctrl+N for connecting server

Command line tool to dump Windows DLL version?

You can also look at filever.exe, which can be downloaded as part of the Windows XP SP2 Support Tools package - only 4.7MB of download.

Access restriction: The type 'Application' is not API (restriction on required library rt.jar)

In Eclipse Mars.2 Release (4.5.2):
Project Explorer -> Context menu -> Properties -> JavaBuildPath -> Libraries
select JRE... and press Edit: Switch to Workspace JRE (jdk1.8.0_77)

Works for me.

Replace X-axis with own values

Yo could also set labels = FALSE inside axis(...) and print the labels in a separate command with Text. With this option you can rotate the text the text in case you need it

axis(1, at=seq(1, 10, by=1), labels = FALSE)
text(seq(1, 10, by=1), par("usr")[3] - 0.2, labels = lablist, srt = 45, pos = 1, xpd = TRUE)

Detailed explanation here

Image with rotated labels

Checking if an object is a number in C#

You could use code like this:

if (n is IConvertible)
  return ((IConvertible) n).ToDouble(CultureInfo.CurrentCulture);
  // Cannot be converted.

If your object is an Int32, Single, Double etc. it will perform the conversion. Also, a string implements IConvertible but if the string isn't convertible to a double then a FormatException will be thrown.

error TS2339: Property 'x' does not exist on type 'Y'

The correct fix is to add the property in the type definition as explained in @Nitzan Tomer's answer. If that's not an option though:

(Hacky) Workaround 1

You can assign the object to a constant of type any, then call the 'non-existing' property.

const newObj: any = oldObj;
return newObj.someProperty;

You can also cast it as any:

return (oldObj as any).someProperty;

This fails to provide any type safety though, which is the point of TypeScript.

(Hacky) Workaround 2

Another thing you may consider, if you're unable to modify the original type, is extending the type like so:

interface NewType extends OldType {
  someProperty: string;

Now you can cast your variable as this NewType instead of any. Still not ideal but less permissive than any, giving you more type safety.

return (oldObj as NewType).someProperty;

How to restrict user to type 10 digit numbers in input element?

whoever is checking this post in 2020, they can use <input inputmode="tel"> for phone numbers (10 digit), <input inputmode="numeric" maxLength={5}> for numeric type and restrict to only 5 digits.

Best Practice for Forcing Garbage Collection in C#

However, if you can reliably test your code to confirm that calling Collect() won't have a negative impact then go ahead...

IMHO, this is similar to saying "If you can prove that your program will never have any bugs in the future, then go ahead..."

In all seriousness, forcing the GC is useful for debugging/testing purposes. If you feel like you need to do it at any other times, then either you are mistaken, or your program has been built wrong. Either way, the solution is not forcing the GC...

Weird behavior of the != XPath operator

The problem is that the 'and' is being treated as an 'or'.

No, the problem is that you are using the XPath != operator and you aren't aware of its "weird" semantics.


Just replace the any x != y expressions with a not(x = y) expression.

In your specific case:


<xsl:when test="$AccountNumber != '12345' and $Balance != '0'">


<xsl:when test="not($AccountNumber = '12345') and not($Balance = '0')">


By definition whenever one of the operands of the != operator is a nodeset, then the result of evaluating this operator is true if there is a node in the node-set, whose value isn't equal to the other operand.


 $someNodeSet != $someValue

generally doesn't produce the same result as:

 not($someNodeSet = $someValue)

The latter (by definition) is true exactly when there isn't a node in $someNodeSet whose string value is equal to $someValue.

Lesson to learn:

Never use the != operator, unless you are absolutely sure you know what you are doing.

What are Maven goals and phases and what is their difference?

There are following three built-in build lifecycles:

  • default
  • clean
  • site

Lifecycle default -> [validate, initialize, generate-sources, process-sources, generate-resources, process-resources, compile, process-classes, generate-test-sources, process-test-sources, generate-test-resources, process-test-resources, test-compile, process-test-classes, test, prepare-package, package, pre-integration-test, integration-test, post-integration-test, verify, install, deploy]

Lifecycle clean -> [pre-clean, clean, post-clean]

Lifecycle site -> [pre-site, site, post-site, site-deploy]

The flow is sequential, for example, for default lifecycle, it starts with validate, then initialize and so on...

You can check the lifecycle by enabling debug mode of mvn i.e., mvn -X <your_goal>

How do you select a particular option in a SELECT element in jQuery?

For Jquery chosen if you send the attribute to function and need to update-select option

$('#yourElement option[value="'+yourValue+'"]').attr('selected', 'selected');


Try this:

Update TableB Set
  Code = Coalesce(
    (Select Max(Value)
    From TableA 
    Where Id = b.Id), 123)
From TableB b

How to extract hours and minutes from a datetime.datetime object?

It's easier to use the timestamp for this things since Tweepy gets both

import datetime

Exit/save edit to sudoers file? Putty SSH

Just open file by nano /file_name

Once done, press CTRL+O and then Enter to save. Then press CTRL+X to return.

Here CTRL+O : is CTRL and O for Orange Not 0 Zero

Why does JPA have a @Transient annotation?

For Kotlin developers, remember the Java transient keyword becomes the built-in Kotlin @Transient annotation. Therefore, make sure you have the JPA import if you're using JPA @Transient in your entity:

import javax.persistence.Transient

Parse an HTML string with JS

It's quite simple:

var parser = new DOMParser();
var htmlDoc = parser.parseFromString(txt, 'text/html');
// do whatever you want with htmlDoc.getElementsByTagName('a');

According to MDN, to do this in chrome you need to parse as XML like so:

var parser = new DOMParser();
var htmlDoc = parser.parseFromString(txt, 'text/xml');
// do whatever you want with htmlDoc.getElementsByTagName('a');

It is currently unsupported by webkit and you'd have to follow Florian's answer, and it is unknown to work in most cases on mobile browsers.

Edit: Now widely supported

Convert UNIX epoch to Date object

With library(lubridate), numeric representations of date and time saved as the number of seconds since 1970-01-01 00:00:00 UTC, can be coerced into dates with as_datetime():


[1] "2012-11-04 22:32:00 UTC"

What should my Objective-C singleton look like?

How about

static MyClass *gInstance = NULL;

+ (MyClass *)instance
    if (gInstance == NULL) {
            if (gInstance == NULL)
                gInstance = [[self alloc] init];


So you avoid the synchronization cost after initialization?

How do you properly use WideCharToMultiByte

You use the lpMultiByteStr [out] parameter by creating a new char array. You then pass this char array in to get it filled. You only need to initialize the length of the string + 1 so that you can have a null terminated string after the conversion.

Here are a couple of useful helper functions for you, they show the usage of all parameters.

#include <string>

std::string wstrtostr(const std::wstring &wstr)
    // Convert a Unicode string to an ASCII string
    std::string strTo;
    char *szTo = new char[wstr.length() + 1];
    szTo[wstr.size()] = '\0';
    WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), -1, szTo, (int)wstr.length(), NULL, NULL);
    strTo = szTo;
    delete[] szTo;
    return strTo;

std::wstring strtowstr(const std::string &str)
    // Convert an ASCII string to a Unicode String
    std::wstring wstrTo;
    wchar_t *wszTo = new wchar_t[str.length() + 1];
    wszTo[str.size()] = L'\0';
    MultiByteToWideChar(CP_ACP, 0, str.c_str(), -1, wszTo, (int)str.length());
    wstrTo = wszTo;
    delete[] wszTo;
    return wstrTo;


Anytime in documentation when you see that it has a parameter which is a pointer to a type, and they tell you it is an out variable, you will want to create that type, and then pass in a pointer to it. The function will use that pointer to fill your variable.

So you can understand this better:

//pX is an out parameter, it fills your variable with 10.
void fillXWith10(int *pX)
  *pX = 10;

int main(int argc, char ** argv)
  int X;
  return 0;

How do I download the Android SDK without downloading Android Studio?

I downloaded Android Studio and installed it. The installer said:-

Android Studio => ( 500 MB )

Android SDK => ( 2.3 GB )

Android Studio installer is actually an "Android SDK Installer" along with a sometimes useful tool called "Android Studio".

Most importantly:- Android Studio Installer will not just install the SDK. It will also:-

  • Install the latest build-tools.
  • Install the latest platform-tools.
  • Install the latest AVD Manager which you cannot do without.

Things which you will have to do manually if you install the SDK from its zip file.

Just take it easy. Install the Android Studio.

****************************** Edit ******************************

So, being inspired by the responses in the comments I would like to update my answer.

The update is that only (and only) if 500MB of hard disk space does not matter much to you than you should go for Android Studio otherwise other answers would be better for you.

Android Studio worked for me as I had a 1TB hard disk which is 2000 times 500MB.

Also, note: that RAM sizse should not a restriction for you as you would not even be running Android Studio.

I came to this solution as I was myself stuck in this problem. I tried other answers but for some reason (maybe my in-competencies) they did not work for me. I decided to go for Android Studio and realized that it was merely 18% of the total installation and SDK was 82% of it. While I used to think otherwise. I am not deleting the answers inspite of negative rating as the answer worked for me. I might work for someone elese with a 1 TB hard disk (which is pretty common these days).

What is the equivalent of Java's System.out.println() in Javascript?


Chrome, Safari, and IE 8+ come with built-in consoles (as part of a larger set of development tools). If you're using Firefox,

Get div tag scroll position using JavaScript

you use the scrollTop attribute

var position = document.getElementById('id').scrollTop;

Drop shadow on a div container?

This works for me on all my browsers:

.shadow {
-moz-box-shadow: 0 0 30px 5px #999;
-webkit-box-shadow: 0 0 30px 5px #999;

then just give any div the shadow class, no jQuery required.

Python BeautifulSoup extract text between element

with your own soup object:

  1. you grab the <p> directly with soup.p *(this hinges on it being the first <p> in the parse tree)
  2. then use next_sibling on the tag object that soup.p returns since the desired text is nested at the same level of the parse tree as the <p>
  3. .strip() is just a Python str method to remove leading and trailing whitespace

*otherwise just find the element using your choice of filter(s)

in the interpreter this looks something like:

In [4]: soup.p
Out[4]: <p>something</p>

In [5]: type(soup.p)
Out[5]: bs4.element.Tag

In [6]: soup.p.next_sibling
Out[6]: u'\n      THIS IS MY TEXT\n      '

In [7]: type(soup.p.next_sibling)
Out[7]: bs4.element.NavigableString

In [8]: soup.p.next_sibling.strip()
Out[8]: u'THIS IS MY TEXT'

In [9]: type(soup.p.next_sibling.strip())
Out[9]: unicode

Android webview launches browser when calling loadurl

Try this code...

private void startWebView(String url) {

    //Create new webview Client to show progress dialog
    //When opening a url or click on link

    webView.setWebViewClient(new WebViewClient() {      
        ProgressDialog progressDialog;

        //If you will not use this method url links are opeen in new brower not in webview
        public boolean shouldOverrideUrlLoading(WebView view, String url) {              
            return true;

        //Show loader on url load
        public void onLoadResource (final WebView view, String url) {
            if (progressDialog == null) {
                // in standard case YourActivity.this
                progressDialog = new ProgressDialog(view.getContext());
        public void onPageFinished(WebView view, String url) {
            if (progressDialog.isShowing()) {
                progressDialog = null;
            }catch(Exception exception){


     // Javascript inabled on webview  

    // Other webview options

     String summary = "<html><body>You scored <b>192</b> points.</body></html>";
     webview.loadData(summary, "text/html", null); 

    //Load url in webview

How do I drop a foreign key constraint only if it exists in sql server?

ALTER TABLE [dbo].[TableName]
    DROP CONSTRAINT FK_TableName_TableName2

Pass Javascript Variable to PHP POST

You can do this using Ajax. I have a function that I use for something like this:

function ajax(elementID,filename,str,post)
    var ajax;
    if (window.XMLHttpRequest)
        ajax=new XMLHttpRequest();//IE7+, Firefox, Chrome, Opera, Safari
    else if (ActiveXObject("Microsoft.XMLHTTP"))
        ajax=new ActiveXObject("Microsoft.XMLHTTP");//IE6/5
    else if (ActiveXObject("Msxml2.XMLHTTP"))
        ajax=new ActiveXObject("Msxml2.XMLHTTP");//other
        alert("Error: Your browser does not support AJAX.");
        return false;
        if (ajax.readyState==4&&ajax.status==200)
    if (post==false)
    return ajax;

The first parameter is the element you want to change. The second parameter is the name of the filename you're loading into the element you're changing. The third parameter is the GET or POST data you're using, so for example "total=10000&othernumber=999". The last parameter is true if you want use POST or false if you want to GET.

Write-back vs Write-Through caching?

Write-Back is a more complex one and requires a complicated Cache Coherence Protocol(MOESI) but it is worth it as it makes the system fast and efficient.

The only benefit of Write-Through is that it makes the implementation extremely simple and no complicated cache coherency protocol is required.

How can I stop python.exe from closing immediately after I get an output?

You can't - globally, i.e. for every python program. And this is a good thing - Python is great for scripting (automating stuff), and scripts should be able to run without any user interaction at all.

However, you can always ask for input at the end of your program, effectively keeping the program alive until you press return. Use input("prompt: ") in Python 3 (or raw_input("promt: ") in Python 2). Or get used to running your programs from the command line (i.e. python, the program will exit but its output remains visible.

Good font for code presentations?

  • Lucida Console (good, but a little short)
  • Lucida Sans Typewriter (taller, smaller character set)
  • Andale Mono is very clear

But this has been answered here before.

This version of Android Studio cannot open this project, please retry with Android Studio 3.4 or newer

in project's build.gradle file comment classpath File ? Project Structure select Android Gradle Plugin Version to match Android Studio version

Project Structure

CSS Custom Dropdown Select that works across all browsers IE7+ FF Webkit

The pointer-events could be useful for this problem as you would be able to put a div over the arrow button, but still be able to click the arrow button.

The pointer-events css makes it possible to click through a div.

This approach will not work for IE versions older than IE11, however. You could something working in IE8 and IE9 if the element you put on top of the arrow button is an SVG element, but it will be more complicated to style the button the way you want proceeding like this.

Here a Js fiddle example:

Auto-refreshing div with jQuery - setTimeout or another method?

$(document).ready(function() {
  $.ajaxSetup({ cache: false }); // This part addresses an IE bug.  without it, IE will only load the first number and will never refresh
  setInterval(function() {
  }, 3000); // the "3000" 

CONVERT Image url to Base64

imageToBase64 = (URL) => {
    let image;
    image = new Image();
    image.crossOrigin = 'Anonymous';
    image.addEventListener('load', function() {
        let canvas = document.createElement('canvas');
        let context = canvas.getContext('2d');
        canvas.width = image.width;
        canvas.height = image.height;
        context.drawImage(image, 0, 0);
        try {
            localStorage.setItem('saved-image-example', canvas.toDataURL('image/png'));
        } catch (err) {
    image.src = URL;

imageToBase64('image URL')

Why is setTimeout(fn, 0) sometimes useful?

The problem was you were trying to perform a Javascript operation on a non existing element. The element was yet to be loaded and setTimeout() gives more time for an element to load in the following ways:

  1. setTimeout() causes the event to be ansynchronous therefore being executed after all the synchronous code, giving your element more time to load. Asynchronous callbacks like the callback in setTimeout() are placed in the event queue and put on the stack by the event loop after the stack of synchronous code is empty.
  2. The value 0 for ms as a second argument in function setTimeout() is often slightly higher (4-10ms depending on browser). This slightly higher time needed for executing the setTimeout() callbacks is caused by the amount of 'ticks' (where a tick is pushing a callback on the stack if stack is empty) of the event loop. Because of performance and battery life reasons the amount of ticks in the event loop are restricted to a certain amount less than 1000 times per second.

How to query MongoDB with "like"?

There are various ways to accomplish this.


db.users.find({"name": /m/})

{ <field>: { $regex: /pattern/, $options: '<options>' } }
{ <field>: { $regex: 'pattern', $options: '<options>' } }
{ <field>: { $regex: /pattern/<options> } }

db.users.find({ "name": { $regex: "m"} })

More details can be found here

curl posting with header application/x-www-form-urlencoded

 $curl = curl_init();
 curl_setopt_array($curl, array(
            CURLOPT_URL => "",
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_ENCODING => "",
            CURLOPT_MAXREDIRS => 10,
            CURLOPT_TIMEOUT => 30,
            CURLOPT_POSTFIELDS => "value1=111&value2=222",
            CURLOPT_HTTPHEADER => array(
                "cache-control: no-cache",
                "content-type: application/x-www-form-urlencoded"
 $response = curl_exec($curl);
 $err = curl_error($curl);


 if (!$err)

How to sort findAll Doctrine's method?

You need to use a criteria, for example:


namespace Bundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Request;
use Doctrine\Common\Collections\Criteria;

* Thing controller
class ThingController extends Controller
    public function thingsAction(Request $request, $id)
        $criteria = new Criteria(null, <<DQL ordering expression>>, null, null );

        $rep    = $this->getDoctrine()->getManager()->getRepository('Bundle:Thing');
        $things = $rep->matching($criteria);
        return $this->render('Bundle:Thing:things.html.twig', [
            'entities' => $things,

Test for multiple cases in a switch, like an OR (||)

Forget switch and break, lets play with if. And instead of asserting

if(pageid === "listing-page" || pageid === "home-page")

lets create several arrays with cases and check it with Array.prototype.includes()

var caseA = ["listing-page", "home-page"];
var caseB = ["details-page", "case04", "case05"];

if(caseA.includes(pageid)) {
else if (caseB.includes(pageid)) {
else {
    alert("there is no else case");

Angular 2 http post params and body

And it works, thanks @trichetriche. The problem was in my RequestOptions, apparently, you can not pass params or body to the RequestOptions while using the post. Removing one of them gives me an error, removing both and it works. Still no final solution to my problem, but I now have something to work with. Final working code.

public post(cmd: string, data: string): Observable<any> {

    const options = new RequestOptions({
      headers: this.getAuthorizedHeaders(),
      responseType: ResponseContentType.Json,
      withCredentials: false

    console.log('Options: ' + JSON.stringify(options));

    return, JSON.stringify({
      cmd: cmd,
      data: data}), options)

Can an Android Toast be longer than Toast.LENGTH_LONG?

Sets toast to a specific period in milli-seconds:

public void toast(int millisec, String msg) {
    Handler handler = null;
    final Toast[] toasts = new Toast[1];
    for(int i = 0; i < millisec; i+=2000) {
        toasts[0] = Toast.makeText(this, msg, Toast.LENGTH_SHORT);
        if(handler == null) {
            handler = new Handler();
            handler.postDelayed(new Runnable() {
                public void run() {
            }, millisec);

jQuery UI Dialog Box - does not open after being closed

For me this approach works:

The dialog may be closed by clicking the X on the dialog or by clicking 'Bewaren'. I'm adding an (arbitrary) id because I need to be sure every bit of html added to the dom is removed afterwards.

$('<div id="dossier_edit_form_tmp_id">').html(data.form)
        title: 'Opdracht wijzigen',
        show: 'clip',
        hide: 'clip',
        minWidth: 520,
        width: 520,
        modal: true,
        buttons: { 'Bewaren': dossier_edit_form_opslaan },
        close: function(event, ui){ 

Check to see if cURL is installed locally?

In the Terminal, type:

$ curl -V

That's a capital V for the version

How to run multiple Python versions on Windows

I thought this answer might be helpful to others having multiple versions of python and wants to use pipenv to create virtual environment.

  1. navigate to the project directory, and run py -[python version] pip install pipenv, example: py -3.6 pip install pipenv
  2. run pipenv --python [version] to create the virtual environment in the version of the python you desire. example: pipenv --python 3.6
  3. run pipenv shell to activate your virtual environment.

Regex lookahead, lookbehind and atomic groups

Lookarounds are zero width assertions. They check for a regex (towards right or left of the current position - based on ahead or behind), succeeds or fails when a match is found (based on if it is positive or negative) and discards the matched portion. They don't consume any character - the matching for regex following them (if any), will start at the same cursor position.

Read for more details.

  • Positive lookahead:



Match only if REGEX_1 matches; after matching REGEX_1, the match is discarded and searching for REGEX_2 starts at the same position.



REGEX_1 is [a-z0-9]{4}$ which matches four alphanumeric chars followed by end of line.
REGEX_2 is [a-z]{1,2}[0-9]{2,3} which matches one or two letters followed by two or three digits.

REGEX_1 makes sure that the length of string is indeed 4, but doesn't consume any characters so that search for REGEX_2 starts at the same location. Now REGEX_2 makes sure that the string matches some other rules. Without look-ahead it would match strings of length three or five.

  • Negative lookahead



Match only if REGEX_1 does not match; after checking REGEX_1, the search for REGEX_2 starts at the same position.



The look-ahead part checks for the FWORD in the string and fails if it finds it. If it doesn't find FWORD, the look-ahead succeeds and the following part verifies that the string's length is between 10 and 30 and that it contains only word characters a-zA-Z0-9_

Look-behind is similar to look-ahead: it just looks behind the current cursor position. Some regex flavors like javascript doesn't support look-behind assertions. And most flavors that support it (PHP, Python etc) require that look-behind portion to have a fixed length.

  • Atomic groups basically discards/forgets the subsequent tokens in the group once a token matches. Check this page for examples of atomic groups

Simplest way to detect a pinch

None of these answers achieved what I was looking for, so I wound up writing something myself. I wanted to pinch-zoom an image on my website using my MacBookPro trackpad. The following code (which requires jQuery) seems to work in Chrome and Edge, at least. Maybe this will be of use to someone else.

function setupImageEnlargement(el)
    // "el" represents the image element, such as the results of document.getElementByd('image-id')
    var img = $(el);
    $(window, 'html', 'body').bind('scroll touchmove mousewheel', function(e)
        //TODO: need to limit this to when the mouse is over the image in question

        //TODO: behavior not the same in Safari and FF, but seems to work in Edge and Chrome

        if (typeof e.originalEvent != 'undefined' && e.originalEvent != null
            && e.originalEvent.wheelDelta != 'undefined' && e.originalEvent.wheelDelta != null)
            if (e.originalEvent.wheelDelta > 0)
                // zooming
                var newW = 1.1 * parseFloat(img.width());
                var newH = 1.1 * parseFloat(img.height());
                if (newW < el.naturalWidth && newH < el.naturalHeight)
                    // Go ahead and zoom the image
                    //console.log('zooming the image');
                        "width": newW + 'px',
                        "height": newH + 'px',
                        "max-width": newW + 'px',
                        "max-height": newH + 'px'
                    // Make image as big as it gets
                    //console.log('making it as big as it gets');
                        "width": el.naturalWidth + 'px',
                        "height": el.naturalHeight + 'px',
                        "max-width": el.naturalWidth + 'px',
                        "max-height": el.naturalHeight + 'px'
            else if (e.originalEvent.wheelDelta < 0)
                // shrinking
                var newW = 0.9 * parseFloat(img.width());
                var newH = 0.9 * parseFloat(img.height());

                //TODO: I had added these data-attributes to the image onload.
                // They represent the original width and height of the image on the screen.
                // If your image is normally 100% width, you may need to change these values on resize.
                var origW = parseFloat(img.attr('data-startwidth'));
                var origH = parseFloat(img.attr('data-startheight'));

                if (newW > origW && newH > origH)
                    // Go ahead and shrink the image
                    //console.log('shrinking the image');
                        "width": newW + 'px',
                        "height": newH + 'px',
                        "max-width": newW + 'px',
                        "max-height": newH + 'px'
                    // Make image as small as it gets
                    //console.log('making it as small as it gets');
                    // This restores the image to its original size. You may want
                    //to do this differently, like by removing the css instead of defining it.
                        "width": origW + 'px',
                        "height": origH + 'px',
                        "max-width": origW + 'px',
                        "max-height": origH + 'px'

What is the maximum length of a valid email address?

TLDR Answer

Given an email address like...

[email protected]

The length limits are as follows:

  • Entire Email Address (aka: "The Path"): i.e., [email protected] -- 256 characters maximum.
  • Local-Part: i.e., me -- 64 character maximum.
  • Domain: i.e., -- 254 characters maximum.


SMTP originally defined what a path was in RFC821, published August 1982, which is an official Internet Standard (most RFC's are only proposals). To quote it...

...a reverse-path, specifies who the mail is from.

...a forward-path, which specifies who the mail is to.

RFC2821, published in April 2001, is the Obsoleted Standard that defined our present maximum values for local-parts, domains, and paths. A new Draft Standard, RFC5321, published in October 2008, keeps the same limits. In between these two dates, RFC3696 was published, on February 2004. It mistakenly cites the maximum email address limit as 320-characters, but this document is "Informational" only, and states: "This memo provides information for the Internet community. It does not specify an Internet standard of any kind." So, we can disregard it.

To quote RFC2821, the modern, accepted standard as confirmed in RFC5321... Local-part

The maximum total length of a user name or other local-part is 64 characters. Domain

The maximum total length of a domain name or number is 255 characters. Path

The maximum total length of a reverse-path or forward-path is 256 characters (including the punctuation and element separators).

You'll notice that I indicate a domain maximum of 254 and the RFC indicates a domain maximum of 255. It's a matter of simple arithmetic. A 255-character domain, plus the "@" sign, is a 256-character path, which is the max path length. An empty or blank name is invalid, though, so the domain actually has a maximum of 254.

Pytorch tensor to numpy array

While other answers perfectly explained the question I will add some real life examples converting tensors to numpy array:

Example: Shared storage

PyTorch tensor residing on CPU shares the same storage as numpy array na

import torch
a = torch.ones((1,2))
na = a.numpy()


tensor([[1., 1.]])
[[10.  1.]]
tensor([[10.,  1.]])

Example: Eliminate effect of shared storage, copy numpy array first

To avoid the effect of shared storage we need to copy() the numpy array na to a new numpy array nac. Numpy copy() method creates the new separate storage.

import torch
a = torch.ones((1,2))
na = a.numpy()
nac = na.copy()


tensor([[1., 1.]])
[[10.  1.]]
[[1. 1.]]
tensor([[1., 1.]])

Now, just the nac numpy array will be altered with the line nac[0][0]=10, na and a will remain as is.

Example: CPU tensor with requires_grad=True

import torch
a = torch.ones((1,2), requires_grad=True)
na = a.detach().numpy()


tensor([[1., 1.]], requires_grad=True)
[[10.  1.]]
tensor([[10.,  1.]], requires_grad=True)

In here we call:

na = a.numpy() 

This would cause: RuntimeError: Can't call numpy() on Tensor that requires grad. Use tensor.detach().numpy() instead., because tensors that require_grad=True are recorded by PyTorch AD. Note that tensor.detach() is the new way for

This explains why we need to detach() them first before converting using numpy().

Example: CUDA tensor with requires_grad=False

a = torch.ones((1,2), device='cuda')
na ='cpu').numpy()


tensor([[1., 1.]], device='cuda:0')
[[10.  1.]]
tensor([[1., 1.]], device='cuda:0')


Example: CUDA tensor with requires_grad=True

a = torch.ones((1,2), device='cuda', requires_grad=True)
na = a.detach().to('cpu').numpy()


tensor([[1., 1.]], device='cuda:0', requires_grad=True)
[[10.  1.]]
tensor([[1., 1.]], device='cuda:0', requires_grad=True)

Without detach() method the error RuntimeError: Can't call numpy() on Tensor that requires grad. Use tensor.detach().numpy() instead. will be set.

Without .to('cpu') method TypeError: can't convert cuda:0 device type tensor to numpy. Use Tensor.cpu() to copy the tensor to host memory first. will be set.

You could use cpu() but instead of to('cpu') but I prefer the newer to('cpu').

How to get the browser to navigate to URL in JavaScript

Try these:

  1. window.location.href = '';
  2. window.location.assign("");
  3. window.location = '';

For more see this link: other ways to reload the page with JavaScript

#1273 - Unknown collation: 'utf8mb4_unicode_ci' cPanel

After the long time research i have found the solution for above:

  1. Firstly you change the wp-config.php> Database DB_CHARSET default to "utf8"

  2. Click the "Export" tab for the database

  3. Click the "Custom" radio button

  4. Go the section titled "Format-specific options" and change the dropdown for "Database system or older MySQL server to maximize output compatibility with:" from NONE to MYSQL40.

  5. Scroll to the bottom and click go

Then you are on.

Facebook Graph API : get larger pictures in one request

rest-fb users (square image, bigger res.): Connection myFriends = fbClient.fetchConnection("me/friends", User.class, Parameter.with("fields", "public_profile,email,first_name,last_name,gender,picture.width(100).height(100)"));

Alternate table with new not null Column in existing table in SQL

There are two ways to add the NOT NULL Columns to the table :

  1. ALTER the table by adding the column with NULL constraint. Fill the column with some data. Ex: column can be updated with ''

  2. ALTER the table by adding the column with NOT NULL constraint by giving DEFAULT values. ALTER table TableName ADD NewColumn DataType NOT NULL DEFAULT ''

How can you run a Java program without main method?

Applets from what I remember do not need a main method, though I am not sure they are technically a program.

How do I put my website's logo to be the icon image in browser tabs?

<link rel="apple-touch-icon" sizes="114x114" href="${resource(dir: 'images', file: 

or you can use this one

<link rel="shortcut icon" sizes="114x114" href="${resource(dir: 'images', file: 'favicon.ico')}"

How do I fix the error 'Named Pipes Provider, error 40 - Could not open a connection to' SQL Server'?

If you are working with core and using appsettings.json than write server as localhost and after write sql instance name for enabled named pipe like this

  "ConnectionString": {
    "dewDB": "server=localhost\\dewelopersql;database=dewdb;User ID=sa;password=XXXXX",

Getting Spring Application Context

If you use a web-app there is also another way to access the application context without using singletons by using a servletfilter and a ThreadLocal. In the filter you can access the application context using WebApplicationContextUtils and store either the application context or the needed beans in the TheadLocal.

Caution: if you forget to unset the ThreadLocal you will get nasty problems when trying to undeploy the application! Thus, you should set it and immediately start a try that unsets the ThreadLocal in the finally-part.

Of course, this still uses a singleton: the ThreadLocal. But the actual beans do not need to be anymore. The can even be request-scoped, and this solution also works if you have multiple WARs in an Application with the libaries in the EAR. Still, you might consider this use of ThreadLocal as bad as the use of plain singletons. ;-)

Perhaps Spring already provides a similar solution? I did not find one, but I don't know for sure.

What are Long-Polling, Websockets, Server-Sent Events (SSE) and Comet?

You can easily use Node.JS in your web app only for real-time communication. Node.JS is really powerful when it's about WebSockets. Therefore "PHP Notifications via Node.js" would be a great concept.

See this example: Creating a Real-Time Chat App with PHP and Node.js

How to embed a YouTube channel into a webpage

YouTube supports a fairly easy to use iframe and url interface to embed videos, playlists and all user uploads to your channel:

For example this HTML will embed a player loaded with a playlist of all the videos uploaded to your channel. Replace YOURCHANNELNAME with the actual name of your channel:

<iframe src="" width="480" height="400"></iframe>

java.lang.ClassNotFoundException: org.springframework.boot.SpringApplication Maven

Mine was caused by a corrupt Maven repository.

I deleted everything under C:\Users\<me>\.m2\repository.

Then did an Eclipse Maven Update, and it worked first time.

So it was simply spring-boot.jar got corrupted.

How to find a hash key containing a matching value

try this:

clients.find{|key,value| value["client_id"] == "2178"}.first

What does "@" mean in Windows batch scripts

The @ disables echo for that one command. Without it, the echo start eclipse.exe line would print both the intended start eclipse.exe and the echo start eclipse.exe line.

The echo off turns off the by-default command echoing.

So @echo off silently turns off command echoing, and only output the batch author intended to be written is actually written.

Copy folder recursively, excluding some folders

inspired by @SteveLazaridis's answer, which would fail, here is a POSIX shell function - just copy and paste into a file named cpx in yout $PATH and make it executible (chmod a+x cpr). [Source is now maintained in my GitLab.


# usage: cpx [-n|--dry-run] "from_path" "to_path" "newline_separated_exclude_list"
# limitations: only excludes from "from_path", not it's subdirectories

cpx() {
# run in subshell to avoid collisions
  (_CopyWithExclude "$@")

_CopyWithExclude() {
  case "$1" in
    -n|--dry-run) { DryRun='echo'; shift; } ;;


  $DryRun mkdir -p "$to"

  if [ -z "$exclude" ]; then
      cp "$from" "$to"

  ls -A1 "$from" \
    | while IFS= read -r f; do
        unset excluded
        if [ -n "$exclude" ]; then
          for x in $(printf "$exclude"); do
          if [ "$f" = "$x" ]; then
        if [ -z "$excluded" ]; then
          $DryRun cp -R "$f" "$to"
          [ -n "$DryRun" ] && echo "skip '$f'"

# Do not execute if being sourced
[ "${0#*cpx}" != "$0" ] && cpx "$@"

Example usage

cpr "$HOME/my_stuff" "/media/usb" "$EXCLUDE"

python pandas dataframe columns convert to dict key and value

With pandas it can be done as:

If lakes is your DataFrame:

area_dict = lakes.to_dict('records')

Android Studio rendering problems

In the Latest Android Studio 3.1.3, Dependency:

implementation ''


Even in latest by 27th of Aug 18 ie

implementation '' facing similar issue

Change it to

    implementation '

This will solve your problem of Preview.


Still, in beta01 there is a preview problem for latest appcompact v7 library make the above change as changing it to alpha01 for solving rendering problem

isset PHP isset($_GET['something']) ? $_GET['something'] : ''

In PHP 7 you can write it even shorter:

$age = $_GET['age'] ?? 27;

This means that the $age variable will be set to the age parameter if it is provided in the URL, or it will default to 27.

See all new features of PHP 7.

The ResourceConfig instance does not contain any root resource classes

Same issue - web.xml looked like this:


Providing a custom application overrides any XML configured auto detection of classes. You need to implement the right methods to write your own code to wire up the classes. See the javadocs.

How to preserve insertion order in HashMap?

HashMap is unordered per the second line of the documentation:

This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.

Perhaps you can do as aix suggests and use a LinkedHashMap, or another ordered collection. This link can help you find the most appropriate collection to use.

Firefox Add-on RESTclient - How to input POST parameters?

Here is a step by step guide (I think this should come pre-loaded with the add-on):

  1. In the top menu of RESTClient -> Headers -> Custom Header
  2. In the pop-up box, enter Name: Content-Type and Value: application/x-www-form-urlencoded
  3. Check the "Save to favorite" box and click Okay.
    Now you will see a "Headers" section with your newly added data.
  4. Then in the Body section, you can enter your data to post like:

  5. Whenever you want to make a post request, from the Headers main menu, select the Content-Type:application/x-www-form-urlencoded item that you added and it should work.

Datatable vs Dataset

in 1.x there used to be things DataTables couldn't do which DataSets could (don't remember exactly what). All that was changed in 2.x. My guess is that's why a lot of examples still use DataSets. DataTables should be quicker as they are more lightweight. If you're only pulling a single resultset, its your best choice between the two.

Filter element based on .data() key/value

your filter would work, but you need to return true on matching objects in the function passed to the filter for it to grab them.

var $previous = $('.navlink').filter(function() { 
  return $(this).data("selected") == true 

How to make rpm auto install dependencies

Simple just run the following command.

sudo dnf install *package.rpm

Enter your password and you are done.

Free Online Team Foundation Server

You can use Visual Studio Team Services for free. Also you can import a TFS repo to this cloud space.

How to make primary key as autoincrement for Room Persistence lib

@Entity(tableName = "user")
data class User(

@PrimaryKey(autoGenerate = true)  var id: Int?,
       var name: String,
       var dob: String,
       var address: String,
       var gender: String

Could not load file or assembly "System.Net.Http, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"

This will work in .NET 4.7.2 with Visual Studio 2017 (15.9.4):

  • Remove web/app.config binding redirects
  • Remove NuGet package for System.Net.Http
  • Open "Add New Reference" and directly link to the new build that ships with .NET 4.7.2


Prevent browser caching of AJAX call result

Of course "cache-breaking" techniques will get the job done, but this would not happen in the first place if the server indicated to the client that the response should not be cached. In some cases it is beneficial to cache responses, some times not. Let the server decide the correct lifetime of the data. You may want to change it later. Much easier to do from the server than from many different places in your UI code.

Of course this doesn't help if you have no control over the server.

How to add and remove item from array in components in Vue 2

There are few mistakes you are doing:

  1. You need to add proper object in the array in addRow method
  2. You can use splice method to remove an element from an array at particular index.
  3. You need to pass the current row as prop to my-item component, where this can be modified.

You can see working code here.

   this.rows.push({description: '', unitprice: '' , code: ''}); // what to push unto the rows array?
   this. itemList.splice(index, 1)

How do I use an INSERT statement's OUTPUT clause to get the identity value?

You can either have the newly inserted ID being output to the SSMS console like this:

INSERT INTO MyTable(Name, Address, PhoneNo)
VALUES ('Yatrix', '1234 Address Stuff', '1112223333')

You can use this also from e.g. C#, when you need to get the ID back to your calling app - just execute the SQL query with .ExecuteScalar() (instead of .ExecuteNonQuery()) to read the resulting ID back.

Or if you need to capture the newly inserted ID inside T-SQL (e.g. for later further processing), you need to create a table variable:


INSERT INTO MyTable(Name, Address, PhoneNo)
VALUES ('Yatrix', '1234 Address Stuff', '1112223333')

This way, you can put multiple values into @OutputTbl and do further processing on those. You could also use a "regular" temporary table (#temp) or even a "real" persistent table as your "output target" here.

How to mkdir only if a directory does not already exist?

If you don't want to show any error message:

[ -d newdir ] || mkdir newdir

If you want to show your own error message:

[ -d newdir ] && echo "Directory Exists" || mkdir newdir

posting hidden value

You should never assume register_global_variables is turned on. Even if it is, it's deprecated and you should never use it that way.

Refer directly to the $_POST or $_GET variables. Most likely your form is POSTing, so you'd want your code to look something along the lines of this:

<input type="hidden" name="date" id="hiddenField" value="<?php echo $_POST['date'] ?>" />

If this doesn't work for you right away, print out the $_POST or $_GET variable on the page that would have the hidden form field and determine exactly what you want and refer to it.

echo "<pre>";
echo "</pre>";

Find duplicate values in R

A terser way, either with rev :

x[!(!duplicated(x) & rev(!duplicated(rev(x))))]

... rather than fromLast:

x[!(!duplicated(x) & !duplicated(x, fromLast = TRUE))]

... and as a helper function to provide either logical vector or elements from original vector :

duplicates <- function(x, as.bool = FALSE) {
    is.dup <- !(!duplicated(x) & rev(!duplicated(rev(x))))
    if (as.bool) { is.dup } else { x[is.dup] }

Treating vectors as data frames to pass to table is handy but can get difficult to read, and the data.table solution is fine but I'd prefer base R solutions for dealing with simple vectors like IDs.

How to call a PHP function on the click of a button

To show $message in your input:

        $message= "The insert function is called.";
        $message="The select function is called.";

<form  method="post">
    <input type="text" name="txt" value="<?php if(isset($message)){ echo $message;}?>" >
    <input type="submit" name="insert" value="insert">
    <input type="submit" name="select" value="select" >

To use functioncalling.php as an external file you have to include it somehow in your HTML document.

How to uninstall Eclipse?

The steps are very simple and it'll take just few mins. 1.Go to your C drive and in that go to the 'USER' section. 2.Under 'USER' section go to your 'name(e.g-'user1') and then find ".eclipse" folder and delete that folder 3.Along with that folder also delete "eclipse" folder and you can find that you're work has been done completely.

iTunes Connect: How to choose a good SKU?

You are able to choose one that you like, but it has to be unique.

Every time I have to enter the SKU I use the App identifier (e.g. de.mycompany.myappname) because this is already unique.

How can I check if my python object is a number?

Sure you can use isinstance, but be aware that this is not how Python works. Python is a duck typed language. You should not explicitly check your types. A TypeError will be raised if the incorrect type was passed.

So just assume it is an int. Don't bother checking.

Boolean vs boolean in Java

Basically boolean represent a primitive data type where Boolean represent a reference data type. this story is started when Java want to become purely object oriented it's provided wrapper class concept to over come to use of primitive data type.

boolean b1;
Boolean b2;

b1 and b2 are not same.

in iPhone App How to detect the screen resolution of the device

See the UIScreen Reference:

if([[UIScreen mainScreen] respondsToSelector:NSSelectorFromString(@"scale")])
    if ([[UIScreen mainScreen] scale] < 1.1)
        NSLog(@"Standard Resolution Device");

    if ([[UIScreen mainScreen] scale] > 1.9)
        NSLog(@"High Resolution Device");

Uses of Action delegate in C#

MSDN says:

This delegate is used by the Array.ForEach method and the List.ForEach method to perform an action on each element of the array or list.

Except that, you can use it as a generic delegate that takes 1-3 parameters without returning any value.

Why should we include ttf, eot, woff, svg,... in a font-face

Woff is a compressed (zipped) form of the TrueType - OpenType font. It is small and can be delivered over the network like a graphic file. Most importantly, this way the font is preserved completely including rendering rule tables that very few people care about because they use only Latin script.

Take a look at [dead URL removed]. The font you see is an experimental web delivered smartfont (woff) that has thousands of combined characters making complex shapes. The underlying text is simple Latin code of romanized Singhala. (Copy and paste to Notepad and see).

Only woff can do this because nobody has this font and yet it is seen anywhere (Mac, Win, Linux and even on smartphones by all browsers except by IE. IE does not have full support for Open Types).

Duplicate / Copy records in the same MySQL table

Your approach is good but the problem is that you use "*" instead enlisting fields names. If you put all the columns names excep primary key your script will work like charm on one or many records.

INSERT INTO invoices (iv.field_name, iv.field_name,iv.field_name
) SELECT iv.field_name, iv.field_name,iv.field_name FROM invoices AS iv     

Update one MySQL table with values from another

UPDATE tobeupdated
INNER JOIN original ON (tobeupdated.value = original.value)

That should do it, and really its doing exactly what yours is. However, I prefer 'JOIN' syntax for joins rather than multiple 'WHERE' conditions, I think its easier to read

As for running slow, how large are the tables? You should have indexes on tobeupdated.value and original.value

EDIT: we can also simplify the query

UPDATE tobeupdated
INNER JOIN original USING (value)

USING is shorthand when both tables of a join have an identical named key such as id. ie an equi-join -

PDO's query vs execute

Gilean's answer is great, but I just wanted to add that sometimes there are rare exceptions to best practices, and you might want to test your environment both ways to see what will work best.

In one case, I found that query worked faster for my purposes because I was bulk transferring trusted data from an Ubuntu Linux box running PHP7 with the poorly supported Microsoft ODBC driver for MS SQL Server.

I arrived at this question because I had a long running script for an ETL that I was trying to squeeze for speed. It seemed intuitive to me that query could be faster than prepare & execute because it was calling only one function instead of two. The parameter binding operation provides excellent protection, but it might be expensive and possibly avoided if unnecessary.

Given a couple rare conditions:

  1. If you can't reuse a prepared statement because it's not supported by the Microsoft ODBC driver.

  2. If you're not worried about sanitizing input and simple escaping is acceptable. This may be the case because binding certain datatypes isn't supported by the Microsoft ODBC driver.

  3. PDO::lastInsertId is not supported by the Microsoft ODBC driver.

Here's a method I used to test my environment, and hopefully you can replicate it or something better in yours:

To start, I've created a basic table in Microsoft SQL Server

CREATE TABLE performancetest (
    id INT,
    val VARCHAR(100)

And now a basic timed test for performance metrics.

$logs = [];

$test = function (String $type, Int $count = 3000) use ($pdo, &$logs) {
    $start = microtime(true);
    $i = 0;
    while ($i < $count) {
        $sql = "INSERT INTO performancetest (id, val) OUTPUT INSERTED.sid VALUES ($i,'value $i')";
        if ($type === 'query') {
            $smt = $pdo->query($sql);
        } else {
            $smt = $pdo->prepare($sql);
            $smt ->execute();
        $sid = $smt->fetch(PDO::FETCH_ASSOC)['sid'];
    $total = (microtime(true) - $start);
    $logs[$type] []= $total;
    echo "$total $type\n";

$trials = 15;
$i = 0;
while ($i < $trials) {
    if (random_int(0,1) === 0) {
    } else {

foreach ($logs as $type => $log) {
    $total = 0;
    foreach ($log as $record) {
        $total += $record;
    $count = count($log);
    echo "($count) $type Average: ".$total/$count.PHP_EOL;

I've played with multiple different trial and counts in my specific environment, and consistently get between 20-30% faster results with query than prepare/execute

5.8128969669342 prepare
5.8688418865204 prepare
4.2948560714722 query
4.9533629417419 query
5.9051351547241 prepare
4.332102060318 query
5.9672858715057 prepare
5.0667371749878 query
3.8260300159454 query
4.0791549682617 query
4.3775160312653 query
3.6910600662231 query
5.2708210945129 prepare
6.2671611309052 prepare
7.3791449069977 prepare
(7) prepare Average: 6.0673267160143
(8) query Average: 4.3276024162769

I'm curious to see how this test compares in other environments, like MySQL.

LINUX: Link all files from one to another directory

ln -s /mnt/usr/lib/* /usr/lib/

I guess, this belongs to superuser, though.

Android getText from EditText field

Sample code for How to get text from EditText.

Android Java Syntax

EditText text = (EditText)findViewById(;
String value = text.getText().toString();

Kotlin Syntax

val text = findViewById<View>( as EditText
val value = text.text.toString()

Perform Segue programmatically and pass parameters to the destination view

Swift 4:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "ExampleSegueIdentifier" {
        if let destinationVC = segue.destination as? ExampleSegueVC {
            destinationVC.exampleString = "Example"

Swift 3:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "ExampleSegueIdentifier" {
            if let destinationVC = segue.destinationViewController as? ExampleSegueVC {
                destinationVC.exampleString = "Example"

when I try to open an HTML file through `http://localhost/xampp/htdocs/index.html` it says unable to connect to localhost

I just put an index.html file in /htdocs and type in - and up comes the html.

Add a folder "named Forum" and type in

Search in lists of lists by given index

the above all look good

but do you want to keep the result?

if so...

you can use the following

result = [element for element in data if element[1] == search]

then a simple


lets you know if anything was found (and now you can do stuff with the results)

of course this does not handle elements which are length less than one (which you should be checking unless you know they always are greater than length 1, and in that case should you be using a tuple? (tuples are immutable))

if you know all items are a set length you can also do:

any(second == search for _, second in data)

or for len(data[0]) == 4:

any(second == search for _, second, _, _ in data)

...and I would recommend using

for element in data:

instead of

for i in range(len(data)):

(for future uses, unless you want to save or use 'i', and just so you know the '0' is not required, you only need use the full syntax if you are starting at a non zero value)