Programs & Examples On #Chardet

chardet is a python module for encoding detection

Pipenv: Command Not Found

In some cases of old pip version:

sudo easy_install pip
sudo pip install pipenv

Pip error: Microsoft Visual C++ 14.0 is required

Try doing this:

py -m pip install pipwin
py -m pipwin install PyAudio

Install pip in docker

You might want to change the DNS settings of the Docker daemon. You can edit (or create) the configuration file at /etc/docker/daemon.json with the dns key, as

    "dns": ["your_dns_address", ""]

In the example above, the first element of the list is the address of your DNS server. The second item is the Google’s DNS which can be used when the first one is not available.

Before proceeding, save daemon.json and restart the docker service.

sudo service docker restart

Once fixed, retry to run the build command.

ImportError: No module named 'Queue'

It's because of the Python version. In Python 3 it's import Queue as queue; on the contrary in Python 2.x it's import queue. If you want it for both environments you may use something below as mentioned here

   import queue
except ImportError:
   import Queue as queue

ImportError: No module named sqlalchemy

I'm new comer, use python 3.8 and met the same problem. I installed with pip instead of pip3 because i thought the pip installer is the same for python2 and python3 so this is proper installation

pip3 install flask_sqlalchemy

Java 11 package javax.xml.bind does not exist

According to the release-notes, Java 11 removed the Java EE modules:

java.xml.bind (JAXB) - REMOVED
  • Java 8 - OK
  • Java 9 - DEPRECATED
  • Java 10 - DEPRECATED
  • Java 11 - REMOVED

See JEP 320 for more info.

You can fix the issue by using alternate versions of the Java EE technologies. Simply add Maven dependencies that contain the classes you need:


Jakarta EE 8 update (Mar 2020)

Instead of using old JAXB modules you can fix the issue by using Jakarta XML Binding from Jakarta EE 8:


Jakarta EE 9 update (Nov 2020)

Use latest release of Eclipse Implementation of JAXB 3.0.0:


Note: Jakarta EE 9 adopts new API package namespace jakarta.xml.bind.*, so update import statements:

javax.xml.bind -> jakarta.xml.bind

eslint: error Parsing error: The keyword 'const' is reserved

ESLint defaults to ES5 syntax-checking. You'll want to override to the latest well-supported version of JavaScript.

Try adding a .eslintrc file to your project. Inside it:

    "parserOptions": {
        "ecmaVersion": 2017

    "env": {
        "es6": true

Hopefully this helps.

EDIT: I also found this example .eslintrc which might help.

HashMap to return default value for non-found keys?

I found the LazyMap quite helpful.

When the get(Object) method is called with a key that does not exist in the map, the factory is used to create the object. The created object will be added to the map using the requested key.

This allows you to do something like this:

    Map<String, AtomicInteger> map = LazyMap.lazyMap(new HashMap<>(), ()->new AtomicInteger(0));

The call to get creates a default value for the given key. You specify how to create the default value with the factory argument to LazyMap.lazyMap(map, factory). In the example above, the map is initialized to a new AtomicInteger with value 0.

PHP - iterate on string characters

You can also just access $s1 like an array, if you only need to access it:

$s1 = "hello world";
echo $s1[0]; // -> h

Display all dataframe columns in a Jupyter Python Notebook

If you want to show all the rows set like bellow

pd.options.display.max_rows = None

If you want to show all columns set like bellow

pd.options.display.max_columns = None

How to specify a port to run a create-react-app based project?

You can specify a environment variable named PORT to specify the port on which the server will run.

$ export PORT=3005 #Linux
$ $env:PORT=3005 # Windows - Powershell

What is the difference between "screen" and "only screen" in media queries?

@media screen and (max-width:480px) { … } 

screen here is to set the screen size of the media query. E.g the maximum width of the display area is 480px. So it is specifying the screen as opposed to the other available media types.

@media only screen and (max-width: 480px;) { … } 

only screen here is used to prevent older browsers that do not support media queries with media features from applying the specified styles.

How to add/subtract time (hours, minutes, etc.) from a Pandas DataFrame.Index whos objects are of type datetime.time?

The Philippe solution but cleaner:

My subtraction data is: '2018-09-22T11:05:00.000Z'

import datetime
import pandas as pd

df_modified = pd.to_datetime(df_reference.index.values) - datetime.datetime(2018, 9, 22, 11, 5, 0)

Run a mySQL query as a cron job?

This was a very handy page as I have a requirement to DELETE records from a mySQL table where the expiry date is < Today.

I am on a shared host and CRON did not like the suggestion AndrewKDay. it also said (and I agree) that exposing the password in this way could be insecure.

I then tried turning Events ON in phpMyAdmin but again being on a shared host this was a no no. Sorry fancyPants.

So I turned to embedding the SQL script in a PHP file. I used the example [here][1]

[1]: stored it in a sub folder somewhere safe and added an empty index.php for good measure. I was then able to test that this PHP file (and my SQL script) was working from the browser URL line.

All good so far. On to CRON. Following the above example almost worked. I ended up calling PHP before the path for my *.php file. Otherwise CRON didn't know what to do with the file.

my cron is set to run once per day and looks like this, modified for security.

00 * * * * php

For the final testing with CRON I initially set it to run each minute and had email alerts turned on. This quickly confirmed that it was running as planned and I changed it back to once per day.

Hope this helps.

How to Generate unique file names in C#

If the readability of the file name isn't important, then the GUID, as suggested by many will do. However, I find that looking into a directory with 1000 GUID file names is very daunting to sort through. So I usually use a combination of a static string which gives the file name some context information, a timestamp, and GUID.

For example:

public string GenerateFileName(string context)
    return context + "_" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + "_" + Guid.NewGuid().ToString("N");

filename1 = GenerateFileName("MeasurementData");
filename2 = GenerateFileName("Image");

This way, when I sort by filename, it will automatically group the files by the context string and sort by timestamp.

Note that the filename limit in windows is 255 characters.

How to center an iframe horizontally?

My simplest solution to this.

iframe {

How do I use vim registers?

I think the secret guru register is the expression = register. It can be used for creative mappings.

:inoremap  \d The current date <c-r>=system("date")<cr>

You can use it in conjunction with your system as above or get responses from custom VimL functions etc.

or just ad hoc stuff like


Looping through a DataTable

Please try the following code below:

//Here I am using a reader object to fetch data from database, along with sqlcommand onject (cmd).
//Once the data is loaded to the Datatable object (datatable) you can loop through it using the datatable.rows.count prop.

using (reader = cmd.ExecuteReader())
// Load the Data table object
  if (dataTable.Rows.Count > 0)
    DataColumn col = dataTable.Columns["YourColumnName"];  
    foreach (DataRow row in dataTable.Rows)
       strJsonData = row[col].ToString();

Date constructor returns NaN in IE, but works in Firefox and Chrome

Try out using getDate feature of datepicker.

$.datepicker.formatDate('yy-mm-dd',new Date(pField.datepicker("getDate")));

JavaScript adding decimal numbers issue

function add(){
    var first=parseFloat($("#first").val());
    var second=parseFloat($("#second").val());


Django set default form values

As explained in Django docs, initial is not default.

  • The initial value of a field is intended to be displayed in an HTML . But if the user delete this value, and finally send back a blank value for this field, the initial value is lost. So you do not obtain what is expected by a default behaviour.

  • The default behaviour is : the value that validation process will take if data argument do not contain any value for the field.

To implement that, a straightforward way is to combine initial and clean_<field>():

class JournalForm(ModelForm):
    tank = forms.IntegerField(widget=forms.HiddenInput(), initial=123) 


    def clean_tank(self):
        if not self['tank'].html_name in
            return self.fields['tank'].initial
        return self.cleaned_data['tank']

Differences between contentType and dataType in jQuery ajax function

enter image description here

In English:

  • ContentType: When sending data to the server, use this content type. Default is application/x-www-form-urlencoded; charset=UTF-8, which is fine for most cases.
  • Accepts: The content type sent in the request header that tells the server what kind of response it will accept in return. Depends on DataType.
  • DataType: The type of data that you're expecting back from the server. If none is specified, jQuery will try to infer it based on the MIME type of the response. Can be text, xml, html, script, json, jsonp.

How do I print the percent sign(%) in c

Your problem is that you have to change:




Or you could use ASCII code and write:

printf("%c", 37);


Is it possible to focus on a <div> using JavaScript focus() function?

window.location.hash = '#tries';

This will scroll to the element in question, essentially "focus"ing it.

How to abort an interactive rebase if --abort doesn't work?

Try to follow the advice you see on the screen, and first reset your master's HEAD to the commit it expects.

git update-ref refs/heads/master b918ac16a33881ce00799bea63d9c23bf7022d67

Then, abort the rebase again.

Convert char array to string use C

Assuming array is a character array that does not end in \0, you will want to use strncpy:

char * strncpy(char * destination, const char * source, size_t num);

like so:

strncpy(string, array, 20);
string[20] = '\0'

Then string will be a null terminated C string, as desired.

How to use radio buttons in ReactJS?

import React, { Component } from "react";

class RadionButtons extends Component {
  constructor(props) {

    this.state = {
      // gender : "" , // use this one if you don't wanna any default value for gender
      gender: "male" // we are using this state to store the value of the radio button and also use to display the active radio button

    this.handleRadioChange = this.handleRadioChange.bind(this);  // we require access to the state of component so we have to bind our function 

  // this function is called whenever you change the radion button 
  handleRadioChange(event) {
      // set the new value of checked radion button to state using setState function which is async funtion

  render() {
    return (
        <div check>
            value="male" // this is te value which will be picked up after radio button change
            checked={this.state.gender === "male"} // when this is true it show the male radio button in checked 
            onChange={this.handleRadioChange} // whenever it changes from checked to uncheck or via-versa it goes to the handleRadioChange function
           style={{ marginLeft: "5px" }} // inline style in reactjs 
        <div check>
            checked={this.state.gender === "female"}
          <span style={{ marginLeft: "5px" }}>Female</span>
export default RadionButtons;

Android studio 3.0: Unable to resolve dependency for :app@dexOptions/compileClasspath': Could not resolve project :animators

This may also happen when you add a reference to the feature module that uses the incorrect plugin type. Simply change to or

adb shell su works but adb root does not

By design adb root command works in development builds only (i.e. eng and userdebug which have ro.debuggable=1 by default). So to enable the adb root command on your otherwise rooted device just add the ro.debuggable=1 line to one of the following files:


If you want adb shell to start as root by default - then add as well.

Alternatively you could use modified adbd binary (which does not check for ro.debuggable)


#if defined(ALLOW_ADBD_ROOT)
// The properties that affect `adb root` and `adb unroot` are and
// ro.debuggable. In this context the names don't make the expected behavior
// particularly obvious.
// ro.debuggable:
//   Allowed to become root, but not necessarily the default. Set to 1 on
//   eng and userdebug builds.
//   Drop privileges by default. Set to 1 on userdebug and user builds.

Laravel assets url

Besides put all your assets in the public folder, you can use the HTML::image() Method, and only needs an argument which is the path to the image, relative on the public folder, as well:

{{ HTML::image('imgs/picture.jpg') }}

Which generates the follow HTML code:

<img src="http://localhost:8000/imgs/picture.jpg">

The link to other elements of HTML::image() Method:

IN vs ANY operator in PostgreSQL

There are two obvious points, as well as the points in the other answer:

  • They are exactly equivalent when using sub queries:

    SELECT * FROM table
    WHERE column IN(subquery);
    SELECT * FROM table
    WHERE column = ANY(subquery);

On the other hand:

  • Only the IN operator allows a simple list:

    SELECT * FROM table
    WHERE column IN(… , … , …);

Presuming they are exactly the same has caught me out several times when forgetting that ANY doesn’t work with lists.

string encoding and decoding?

Aside from getting decode and encode backwards, I think part of the answer here is actually don't use the ascii encoding. It's probably not what you want.

To begin with, think of str like you would a plain text file. It's just a bunch of bytes with no encoding actually attached to it. How it's interpreted is up to whatever piece of code is reading it. If you don't know what this paragraph is talking about, go read Joel's The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets right now before you go any further.

Naturally, we're all aware of the mess that created. The answer is to, at least within memory, have a standard encoding for all strings. That's where unicode comes in. I'm having trouble tracking down exactly what encoding Python uses internally for sure, but it doesn't really matter just for this. The point is that you know it's a sequence of bytes that are interpreted a certain way. So you only need to think about the characters themselves, and not the bytes.

The problem is that in practice, you run into both. Some libraries give you a str, and some expect a str. Certainly that makes sense whenever you're streaming a series of bytes (such as to or from disk or over a web request). So you need to be able to translate back and forth.

Enter codecs: it's the translation library between these two data types. You use encode to generate a sequence of bytes (str) from a text string (unicode), and you use decode to get a text string (unicode) from a sequence of bytes (str).

For example:

>>> s = "I look like a string, but I'm actually a sequence of bytes. \xe2\x9d\xa4"
>>> codecs.decode(s, 'utf-8')
u"I look like a string, but I'm actually a sequence of bytes. \u2764"

What happened here? I gave Python a sequence of bytes, and then I told it, "Give me the unicode version of this, given that this sequence of bytes is in 'utf-8'." It did as I asked, and those bytes (a heart character) are now treated as a whole, represented by their Unicode codepoint.

Let's go the other way around:

>>> u = u"I'm a string! Really! \u2764"
>>> codecs.encode(u, 'utf-8')
"I'm a string! Really! \xe2\x9d\xa4"

I gave Python a Unicode string, and I asked it to translate the string into a sequence of bytes using the 'utf-8' encoding. So it did, and now the heart is just a bunch of bytes it can't print as ASCII; so it shows me the hexadecimal instead.

We can work with other encodings, too, of course:

>>> s = "I have a section \xa7"
>>> codecs.decode(s, 'latin1')
u'I have a section \xa7'
>>> codecs.decode(s, 'latin1')[-1] == u'\u00A7'

>>> u = u"I have a section \u00a7"
>>> u
u'I have a section \xa7'
>>> codecs.encode(u, 'latin1')
'I have a section \xa7'

('\xa7' is the section character, in both Unicode and Latin-1.)

So for your question, you first need to figure out what encoding your str is in.

  • Did it come from a file? From a web request? From your database? Then the source determines the encoding. Find out the encoding of the source and use that to translate it into a unicode.

    s = [get from external source]
    u = codecs.decode(s, 'utf-8') # Replace utf-8 with the actual input encoding
  • Or maybe you're trying to write it out somewhere. What encoding does the destination expect? Use that to translate it into a str. UTF-8 is a good choice for plain text documents; most things can read it.

    u = u'My string'
    s = codecs.encode(u, 'utf-8') # Replace utf-8 with the actual output encoding
    [Write s out somewhere]
  • Are you just translating back and forth in memory for interoperability or something? Then just pick an encoding and stick with it; 'utf-8' is probably the best choice for that:

    u = u'My string'
    s = codecs.encode(u, 'utf-8')
    newu = codecs.decode(s, 'utf-8')

In modern programming, you probably never want to use the 'ascii' encoding for any of this. It's an extremely small subset of all possible characters, and no system I know of uses it by default or anything.

Python 3 does its best to make this immensely clearer simply by changing the names. In Python 3, str was replaced with bytes, and unicode was replaced with str.

TortoiseSVN icons not showing up under Windows 7

It seems there is another reason why the icons wont be shown. Today I made an update of my TortoiseSVN Client from 1.6.x to 1.10.x. After that the Icons of my Working copies were not displayed any more. But it turns out that it has nothing to do with to many applications occupy the possible icons. The reason was that the Working copies format was to old. First you have to make a "SVN upgrade working copy" with your new installed client.

You can read more about the details here: SVN upgrade working copy

Have a nice day

XPath to select multiple tags

Why not a/b/(c|d|e)? I just tried with Saxon XML library (wrapped up nicely with some Clojure goodness), and it seems to work. abc.xml is the doc described by OP.

(require '[saxon :as xml])
(def abc-doc (xml/compile-xml (slurp "abc.xml")))
(xml/query "a/b/(c|d|e)" abc-doc)
=> (#<XdmNode <c>C1</c>>
    #<XdmNode <d>D1</d>>
    #<XdmNode <e>E1</e>>
    #<XdmNode <c>C2</c>>
    #<XdmNode <d>D2</d>>
    #<XdmNode <e>E1</e>>)

Execute specified function every X seconds

Use System.Windows.Forms.Timer.

private Timer timer1; 
public void InitTimer()
    timer1 = new Timer();
    timer1.Tick += new EventHandler(timer1_Tick);
    timer1.Interval = 2000; // in miliseconds

private void timer1_Tick(object sender, EventArgs e)

You can call InitTimer() in Form1_Load().

Partition Function COUNT() OVER possible using DISTINCT

There is a very simple solution using dense_rank()

dense_rank() over (partition by [Mth] order by [UserAccountKey]) 
+ dense_rank() over (partition by [Mth] order by [UserAccountKey] desc) 
- 1

This will give you exactly what you were asking for: The number of distinct UserAccountKeys within each month.

Jmeter - get current date and time

Use this format: ${__time(yyyy-MM-dd'T'hh:mm:ss.SS'Z')}

Which will give you: 2018-01-16T08:32:28.75Z

Display filename before matching line

Try this little trick to coax grep into thinking it is dealing with multiple files, so that it displays the filename:

grep 'pattern' file /dev/null

To also get the line number:

grep -n 'pattern' file /dev/null

iPhone get SSID without private library

Here's the short & sweet Swift version.

Remember to link and import the Framework:

import UIKit
import SystemConfiguration.CaptiveNetwork

Define the method:

func fetchSSIDInfo() -> CFDictionary? {
    if let
        ifs = CNCopySupportedInterfaces().takeUnretainedValue() as? [String],
        ifName = ifs.first,
        info = CNCopyCurrentNetworkInfo((ifName as CFStringRef))
        return info.takeUnretainedValue()
    return nil

Call the method when you need it:

if let
    ssidInfo = fetchSSIDInfo() as? [String:AnyObject],
    ssID = ssidInfo["SSID"] as? String
    println("SSID: \(ssID)")
} else {
    println("SSID not found")

As mentioned elsewhere, this only works on your iDevice. When not on WiFi, the method will return nil – hence the optional.

Where does the iPhone Simulator store its data?

On Lion the Users/[username]/Library is hidden.

To simply view in Finder, click the 'Go' menu at the top of the screen and hold down the 'alt' key to show 'Library'.

Click on 'Library' and you can see your previously hidden library folder.

Previously advised:


chflags nohidden /users/[username]/library

in a terminal to display the folder.

How to load Spring Application Context

Add this at the start of main

ApplicationContext context = new ClassPathXmlApplicationContext("path/to/applicationContext.xml");

JobLauncher launcher=(JobLauncher)context.getBean("launcher");
Job job=(Job)context.getBean("job");

//Get as many beans you want
//Now do the thing you were doing inside test method
StopWatch sw = new StopWatch();
sw.start();, jobParameters);
//initialize the log same way inside main">>> TIME ELAPSED:" + sw.prettyPrint());

How can I get enum possible values in a MySQL database?

try this

describe table columnname

gives you all the information about that column in that table;

Python, compute list difference

most simple way,

use set().difference(set())

list_a = [1,2,3]
list_b = [2,3]
print set(list_a).difference(set(list_b))

answer is set([1])

How to check whether a select box is empty using JQuery/Javascript

One correct way to get selected value would be

var selected_value = $('#fruit_name').val()

And then you should do

if(selected_value) { ... }

Skip first entry in for loop in python?

The best way to skip the first item(s) is:

from itertools import islice
for car in islice(cars, 1, None):
    # do something

islice in this case is invoked with a start-point of 1, and an end point of None, signifying the end of the iterator.

To be able to skip items from the end of an iterable, you need to know its length (always possible for a list, but not necessarily for everything you can iterate on). for example, islice(cars, 1, len(cars)-1) will skip the first and last items in the cars list.

Compiling with g++ using multiple cores

make will do this for you. Investigate the -j and -l switches in the man page. I don't think g++ is parallelizable.

Different ways of clearing lists

Doing alist = [] does not clear the list, just creates an empty list and binds it to the variable alist. The old list will still exist if it had other variable bindings.

To actually clear a list in-place, you can use any of these ways:

  1. alist.clear() # Python 3.3+, most obvious
  2. del alist[:]
  3. alist[:] = []
  4. alist *= 0 # fastest

See the Mutable Sequence Types documentation page for more details.

How to initialize std::vector from C-style array?

Well, Pavel was close, but there's even a more simple and elegant solution to initialize a sequential container from a c style array.

In your case:

w_ (array, std::end(array))
  • array will get us a pointer to the beginning of the array (didn't catch it's name),
  • std::end(array) will get us an iterator to the end of the array.

Why is it common to put CSRF prevention tokens in cookies?

My best guess as to the answer: Consider these 3 options for how to get the CSRF token down from the server to the browser.

  1. In the request body (not an HTTP header).
  2. In a custom HTTP header, not Set-Cookie.
  3. As a cookie, in a Set-Cookie header.

I think the 1st one, request body (while demonstrated by the Express tutorial I linked in the question), is not as portable to a wide variety of situations; not everyone is generating every HTTP response dynamically; where you end up needing to put the token in the generated response might vary widely (in a hidden form input; in a fragment of JS code or a variable accessible by other JS code; maybe even in a URL though that seems generally a bad place to put CSRF tokens). So while workable with some customization, #1 is a hard place to do a one-size-fits-all approach.

The second one, custom header, is attractive but doesn't actually work, because while JS can get the headers for an XHR it invoked, it can't get the headers for the page it loaded from.

That leaves the third one, a cookie carried by a Set-Cookie header, as an approach that is easy to use in all situations (anyone's server will be able to set per-request cookie headers, and it doesn't matter what kind of data is in the request body). So despite its downsides, it was the easiest method for frameworks to implement widely.

How do I set a path in Visual Studio?

You have a couple of options:

  • You can add the path to the DLLs to the Executable files settings under Tools > Options > Projects and Solutions > VC++ Directories (but only for building, for executing or debugging here)
  • You can add them in your global PATH environment variable
  • You can start Visual Studio using a batch file as I described here and manipulate the path in that one
  • You can copy the DLLs into the executable file's directory :-)

Duplicate headers received from server

For me the issue was about a comma not in the filename but as below: -

Response.ok(streamingOutput,MediaType.APPLICATION_OCTET_STREAM_TYPE).header("content-disposition", "attachment, filename=your_file_name").build();

I accidentally put a comma after attachment. Got it resolved by replacing comma with a semicolon.

git pull displays "fatal: Couldn't find remote ref refs/heads/xxxx" and hangs up

In my case, it happenned for the master branch. Later found that my access to the project was accidentally revoked by the project manager. To cross-check, I visited the review site and couldn't see any commits of the said branch and others for that project.

Swift: print() vs println() vs NSLog()

If you're using Swift 2, now you can only use print() to write something to the output.

Apple has combined both println() and print() functions into one.

Updated to iOS 9

By default, the function terminates the line it prints by adding a line break.

print("Hello Swift")


To print a value without a line break after it, pass an empty string as the terminator

print("Hello Swift", terminator: "")


You now can use separator to concatenate multiple items

print("Hello", "Swift", 2, separator:" ")


Or you could combine using in this way

print("Hello", "Swift", 2, separator:" ", terminator:".")

How to switch between python 2.7 to python 3 from command line?

There is an easier way than all of the above; You can use the PY_PYTHON environment variable. From inside the cmd.exe shell;

For the latest version of Python 2


For the latest version of Python 3


If you want it to be permanent, set it in the control panel. Or use setx instead of set in the cmd.exe shell.

How do I execute .js files locally in my browser?

If you're using Google Chrome you can use the Chrome Dev Editor:

How to install a certificate in Xcode (preparing for app store submission)

In Xcode 5 this has been moved to:

Xcode>Preferences>Accounts>View Details button>

how to create insert new nodes in JsonNode?

I've recently found even more interesting way to create any ValueNode or ContainerNode (Jackson v2.3).

ObjectNode node = JsonNodeFactory.instance.objectNode();

Classes cannot be accessed from outside package

Do you by any chance have two PUBLICclass classes in your project, where one is public (the one of which you posted the signature here), and another one which is package visible, and you import the wrong one in your code ?

String.equals versus ==

The .equals() will check if the two strings have the same value and return the boolean value where as the == operator checks to see if the two strings are the same object.

Make a link open a new window (not tab)

You can try this:-

   <a href="some.htm" target="_blank">Link Text</a>

and you can try this one also:-

  <a href="some.htm" onclick="if(!event.ctrlKey&&!window.opera){alert('Hold the Ctrl Key');return false;}else{return true;}" target="_blank">Link Text</a>

Create nice column output in python

Scolp is a new library that lets you pretty print streaming columnar data easily while auto-adjusting column width.

(Disclaimer: I am the author)

@angular/material/index.d.ts' is not a module

import { MatDialogModule } from '@angular/material/dialog';
import { MatTableModule } from '@angular/material/table';
import { MatFormFieldModule } from '@angular/material/form-field';
import { MatInputModule } from '@angular/material/input';
import { MatButtonModule } from '@angular/material/button';

Required attribute on multiple checkboxes with the same name?

To provide another approach similar to the answer by @IvanCollantes. It works by additionally filtering the required checkboxes by name. I also simplified the code a bit and checks for a default checked checkbox.

jQuery(function($) {_x000D_
  var requiredCheckboxes = $(':checkbox[required]');_x000D_
  requiredCheckboxes.on('change', function(e) {_x000D_
    var checkboxGroup = requiredCheckboxes.filter('[name="' + $(this).attr('name') + '"]');_x000D_
    var isChecked =':checked');_x000D_
    checkboxGroup.prop('required', !isChecked);_x000D_
<script src=""></script>_x000D_
<form target="_blank">_x000D_
    At least one checkbox from each group is required..._x000D_
    <legend>Checkboxes Group test</legend>_x000D_
      <input type="checkbox" name="test[]" value="1" checked="checked" required="required">test-1_x000D_
      <input type="checkbox" name="test[]" value="2" required="required">test-2_x000D_
      <input type="checkbox" name="test[]" value="3" required="required">test-3_x000D_
    <legend>Checkboxes Group test2</legend>_x000D_
      <input type="checkbox" name="test2[]" value="1" required="required">test2-1_x000D_
      <input type="checkbox" name="test2[]" value="2" required="required">test2-2_x000D_
      <input type="checkbox" name="test2[]" value="3" required="required">test2-3_x000D_
  <button type="submit" value="submit">Submit</button>_x000D_

Function that creates a timestamp in c#

If you want timestamps that correspond to actual real times BUT also want them to be unique (for a given application instance), you can use the following code:

public class HiResDateTime
   private static long lastTimeStamp = DateTime.UtcNow.Ticks;
   public static long UtcNowTicks
           long orig, newval;
               orig = lastTimeStamp;
               long now = DateTime.UtcNow.Ticks;
               newval = Math.Max(now, orig + 1);
           } while (Interlocked.CompareExchange
                        (ref lastTimeStamp, newval, orig) != orig);

           return newval;

When to use window.opener / window.parent /

  • window.opener refers to the window that called ... ) to open the window from which it's called
  • window.parent refers to the parent of a window in a <frame> or <iframe>
  • refers to the top-most window from a window nested in one or more layers of <iframe> sub-windows

Those will be null (or maybe undefined) when they're not relevant to the referring window's situation. ("Referring window" means the window in whose context the JavaScript code is run.)

How do I rename both a Git local and remote branch name?

  1. Rename your local branch. If you are on the branch you want to rename:

    git branch -m new-name

If you are on a different branch:

git branch -m old-name new-name
  1. Delete the old-name remote branch and push the new-name local branch.

    git push origin :old-name new-name

  2. Reset the upstream branch for the new-name local branch. Switch to the branch and then:

    git push origin -u new-name

All set!

How to get last N records with activerecord?

This is the Rails 3 way

SomeModel.last(5) # last 5 records in ascending order

SomeModel.last(5).reverse # last 5 records in descending order

Splitting a dataframe string column into multiple different columns

A very direct way is to just use read.table on your character vector:

> read.table(text = text, sep = ".", colClasses = "character")
   V1 V2  V3  V4
1   F US CLE V13
2   F US CA6 U13
3   F US CA6 U13
4   F US CA6 U13
5   F US CA6 U13
6   F US CA6 U13
7   F US CA6 U13
8   F US CA6 U13
9   F US  DL U13
10  F US  DL U13
11  F US  DL U13
12  F US  DL Z13
13  F US  DL Z13

colClasses needs to be specified, otherwise F gets converted to FALSE (which is something I need to fix in "splitstackshape", otherwise I would have recommended that :) )

Update (> a year later)...

Alternatively, you can use my cSplit function, like this:

cSplit(, "text", ".")
#     text_1 text_2 text_3 text_4
#  1:      F     US    CLE    V13
#  2:      F     US    CA6    U13
#  3:      F     US    CA6    U13
#  4:      F     US    CA6    U13
#  5:      F     US    CA6    U13
#  6:      F     US    CA6    U13
#  7:      F     US    CA6    U13
#  8:      F     US    CA6    U13
#  9:      F     US     DL    U13
# 10:      F     US     DL    U13
# 11:      F     US     DL    U13
# 12:      F     US     DL    Z13
# 13:      F     US     DL    Z13

Or, separate from "tidyr", like this:

library(tidyr) %>% separate(text, into = paste("V", 1:4, sep = "_"))
#    V_1 V_2 V_3 V_4
# 1    F  US CLE V13
# 2    F  US CA6 U13
# 3    F  US CA6 U13
# 4    F  US CA6 U13
# 5    F  US CA6 U13
# 6    F  US CA6 U13
# 7    F  US CA6 U13
# 8    F  US CA6 U13
# 9    F  US  DL U13
# 10   F  US  DL U13
# 11   F  US  DL U13
# 12   F  US  DL Z13
# 13   F  US  DL Z13

Regular expression to validate US phone numbers?

The easiest way to match both




is to use alternation ((...|...)): specify them as two mostly-separate options:


By the way, when Americans put the area code in parentheses, we actually put a space after that; for example, I'd write (123) 123-1234, not (123)123-1234. So you might want to write:

^(\([0-9]{3}\) |[0-9]{3}-)[0-9]{3}-[0-9]{4}$

(Though it's probably best to explicitly demonstrate the format that you expect phone numbers to be in.)

How to clean old dependencies from maven repositories?

  1. Download all actual dependencies of your projects

    find your-projects-dir -name pom.xml -exec mvn -f '{}' dependency:resolve
  2. Move your local maven repository to temporary location

    mv ~/.m2 ~/saved-m2
  3. Rename all files maven-metadata-central.xml* from saved repository into maven-metadata.xml*

    find . -type f -name "maven-metadata-central.xml*" -exec rename -v -- 's/-central//' '{}' \;
  4. To setup the modified copy of the local repository as a mirror, create the directory ~/.m2 and the file ~/.m2/settings.xml with the following content (replacing user with your username):

       <name>My Central</name>
  5. Resolve your projects dependencies again:

    find your-projects-dir -name pom.xml -exec mvn -f '{}' dependency:resolve
  6. Now you have local maven repository with minimal of necessary artifacts. Remove local mirror from config file and from file system.

Spring @ContextConfiguration how to put the right location for the xml

We Use:


the project is a eclipse dynamic web project, then the path is:

{project name}/WebContent/WEB-INF/spitterMVC-servlet.xml

JavaScript: Create and save file

For Chrome and Firefox, I have been using a purely JavaScript method.

(My application cannot make use of a package such as Blob.js because it is served from a special engine: a DSP with a WWWeb server crammed in and little room for anything at all.)

function FileSave(sourceText, fileIdentity) {
    var workElement = document.createElement("a");
    if ('download' in workElement) {
        workElement.href = "data:" + 'text/plain' + "charset=utf-8," + escape(sourceText);
        workElement.setAttribute("download", fileIdentity);
        var eventMouse = document.createEvent("MouseEvents");
        eventMouse.initMouseEvent("click", true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
    } else throw 'File saving not supported for this browser';

Notes, caveats, and weasel-words:

  • I have had success with this code in both Chrome and Firefox clients running in Linux (Maipo) and Windows (7 and 10) environments.
  • However, if sourceText is larger than a MB, Chrome sometimes (only sometimes) gets stuck in its own download without any failure indication; Firefox, so far, has not exhibited this behavior. The cause might be some blob limitation in Chrome. Frankly, I just don't know; if anybody has any ideas how to correct (or at least detect), please post. If the download anomaly occurs, when the Chrome browser is closed, it generates a diagnostic such as Chrome browser diagnostic
  • This code is not compatible with Edge or Internet Explorer; I have not tried Opera or Safari.

What does AND 0xFF do?

The danger of the second expression comes if the type of byte1 is char. In that case, some implementations can have it signed char, which will result in sign extension when evaluating.

signed char byte1 = 0x80;
signed char byte2 = 0x10;

unsigned short value1 = ((byte2 << 8) | (byte1 & 0xFF));
unsigned short value2 = ((byte2 << 8) | byte1);

printf("value1=%hu %hx\n", value1, value1);
printf("value2=%hu %hx\n", value2, value2);

will print

value1=4224 1080     right
value2=65408 ff80    wrong!!

I tried it on gcc v3.4.6 on Solaris SPARC 64 bit and the result is the same with byte1 and byte2 declared as char.


The masking is to avoid implicit sign extension.

EDIT: I checked, it's the same behaviour in C++.

EDIT2: As requested explanation of sign extension. Sign extension is a consequence of the way C evaluates expressions. There is a rule in C called promotion rule. C will implicitly cast all small types to int before doing the evaluation. Let's see what happens to our expression:

unsigned short value2 = ((byte2 << 8) | byte1);

byte1 is a variable containing bit pattern 0xFF. If char is unsigned that value is interpreted as 255, if it is signed it is -128. When doing the calculation, C will extend the value to an int size (16 or 32 bits generally). This means that if the variable is unsigned and we will keep the value 255, the bit-pattern of that value as int will be 0x000000FF. If it is signed we want the value -128 which bit pattern is 0xFFFFFFFF. The sign was extended to the size of the tempory used to do the calculation. And thus oring the temporary will yield the wrong result.

On x86 assembly it is done with the movsx instruction (movzx for the zero extend). Other CPU's had other instructions for that (6809 had SEX).

Why use static_cast<int>(x) instead of (int)x?

  1. Allows casts to be found easily in your code using grep or similar tools.
  2. Makes it explicit what kind of cast you are doing, and engaging the compiler's help in enforcing it. If you only want to cast away const-ness, then you can use const_cast, which will not allow you to do other types of conversions.
  3. Casts are inherently ugly -- you as a programmer are overruling how the compiler would ordinarily treat your code. You are saying to the compiler, "I know better than you." That being the case, it makes sense that performing a cast should be a moderately painful thing to do, and that they should stick out in your code, since they are a likely source of problems.

See Effective C++ Introduction

Reference an Element in a List of Tuples

Rather than:

first_element = myList[i[0]]

You probably want:

first_element = myList[i][0]

How do I negate a condition in PowerShell?

You almost had it with Not. It should be:

if (-Not (Test-Path C:\Code)) {
    write "it doesn't exist!"

You can also use !: if (!(Test-Path C:\Code)){}

Just for fun, you could also use bitwise exclusive or, though it's not the most readable/understandable method.

if ((test-path C:\code) -bxor 1) {write "it doesn't exist!"}

automating telnet session using bash scripts

Following is working for me... put all of your IPs you want to telnet in IP_sheet.txt

while true
read a
    sleep 3
    echo df -kh
    sleep 3
    echo exit
} | telnet $a

Saving image from PHP URL

Vartec's answer with cURL didn't work for me. It did, with a slight improvement due to my specific problem.


When there is a redirect on the server (like when you are trying to save the facebook profile image) you will need following option set:

curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

The full solution becomes:

$ch = curl_init('');
$fp = fopen('/my/folder/flower.gif', 'wb');
curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

How to check if multiple array keys exists

If you only have 2 keys to check (like in the original question), it's probably easy enough to just call array_key_exists() twice to check if the keys exists.

if (array_key_exists("story", $arr) && array_key_exists("message", $arr)) {
    // Both keys exist.

However this obviously doesn't scale up well to many keys. In that situation a custom function would help.

function array_keys_exists(array $keys, array $arr) {
   return !array_diff_key(array_flip($keys), $arr);

Unfamiliar symbol in algorithm: what does ? mean?

yes, these are the well-known quantifiers used in math. Another example is ? which reads as "exists".

JSON Structure for List of Objects

As others mentioned, Justin's answer was close, but not quite right. I tested this using Visual Studio's "Paste JSON as C# Classes"

    "foos" : [

Confirm deletion using Bootstrap 3 modal box

enter image description here Following solution is better than bootbox.js, because

  • It can do everything bootbox.js can do;
  • The use syntax is simpler
  • It allows you to elegantly control the color of your message using "error", "warning" or "info"
  • Bootbox is 986 lines long, mine only 110 lines long


const dialogTemplate = '\_x000D_
    <div class ="modal" id="digimango_messageBox" role="dialog">\_x000D_
        <div class ="modal-dialog">\_x000D_
            <div class ="modal-content">\_x000D_
                <div class ="modal-body">\_x000D_
                    <p class ="text-success" id="digimango_messageBoxMessage">Some text in the modal.</p>\_x000D_
                    <p><textarea id="digimango_messageBoxTextArea" cols="70" rows="5"></textarea></p>\_x000D_
                <div class ="modal-footer">\_x000D_
                    <button type="button" class ="btn btn-primary" id="digimango_messageBoxOkButton">OK</button>\_x000D_
                    <button type="button" class ="btn btn-default" data-dismiss="modal" id="digimango_messageBoxCancelButton">Cancel</button>\_x000D_
// See the comment inside function digimango_onOkClick(event) {_x000D_
var digimango_numOfDialogsOpened = 0;_x000D_
function messageBox(msg, significance, options, actionConfirmedCallback) {_x000D_
    if ($('#digimango_MessageBoxContainer').length == 0) {_x000D_
        var iDiv = document.createElement('div');_x000D_ = 'digimango_MessageBoxContainer';_x000D_
    var okButtonName, cancelButtonName, showTextBox, textBoxDefaultText;_x000D_
    if (options == null) {_x000D_
        okButtonName = 'OK';_x000D_
        cancelButtonName = null;_x000D_
        showTextBox = null;_x000D_
        textBoxDefaultText = null;_x000D_
    } else {_x000D_
        okButtonName = options.okButtonName;_x000D_
        cancelButtonName = options.cancelButtonName;_x000D_
        showTextBox = options.showTextBox;_x000D_
        textBoxDefaultText = options.textBoxDefaultText;_x000D_
    if (showTextBox == true) {_x000D_
        if (textBoxDefaultText == null)_x000D_
    if (okButtonName != null)_x000D_
    if (cancelButtonName == null)_x000D_
    else {_x000D_
    $('#digimango_messageBoxOkButton').on('click', { callback: actionConfirmedCallback }, digimango_onOkClick);_x000D_
    $('#digimango_messageBoxCancelButton').on('click', digimango_onCancelClick);_x000D_
    var content = $("#digimango_messageBoxMessage");_x000D_
    if (significance == 'error')_x000D_
        content.attr('class', 'text-danger');_x000D_
    else if (significance == 'warning')_x000D_
        content.attr('class', 'text-warning');_x000D_
        content.attr('class', 'text-success');_x000D_
    if (digimango_numOfDialogsOpened == 0)_x000D_
function digimango_onOkClick(event) {_x000D_
    // JavaScript's nature is unblocking. So the function call in the following line will not block,_x000D_
    // thus the last line of this function, which is to hide the dialog, is executed before user_x000D_
    // clicks the "OK" button on the second dialog shown in the callback. Therefore we need to count_x000D_
    // how many dialogs is currently showing. If we know there is still a dialog being shown, we do_x000D_
    // not execute the last line in this function._x000D_
    if (typeof ( != 'undefined')_x000D_$('#digimango_messageBoxTextArea').val());_x000D_
    if (digimango_numOfDialogsOpened == 0)_x000D_
function digimango_onCancelClick() {_x000D_
    if (digimango_numOfDialogsOpened == 0)_x000D_

To use digimango.messagebox.js:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">_x000D_
<html xmlns="">_x000D_
    <title>A useful generic message box</title>_x000D_
    <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />_x000D_
    <link rel="stylesheet" type="text/css" href="~/Content/bootstrap.min.css" media="screen" />_x000D_
    <script src="~/Scripts/jquery-1.10.2.min.js" type="text/javascript"></script>_x000D_
    <script src="~/Scripts/bootstrap.js" type="text/javascript"></script>_x000D_
    <script src="~/Scripts/bootbox.js" type="text/javascript"></script>_x000D_
    <script src="~/Scripts/digimango.messagebox.js" type="text/javascript"></script>_x000D_
    <script type="text/javascript">_x000D_
        function testAlert() {_x000D_
            messageBox('Something went wrong!', 'error');_x000D_
        function testAlertWithCallback() {_x000D_
            messageBox('Something went wrong!', 'error', null, function () {_x000D_
                messageBox('OK clicked.');_x000D_
        function testConfirm() {_x000D_
            messageBox('Do you want to proceed?', 'warning', { okButtonName: 'Yes', cancelButtonName: 'No' }, function () {_x000D_
                messageBox('Are you sure you want to proceed?', 'warning', { okButtonName: 'Yes', cancelButtonName: 'No' });_x000D_
        function testPrompt() {_x000D_
            messageBox('How do you feel now?', 'normal', { showTextBox: true }, function (userInput) {_x000D_
                messageBox('User entered "' + userInput + '".');_x000D_
        function testPromptWithDefault() {_x000D_
            messageBox('How do you feel now?', 'normal', { showTextBox: true, textBoxDefaultText: 'I am good!' }, function (userInput) {_x000D_
                messageBox('User entered "' + userInput + '".');_x000D_
    <a href="#" onclick="testAlert();">Test alert</a> <br/>_x000D_
    <a href="#" onclick="testAlertWithCallback();">Test alert with callback</a> <br />_x000D_
    <a href="#" onclick="testConfirm();">Test confirm</a> <br/>_x000D_
    <a href="#" onclick="testPrompt();">Test prompt</a><br />_x000D_
    <a href="#" onclick="testPromptWithDefault();">Test prompt with default text</a> <br />_x000D_

How to convert NUM to INT in R?

Use as.integer:

x <- runif(5, 0, 100)
[1] 26.55087 37.21239 57.28534 90.82078 20.16819

[1] 26 37 57 90 20

Test for class:

xx <- as.integer(x)
 int [1:5] 26 37 57 90 20

Switch/toggle div (jQuery)

I think you want this:




This is made possible by jQuery.

How can I limit possible inputs in a HTML5 "number" element?

I know there's an answer already, but if you want your input to behave exactly like the maxlength attribute or as close as you can, use the following code:

(function($) {
 methods = {
     * addMax will take the applied element and add a javascript behavior
     * that will set the max length
    addMax: function() {
        // set variables
            maxlAttr = $(this).attr("maxlength"),
            maxAttR = $(this).attr("max"),
            x = 0,
            max = "";

        // If the element has maxlength apply the code.
        if (typeof maxlAttr !== typeof undefined && maxlAttr !== false) {

            // create a max equivelant
            if (typeof maxlAttr !== typeof undefined && maxlAttr !== false){
                while (x < maxlAttr) {
                    max += "9";
              maxAttR = max;

            // Permissible Keys that can be used while the input has reached maxlength
            var keys = [
                8, // backspace
                9, // tab
                13, // enter
                46, // delete
                37, 39, 38, 40 // arrow keys<^>v

            // Apply changes to element
                .attr("max", maxAttR) //add existing max or new max
                .keydown(function(event) {
                    // restrict key press on length reached unless key being used is in keys array or there is highlighted text
                    if ($(this).val().length == maxlAttr && $.inArray(event.which, keys) == -1 && methods.isTextSelected() == false) return false;
     * isTextSelected returns true if there is a selection on the page. 
     * This is so that if the user selects text and then presses a number
     * it will behave as normal by replacing the selection with the value
     * of the key pressed.
    isTextSelected: function() {
       // set text variable
        text = "";
        if (window.getSelection) {
            text = window.getSelection().toString();
        } else if (document.selection && document.selection.type != "Control") {
            text = document.selection.createRange().text;
        return (text.length > 0);

$.maxlengthNumber = function(){
     // Get all number inputs that have maxlength$("input[type=number]"));


// Apply it:

How to define dimens.xml for every different screen size in android?

I've uploaded a simple java program which takes your project location and the dimension file you want as input. Based on that, it would output the corresponding dimension file in the console. Here's the link to it:

Here's the full code for the reference:

public class Main {

     * You can change your factors here. The current factors are in accordance with the official documentation.
    private static final double LDPI_FACTOR = 0.375;
    private static final double MDPI_FACTOR = 0.5;
    private static final double HDPI_FACTOR = 0.75;
    private static final double XHDPI_FACTOR = 1.0;
    private static final double XXHDPI_FACTOR = 1.5;
    private static final double XXXHDPI_FACTOR = 2.0;

    private static double factor;

    public static void main(String[] args) throws IOException {

        Scanner in = new Scanner(;
        System.out.println("Enter the location of the project/module");
        String projectPath = in.nextLine();

        System.out.println("Which of the following dimension file do you want?\n1. ldpi \n2. mdpi \n3. hdpi \n4. xhdpi \n5. xxhdpi \n6. xxxhdpi");

        int dimenType = in.nextInt();

        switch (dimenType) {
            case 1: factor = LDPI_FACTOR;
            case 2: factor = MDPI_FACTOR;
            case 3: factor = HDPI_FACTOR;
            case 4: factor = XHDPI_FACTOR;
            case 5: factor = XXHDPI_FACTOR;
            case 6: factor = XXXHDPI_FACTOR;
                factor = 1.0;

        //full path = "/home/akeshwar/android-sat-bothIncluded-notintegrated/code/tpr-5-5-9/princetonReview/src/main/res/values/dimens.xml"
        //location of the project or module = "/home/akeshwar/android-sat-bothIncluded-notintegrated/code/tpr-5-5-9/princetonReview/"

         * In case there is some I/O exception with the file, you can directly copy-paste the full path to the file here:
        String fullPath = projectPath + "/src/main/res/values/dimens.xml";

        FileInputStream fstream = new FileInputStream(fullPath);
        BufferedReader br = new BufferedReader(new InputStreamReader(fstream));

        String strLine;

        while ((strLine = br.readLine()) != null)   {


    private static void modifyLine(String line) {

         * Well, this is how I'm detecting if the line has some dimension value or not.
        if(line.contains("p</")) {
            int endIndex = line.indexOf("p</");

            //since indexOf returns the first instance of the occurring string. And, the actual dimension would follow after the first ">" in the screen
            int begIndex = line.indexOf(">");

            String prefix = line.substring(0, begIndex+1);
            String root = line.substring(begIndex+1, endIndex-1);
            String suffix = line.substring(endIndex-1,line.length());

             * Now, we have the root. We can use it to create different dimensions. Root is simply the dimension number.

            double dimens = Double.parseDouble(root);
            dimens = dimens*factor*1000;
            dimens = (double)((int)dimens);
            dimens = dimens/1000;
            root = dimens + "";

            System.out.println(prefix + " " +  root + " " + suffix );



How to hide axes and gridlines in Matplotlib (python)

Turn the axes off with:


And gridlines with:


Assembly code vs Machine code vs Object code?

Machine code is binary (1's and 0's) code that can be executed directly by the CPU. If you open a machine code file in a text editor you would see garbage, including unprintable characters (no, not those unprintable characters ;) ).

Object code is a portion of machine code not yet linked into a complete program. It's the machine code for one particular library or module that will make up the completed product. It may also contain placeholders or offsets not found in the machine code of a completed program. The linker will use these placeholders and offsets to connect everything together.

Assembly code is plain-text and (somewhat) human read-able source code that mostly has a direct 1:1 analog with machine instructions. This is accomplished using mnemonics for the actual instructions, registers, or other resources. Examples include JMP and MULT for the CPU's jump and multiplication instructions. Unlike machine code, the CPU does not understand assembly code. You convert assembly code to machine code with the use of an assembler or a compiler, though we usually think of compilers in association with high-level programming language that are abstracted further from the CPU instructions.

Building a complete program involves writing source code for the program in either assembly or a higher level language like C++. The source code is assembled (for assembly code) or compiled (for higher level languages) to object code, and individual modules are linked together to become the machine code for the final program. In the case of very simple programs the linking step may not be needed. In other cases, such as with an IDE (integrated development environment) the linker and compiler may be invoked together. In other cases, a complicated make script or solution file may be used to tell the environment how to build the final application.

There are also interpreted languages that behave differently. Interpreted languages rely on the machine code of a special interpreter program. At the basic level, an interpreter parses the source code and immediately converts the commands to new machine code and executes them. Modern interpreters are now much more complicated: evaluating whole sections of source code at a time, caching and optimizing where possible, and handling complex memory management tasks.

One final type of program involves the use of a runtime-environment or virtual machine. In this situation, a program is first pre-compiled to a lower-level intermediate language or byte code. The byte code is then loaded by the virtual machine, which just-in-time compiles it to native code. The advantage here is the virtual machine can take advantage of optimizations available at the time the program runs and for that specific environment. A compiler belongs to the developer, and therefore must produce relatively generic (less-optimized) machine code that could run in many places. The runtime environment or virtual machine, however, is located on the end user's computer and therefore can take advantage of all the features provided by that system.

How to update Git clone

If you want to fetch + merge, run

git pull

if you want simply to fetch :

git fetch

How to run Rake tasks from within Rake tasks?

If you want each task to run regardless of any failures, you can do something like:

task :build_all do
  [:debug, :release].each do |t| 
    ts = 0
      ts = 1
      Rake::Task["build"].reenable # If you need to reenable
    return ts # Return exit code 1 if any failed, 0 if all success

Delete column from pandas DataFrame

It's good practice to always use the [] notation. One reason is that attribute notation (df.column_name) does not work for numbered indices:

In [1]: df = DataFrame([[1, 2, 3], [4, 5, 6]])

In [2]: df[1]
0    2
1    5
Name: 1

In [3]: df.1
  File "<ipython-input-3-e4803c0d1066>", line 1
SyntaxError: invalid syntax

Simple bubble sort c#

int[] arr = { 800, 11, 50, 771, 649, 770, 240, 9 };
for (int i = 0; i < arr.Length; i++)
    for (int j = i; j < arr.Length ; j++)
        if (arr[j] < arr[i])
            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;

How to handle Pop-up in Selenium WebDriver using Java

String parentWindowHandler = driver.getWindowHandle(); // Store your parent window
String subWindowHandler = null;

Set<String> handles = driver.getWindowHandles(); // get all window handles
Iterator<String> iterator = handles.iterator();

subWindowHandler =;

driver.switchTo().window(subWindowHandler); // switch to popup window

// Now you are in the popup window, perform necessary actions here

driver.switchTo().window(parentWindowHandler);  // switch back to parent window

The tilde operator in Python

I was solving this leetcode problem and I came across this beautiful solution by a user named Zitao Wang.

The problem goes like this for each element in the given array find the product of all the remaining numbers without making use of divison and in O(n) time

The standard solution is:

Pass 1: For all elements compute product of all the elements to the left of it
Pass 2: For all elements compute product of all the elements to the right of it
        and then multiplying them for the final answer 

His solution uses only one for loop by making use of. He computes the left product and right product on the fly using ~

def productExceptSelf(self, nums):
    res = [1]*len(nums)
    lprod = 1
    rprod = 1
    for i in range(len(nums)):
        res[i] *= lprod
        lprod *= nums[i]
        res[~i] *= rprod
        rprod *= nums[~i]
    return res

How to set default values for Angular 2 component properties?

Here is the best solution for this. (ANGULAR All Version)

Addressing solution: To set a default value for @Input variable. If no value passed to that input variable then It will take the default value.

I have provided solution for this kind of similar question. You can find the full solution from here

export class CarComponent implements OnInit {
  private _defaultCar: car = {
    // default isCar is true
    isCar: true,
    // default wheels  will be 4
    wheels: 4

  @Input() newCar: car = {};

  constructor() {}

  ngOnInit(): void {

   // this will concate both the objects and the object declared later (ie.. ...this.newCar )
   // will overwrite the default value. ONLY AND ONLY IF DEFAULT VALUE IS PRESENT

    this.newCar = { ...this._defaultCar, ...this.newCar };
   //  console.log(this.newCar);

Does a foreign key automatically create an index?

Say you have a big table called orders, and a small table called customers. There is a foreign key from an order to a customer. Now if you delete a customer, Sql Server must check that there are no orphan orders; if there are, it raises an error.

To check if there are any orders, Sql Server has to search the big orders table. Now if there is an index, the search will be fast; if there is not, the search will be slow.

So in this case, the slow delete could be explained by the absence of an index. Especially if Sql Server would have to search 15 big tables without an index.

P.S. If the foreign key has ON DELETE CASCADE, Sql Server still has to search the order table, but then to remove any orders that reference the deleted customer.

No String-argument constructor/factory method to deserialize from String value ('')


My code work well just as the answer above. The reason is that the json from jackson is different with the json sent from controller.

String test1= mapper.writeValueAsString(result1);

And the json is like(which can be deserialized normally):


but the json send from the another service just like:


You can notice the difference when dealing with the param without initiation. Be careful

Use space as a delimiter with cut command

cut -d ' ' -f 2

Where 2 is the field number of the space-delimited field you want.

How to scale Docker containers in production

Have a look at - it can manage multiple Docker hosts and much more.

String replacement in Objective-C

If you want multiple string replacement:

NSString *s = @"foo/";
NSCharacterSet *doNotWant = [NSCharacterSet characterSetWithCharactersInString:@"/:."];
s = [[s componentsSeparatedByCharactersInSet: doNotWant] componentsJoinedByString: @""];
NSLog(@"%@", s); // => foobarbazfoo

PHP Get URL with Parameter

for complette URL with protocol, servername and parameters:

 $base_url = ( isset($_SERVER['HTTPS']) && $_SERVER['HTTPS']=='on' ? 'https' : 'http' ) . '://' .  $_SERVER['HTTP_HOST'];
 $url = $base_url . $_SERVER["REQUEST_URI"];

React hooks useState Array

Try to keep your state minimal. There is no need to store

   const initialValue = [
    { id: 0,value: " --- Select a State ---" }];

as state. Separate the permanent from the changing

const ALL_STATE_VALS = [
    { id: 0,value: " --- Select a State ---" }
    { id: 1, value: "Alabama" },
    { id: 2, value: "Georgia" },
    { id: 3, value: "Tennessee" }

Then you can store just the id as your state:

const StateSelector = () =>{
  const [selectedStateOption, setselectedStateOption] = useState(0);

  return (
      <label>Select a State:</label>
        {, index) => (
          <option key={} selected={index===selectedStateOption}>{option.value}</option>
}"#element") not working when code above the html element

just add your <script src="./custom.js"></script> before </bod> tag. that is supply time to detect your #chart element in html body

What is the difference between SAX and DOM?

I will provide general Q&A-oriented answer for this question:

Answer to Questions

Why do we need XML parser?

We need XML parser because we do not want to do everything in our application from scratch, and we need some "helper" programs or libraries to do something very low-level but very necessary to us. These low-level but necessary things include checking the well-formedness, validating the document against its DTD or schema (just for validating parsers), resolving character reference, understanding CDATA sections, and so on. XML parsers are just such "helper" programs and they will do all these jobs. With XML parser, we are shielded from a lot of these complexities and we could concentrate ourselves on just programming at high-level through the API's implemented by the parsers, and thus gain programming efficiency.

Which one is better, SAX or DOM ?

Both SAX and DOM parser have their advantages and disadvantages. Which one is better should depend on the characteristics of your application (please refer to some questions below).

Which parser can get better speed, DOM or SAX parsers?

SAX parser can get better speed.

What's the difference between tree-based API and event-based API?

A tree-based API is centered around a tree structure and therefore provides interfaces on components of a tree (which is a DOM document) such as Document interface,Node interface, NodeList interface, Element interface, Attr interface and so on. By contrast, however, an event-based API provides interfaces on handlers. There are four handler interfaces, ContentHandler interface, DTDHandler interface, EntityResolver interface and ErrorHandler interface.

What is the difference between a DOM Parser and a SAX Parser?

DOM parsers and SAX parsers work in different ways:

  • A DOM parser creates a tree structure in memory from the input document and then waits for requests from client. But a SAX parser does not create any internal structure. Instead, it takes the occurrences of components of a input document as events, and tells the client what it reads as it reads through the input document. A

  • DOM parser always serves the client application with the entire document no matter how much is actually needed by the client. But a SAX parser serves the client application always only with pieces of the document at any given time.

  • With DOM parser, method calls in client application have to be explicit and forms a kind of chain. But with SAX, some certain methods (usually overriden by the cient) will be invoked automatically (implicitly) in a way which is called "callback" when some certain events occur. These methods do not have to be called explicitly by the client, though we could call them explicitly.

How do we decide on which parser is good?

Ideally a good parser should be fast (time efficient),space efficient, rich in functionality and easy to use. But in reality, none of the main parsers have all these features at the same time. For example, a DOM Parser is rich in functionality (because it creates a DOM tree in memory and allows you to access any part of the document repeatedly and allows you to modify the DOM tree), but it is space inefficient when the document is huge, and it takes a little bit long to learn how to work with it. A SAX Parser, however, is much more space efficient in case of big input document (because it creates no internal structure). What's more, it runs faster and is easier to learn than DOM Parser because its API is really simple. But from the functionality point of view, it provides less functions which mean that the users themselves have to take care of more, such as creating their own data structures. By the way, what is a good parser? I think the answer really depends on the characteristics of your application.

What are some real world applications where using SAX parser is advantageous than using DOM parser and vice versa? What are the usual application for a DOM parser and for a SAX parser?

In the following cases, using SAX parser is advantageous than using DOM parser.

  • The input document is too big for available memory (actually in this case SAX is your only choice)
  • You can process the document in small contiguous chunks of input. You do not need the entire document before you can do useful work
  • You just want to use the parser to extract the information of interest, and all your computation will be completely based on the data structures created by yourself. Actually in most of our applications, we create data structures of our own which are usually not as complicated as the DOM tree. From this sense, I think, the chance of using a DOM parser is less than that of using a SAX parser.

In the following cases, using DOM parser is advantageous than using SAX parser.

  • Your application needs to access widely separately parts of the document at the same time.
  • Your application may probably use a internal data structure which is almost as complicated as the document itself.
  • Your application has to modify the document repeatedly.
  • Your application has to store the document for a significant amount of time through many method calls.

Example (Use a DOM parser or a SAX parser?):

Assume that an instructor has an XML document containing all the personal information of the students as well as the points his students made in his class, and he is now assigning final grades for the students using an application. What he wants to produce, is a list with the SSN and the grades. Also we assume that in his application, the instructor use no data structure such as arrays to store the student personal information and the points. If the instructor decides to give A's to those who earned the class average or above, and give B's to the others, then he'd better to use a DOM parser in his application. The reason is that he has no way to know how much is the class average before the entire document gets processed. What he probably need to do in his application, is first to look through all the students' points and compute the average, and then look through the document again and assign the final grade to each student by comparing the points he earned to the class average. If, however, the instructor adopts such a grading policy that the students who got 90 points or more, are assigned A's and the others are assigned B's, then probably he'd better use a SAX parser. The reason is, to assign each student a final grade, he do not need to wait for the entire document to be processed. He could immediately assign a grade to a student once the SAX parser reads the grade of this student. In the above analysis, we assumed that the instructor created no data structure of his own. What if he creates his own data structure, such as an array of strings to store the SSN and an array of integers to sto re the points ? In this case, I think SAX is a better choice, before this could save both memory and time as well, yet get the job done. Well, one more consideration on this example. What if what the instructor wants to do is not to print a list, but to save the original document back with the grade of each student updated ? In this case, a DOM parser should be a better choice no matter what grading policy he is adopting. He does not need to create any data structure of his own. What he needs to do is to first modify the DOM tree (i.e., set value to the 'grade' node) and then save the whole modified tree. If he choose to use a SAX parser instead of a DOM parser, then in this case he has to create a data structure which is almost as complicated as a DOM tree before he could get the job done.

An Example

Problem statement: Write a Java program to extract all the information about circles which are elements in a given XML document. We assume that each circle element has three child elements(i.e., x, y and radius) as well as a color attribute. A sample document is given below:

<?xml version="1.0"?> 
<!DOCTYPE shapes [
<!ELEMENT shapes (circle)*>
<!ELEMENT circle (x,y,radius)>
<!ELEMENT radius (#PCDATA)>
<!ATTLIST circle color CDATA #IMPLIED>

          <circle color="BLUE"> 
          <circle color="RED" >

Program with DOMparser

import org.w3c.dom.*;
import org.apache.xerces.parsers.DOMParser;

public class shapes_DOM {
   static int numberOfCircles = 0;   // total number of circles seen
   static int x[] = new int[1000];   // X-coordinates of the centers
   static int y[] = new int[1000];   // Y-coordinates of the centers  
   static int r[] = new int[1000];   // radius of the circle
   static String color[] = new String[1000];  // colors of the circles 

   public static void main(String[] args) {   

         // create a DOMParser
         DOMParser parser=new DOMParser();

         // get the DOM Document object
         Document doc=parser.getDocument();

         // get all the circle nodes
         NodeList nodelist = doc.getElementsByTagName("circle");
         numberOfCircles =  nodelist.getLength();

         // retrieve all info about the circles
         for(int i=0; i<nodelist.getLength(); i++) {

            // get one circle node
            Node node = nodelist.item(i);

            // get the color attribute 
            NamedNodeMap attrs = node.getAttributes();
            if(attrs.getLength() > 0)

            // get the child nodes of a circle node 
            NodeList childnodelist = node.getChildNodes();

            // get the x and y value 
            for(int j=0; j<childnodelist.getLength(); j++) {
               Node childnode = childnodelist.item(j);
               Node textnode = childnode.getFirstChild();//the only text node
               String childnodename=childnode.getNodeName(); 
                  x[i]= Integer.parseInt(textnode.getNodeValue().trim());
               else if(childnodename.equals("y")) 
                  y[i]= Integer.parseInt(textnode.getNodeValue().trim());
               else if(childnodename.equals("radius")) 
                  r[i]= Integer.parseInt(textnode.getNodeValue().trim());


         // print the result
         for(int i=0;i<numberOfCircles;i++) {
             String line="";

      }  catch (Exception e) {e.printStackTrace(System.err);}



Program with SAXparser

import org.xml.sax.*;
import org.xml.sax.helpers.DefaultHandler;
import org.apache.xerces.parsers.SAXParser;

public class shapes_SAX extends DefaultHandler {

   static int numberOfCircles = 0;   // total number of circles seen
   static int x[] = new int[1000];   // X-coordinates of the centers
   static int y[] = new int[1000];   // Y-coordinates of the centers
   static int r[] = new int[1000];   // radius of the circle
   static String color[] = new String[1000];  // colors of the circles

   static int flagX=0;    //to remember what element has occurred
   static int flagY=0;    //to remember what element has occurred
   static int flagR=0;    //to remember what element has occurred

   // main method 
   public static void main(String[] args) {   
         shapes_SAX SAXHandler = new shapes_SAX (); // an instance of this class
         SAXParser parser=new SAXParser();          // create a SAXParser object 
         parser.setContentHandler(SAXHandler);      // register with the ContentHandler 
      }  catch (Exception e) {e.printStackTrace(System.err);}  // catch exeptions

   // override the startElement() method
   public void startElement(String uri, String localName, 
                       String rawName, Attributes attributes) {
         if(rawName.equals("circle"))                      // if a circle element is seen
            color[numberOfCircles]=attributes.getValue("color");  // get the color attribute 

         else if(rawName.equals("x"))      // if a x element is seen set the flag as 1 
         else if(rawName.equals("y"))      // if a y element is seen set the flag as 2
         else if(rawName.equals("radius")) // if a radius element is seen set the flag as 3 

   // override the endElement() method
   public void endElement(String uri, String localName, String rawName) {
         // in this example we do not need to do anything else here
         if(rawName.equals("circle"))                       // if a circle element is ended 
            numberOfCircles +=  1;                          // increment the counter 

   // override the characters() method
   public void characters(char characters[], int start, int length) {
         String characterData = 
             (new String(characters,start,length)).trim(); // get the text

         if(flagX==1) {        // indicate this text is for <x> element 
             x[numberOfCircles] = Integer.parseInt(characterData);
         else if(flagY==1) {  // indicate this text is for <y> element 
             y[numberOfCircles] = Integer.parseInt(characterData);
         else if(flagR==1) {  // indicate this text is for <radius> element 
             r[numberOfCircles] = Integer.parseInt(characterData);

   // override the endDocument() method
   public void endDocument() {
         // when the end of document is seen, just print the circle info 
         for(int i=0;i<numberOfCircles;i++) {
             String line="";


Check if AJAX response data is empty/blank/null/undefined/0


This is an assignment statement, not a comparison. Also, "undefined" is a string, it's a property. Checking it is like this: if (data === undefined) (no quotes, otherwise it's a string value)

If it's not defined, you may be returning an empty string. You could try checking for a falsy value like if (!data) as well

SQL Statement using Where clause with multiple values

SELECT PersonName, songName, status
FROM table
WHERE name IN ('Holly', 'Ryan')

If you are using parametrized Stored procedure:

  1. Pass in comma separated string
  2. Use special function to split comma separated string into table value variable
  3. Use INNER JOIN ON t.PersonName = newTable.PersonName using a table variable which contains passed in names

Split value from one field to two

In case someone needs to run over a table and split a field:

  1. First we use the function mention above:
CREATE DEFINER=`root`@`localhost` FUNCTION `fn_split_str`($str VARCHAR(800), $delimiter VARCHAR(12), $position INT) RETURNS varchar(800) CHARSET utf8
                SUBSTRING_INDEX($str, $delimiter, $position),
                    SUBSTRING_INDEX($str, $delimiter, $position -1)
                ) + 1
    $delimiter, '');
  1. Second, we run in a while loop on the string until there isn't any results (I've added $id for JOIN clause):
CREATE DEFINER=`root`@`localhost` FUNCTION `fn_split_str_to_rows`($id INT, $str VARCHAR(800), $delimiter VARCHAR(12), $empty_table BIT) RETURNS int(11)

    DECLARE position INT;
    DECLARE val VARCHAR(800);
    SET position = 1;
    IF $empty_table THEN
        DROP TEMPORARY TABLE IF EXISTS tmp_rows;    
    END IF;
    SET val = fn_split_str($str, ',', position);
    CREATE TEMPORARY TABLE IF NOT EXISTS tmp_rows AS (SELECT $id as id, val as val where 1 = 2);
    WHILE (val IS NOT NULL and val != '') DO               
        INSERT INTO tmp_rows
        SELECT $id, val;
        SET position = position + 1;
        SET val = fn_split_str($str, ',', position);
    RETURN position - 1;
  1. Finally we can use it like that:
SELECT  SUM(fn_split_str_to_rows(ID, FieldToSplit, ',', 0))
FROM    MyTable;

SELECT * FROM tmp_rows;

You can use the id to join to other table.

In case you are only splitting one value you can use it like that

SELECT  fn_split_str_to_rows(null, 'AAA,BBB,CCC,DDD,EEE,FFF,GGG', ',', 1);
SELECT * FROM tmp_rows;

We don't need to empty the temporary table, the function will take care of that.

Clear form fields with jQuery

This won't handle cases where form input fields have non empty default values.

Something like should work


How to turn off magic quotes on shared hosting?

  1. Does it work if you remove the AddType line? I'm not quite sure why that's relevant to turning magic quotes off.

  2. If PHP isn't running under mod_php, htaccess won't work. Does it work as a CGI?

This is one for your hosting company really.

Is it possible to use an input value attribute as a CSS selector?

It is possible, if you're using a browser which supports the CSS :valid pseudo-class and the pattern validation attribute on inputs -- which includes most modern browsers except IE9.

For instance, to change the text of an input from black to green when the correct answer is entered:

input {_x000D_
  color: black;_x000D_
input:valid {_x000D_
  color: green;_x000D_
<p>Which country has fifty states?</p>_x000D_
<input type="text" pattern="^United States$">

CSS override rules and specificity

The important needs to be inside the ;

td.rule2 div {     background-color: #ffff00 !important; } 

in fact i believe this should override it

td.rule2 { background-color: #ffff00 !important; } 

What is the difference between JavaScript and ECMAScript?

In my understanding, ECMAScript is the "Theory" or "Specification", and Javascript is "Practicals" or "Implementation".

How to stop IIS asking authentication for default website on localhost

This is most likely a NT file permissions problem. IUSR_ needs to have file system permissions to read whatever file you're requesting (like /inetpub/wwwroot/index.htm).

If you still have trouble, check the IIS logs, typically at \windows\system32\logfiles\W3SVC*.

Background color not showing in print preview

If you download Bootstrap without the "Print media styles" option, you will not have this problem and do not have to remove the "@media print" code manually in your bootstrap.css file.

Decrypt password created with htpasswd

.htpasswd entries are HASHES. They are not encrypted passwords. Hashes are designed not to be decryptable. Hence there is no way (unless you bruteforce for a loooong time) to get the password from the .htpasswd file.

What you need to do is apply the same hash algorithm to the password provided to you and compare it to the hash in the .htpasswd file. If the user and hash are the same then you're a go.

"Least Astonishment" and the Mutable Default Argument

It's a performance optimization. As a result of this functionality, which of these two function calls do you think is faster?

def print_tuple(some_tuple=(1,2,3)):
    print some_tuple

print_tuple()        #1
print_tuple((1,2,3)) #2

I'll give you a hint. Here's the disassembly (see


0 LOAD_GLOBAL              0 (print_tuple)
3 CALL_FUNCTION            0
7 LOAD_CONST               0 (None)


 0 LOAD_GLOBAL              0 (print_tuple)
 3 LOAD_CONST               4 ((1, 2, 3))
 6 CALL_FUNCTION            1
10 LOAD_CONST               0 (None)

I doubt the experienced behavior has a practical use (who really used static variables in C, without breeding bugs ?)

As you can see, there is a performance benefit when using immutable default arguments. This can make a difference if it's a frequently called function or the default argument takes a long time to construct. Also, bear in mind that Python isn't C. In C you have constants that are pretty much free. In Python you don't have this benefit.

My Routes are Returning a 404, How can I Fix Them?

Have you tried to check if


was working? If so then make sure all your path's folders don't have any uppercase letters. I had the same situation and converting letters to lower case helped.

How to trim leading and trailing white spaces of a string?

There's a bunch of functions to trim strings in go.

See them there : Trim

Here's an example, adapted from the documentation, removing leading and trailing white spaces :

fmt.Printf("[%q]", strings.Trim(" Achtung  ", " "))

How can I overwrite file contents with new content in PHP?

Use file_put_contents()

file_put_contents('file.txt', 'bar');
echo file_get_contents('file.txt'); // bar
file_put_contents('file.txt', 'foo');
echo file_get_contents('file.txt'); // foo

Alternatively, if you're stuck with fopen() you can use the w or w+ modes:

'w' Open for writing only; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.

'w+' Open for reading and writing; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.

Java, How do I get current index/key in "for each" loop

Not possible in Java.

Here's the Scala way:

val m = List(5, 4, 2, 89)

for((el, i) <- m.zipWithIndex)
  println(el +" "+ i)

inherit from two classes in C#

Use composition:

class ClassC
    public ClassA A { get; set; }
    public ClassB B { get; set; }   

    public C (ClassA  a, ClassB  b)
        this.A = a;
        this.B = b;

Then you can call C.A.DoA(). You also can change the properties to an interface or abstract class, like public InterfaceA A or public AbstractClassA A.

delete all record from table in mysql

It’s because you tried to update a table without a WHERE that uses a KEY column.

The quick fix is to add SET SQL_SAFE_UPDATES=0; before your query :



close the safe update mode. Edit -> Preferences -> SQL Editor -> SQL Editor remove Forbid UPDATE and DELETE statements without a WHERE clause (safe updates) .

BTW you can use TRUNCATE TABLE tablename; to delete all the records .

How to convert a set to a list in python?

Whenever you are stuck in such type of problems, try to find the datatype of the element you want to convert first by using :


Then, Use:


to convert it to a list. You can use the newly built list like any normal list in python now.

Subquery returned more than 1 value.This is not permitted when the subquery follows =,!=,<,<=,>,>= or when the subquery is used as an expression

You can use IN operator as below

select * from dbo.books where isbn IN
(select isbn from dbo.lending where lended_date between @fdate and @tdate)

Find file in directory from command line

Yes, bash has filename completion mechanisms. I don't use them myself (too lazy to learn, and I don't find it necessary often enough to make it urgent), but the basic mechanism is to type the first few characters, and then a tab; this will extend the name as far as it can (perhaps not at all) as long as the name is unambiguous. There are a boatload of Emacs-style commands related to completion in the good ol' man page.

How to format numbers as currency string? Example: Using locales

This example shows some of the variations in localized number formats. In order to get the format of the language used in the user interface of your application, make sure to specify that language (and possibly some fallback languages) using the locales argument:

var number = 123456.789;

// German uses comma as decimal separator and period for thousands console.log(new Intl.NumberFormat('de-DE').format(number)); // ? 123.456,789

// Arabic in most Arabic speaking countries uses real Arabic digits console.log(new Intl.NumberFormat('ar-EG').format(number)); // ? ??????????

// India uses thousands/lakh/crore separators console.log(new Intl.NumberFormat('en-IN').format(number));

Serialize form data to JSON

If you do not care about repetitive form elements with the same name, then you can do:

var data = $("form.login").serializeArray();
var formData = _.object(_.pluck(data, 'name'), _.pluck(data, 'value'));

I am using Underscore.js here.

Is it better practice to use String.format over string Concatenation in Java?

I'd suggest that it is better practice to use String.format(). The main reason is that String.format() can be more easily localised with text loaded from resource files whereas concatenation can't be localised without producing a new executable with different code for each language.

If you plan on your app being localisable you should also get into the habit of specifying argument positions for your format tokens as well:

"Hello %1$s the time is %2$t"

This can then be localised and have the name and time tokens swapped without requiring a recompile of the executable to account for the different ordering. With argument positions you can also re-use the same argument without passing it into the function twice:

String.format("Hello %1$s, your name is %1$s and the time is %2$t", name, time)

How to chain scope queries with OR instead of AND?

the squeel gem provides an incredibly easy way to accomplish this (prior to this I used something like @coloradoblue's method):

names = ["Kroger", "Walmart", "Target", "Aldi"]
matching_stores = Grocery.where{name.like_any(names)}

Getting HTML elements by their attribute names

With prototypejs :



Both return an array

Python ValueError: too many values to unpack

self.materials is a dict and by default you are iterating over just the keys (which are strings).

Since self.materials has more than two keys*, they can't be unpacked into the tuple "k, m", hence the ValueError exception is raised.

In Python 2.x, to iterate over the keys and the values (the tuple "k, m"), we use self.materials.iteritems().

However, since you're throwing the key away anyway, you may as well simply iterate over the dictionary's values:

for m in self.materials.itervalues():

In Python 3.x, prefer dict.values() (which returns a dictionary view object):

for m in self.materials.values():

MySql Inner Join with WHERE clause

Yes you are right. You have placed WHERE clause wrong. You can only use one WHERE clause in single query so try AND for multiple conditions like this:

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

Converting XML to JSON using Python?

I published one on github a while back..

This converter is written in Python and will convert one or more XML files into JSON / JSONL files

It requires a XSD schema file to figure out nested json structures (dictionaries vs lists) and json equivalent data types.

python -x PurchaseOrder.xsd PurchaseOrder.xml

INFO - 2018-03-20 11:10:24 - Parsing XML Files..
INFO - 2018-03-20 11:10:24 - Processing 1 files
INFO - 2018-03-20 11:10:24 - Parsing files in the following order:
INFO - 2018-03-20 11:10:24 - ['PurchaseOrder.xml']
DEBUG - 2018-03-20 11:10:24 - Generating schema from PurchaseOrder.xsd
DEBUG - 2018-03-20 11:10:24 - Parsing PurchaseOrder.xml
DEBUG - 2018-03-20 11:10:24 - Writing to file PurchaseOrder.json
DEBUG - 2018-03-20 11:10:24 - Completed PurchaseOrder.xml

I also have a follow up xml to parquet converter that works in a similar fashion

Ubuntu says "bash: ./program Permission denied"

Try this:

sudo chmod +x program_name

Convert string to datetime in

As an alternative, if you put a space between the date and time, DateTime.Parse will recognize the format for you. That's about as simple as you can get it. (If ParseExact was still not being recognized)

How to retrieve an Oracle directory path?

select directory_path from dba_directories where upper(directory_name) = 'CSVDIR'

Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 71 bytes)

I had this problem. I searched the internet, took all advices, changes configurations, but the problem is still there. Finally with the help of the server administrator, he found that the problem lies in MySQL database column definition. one of the columns in the a table was assigned to 'Longtext' which leads to allocate 4,294,967,295 bites of memory. It seems working OK if you don't use MySqli prepare statement, but once you use prepare statement, it tries to allocate that amount of memory. I changed the column type to Mediumtext which needs 16,777,215 bites of memory space. The problem is gone. Hope this help.

UIView touch event in controller

Swift 4.2:

@IBOutlet weak var viewLabel1: UIView!
@IBOutlet weak var viewLabel2: UIView!
  override func viewDidLoad() {

    let myView = UITapGestureRecognizer(target: self, action: #selector(someAction(_:)))

 @objc func someAction(_ sender:UITapGestureRecognizer){
   viewLabel2.isHidden = true

How can I use UserDefaults in Swift?

Best way to use UserDefaults


  1. Create extension of UserDefaults
  2. Create enum with required Keys to store in local
  3. Store and retrieve the local data wherever you want


extension UserDefaults{

    //MARK: Check Login
    func setLoggedIn(value: Bool) {
        set(value, forKey: UserDefaultsKeys.isLoggedIn.rawValue)

    func isLoggedIn()-> Bool {
        return bool(forKey: UserDefaultsKeys.isLoggedIn.rawValue)

    //MARK: Save User Data
    func setUserID(value: Int){
        set(value, forKey: UserDefaultsKeys.userID.rawValue)

    //MARK: Retrieve User Data
    func getUserID() -> Int{
        return integer(forKey: UserDefaultsKeys.userID.rawValue)

enum for Keys used to store data

enum UserDefaultsKeys : String {
    case isLoggedIn
    case userID

Save in UserDefaults where you want

UserDefaults.standard.setLoggedIn(value: true)          // String
UserDefaults.standard.setUserID(value:!) // String

Retrieve data anywhere in app

print("ID : \(UserDefaults.standard.getUserID())")

Remove Values

UserDefaults.standard.removeObject(forKey: UserDefaultsKeys.userID) 

This way you can store primitive data in best

Update You need no use synchronize() to store the values. As @Moritz pointed out the it unnecessary and given the article about it.Check comments for more detail

Insert node at a certain position in a linked list C++

 void addToSpecific()
 int n;   
 int f=0;   //flag
 Node *temp=H;    //H-Head, T-Tail
    cout<<"Enter the Number"<<endl;
    Node *nn=new Node();
 else if(0==f)
    Node *nn=new Node();
 else if(1==f)
    Node *nn=new Node();

Object not found! The requested URL was not found on this server. localhost

You are not specified your project as right way.

  • So run your XAMPP control panel then start the apache and MySQL
  • Then note the ports.
  • For Example PORT 80: then you type your browser url as localhost:80\ press enter now your php basic Config page is visible.
  • Then create any folder on xampp\htdocs\YourFloderName Then create php file then save it and go to browser then type it localhost\YourFolderName now it listed the files click the file and it runs.

Change label text using JavaScript

Use .textContent instead.

I was struggling with changing the value of a label as well, until I tried this.

If this doesn't solve try inspecting the object to see what properties you can set by logging it to the console with console.dir as shown on this question: How can I log an HTML element as a JavaScript object?

C# Get/Set Syntax Usage

Assuming you have access to them (the properties you've declared are protected), you use them like this:

Person tom = new Person();
tom.Title = "A title";
string hisTitle = tom.Title;

These are properties. They're basically pairs of getter/setter methods (although you can have just a getter, or just a setter) with appropriate metadata. The example you've given is of automatically implemented properties where the compiler is adding a backing field. You can write the code yourself though. For example, the Title property you've declared is like this:

private string title; // Backing field
protected string Title
    get { return title; }  // Getter
    set { title = value; } // Setter

... except that the backing field is given an "unspeakable name" - one you can't refer to in your C# code. You're forced to go through the property itself.

You can make one part of a property more restricted than another. For example, this is quite common:

private string foo;
public string Foo
    get { return foo; }
    private set { foo = value; }

or as an automatically implemented property:

public string Foo { get; private set; }

Here the "getter" is public but the "setter" is private.

Google Apps Script to open a URL

Google Apps Script will not open automatically web pages, but it could be used to display a message with links, buttons that the user could click on them to open the desired web pages or even to use the Window object and methods like addEventListener() to open URLs.

It's worth to note that UiApp is now deprecated. From Class UiApp - Google Apps Script - Google Developers

Deprecated. The UI service was deprecated on December 11, 2014. To create user interfaces, use the HTML service instead.

The example in the HTML Service linked page is pretty simple,

// Use this code for Google Docs, Forms, or new Sheets.
function onOpen() {
  SpreadsheetApp.getUi() // Or DocumentApp or FormApp.
      .addItem('Open', 'openDialog')

function openDialog() {
  var html = HtmlService.createHtmlOutputFromFile('index')
  SpreadsheetApp.getUi() // Or DocumentApp or FormApp.
      .showModalDialog(html, 'Dialog title');

A customized version of index.html to show two hyperlinks

<a href='' target='_blank'>Stack Overflow</a>
<a href='' target='_blank'>Meta Stack Overflow</a>

Securing a password in a properties file

The poor mans compromise solution is to use a simplistic multi signature approach.

For Example the DBA sets the applications database password to a 50 character random string. TAKqWskc4ncvKaJTyDcgAHq82X7tX6GfK2fc386bmNw3muknjU

He or she give half the password to the application developer who then hard codes it into the java binary.

private String pass1 = "TAKqWskc4ncvKaJTyDcgAHq82"

The other half of the password is passed as a command line argument. the DBA gives pass2 to the system support or admin person who either enters it a application start time or puts it into the automated application start up script.

java -jar /myapplication.jar -pass2 X7tX6GfK2fc386bmNw3muknjU

When the application starts it uses pass1 + pass2 and connects to the database.

This solution has many advantages with out the downfalls mentioned.

You can safely put half the password in a command line arguments as reading it wont help you much unless you are the developer who has the other half of the password.

The DBA can also still change the second half of the password and the developer need not have to re-deploy the application.

The source code can also be semi public as reading it and the password will not give you application access.

You can further improve the situation by adding restrictions on the IP address ranges the database will accept connections from.

Is there any sed like utility for cmd.exe?

If you don't want to install anything (I assume you want to add the script into some solution/program/etc that will be run in other machines), you could try creating a vbs script (lets say, replace.vbs):

Const ForReading = 1
Const ForWriting = 2

strFileName = Wscript.Arguments(0)
strOldText = Wscript.Arguments(1)
strNewText = Wscript.Arguments(2)

Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objFile = objFSO.OpenTextFile(strFileName, ForReading)

strText = objFile.ReadAll
strNewText = Replace(strText, strOldText, strNewText)

Set objFile = objFSO.OpenTextFile(strFileName, ForWriting)
objFile.Write strNewText

And you run it like this:

cscript replace.vbs "C:\One.txt" "Robert" "Rob"

Which is similar to the sed version provided by "bill weaver", but I think this one is more friendly in terms of special (' > < / ) characters.

Btw, I didn't write this, but I can't recall where I got it from.

Array definition in XML?

No, there is no simpler way. You only can lose the type=array.


What is the difference between an annotated and unannotated tag?

Push annotated tags, keep lightweight local

man git-tag says:

Annotated tags are meant for release while lightweight tags are meant for private or temporary object labels.

And certain behaviors do differentiate between them in ways that this recommendation is useful e.g.:

  • annotated tags can contain a message, creator, and date different than the commit they point to. So you could use them to describe a release without making a release commit.

    Lightweight tags don't have that extra information, and don't need it, since you are only going to use it yourself to develop.

  • git push --follow-tags will only push annotated tags
  • git describe without command line options only sees annotated tags

Internals differences

  • both lightweight and annotated tags are a file under .git/refs/tags that contains a SHA-1

  • for lightweight tags, the SHA-1 points directly to a commit:

    git tag light
    cat .git/refs/tags/light

    prints the same as the HEAD's SHA-1.

    So no wonder they cannot contain any other metadata.

  • annotated tags point to a tag object in the object database.

    git tag -as -m msg annot
    cat .git/refs/tags/annot

    contains the SHA of the annotated tag object:


    and then we can get its content with:

    git cat-file -p c1d7720e99f9dd1d1c8aee625fd6ce09b3a81fef

    sample output:

    object 4284c41353e51a07e4ed4192ad2e9eaada9c059f
    type commit
    tag annot
    tagger Ciro Santilli <[email protected]> 1411478848 +0200
    Version: GnuPG v1.4.11 (GNU/Linux)

    And this is how it contains extra metadata. As we can see from the output, the metadata fields are:

    A more detailed analysis of the format is present at: What is the format of a git tag object and how to calculate its SHA?


  • Determine if a tag is annotated:

    git cat-file -t tag


    • commit for lightweight, since there is no tag object, it points directly to the commit
    • tag for annotated, since there is a tag object in that case
  • List only lightweight tags: How can I list all lightweight tags?

Spacing between elements

It depends on what exactly you want to accomplish. Let's assume you have this structure:

<p style="width:400px;">
    Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem. Nulla consequat massa quis enim. Donec pede justo, fringilla vel, aliquet nec, vulputate eget, arcu. In enim justo, rhoncus ut, imperdiet a, venenatis vitae, justo. Nullam dictum felis eu pede mollis pretium. Integer tincidunt. Cras dapibus. Vivamus elementum semper nisi. Aenean vulputate eleifend tellus. Aenean leo ligula, porttitor eu, consequat vitae, eleifend ac, enim. Aliquam lorem ante, dapibus in, viverra quis, feugiat a, tellus. Phasellus viverra nulla ut metus varius laoreet.

If you want the space between the single lines to be bigger, you should increase


If you want the space at the end to be bigger, you should increase


If you want the space at the end to be bigger, but have the background fill the space (or the border around the space) use


Of course, there are also the corresponding values for space on the top:


Some examples:

<p style="line-height: 30px; width: 300px; border: 1px solid black;">
     Space between single lines 
     Space between single lines
     Space between single lines
     Space between single lines
     Space between single lines
     Space between single lines
     Space between single lines
     Space between single lines
<p style="margin-bottom: 30px; width: 300px; border: 1px solid black;">
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
     Space at the bottom, outside of the border
<p style="padding-bottom: 30px; width: 300px; border: 1px solid black;">
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border
     Space at the bottom, inside of the border

here you can see this code in action:

Of course you should put your styles in a separate stylesheet, the inline code was just to show the effect.

here you have a little schematic demonstration of what which value affects:

           content                 +
                                   |      padding-bottom
                  <----------------+      +
           content                        |    border-bottom
                                          |    +
                                          |    |
        +-------------+<------------------+    |       margin-bottom
                                               |       +
     +===================+ <-------------------+       |
  +-------------------------+ <------------------------+

Difference between no-cache and must-revalidate

I believe that must-revalidate means :

Once the cache expires, refuse to return stale responses to the user even if they say that stale responses are acceptable.

Whereas no-cache implies :

must-revalidate plus the fact the response becomes stale right away.

If a response is cacheable for 10 seconds, then must-revalidate kicks in after 10 seconds, whereas no-cache implies must-revalidate after 0 seconds.

At least, that's my interpretation.

How do I get a string format of the current date time, in python?

>>> import datetime
>>> now =
>>> now.strftime("%B %d, %Y")
'July 23, 2010'

Linux bash script to extract IP address

Just a note, since I just spent some time trouble-shooting a botched upgrade on a server. Turned out, that (years ago) I had implemented a test to see if dynamically added interfaces (e.g. eth0:1) were present, and if so, I would bind certain proggis to the 'main' IP on eth0. Basically it was a variation on the 'ifconfig|grep...|sed... ' solution (plus checking for 'eth0:' presence).
The upgrade brought new net-tools, and with it the output has changed slightly:

old ifconfig:

eth0      Link encap:Ethernet  HWaddr 42:01:0A:F0:B0:1D
          inet addr:  Bcast:  Mask:

whereas the new version will display this:

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1460
      inet  netmask  broadcast

rendering the hunt for 'eth0:' as well as 'inet addr:' search busted (never mind interfaces called 'em0','br0' or 'wlan0'...). Sure you could check for 'inet ' (or 'inet6'), and make the addr: part optional, but looking closer, you'll see that more or less everything has changed, 'Mask' is now 'netmask',...

The 'ip route ...' suggestion's pretty nifty - so maybe:

_MyIP="$( ip route get | awk 'NR==1 {print $NF}' )"
if [ "A$_MyIP" == "A" ]
    _MyIPs="$( hostname -I )"
    for _MyIP in "$_MyIPs"
        echo "Found IP: \"$_MyIP\""
    echo "Found IP: $_MyIP"

Well, something of that sort anyway. Since all proposed solutions seem to have circumstances where they fail, check for possible edge cases - no eth, multiple eth's & lo's, when would 'hostname -i' fail,... and then decide on best solution, check it worked, otherwise 2nd best.

Cheers 'n' beers!

How can I check whether a numpy array is empty or not?

NumPy's main object is the homogeneous multidimensional array. In Numpy dimensions are called axes. The number of axes is rank. Numpy's array class is called ndarray. It is also known by the alias array. The more important attributes of an ndarray object are:

the number of axes (dimensions) of the array. In the Python world, the number of dimensions is referred to as rank.

the dimensions of the array. This is a tuple of integers indicating the size of the array in each dimension. For a matrix with n rows and m columns, shape will be (n,m). The length of the shape tuple is therefore the rank, or number of dimensions, ndim.

the total number of elements of the array. This is equal to the product of the elements of shape.

What is :: (double colon) in Python when subscripting sequences?


This visual example will show you how to a neatly select elements in a NumPy Matrix (2 dimensional array) in a pretty entertaining way (I promise). Step 2 below illustrate the usage of that "double colons" :: in question.

(Caution: this is a NumPy array specific example with the aim of illustrating the a use case of "double colons" :: for jumping of elements in multiple axes. This example does not cover native Python data structures like List).

One concrete example to rule them all...

Say we have a NumPy matrix that looks like this:

In [1]: import numpy as np

In [2]: X = np.arange(100).reshape(10,10)

In [3]: X
array([[ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
       [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
       [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
       [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
       [50, 51, 52, 53, 54, 55, 56, 57, 58, 59],
       [60, 61, 62, 63, 64, 65, 66, 67, 68, 69],
       [70, 71, 72, 73, 74, 75, 76, 77, 78, 79],
       [80, 81, 82, 83, 84, 85, 86, 87, 88, 89],
       [90, 91, 92, 93, 94, 95, 96, 97, 98, 99]])

Say for some reason, your boss wants you to select the following elements:

enter image description here

"But How???"... Read on! (We can do this in a 2-step approach)

Step 1 - Obtain subset

Specify the "start index" and "end index" in both row-wise and column-wise directions.

enter image description here

In code:

In [5]: X2 = X[2:9,3:8]

In [6]: X2
array([[23, 24, 25, 26, 27],
       [33, 34, 35, 36, 37],
       [43, 44, 45, 46, 47],
       [53, 54, 55, 56, 57],
       [63, 64, 65, 66, 67],
       [73, 74, 75, 76, 77],
       [83, 84, 85, 86, 87]])

Notice now we've just obtained our subset, with the use of simple start and end indexing technique. Next up, how to do that "jumping"... (read on!)

Step 2 - Select elements (with the "jump step" argument)

We can now specify the "jump steps" in both row-wise and column-wise directions (to select elements in a "jumping" way) like this:

enter image description here

In code (note the double colons):

In [7]: X3 = X2[::3, ::2]

In [8]: X3
array([[23, 25, 27],
       [53, 55, 57],
       [83, 85, 87]])

We have just selected all the elements as required! :)

 Consolidate Step 1 (start and end) and Step 2 ("jumping")

Now we know the concept, we can easily combine step 1 and step 2 into one consolidated step - for compactness:

In [9]: X4 = X[2:9,3:8][::3,::2]

    In [10]: X4
    array([[23, 25, 27],
           [53, 55, 57],
           [83, 85, 87]])


Can I force a page break in HTML printing?

I needed a page break after every 3rd row while we use print command on browser.

I added

<div style='page-break-before: always;'></div>

after every 3rd row and my parent div have display: flex; so I removed display: flex; and it was working as I want.

Check if object value exists within a Javascript array of objects and if not add a new object to array

This small snippets works for me..

const arrayOfObject = [{ id: 1, name: 'john' }, {id: 2, name: 'max'}];

const checkUsername = obj => === 'max';


android edittext onchange listener

I have done it using AutotextView:

AutotextView textView = (AutotextView) findViewById(;
textView.addTextChangedListener(new TextWatcher() {

    public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
        seq = cs;

    public void beforeTextChanged(CharSequence s, int arg1, int arg2, int arg3) {


    public void afterTextChanged(Editable arg0) {
        new SearchTask().execute(seq.toString().trim());


Electron: jQuery is not defined

As seen in the problem is caused because of this code:

if ( typeof module === "object" && typeof module.exports === "object" ) {
  // set jQuery in `module`
} else {
  // set jQuery in `window`

The jQuery code "sees" that its running in a CommonJS environment and ignores window.

The solution is really easy, instead of loading jQuery through <script src="...">, you should load like this:

<script>window.$ = window.jQuery = require('./path/to/jquery');</script>

Note: the dot before the path is required, since it indicates that it's the current directory. Also, remember to load jQuery before loading any other plugin that depends on it.

How to use font-family lato?

Download it from here and extract LatoOFL.rar then go to TTF and open this font-face-generator click at Choose File choose font which you want to use and click at generate then download it and then go html file open it and you see the code like this

@font-face {
        font-family: "Lato Black";
        src: url('698242188-Lato-Bla.eot');
        src: url('698242188-Lato-Bla.eot?#iefix') format('embedded-opentype'),
        url('698242188-Lato-Bla.svg#Lato Black') format('svg'),
        url('698242188-Lato-Bla.woff') format('woff'),
        url('698242188-Lato-Bla.ttf') format('truetype');
        font-weight: normal;
        font-style: normal;
    font-family: "Lato Black";
    direction: ltr;

change the src code and give the url where your this font directory placed, now you can use it at your website...

If you don't want to download it use this

<link type='text/css' href=',700' />

How to place div side by side

There are many ways to do what you're asking for:

  1. Using CSS float property:

 <div style="width: 100%; overflow: hidden;">
     <div style="width: 600px; float: left;"> Left </div>
     <div style="margin-left: 620px;"> Right </div>

  1. Using CSS display property - which can be used to make divs act like a table:

<div style="width: 100%; display: table;">
    <div style="display: table-row">
        <div style="width: 600px; display: table-cell;"> Left </div>
        <div style="display: table-cell;"> Right </div>

There are more methods, but those two are the most popular.

Use JSTL forEach loop's varStatus as an ID

The variable set by varStatus is a LoopTagStatus object, not an int. Use:

<div id="divIDNo${theCount.index}">

To clarify:

  • ${theCount.index} starts counting at 0 unless you've set the begin attribute
  • ${theCount.count} starts counting at 1

How do I uninstall nodejs installed from pkg (Mac OS X)?

This is the full list of commands I used (Many thanks to the posters above):

sudo rm -rf /usr/local/lib/node /usr/local/lib/node_modules /var/db/receipts/org.nodejs.*
sudo rm -rf /usr/local/include/node /Users/$USER/.npm
sudo rm /usr/local/bin/node
sudo rm /usr/local/share/man/man1/node.1
brew install node

Highcharts - how to have a chart with dynamic height?

What if you hooked the window resize event:


See example fiddle here.

Highcharts API Reference : setSize().

Could not find an implementation of the query pattern

You are missing an equality:

var query = (from p in tblPersoon where == 5 select p).Single();

where clause must result in a boolean.

OR you should not be using where at all:

var query = (from p in tblPersoon select p).Single();

Jquery set radio button checked, using id and class selectors

" a class and a div."

I assume when you say "div" you mean "id"? Try this:

$('#test2.test1').prop('checked', true);

No need to muck about with your [attributename=value] style selectors because id has its own format as does class, and they're easily combined although given that id is supposed to be unique it should be enough on its own unless your meaning is "select that element only if it currently has the specified class".

Or more generally to select an input where you want to specify a multiple attribute selector:

$('input:radio[class=test1][id=test2]').prop('checked', true);

That is, list each attribute with its own square brackets.

Note that unless you have a pretty old version of jQuery you should use .prop() rather than .attr() for this purpose.

Get only filename from url in php without any variable values which exist in the url

Is better to use parse_url to retrieve only the path, and then getting only the filename with the basename. This way we also avoid query parameters.


// url to inspect
$url = '';

// parsed path
$path = parse_url($url, PHP_URL_PATH);

// extracted basename
echo basename($path);


Is somewhat similar to Sultan answer excepting that I'm using component parse_url parameter, to obtain only the path.

Copy Notepad++ text with formatting?

Select the text.

Right Click.

Plugin Commands -> Copy Text with Syntax Highlighting

Paste it into Word or whatever.

ASP MVC href to a controller/view

Try the following:

<a asp-controller="Users" asp-action="Index"></a>

(Valid for ASP.NET 5 and MVC 6)

Error: Module not specified (IntelliJ IDEA)

this is how I fix this issue my project structure module enter image description here plus button enter image description here import module,and find the module's pom enter image description here
5.make sure you select the module you want to import,then next next finish:) enter image description here

Go / golang time.Now().UnixNano() convert to milliseconds?

I think it's better to round the time to milliseconds before the division.

func makeTimestamp() int64 {
    return time.Now().Round(time.Millisecond).UnixNano() / (int64(time.Millisecond)/int64(time.Nanosecond))

Here is an example program:

package main

import (

func main() {
        fmt.Println(unixMilli(time.Unix(0, 123400000)))
        fmt.Println(unixMilli(time.Unix(0, 123500000)))
        m := makeTimestampMilli()
        fmt.Println(time.Unix(m/1e3, (m%1e3)*int64(time.Millisecond)/int64(time.Nanosecond)))

func unixMilli(t time.Time) int64 {
        return t.Round(time.Millisecond).UnixNano() / (int64(time.Millisecond) / int64(time.Nanosecond))

func makeTimestampMilli() int64 {
        return unixMilli(time.Now())

The above program printed the result below on my machine:

2016-08-28 01:00:24.305 +0900 JST

Simple and fast method to compare images for similarity

If you want to get an index about the similarity of the two pictures, I suggest you from the metrics the SSIM index. It is more consistent with the human eye. Here is an article about it: Structural Similarity Index

It is implemented in OpenCV too, and it can be accelerated with GPU: OpenCV SSIM with GPU

Batch file to move files to another directory

Suppose there's a file test.txt in Root Folder, and want to move it to \TxtFolder,

You can try

move %~dp0\test.txt %~dp0\TxtFolder


reference answer: relative path in BAT script

Change grid interval and specify tick labels in Matplotlib

There are several problems in your code.

First the big ones:

  1. You are creating a new figure and a new axes in every iteration of your loop ? put fig = plt.figure and ax = fig.add_subplot(1,1,1) outside of the loop.

  2. Don't use the Locators. Call the functions ax.set_xticks() and ax.grid() with the correct keywords.

  3. With plt.axes() you are creating a new axes again. Use ax.set_aspect('equal').

The minor things: You should not mix the MATLAB-like syntax like plt.axis() with the objective syntax. Use ax.set_xlim(a,b) and ax.set_ylim(a,b)

This should be a working minimal example:

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)

# Major ticks every 20, minor ticks every 5
major_ticks = np.arange(0, 101, 20)
minor_ticks = np.arange(0, 101, 5)

ax.set_xticks(minor_ticks, minor=True)
ax.set_yticks(minor_ticks, minor=True)

# And a corresponding grid

# Or if you want different settings for the grids:
ax.grid(which='minor', alpha=0.2)
ax.grid(which='major', alpha=0.5)

Output is this:


Getting date format m-d-Y H:i:s.u from milliseconds

This is based on answer from ArchCodeMonkey.

But just simplified, if you just want something quick that works.

function DateTime_us_utc(){
    return DateTime::createFromFormat('U.u', number_format(microtime(true), 6, '.', ''));
function DateTime_us(){
    $now = DateTime_us_utc();
    return $now->setTimeZone(new DateTimeZone(date_default_timezone_get()));

So for me then

$now = DateTime_us();
$now->format("m-d-Y H:i:s.u");

Disable all table constraints in Oracle

To take in count the dependencies between the constraints:

SET Serveroutput ON
    FOR c IN
    (SELECT c.owner,c.table_name,c.constraint_name
    FROM user_constraints c,user_tables t
    WHERE c.table_name=t.table_name
    AND c.status='ENABLED'
    ORDER BY c.constraint_type DESC,c.last_change DESC
        FOR D IN
        (SELECT P.Table_Name Parent_Table,C1.Table_Name Child_Table,C1.Owner,P.Constraint_Name Parent_Constraint,
            c1.constraint_name Child_Constraint
        FROM user_constraints p
        JOIN user_constraints c1 ON(p.constraint_name=c1.r_constraint_name)
        OR p.constraint_type='U')
        AND c1.constraint_type='R'
        AND p.table_name=UPPER(c.table_name)
            dbms_output.put_line('. Disable the constraint ' || d.Child_Constraint ||' (on table '||d.owner || '.' ||
            d.Child_Table || ')') ;
            dbms_utility.exec_ddl_statement('alter table ' || d.owner || '.' ||d.Child_Table || ' disable constraint ' ||
            d.Child_Constraint) ;
        END LOOP;

Best way to remove items from a collection

This is my generic solution

public static IEnumerable<T> Remove<T>(this IEnumerable<T> items, Func<T, bool> match)
        var list = items.ToList();
        for (int idx = 0; idx < list.Count(); idx++)
            if (match(list[idx]))
                idx--; // the list is 1 item shorter
        return list.AsEnumerable();

It would look much simpler if extension methods support passing by reference ! usage:

var result = string[]{"mike", "john", "ali"}
result = result.Remove(x => x.Username == "mike").ToArray();
Assert.IsTrue(result.Length == 2);

EDIT: ensured that the list looping remains valid even when deleting items by decrementing the index (idx).

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

In some cases data was not encoded into JSON format, so you need to encode it first e.g


Later you will use json Parse in your JS, like


How to define several include path in Makefile

You have to prepend every directory with -I:

INC=-I/usr/informix/incl/c++ -I/opt/informix/incl/public

Cross browser method to fit a child div to its parent's width

If you put position:relative; on the outer element, the inner element will place itself according to this one. Then a width:auto; on the inner element will be the same as the width of the outer.

Launch an app from within another (iPhone)

In order to let you open your application from another, you'll need to make changes in both applications. Here are the steps using Swift 3 with iOS 10 update:

1. Register your application that you want to open

Update the Info.plist by defining your application's custom and unique URL Scheme.

enter image description here

Note that your scheme name should be unique, otherwise if you have another application with the same URL scheme name installed on your device, then this will be determined runtime which one gets opened.

2. Include the previous URL scheme in your main application

You'll need to specify the URL scheme you want the app to be able to use with the canOpenURL: method of the UIApplication class. So open the main application's Info.plist and add the other application's URL scheme to LSApplicationQueriesSchemes. (Introduced in iOS 9.0)

enter image description here

3. Implement the action that opens your application

Now everything is set up, so you're good to write your code in your main application that opens your other app. This should looks something like this:

let appURLScheme = "MyAppToOpen://"

guard let appURL = URL(string: appURLScheme) else {

if UIApplication.shared.canOpenURL(appURL) {

    if #available(iOS 10.0, *) {
    else {
else {
    // Here you can handle the case when your other application cannot be opened for any reason.

Note that these changes requires a new release if you want your existing app (installed from AppStore) to open. If you want to open an application that you've already released to Apple AppStore, then you'll need to upload a new version first that includes your URL scheme registration.

how to read all files inside particular folder

Try this It is working for me..

The syntax is GetFiles(string path, string searchPattern);

var filePath = Server.MapPath("~/App_Data/");
string[] filePaths = Directory.GetFiles(@filePath, "*.*");

This code will return all the files inside App_Data folder.

The second parameter . indicates the searchPattern with File Extension where the first * is for file name and second is for format of the file or File Extension like (*.png - any file name with .png format.

How do I use shell variables in an awk script?

You can utilize ARGV:

awk 'BEGIN {print ARGV[1]}' "$v"

Note that if you are going to continue into the body, you will need to adjust ARGC:

awk 'BEGIN {ARGC--} {print ARGV[2], $0}' file "$v"

How can I use LTRIM/RTRIM to search and replace leading/trailing spaces?

To remove spaces from left/right, use LTRIM/RTRIM. What you had

UPDATE *tablename*
   SET *columnname* = LTRIM(RTRIM(*columnname*));

would have worked on ALL the rows. To minimize updates if you don't need to update, the update code is unchanged, but the LIKE expression in the WHERE clause would have been

UPDATE [tablename]
   SET [columnname] = LTRIM(RTRIM([columnname]))
 WHERE 32 in (ASCII([columname]), ASCII(REVERSE([columname])));

Note: 32 is the ascii code for the space character.

I do not understand how execlp() works in Linux

The limitation of execl is that when executing a shell command or any other script that is not in the current working directory, then we have to pass the full path of the command or the script. Example:

execl("/bin/ls", "ls", "-la", NULL);

The workaround to passing the full path of the executable is to use the function execlp, that searches for the file (1st argument of execlp) in those directories pointed by PATH:

execlp("ls", "ls", "-la", NULL);

xlsxwriter: is there a way to open an existing worksheet in my workbook?

You can use the workbook.get_worksheet_by_name() feature:

According to the feature has been added on May 13, 2016.

"Release 0.8.7 - May 13 2016

-Fix for issue when inserting read-only images on Windows. Issue #352.

-Added get_worksheet_by_name() method to allow the retrieval of a worksheet from a workbook via its name.

-Fixed issue where internal file creation and modification dates were in the local timezone instead of UTC."

Jenkins pipeline if else not working

It requires a bit of rearranging, but when does a good job to replace conditionals above. Here's the example from above written using the declarative syntax. Note that test3 stage is now two different stages. One that runs on the master branch and one that runs on anything else.

stage ('Test 3: Master') {
    when { branch 'master' }
    steps { 
        echo 'I only execute on the master branch.' 

stage ('Test 3: Dev') {
    when { not { branch 'master' } }
    steps {
        echo 'I execute on non-master branches.'

How do I escape ampersands in XML so they are rendered as entities in HTML?

How about using the unicode \u0026? Works for me in my android XML files. If problems arise, someone let me know.

Regex: match word that ends with "Id"

Regex ids = new Regex(@"\w*Id\b", RegexOptions.None);

\b means "word break" and \w means any word character. So \w*Id\b means "{stuff}Id". By not including RegexOptions.IgnoreCase, it will be case sensitive.

Aliases in Windows command prompt

Naturally, I would not rest until I have the most convenient solution of all. Combining the very many answers and topics on the vast internet, here is what you can have.

  • Loads automatically with every instance of cmd
  • Doesn't require keyword DOSKEY for aliases
    example: ls=ls --color=auto $*

Note that this is largely based on Argyll's answer and comments, definitely read it to understand the concepts.

How to make it work?

  1. Create a mac macro file with the aliases
    you can even use a bat/cmd file to also run other stuff (similar to .bashrc in linux)
  2. Register it in Registry to run on each instance of cmd
      or run it via shortcut only if you want

Example steps:

;= This file is registered via registry to auto load with each instance of cmd.
;================================ general info ================================
;=  -  how to set it up?
;=  -  example doskey macrofile
;========================= loading with cmd shortcut ==========================
;= create a shortcut with the following target :
;= %comspec% /k "(doskey /macrofile=%userprofile%\cmd\aliases.mac)"

alias=subl %USERPROFILE%\cmd\aliases.mac
hosts=runas /noprofile /savecred /user:QWERTY-XPS9370\administrator "subl C:\Windows\System32\drivers\etc\hosts" > NUL

p=@echo "~~ powercfg -devicequery wake_armed ~~" && powercfg -devicequery wake_armed && @echo "~~ powercfg -requests ~~ " && powercfg -requests && @echo "~~ powercfg -waketimers ~~"p && powercfg -waketimers

ls=ls --color=auto $*
ll=ls -l --color=auto $*
la=ls -la --color=auto $*
grep=grep --color $*

cdr=cd C:\repos
cde=cd C:\repos\esquire
cdd=cd C:\repos\dixons
cds=cd C:\repos\stekkie
cdu=cd C:\repos\uplus
cduo=cd C:\repos\uplus\oxbridge-fe
cdus=cd C:\repos\uplus\stratus

npx=npx --no-install $*
npxi=npx $*
npr=npm run $*

now=vercel $*

;=only in bash
;=alias whereget='_whereget() { A=$1; B=$2; shift 2; eval \"$(where $B | head -$A | tail -1)\" $@; }; _whereget'

history=doskey /history
;= h [SHOW | SAVE | TSAVE ]
h=IF ".$*." == ".." (echo "usage: h [ SHOW | SAVE | TSAVE ]" && doskey/history) ELSE (IF /I "$1" == "SAVE" (doskey/history $g$g %USERPROFILE%\cmd\history.log & ECHO Command history saved) ELSE (IF /I "$1" == "TSAVE" (echo **** %date% %time% **** >> %USERPROFILE%\cmd\history.log & doskey/history $g$g %USERPROFILE%\cmd\history.log & ECHO Command history saved) ELSE (IF /I "$1" == "SHOW" (type %USERPROFILE%\cmd\history.log) ELSE (doskey/history))))
loghistory=doskey /history >> %USERPROFILE%\cmd\history.log

;=exit=echo **** %date% %time% **** >> %USERPROFILE%\cmd\history.log & doskey/history $g$g %USERPROFILE%\cmd\history.log & ECHO Command history saved, exiting & timeout 1 & exit $*
exit=echo **** %date% %time% **** >> %USERPROFILE%\cmd\history.log & doskey/history $g$g %USERPROFILE%\cmd\history.log & exit $*

;============================= :end ============================
;= rem ******************************************************************
;= rem * EOF - Don't remove the following line.  It clears out the ';'
;= rem * macro. We're using it because there is no support for comments
;= rem * in a DOSKEY macro file.
;= rem ******************************************************************

Now you have three options:

  • a) load manually with shortcut

    create a shortcut to cmd.exe with the following target :
    %comspec% /k "(doskey /macrofile=%userprofile%\cmd\aliases.mac)"

  • b) register just the aliases.mac macrofile

  • c) register a regular cmd/bat file to also run arbitrary commands
    see example cmdrc.cmd file at the bottom

note: Below, Autorun_ is just a placeholder key which will not do anything. Pick one and rename the other.

Manually edit registry at this path:

[HKEY_CURRENT_USER\Software\Microsoft\Command Processor]
  Autorun    REG_SZ    doskey /macrofile=%userprofile%\cmd\aliases.mac
  Autorun_    REG_SZ    %USERPROFILE%\cmd\cmdrc.cmd

Or import reg file:

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Command Processor]
"Autorun"="doskey /macrofile=%userprofile%\\cmd\\aliases.mac"
%userprofile%/cmd/cmdrc.cmd you don't need this file if you decided for b) above
:: This file is registered via registry to auto load with each instance of cmd.

@echo off
doskey /macrofile=%userprofile%\cmd\aliases.mac

:: put other commands here

Remove all special characters, punctuation and spaces from string

import re
my_string = """Strings are amongst the most popular data types in Python. We can create the strings by enclosing characters in quotes. Python treats single quotes the 

same as double quotes."""

# if we need to count the word python that ends with or without ',' or '.' at end

count = 0
for i in text:
    if i.endswith("."):
        text[count] = re.sub("^([a-z]+)(.)?$", r"\1", i)
    count += 1
print("The count of Python : ", text.count("python"))

Is there a method that tells my program to quit?

One way is to do:


You will have to import sys of course.

Another way is to break out of your infinite loop. For example, you could do this:

while True:
    choice = get_input()
    if choice == "a":
        # do something
    elif choice == "q":

Yet another way is to put your main loop in a function, and use return:

def run():
    while True:
        choice = get_input()
        if choice == "a":
            # do something
        elif choice == "q":

if __name__ == "__main__":

The only reason you need the run() function when using return is that (unlike some other languages) you can't directly return from the main part of your Python code (the part that's not inside a function).

How to disable 'X-Frame-Options' response header in Spring Security?

If you're using Spring Boot, the simplest way to disable the Spring Security default headers is to use security.headers.* properties. In particular, if you want to disable the X-Frame-Options default header, just add the following to your


There is also security.headers.cache, security.headers.content-type, security.headers.hsts and security.headers.xss properties that you can use. For more information, take a look at SecurityProperties.

What values for checked and selected are false?

The checked and selected attributes are allowed only two values, which are a copy of the attribute name and (from HTML 5 onwards) an empty string. Giving any other value is an error.

If you don't want to set the attribute, then the entire attribute must be omitted.

Note that in HTML 4 you may omit everything except the value. HTML 5 changed this to omit everything except the name (which makes no practical difference).

Thus, the complete (aside from variations in cAsE) set of valid representations of the attribute are:

<input ... checked="checked"> <!-- All versions of HTML / XHTML -->
<input ...          checked > <!-- Only HTML 4.01 and earlier -->
<input ... checked          > <!-- Only HTML 5 and later -->
<input ... checked=""       > <!-- Only HTML 5 and later -->

Documents served as text/html (HTML or XHTML) will be fed through a tag soup parser, and the presence of a checked attribute (with any value) will be treated as "This element should be checked". Thus, while invalid, checked="true", checked="yes", and checked="false" will all trigger the checked state.

I've not had any inclination to find out what error recovery mechanisms are in place for XML parsing mode should a different value be given to the attribute, but I would expect that the legacy of HTML and/or simple error recovery would treat it in the same way: If the attribute is there then the element is checked.

(And all the above applies equally to selected as it does to checked.)

How to load a UIView using a nib file created with Interface Builder

I made a category that I like:


#import <UIKit/UIKit.h>

@interface UIView (NibInitializer)
- (instancetype)initWithNibNamed:(NSString *)nibNameOrNil;


#import "UIView+NibInitializer.h"

@implementation UIView (NibInitializer)

- (instancetype)initWithNibNamed:(NSString *)nibNameOrNil
    if (!nibNameOrNil) {
        nibNameOrNil = NSStringFromClass([self class]);
    NSArray *viewsInNib = [[NSBundle mainBundle] loadNibNamed:nibNameOrNil
    for (id view in viewsInNib) {
        if ([view isKindOfClass:[self class]]) {
            self = view;
    return self;


Then, call like this:

MyCustomView *myCustomView = [[MyCustomView alloc] initWithNibNamed:nil];

Use a nib name if your nib is named something other than the name of your class.

To override it in your subclasses for additional behavior, it could look like this:

- (instancetype)initWithNibNamed:(NSString *)nibNameOrNil
    self = [super initWithNibNamed:nibNameOrNil];
    if (self) {
        self.layer.cornerRadius = CGRectGetHeight(self.bounds) / 2.0;
    return self;

Ignore duplicates when producing map using streams

For anyone else getting this issue but without duplicate keys in the map being streamed, make sure your keyMapper function isn't returning null values.

It's very annoying to track this down because the error will say "Duplicate key 1" when 1 is actually the value of the entry instead of the key.

In my case, my keyMapper function tried to look up values in a different map, but due to a typo in the strings was returning null values.

final Map<String, String> doop = new HashMap<>();
doop.put("a", "1");
doop.put("b", "2");

final Map<String, String> lookup = new HashMap<>();
doop.put("c", "e");
doop.put("d", "f");

doop.entrySet().stream().collect(Collectors.toMap(e -> lookup.get(e.getKey()), e -> e.getValue()));

C#: Converting byte array to string and printing out to console

This is just an updated version of Jesse Webbs code that doesn't append the unnecessary trailing , character.

public static string PrintBytes(this byte[] byteArray)
    var sb = new StringBuilder("new byte[] { ");
    for(var i = 0; i < byteArray.Length;i++)
        var b = byteArray[i];
        if (i < byteArray.Length -1)
            sb.Append(", ");
    sb.Append(" }");
    return sb.ToString();

The output from this method would be:

new byte[] { 48, ... 135, 31, 178, 7, 157 }

What's a "static method" in C#?

Core of the static keyword that you will have only one copy at RAM of this (method /variable /class ) that's shared for all calling

How can get the text of a div tag using only javascript (no jQuery)

Actually you dont need to call document.getElementById() function to get access to your div.

You can use this object directly by id:

text = test.textContent || test.innerText;

Set selected item of spinner programmatically

In my case, this code saved my day:

public static void selectSpinnerItemByValue(Spinner spnr, long value) {
    SpinnerAdapter adapter = spnr.getAdapter();
    for (int position = 0; position < adapter.getCount(); position++) {
        if(adapter.getItemId(position) == value) {

error: use of deleted function

I encountered this error when inheriting from an abstract class and not implementing all of the pure virtual methods in my subclass.

In Excel, sum all values in one column in each row where another column is a specific value

You should be able to use the IF function for that. the syntax is =IF(condition, value_if_true, value_if_false). To add an extra column with only the non-reimbursed amounts, you would use something like:

=IF(B1="No", A1, 0)

and sum that. There's probably a way to include it in a single cell below the column as well, but off the top of my head I can't think of anything simple.

How to match hyphens with Regular Expression?

The hyphen is usually a normal character in regular expressions. Only if it’s in a character class and between two other characters does it take a special meaning.


  • [-] matches a hyphen.
  • [abc-] matches a, b, c or a hyphen.
  • [-abc] matches a, b, c or a hyphen.
  • [ab-d] matches a, b, c or d (only here the hyphen denotes a character range).

c# dictionary one key many values

Use this:

Dictionary<TKey, Tuple<TValue1, TValue2, TValue3, ...>>

Dynamically add child components in React

You need to pass your components as children, like this:

var App = require('./App.js');
var SampleComponent = require('./SampleComponent.js');
        <SampleComponent name="SomeName"/> 

And then append them in the component's body:

var App = React.createClass({
    render: function() {
        return (
                <h1>App main component! </h1>

You don't need to manually manipulate HTML code, React will do that for you. If you want to add some child components, you just need to change props or state it depends. For example:

var App = React.createClass({

    getInitialState: function(){
        return [
            {id:1,name:"Some Name"}

    addChild: function() {
        // State change will cause component re-render
            {id:2,name:"Another Name"}

    render: function() {
        return (
                <h1>App main component! </h1>
                <button onClick={this.addChild}>Add component</button>
           => (
                        <SampleComponent key={} name={}/>


Optional query string parameters in ASP.NET Web API

Default values cannot be supplied for parameters that are not declared 'optional'

 Function GetFindBooks(id As Integer, ByVal pid As Integer, Optional sort As String = "DESC", Optional limit As Integer = 99)

In your WebApiConfig

 config.Routes.MapHttpRoute( _
          name:="books", _
          routeTemplate:="api/{controller}/{action}/{id}/{pid}/{sort}/{limit}", _
          defaults:=New With {.id = RouteParameter.Optional, .pid = RouteParameter.Optional, .sort = UrlParameter.Optional, .limit = UrlParameter.Optional} _