Programs & Examples On #Ob start

ob_start is a PHP function which turns output buffering on. While output buffering is active no output is sent from the script (other than headers), instead the output is stored in an internal buffer.

Accessing JSON elements

import json
weather = urllib2.urlopen('url')
wjson =
wjdata = json.loads(wjson)
print wjdata['data']['current_condition'][0]['temp_C']

What you get from the url is a json string. And your can't parse it with index directly. You should convert it to a dict by json.loads and then you can parse it with index.

Instead of using .read() to intermediately save it to memory and then read it to json, allow json to load it directly from the file:

wjdata = json.load(urllib2.urlopen('url'))

How can I show an image using the ImageView component in javafx and fxml?

You don't need an initializer, unless you're dynamically loading a different image each time. I think doing as much as possible in fxml is more organized. Here is an fxml file that will do what you need.

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import javafx.scene.image.*?>
<?import javafx.scene.layout.*?>


Specifying the backgroundLoading property in the Image tag is optional, it defaults to false. It's best to set backgroundLoading true when it takes a moment or longer to load the image, that way a placeholder will be used until the image loads, and the program wont freeze while loading.

"The operation is not valid for the state of the transaction" error and transaction scope

I've encountered this error when my Transaction is nested within another. Is it possible that the stored procedure declares its own transaction or that the calling function declares one?

What is dtype('O'), in pandas?

'O' stands for object.

#Loading a csv file as a dataframe
import pandas as pd 
train_df = pd.read_csv('train.csv')
col_name = 'Name of Employee'

#Checking the datatype of column name

#Instead try printing the same thing
print train_df[col_name].dtype

The first line returns: dtype('O')

The line with the print statement returns the following: object

Why extend the Android Application class?

I think you can use the Application class for many things, but they are all tied to your need to do some stuff BEFORE any of your Activities or Services are started. For instance, in my application I use custom fonts. Instead of calling


from every Activity to get references for my fonts from the Assets folder (this is bad because it will result in memory leak as you are keeping a reference to assets every time you call that method), I do this from the onCreate() method in my Application class:

private App appInstance;
Typeface quickSandRegular;
public void onCreate() {

    appInstance = this;
    quicksandRegular = Typeface.createFromAsset(getApplicationContext().getAssets(),

Now, I also have a method defined like this:

public static App getAppInstance() {
    return appInstance;

and this:

public Typeface getQuickSandRegular() {
    return quicksandRegular;

So, from anywhere in my application, all I have to do is:


Another use for the Application class for me is to check if the device is connected to the Internet BEFORE activities and services that require a connection actually start and take necessary action.

Read and write to binary files in C?

There are a few ways to do it. If I want to read and write binary I usually use open(), read(), write(), close(). Which are completely different than doing a byte at a time. You work with integer file descriptors instead of FILE * variables. fileno will get an integer descriptor from a FILE * BTW. You read a buffer full of data, say 32k bytes at once. The buffer is really an array which you can read from really fast because it's in memory. And reading and writing many bytes at once is faster than one at a time. It's called a blockread in Pascal I think, but read() is the C equivalent.

I looked but I don't have any examples handy. OK, these aren't ideal because they also are doing stuff with JPEG images. Here's a read, you probably only care about the part from open() to close(). fbuf is the array to read into, sb.st_size is the file size in bytes from a stat() call.

    fd = open(MASKFNAME,O_RDONLY);
    if (fd != -1) {
      splitmask(fbuf,(uint32_t)sb.st_size); // look at lines, etc
      have_mask = 1;

Here's a write: (here pix is the byte array, jwidth and jheight are the JPEG width and height so for RGB color we write height * width * 3 color bytes). It's the # of bytes to write.

void simpdump(uint8_t *pix, char *nm) { // makes a raw aka .data file
  int sdfd;
  sdfd = open(nm,O_WRONLY | O_CREAT);
  if (sdfd == -1) {
    printf("bad open\n");
  printf("width: %i height: %i\n",jwidth,jheight);  // to the console

Look at man 2 open, also read, write, close. Also this old-style jpeg example.c: I'm reading and writing an entire image at once here. But they're binary reads and writes of bytes, just a lot at once.

"But when I try to read from a file it is not outputting correctly." Hmmm. If you read a number 65 that's (decimal) ASCII for an A. Maybe you should look at man ascii too. If you want a 1 that's ASCII 0x31. A char variable is a tiny 8-bit integer really, if you do a printf as a %i you get the ASCII value, if you do a %c you get the character. Do %x for hexadecimal. All from the same number between 0 and 255.

how to sort an ArrayList in ascending order using Collections and Comparator

Use the default version:


Of course this requires that your Elements implement Comparable, but the same holds true for the version you mentioned.

BTW: you should use generics in your code, that way you get compile-time errors if your class doesn't implement Comparable. And compile-time errors are much better than the runtime errors you'll get otherwise.

List<MyClass> list = new ArrayList<MyClass>();
// now fill up the list

// compile error here unless MyClass implements Comparable

Forward declaring an enum in C++

Because the enum can be an integral size of varying size (the compiler decides which size a given enum has), the pointer to the enum can also have varying size, since it's an integral type (chars have pointers of a different size on some platforms for instance).

So the compiler can't even let you forward-declare the enum and user a pointer to it, because even there, it needs the size of the enum.

How to change background color in the Notepad++ text editor?

There seems to have been an update some time in the past 3 years which changes the location of where to place themes in order to get them working.

Previosuly, themes were located in the Notepad++ installation folder. Now they are located in AppData:


My answer is an update to @Amit-IO's answer about manually copying the themes.

  1. In Explorer, browse to: %AppData%\Notepad++.
  2. If a folder called themes does not exist, create it.
  3. Download your favourite theme from wherever (see Amit-IO's answer for a good list) and save it to %AppData%\Notepad++\themes.
  4. Restart Notepad++ and then use Settings -> Style Configurator. The new theme(s) will appear in the list.

Span inside anchor or anchor inside span or doesn't matter?

SPAN is a GENERIC inline container. It does not matter whether an a is inside span or span is inside a as both are inline elements. Feel free to do whatever seems logically correct to you.

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

jQuery .on method is used to bind events even without the presence of element on page load. Here is the link It is used in this way:

 $("#dataTable tbody tr").on("click", function(event){

Before jquery 1.7, .live() method was used, but it is deprecated now.

How to view changes made to files on a certain revision in Subversion

The equivalent command in svn is:

svn log --diff -r revision

Looping through rows in a DataView

You can iterate DefaultView as the following code by Indexer:

DataTable dt = new DataTable();
// add some rows to your table
// ...
dt.DefaultView.Sort = "OneColumnName ASC"; // For example
for (int i = 0; i < dt.Rows.Count; i++)
    DataRow oRow = dt.DefaultView[i].Row;
    // Do your stuff with oRow
    // ...

How to run a .jar in mac?

Make Executable your jar and after that double click on it on Mac OS then it works successfully.

sudo chmod +x filename.jar

Try this, I hope this works.

Ansible: get current target host's IP address

Simple debug command:

ansible -i inventory/hosts.yaml -m debug -a "var=hostvars[inventory_hostname]" all


"hostvars[inventory_hostname]": {
    "ansible_check_mode": false, 
    "ansible_diff_mode": false, 
    "ansible_facts": {}, 
    "ansible_forks": 5, 
    "ansible_host": "", 
    "ansible_inventory_sources": [
    "ansible_playbook_python": "/usr/bin/python2", 
    "ansible_port": 65532, 
    "ansible_verbosity": 0, 
    "ansible_version": {
        "full": "2.8.5", 
        "major": 2, 
        "minor": 8, 
        "revision": 5, 
        "string": "2.8.5"

get host ip address:

ansible -i inventory/hosts.yaml -m debug -a "var=hostvars[inventory_hostname].ansible_host" all

zk01 | SUCCESS => {
    "hostvars[inventory_hostname].ansible_host": ""

Set Page Title using PHP

What about using something like:

    $page_title = "Your page tile";
    include("navigation.php");             // if required

How can I select the row with the highest ID in MySQL?

if it's just the highest ID you want. and ID is unique/auto_increment:


Error during SSL Handshake with remote server

I have 2 servers setup on docker, reverse proxy & web server. This error started happening for all my websites all of a sudden after 1 year. When setting up earlier, I generated a self signed certificate on the web server.

So, I had to generate the SSL certificate again and it started working...

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout ssl.key -out ssl.crt

How to force a UIViewController to Portrait orientation in iOS 6

I have a relatively complex universal app using UISplitViewController and UISegmentedController, and have a few views that must be presented in Landscape using presentViewController. Using the methods suggested above, I was able to get iPhone ios 5 & 6 to work acceptably, but for some reason the iPad simply refused to present as Landscape. Finally, I found a simple solution (implemented after hours of reading and trial and error) that works for both devices and ios 5 & 6.

Step 1) On the controller, specify the required orientation (more or less as noted above)

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
    return (interfaceOrientation == UIInterfaceOrientationLandscapeRight);

    return YES;

    NSInteger mask = UIInterfaceOrientationMaskLandscape;
    return mask;


Step 2) Create a simple UINavigationController subclass and implement the following methods

-(BOOL)shouldAutorotate {
        return YES;
- (NSUInteger)supportedInterfaceOrientations {
        return UIInterfaceOrientationMaskLandscape;

Step 3) Present your viewController

vc = [[MyViewController alloc]init];
MyLandscapeNavigationController *myNavigationController = [[MyLandscapeNavigationController alloc] initWithRootViewController:vc];
[self myNavigationController animated:YES completion:nil];

Hope this is helpful to someone.

Make $JAVA_HOME easily changable in Ubuntu

Take a look at bash(1), you need a login shell to pickup the ~/.profile, i.e. the -l option.

addEventListener for keydown on Canvas

Set the tabindex of the canvas element to 1 or something like this

<canvas tabindex='1'></canvas>

It's an old trick to make any element focusable

How to autowire RestTemplate using annotations

private RestOperations restTemplate;

You can only autowire interfaces with implementations.

Display images in mvc

Make sure you image is a relative path such as:



<img src="~/Content/images/myimage.png" />

You could convert the byte[] into a Base64 string on the fly.

string base64String = Convert.ToBase64String(imageBytes);

<img src="@String.Format("data:image/png;base64,{0}", base64string)" />

What is "with (nolock)" in SQL Server?

Another case where it's usually okay is in a reporting database, where data is perhaps already aged and writes just don't happen. In this case, though, the option should be set at the database or table level by the administrator by changing the default isolation level.

In the general case: you can use it when you are very sure that it's okay to read old data. The important thing to remember is that its very easy to get that wrong. For example, even if it's okay at the time you write the query, are you sure something won't change in the database in the future to make these updates more important?

I'll also 2nd the notion that it's probably not a good idea in banking app. Or inventory app. Or anywhere you're thinking about transactions.

html5 localStorage error with Safari: "QUOTA_EXCEEDED_ERR: DOM Exception 22: An attempt was made to add something to storage that exceeded the quota."

I have created a patch for the issue. Simply I am checking if the browser does support localStorage or sessionStorage or not. If not then the storage engine will be Cookie. But the negative side is Cookie have very tiny storage memory :(

function StorageEngine(engine) {
    this.engine = engine || 'localStorage';

    if(!this.checkStorageApi(this.engine)) {
        // Default engine would be alway cooke
        // Safari private browsing issue with localStorage / sessionStorage
        this.engine = 'cookie';

StorageEngine.prototype.checkStorageApi = function(name) {
    if(!window[name]) return false;
    try {
        var tempKey = '__temp_';
        window[name].setItem(tempKey, 'hi')
        return true;
    } catch(e) {
        return false;

StorageEngine.prototype.getItem = function(key) {
    if(['sessionStorage', 'localStorage'].includes(this.engine)) {
        return window[this.engine].getItem(key);
    } else if('cookie') {
        var name = key+"=";
        var allCookie = decodeURIComponent(document.cookie).split(';');
        var cval = [];
        for(var i=0; i < allCookie.length; i++) {
            if (allCookie[i].trim().indexOf(name) == 0) {
                cval = allCookie[i].trim().split("=");
        return (cval.length > 0) ? cval[1] : null;
    return null;

StorageEngine.prototype.setItem = function(key, val, exdays) {
    if(['sessionStorage', 'localStorage'].includes(this.engine)) {
        window[this.engine].setItem(key, val);
    } else if('cookie') {
        var d = new Date();
        var exdays = exdays || 1;
        d.setTime(d.getTime() + (exdays*24*36E5));
        var expires = "expires="+ d.toUTCString();
        document.cookie = key + "=" + val + ";" + expires + ";path=/";
    return true;

// ------------------------
var StorageEngine = new StorageEngine(); // new StorageEngine('localStorage');
// If your current browser (IOS safary or any) does not support localStorage/sessionStorage, then the default engine will be "cookie"

StorageEngine.setItem('keyName', 'val')

var expireDay = 1; // for cookie only
StorageEngine.setItem('keyName', 'val', expireDay)

How to load a controller from another controller in codeigniter?

While the methods above might work, here is a very good method.

Extend the core controller with a MY controller, then extend this MY controller for all your other controllers. For example, you could have:

class MY_Controller extends CI_Controller {
    public function is_logged()
        //Your code here
public function logout()
        //Your code here

Then your other controllers could then extend this as follows:

class Another_Controller extends MY_Controller {
    public function show_home()
         if (!$this->is_logged()) {
           return false;
public function logout()

How do I update an entity using spring-data-jpa?

You can simply use this function with save() JPAfunction, but the object sent as parameter must contain an existing id in the database otherwise it will not work, because save() when we send an object without id, it adds directly a row in database, but if we send an object with an existing id, it changes the columns already found in the database.

public void updateUser(Userinfos u) {
    User userFromDb = userRepository.findById(u.getid());
    // crush the variables of the object found

How does Go update third-party packages?

go 1.13

(exec from module root directory)

Update specified dependencies:

go get -u <package-name>

Update all direct and indirect dependencies to latest minor or patch upgrades (pre-releases are ignored):

go get -u ./...
# or
go get -u=patch ./...


go help get

Twig for loop for arrays with keys

These are extended operations (e.g., sort, reverse) for one dimensional and two dimensional arrays in Twig framework:

1D Array

Without Key Sort and Reverse

{% for key, value in array_one_dimension %}
    <div>{{ key }}</div>
    <div>{{ value }}</div>
{% endfor %}

Key Sort

{% for key, value in array_one_dimension|keys|sort %}
    <div>{{ key }}</div>
    <div>{{ value }}</div>
{% endfor %}

Key Sort and Reverse

{% for key, value in array_one_dimension|keys|sort|reverse %}
    <div>{{ key }}</div>
    <div>{{ value }}</div>
{% endfor %}

2D Arrays

Without Key Sort and Reverse

{% for key_a, value_a in array_two_dimension %}
    {% for key_b, value_b in array_two_dimension[key_a] %}
        <div>{{ key_b }}</div>
        <div>{{ value_b }}</div>
    {% endfor %}
{% endfor %}

Key Sort on Outer Array

{% for key_a, value_a in array_two_dimension|keys|sort %}
    {% for key_b, value_b in array_two_dimension[key_a] %}
        <div>{{ key_b }}</div>
        <div>{{ value_b }}</div>
    {% endfor %}
{% endfor %}

Key Sort on Both Outer and Inner Arrays

{% for key_a, value_a in array_two_dimension|keys|sort %}
    {% for key_b, value_b in array_two_dimension[key_a]|keys|sort %}
        <div>{{ key_b }}</div>
        <div>{{ value_b }}</div>
    {% endfor %}
{% endfor %}

Key Sort on Outer Array & Key Sort and Reverse on Inner Array

{% for key_a, value_a in array_two_dimension|keys|sort %}
    {% for key_b, value_b in array_two_dimension[key_a]|keys|sort|reverse %}
        <div>{{ key_b }}</div>
        <div>{{ value_b }}</div>
    {% endfor %}
{% endfor %}

Key Sort and Reverse on Outer Array & Key Sort on Inner Array

{% for key_a, value_a in array_two_dimension|keys|sort|reverse %}
    {% for key_b, value_b in array_two_dimension[key_a]|keys|sort %}
        <div>{{ key_b }}</div>
        <div>{{ value_b }}</div>
    {% endfor %}
{% endfor %}

Key Sort and Reverse on Both Outer and Inner Array

{% for key_a, value_a in array_two_dimension|keys|sort|reverse %}
    {% for key_b, value_b in array_two_dimension[key_a]|keys|sort|reverse %}
        <div>{{ key_b }}</div>
        <div>{{ value_b }}</div>
    {% endfor %}
{% endfor %}

Pass data from Activity to Service using an Intent

For a precise answer to this question on "How to send data via intent from an Activity to Service", Is that you have to override the onStartCommand() method which is where you receive the intent object:

When you create a Service you should override the onStartCommand() method so if you closely look at the signature below, this is where you receive the intent object which is passed to it:

  public int onStartCommand(Intent intent, int flags, int startId)

So from an activity you will create the intent object to start service and then you place your data inside the intent object for example you want to pass a UserID from Activity to Service:

 Intent serviceIntent = new Intent(YourService.class.getName())
 serviceIntent.putExtra("UserID", "123456");

When the service is started its onStartCommand() method will be called so in this method you can retrieve the value (UserID) from the intent object for example

public int onStartCommand (Intent intent, int flags, int startId) {
    String userID = intent.getStringExtra("UserID");
    return START_STICKY;

Note: the above answer specifies to get an Intent with getIntent() method which is not correct in context of a service

how to cancel/abort ajax request in axios

import React, { Component } from "react";
import axios from "axios";

const CancelToken = axios.CancelToken;

let cancel;

class Abc extends Component {
  componentDidMount() {

  Api() {
      // Cancel previous request
    if (cancel !== undefined) {
    }, reqBody, {
        cancelToken: new CancelToken(function executor(c) {
          cancel = c;
      .then((response) => {
        //responce Body
      .catch((error) => {
        if (axios.isCancel(error)) {
          console.log("post Request canceled");

  render() {
    return <h2>cancel Axios Request</h2>;

export default Abc;

How do I check if an HTML element is empty using jQuery?

Try this:

if (!$('#el').html()) {

Delete commits from a branch in Git

Say we want to remove commits 2 & 4 from the repo.

commit 0 : b3d92c5
commit 1 : 2c6a45b
commit 2 : <any_hash>
commit 3 : 77b9b82
commit 4 : <any_hash>

Note: You need to have admin rights over the repo since you are using --hard and -f.

  • git checkout b3d92c5 Checkout the last usable commit.
  • git checkout -b repair Create a new branch to work on.
  • git cherry-pick 77b9b82 Run through commit 3.
  • git cherry-pick 2c6a45b Run through commit 1.
  • git checkout master Checkout master.
  • git reset --hard b3d92c5 Reset master to last usable commit.
  • git merge repair Merge our new branch onto master.
  • git push -f origin master Push master to the remote repo.

How to prompt for user input and read command-line arguments

This simple program helps you in understanding how to feed the user input from command line and to show help on passing invalid argument.

import argparse
import sys

     parser = argparse.ArgumentParser()
     parser.add_argument("square", help="display a square of a given number",
    args = parser.parse_args()

    #print the square of user input from cmd line.
    print args.square**2

    #print all the sys argument passed from cmd line including the program name.
    print sys.argv

    #print the second argument passed from cmd line; Note it starts from ZERO
    print sys.argv[1]
    e = sys.exc_info()[0]
    print e

1) To find the square root of 5

C:\Users\Desktop>python -i 5
['', '5']

2) Passing invalid argument other than number

C:\Users\bgh37516\Desktop>python -i five
usage: [-h] square error: argument square: invalid int value: 'five'
<type 'exceptions.SystemExit'>

How to change the background color on a input checkbox with css?

I always use pseudo elements :before and :after for changing the appearance of checkboxes and radio buttons. it's works like a charm.

Refer this link for more info



  1. Hide the default checkbox using css rules like visibility:hidden or opacity:0 or position:absolute;left:-9999px etc.
  2. Create a fake checkbox using :before element and pass either an empty or a non-breaking space '\00a0';
  3. When the checkbox is in :checked state, pass the unicode content: "\2713", which is a checkmark;
  4. Add :focus style to make the checkbox accessible.
  5. Done

Here is how I did it.

.box {_x000D_
  background: #666666;_x000D_
  color: #ffffff;_x000D_
  width: 250px;_x000D_
  padding: 10px;_x000D_
  margin: 1em auto;_x000D_
p {_x000D_
  margin: 1.5em 0;_x000D_
  padding: 0;_x000D_
input[type="checkbox"] {_x000D_
  visibility: hidden;_x000D_
label {_x000D_
  cursor: pointer;_x000D_
input[type="checkbox"] + label:before {_x000D_
  border: 1px solid #333;_x000D_
  content: "\00a0";_x000D_
  display: inline-block;_x000D_
  font: 16px/1em sans-serif;_x000D_
  height: 16px;_x000D_
  margin: 0 .25em 0 0;_x000D_
  padding: 0;_x000D_
  vertical-align: top;_x000D_
  width: 16px;_x000D_
input[type="checkbox"]:checked + label:before {_x000D_
  background: #fff;_x000D_
  color: #333;_x000D_
  content: "\2713";_x000D_
  text-align: center;_x000D_
input[type="checkbox"]:checked + label:after {_x000D_
  font-weight: bold;_x000D_
input[type="checkbox"]:focus + label::before {_x000D_
    outline: rgb(59, 153, 252) auto 5px;_x000D_
<div class="content">_x000D_
  <div class="box">_x000D_
      <input type="checkbox" id="c1" name="cb">_x000D_
      <label for="c1">Option 01</label>_x000D_
      <input type="checkbox" id="c2" name="cb">_x000D_
      <label for="c2">Option 02</label>_x000D_
      <input type="checkbox" id="c3" name="cb">_x000D_
      <label for="c3">Option 03</label>_x000D_

Much more stylish using :before and :after

  font-family: sans-serif;  _x000D_
.container {_x000D_
    margin-top: 50px;_x000D_
    margin-left: 20px;_x000D_
    margin-right: 20px;_x000D_
.checkbox {_x000D_
    width: 100%;_x000D_
    margin: 15px auto;_x000D_
    position: relative;_x000D_
    display: block;_x000D_
.checkbox input[type="checkbox"] {_x000D_
    width: auto;_x000D_
    opacity: 0.00000001;_x000D_
    position: absolute;_x000D_
    left: 0;_x000D_
    margin-left: -20px;_x000D_
.checkbox label {_x000D_
    position: relative;_x000D_
.checkbox label:before {_x000D_
    content: '';_x000D_
    position: absolute;_x000D_
    left: 0;_x000D_
    top: 0;_x000D_
    margin: 4px;_x000D_
    width: 22px;_x000D_
    height: 22px;_x000D_
    transition: transform 0.28s ease;_x000D_
    border-radius: 3px;_x000D_
    border: 2px solid #7bbe72;_x000D_
.checkbox label:after {_x000D_
  content: '';_x000D_
    display: block;_x000D_
    width: 10px;_x000D_
    height: 5px;_x000D_
    border-bottom: 2px solid #7bbe72;_x000D_
    border-left: 2px solid #7bbe72;_x000D_
    -webkit-transform: rotate(-45deg) scale(0);_x000D_
    transform: rotate(-45deg) scale(0);_x000D_
    transition: transform ease 0.25s;_x000D_
    will-change: transform;_x000D_
    position: absolute;_x000D_
    top: 12px;_x000D_
    left: 10px;_x000D_
.checkbox input[type="checkbox"]:checked ~ label::before {_x000D_
    color: #7bbe72;_x000D_
.checkbox input[type="checkbox"]:checked ~ label::after {_x000D_
    -webkit-transform: rotate(-45deg) scale(1);_x000D_
    transform: rotate(-45deg) scale(1);_x000D_
.checkbox label {_x000D_
    min-height: 34px;_x000D_
    display: block;_x000D_
    padding-left: 40px;_x000D_
    margin-bottom: 0;_x000D_
    font-weight: normal;_x000D_
    cursor: pointer;_x000D_
    vertical-align: sub;_x000D_
.checkbox label span {_x000D_
    position: absolute;_x000D_
    top: 50%;_x000D_
    -webkit-transform: translateY(-50%);_x000D_
    transform: translateY(-50%);_x000D_
.checkbox input[type="checkbox"]:focus + label::before {_x000D_
    outline: 0;_x000D_
<div class="container"> _x000D_
  <div class="checkbox">_x000D_
     <input type="checkbox" id="checkbox" name="" value="">_x000D_
     <label for="checkbox"><span>Checkbox</span></label>_x000D_
  <div class="checkbox">_x000D_
     <input type="checkbox" id="checkbox2" name="" value="">_x000D_
     <label for="checkbox2"><span>Checkbox</span></label>_x000D_

How to delete an SVN project from SVN repository

In the case where you simply want to delete a project from the head revision, so that it no longer shows up in your repo when you run svn list file:///path/to/repo/ just run:

svn delete file:///path/to/repo/project 

However, if you need to delete all record of it in the repo, use another method.

What is the closest thing Windows has to fork()?

Prior to Microsoft introducing their new "Linux subsystem for Windows" option, CreateProcess() was the closest thing Windows has to fork(), but Windows requires you to specify an executable to run in that process.

The UNIX process creation is quite different to Windows. Its fork() call basically duplicates the current process almost in total, each in their own address space, and continues running them separately. While the processes themselves are different, they are still running the same program. See here for a good overview of the fork/exec model.

Going back the other way, the equivalent of the Windows CreateProcess() is the fork()/exec() pair of functions in UNIX.

If you were porting software to Windows and you don't mind a translation layer, Cygwin provided the capability that you want but it was rather kludgey.

Of course, with the new Linux subsystem, the closest thing Windows has to fork() is actually fork() :-)

Print string to text file

If you are using Python3.

then you can use Print Function :

your_data = {"Purchase Amount": 'TotalAmount'}
print(your_data,  file=open('D:\log.txt', 'w'))

For python2

this is the example of Python Print String To Text File

def my_func():
    this function return some value
    return 25.256

def write_file(data):
    this function write data to file
    :param data:
    file_name = r'D:\log.txt'
    with open(file_name, 'w') as x_file:
        x_file.write('{} TotalAmount'.format(data))

def run():
    data = my_func()


Wait until an HTML5 video loads

you can use preload="none" in the attribute of video tag so the video will be displayed only when user clicks on play button.

<video preload="none">

How can I format date by locale in Java?

Yes, using DateFormat.getDateInstance(int style, Locale aLocale) This displays the current date in a locale-specific way.

So, for example:

DateFormat df = DateFormat.getDateInstance(DateFormat.SHORT, yourLocale);
String formattedDate = df.format(yourDate);

See the docs for the exact meaning of the style parameter (SHORT, MEDIUM, etc)

Error:Unable to locate adb within SDK in Android Studio

even after downloading specific required file or everything, we could face file execution error.

a file execution fail could be due to following reasons:
1. user permission/s (inheritance manhandled).
2. corrupt file.
3. file being accessed by another application at the same time.
4. file being locked by anti-malware / anti-virus software.

strangely my antivirus detected adb, avd and jndispatch.dll files as unclean files and dumped them to its vault.

i had to restore them from AVG vault. configure AVG to ignore (add folder to exception list) folder of AndroidStudio and other required folder.

if you are without antivirus and still facing this problem, remember that windows 7 and above have inbuilt 'windows defender'. see whether this fellow is doing the same thing. put your folder in antivirus 'exclusion' list as the vendor is trusted world wide.

this same answer would go to 'Error in launching AVD with AMD processor'. i don't have enough reputation to answer this question there and there.

XSLT counting elements with a given value

<xsl:variable name="count" select="count(/Property/long = $parPropId)"/>

Un-tested but I think that should work. I'm assuming the Property nodes are direct children of the root node and therefor taking out your descendant selector for peformance

How can I rebuild indexes and update stats in MySQL innoDB?

For basic cleanup and re-analyzing you can run "OPTIMIZE TABLE ...", it will compact out the overhead in the indexes and run ANALYZE TABLE too, but it's not going to re-sort them and make them as small & efficient as they could be.

However, if you want the indexes completely rebuilt for best performance, you can:

  1. drop / re-add indexes (obviously)
  2. dump / reload the table
  3. ALTER TABLE and "change" using the same storage engine
  4. REPAIR TABLE (only works for MyISAM, ARCHIVE, and CSV)

If you do an ALTER TABLE on a field (that is part of an index) and change its type, then it will also fully rebuild the related index(es).

Understanding the Gemfile.lock file

It looks to me like PATH lists the first-generation dependencies directly from your gemspec, whereas GEM lists second-generation dependencies (i.e. what your dependencies depend on) and those from your Gemfile. PATH::remote is . because it relied on a local gemspec in the current directory to find out what belongs in PATH::spec, whereas GEM::remote is, since that's where it had to go to find out what belongs in GEM::spec.

In a Rails plugin, you'll see a PATH section, but not in a Rails app. Since the app doesn't have a gemspec file, there would be nothing to put in PATH.

As for DEPENDENCIES, states:

Runtime dependencies in your gemspec are treated like base dependencies, 
and development dependencies are added by default to the group, :development

The Gemfile generated by rails plugin new my_plugin says something similar:

# Bundler will treat runtime dependencies like base dependencies, and
# development dependencies will be added by default to the :development group.

What this means is that the difference between

s.add_development_dependency "july" # (1)


s.add_dependency "july" # (2)

is that (1) will only include "july" in Gemfile.lock (and therefore in the application) in a development environment. So when you run bundle install, you'll see "july" not only under PATH but also under DEPENDENCIES, but only in development. In production, it won't be there at all. However, when you use (2), you'll see "july" only in PATH, not in DEPENDENCIES, but it will show up when you bundle install from a production environment (i.e. in some other gem that includes yours as a dependency), not only development.

These are just my observations and I can't fully explain why any of this is the way it is but I welcome further comments.

Converting a float to a string without rounding it

Some form of rounding is often unavoidable when dealing with floating point numbers. This is because numbers that you can express exactly in base 10 cannot always be expressed exactly in base 2 (which your computer uses).

For example:

>>> .1

In this case, you're seeing .1 converted to a string using repr:

>>> repr(.1)

I believe python chops off the last few digits when you use str() in order to work around this problem, but it's a partial workaround that doesn't substitute for understanding what's going on.

>>> str(.1)

I'm not sure exactly what problems "rounding" is causing you. Perhaps you would do better with string formatting as a way to more precisely control your output?


>>> '%.5f' % .1
>>> '%.5f' % .12345678

Documentation here.

Open Source HTML to PDF Renderer with Full CSS Support

I've always used it on the command line and not as a library, but HTMLDOC gives me excellent results, and it handles at least some CSS (I couldn't easily see how much).

Here's a sample command line

htmldoc --webpage -t pdf --size letter --fontsize 10pt index.html > index.pdf

How to append binary data to a buffer in node.js

Updated Answer for Node.js ~>0.8

Node is able to concatenate buffers on its own now.

var newBuffer = Buffer.concat([buffer1, buffer2]);

Old Answer for Node.js ~0.6

I use a module to add a .concat function, among others:

I know it isn't a "pure" solution, but it works very well for my purposes.

Regular expression to search multiple strings (Textpad)

If I understand what you are asking, it is a regular expression like this:


This matches the three sets of digit strings at beginning of line only.

Linux delete file with size 0

You can use the command find to do this. We can match files with -type f, and match empty files using -size 0. Then we can delete the matches with -delete.

find . -type f -size 0 -delete

How to find which version of Oracle is installed on a Linux server (In terminal)

I solved this in about 1 minute by just reading the startup script (in my case /etc/init.d/oracle-xe):

less /etc/init.d/oracle-xe

At almost the beginning of the file I found:


This was the quickest solution for me because I knew where the script was located, and that it is used for starting/restarting the server.

Of course, this relies on that the version number actually corresponds to the actual server version, which it should for a correctly installed instance.

How do I flush the cin buffer?

I prefer:


There's an example where cin.ignore just doesn't cut it, but I can't think of it at the moment. It was a while ago when I needed to use it (with Mingw).

However, fflush(stdin) is undefined behavior according to the standard. fflush() is only meant for output streams. fflush(stdin) only seems to work as expected on Windows (with GCC and MS compilers at least) as an extension to the C standard.

So, if you use it, your code isn't going to be portable.

See Using fflush(stdin).

Also, see for an alternative.

Foreach value from POST from form

If your post keys have to be parsed and the keys are sequences with data, you can try this:

Post data example: Storeitem|14=data14

foreach($_POST as $key => $value){
    $key=Filterdata($key); $value=Filterdata($value);

then you can use strpos to isolate the end of the key separating the number from the key.

iOS download and save image inside app

Since we are on IO5 now, you no longer need to write images to disk neccessarily.
You are now able to set "allow external storage" on an coredata binary attribute. According to apples release notes it means the following:

Small data values like image thumbnails may be efficiently stored in a database, but large photos or other media are best handled directly by the file system. You can now specify that the value of a managed object attribute may be stored as an external record - see setAllowsExternalBinaryDataStorage: When enabled, Core Data heuristically decides on a per-value basis if it should save the data directly in the database or store a URI to a separate file which it manages for you. You cannot query based on the contents of a binary data property if you use this option.

curl: (6) Could not resolve host:; Name or service not known

Perhaps you have some very weird and restrictive SELinux rules in place?

If not, try strace -o /tmp/wtf -fF curl -v and try to spot from /tmp/wtf output file what's going on.

Align button at the bottom of div using CSS

Goes to the right and can be used the same way for the left

   float: right;
   bottom: 0;

ASP.NET 5 MVC: unable to connect to web server 'IIS Express'

In my case this error was caused because I was running Docker.

Make sure the port you are trying to host on is not in a Port Exclusion Range by running the following command in cmd/powershell session:

netsh interface ipv4 show excludedportrange protocol=tcp

I tracked this down after reading through this stackoverflow question:

Unable to launch the IIS Express Web server, Failed to register URL, Access is denied


Counting the Number of keywords in a dictionary in python

If the question is about counting the number of keywords then would recommend something like

def countoccurrences(store, value):
        store[value] = store[value] + 1
    except KeyError as e:
        store[value] = 1

in the main function have something that loops through the data and pass the values to countoccurrences function

if __name__ == "__main__":
    store = {}
    list = ('a', 'a', 'b', 'c', 'c')
    for data in list:
        countoccurrences(store, data)
    for k, v in store.iteritems():
        print "Key " + k + " has occurred "  + str(v) + " times"

The code outputs

Key a has occurred 2 times
Key c has occurred 2 times
Key b has occurred 1 times

How do I give ASP.NET permission to write to a folder in Windows 7?

My immediate solution (since I couldn't find the ASP.NET worker process) was to give write (that is, Modify) permission to IIS_IUSRS. This worked. I seem to recall that in WinXP I had to specifically given the ASP.NET worker process write permission to accomplish this. Maybe my memory is faulty, but anyway...

@DraganRadivojevic wrote that he thought this was dangerous from a security viewpoint. I do not disagree, but since this was my workstation and not a network server, it seemed relatively safe. In any case, his answer is better and is what I finally settled on after chasing down a fail-path due to not specifying the correct domain for the AppPool user.

Calculating Covariance with Python and Numpy

Thanks to unutbu for the explanation. By default numpy.cov calculates the sample covariance. To obtain the population covariance you can specify normalisation by the total N samples like this:

Covariance = numpy.cov(a, b, bias=True)[0][1]

or like this:

Covariance = numpy.cov(a, b, ddof=0)[0][1]

How to save password when using Subversion from the console

If you use svn+ssh, you can copy your public ssh key to the remote machine:

ssh-copy-id user@remotehost

How to compare two maps by their values

If you assume that there can be duplicate values the only way to do this is to put the values in lists, sort them and compare the lists viz:

List<String> values1 = new ArrayList<String>(map1.values());
List<String> values2 = new ArrayList<String>(map2.values());
boolean mapsHaveEqualValues = values1.equals(values2);

If values cannot contain duplicate values then you can either do the above without the sort using sets.


Use the following Statement:

  UPDATE prueba
  SET nombre = '1', apellido = '1' 
  WHERE cedula = 'ct'
  INSERT INTO prueba (cedula, nombre, apellido)
  VALUES ('ct', 'ct', 'ct');

Giving graphs a subtitle in matplotlib

This is a pandas code example that implements Floris van Vugt's answer (Dec 20, 2010). He said:

>What I do is use the title() function for the subtitle and the suptitle() for the >main title (they can take different fontsize arguments). Hope that helps!

import pandas as pd
import matplotlib.pyplot as plt

d = {'series a' : pd.Series([1., 2., 3.], index=['a', 'b', 'c']),
      'series b' : pd.Series([1., 2., 3., 4.], index=['a', 'b', 'c', 'd'])}
df = pd.DataFrame(d)

title_string = "This is the title"
subtitle_string = "This is the subtitle"

plt.suptitle(title_string, y=1.05, fontsize=18)
plt.title(subtitle_string, fontsize=10)

Note: I could not comment on that answer because I'm new to stackoverflow.

Execute a shell script in current shell with sudo permission

I think you are confused about the difference between sourcing and executing a script.

Executing a script means creating a new process, and running the program. The program can be a shell script, or any other type of program. As it is a sub process, any environmental variables changed in the program will not affect the shell.

Sourcing a script can only be used with a bash script (if you are running bash). It effectively types the commands in as if you did them. This is useful as it lets a script change environmental variables in the shell.

Running a script is simple, you just type in the path to the script. . is the current directory. So ./ will execute the file in the current directory. If the command is a single file (eg, it will check all the folders in the PATH variable to find the script. Note that the current directory isn't in PATH, so you can't execute a file in the current directory by running, you need to run ./ (unless the current directory is in the PATH, eg you can run ls while in the /bin dir).

Sourcing a script doesn't use the PATH, and just searches for the path. Note that source isn't a program - otherwise it wouldn't be able to change environmental variables in the current shell. It is actually a bash built in command. Search /bin and /usr/bin - you won't find a source program there. So to source a file in the current directory, you just use source

How does sudo interact with this? Well sudo takes a program, and executes it as root. Eg sudo ./ executes in a sub process but running as root.

What does sudo source ./ do however? Remember source isn't a program (rather a shell builtin)? Sudo expects a program name though, so it searches for a program named source. It doesn't find one, and so fails. It isn't possible to source a file running as root, without creating a new subprocess, as you cannot change the runner of a program (in this case, bash) after it has started.

I'm not sure what you actually wanted, but hopefully this will clear it up for you.

Here is a concrete example. Make the file in your current directory with the contents:

export NEW_VAR="hello"
echo "Some text"

Make it executable with chmod +x

Now observe what happens with bash:

> ./
Some text
> echo $NEW_VAR

> sudo ./
Some text
> echo $NEW_VAR

> source
Some text
> echo $NEW_VAR
> sudo source
sudo: source: command not found

How to get GMT date in yyyy-mm-dd hh:mm:ss in PHP

You don't have to repeat those format identifiers . For yyyy you just need to have Y, etc.

gmdate('Y-m-d h:i:s \G\M\T', time());

In fact you don't even need to give it a default time if you want current time

gmdate('Y-m-d h:i:s \G\M\T');  // This is fine for your purpose


You can get that list of identifiers Here

Open File Dialog, One Filter for Multiple Excel Extensions?

Use a semicolon

OpenFileDialog of = new OpenFileDialog();
of.Filter = "Excel Files|*.xls;*.xlsx;*.xlsm";

Add CSS to iFrame

Based on solution You've already found How to apply CSS to iframe?:

var cssLink = document.createElement("link") 
cssLink.href = "file://path/to/style.css"; 
cssLink .rel = "stylesheet"; 
cssLink .type = "text/css"; 

or more jqueryish (from Append a stylesheet to an iframe with jQuery):

var $head = $("iframe").contents().find("head");                
    { rel: "stylesheet", href: "file://path/to/style.css", type: "text/css" }));

as for security issues: Disabling same-origin policy in Safari

How to clear a notification in Android

    // Get a notification builder that's compatible with platform versions
    // >= 4
    NotificationCompat.Builder builder = new NotificationCompat.Builder(

this works if you are using a notification builder...

How to add a TextView to a LinearLayout dynamically in Android?

Here is a more general answer for future viewers of this question. The layout we will make is below:

enter image description here

Method 1: Add TextView to existing LinearLayout

protected void onCreate(Bundle savedInstanceState) {

    LinearLayout linearLayout = (LinearLayout) findViewById(;

    // Add textview 1
    TextView textView1 = new TextView(this);
    textView1.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
    textView1.setText("programmatically created TextView1");
    textView1.setBackgroundColor(0xff66ff66); // hex color 0xAARRGGBB
    textView1.setPadding(20, 20, 20, 20);// in pixels (left, top, right, bottom)

    // Add textview 2
    TextView textView2 = new TextView(this);
    LayoutParams layoutParams = new LayoutParams(LayoutParams.WRAP_CONTENT,
    layoutParams.gravity = Gravity.RIGHT;
    layoutParams.setMargins(10, 10, 10, 10); // (left, top, right, bottom)
    textView2.setText("programmatically created TextView2");
    textView2.setTextSize(TypedValue.COMPLEX_UNIT_SP, 18);
    textView2.setBackgroundColor(0xffffdbdb); // hex color 0xAARRGGBB

Note that for LayoutParams you must specify the kind of layout for the import, as in

import android.widget.LinearLayout.LayoutParams;

Otherwise you need to use LinearLayout.LayoutParams in the code.

Here is the xml:

<LinearLayout xmlns:android=""
    android:orientation="vertical" >


Method 2: Create both LinearLayout and TextView programmatically

protected void onCreate(Bundle savedInstanceState) {
    // NOTE: setContentView is below, not here

    // Create new LinearLayout
    LinearLayout linearLayout = new LinearLayout(this);
    linearLayout.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,

    // Add textviews
    TextView textView1 = new TextView(this);
    textView1.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
    textView1.setText("programmatically created TextView1");
    textView1.setBackgroundColor(0xff66ff66); // hex color 0xAARRGGBB
    textView1.setPadding(20, 20, 20, 20); // in pixels (left, top, right, bottom)

    TextView textView2 = new TextView(this);
    LayoutParams layoutParams = new LayoutParams(LayoutParams.WRAP_CONTENT,
    layoutParams.gravity = Gravity.RIGHT;
    layoutParams.setMargins(10, 10, 10, 10); // (left, top, right, bottom)
    textView2.setText("programmatically created TextView2");
    textView2.setTextSize(TypedValue.COMPLEX_UNIT_SP, 18);
    textView2.setBackgroundColor(0xffffdbdb); // hex color 0xAARRGGBB

    // Set context view

Method 3: Programmatically add one xml layout to another xml layout

protected void onCreate(Bundle savedInstanceState) {

    LayoutInflater inflater = (LayoutInflater) getApplicationContext().getSystemService(
    View view = inflater.inflate(R.layout.dynamic_linearlayout_item, null);
    FrameLayout container = (FrameLayout) findViewById(;

Here is dynamic_linearlayout.xml:

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


And here is the dynamic_linearlayout_item.xml to add:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=""
    android:orientation="vertical" >

        android:text="programmatically created TextView1" />

        android:text="programmatically created TextView2" />


Pip Install not installing into correct directory?

I've tried this and it worked for me,

curl -O

tar -zxvf boto3-1.14.29.tar.gz

cd boto3-1.14.29/

Replace X with your required python interpreter, for mine it was python3

sudo pythonX install

Jquery: Checking to see if div contains text, then action

You might want to try the contains selector:

if ($("#field > div.field-item:contains('someText')").length) {

Also, as other mentioned, you must use == or === rather than =.

Batch file for PuTTY/PSFTP file transfer automation

You need to store the psftp script (lines from open to bye) into a separate file and pass that to psftp using -b switch:

cd "C:\Program Files (x86)\PuTTY"
psftp -b "C:\path\to\script\script.txt"


EDIT: For username+password: As you cannot use psftp commands in a batch file, for the same reason, you cannot specify the username and the password as psftp commands. These are inputs to the open command. While you can specify the username with the open command (open <user>@<IP>), you cannot specify the password this way. This can be done on a psftp command line only. Then it's probably cleaner to do all on the command-line:

cd "C:\Program Files (x86)\PuTTY"
psftp -b script.txt <user>@<IP> -pw <PW>

And remove the open, <user> and <PW> lines from your script.txt.


What you are doing atm is that you run psftp without any parameter or commands. Once you exit it (like by typing bye), your batch file continues trying to run open command (and others), what Windows shell obviously does not understand.

If you really want to keep everything in one file (the batch file), you can write commands to psftp standard input, like:

    echo cd ...
    echo lcd ...
    echo put
) | psftp -b script.txt <user>@<IP> -pw <PW>

Switch to another branch without changing the workspace files

Edit: I just noticed that you said you had already created some commits. In that case, use git merge --squash to make a single commit:

git checkout cleanchanges
git merge --squash master
git commit -m "nice commit comment for all my changes"

(Edit: The following answer applies if you have uncommitted changes.)

Just switch branches with git checkout cleanchanges. If the branches refer to the same ref, then all your uncommitted changes will be preserved in your working directory when you switch.

The only time you would have a conflict is if some file in the repository is different between origin/master and cleanchanges. If you just created the branch, then no problem.

As always, if you're at all concerned about losing work, make a backup copy first. Git is designed to not throw away work without asking you first.

Run Excel Macro from Outside Excel Using VBScript From Command Line

I think you are trying to do this? (TRIED AND TESTED)

This code will open the file Test.xls and run the macro TestMacro which will in turn write to the text file TestResult.txt

Option Explicit

Dim xlApp, xlBook

Set xlApp = CreateObject("Excel.Application")
'~~> Change Path here
Set xlBook = xlApp.Workbooks.Open("C:\Test.xls", 0, True)
xlApp.Run "TestMacro"

Set xlBook = Nothing
Set xlApp = Nothing

WScript.Echo "Finished."

Inline JavaScript onclick function

Based on the answer that @Mukund Kumar gave here's a version that passes the event argument to the anonymous function:

<a href="#" onClick="(function(e){
    alert('Hey i am calling');
    return false;
})(arguments[0]);return false;">click here</a>

Choosing the correct upper and lower HSV boundaries for color detection with`cv::inRange` (OpenCV)

Here's a simple HSV color thresholder script to determine the lower/upper color ranges using trackbars for any image on the disk. Simply change the image path in cv2.imread()

enter image description here

import cv2
import numpy as np

def nothing(x):

# Load image
image = cv2.imread('1.jpg')

# Create a window

# Create trackbars for color change
# Hue is from 0-179 for Opencv
cv2.createTrackbar('HMin', 'image', 0, 179, nothing)
cv2.createTrackbar('SMin', 'image', 0, 255, nothing)
cv2.createTrackbar('VMin', 'image', 0, 255, nothing)
cv2.createTrackbar('HMax', 'image', 0, 179, nothing)
cv2.createTrackbar('SMax', 'image', 0, 255, nothing)
cv2.createTrackbar('VMax', 'image', 0, 255, nothing)

# Set default value for Max HSV trackbars
cv2.setTrackbarPos('HMax', 'image', 179)
cv2.setTrackbarPos('SMax', 'image', 255)
cv2.setTrackbarPos('VMax', 'image', 255)

# Initialize HSV min/max values
hMin = sMin = vMin = hMax = sMax = vMax = 0
phMin = psMin = pvMin = phMax = psMax = pvMax = 0

    # Get current positions of all trackbars
    hMin = cv2.getTrackbarPos('HMin', 'image')
    sMin = cv2.getTrackbarPos('SMin', 'image')
    vMin = cv2.getTrackbarPos('VMin', 'image')
    hMax = cv2.getTrackbarPos('HMax', 'image')
    sMax = cv2.getTrackbarPos('SMax', 'image')
    vMax = cv2.getTrackbarPos('VMax', 'image')

    # Set minimum and maximum HSV values to display
    lower = np.array([hMin, sMin, vMin])
    upper = np.array([hMax, sMax, vMax])

    # Convert to HSV format and color threshold
    hsv = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
    mask = cv2.inRange(hsv, lower, upper)
    result = cv2.bitwise_and(image, image, mask=mask)

    # Print if there is a change in HSV value
    if((phMin != hMin) | (psMin != sMin) | (pvMin != vMin) | (phMax != hMax) | (psMax != sMax) | (pvMax != vMax) ):
        print("(hMin = %d , sMin = %d, vMin = %d), (hMax = %d , sMax = %d, vMax = %d)" % (hMin , sMin , vMin, hMax, sMax , vMax))
        phMin = hMin
        psMin = sMin
        pvMin = vMin
        phMax = hMax
        psMax = sMax
        pvMax = vMax

    # Display result image
    cv2.imshow('image', result)
    if cv2.waitKey(10) & 0xFF == ord('q'):


Save string to the NSUserDefaults?

NSString *valueToSave = @"someValue";
[[NSUserDefaults standardUserDefaults] setObject:valueToSave forKey:@"preferenceName"];
[[NSUserDefaults standardUserDefaults] synchronize];

to get it back later

NSString *savedValue = [[NSUserDefaults standardUserDefaults]

What is the difference between SessionState and ViewState?


  • Can be persisted in memory, which makes it a fast solution. Which means state cannot be shared in the Web Farm/Web Garden.
  • Can be persisted in a Database, useful for Web Farms / Web Gardens.
  • Is Cleared when the session dies - usually after 20min of inactivity.


  • Is sent back and forth between the server and client, taking up bandwidth.
  • Has no expiration date.
  • Is useful in a Web Farm / Web Garden

Dynamically updating plot in matplotlib

I know I'm late to answer this question, but for your issue you could look into the "joystick" package. I designed it for plotting a stream of data from the serial port, but it works for any stream. It also allows for interactive text logging or image plotting (in addition to graph plotting). No need to do your own loops in a separate thread, the package takes care of it, just give the update frequency you wish. Plus the terminal remains available for monitoring commands while plotting. See or (use pip install joystick to install)

Just replace np.random.random() by your real data point read from the serial port in the code below:

import joystick as jk
import numpy as np
import time

class test(jk.Joystick):
    # initialize the infinite loop decorator
    _infinite_loop = jk.deco_infinite_loop()

    def _init(self, *args, **kwargs):
        Function called at initialization, see the doc
        self._t0 = time.time()  # initialize time
        self.xdata = np.array([self._t0])  # time x-axis
        self.ydata = np.array([0.0])  # fake data y-axis
        # create a graph frame
        self.mygraph = self.add_frame(jk.Graph(name="test", size=(500, 500), pos=(50, 50), fmt="go-", xnpts=10000, xnptsmax=10000, xylim=(None, None, 0, 1)))

    def _generate_data(self):  # function looped every 0.2 second to read or produce data
        Loop starting with the simulation start, getting data and
    pushing it to the graph every 0.2 seconds
        # concatenate data on the time x-axis
        self.xdata = jk.core.add_datapoint(self.xdata, time.time(), xnptsmax=self.mygraph.xnptsmax)
        # concatenate data on the fake data y-axis
        self.ydata = jk.core.add_datapoint(self.ydata, np.random.random(), xnptsmax=self.mygraph.xnptsmax)
        self.mygraph.set_xydata(t, self.ydata)

t = test()

Emulate a 403 error page

Refresh the page after sending the 403:

header('HTTP/1.0 403 Forbidden');
<meta http-equiv="refresh" content="0;URL=">

Angular 2.0 and Modal Dialog

Here is my full implementation of modal bootstrap angular2 component:

I assume that in your main index.html file (with <html> and <body> tags) at the bottom of <body> tag you have:

  <script src="assets/js/jquery-2.1.1.js"></script>
  <script src="assets/js/bootstrap.min.js"></script>


import { Component, Input, Output, ElementRef, EventEmitter, AfterViewInit } from '@angular/core';

declare var $: any;// this is very importnant (to work this line: this.modalEl.modal('show')) - don't do this (becouse this owerride jQuery which was changed by bootstrap, included in main html-body template): let $ = require('../../../../../node_modules/jquery/dist/jquery.min.js');

  selector: 'modal',
  templateUrl: './modal.html',
export class Modal implements AfterViewInit {

    @Input() title:string;
    @Input() showClose:boolean = true;
    @Output() onClose: EventEmitter<any> = new EventEmitter();

    modalEl = null;
    id: string = uniqueId('modal_');

    constructor(private _rootNode: ElementRef) {}

    open() {

    close() {

    closeInternal() { // close modal when click on times button in up-right corner; // emit event

    ngAfterViewInit() {
        this.modalEl = $(this._rootNode.nativeElement).find('div.modal');

    has(selector) {
        return $(this._rootNode.nativeElement).find(selector).length;

let modal_id: number = 0;
export function uniqueId(prefix: string): string {
    return prefix + ++modal_id;


<div class="modal inmodal fade" id="{{modal_id}}" tabindex="-1" role="dialog"  aria-hidden="true" #thisModal>
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header" [ngClass]="{'hide': !(has('mhead') || title) }">
                <button *ngIf="showClose" type="button" class="close" (click)="closeInternal()"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span></button>
                <ng-content select="mhead"></ng-content>
                <h4 *ngIf='title' class="modal-title">{{ title }}</h4>
            <div class="modal-body">

            <div class="modal-footer" [ngClass]="{'hide': !has('mfoot') }" >
                <ng-content select="mfoot"></ng-content>

And example of usage in client Editor component: client-edit-component.ts:

import { Component } from '@angular/core';
import { ClientService } from './client.service';
import { Modal } from '../common';

  selector: 'client-edit',
  directives: [ Modal ],
  templateUrl: './client-edit.html',
  providers: [ ClientService ]
export class ClientEdit {

    _modal = null;

    constructor(private _ClientService: ClientService) {}

    bindModal(modal) {this._modal=modal;}

    open(client) {;

    close() {



<modal [title]='"Some standard title"' [showClose]='true' (onClose)="close()" #editModal>{{ bindModal(editModal) }}
    <mhead>Som non-standart title</mhead>
    Some contents
    <mfoot><button calss='btn' (click)="close()">Close</button></mfoot>

Ofcourse title, showClose, <mhead> and <mfoot> ar optional parameters/tags.

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


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

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

Converting Secret Key into a String and Vice Versa

To show how much fun it is to create some functions that are fail fast I've written the following 3 functions.

One creates an AES key, one encodes it and one decodes it back. These three methods can be used with Java 8 (without dependence of internal classes or outside dependencies):

public static SecretKey generateAESKey(int keysize)
        throws InvalidParameterException {
    try {
        if (Cipher.getMaxAllowedKeyLength("AES") < keysize) {
            // this may be an issue if unlimited crypto is not installed
            throw new InvalidParameterException("Key size of " + keysize
                    + " not supported in this runtime");

        final KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        return keyGen.generateKey();
    } catch (final NoSuchAlgorithmException e) {
        // AES functionality is a requirement for any Java SE runtime
        throw new IllegalStateException(
                "AES should always be present in a Java SE runtime", e);

public static SecretKey decodeBase64ToAESKey(final String encodedKey)
        throws IllegalArgumentException {
    try {
        // throws IllegalArgumentException - if src is not in valid Base64
        // scheme
        final byte[] keyData = Base64.getDecoder().decode(encodedKey);
        final int keysize = keyData.length * Byte.SIZE;

        // this should be checked by a SecretKeyFactory, but that doesn't exist for AES
        switch (keysize) {
        case 128:
        case 192:
        case 256:
            throw new IllegalArgumentException("Invalid key size for AES: " + keysize);

        if (Cipher.getMaxAllowedKeyLength("AES") < keysize) {
            // this may be an issue if unlimited crypto is not installed
            throw new IllegalArgumentException("Key size of " + keysize
                    + " not supported in this runtime");

        // throws IllegalArgumentException - if key is empty
        final SecretKeySpec aesKey = new SecretKeySpec(keyData, "AES");
        return aesKey;
    } catch (final NoSuchAlgorithmException e) {
        // AES functionality is a requirement for any Java SE runtime
        throw new IllegalStateException(
                "AES should always be present in a Java SE runtime", e);

public static String encodeAESKeyToBase64(final SecretKey aesKey)
        throws IllegalArgumentException {
    if (!aesKey.getAlgorithm().equalsIgnoreCase("AES")) {
        throw new IllegalArgumentException("Not an AES key");

    final byte[] keyData = aesKey.getEncoded();
    final String encodedKey = Base64.getEncoder().encodeToString(keyData);
    return encodedKey;

Reset Entity-Framework Migrations

Enable-Migrations -EnableAutomaticMigrations -Force

How do I check my gcc C++ compiler version for my Eclipse?

gcc -dumpversion

-dumpversion Print the compiler version (for example, 3.0) — and don't do anything else.

The same works for following compilers/aliases:

cc -dumpversion
g++ -dumpversion
clang -dumpversion
tcc -dumpversion

Be careful with automate parsing the GCC output:

  • Output of --version might be localized (e.g. to Russian, Chinese, etc.)
  • GCC might be built with option --with-gcc-major-version-only. And some distros (e.g. Fedora) are already using that
  • GCC might be built with option --with-pkgversion. And --version output will contain something like Android (5220042 based on r346389c) clang version 8.0.7 (it's real version string)

Filtering a pyspark dataframe using isin by exclusion

Also could be like this

df.filter(col('bar').isin(['a','b']) == False).show()

How to get Exception Error Code in C#

Another method would be to get the error code from the exception class directly. For example:

catch (Exception ex)
    if (ex.InnerException is ServiceResponseException)
        ServiceResponseException srex = ex.InnerException as ServiceResponseException;
        string ErrorCode = srex.ErrorCode.ToString();

Save matplotlib file to a directory

According to the docs savefig accepts a file path, so all you need is to specify a full (or relative) path instead of a file name.

Java: how do I initialize an array size if it's unknown?

You should use a List for something like this, not an array. As a general rule of thumb, when you don't know how many elements you will add to an array before hand, use a List instead. Most would probably tackle this problem by using an ArrayList.

If you really can't use a List, then you'll probably have to use an array of some initial size (maybe 10?) and keep track of your array capacity versus how many elements you're adding, and copy the elements to a new, larger array if you run out of room (this is essentially what ArrayList does internally). Also note that, in the real world, you would never do it this way - you would use one of the standard classes that are made specifically for cases like this, such as ArrayList.

ActionBarActivity: cannot be resolved to a type

I was also following the instructions on

and even though I did everything in the tutorial, as soon as "extends Action" is changed to "extends ActionBarActivity" all sorts of errors appear in Eclipse, including the "ActionBarActivitycannot be resolved to a type"

None of the above solutions worked for me, but what did work is adding this line to the top:


redistributable offline .NET Framework 3.5 installer for Windows 8

Microsoft .NET framework 3.5 can be installed on windows 10 without having installation media. The file you need is called Just google it and you will get the download links. After downloading it, copy that file to C:\dotnet35 and run the following command.

Dism.exe /online /enable-feature /featurename:NetFX3 /All /Source:c:\dotnet35 /LimitAccess

Tested and worked in Windows 10 without any issue.

how to show calendar on text box click in html

What you need is a jQuery UI Datepicker

Check out the demo and the source code.

How to display list items on console window in C#

You can also use List's inbuilt foreach, such as:

List<T>.ForEach(item => Console.Write(item));

This code also runs significantly faster!

The above code also makes you able to manipulate Console.WriteLine, such as doing:

List<T>.ForEach(item => Console.Write(item + ",")); //Put a,b etc.

How can I analyze a heap dump in IntelliJ? (memory leak)

There also exists a 'JVM Debugger Memory View' found in the plugin repository, which could be useful.

Get combobox value in Java swing

If the string is empty, comboBox.getSelectedItem().toString() will give a NullPointerException. So better to typecast by (String).

Remove empty lines in a text file via grep

Try ex-way:

ex -s +'v/\S/d' -cwq test.txt

For multiple files (edit in-place):

ex -s +'bufdo!v/\S/d' -cxa *.txt

Without modifying the file (just print on the standard output):

cat test.txt | ex -s +'v/\S/d' +%p +q! /dev/stdin

Inheritance and Overriding __init__ in python

If the FileInfo class has more than one ancestor class then you should definitely call all of their __init__() functions. You should also do the same for the __del__() function, which is a destructor.

How to save a base64 image to user's disk using JavaScript?

HTML5 download attribute

Just to allow user to download the image or other file you may use the HTML5 download attribute.

Static file download

<a href="/images/image-name.jpg" download>
<!-- OR -->
<a href="/images/image-name.jpg" download="new-image-name.jpg"> 

Dynamic file download

In cases requesting image dynamically it is possible to emulate such download.

If your image is already loaded and you have the base64 source then:

function saveBase64AsFile(base64, fileName) {
    var link = document.createElement("a");

    document.body.appendChild(link); // for Firefox

    link.setAttribute("href", base64);
    link.setAttribute("download", fileName);;

Otherwise if image file is downloaded as Blob you can use FileReader to convert it to Base64:

function saveBlobAsFile(blob, fileName) {
    var reader = new FileReader();

    reader.onloadend = function () {    
        var base64 = reader.result ;
        var link = document.createElement("a");

        document.body.appendChild(link); // for Firefox

        link.setAttribute("href", base64);
        link.setAttribute("download", fileName);;



The anchor tag you are creating also needs to be added to the DOM in Firefox, in order to be recognized for click events (Link).

IE is not supported: Caniuse link

How do I prevent a form from being resized by the user?

If you want to prevent resize by dragging sizegrips and by the maximize button and by maximize by doubleclick on the header text, than insert the following code in the load event of the form:

    Me.FormBorderStyle = Windows.Forms.FormBorderStyle.FixedSingle ' Prevent size grips
    Me.MaximumSize = Me.Size ' Prevent maximize (also by doubleclick of header text)

Of course all choices of a formborderstyle beginning with Fixed will do.

How do I implement onchange of <input type="text"> with jQuery?

You can do this in different ways, keyup is one of them. But i am giving example below with on change.

$('input[name="vat_id"]').on('change', function() {
    if($(this).val().length == 0) {
        alert('Input field is empty');

NB: input[name="vat_id"] replace with your input ID or name.

Two's Complement in Python

in case someone needs the inverse direction too:

def num_to_bin(num, wordsize):
    if num < 0:
        num = 2**wordsize+num
    base = bin(num)[2:]
    padding_size = wordsize - len(base)
    return '0' * padding_size + base

for i in range(7, -9, -1):
    print num_to_bin(i, 4)

should output this: 0111 0110 0101 0100 0011 0010 0001 0000 1111 1110 1101 1100 1011 1010 1001 1000

Get the name of a pandas DataFrame

Sometimes doesn't work.

you might get an error message:

'DataFrame' object has no attribute 'name'

try the below function:

def get_df_name(df):
    name =[x for x in globals() if globals()[x] is df][0]
    return name

How to add multiple columns to pandas dataframe in one assignment?

If you just want to add empty new columns, reindex will do the job

   col_1  col_2
0      0      4
1      1      5
2      2      6
3      3      7

df.reindex(list(df)+['column_new_1', 'column_new_2','column_new_3'], axis=1)
   col_1  col_2  column_new_1  column_new_2  column_new_3
0      0      4           NaN           NaN           NaN
1      1      5           NaN           NaN           NaN
2      2      6           NaN           NaN           NaN
3      3      7           NaN           NaN           NaN

full code example

import numpy as np
import pandas as pd

df = {'col_1': [0, 1, 2, 3],
        'col_2': [4, 5, 6, 7]}
df = pd.DataFrame(df)
print('df',df, sep='\n')
df=df.reindex(list(df)+['column_new_1', 'column_new_2','column_new_3'], axis=1)
print('''df.reindex(list(df)+['column_new_1', 'column_new_2','column_new_3'], axis=1)''',df, sep='\n')

otherwise go for zeros answer with assign

Plotting using a CSV file

This should get you started:

set datafile separator ","
plot 'infile' using 0:1

jQuery: Performing synchronous AJAX requests

As you're making a synchronous request, that should be

function getRemote() {
    return $.ajax({
        type: "GET",
        url: remote_url,
        async: false

Example -

PLEASE NOTE: Setting async property to false is deprecated and in the process of being removed (link). Many browsers including Firefox and Chrome have already started to print a warning in the console if you use this:


Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check


Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user’s experience. For more help

how to overcome ERROR 1045 (28000): Access denied for user 'ODBC'@'localhost' (using password: NO) permanently

I tried this and it worked:

C:\cd MySQL installed path\MySQL -uyourusername -pyourpassword

clear data inside text file in c++

If you simply open the file for writing with the truncate-option, you'll delete the content.

std::ofstream ofs;"test.txt", std::ofstream::out | std::ofstream::trunc);

.crx file install in chrome

In case Chrome tells you "This can only be added from the Chrome Web Store", you can try the following:

  • Go to the webstore and try to add the extension
  • It will fail and give you a download instead
  • Rename the downloaded file to .zip and unpack it to a directory (you might get a warning about a corrupt zip header, but most unpacker will continue anyway)
  • Go to Settings -> Tools -> Extensions
  • Enable developer mode
  • Click "Load unpacked extention"
  • Browse to the unpacked folder and install your extention

How to get exception message in Python properly

If you look at the documentation for the built-in errors, you'll see that most Exception classes assign their first argument as a message attribute. Not all of them do though.

Notably,EnvironmentError (with subclasses IOError and OSError) has a first argument of errno, second of strerror. There is no message... strerror is roughly analogous to what would normally be a message.

More generally, subclasses of Exception can do whatever they want. They may or may not have a message attribute. Future built-in Exceptions may not have a message attribute. Any Exception subclass imported from third-party libraries or user code may not have a message attribute.

I think the proper way of handling this is to identify the specific Exception subclasses you want to catch, and then catch only those instead of everything with an except Exception, then utilize whatever attributes that specific subclass defines however you want.

If you must print something, I think that printing the caught Exception itself is most likely to do what you want, whether it has a message attribute or not.

You could also check for the message attribute if you wanted, like this, but I wouldn't really suggest it as it just seems messy:

except Exception as e:
    # Just print(e) is cleaner and more likely what you want,
    # but if you insist on printing message specifically whenever possible...
    if hasattr(e, 'message'):

Declaring variables inside or outside of a loop

if you want to use str outside looop also; declare it outside. otherwise, 2nd version is fine.

Mysql: Select rows from a table that are not in another

FROM Table1 AS a
  FROM Table2 AS b 
  WHERE a.FirstName=b.FirstName AND a.LastName=b.Last_Name

EXISTS will help you...

How to use hex color values

extension UIColor {

    convenience init(r: CGFloat, g: CGFloat, b: CGFloat, a: CGFloat = 1) {
        self.init(red: r/255, green: g/255, blue: b/255, alpha: a)

    convenience init(hex: Int, alpha: CGFloat = 1) {
        self.init(r: CGFloat((hex >> 16) & 0xff), g: CGFloat((hex >> 08) & 0xff), b: CGFloat((hex >> 00) & 0xff), a: alpha)

Stylesheet not updating

This may not have been the OP's problem, but I had the same problem and solved it by flushing then disabling Supercache on my cpanel. Perhaps some other newbies like myself won't know that many hosting providers cache CSS and some other static files, and these cached old versions of CSS files will persist in the cloud for hours after you edit the file on your server. If your site serves up old versions of CSS files after you edit them, and you're certain you've cleared your browser cache, and you don't know whether your host is caching stuff, check that first before you try any other more complicated suggestions.

?: ?? Operators Instead Of IF|ELSE

The ternary operator RETURNS one of two values. Or, it can execute one of two statements based on its condition, but that's generally not a good idea, as it can lead to unintended side-effects.

bar ? () : baz();

In this case, the () does nothing, while baz does something. But you've only made the code less clear. I'd go for more verbose code that's clearer and easier to maintain.

Further, this makes little sense at all:

var foo = bar ? () : baz();

since () has no return type (it's void) and baz has a return type that's unknown at the point of call in this sample. If they don't agree, the compiler will complain, and loudly.

Is there a java setting for disabling certificate validation?

It is very simple .In my opinion it is the best way for everyone

       HttpResponse<String> response = null;
       try {
           Gson gson = new Gson();
           response ="your_api_url")
                   .header("Authorization", "Basic " + "authkey")
                   .header("Content-Type", "application/json")
           System.out.println("------RESPONSE -------"+ gson.toJson(response.getBody()));
       } catch (Exception e) {
           System.out.println("------RESPONSE ERROR--");

Semaphore vs. Monitors - what's the difference?

One Line Answer:

Monitor: controls only ONE thread at a time can execute in the monitor. (need to acquire lock to execute the single thread)

Semaphore: a lock that protects a shared resource. (need to acquire the lock to access resource)

How to check variable type at runtime in Go language

What's wrong with

func (e *Easy)SetStringOption(option Option, param string)
func (e *Easy)SetLongOption(option Option, param long)

and so on?

Center a 'div' in the middle of the screen, even when the page is scrolled up or down?

I just found a new trick to center a box in the middle of the screen even if you don't have fixed dimensions. Let's say you would like a box 60% width / 60% height. The way to make it centered is by creating 2 boxes: a "container" box that position left: 50% top :50%, and a "text" box inside with reverse position left: -50%; top :-50%;

It works and it's cross browser compatible.

Check out the code below, you probably get a better explanation:

jQuery('.close a, .bg', '#message').on('click', function() {_x000D_
  return false;_x000D_
html, body {_x000D_
  min-height: 100%;_x000D_
#message {_x000D_
  height: 100%;_x000D_
  left: 0;_x000D_
  position: fixed;_x000D_
  top: 0;_x000D_
  width: 100%;_x000D_
#message .container {_x000D_
  height: 60%;_x000D_
  left: 50%;_x000D_
  position: absolute;_x000D_
  top: 50%;_x000D_
  z-index: 10;_x000D_
  width: 60%;_x000D_
#message .container .text {_x000D_
  background: #fff;_x000D_
  height: 100%;_x000D_
  left: -50%;_x000D_
  position: absolute;_x000D_
  top: -50%;_x000D_
  width: 100%;_x000D_
#message .bg {_x000D_
  background: rgba(0, 0, 0, 0.5);_x000D_
  height: 100%;_x000D_
  left: 0;_x000D_
  position: absolute;_x000D_
  top: 0;_x000D_
  width: 100%;_x000D_
  z-index: 9;_x000D_
<script src=""></script>_x000D_
<div id="message">_x000D_
  <div class="container">_x000D_
    <div class="text">_x000D_
      <p>The message</p>_x000D_
      <p class="close"><a href="#">Close Window</a></p>_x000D_
  <div class="bg"></div>_x000D_

How to Set Variables in a Laravel Blade Template

Ya'll are making it too complicated.

Just use plain php

<?php $i = 1; ?>


(or looks pretty straighforward too)

We're all kinda "hacking" the system by setting variables in views, so why make the "hack" more complicated then it needs to be?

Tested in Laravel 4.

Another benefit is that syntax highlighting works properly (I was using comment hack before and it was awful to read)

Sending HTTP Post request with SOAP action using org.apache.http

The soapAction must passed as a http-header parameter - when used, it's not part of the http-body/payload.

Look here for an example with apache httpclient:

React Native fixed footer

I'm using fixed footers for buttons in my app. The way I implement a fixed footer is like so:

<View style={{flex: 1}}>
<View><Text>my text</Text></View>
<View style={{position: 'absolute', left: 0, right: 0, bottom: 0}}><Text>My fixed footer</Text></View>

And if need the footer to move up when a keyboard appears for instance you can use:

const {  DeviceEventEmitter } = React

class MyClass {
  constructor() {
     this.state = {
       btnLocation: 0

  componentWillMount() {
     DeviceEventEmitter.addListener('keyboardWillShow', this.keyboardWillShow.bind(this))
     DeviceEventEmitter.addListener('keyboardWillHide', this.keyboardWillHide.bind(this))

  keyboardWillShow(e) {
    this.setState({btnLocation: e.endCoordinates.height})

  keyboardWillHide(e) {
    this.setState({btnLocation: 0})

Then use {bottom: this.state.btnLocation} in your fixed footer class. I hope this helps!

How do you force a CIFS connection to unmount

umount -a -t cifs -l

worked like a charm for me on CentOS 6.3. It saved me a server reboot.

How do I connect to a terminal to a serial-to-USB device on Ubuntu 10.10 (Maverick Meerkat)?

I get get the same minicom error, "cannot open /dev/ttyUSB0: No such file or directory"

Three notes:

  1. I get the error when the device attached to the serial port end of my Prolific Technology PL2303 USB/Serial adapter is turned off. After turning on the device (an embedded controller running Linux) minicom connected fine.

  2. I have to run as super user (i.e. sudo minicom)

  3. Sometimes I have to unplug and plug back in the USB-to-serial adapter to get minicom to connect to it.

I am running Ubuntu 10.04 LTS (Lucid Lynx) under VMware (running on Windows 7). In this situation, make sure the device is attached to VM operating system by right clicking on the USB/Serial USB icon in the lower right of the VMware window and select Connect (Disconnect from Host).

Remember to press Ctrl + A to get minicom's prompt, and type X to exit the program. Just exiting the terminal session running minicom will leave the process running.

Generating a UUID in Postgres for Insert statement?

PostgreSQL 13 supports natively gen_random_uuid ():

PostgreSQL includes one function to generate a UUID:

gen_random_uuid () ? uuid

This function returns a version 4 (random) UUID. This is the most commonly used type of UUID and is appropriate for most applications.

db<>fiddle demo

CardView not showing Shadow in Android L

check hardwareAccelerated in manifest make it true , making it false removes shadows , when false shadow appears in xml preview but not in phone .

How can I detect when the mouse leaves the window?

Please keep in mind that my answer has aged a lot.

This type of behavior is usually desired while implementing drag-drop behavior on an html page. The solution below was tested on IE 8.0.6, FireFox 3.6.6, Opera 10.53, and Safari 4 on an MS Windows XP machine.
First a little function from Peter-Paul Koch; cross browser event handler:

function addEvent(obj, evt, fn) {
    if (obj.addEventListener) {
        obj.addEventListener(evt, fn, false);
    else if (obj.attachEvent) {
        obj.attachEvent("on" + evt, fn);

And then use this method to attach an event handler to the document objects mouseout event:

addEvent(document, "mouseout", function(e) {
    e = e ? e : window.event;
    var from = e.relatedTarget || e.toElement;
    if (!from || from.nodeName == "HTML") {
        // stop your drag event here
        // for now we can just use an alert
        alert("left window");

Finally, here is an html page with the script embedded for debugging:

<script type="text/javascript">
function addEvent(obj, evt, fn) {
    if (obj.addEventListener) {
        obj.addEventListener(evt, fn, false);
    else if (obj.attachEvent) {
        obj.attachEvent("on" + evt, fn);
addEvent(window,"load",function(e) {
    addEvent(document, "mouseout", function(e) {
        e = e ? e : window.event;
        var from = e.relatedTarget || e.toElement;
        if (!from || from.nodeName == "HTML") {
            // stop your drag event here
            // for now we can just use an alert
            alert("left window");

Java serialization - local class incompatible

For me, I forgot to add the default serial id.

private static final long serialVersionUID = 1L;

Call a method of a controller from another controller using 'scope' in AngularJS

Here is good Demo in Fiddle how to use shared service in directive and other controllers through $scope.$on


<div ng-controller="ControllerZero">
    <input ng-model="message" >
    <button ng-click="handleClick(message);">BROADCAST</button>

<div ng-controller="ControllerOne">
    <input ng-model="message" >

<div ng-controller="ControllerTwo">
    <input ng-model="message" >

<my-component ng-model="message"></my-component>


var myModule = angular.module('myModule', []);

myModule.factory('mySharedService', function($rootScope) {
    var sharedService = {};

    sharedService.message = '';

    sharedService.prepForBroadcast = function(msg) {
        this.message = msg;

    sharedService.broadcastItem = function() {

    return sharedService;

By the same way we can use shared service in directive. We can implement controller section into directive and use $scope.$on

myModule.directive('myComponent', function(mySharedService) {
    return {
        restrict: 'E',
        controller: function($scope, $attrs, mySharedService) {
            $scope.$on('handleBroadcast', function() {
                $scope.message = 'Directive: ' + mySharedService.message;
        replace: true,
        template: '<input>'

And here three our controllers where ControllerZero used as trigger to invoke prepForBroadcast

function ControllerZero($scope, sharedService) {
    $scope.handleClick = function(msg) {

    $scope.$on('handleBroadcast', function() {
        $scope.message = sharedService.message;

function ControllerOne($scope, sharedService) {
    $scope.$on('handleBroadcast', function() {
        $scope.message = 'ONE: ' + sharedService.message;

function ControllerTwo($scope, sharedService) {
    $scope.$on('handleBroadcast', function() {
        $scope.message = 'TWO: ' + sharedService.message;

The ControllerOne and ControllerTwo listen message change by using $scope.$on handler.

Why can't I use background image and color together?

background:url(directoryName/imageName.extention) bottom left no-repeat; 
background-color: red;

how to display a div triggered by onclick event

Here you go:

    display: none;

document.querySelector("button").addEventListener("click", function(){
    document.querySelector("div").style.display = "block";

<div>blah blah blah</div>


Convert file to byte array and vice versa

You cannot do it for File, which is primarily an intelligent file path. Can you refactor your code so that it declares the variables, and passes around arguments, with type OutputStream instead of FileOutputStream? If so, see classes and

OutputStream outStream = new ByteArrayOutputStream();
byte[] data = outStream.toByteArray();
InputStream inStream = new ByteArrayInputStream(data);

Android Studio emulator does not come with Play Store for API 23

Now there's no need to side load any packages of execute any scripts to get the Play Store on the emulator. Starting from Android Studio 2.4 now you can create an AVD that has Play Store pre-installed on it. Currently it is supported only on the AVDs running Android 7.0 (API 24) system images.

Official Source

AVD with Play Store

Note: Compatible devices are denoted by the new Play Store column.

How to disable Python warnings?

import sys
if not sys.warnoptions:
    import warnings

Change ignore to default when working on the file or adding new functionality to re-enable warnings.

Getting a random value from a JavaScript array

By adding a method on prototype of array you can get random values easly.

In this example you can get single or multiple random values from array.

You can run to test code by clicking snippet button.

Array.prototype.random = function(n){
    const a = [];
    for(let i = 0;i<n;i++){
    return a;
  } else {
    return this[Math.floor(Math.random()*this.length)];

const mySampleArray =  ['a','b','c','d','e','f','g','h'];

mySampleArray.random(); // return any random value etc. 'a', 'b'
mySampleArray.random(3); //retun an array with random values etc: ['b','f','a'] , ['d','b','d']


Visual Studio popup: "the operation could not be completed"

I had a similar problem on opening Razor Views

  • I logged on to my Azure account which was asking to re-enter my credntials.
  • Restart VS 2015 Update 1

How could I create a function with a completion handler in Swift?

I'm a little confused about custom made completion handlers. In your example:

Say you have a download function to download a file from network,and want to be notified when download task has finished.

typealias CompletionHandler = (success:Bool) -> Void

func downloadFileFromURL(url: NSURL,completionHandler: CompletionHandler) {

    // download code.

    let flag = true // true if download succeed,false otherwise

    completionHandler(success: flag)

Your // download code will still be ran asynchronously. Why wouldn't the code go straight to your let flag = true and completion Handler(success: flag) without waiting for your download code to be finished?

"FATAL: Module not found error" using modprobe

Ensure that your network is brought down before loading module:

sudo stop networking

It helped me -

How to access parameters in a RESTful POST method

Your @POST method should be accepting a JSON object instead of a string. Jersey uses JAXB to support marshaling and unmarshaling JSON objects (see the jersey docs for details). Create a class like:

public class MyJaxBean {
    @XmlElement public String param1;
    @XmlElement public String param2;

Then your @POST method would look like the following:

@POST @Consumes("application/json")
public void create(final MyJaxBean input) {
    System.out.println("param1 = " + input.param1);
    System.out.println("param2 = " + input.param2);

This method expects to receive JSON object as the body of the HTTP POST. JAX-RS passes the content body of the HTTP message as an unannotated parameter -- input in this case. The actual message would look something like:

POST /create HTTP/1.1
Content-Type: application/json
Content-Length: 35


Using JSON in this way is quite common for obvious reasons. However, if you are generating or consuming it in something other than JavaScript, then you do have to be careful to properly escape the data. In JAX-RS, you would use a MessageBodyReader and MessageBodyWriter to implement this. I believe that Jersey already has implementations for the required types (e.g., Java primitives and JAXB wrapped classes) as well as for JSON. JAX-RS supports a number of other methods for passing data. These don't require the creation of a new class since the data is passed using simple argument passing.


The parameters would be annotated using @FormParam:

public void create(@FormParam("param1") String param1,
                   @FormParam("param2") String param2) {

The browser will encode the form using "application/x-www-form-urlencoded". The JAX-RS runtime will take care of decoding the body and passing it to the method. Here's what you should see on the wire:

POST /create HTTP/1.1
Content-Type: application/x-www-form-urlencoded;charset=UTF-8
Content-Length: 25


The content is URL encoded in this case.

If you do not know the names of the FormParam's you can do the following:

@POST @Consumes("application/x-www-form-urlencoded")
public void create(final MultivaluedMap<String, String> formParams) {

HTTP Headers

You can using the @HeaderParam annotation if you want to pass parameters via HTTP headers:

public void create(@HeaderParam("param1") String param1,
                   @HeaderParam("param2") String param2) {

Here's what the HTTP message would look like. Note that this POST does not have a body.

POST /create HTTP/1.1
Content-Length: 0
param1: hello
param2: world

I wouldn't use this method for generalized parameter passing. It is really handy if you need to access the value of a particular HTTP header though.

HTTP Query Parameters

This method is primarily used with HTTP GETs but it is equally applicable to POSTs. It uses the @QueryParam annotation.

public void create(@QueryParam("param1") String param1,
                   @QueryParam("param2") String param2) {

Like the previous technique, passing parameters via the query string does not require a message body. Here's the HTTP message:

POST /create?param1=hello&param2=world HTTP/1.1
Content-Length: 0

You do have to be particularly careful to properly encode query parameters on the client side. Using query parameters can be problematic due to URL length restrictions enforced by some proxies as well as problems associated with encoding them.

HTTP Path Parameters

Path parameters are similar to query parameters except that they are embedded in the HTTP resource path. This method seems to be in favor today. There are impacts with respect to HTTP caching since the path is what really defines the HTTP resource. The code looks a little different than the others since the @Path annotation is modified and it uses @PathParam:

public void create(@PathParam("param1") String param1,
                   @PathParam("param2") String param2) {

The message is similar to the query parameter version except that the names of the parameters are not included anywhere in the message.

POST /create/hello/world HTTP/1.1
Content-Length: 0

This method shares the same encoding woes that the query parameter version. Path segments are encoded differently so you do have to be careful there as well.

As you can see, there are pros and cons to each method. The choice is usually decided by your clients. If you are serving FORM-based HTML pages, then use @FormParam. If your clients are JavaScript+HTML5-based, then you will probably want to use JAXB-based serialization and JSON objects. The MessageBodyReader/Writer implementations should take care of the necessary escaping for you so that is one fewer thing that can go wrong. If your client is Java based but does not have a good XML processor (e.g., Android), then I would probably use FORM encoding since a content body is easier to generate and encode properly than URLs are. Hopefully this mini-wiki entry sheds some light on the various methods that JAX-RS supports.

Note: in the interest of full disclosure, I haven't actually used this feature of Jersey yet. We were tinkering with it since we have a number of JAXB+JAX-RS applications deployed and are moving into the mobile client space. JSON is a much better fit that XML on HTML5 or jQuery-based solutions.

How to set conditional breakpoints in Visual Studio?

Writing the actual condition can be the tricky part, so I tend to

  1. Set a regular breakpoint.
  2. Run the code until the breakpoint is hit for the first time.
  3. Use the Immediate Window (Debug > Windows > Immediate) to test your expression.
  4. Right-click the breakpoint, click Condition and paste in your expression.

Advantages of using the Immediate window:

  • It has IntelliSense.
  • You can be sure that the variables in the expression are in scope when the expression is evaluated.
  • You can be sure your expression returns true or false.

This example breaks when the code is referring to a table with the name "Setting":


How to extract text from a string using sed?

sed doesn't recognize \d, use [[:digit:]] instead. You will also need to escape the + or use the -r switch (-E on OS X).

Note that [0-9] works as well for Arabic-Hindu numerals.

What is the use of the JavaScript 'bind' method?


The bind() method takes an object as an first argument and creates a new function. When the function is invoked the value of this in the function body will be the object which was passed in as an argument in the bind() function.

How does this work in JS anyway

The value of this in javascript is dependent always depends on what Object the function is called. The value of this always refers to the object left of the dot from where is the function is called. In case of the global scope this is window (or global in nodeJS). Only call, apply and bind can alter the this binding differently. Here is an example to show how the this keyword works:

let obj = {_x000D_
  prop1: 1,_x000D_
  func: function () { console.log(this); } _x000D_
obj.func();   // obj left of the dot so this refers to obj_x000D_
const customFunc = obj.func;  // we store the function in the customFunc obj_x000D_
customFunc();  // now the object left of the dot is window, _x000D_
               // customFunc() is shorthand for window.customFunc()_x000D_
               // Therefore window will be logged

How is bind used?

Bind can help in overcoming difficulties with the this keyword by having a fixed object where this will refer to. For example:

var name = 'globalName';_x000D_
const obj = {_x000D_
  name: 'myName',_x000D_
  sayName: function () { console.log(;}_x000D_
const say = obj.sayName; // we are merely storing the function the value of this isn't magically transferred_x000D_
say(); // now because this function is executed in global scope this will refer to the global var_x000D_
const boundSay = obj.sayName.bind(obj); // now the value of this is bound to the obj object_x000D_
boundSay();  // Now this will refer to the name in the obj object: 'myName'

Once the function is bound to a particular this value we can pass it around and even put it on properties on other objects. The value of this will remain the same.

mysqldump exports only one table

Here I am going to export 3 tables from database named myDB in an sql file named table.sql

mysqldump -u root -p myDB table1 table2 table3 > table.sql

Simple way to find if two different lists contain exactly the same elements?

Sample code:

public static '<'T'>' boolean isListDifferent(List'<'T'>' previousList,
        List'<'T'>' newList) {

    int sizePrevoisList = -1;
    int sizeNewList = -1;

    if (previousList != null && !previousList.isEmpty()) {
        sizePrevoisList = previousList.size();
    if (newList != null && !newList.isEmpty()) {
        sizeNewList = newList.size();

    if ((sizePrevoisList == -1) && (sizeNewList == -1)) {
        return false;

    if (sizeNewList != sizePrevoisList) {
        return true;

    List n_prevois = new ArrayList(previousList);
    List n_new = new ArrayList(newList);

    try {
    } catch (ClassCastException exp) {
        return true;

    for (int i = 0; i < sizeNewList; i++) {
        Object obj_prevois = n_prevois.get(i);
        Object obj_new = n_new.get(i);
        if (obj_new.equals(obj_prevois)) {
            // Object are same
        } else {
            return true;

    return false;

how to use LIKE with column name

You're close.

The LIKE operator works with strings (CHAR, NVARCHAR, etc). so you need to concattenate the '%' symbol to the string...

MS SQL Server:

SELECT * FROM table1,table2 WHERE table1.x LIKE table2.y + '%'

Use of LIKE, however, is often slower than other operations. It's useful, powerful, flexible, but has performance considerations. I'll leave those for another topic though :)


I don't use MySQL, but this may work...

SELECT * FROM table1,table2 WHERE table1.x LIKE CONCAT(table2.y, '%')

Disabling swap files creation in vim

Set the following variables in .vimrc or /etc/vimrc to make vim put swap, backup and undo files in a special location instead of the working directory of the file being edited:

set backupdir=~/.vim/backup//
set directory=~/.vim/swap//
set undodir=~/.vim/undo//

Using double trailing slashes in the path tells vim to enable a feature where it avoids name collisions. For example, if you edit a file in one location and another file in another location and both files have the same name, you don't want a name collision to occur in ~/.vim/swap/. If you specify ~/.vim/swap// with two trailing slashes vim will create swap files using the whole path of the files being edited to avoid collisions (slashes in the file's path will be replaced by percent symbol %).

For example, if you edit /path/one/foobar.txt and /path/two/foobar.txt, then you will see two swap files in ~/.vim/swap/ that are named %path%one%foobar.txt and %path%two%foobar.txt, respectively.

How can I set a custom date time format in Oracle SQL Developer?

When i copied the date format for timestamp and used that for date, it did not work. But changing the date format to this (DD-MON-YY HH12:MI:SS AM) worked for me.

The change has to be made in Tools->Preferences-> search for NLS

"Proxy server connection failed" in google chrome

Internet explorer has a reset to factory button and luckily so does chrome! try the link below and let us know. the other option is to stop chrome and delete the c:\users\%username%\appdata\local\google folder entirely then reinstall chrome but this will loose all you local settings and data.

Google doc on how to factory reset:

How do I make JavaScript beep?

Using Houshalter's suggestion, I made this simple tone synthesizer demo.


Here is a screenshot. Try the live demo further down in this Answer (click Run code snippet).

screenshot of live demo available further down in this Answer

Demo code

audioCtx = new(window.AudioContext || window.webkitAudioContext)();_x000D_
function show() {_x000D_
  frequency = document.getElementById("fIn").value;_x000D_
  document.getElementById("fOut").innerHTML = frequency + ' Hz';_x000D_
  switch (document.getElementById("tIn").value * 1) {_x000D_
    case 0: type = 'sine'; break;_x000D_
    case 1: type = 'square'; break;_x000D_
    case 2: type = 'sawtooth'; break;_x000D_
    case 3: type = 'triangle'; break;_x000D_
  document.getElementById("tOut").innerHTML = type;_x000D_
  volume = document.getElementById("vIn").value / 100;_x000D_
  document.getElementById("vOut").innerHTML = volume;_x000D_
  duration = document.getElementById("dIn").value;_x000D_
  document.getElementById("dOut").innerHTML = duration + ' ms';_x000D_
function beep() {_x000D_
  var oscillator = audioCtx.createOscillator();_x000D_
  var gainNode = audioCtx.createGain();_x000D_
  gainNode.gain.value = volume;_x000D_
  oscillator.frequency.value = frequency;_x000D_
  oscillator.type = type;_x000D_
    function() {_x000D_
<input type="range" id="fIn" min="40" max="6000" oninput="show()" />_x000D_
<span id="fOut"></span><br>_x000D_
<input type="range" id="tIn" min="0" max="3" oninput="show()" />_x000D_
<span id="tOut"></span><br>_x000D_
<input type="range" id="vIn" min="0" max="100" oninput="show()" />_x000D_
<span id="vOut"></span><br>_x000D_
<input type="range" id="dIn" min="1" max="5000" oninput="show()" />_x000D_
<span id="dOut"></span>_x000D_
<button onclick='beep();'>Play</button>

You can clone and tweak the code here: Tone synthesizer demo on JS Bin

Have fun!

Compatible browsers:

  • Chrome mobile & desktop
  • Firefox mobile & desktop
  • Opera mobile, mini & desktop
  • Android browser
  • Microsoft Edge browser
  • Safari on iPhone or iPad

Not Compatible

  • Internet Explorer version 11 (but does work on the Edge browser)

Mockito: InvalidUseOfMatchersException

Do not use Mockito.anyXXXX(). Directly pass the value to the method parameter of same type. Example:

A expected = new A(10);

String firstId = "10w";
String secondId = "20s";
String product = "Test";
String type = "type2";
Mockito.when(service.getTestData(firstId, secondId, product,type)).thenReturn(expected);

public class A{
   int a ;
   public A(int a) {
      this.a = a;

What is the difference between & and && in Java?

With booleans, there is no output difference between the two. You can swap && and & or || and | and it will never change the result of your expression.

The difference lies behind the scene where the information is being processed. When you right an expression "(a != 0) & ( b != 0)" for a= 0 and b = 1, The following happens:

left side: a != 0 --> false
right side: b 1= 0 --> true
left side and right side are both true? --> false
expression returns false

When you write an expression (a != 0) && ( b != 0) when a= 0 and b = 1, the following happens:

a != 0 -->false
expression returns false

Less steps, less processing, better coding, especially when doing many boolean expression or complicated arguments.

Install tkinter for Python

For Fedora >= 25 and python >= 3, we might need to include the dependencies for Tkinter

sudo dnf install python3-tkinter

I want to delete all bin and obj folders to force all projects to rebuild everything

I found this thread and got bingo. A little more searching turned up this power shell script:

Get-ChildItem .\ -include bin,obj -Recurse | ForEach-Object ($_) { Remove-Item $_.FullName -Force -Recurse }

I thought I'd share, considering that I did not find the answer when I was looking here.

Android - running a method periodically using postDelayed() call

Handler h = new Handler() {
    public void handleMessage(Message msg) {
        if (msg.what==0){
            // do stuff
            h.removeMessages(0);  // clear the handler for those messages with what = 0
            h.sendEmptyMessageDelayed(0, 2000); 


Access cell value of datatable

If you need a weak reference to the cell value:

object field = d.Rows[0][3]


object field = d.Rows[0].ItemArray[3]

Should do it

If you need a strongly typed reference (string in your case) you can use the DataRowExtensions.Field extension method:

string field = d.Rows[0].Field<string>(3);

(make sure System.Data is in listed in the namespaces in this case)

Indexes are 0 based so we first access the first row (0) and then the 4th column in this row (3)

How to tell if node.js is installed or not

Open the command prompt in Windows or terminal in Linux and Mac.Type

node -v

If node is install it will show its version.For eg.,


Else download it from

Can I simultaneously declare and assign a variable in VBA?

There is no shorthand in VBA unfortunately, The closest you will get is a purely visual thing using the : continuation character if you want it on one line for readability;

Dim clientToTest As String:  clientToTest = clientsToTest(i)
Dim clientString As Variant: clientString = Split(clientToTest)

Hint (summary of other answers/comments): Works with objects too (Excel 2010):

Dim ws  As Worksheet: Set ws = ActiveWorkbook.Worksheets("Sheet1")
Dim ws2 As New Worksheet: ws2.Name = "test"

How to open a WPF Popup when another control is clicked, using XAML markup only?

The following uses EventTrigger to show the Popup. This means we don't need a ToggleButton for state binding. In this example the Click event of a Button is used. You can adapt it to use another element/event combination.

<Button x:Name="OpenPopup">Popup
        <EventTrigger RoutedEvent="Button.Click">
                            <DiscreteBooleanKeyFrame KeyTime="0:0:0" Value="True" />
<Popup x:Name="ContextPopup"
       PlacementTarget="{Binding ElementName=OpenPopup}"

Please note that the Popup is referencing the Button by name and vice versa. So x:Name="..." is required on both, the Popup and the Button.

It can actually be further simplified by replacing the Storyboard stuff with a custom SetProperty EventTrigger Action described in this SO Answer

can't multiply sequence by non-int of type 'float'

for i in growthRates:  
    fund = fund * (1 + 0.01 * growthRates) + depositPerYear

should be:

for i in growthRates:  
    fund = fund * (1 + 0.01 * i) + depositPerYear

You are multiplying 0.01 with the growthRates list object. Multiplying a list by an integer is valid (it's overloaded syntactic sugar that allows you to create an extended a list with copies of its element references).


>>> 2 * [1,2]
[1, 2, 1, 2]

Getter and Setter?

class MyClass {
    private $firstField;
    private $secondField;
    private $thirdField;

    public function __get( $name ) {
        if( method_exists( $this , $method = ( 'get' . ucfirst( $name  ) ) ) )
            return $this->$method();
            throw new Exception( 'Can\'t get property ' . $name );

    public function __set( $name , $value ) {
        if( method_exists( $this , $method = ( 'set' . ucfirst( $name  ) ) ) )
            return $this->$method( $value );
            throw new Exception( 'Can\'t set property ' . $name );

    public function __isset( $name )
        return method_exists( $this , 'get' . ucfirst( $name  ) ) 
            || method_exists( $this , 'set' . ucfirst( $name  ) );

    public function getFirstField() {
        return $this->firstField;

    protected function setFirstField($x) {
        $this->firstField = $x;

    private function getSecondField() {
        return $this->secondField;

$obj = new MyClass();

echo $obj->firstField; // works
$obj->firstField = 'value'; // works

echo $obj->getFirstField(); // works
$obj->setFirstField( 'value' ); // not works, method is protected

echo $obj->secondField; // works
echo $obj->getSecondField(); // not works, method is private

$obj->secondField = 'value'; // not works, setter not exists

echo $obj->thirdField; // not works, property not exists

isset( $obj->firstField ); // returns true
isset( $obj->secondField ); // returns true
isset( $obj->thirdField ); // returns false


Wordpress keeps redirecting to install-php after migration

Resolved: wp-config.php setting

I had a similar problem. I got the install.php after moving files and creating a new database. It seems the install screen shows up it there is problem finding the correct database tables.

I fixed the problem by changing the following settings to be correct:

// ** MySQL settings - You can get this info from your web host ** //
/** The name of the database for WordPress */
define('DB_NAME', 'HikeforLife_dev11');

/** MySQL database username */
define('DB_USER', 'HikeforLife_dev11');

$table_prefix  = 'wphk_';

Finding the index of elements based on a condition using python list comprehension

  • In Python, you wouldn't use indexes for this at all, but just deal with the values—[value for value in a if value > 2]. Usually dealing with indexes means you're not doing something the best way.

  • If you do need an API similar to Matlab's, you would use numpy, a package for multidimensional arrays and numerical math in Python which is heavily inspired by Matlab. You would be using a numpy array instead of a list.

    >>> import numpy
    >>> a = numpy.array([1, 2, 3, 1, 2, 3])
    >>> a
    array([1, 2, 3, 1, 2, 3])
    >>> numpy.where(a > 2)
    (array([2, 5]),)
    >>> a > 2
    array([False, False,  True, False, False,  True], dtype=bool)
    >>> a[numpy.where(a > 2)]
    array([3, 3])
    >>> a[a > 2]
    array([3, 3])

Angular Directive refresh on parameter change

What you're trying to do is to monitor the property of attribute in directive. You can watch the property of attribute changes using $observe() as follows:

angular.module('myApp').directive('conversation', function() {
  return {
    restrict: 'E',
    replace: true,
    compile: function(tElement, attr) {
      attr.$observe('typeId', function(data) {
            console.log("Updated data ", data);
      }, true);


Keep in mind that I used the 'compile' function in the directive here because you haven't mentioned if you have any models and whether this is performance sensitive.

If you have models, you need to change the 'compile' function to 'link' or use 'controller' and to monitor the property of a model changes, you should use $watch(), and take of the angular {{}} brackets from the property, example:

<conversation style="height:300px" type="convo" type-id="some_prop"></conversation>

And in the directive:

angular.module('myApp').directive('conversation', function() {
  return {
    scope: {
      typeId: '=',
    link: function(scope, elm, attr) {

      scope.$watch('typeId', function(newValue, oldValue) {
          if (newValue !== oldValue) {
            // You actions here
            console.log("I got the new value! ", newValue);
      }, true);


Is it a good idea to index datetime field in mysql?

Here author performed tests showed that integer unix timestamp is better than DateTime. Note, he used MySql. But I feel no matter what DB engine you use comparing integers are slightly faster than comparing dates so int index is better than DateTime index. Take T1 - time of comparing 2 dates, T2 - time of comparing 2 integers. Search on indexed field takes approximately O(log(rows)) time because index based on some balanced tree - it may be different for different DB engines but anyway Log(rows) is common estimation. (if you not use bitmask or r-tree based index). So difference is (T2-T1)*Log(rows) - may play role if you perform your query oftenly.

How to check if input file is empty in jQuery

Just check the length of files property, which is a FileList object contained on the input element

if( document.getElementById("videoUploadFile").files.length == 0 ){
    console.log("no files selected");

Javascript: How to loop through ALL DOM elements on a page?

Here is another example on how you can loop through a document or an element:

function getNodeList(elem){
var l=new Array(elem),c=1,ret=new Array();
//This first loop will loop until the count var is stable//
for(var r=0;r<c;r++){
    //This loop will loop thru the child element list//
    for(var z=0;z<l[r].childNodes.length;z++){

         //Push the element to the return array.

return ret;

Check if null Boolean is true results in exception

as your variable bool is pointing to a null, you will always get a NullPointerException, you need to initialize the variable first somewhere with a not null value, and then modify it.

Using Java generics for JPA findAll() query with WHERE clause

I found this page very useful

public abstract class GenericDAOWithJPA<T, ID extends Serializable> {

    private Class<T> persistentClass;

    //This you might want to get injected by the container
    protected EntityManager entityManager;

    public GenericDAOWithJPA() {
            this.persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];

    public List<T> findAll() {
            return entityManager.createQuery("Select t from " + persistentClass.getSimpleName() + " t").getResultList();

Get top most UIViewController

For anyone looking for a swift 5/iOS 13+ solution (keywindow is deprecated since iOS 13)

extension UIApplication {

    class func getTopMostViewController() -> UIViewController? {
        let keyWindow = {$0.isKeyWindow}.first
        if var topController = keyWindow?.rootViewController {
            while let presentedViewController = topController.presentedViewController {
                topController = presentedViewController
            return topController
        } else {
            return nil

Find duplicate records in a table using SQL Server

Try this instead

SELECT MAX(shoppername), COUNT(*) AS cnt
FROM dbo.sales

Read about the CHECKSUM function first, as there can be duplicates.

Git remote branch deleted, but still it appears in 'branch -a'


git remote prune origin

From the Git remote documentation:


Deletes all stale remote-tracking branches under <name>. These stale branches have already been removed from the remote repository referenced by <name>, but are still locally available in "remotes/<name>".

With --dry-run option, report what branches will be pruned, but do not actually prune them.

How to parse a JSON object to a TypeScript Object

let employee = <Employee>JSON.parse(employeeString);

Remember: Strong typings is compile time only since javascript doesn't support it.

Xcode swift am/pm time to 24 hour format

let calendar = Calendar.current
let hours    = calendar.component(.hour, from: Date())
let minutes  = calendar.component(.minute, from: Date())
let seconds  = calendar.component(.second, from: Date())

submit the form using ajax

Nobody has actually given a pure javascript answer (as requested by OP), so here it is:

function postAsync(url2get, sendstr)    {
    var req;
    if (window.XMLHttpRequest) {
        req = new XMLHttpRequest();
        } else if (window.ActiveXObject) {
        req = new ActiveXObject("Microsoft.XMLHTTP");
    if (req != undefined) {
        // req.overrideMimeType("application/json"); // if request result is JSON
        try {
  "POST", url2get, false); // 3rd param is whether "async"
        catch(err) {
            alert("couldnt complete request. Is JS enabled for that domain?\\n\\n" + err.message);
            return false;
        req.send(sendstr); // param string only used for POST

        if (req.readyState == 4) { // only if req is "loaded"
            if (req.status == 200)  // only if "OK"
                { return req.responseText ; }
            else    { return "XHR error: " + req.status +" "+req.statusText; }
    alert("req for getAsync is undefined");

var var_str = "var1=" + var1  + "&var2=" + var2;
var ret = postAsync(url, var_str) ;
    // hint: encodeURIComponent()

if (ret.match(/^XHR error/)) {

In your case:

var var_str = "video_time=" + document.getElementById('video_time').value 
     + "&video_id=" + document.getElementById('video_id').value;

Getting the error "Java.lang.IllegalStateException Activity has been destroyed" when using tabs with ViewPager

This one drove me crazy for Xamarin.

I ran into this with a ViewPager implementation for TabLayout WITHIN a Fragment, that is itself implemented in the DrawerLayout:

 - DrawerLayout
   - DrawerFragment
     - TabLayout
     - TabViewPager
       - TabViewPagerFragments

So you have to implement the following code in your DrawerFragment. Be aware to choose the correct FragmentManager-Path. Because you might have two different FragmentManager References:

  1. Android.Support.V4.App.FragmentManager
  2. Android.App.FragmentManager

--> Choose the one you use. If you want to make use of the ChildFragmentManager, you had to use the class declaration Android.App.FragmentManager for your ViewPager!


Implement the following Method in your "Main" Fragment - in this example: DrawerFragment

public override void OnDetach() {
    try {
        Fragment x = this;
        var classRefProp = typeof(Fragment).GetProperty("class_ref", BindingFlags.NonPublic | BindingFlags.Static);
        IntPtr classRef = (IntPtr)classRefProp.GetValue(x);
        var field = JNIEnv.GetFieldID(classRef, "mChildFragmentManager", "Landroid/support/v4/app/FragmentManagerImpl;");
        JNIEnv.SetField(base.Handle, field, IntPtr.Zero);
    catch (Exception e) {
        Log.Debug("Error", e+"");


public class TabViewPager: Android.Support.V13.App.FragmentPagerAdapter {}

That means you had to init the ViewPager with Android.App.FragmentManager.

Implement the following Method in your "Main" Fragment - in this example: DrawerFragment

public override void OnDetach() {
    try {
        Fragment x = this;
        var classRefProp = typeof(Fragment).GetProperty("class_ref", BindingFlags.NonPublic | BindingFlags.Static);
        IntPtr classRef = (IntPtr)classRefProp.GetValue(x);
        var field = JNIEnv.GetFieldID(classRef, "mChildFragmentManager", "Landroid/app/FragmentManagerImpl;");
        JNIEnv.SetField(base.Handle, field, IntPtr.Zero);
    catch (Exception e) {
        Log.Debug("Error", e+"");

How to display a list of images in a ListView in Android?

File name should match the layout id which in this example is : items_list_item.xml in the layout folder of your application

<LinearLayout xmlns:android=""

<ImageView android:id="@+id/"
  android:layout_height="wrap_content" />  

How to subtract days from a plain Date?

When setting the date, the date converts to milliseconds, so you need to convert it back to a date:

This method also take into consideration, new year change etc.

function addDays( date, days ) {
    var dateInMs = date.setDate(date.getDate() - days);
    return new Date(dateInMs);

var date_from = new Date();
var date_to = addDays( new Date(), parseInt(days) );

jQuery SVG, why can't I addClass?

jQuery does not support the classes of SVG elements. You can get the element directly $(el).get(0) and use classList and add / remove. There is a trick with this too in that the topmost SVG element is actually a normal DOM object and can be used like every other element in jQuery. In my project I created this to take care of what I needed but the documentation provided on the Mozilla Developer Network has a shim that can be used as an alternative.


function addRemoveClass(jqEl, className, addOrRemove) 
  var classAttr = jqEl.attr('class');
  if (!addOrRemove) {
    classAttr = classAttr.replace(new RegExp('\\s?' + className), '');
    jqEl.attr('class', classAttr);
  } else {
    classAttr = classAttr + (classAttr.length === 0 ? '' : ' ') + className;
    jqEl.attr('class', classAttr);

An alternative all tougher is to use D3.js as your selector engine instead. My projects have charts that are built with it so it's also in my app scope. D3 correctly modifies the class attributes of vanilla DOM elements and SVG elements. Though adding D3 for just this case would likely be overkill.'myclass', true);

Setting the height of a DIV dynamically

If I understand what you're asking, this should do the trick:

// the more standards compliant browsers (mozilla/netscape/opera/IE7) use 
// window.innerWidth and window.innerHeight

var windowHeight;

if (typeof window.innerWidth != 'undefined')
    windowHeight = window.innerHeight;
// IE6 in standards compliant mode (i.e. with a valid doctype as the first 
// line in the document)
else if (typeof document.documentElement != 'undefined'
        && typeof document.documentElement.clientWidth != 'undefined' 
        && document.documentElement.clientWidth != 0)
    windowHeight = document.documentElement.clientHeight;
// older versions of IE
    windowHeight = document.getElementsByTagName('body')[0].clientHeight;

document.getElementById("yourDiv").height = windowHeight - 300 + "px";

Naming convention - underscore in C++ and C# variables

A naming convention like this is useful when you are reading code, particularly code that is not your own. A strong naming convention helps indicate where a particular member is defined, what kind of member it is, etc. Most development teams adopt a simple naming convention, and simply prefix member fields with an underscore (_fieldName). In the past, I have used the following naming convention for C# (which is based on Microsofts conventions for the .NET framework code, which can be seen with Reflector):

Instance Field: m_fieldName
Static Field: s_fieldName
Public/Protected/Internal Member: PascalCasedName()
Private Member: camelCasedName()

This helps people understand the structure, use, accessibility and location of members when reading unfamiliar code very rapidly.

What is for?

In Python the definition of package is very simple. Like Java the hierarchical structure and the directory structure are the same. But you have to have in a package. I will explain the file with the example below:

|--    subPackage_a/
|--    subPackage_b/
|------ can be empty, as long as it exists. It indicates that the directory should be regarded as a package. Of course, can also set the appropriate content.

If we add a function in module_n1:

def function_X():
    print "function_X in module_n1"

After running:

>>>from package_x.subPackage_b.module_n1 import function_X

function_X in module_n1 

Then we followed the hierarchy package and called module_n1 the function. We can use in subPackage_b like this:

__all__ = ['module_n2', 'module_n3']

After running:

>>>from package_x.subPackage_b import * 

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named module_n1

Hence using * importing, module package is subject to content.

What is the difference between response.sendRedirect() and request.getRequestDispatcher().forward(request,response)


Control can be forward to resources available within the server from where the call is made. This transfer of control is done by the container internally and browser / client is not involved. This is the major difference between forward and sendRedirect. When the forward is done, the original request and response objects are transfered along with additional parameters if needed.


Control can be redirect to resources to different servers or domains. This transfer of control task is delegated to the browser by the container. That is, the redirect sends a header back to the browser / client. This header contains the resource url to be redirected by the browser. Then the browser initiates a new request to the given url. Since it is a new request, the old request and response object is lost.

For example, sendRedirect can transfer control from to but forward cannot do this.

‘session’ is not lost in both forward and redirect.

To feel the difference between forward and sendRedirect visually see the address bar of your browser, in forward, you will not see the forwarded address (since the browser is not involved) in redirect, you can see the redirected address.

Unbound classpath container in Eclipse

I had a similar problem when I recreated my workspace that was fixed in the following way:

Go to Eclipse -> Preferences, under Java select "Installed JREs" and check one of the boxes to specify a default JRE. Click OK and then go back to your project's properties. Go to the "Java Build Path" section and choose the "Libraries" tab. Remove the unbound System Default library, then click the "Add Library" button. Select "JRE System Library" and you should be good to go!

Gradle build without tests

Using -x test skip test execution but this also exclude test code compilation.

gradle build -x test 

In our case, we have a CI/CD process where one goal is compilation and next goal is testing (Build -> Test).

So, for our first Build goal we wanted to ensure that the whole project compiles well. For this we have used:

./gradlew build testClasses -x test

On the next goal we simply execute tests.

Select row and element in awk

Since awk and perl are closely related...

Perl equivalents of @Dennis's awk solutions:

To print the second line:
perl -ne 'print if $. == 2' file

To print the second field:
perl -lane 'print $F[1]' file

To print the third field of the fifth line:
perl -lane 'print $F[2] if $. == 5' file

Perl equivalent of @Glenn's solution:

Print the j'th field of the i'th line

perl -lanse 'print $F[$j-1] if $. == $i' -- -i=5 -j=3 file

Perl equivalents of @Hai's solutions:

if you are looking for second columns that contains abc:

perl -lane 'print if $F[1] =~ /abc/' foo

... and if you want to print only a particular column:

perl -lane 'print $F[2] if $F[1] =~ /abc/' foo

... and for a particular line number:

perl -lane 'print $F[2] if $F[1] =~ /abc/ && $. == 5' foo

-l removes newlines, and adds them back in when printing
-a autosplits the input line into array @F, using whitespace as the delimiter
-n loop over each line of the input file
-e execute the code within quotes
$F[1] is the second element of the array, since Perl starts at 0
$. is the line number

Rails: Using greater than/less than with a where statement

A better usage is to create a scope in the user model where(arel_table[:id].gt(id))

How to uncheck a radio button?

Thanks Patrick, you made my day! It's mousedown you have to use. However I've improved the code so you can handle a group of radio buttons.

//We need to bind click handler as well
//as FF sets button checked after mousedown, but before click
$('input:radio').bind('click mousedown', (function() {
    //Capture radio button status within its handler scope,
    //so we do not use any global vars and every radio button keeps its own status.
    //This required to uncheck them later.
    //We need to store status separately as browser updates checked status before click handler called,
    //so radio button will always be checked.
    var isChecked;

    return function(event) {
        //console.log(event.type + ": " + this.checked);

        if(event.type == 'click') {

            if(isChecked) {
                //Uncheck and update status
                isChecked = this.checked = false;
            } else {
                //Update status
                //Browser will check the button by itself
                isChecked = true;

                //Do something else if radio button selected
                if(this.value == 'somevalue') {
                } else {
    } else {
        //Get the right status before browser sets it
        //We need to use onmousedown event here, as it is the only cross-browser compatible event for radio buttons
        isChecked = this.checked;

JavaFX "Location is required." even though it is in the same package

The root directory for the loader is in the 'resources' folder for a maven project. So if you have src/main/java then the fxml file path should start from: src/main/resources

How to set OnClickListener on a RadioButton in Android?

Just in case someone else was struggeling with the accepted answer:

There are different OnCheckedChangeListener-Interfaces. I added to first one to see if a CheckBox was changed.

import android.widget.CompoundButton.OnCheckedChangeListener;


import android.widget.RadioGroup.OnCheckedChangeListener;

When adding the snippet from Ricky I had errors:

The method setOnCheckedChangeListener(RadioGroup.OnCheckedChangeListener) in the type RadioGroup is not applicable for the arguments (new CompoundButton.OnCheckedChangeListener(){})

Can be fixed with answer from Ali :

new RadioGroup.OnCheckedChangeListener()

div background color, to change onhover

Just make the property !important in your css file so that background color doesnot change on mouse over.This worked for me.


.fbColor {
    background-color: #3b5998 !important;
    color: white;

How to include a class in PHP

I suggest you also take a look at __autoload.
This will clean up the code of requires and includes.

Filter element based on .data() key/value

Just for the record, you can filter on data with jquery (this question is quite old, and jQuery evolved since then, so it's right to write this solution as well):


or, better (for performance):


or, if you want to get all the elements with data-selected set:


Note that this method will only work with data that was set via html-attributes. If you set or change data with the .data() call, this method will no longer work.

How do you round a float to 2 decimal places in JRuby?

Float#round can take a parameter in Ruby 1.9, not in Ruby 1.8. JRuby defaults to 1.8, but it is capable of running in 1.9 mode.

AngularJS error: 'argument 'FirstCtrl' is not a function, got undefined'

You have 2 unnamed ng-app directives in your html.
Lose the one in your div.

Let's try a different approach.
Define a module in your js file and assign the ng-appdirective to it. After that, define the controller like an ng component, not as a simple function:

<div ng-app="myAppName">  
<!-- or what's the root node of your angular app -->

and the js part:

angular.module('myAppName', [])
    .controller('FirstCtrl', function($scope) {
         $ = {message: 'Hello'};

Here's an online demo that is doing just that :

Convert `List<string>` to comma-separated string

In .NET 4 you don't need the ToArray() call - string.Join is overloaded to accept IEnumerable<T> or just IEnumerable<string>.

There are potentially more efficient ways of doing it before .NET 4, but do you really need them? Is this actually a bottleneck in your code?

You could iterate over the list, work out the final size, allocate a StringBuilder of exactly the right size, then do the join yourself. That would avoid the extra array being built for little reason - but it wouldn't save much time and it would be a lot more code.

What are the pros and cons of parquet format compared to other formats?

I think the main difference I can describe relates to record oriented vs. column oriented formats. Record oriented formats are what we're all used to -- text files, delimited formats like CSV, TSV. AVRO is slightly cooler than those because it can change schema over time, e.g. adding or removing columns from a record. Other tricks of various formats (especially including compression) involve whether a format can be split -- that is, can you read a block of records from anywhere in the dataset and still know it's schema? But here's more detail on columnar formats like Parquet.

Parquet, and other columnar formats handle a common Hadoop situation very efficiently. It is common to have tables (datasets) having many more columns than you would expect in a well-designed relational database -- a hundred or two hundred columns is not unusual. This is so because we often use Hadoop as a place to denormalize data from relational formats -- yes, you get lots of repeated values and many tables all flattened into a single one. But it becomes much easier to query since all the joins are worked out. There are other advantages such as retaining state-in-time data. So anyway it's common to have a boatload of columns in a table.

Let's say there are 132 columns, and some of them are really long text fields, each different column one following the other and use up maybe 10K per record.

While querying these tables is easy with SQL standpoint, it's common that you'll want to get some range of records based on only a few of those hundred-plus columns. For example, you might want all of the records in February and March for customers with sales > $500.

To do this in a row format the query would need to scan every record of the dataset. Read the first row, parse the record into fields (columns) and get the date and sales columns, include it in your result if it satisfies the condition. Repeat. If you have 10 years (120 months) of history, you're reading every single record just to find 2 of those months. Of course this is a great opportunity to use a partition on year and month, but even so, you're reading and parsing 10K of each record/row for those two months just to find whether the customer's sales are > $500.

In a columnar format, each column (field) of a record is stored with others of its kind, spread all over many different blocks on the disk -- columns for year together, columns for month together, columns for customer employee handbook (or other long text), and all the others that make those records so huge all in their own separate place on the disk, and of course columns for sales together. Well heck, date and months are numbers, and so are sales -- they are just a few bytes. Wouldn't it be great if we only had to read a few bytes for each record to determine which records matched our query? Columnar storage to the rescue!

Even without partitions, scanning the small fields needed to satisfy our query is super-fast -- they are all in order by record, and all the same size, so the disk seeks over much less data checking for included records. No need to read through that employee handbook and other long text fields -- just ignore them. So, by grouping columns with each other, instead of rows, you can almost always scan less data. Win!

But wait, it gets better. If your query only needed to know those values and a few more (let's say 10 of the 132 columns) and didn't care about that employee handbook column, once it had picked the right records to return, it would now only have to go back to the 10 columns it needed to render the results, ignoring the other 122 of the 132 in our dataset. Again, we skip a lot of reading.

(Note: for this reason, columnar formats are a lousy choice when doing straight transformations, for example, if you're joining all of two tables into one big(ger) result set that you're saving as a new table, the sources are going to get scanned completely anyway, so there's not a lot of benefit in read performance, and because columnar formats need to remember more about the where stuff is, they use more memory than a similar row format).

One more benefit of columnar: data is spread around. To get a single record, you can have 132 workers each read (and write) data from/to 132 different places on 132 blocks of data. Yay for parallelization!

And now for the clincher: compression algorithms work much better when it can find repeating patterns. You could compress AABBBBBBCCCCCCCCCCCCCCCC as 2A6B16C but ABCABCBCBCBCCCCCCCCCCCCCC wouldn't get as small (well, actually, in this case it would, but trust me :-) ). So once again, less reading. And writing too.

So we read a lot less data to answer common queries, it's potentially faster to read and write in parallel, and compression tends to work much better.

Columnar is great when your input side is large, and your output is a filtered subset: from big to little is great. Not as beneficial when the input and outputs are about the same.

But in our case, Impala took our old Hive queries that ran in 5, 10, 20 or 30 minutes, and finished most in a few seconds or a minute.

Hope this helps answer at least part of your question!

Convert string to date in Swift

Swift 5. To see IF A DATE HAS PASSED:

let expiryDate = "2020-01-10" // Jan 10 2020

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"

if Date() < expiryDate) ?? Date() {
    print("Not Yet expiryDate")
} else {
    print("expiryDate has passed")

Error : Index was outside the bounds of the array.

You have declared an array that can store 8 elements not 9.

this.posStatus = new int[8]; 

It means postStatus will contain 8 elements from index 0 to 7.

Reimport a module in python while interactive

Although the provided answers do work for a specific module, they won't reload submodules, as noted in This answer:

If a module imports objects from another module using from ... import ..., calling reload() for the other module does not redefine the objects imported from it — one way around this is to re-execute the from statement, another is to use import and qualified names (module.*name*) instead.

However, if using the __all__ variable to define the public API, it is possible to automatically reload all publicly available modules:

# Python >= 3.5
import importlib
import types

def walk_reload(module: types.ModuleType) -> None:
    if hasattr(module, "__all__"):
        for submodule_name in module.__all__:
            walk_reload(getattr(module, submodule_name))


The caveats noted in the previous answer are still valid though. Notably, modifying a submodule that is not part of the public API as described by the __all__ variable won't be affected by a reload using this function. Similarly, removing an element of a submodule won't be reflected by a reload.

How to synchronize or lock upon variables in Java?

From Java 1.5 it's always a good Idea to consider java.util.concurrent package. They are the state of the art locking mechanism in java right now. The synchronize mechanism is more heavyweight that the java.util.concurrent classes.

The example would look something like this:

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Sample {

    private final Lock lock = new ReentrantLock();

    private String message = null;

    public void newmsg(String msg) {
        try {
            message = msg;
        } finally {

    public String getmsg() {
        try {
            String temp = message;
            message = null;
            return temp;
        } finally {