Programs & Examples On #Attributeerror

The Python `AttributeError` exception.

Why does this AttributeError in python occur?

This happens because the scipy module doesn't have any attribute named sparse. That attribute only gets defined when you import scipy.sparse.

Submodules don't automatically get imported when you just import scipy; you need to import them explicitly. The same holds for most packages, although a package can choose to import its own submodules if it wants to. (For example, if scipy/ included a statement import scipy.sparse, then the sparse submodule would be imported whenever you import scipy.)

Why Python 3.6.1 throws AttributeError: module 'enum' has no attribute 'IntFlag'?

It's because your enum is not the standard library enum module. You probably have the package enum34 installed.

One way check if this is the case is to inspect the property enum.__file__

import enum
# standard library location should be something like 
# /usr/local/lib/python3.6/

Since python 3.6 the enum34 library is no longer compatible with the standard library. The library is also unnecessary, so you can simply uninstall it.

pip uninstall -y enum34

If you need the code to run on python versions both <=3.4 and >3.4, you can try having enum-compat as a requirement. It only installs enum34 for older versions of python without the standard library enum.

Why do I get AttributeError: 'NoneType' object has no attribute 'something'?

NoneType means that instead of an instance of whatever Class or Object you think you're working with, you've actually got None. That usually means that an assignment or function call up above failed or returned an unexpected result.

Beginner Python: AttributeError: 'list' object has no attribute

You need to pass the values of the dict into the Bike constructor before using like that. Or, see the namedtuple -- seems more in line with what you're trying to do.

AttributeError("'str' object has no attribute 'read'")

You need to open the file first. This doesn't work:

json_file = json.load('test.json')

But this works:

f = open('test.json')
json_file = json.load(f)

"import datetime" v.s. "from datetime import datetime"

You cannot use both statements; the datetime module contains a datetime type. The local name datetime in your own module can only refer to one or the other.

Use only import datetime, then make sure that you always use datetime.datetime to refer to the contained type:

import datetime

today_date =
date_time = datetime.datetime.strptime(date_time_string, '%Y-%m-%d %H:%M')

Now datetime is the module, and you refer to the contained types via that.

Alternatively, import all types you need from the module:

from datetime import date, datetime

today_date =
date_time = datetime.strptime(date_time_string, '%Y-%m-%d %H:%M')

Here datetime is the type from the module. date is another type, from the same module.

AttributeError: 'module' object has no attribute 'urlretrieve'

As you're using Python 3, there is no urllib module anymore. It has been split into several modules.

This would be equivalent to urlretrieve:

import urllib.request
data = urllib.request.urlretrieve("http://...")

urlretrieve behaves exactly the same way as it did in Python 2.x, so it'll work just fine.


  • urlretrieve saves the file to a temporary file and returns a tuple (filename, headers)
  • urlopen returns a Request object whose read method returns a bytestring containing the file contents

Python: instance has no attribute

Your class doesn't have a __init__(), so by the time it's instantiated, the attribute atoms is not present. You'd have to do C.setdata('something') so C.atoms becomes available.

>>> C = Residues()
>>> C.atoms.append('thing')

Traceback (most recent call last):
  File "<pyshell#84>", line 1, in <module>
AttributeError: Residues instance has no attribute 'atoms'

>>> C.setdata('something')
>>> C.atoms.append('thing')   # now it works

Unlike in languages like Java, where you know at compile time what attributes/member variables an object will have, in Python you can dynamically add attributes at runtime. This also implies instances of the same class can have different attributes.

To ensure you'll always have (unless you mess with it down the line, then it's your own fault) an atoms list you could add a constructor:

def __init__(self):
    self.atoms = []

AttributeError: 'module' object has no attribute

Circular imports cause problems, but Python has ways to mitigate it built-in.

The problem is when you run python, it runs but not mark it imported as a module. So in turn -> imports module b -> imports module a -> imports module b. The last import a no-op since b is currently being imported and Python guards against that. And b is an empty module for now. So when it executes b.hi(), it can't find anything.

Note that the b.hi() that got executed is during -> module b -> module a, not in directly.

In your specific example, you can just run python -c 'import a' at top-level, so the first execution of is registered as importing a module.

AttributeError: 'DataFrame' object has no attribute

To get all the counts for all the columns in a dataframe, it's just df.count()

AttributeError: 'str' object has no attribute

The problem is in your playerMovement method. You are creating the string name of your room variables (ID1, ID2, ID3):

letsago = "ID" + str(self.dirDesc.values())

However, what you create is just a str. It is not the variable. Plus, I do not think it is doing what you think its doing:


If you REALLY needed to find the variable this way, you could use the eval function:

>>>foo = 'Hello World!'
'Hello World!'

or the globals function:

class Foo(object):
    def __init__(self):
        super(Foo, self).__init__()
    def test(self, name):

foo = Foo()
bar = 'Hello World!'

However, instead I would strongly recommend you rethink you class(es). Your userInterface class is essentially a Room. It shouldn't handle player movement. This should be within another class, maybe GameManager or something like that.

How can I select checkboxes using the Selenium Java WebDriver?

I tried with various approaches, but nothing worked. I kept getting "Cannot click element" or ElementNotVisibleException.

I was able to find the input, but I couldn't check it. Now, I'm clicking on the div that contains the checkbox and it works with following HTML (CSS based on Bootstrap).

 @foreach (var item in Model)
             <div id="@item.Id" class="checkbox">
                 <label><input type="checkbox" class="selectone" value="@item.Id"></label>
         <td val="@item.Id">
             @Html.ActionLink("Edit", "Create", new { EditId = item.Id })

This is the code for WebDriver:

var table = driver.FindElement(By.TagName("table"));
var tds = table.FindElements(By.TagName("td"));
var itemTds = tds.Where(t => t.Text == itemtocheck);
foreach (var td in itemTds)
    var CheckBoxTd = tds[tds.IndexOf(td) - 1];
    var val = td.GetAttribute("val");

In this approach, I give the item id as id for the div and also add an attribute for td with that id. Once I find the td of the item that needs to be checked, I can find the div before that td and click it. We can also use the XPath query that supports before (here is the example

Array of char* should end at '\0' or "\0"?

Null termination is a bad design pattern best left in the history books. There's still plenty of inertia behind c-strings, so it can't be avoided there. But there's no reason to use it in the OP's example.

Don't use any terminator, and use sizeof(array) / sizeof(array[0]) to get the number of elements.

Difference between decimal, float and double in .NET?

  • float: ±1.5 x 10^-45 to ±3.4 x 10^38 (~7 significant figures
  • double: ±5.0 x 10^-324 to ±1.7 x 10^308 (15-16 significant figures)
  • decimal: ±1.0 x 10^-28 to ±7.9 x 10^28 (28-29 significant figures)

Angular 2 / 4 / 5 - Set base href dynamically

I use the current working directory ./ when building several apps off the same domain:

<base href="./">

On a side note, I use .htaccess to assist with my routing on page reload:

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .* index.html [L]

How to add hours to current time in python

from datetime import datetime, timedelta

nine_hours_from_now = + timedelta(hours=9)
#datetime.datetime(2012, 12, 3, 23, 24, 31, 774118)

And then use string formatting to get the relevant pieces:

>>> '{:%H:%M:%S}'.format(nine_hours_from_now)

If you're only formatting the datetime then you can use:

>>> format(nine_hours_from_now, '%H:%M:%S')

Or, as @eumiro has pointed out in comments - strftime

How to hide output of subprocess in Python 2.7

Here's a more portable version (just for fun, it is not necessary in your case):

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from subprocess import Popen, PIPE, STDOUT

    from subprocess import DEVNULL # py3k
except ImportError:
    import os
    DEVNULL = open(os.devnull, 'wb')

text = u"René Descartes"
p = Popen(['espeak', '-b', '1'], stdin=PIPE, stdout=DEVNULL, stderr=STDOUT)
assert p.returncode == 0 # use appropriate for your program error handling here

What is the difference between :focus and :active?

Using "focus" will give keyboard users the same effect that mouse users get when they hover with a mouse. "Active" is needed to get the same effect in Internet Explorer.

The reality is, these states do not work as they should for all users. Not using all three selectors creates accessibility issues for many keyboard-only users who are physically unable to use a mouse. I invite you to take the #nomouse challenge (nomouse dot org).

Return a value of '1' a referenced cell is empty

You can use:


but you should be careful what you mean by empty cell. I've been caught out by this before. If you want to know if a cell is truly blank, isblank, as above, will work. Unfortunately, you sometimes also need to know if it just contains no useful data.

The expression:


will return true for cells that are either truly blank, or contain nothing but white space.

Here's the results when column A contains varying amounts of spaces, column B contains the length (so you know how many spaces) and column C contains the result of the above expression:

<-A-> <-B-> <-C->
        0   TRUE
        1   TRUE
        2   TRUE
        3   TRUE
        4   TRUE
        5   TRUE
  a     1   FALSE
<-A-> <-B-> <-C->

To return 1 if the cell is blank or white space and 0 otherwise:


will do the trick.

This trick comes in handy when the cell that you're checking is actually the result of an Excel function. Many Excel functions (such as trim) will return an empty string rather than a blank cell.

You can see this in action with a new sheet. Leave cell A1 as-is and set A2 to =trim(a1).

Then set B1 to =isblank(a1) and B2 to isblank(a2). You'll see that the former is true while the latter is false.

MaxLength Attribute not generating client-side validation attributes

MaxLengthAttribute is working since MVC 5.1 update: change notes

Create a SQL query to retrieve most recent records

another way, this will scan the table only once instead of twice if you use a subquery

only sql server 2005 and up

select Date, User, Status, Notes 
from (
       select m.*, row_number() over (partition by user order by Date desc) as rn
       from [SOMETABLE] m
     ) m2
where m2.rn = 1;

Split list into smaller lists (split in half)

This is similar to other solutions, but a little faster.

# Usage: split_half([1,2,3,4,5]) Result: ([1, 2], [3, 4, 5])

def split_half(a):
    half = len(a) >> 1
    return a[:half], a[half:]

How to print a list with integers without the brackets, commas and no quotes?

If you're using Python 3, or appropriate Python 2.x version with from __future__ import print_function then:

data = [7, 7, 7, 7]
print(*data, sep='')

Otherwise, you'll need to convert to string and print:

print ''.join(map(str, data))

How to fix Uncaught InvalidValueError: setPosition: not a LatLng or LatLngLiteral: in property lat: not a number?

Using angular-google-maps

$scope.bounds = new google.maps.LatLngBounds();
for (var i = $scope.markers.length - 1; i >= 0; i--) {
    $scope.bounds.extend(new google.maps.LatLng($scope.markers[i].coords.latitude, $scope.markers[i].coords.longitude));

Importing Excel into a DataTable Quickly

MS Office Interop is slow and even Microsoft does not recommend Interop usage on server side and cannot be use to import large Excel files. For more details see why not to use OLE Automation from Microsoft point of view.

Instead, you can use any Excel library, like EasyXLS for example. This is a code sample that shows how to read the Excel file:

ExcelDocument workbook = new ExcelDocument();
DataSet ds = workbook.easy_ReadXLSActiveSheet_AsDataSet("excel.xls");
DataTable dataTable = ds.Tables[0];

If your Excel file has multiple sheets or for importing only ranges of cells (for better performances) take a look to more code samples on how to import Excel to DataTable in C# using EasyXLS.

"Could not find bundler" error

According to this answer to a similar question, it should be enough:

rvmsudo gem install bundler.


Strip HTML from Text JavaScript

myString.replace(/<[^>]*>?/gm, '');

How can I disable mod_security in .htaccess file?

On some servers and web hosts, it's possible to disable ModSecurity via .htaccess, but be aware that you can only switch it on or off, you can't disable individual rules.

But a good practice that still keeps your site secure is to disable it only on specific URLs, rather than your entire site. You can specify which URLs to match via the regex in the <If> statement below...

### DISABLE mod_security firewall
### Some rules are currently too strict and are blocking legitimate users
### We only disable it for URLs that contain the regex below
### The regex below should be placed between "m#" and "#" 
### (this syntax is required when the string contains forward slashes)
<IfModule mod_security.c>
  <If "%{REQUEST_URI} =~ m#/admin/#">
    SecFilterEngine Off
    SecFilterScanPOST Off

Android: Create a toggle button with image and no text

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

    android:textSize="0dp" />

The result compared to regular ToggleButton looks like

enter image description here

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

You create a plain ToggleButton

    android:checked="false" />

Then set the "text" programmatially

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

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

enter image description here

I want to get the type of a variable at runtime

I think the question is incomplete. if you meant that you wish to get the type information of some typeclass then below:

If you wish to print as you have specified then:

scala>  def manOf[T: Manifest](t: T): Manifest[T] = manifest[T]
manOf: [T](t: T)(implicit evidence$1: Manifest[T])Manifest[T]

scala> val x = List(1,2,3)
x: List[Int] = List(1, 2, 3)

scala> println(manOf(x))

If you are in repl mode then

scala> :type List(1,2,3)

Or if you just wish to know what the class type then as @monkjack explains "string".getClass might solve the purpose

Bootstrap : TypeError: $(...).modal is not a function

Use this. It will work. I have used bootstrap 3.3.5 and jquery 1.11.3

$('document').ready(function() {_x000D_
  $('#btnTest').click(function() {_x000D_
body {_x000D_
  background-color: #eee;_x000D_
  padding-top: 40px;_x000D_
  padding-bottom: 40px;_x000D_
<!DOCTYPE html>_x000D_
  <meta charset="utf8">_x000D_
  <meta http-equiv="X-UA-Compatible" content="IE=edge">_x000D_
  <meta name="viewport" content="width=device-width,initial-scale=1">_x000D_
  <link rel="stylesheet" type="text/css" href="">_x000D_
  <title>Modal Test</title>_x000D_
  <div class="container">_x000D_
    <button id="btnTest" class="btn btn-default">Show Modal</button>_x000D_
    <div id="dummyModal" role="dialog" class="modal fade">_x000D_
      <div class="modal-dialog">_x000D_
        <div class="modal-content">_x000D_
          <div class="modal-header">_x000D_
            <button type="button" data-dismiss="modal" class="close">&times;</button>_x000D_
            <h4 class="modal-title">Error</h4>_x000D_
          <div class="modal-body">_x000D_
            <p>Quick Brown Fox Jumps Over The Lazy Dog</p>_x000D_
          <div class="modal-footer">_x000D_
            <button type="button" data-dismiss="modal" class="btn btn-default">Close</button>_x000D_
  <script type="text/javascript" src=""></script>_x000D_
  <script type="text/javascript" src=""></script>_x000D_

PHP $_SERVER['HTTP_HOST'] vs. $_SERVER['SERVER_NAME'], am I understanding the man pages correctly?

Is it "safe" to use $_SERVER['HTTP_HOST'] for all links on a site without having to worry about XSS attacks, even when used in forms?

Yes, it's safe to use $_SERVER['HTTP_HOST'], (and even $_GET and $_POST) as long as you verify them before accepting them. This is what I do for secure production servers:

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
$reject_request = true;
if(array_key_exists('HTTP_HOST', $_SERVER)){
    $host_name = $_SERVER['HTTP_HOST'];
    // [ need to cater for `host:port` since some "buggy" SAPI(s) have been known to return the port too, see
    $strpos = strpos($host_name, ':');
    if($strpos !== false){
        $host_name = substr($host_name, $strpos);
    // ]
    // [ for dynamic verification, replace this chunk with db/file/curl queries
    $reject_request = !array_key_exists($host_name, array(
        '' => null,
        '' => null,
        '' => null,
        '' => null
    // ]
    // log errors
    // display errors (optional)
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
echo 'Hello World!';
// ...

The advantage of $_SERVER['HTTP_HOST'] is that its behavior is more well-defined than $_SERVER['SERVER_NAME']. Contrast ??:

Contents of the Host: header from the current request, if there is one.


The name of the server host under which the current script is executing.

Using a better defined interface like $_SERVER['HTTP_HOST'] means that more SAPIs will implement it using reliable well-defined behavior. (Unlike the other.) However, it is still totally SAPI dependent ??:

There is no guarantee that every web server will provide any of these [$_SERVER entries]; servers may omit some, or provide others not listed here.

To understand how to properly retrieve the host name, first and foremost you need to understand that a server which contains only code has no means of knowing (pre-requisite for verifying) its own name on the network. It needs to interface with a component that supplies it its own name. This can be done via:

  • local config file

  • local database

  • hardcoded source code

  • external request (curl)

  • client/attacker's Host: request

  • etc

Usually its done via the local (SAPI) config file. Note that you have configured it correctly, e.g. in Apache ??:

A couple of things need to be 'faked' to make the dynamic virtual host look like a normal one.

The most important is the server name which is used by Apache to generate self-referential URLs, etc. It is configured with the ServerName directive, and it is available to CGIs via the SERVER_NAME environment variable.

The actual value used at run time is controlled by the UseCanonicalName setting.

With UseCanonicalName Off the server name comes from the contents of the Host: header in the request. With UseCanonicalName DNS it comes from a reverse DNS lookup of the virtual host's IP address. The former setting is used for name-based dynamic virtual hosting, and the latter is used for** IP-based hosting.

If Apache cannot work out the server name because there is no Host: header or the DNS lookup fails then the value configured with ServerName is used instead.

How do I make an auto increment integer field in Django?

You can create an autofield. Here is the documentation for the same

Please remember Django won't allow to have more than one AutoField in a model, In your model you already have one for your primary key (which is default). So you'll have to override model's save method and will probably fetch the last inserted record from the table and accordingly increment the counter and add the new record.

Please make that code thread safe because in case of multiple requests you might end up trying to insert same value for different new records.

Using a PHP variable in a text input value = statement


You are missing an echo. Each time that you want to show the value of a variable to HTML you need to echo it.

<input type="text" name="idtest" value="<?php echo $idtest; ?>" >

Note: Depending on the value, your echo is the function you use to escape it like htmlspecialchars.

Can you style html form buttons with css?

You can directly create your own style in this way:

//Change the style as you like

Cannot apply indexing with [] to an expression of type 'System.Collections.Generic.IEnumerable<>

The []-operator is resolved to the access property this[sometype index], with implementation depending upon the Element-Collection.

An Enumerable-Interface declares a blueprint of what a Collection should look like in the first place.

Take this example to demonstrate the usefulness of clean Interface separation:

var ienu = "13;37".Split(';').Select(int.Parse);
//provides an WhereSelectArrayIterator
var inta = "13;37".Split(';').Select(int.Parse).ToArray()[0];
//inta.GetType(): System.Int32

Also look at the syntax of the []-operator:

public class SomeCollection{
public SomeCollection(){}

 private bool[] bools;

  public bool this[int index] {
     get {
        if ( index < 0 || index >= bools.Length ){
           //... Out of range index Exception
        return bools[index];
     set {
        bools[index] = value;

Eclipse Error: "Failed to connect to remote VM"

If you are using windows os then replace line in tomcat configuration Tomcat6\bin\startup.bat.




call "%EXECUTABLE%" jpda start %CMD_LINE_ARGS%

What is the syntax for an inner join in LINQ to SQL?

basically LINQ join operator provides no benefit for SQL. I.e. the following query

var r = from dealer in db.Dealers
   from contact in db.DealerContact
   where dealer.DealerID == contact.DealerID
   select dealerContact;

will result in INNER JOIN in SQL

join is useful for IEnumerable<> because it is more efficient:

from contact in db.DealerContact  

clause would be re-executed for every dealer But for IQueryable<> it is not the case. Also join is less flexible.

What's the Android ADB shell "dumpsys" tool and what are its benefits?

Looking at the source code for dumpsys and service, you can get the list of services available by executing the following:

adb shell service -l

You can then supply the service name you are interested in to dumpsys to get the specific information. For example (note that not all services provide dump info):

adb shell dumpsys activity
adb shell dumpsys cpuinfo
adb shell dumpsys battery

As you can see in the code (and in K_Anas's answer), if you call dumpsys without any service name, it will dump the info on all services in one big dump:

adb shell dumpsys

Some services can receive additional arguments on what to show which normally is explained if you supplied a -h argument, for example:

adb shell dumpsys activity -h
adb shell dumpsys window -h
adb shell dumpsys meminfo -h
adb shell dumpsys package -h
adb shell dumpsys batteryinfo -h

Python - How to sort a list of lists by the fourth element in each list?

Use sorted() with a key as follows -

>>> unsorted_list = [['a','b','c','5','d'],['e','f','g','3','h'],['i','j','k','4','m']]
>>> sorted(unsorted_list, key = lambda x: int(x[3]))
[['e', 'f', 'g', '3', 'h'], ['i', 'j', 'k', '4', 'm'], ['a', 'b', 'c', '5', 'd']]

The lambda returns the fourth element of each of the inner lists and the sorted function uses that to sort those list. This assumes that int(elem) will not fail for the list.

Or use itemgetter (As Ashwini's comment pointed out, this method would not work if you have string representations of the numbers, since they are bound to fail somewhere for 2+ digit numbers)

>>> from operator import itemgetter
>>> sorted(unsorted_list, key = itemgetter(3))
[['e', 'f', 'g', '3', 'h'], ['i', 'j', 'k', '4', 'm'], ['a', 'b', 'c', '5', 'd']]

PHP - print all properties of an object

for knowing the object properties var_dump(object) is the best way. It will show all public, private and protected properties associated with it without knowing the class name.

But in case of methods, you need to know the class name else i think it's difficult to get all associated methods of the object.

How to detect chrome and safari browser (webkit)

If you dont want to use $.browser, take a look at case 1, otherwise maybe case 2 and 3 can help you just to get informed because it is not recommended to use $.browser (the user agent can be spoofed using this). An alternative can be using that will detect feature support and not agent info.


If you insist on getting browser type (just Chrome or Safari) but not using $.browser, case 1 is what you looking for...

This fits your requirement:

Case 1: (No jQuery and no $.browser, just javascript)

Live Demo:

var isChrome = /Chrome/.test(navigator.userAgent) && /Google Inc/.test(navigator.vendor);
var isSafari = /Safari/.test(navigator.userAgent) && /Apple Computer/.test(navigator.vendor);

if (isChrome) alert("You are using Chrome!");
if (isSafari) alert("You are using Safari!");

These cases I used in times before and worked well but they are not recommended...

Case 2: (Using jQuery and $.browser, this one is tricky)

Live Demo:


    /* Get browser */
    $ = /chrome/.test(navigator.userAgent.toLowerCase());

    /* Detect Chrome */
        /* Do something for Chrome at this point */
        /* Finally, if it is Chrome then jQuery thinks it's 
           Safari so we have to tell it isn't */
        $.browser.safari = false;

    /* Detect Safari */
        /* Do something for Safari */


Case 3: (Using jQuery and $.browser, "elegant" solution)

Live Demo:

$ = $.browser.webkit && !!;
$.browser.safari = $.browser.webkit && !;

if ($ alert("You are using Chrome!");
if ($.browser.safari) alert("You are using Safari!");

sql server Get the FULL month name from a date

select datename(DAY,GETDATE()) +'-'+ datename(MONTH,GETDATE()) +'- '+ 
       datename(YEAR,GETDATE()) as 'yourcolumnname'

How do I exit a foreach loop in C#?

During testing I found that foreach loop after break go to the loop beging and not out of the loop. So I changed foreach into for and break in this case work correctly- after break program flow goes out of the loop.

How to delete specific rows and columns from a matrix in a smarter way?

You can use

t1<- t1[-4:-6,-7:-9]  


t1 <- t1[-(4:6), -(7:9)]


t1 <- t1[-c(4, 5, 6), -c(7, 8, 9)]

You can pass vectors to select rows/columns to be deleted. First two methods are useful if you are trying to delete contiguous rows/columns. Third method is useful if You are trying to delete discrete rows/columns.

> t1 <- array(1:20, dim=c(10,10));

> t1[-c(1, 4, 6, 7, 9), -c(2, 3, 8, 9)]

     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    2   12    2   12    2   12
[2,]    3   13    3   13    3   13
[3,]    5   15    5   15    5   15
[4,]    8   18    8   18    8   18
[5,]   10   20   10   20   10   20

How to find column names for all tables in all databases in SQL Server

SELECT AS ColumnName, AS TableName 
FROM sys.columns 
     JOIN sys.tables ON sys.columns.object_id = tables.object_id

How to get the input from the Tkinter Text Widget?

I would argue that creating a simple extension of Text and turning text into a property is the cleanest way to go. You can then stick that extension in some file that you always import, and use it instead of the original Text widget. This way, instead of having to remember, write, repeat, etc all the hoops tkinter makes you jump through to do the simplest things, you have a butt-simple interface that can be reused in any project. You can do this for Entry, as well, but the syntax is slightly different.

import tkinter as tk

root = tk.Tk()    
class Text(tk.Text):
    def text(self) -> str:
        return self.get('1.0', 'end-1c')
    def text(self, value) -> None:
        self.replace('1.0', 'end-1c', value)
    def __init__(self, master, **kwargs):
        tk.Text.__init__(self, master, **kwargs)

#Entry version of the same concept as above      
class Entry(tk.Entry):
    def text(self) -> str:
        return self.get()
    def text(self, value) -> None:
        self.delete(0, 'end')
        self.insert(0, value)
    def __init__(self, master, **kwargs):
        tk.Entry.__init__(self, master, **kwargs)      
textbox = Text(root)

textbox.text = "this is text" #set
print(textbox.text)           #get  

entry = Entry(root)

entry.text = 'this is text'   #set
print(entry.text)             #get


Package signatures do not match the previously installed version

Only 1 emulator or device may be open at a time. Make sure you don't have multiple emulators running.

Fit image into ImageView, keep aspect ratio and then resize ImageView to image dimensions?

Edited Jarno Argillanders answer:

How to fit Image with your Width and Height:

1) Initialize ImageView and set Image:

iv = (ImageView) findViewById(;

2) Now resize:


Edited scaleImage method: (you can replace EXPECTED bounding values)

private void scaleImage(ImageView view) {
    Drawable drawing = view.getDrawable();
    if (drawing == null) {
    Bitmap bitmap = ((BitmapDrawable) drawing).getBitmap();

    int width = bitmap.getWidth();
    int height = bitmap.getHeight();
    int xBounding = ((View) view.getParent()).getWidth();//EXPECTED WIDTH
    int yBounding = ((View) view.getParent()).getHeight();//EXPECTED HEIGHT

    float xScale = ((float) xBounding) / width;
    float yScale = ((float) yBounding) / height;

    Matrix matrix = new Matrix();
    matrix.postScale(xScale, yScale);

    Bitmap scaledBitmap = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
    width = scaledBitmap.getWidth();
    height = scaledBitmap.getHeight();
    BitmapDrawable result = new BitmapDrawable(context.getResources(), scaledBitmap);


    LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) view.getLayoutParams(); 
    params.width = width;
    params.height = height;

And .xml:

    android:layout_gravity="center_horizontal" />

Where do I download JDBC drivers for DB2 that are compatible with JDK 1.5?

Right here:

This is what I use for that exact purpose.

EDIT: Usage Examples (minus exceptions):

// Driver initialization
AS400JDBCDriver driver = new;

// JDBC Connection URL
String url = "jdbc:as400://" + ";promt=false" // disable GUI prompting by jt400 library

// Get a Connection object (this is used to create statements, etc)
Connection conn = DriverManager.getConnection(url, UserString, PassString);

Hope that helps!

Change label text using JavaScript

Here is another way to change the text of a label using jQuery:

  $("#lbltipAddedComment").text("your tip has been submitted!");

Check the JsFiddle example

How can I insert vertical blank space into an html document?

While the above answers are probably best for this situation, if you just want to do a one-off and don't want to bother with modifying other files, you can in-line the CSS.

<p style="margin-bottom:3cm;">This is the first question?</p>

Oracle - How to create a materialized view with FAST REFRESH and JOINS

Have you tried it without the ANSI join ?


How do I escape reserved words used as column names? MySQL/Create Table

You can use double quotes if ANSI SQL mode is enabled

     value TEXT NOT NULL

or the proprietary back tick escaping otherwise. (Where to find the ` character on various keyboard layouts is covered in this answer)

     value TEXT NOT NULL

(Source: MySQL Reference Manual, 9.3 Reserved Words)

Is it possible to specify condition in Count()?

Assuming you do not want to restrict the rows that are returned because you are aggregating other values as well, you can do it like this:

select count(case when Position = 'Manager' then 1 else null end) as ManagerCount
from ...

Let's say within the same column you had values of Manager, Supervisor, and Team Lead, you could get the counts of each like this:

select count(case when Position = 'Manager' then 1 else null end) as ManagerCount,
    count(case when Position = 'Supervisor' then 1 else null end) as SupervisorCount,
    count(case when Position = 'Team Lead' then 1 else null end) as TeamLeadCount,
from ...

Error: Configuration with name 'default' not found in Android Studio

This is probably a rare case, but for me a library that was included in the settings.gradle was not there.

E.g. I had: include ':libraries:Android-RateThisApp:library' in my settings.gradle

but the folder Android-RateThisApp was empty. As soon as I checked out this submodule the gradle sync succeed.

How do you compare structs for equality in C?

memcmp does not compare structure, memcmp compares the binary, and there is always garbage in the struct, therefore it always comes out False in comparison.

Compare element by element its safe and doesn't fail.

How do I check if a directory exists? "is_dir", "file_exists" or both?

$year = date("Y");   
$month = date("m");   
$filename = "../".$year;   
$filename2 = "../".$year."/".$month;


Check if specific input file is empty

check after the form is posted the following


python: NameError:global name '...‘ is not defined

You need to call self.a() to invoke a from b. a is not a global function, it is a method on the class.

You may want to read through the Python tutorial on classes some more to get the finer details down.

Batch File; List files in directory, only filenames?

Windows 10:

  1. open cmd

  2. change directory where you want to create text file(movie_list.txt) for the folder (d:\videos\movies)

  3. type following command

    d:\videos\movies> dir /b /a-d > movie_list.txt

How do I clone a generic list in C#?

To clone a list just call .ToList(). This creates a shallow copy.

Microsoft (R) Roslyn C# Compiler version
Loading context from 'CSharpInteractive.rsp'.
Type "#help" for more information.
> var x = new List<int>() { 3, 4 };
> var y = x.ToList();
> x.Add(5)
> x
List<int>(3) { 3, 4, 5 }
> y
List<int>(2) { 3, 4 }

How to validate an email address using a regular expression?

It depends on what you mean by best: If you're talking about catching every valid email address use the following:

(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:
\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(
?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ 
\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\0
31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\
](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+
(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:
(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)
?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\
r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[
 \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)
?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t]
)*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[
 \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*
)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)
*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+
|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r
\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t
]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031
]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](
?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?
:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?
:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?
:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?
[ \t]))*"(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] 
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|
\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>
@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"
(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?
:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[
\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-
\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(
?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;
:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([
^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"
.\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\
]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\
[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\
r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] 
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]
|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \0
00-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\
.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,
;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?
:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[
^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]
]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*(
?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(
?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[
\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t
])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t
])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?
:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|
\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:
[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\
]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)
?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["
()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)
?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>
@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[
 \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,
;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:
\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[
"()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])
*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])
+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\
.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(
?:\r\n)?[ \t])*))*)?;\s*)

( If you're looking for something simpler but that will catch most valid email addresses try something like:


EDIT: From the link:

This regular expression will only validate addresses that have had any comments stripped and replaced with whitespace (this is done by the module).

How to check if a user likes my Facebook Page or URL using Facebook's API

I tore my hair out over this one too. Your code only works if the user has granted an extended permission for that which is not ideal.

Here's another approach.

In a nutshell, if you turn on the OAuth 2.0 for Canvas advanced option, Facebook will send a $_REQUEST['signed_request'] along with every page requested within your tab app. If you parse that signed_request you can get some info about the user including if they've liked the page or not.

function parsePageSignedRequest() {
    if (isset($_REQUEST['signed_request'])) {
      $encoded_sig = null;
      $payload = null;
      list($encoded_sig, $payload) = explode('.', $_REQUEST['signed_request'], 2);
      $sig = base64_decode(strtr($encoded_sig, '-_', '+/'));
      $data = json_decode(base64_decode(strtr($payload, '-_', '+/'), true));
      return $data;
    return false;
  if($signed_request = parsePageSignedRequest()) {
    if($signed_request->page->liked) {
      echo "This content is for Fans only!";
    } else {
      echo "Please click on the Like button to view this tab!";

Updating state on props change in React Form

Use Memoize

The op's derivation of state is a direct manipulation of props, with no true derivation needed. In other words, if you have a prop which can be utilized or transformed directly there is no need to store the prop on state.

Given that the state value of start_time is simply the prop start_time.format("HH:mm"), the information contained in the prop is already in itself sufficient for updating the component.

However if you did want to only call format on a prop change, the correct way to do this per latest documentation would be via Memoize:

How to clear cache in Yarn?

Run yarn cache clean.

Run yarn help cache in your bash, and you will see:

Usage: yarn cache [ls|clean] [flags]

Options: -h, --help output usage information -V, --version output the version number --offline
--global-folder [path]
--modules-folder [path] rather than installing modules into the node_modules folder relative to the cwd, output them here
--packages-root [path] rather than storing modules into a global packages root, store them here
--mutex [type][:specifier] use a mutex to ensure only one yarn instance is executing

Visit for documentation about this command.

How to remove time portion of date in C# in DateTime object only?

If you want to remove part of time from a DateTime, try using this code:

DateTime dt = new DateTime();

dt = DateTime.Now; //ex: 31/1/2017 6:30:20 PM

TimeSpan remainingTime = new TimeSpan(0, dt.Hour - 5, dt.Minute - 29, dt.Second - 19);

label1.Text = dt.ToString("HH:mm:ss"); // must be HH not hh

the output : 01:01:01

Java random numbers using a seed

You shouldn't be creating a new Random in method scope. Make it a class member:

public class Foo {
   private Random random 

   public Foo() {

   public Foo(long seed) {
       this.random = new Random(seed);

   public synchronized double getNext() {
        return generator.nextDouble();

This is only an example. I don't think wrapping Random this way adds any value. Put it in a class of yours that is using it.

Which MySQL datatype to use for an IP address?

You have two possibilities (for an IPv4 address) :

  • a varchar(15), if your want to store the IP address as a string
    • for instance
  • an integer (4 bytes), if you convert the IP address to an integer
    • 3229614095 for the IP I used before

The second solution will require less space in the database, and is probably a better choice, even if it implies a bit of manipulations when storing and retrieving the data (converting it from/to a string).

About those manipulations, see the ip2long() and long2ip() functions, on the PHP-side, or inet_aton() and inet_ntoa() on the MySQL-side.

Android get Current UTC time

System.currentTimeMillis() does give you the number of milliseconds since January 1, 1970 00:00:00 UTC. The reason you see local times might be because you convert a Date instance to a string before using it. You can use DateFormats to convert Dates to Strings in any timezone:

DateFormat df = DateFormat.getTimeInstance();
String gmtTime = df.format(new Date());

Also see this related question.

Performance of FOR vs FOREACH in PHP

My personal opinion is to use what makes sense in the context. Personally I almost never use for for array traversal. I use it for other types of iteration, but foreach is just too easy... The time difference is going to be minimal in most cases.

The big thing to watch for is:

for ($i = 0; $i < count($array); $i++) {

That's an expensive loop, since it calls count on every single iteration. So long as you're not doing that, I don't think it really matters...

As for the reference making a difference, PHP uses copy-on-write, so if you don't write to the array, there will be relatively little overhead while looping. However, if you start modifying the array within the array, that's where you'll start seeing differences between them (since one will need to copy the entire array, and the reference can just modify inline)...

As for the iterators, foreach is equivalent to:

while ($it->valid()) {
    $key = $it->key();     // If using the $key => $value syntax
    $value = $it->current();

    // Contents of loop in here


As far as there being faster ways to iterate, it really depends on the problem. But I really need to ask, why? I understand wanting to make things more efficient, but I think you're wasting your time for a micro-optimization. Remember, Premature Optimization Is The Root Of All Evil...

Edit: Based upon the comment, I decided to do a quick benchmark run...

$a = array();
for ($i = 0; $i < 10000; $i++) {
    $a[] = $i;

$start = microtime(true);
foreach ($a as $k => $v) {
    $a[$k] = $v + 1;
echo "Completed in ", microtime(true) - $start, " Seconds\n";

$start = microtime(true);
foreach ($a as $k => &$v) {
    $v = $v + 1;
echo "Completed in ", microtime(true) - $start, " Seconds\n";

$start = microtime(true);
foreach ($a as $k => $v) {}
echo "Completed in ", microtime(true) - $start, " Seconds\n";

$start = microtime(true);
foreach ($a as $k => &$v) {}    
echo "Completed in ", microtime(true) - $start, " Seconds\n";

And the results:

Completed in 0.0073502063751221 Seconds
Completed in 0.0019769668579102 Seconds
Completed in 0.0011849403381348 Seconds
Completed in 0.00111985206604 Seconds

So if you're modifying the array in the loop, it's several times faster to use references...

And the overhead for just the reference is actually less than copying the array (this is on 5.3.2)... So it appears (on 5.3.2 at least) as if references are significantly faster...

href overrides ng-click in Angular.js

In Angular, <a>s are directives. As such, if you have an empty href or no href, Angular will call event.preventDefault.

From the source:

    element.on('click', function(event){
      // if we have no href url, then don't navigate anywhere.
      if (!element.attr(href)) {

Here's a plnkr demonstrating the missing href scenario.

What are the true benefits of ExpandoObject?

Since I wrote the MSDN article you are referring to, I guess I have to answer this one.

First, I anticipated this question and that's why I wrote a blog post that shows a more or less real use case for ExpandoObject: Dynamic in C# 4.0: Introducing the ExpandoObject.

Shortly, ExpandoObject can help you create complex hierarchical objects. For example, imagine that you have a dictionary within a dictionary:

Dictionary<String, object> dict = new Dictionary<string, object>();
Dictionary<String, object> address = new Dictionary<string,object>();
dict["Address"] = address;
address["State"] = "WA";

The deeper is the hierarchy, the uglier is the code. With ExpandoObject it stays elegant and readable.

dynamic expando = new ExpandoObject();
expando.Address = new ExpandoObject();
expando.Address.State = "WA";

Second, as it was already pointed out, ExpandoObject implements INotifyPropertyChanged interface which gives you more control over properties than a dictionary.

Finally, you can add events to ExpandoObject like here:

class Program
   static void Main(string[] args)
       dynamic d = new ExpandoObject();

       // Initialize the event to null (meaning no handlers)
       d.MyEvent = null;

       // Add some handlers
       d.MyEvent += new EventHandler(OnMyEvent);
       d.MyEvent += new EventHandler(OnMyEvent2);

       // Fire the event
       EventHandler e = d.MyEvent;

       e?.Invoke(d, new EventArgs());

   static void OnMyEvent(object sender, EventArgs e)
       Console.WriteLine("OnMyEvent fired by: {0}", sender);

   static void OnMyEvent2(object sender, EventArgs e)
       Console.WriteLine("OnMyEvent2 fired by: {0}", sender);

Also, keep in mind that nothing is preventing you from accepting event arguments in a dynamic way. In other words, instead of using EventHandler, you can use EventHandler<dynamic> which would cause the second argument of the handler to be dynamic.

Razor-based view doesn't see referenced assemblies

In my case, I was using Razor Views outside of a web application.
Copying the dlls to my bin folder in solution solved the problem.

Check if string is in a pandas dataframe

a['Names'].str.contains('Mel') will return an indicator vector of boolean values of size len(BabyDataSet)

Therefore, you can use

if mel_count>0:
    print ("There are {m} Mels".format(m=mel_count))

Or any(), if you don't care how many records match your query

if a['Names'].str.contains('Mel').any():
    print ("Mel is there")

How to insert values in table with foreign key using MySQL?

Case 1

INSERT INTO tab_student (name_student, id_teacher_fk)
    VALUES ('dan red', 
           (SELECT id_teacher FROM tab_teacher WHERE name_teacher ='jason bourne')

it is advisable to store your values in lowercase to make retrieval easier and less error prone

Case 2

mysql docs

INSERT INTO tab_teacher (name_teacher) 
    VALUES ('tom stills')
INSERT INTO tab_student (name_student, id_teacher_fk)
    VALUES ('rich man', LAST_INSERT_ID())

MySQL Query - Records between Today and Last 30 Days

Here's a solution without using curdate() function, this is a solution for those who use TSQL I guess

FROM myTable

TypeError("'bool' object is not iterable",) when trying to return a Boolean

Look at the traceback:

Traceback (most recent call last):
  File "C:\Python33\lib\site-packages\", line 821, in _cast
    out = iter(out)
TypeError: 'bool' object is not iterable

Your code isn't iterating the value, but the code receiving it is.

The solution is: return an iterable. I suggest that you either convert the bool to a string (str(False)) or enclose it in a tuple ((False,)).

Always read the traceback: it's correct, and it's helpful.

How do I use a delimiter with Scanner.useDelimiter in Java?

With Scanner the default delimiters are the whitespace characters.

But Scanner can define where a token starts and ends based on a set of delimiter, wich could be specified in two ways:

  1. Using the Scanner method: useDelimiter(String pattern)
  2. Using the Scanner method : useDelimiter(Pattern pattern) where Pattern is a regular expression that specifies the delimiter set.

So useDelimiter() methods are used to tokenize the Scanner input, and behave like StringTokenizer class, take a look at these tutorials for further information:

And here is an Example:

public static void main(String[] args) {

    // Initialize Scanner object
    Scanner scan = new Scanner("Anna Mills/Female/18");
    // initialize the string delimiter
    // Printing the tokenized Strings
    // closing the scanner stream

Prints this output:

Anna Mills

Image Greyscale with CSS & re-color on mouse-over?

I use the following code on

Smooth transition from b/w to color with magnifying effect (scale)

    img.color_flip {
      filter: url(filters.svg#grayscale); /* Firefox 3.5+ */
      filter: gray; /* IE5+ */
      -webkit-filter: grayscale(1); /* Webkit Nightlies & Chrome Canary */
      -webkit-transition: all .5s ease-in-out;

    img.color_flip:hover {
      filter: none;
      -webkit-filter: grayscale(0);
      -webkit-transform: scale(1.1);

C# switch statement limitations - why?

According to the switch statement documentation if there is an unambiguous way to implicitly convert the the object to an integral type, then it will be allowed. I think you are expecting a behavior where for each case statement it would be replaced with if (t == typeof(int)), but that would open a whole can of worms when you get to overload that operator. The behavior would change when implementation details for the switch statement changed if you wrote your == override incorrectly. By reducing the comparisons to integral types and string and those things that can be reduced to integral types (and are intended to) they avoid potential issues.

Sound effects in JavaScript / HTML5

It's not possible to do multi-shot playing with a single <audio> element. You need to use multiple elements for this.

Compress images on client side before uploading

If you are looking for a library to carry out client-side image compression, you can check this out:compress.js. This will basically help you compress multiple images purely with JavaScript and convert them to base64 string. You can optionally set the maximum size in MB and also the preferred image quality.

Best way to verify string is empty or null

With the openJDK 11 you can use the internal validation to check if the String is null or just white spaces

import jdk.internal.joptsimple.internal.Strings;

String targetString;
if (Strings.isNullOrEmpty(tragetString)) {}

PHP Check for NULL

How about using

if (empty($result['column']))

Git: Installing Git in PATH with GitHub client for Windows

To get this to work I had to combine many of the above answers, to anyone who this might help here is my much simpler process.

If you have Windows 10 just start typing "edit environmental..." and it'll pop up right away. Click path and Edit… then paste the ;C:\Program Files\Git\bin\git.exe;C:\Program Files\Git\cmd at the end of the path already there, don't forget the ; to separate your new github path from the current path.

You do not need the guid but if you want to know how to find it open bash, type git --man-path

Working with huge files in VIM

Old thread. But nevertheless( pun :) ).

 $less filename

less works efficiently if you don't want to edit and just look around which is the case for examining huge log files.

Search in less works like vi

Best part, it's available by default on most distros. So won't be problem for production environment as well.

jQuery get text as number

var number = parseInt($(this).find('.number').text());
var current = 600;
if (current > number)
     // do something

Fatal error: Class 'PHPMailer' not found

This is just namespacing. Look at the examples for reference - you need to either use the namespaced class or reference it absolutely, for example:

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

//Load composer's autoloader
require 'vendor/autoload.php';

Replace \n with actual new line in Sublime Text

For Windows line endings:

(Turn on regex - Alt+R)

Find: \\r\\n

Replace: \r\n


shift a std_logic_vector of n bit to right or left

Use the ieee.numeric_std library, and the appropriate vector type for the numbers you are working on (unsigned or signed).

Then the operators are sla/sra for arithmetic shifts (ie fill with sign bit on right shifts and lsb on left shifts) and sll/srl for logical shifts (ie fill with '0's).

You pass a parameter to the operator to define the number of bits to shift:

A <= B srl 2; -- logical shift right 2 bits


I have no idea what I was writing above (thanks to Val for pointing that out!)

Of course the correct way to shift signed and unsigned types is with the shift_left and shift_right functions defined in ieee.numeric_std.

The shift and rotate operators sll, ror etc are for vectors of boolean, bit or std_ulogic, and can have interestingly unexpected behaviour in that the arithmetic shifts duplicate the end-bit even when shifting left.

And much more history can be found here:

However, the answer to the original question is still

sig <= tmp sll number_of_bits;

Read url to string in few lines of java code

Java 11+:

URI uri = URI.create("");
HttpRequest request = HttpRequest.newBuilder(uri).build();
String content = HttpClient.newHttpClient().send(request, BodyHandlers.ofString()).body();

How to set max width of an image in CSS

I see this hasn't been answered as final.

I see you have max-width as 100% and width as 600. Flip those.

A simple way also is:

     <img src="image.png" style="max-width:600px;width:100%">

I use this often, and then you can control individual images as well, and not have it on all img tags. You could CSS it also like below.


     <img src="image.png" class="image600">

How do I get the APK of an installed app without root access?

Open ES explorer -> push Menu button at the left upper corner (three horizontal stripes) -> in the Libraries section choose APPs.

Thus, you get the list of all the user apps. Find your app and select it with long pushing on it. Then press "More" in the right low corner and choose "Send". Then you can use different options, e.g. you can choose "ES Save To" in order to save the .apk file to your home directory or anywhere else.

How to set radio button selected value using jquery

  <input type="radio" name="RBLExperienceApplicable" class="radio" value="1" checked > 
 //       For Example it is checked
 <input type="radio" name="RBLExperienceApplicable" class="radio" value="0" >

<input type="radio" name="RBLExperienceApplicable2" class="radio" value="1" > 
<input type="radio" name="RBLExperienceApplicable2" class="radio" value="0" >

      $( "input[type='radio']" ).change(function() //on change radio buttons

   if($('input[name=RBLExperienceApplicable]:checked').val() != '') //Testing value

$('input[name=RBLExperienceApplicable]:checked').val('Your value Without Quotes');

    }); Demo

enter image description here

How do I set the visibility of a text box in SSRS using an expression?

Visibility of the text box depends on the Hidden Value

As per the below example, if the internal condition satisfies then text box Hidden functionality will be True else if the condition fails then text box Hidden functionality will be False

=IIf((CountRows("ScannerStatisticsData") = 0), True, False)

Just get column names from hive table

use desc tablename from Hive CLI or beeline to get all the column names. If you want the column names in a file then run the below command from the shell.

$ hive -e 'desc dbname.tablename;' > ~/columnnames.txt

where dbname is the name of the Hive database where your table is residing You can find the file columnnames.txt in your root directory.

$cd ~

How can I find out what version of git I'm running?

which git &> /dev/null || { echo >&2 "I require git but it's not installed.  Aborting."; exit 1; }
echo "Git is installed."

That will echo "Git is installed" if it is, otherwise, it'll echo an error message. You can use this for scripts that use git

It's also customizable, so you can change "which git" to "which java" or something, and change the error message.

Get list of all input objects using JavaScript, without accessing a form object

var inputs = document.getElementsByTagName('input');
for (var i = 0; i < inputs.length; ++i) {
  // ...

Run-time error '1004' - Method 'Range' of object'_Global' failed


Range(DataImportColumn & DataImportRow).Offset(0, 2).Value



When you just have the row and the column then you can use the cells() object. The syntax is Cells(Row,Column)

Also one more tip. You might want to fully qualify your Cells object. for example


Setting the default value of a DateTime Property to DateTime.Now inside the System.ComponentModel Default Value Attrbute

I needed a UTC Timestamp as a default value and so modified Daniel's solution like this:

    [Column(TypeName = "datetime2")]
    [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:yyyy-MM-dd}")]
    [Display(Name = "Date Modified")]
    [DateRange(Min = "1900-01-01", Max = "2999-12-31")]
    public DateTime DateModified {
        get { return dateModified; }
        set { dateModified = value; } 
    private DateTime dateModified = DateTime.Now.ToUniversalTime();

For DateRangeAttribute tutorial, see this awesome blog post

Select row with most recent date per user

select b.* from 

        `lms_attendance`.`user` AS `user`,
        max(`lms_attendance`.`time`) AS `time`
    from `lms_attendance` 
    group by 
        `lms_attendance`.`user`) a


    (select * 
    from `lms_attendance` ) b

on a.user = b.user
and a.time = b.time

Iterating over a numpy array

If you only need the indices, you could try numpy.ndindex:

>>> a = numpy.arange(9).reshape(3, 3)
>>> [(x, y) for x, y in numpy.ndindex(a.shape)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]

foreach vs someList.ForEach(){}

For fun, I popped List into reflector and this is the resulting C#:

public void ForEach(Action<T> action)
    if (action == null)
    for (int i = 0; i < this._size; i++)

Similarly, the MoveNext in Enumerator which is what is used by foreach is this:

public bool MoveNext()
    if (this.version != this.list._version)
    if (this.index < this.list._size)
        this.current = this.list._items[this.index];
        return true;
    this.index = this.list._size + 1;
    this.current = default(T);
    return false;

The List.ForEach is much more trimmed down than MoveNext - far less processing - will more likely JIT into something efficient..

In addition, foreach() will allocate a new Enumerator no matter what. The GC is your friend, but if you're doing the same foreach repeatedly, this will make more throwaway objects, as opposed to reusing the same delegate - BUT - this is really a fringe case. In typical usage you will see little or no difference.

How to get VM arguments from inside of Java application?

If you want the entire command line of your java process, you can use: (uses a combination of JNA + /proc to cover most unix implementations)

Maven skip tests

There is a difference between each parameter.

  • The -DskipTests skip running tests phase, it means at the end of this process you will have your tests compiled.

  • The -Dmaven.test.skip=true skip compiling and running tests phase.

As the parameter -Dmaven.test.skip=true skip compiling you don't have the tests artifact.

For more information just read the surfire documentation:

Which is the best Linux C/C++ debugger (or front-end to gdb) to help teaching programming?

ddd is a graphical front-end to gdb that is pretty nice. One of the down sides is a classic X interface, but I seem to recall it being pretty intuitive.

psql: FATAL: role "postgres" does not exist

I needed to unset $PGUSER:

$ unset PGUSER
$ createuser -s postgres

How to resolve "could not execute statement; SQL [n/a]; constraint [numbering];"?

Future readers.

I have had the best luck figuring out these issues....using this method:

private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(MyDaoObject.class);

public void save(MyObject item) {

    try {
         /* this is whatever code you have already...this is just an example */
    catch(Exception ex)
        /* below works in conjunction with concrete logging framework */
        logger.error(ex.getMessage(), ex);
        throw ex;

Now, slf4j is just a fascade (interfaces, adapter)..... you need a concrete.

When picking log4j2, you want to persist the


So you are not flying blind, you can see %throwable at the below URL (on how you defined %throwable so it shows up in the logging. If you're not using log4j2 as the concrete, you'll have to figure out your logging framework's version of %throwable)

That %throwable, when logged, will have the actual SQL exception in it.

if throwable is giving you a fuss, you can do this (the below is NOT great since it does recursive log calls)

public void save(MyObject item) {

    try {
         /* this is whatever code you have already...this is just an example */
    catch(Exception ex)
        logger.error(ex.getMessage(), ex);
        //throw ex;
        Throwable thr = ex;
        /* recursive logging warning !!! could perform very poorly, not for production....alternate idea is to use Stringbuilder and log the stringbuilder result */
        while (null != thr) {
            logger.error(thr.getMessage(), thr);
            thr = thr.getCause();

How to create loading dialogs in Android?

It's a ProgressDialog, with setIndeterminate(true).


ProgressDialog dialog =, "", 
                    "Loading. Please wait...", true);

An indeterminate progress bar doesn't actually show a bar, it shows a spinning activity circle thing. I'm sure you know what I mean :)

How are parameters sent in an HTTP POST request?

The values are sent in the request body, in the format that the content type specifies.

Usually the content type is application/x-www-form-urlencoded, so the request body uses the same format as the query string:


When you use a file upload in the form, you use the multipart/form-data encoding instead, which has a different format. It's more complicated, but you usually don't need to care what it looks like, so I won't show an example, but it can be good to know that it exists.

Request failed: unacceptable content-type: text/html using AFNetworking 2.0

If someone is using AFHTTPSessionManager then one can do like this to solve the issue,

I subclassed AFHTTPSessionManager where I'm doing like this,

NSMutableSet *contentTypes = [[NSMutableSet alloc] initWithSet:self.responseSerializer.acceptableContentTypes];
[contentTypes addObject:@"text/html"];
self.responseSerializer.acceptableContentTypes = contentTypes;

How to create a pivot query in sql server without aggregate function

SELECT [Period], [Account], [Value]
FROM TableName
) AS source
    FOR [Period] IN ([2000], [2001], [2002])
) as pvt

Another way,

      MAX(CASE WHEN Period = '2000' THEN Value ELSE NULL END) [2000],
      MAX(CASE WHEN Period = '2001' THEN Value ELSE NULL END) [2001],
      MAX(CASE WHEN Period = '2002' THEN Value ELSE NULL END) [2002]
FROM tableName
GROUP BY Account

Is there a way to create xxhdpi, xhdpi, hdpi, mdpi and ldpi drawables from a large scale image?

A bash script using ImageMagick (convert) as per CommonsWare's answer:

Added folder creation and argument check thanks to Kishan Vaghela

# Given an xxhdpi image or an App Icon (launcher), this script
# creates different dpis resources and the necessary folders
# if they don't exist
# Place this script, as well as the source image, inside res
# folder and execute it passing the image filename as argument
# Example:
# ./ ic_launcher.png
# OR
# ./ my_cool_xxhdpi_image.png
# Copyright (c) 2016 Ricardo Romao.
# This free software comes with ABSOLUTELY NO WARRANTY and
# is distributed under GNU GPL v3 license. 

if [ $# -eq 0 ]; then
    echo "No arguments supplied"
else if [ -f "$1" ]; then
    echo " Creating different dimensions (dips) of "$1" ..."
    mkdir -p drawable-xxxhdpi
    mkdir -p drawable-xxhdpi
    mkdir -p drawable-xhdpi
    mkdir -p drawable-hdpi
    mkdir -p drawable-mdpi

    if [ $1 = "ic_launcher.png" ]; then
        echo "  App icon detected"
        convert ic_launcher.png -resize 144x144 drawable-xxhdpi/ic_launcher.png
        convert ic_launcher.png -resize 96x96 drawable-xhdpi/ic_launcher.png
        convert ic_launcher.png -resize 72x72 drawable-hdpi/ic_launcher.png
        convert ic_launcher.png -resize 48x48 drawable-mdpi/ic_launcher.png
        rm -i ic_launcher.png
        convert $1 -resize 75% drawable-xxhdpi/$1
        convert $1 -resize 50% drawable-xhdpi/$1
        convert $1 -resize 38% drawable-hdpi/$1
        convert $1 -resize 25% drawable-mdpi/$1
        mv $1 drawable-xxxhdpi/$1
echo " Done"
    echo "$1 not found."

Only detect click event on pseudo-element

This works for me:

$('#element').click(function (e) {
        if (e.offsetX > {
            // click on element
           // click on ::before element

git with IntelliJ IDEA: Could not read from remote repository

I've resolved this by adding my SSH private key to the ssh-agent in the command:

$ ssh-add -K ~/.ssh/id_rsa

And setting Settings --> Version Control --> Git, and then, in the SSH executable dropdown, choose Native

how to get right offset of an element? - jQuery

Just an addition to what Greg said:

$("#whatever").offset().left + $("#whatever").outerWidth()

This code will get the right position relative to the left side. If the intention was to get the right side position relative to the right (like when using the CSS right property) then an addition to the code is necessary as follows:

$("#parent_container").innerWidth() - ($("#whatever").offset().left + $("#whatever").outerWidth())

This code is useful in animations where you have to set the right side as a fixed anchor when you can't initially set the right property in CSS.

Create a BufferedImage from file and make it TYPE_INT_ARGB

Create a BufferedImage from file and make it TYPE_INT_RGB

import java.awt.image.*;
import javax.imageio.*;
public class Main{
    public static void main(String args[]){
            BufferedImage img = new BufferedImage( 
                500, 500, BufferedImage.TYPE_INT_RGB );
            File f = new File("MyFile.png");
            int r = 5;
            int g = 25; 
            int b = 255;
            int col = (r << 16) | (g << 8) | b;
            for(int x = 0; x < 500; x++){
                for(int y = 20; y < 300; y++){
                    img.setRGB(x, y, col);
            ImageIO.write(img, "PNG", f); 
        catch(Exception e){ 

This paints a big blue streak across the top.

If you want it ARGB, do it like this:

        BufferedImage img = new BufferedImage( 
            500, 500, BufferedImage.TYPE_INT_ARGB );
        File f = new File("MyFile.png");
        int r = 255;
        int g = 10;
        int b = 57;
        int alpha = 255;
        int col = (alpha << 24) | (r << 16) | (g << 8) | b;
        for(int x = 0; x < 500; x++){
            for(int y = 20; y < 30; y++){
                img.setRGB(x, y, col);
        ImageIO.write(img, "PNG", f);
    catch(Exception e){

Open up MyFile.png, it has a red streak across the top.

setting min date in jquery datepicker

$(function () {
        dateFormat: 'yy-mm-dd',
        showButtonPanel: true,
        changeMonth: true,
        changeYear: true,
yearRange: '1999:2012',
        showOn: "button",
        buttonImage: "images/calendar.gif",
        buttonImageOnly: true,
        minDate: new Date(1999, 10 - 1, 25),
        maxDate: '+30Y',
        inline: true

Just added year range option. It should solve the problem

Initializing C# auto-properties

This will be possible in C# 6.0:

public int Y { get; } = 2;

How can I convert an image into Base64 string using JavaScript?

Try this code:

For a file upload change event, call this function:

$("#fileproof").on('change', function () {
    readImage($(this)).done(function (base64Data) { $('#<%=hfimgbs64.ClientID%>').val(base64Data); });

function readImage(inputElement) {
    var deferred = $.Deferred();

    var files = inputElement.get(0).files;

    if (files && files[0]) {
        var fr = new FileReader();
        fr.onload = function (e) {
    } else {

    return deferred.promise();

Store Base64 data in hidden filed to use.

Plotting multiple curves same graph and same scale

You aren't being very clear about what you want here, since I think @DWin's is technically correct, given your example code. I think what you really want is this:

y1 <- c(100, 200, 300, 400, 500)
y2 <- c(1, 2, 3, 4, 5)
x <- c(1, 2, 3, 4, 5)

# first plot
plot(x, y1,ylim = range(c(y1,y2)))

# Add points
points(x, y2)

DWin's solution was operating under the implicit assumption (based on your example code) that you wanted to plot the second set of points overlayed on the original scale. That's why his image looks like the points are plotted at 1, 101, etc. Calling plot a second time isn't what you want, you want to add to the plot using points. So the above code on my machine produces this:

enter image description here

But DWin's main point about using ylim is correct.

Best practice for REST token-based authentication with JAX-RS and Jersey

This answer is all about authorization and it is a complement of my previous answer about authentication

Why another answer? I attempted to expand my previous answer by adding details on how to support JSR-250 annotations. However the original answer became the way too long and exceeded the maximum length of 30,000 characters. So I moved the whole authorization details to this answer, keeping the other answer focused on performing authentication and issuing tokens.

Supporting role-based authorization with the @Secured annotation

Besides authentication flow shown in the other answer, role-based authorization can be supported in the REST endpoints.

Create an enumeration and define the roles according to your needs:

public enum Role {

Change the @Secured name binding annotation created before to support roles:

@Target({TYPE, METHOD})
public @interface Secured {
    Role[] value() default {};

And then annotate the resource classes and methods with @Secured to perform the authorization. The method annotations will override the class annotations:

public class ExampleResource {

    public Response myMethod(@PathParam("id") Long id) {
        // This method is not annotated with @Secured
        // But it's declared within a class annotated with @Secured({Role.ROLE_1})
        // So it only can be executed by the users who have the ROLE_1 role

    @Secured({Role.ROLE_1, Role.ROLE_2})
    public Response myOtherMethod(@PathParam("id") Long id) {
        // This method is annotated with @Secured({Role.ROLE_1, Role.ROLE_2})
        // The method annotation overrides the class annotation
        // So it only can be executed by the users who have the ROLE_1 or ROLE_2 roles

Create a filter with the AUTHORIZATION priority, which is executed after the AUTHENTICATION priority filter defined previously.

The ResourceInfo can be used to get the resource Method and resource Class that will handle the request and then extract the @Secured annotations from them:

public class AuthorizationFilter implements ContainerRequestFilter {

    private ResourceInfo resourceInfo;

    public void filter(ContainerRequestContext requestContext) throws IOException {

        // Get the resource class which matches with the requested URL
        // Extract the roles declared by it
        Class<?> resourceClass = resourceInfo.getResourceClass();
        List<Role> classRoles = extractRoles(resourceClass);

        // Get the resource method which matches with the requested URL
        // Extract the roles declared by it
        Method resourceMethod = resourceInfo.getResourceMethod();
        List<Role> methodRoles = extractRoles(resourceMethod);

        try {

            // Check if the user is allowed to execute the method
            // The method annotations override the class annotations
            if (methodRoles.isEmpty()) {
            } else {

        } catch (Exception e) {

    // Extract the roles from the annotated element
    private List<Role> extractRoles(AnnotatedElement annotatedElement) {
        if (annotatedElement == null) {
            return new ArrayList<Role>();
        } else {
            Secured secured = annotatedElement.getAnnotation(Secured.class);
            if (secured == null) {
                return new ArrayList<Role>();
            } else {
                Role[] allowedRoles = secured.value();
                return Arrays.asList(allowedRoles);

    private void checkPermissions(List<Role> allowedRoles) throws Exception {
        // Check if the user contains one of the allowed roles
        // Throw an Exception if the user has not permission to execute the method

If the user has no permission to execute the operation, the request is aborted with a 403 (Forbidden).

To know the user who is performing the request, see my previous answer. You can get it from the SecurityContext (which should be already set in the ContainerRequestContext) or inject it using CDI, depending on the approach you go for.

If a @Secured annotation has no roles declared, you can assume all authenticated users can access that endpoint, disregarding the roles the users have.

Supporting role-based authorization with JSR-250 annotations

Alternatively to defining the roles in the @Secured annotation as shown above, you could consider JSR-250 annotations such as @RolesAllowed, @PermitAll and @DenyAll.

JAX-RS doesn't support such annotations out-of-the-box, but it could be achieved with a filter. Here are a few considerations to keep in mind if you want to support all of them:

So an authorization filter that checks JSR-250 annotations could be like:

public class AuthorizationFilter implements ContainerRequestFilter {

    private ResourceInfo resourceInfo;

    public void filter(ContainerRequestContext requestContext) throws IOException {

        Method method = resourceInfo.getResourceMethod();

        // @DenyAll on the method takes precedence over @RolesAllowed and @PermitAll
        if (method.isAnnotationPresent(DenyAll.class)) {

        // @RolesAllowed on the method takes precedence over @PermitAll
        RolesAllowed rolesAllowed = method.getAnnotation(RolesAllowed.class);
        if (rolesAllowed != null) {
            performAuthorization(rolesAllowed.value(), requestContext);

        // @PermitAll on the method takes precedence over @RolesAllowed on the class
        if (method.isAnnotationPresent(PermitAll.class)) {
            // Do nothing

        // @DenyAll can't be attached to classes

        // @RolesAllowed on the class takes precedence over @PermitAll on the class
        rolesAllowed = 
        if (rolesAllowed != null) {
            performAuthorization(rolesAllowed.value(), requestContext);

        // @PermitAll on the class
        if (resourceInfo.getResourceClass().isAnnotationPresent(PermitAll.class)) {
            // Do nothing

        // Authentication is required for non-annotated methods
        if (!isAuthenticated(requestContext)) {

     * Perform authorization based on roles.
     * @param rolesAllowed
     * @param requestContext
    private void performAuthorization(String[] rolesAllowed, 
                                      ContainerRequestContext requestContext) {

        if (rolesAllowed.length > 0 && !isAuthenticated(requestContext)) {

        for (final String role : rolesAllowed) {
            if (requestContext.getSecurityContext().isUserInRole(role)) {


     * Check if the user is authenticated.
     * @param requestContext
     * @return
    private boolean isAuthenticated(final ContainerRequestContext requestContext) {
        // Return true if the user is authenticated or false otherwise
        // An implementation could be like:
        // return requestContext.getSecurityContext().getUserPrincipal() != null;

     * Refuse the request.
    private void refuseRequest() {
        throw new AccessDeniedException(
            "You don't have permissions to perform this action.");

Note: The above implementation is based on the Jersey RolesAllowedDynamicFeature. If you use Jersey, you don't need to write your own filter, just use the existing implementation.

"RuntimeError: Make sure the Graphviz executables are on your system's path" after installing Graphviz 2.38

1.install windows package from: and download msi file

Add in Environmental variables 2. Add C:\Program Files (x86)\Graphviz2.38\bin to User path

  1. Add C:\Program Files (x86)\Graphviz2.38\bin\dot.exe to System Path

  2. Restart your python notebook.

It will work.

Python vs Cpython

You should know that CPython doesn't really support multithreading (it does, but not optimal) because of the Global Interpreter Lock. It also has no Optimisation mechanisms for recursion, and has many other limitations that other implementations and libraries try to fill.

You should take a look at this page on the python wiki.

Look at the code snippets on this page, it'll give you a good idea of what an interpreter is.

Setting default values for columns in JPA

you can use the java reflect api:

    void preInsert() {

This is common:

    public class PrePersistUtil {

        private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

        public static void pre(Object object){
            try {
                Field[] fields = object.getClass().getDeclaredFields();
                for(Field field : fields){
                    if (field.getType().getName().equals("java.lang.Long")
                            && field.get(object) == null){
                    }else if    (field.getType().getName().equals("java.lang.String")
                            && field.get(object) == null){
                    }else if (field.getType().getName().equals("java.util.Date")
                            && field.get(object) == null){
                    }else if (field.getType().getName().equals("java.lang.Double")
                            && field.get(object) == null){
                    }else if (field.getType().getName().equals("java.lang.Integer")
                            && field.get(object) == null){
                    }else if (field.getType().getName().equals("java.lang.Float")
                            && field.get(object) == null){
            } catch (IllegalAccessException e) {
            } catch (ParseException e) {

PHP, MySQL error: Column count doesn't match value count at row 1

You have 9 fields listed, but only 8 values. Try adding the method.

Simple way to repeat a string

Here is the shortest version (Java 1.5+ required):

repeated = new String(new char[n]).replace("\0", s);

Where n is the number of times you want to repeat the string and s is the string to repeat.

No imports or libraries needed.

Sort an ArrayList based on an object field

Modify the DataNode class so that it implements Comparable interface.

public int compareTo(DataNode o)
     return(degree -;

then just use


What is the "right" JSON date format?

I believe that the best format for universal interoperability is not the ISO-8601 string, but rather the format used by EJSON:

{ "myDateField": { "$date" : <ms-since-epoch> } }

As described here:


  1. Parsing performance: If you store dates as ISO-8601 strings, this is great if you are expecting a date value under that particular field, but if you have a system which must determine value types without context, you're parsing every string for a date format.
  2. No Need for Date Validation: You need not worry about validation and verification of the date. Even if a string matches ISO-8601 format, it may not be a real date; this can never happen with an EJSON date.
  3. Unambiguous Type Declaration: as far as generic data systems go, if you wanted to store an ISO string as a string in one case, and a real system date in another, generic systems adopting the ISO-8601 string format will not allow this, mechanically (without escape tricks or similar awful solutions).


I understand that a human-readable format (ISO-8601 string) is helpful and more convenient for 80% of use cases, and indeed no-one should ever be told not to store their dates as ISO-8601 strings if that's what their applications understand, but for a universally accepted transport format which should guarantee certain values to for sure be dates, how can we allow for ambiguity and need for so much validation?

Running sites on "localhost" is extremely slow

If you are just viewing the page output (not debugging code) then go to the Web.Config file and set debug to false. This changes load time from >15 secs to <1 sec

        <compilation debug="false" strict="false" explicit="true" targetFramework="4.0" />

HTML5 form required attribute. Set custom validation message?

Here is the code to handle custom error message in HTML5:

<input type="text" id="username" required placeholder="Enter Name"
  oninvalid="this.setCustomValidity('Enter User Name Here')"

This part is important because it hides the error message when the user inputs new data:


Toggle input disabled attribute using jQuery

Another simple option that updates on a click of the checkbox.


<input type="checkbox" id="checkbox/>
<input disabled type="submit" id="item"/>


$('#checkbox').click(function() {
    if (this.checked) {
        $('#item').prop('disabled', false); // If checked enable item       
    } else {
        $('#item').prop('disabled', true); // If checked disable item                   

In action: link

What is the difference between ExecuteScalar, ExecuteReader and ExecuteNonQuery?

Each one is a different type execution.

  • ExecuteScalar is going to be the type of query which will be returning a single value.

    An example would be returning a generated id after inserting.

    INSERT INTO my_profile (Address) VALUES ('123 Fake St.'); SELECT CAST(scope_identity() AS int)

  • ExecuteReader gives you a data reader back which will allow you to read all of the columns of the results a row at a time.

    An example would be pulling profile information for one or more users.

    SELECT * FROM my_profile WHERE id = '123456'

  • ExecuteNonQuery is any SQL which isn't returning values, but is actually performing some form of work like inserting deleting or modifying something.

    An example would be updating a user's profile in the database.

    UPDATE my_profile SET Address = '123 Fake St.' WHERE id = '123456'

Best way to define error codes/strings in Java?

At my last job I went a little deeper in the enum version:

public enum Messages {
    @Text("You can''t put a {0} in a {1}")

@Error, @Info, @Warning are retained in the class file and are available at runtime. (We had a couple of other annotations to help describe message delivery as well)

@Text is a compile-time annotation.

I wrote an annotation processor for this that did the following:

  • Verify that there are no duplicate message numbers (the part before the first underscore)
  • Syntax-check the message text
  • Generate a file that contains the text, keyed by the enum value.

I wrote a few utility routines that helped log errors, wrap them as exceptions (if desired) and so forth.

I'm trying to get them to let me open-source it... -- Scott

What does EntityManager.flush do and why do I need to use it?

EntityManager.persist() makes an entity persistent whereas EntityManager.flush() actually runs the query on your database.

So, when you call EntityManager.flush(), queries for inserting/updating/deleting associated entities are executed in the database. Any constraint failures (column width, data types, foreign key) will be known at this time.

The concrete behaviour depends on whether flush-mode is AUTO or COMMIT.

Finding the mode of a list

import numpy as np
def get_mode(xs):
    values, counts = np.unique(xs, return_counts=True)
    max_count_index = np.argmax(counts) #return the index with max value counts
    return values[max_count_index]

Regular vs Context Free Grammars

a regular grammer is never ambiguous because it is either left linear or right linear so we cant make two decision tree for regular grammer so it is always unambiguous.but othert than regular grammar all are may or may not be regular

How can I have linebreaks in my long LaTeX equations?

This worked for me while using mathtools package.

            first term \\
            second term                 

Calling async method on button click

You're the victim of the classic deadlock. task.Wait() or task.Result is a blocking call in UI thread which causes the deadlock.

Don't block in the UI thread. Never do it. Just await it.

private async void Button_Click(object sender, RoutedEventArgs 
      var task = GetResponseAsync<MyObject>("my url");
      var items = await task;

Btw, why are you catching the WebException and throwing it back? It would be better if you simply don't catch it. Both are same.

Also I can see you're mixing the asynchronous code with synchronous code inside the GetResponse method. StreamReader.ReadToEnd is a blocking call --you should be using StreamReader.ReadToEndAsync.

Also use "Async" suffix to methods which returns a Task or asynchronous to follow the TAP("Task based Asynchronous Pattern") convention as Jon says.

Your method should look something like the following when you've addressed all the above concerns.

public static async Task<List<T>> GetResponseAsync<T>(string url)
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
    var response = (HttpWebResponse)await Task.Factory.FromAsync<WebResponse>(request.BeginGetResponse, request.EndGetResponse, null);

    Stream stream = response.GetResponseStream();
    StreamReader strReader = new StreamReader(stream);
    string text = await strReader.ReadToEndAsync();

    return JsonConvert.DeserializeObject<List<T>>(text);

check if directory exists and delete in one command unix

Why not just use rm -rf /some/dir? That will remove the directory if it's present, otherwise do nothing. Unlike rm -r /some/dir this flavor of the command won't crash if the folder doesn't exist.

UITableView with fixed section headers

Swift 3.0

Create a ViewController with the UITableViewDelegate and UITableViewDataSource protocols. Then create a tableView inside it, declaring its style to be UITableViewStyle.grouped. This will fix the headers.

lazy var tableView: UITableView = {
    let view = UITableView(frame: UIScreen.main.bounds, style: UITableViewStyle.grouped)
    view.delegate = self
    view.dataSource = self
    view.separatorStyle = .none
    return view

How to convert String object to Boolean Object?

Well, as now in Jan, 2018, the best way for this is to use apache's BooleanUtils.toBoolean.

This will convert any boolean like string to boolean, e.g. Y, yes, true, N, no, false, etc.

Really handy!

How to run python script with elevated privilege on windows

It worth mentioning that if you intend to package your application with PyInstaller and wise to avoid supporting that feature by yourself, you can pass the --uac-admin or --uac-uiaccess argument in order to request UAC elevation on start.

Days between two dates?

Do you mean full calendar days, or groups of 24 hours?

For simply 24 hours, assuming you're using Python's datetime, then the timedelta object already has a days property:

days = (a - b).days

For calendar days, you'll need to round a down to the nearest day, and b up to the nearest day, getting rid of the partial day on either side:

roundedA = a.replace(hour = 0, minute = 0, second = 0, microsecond = 0)
roundedB = b.replace(hour = 0, minute = 0, second = 0, microsecond = 0)
days = (roundedA - roundedB).days

jQuery Validation plugin: disable validation for specified submit buttons

You can add a CSS class of cancel to a submit button to suppress the validation


<input class="cancel" type="submit" value="Save" />

See the jQuery Validator documentation of this feature here: Skipping validation on submit


The above technique has been deprecated and replaced with the formnovalidate attribute.

<input formnovalidate="formnovalidate" type="submit" value="Save" />

Angular 2 select option (dropdown) - how to get the value on change so it can be used in a function?

Another solution would be,you can get the object itself as value if you are not mentioning it's id as value: Note: [value] and [ngValue] both works here.

<select (change)="your_method(values[$])">
  <option *ngFor="let v of values" [value]="v" >  

In ts:

  //access values here as needed. 
  // or

Note: If you are using reactive form and you want to catch selected value on form Submit, you should use [ngValue] directive instead of [value] in above scanerio


  <select (change)="your_method(values[$])" formControlName="form_control_name">
      <option *ngFor="let v of values" [ngValue]="v" >  

In ts:

        let v : any = this.form_group_name.value.form_control_name;  

Defining custom attrs

The traditional approach is full of boilerplate code and clumsy resource handling. That's why I made the Spyglass framework. To demonstrate how it works, here's an example showing how to make a custom view that displays a String title.

Step 1: Create a custom view class.

public class CustomView extends FrameLayout {
    private TextView titleView;

    public CustomView(Context context) {
        init(null, 0, 0);

    public CustomView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs, 0, 0);

    public CustomView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(attrs, defStyleAttr, 0);

    public CustomView(
            Context context, 
            AttributeSet attrs,
            int defStyleAttr,
            int defStyleRes) {

        super(context, attrs, defStyleAttr, defStyleRes);
        init(attrs, defStyleAttr, defStyleRes);

    public void setTitle(String title) {

    private void init(AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        inflate(getContext(), R.layout.custom_view, this);

        titleView = findViewById(;

Step 2: Define a string attribute in the values/attrs.xml resource file:

    <declare-styleable name="CustomView">
        <attr name="title" format="string"/>

Step 3: Apply the @StringHandler annotation to the setTitle method to tell the Spyglass framework to route the attribute value to this method when the view is inflated.

@HandlesString(attributeId = R.styleable.CustomView_title)
public void setTitle(String title) {

Now that your class has a Spyglass annotation, the Spyglass framework will detect it at compile-time and automatically generate the CustomView_SpyglassCompanion class.

Step 4: Use the generated class in the custom view's init method:

private void init(AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    inflate(getContext(), R.layout.custom_view, this);

    titleView = findViewById(;


That's it. Now when you instantiate the class from XML, the Spyglass companion interprets the attributes and makes the required method call. For example, if we inflate the following layout then setTitle will be called with "Hello, World!" as the argument.


        app:title="Hello, World!"/>

The framework isn't limited to string resources has lots of different annotations for handling other resource types. It also has annotations for defining default values and for passing in placeholder values if your methods have multiple parameters.

Have a look at the Github repo for more information and examples.


I think that parse_str is what you're looking for, something like this should do the trick for you:

parse_str($_SERVER['QUERY_STRING'], $vars);

Then the $vars array will hold all the passed arguments.

I want to multiply two columns in a pandas DataFrame and add the result into a new column

To make things neat, I take Hayden's solution but make a small function out of it.

def create_value(row):
    if row['Action'] == 'Sell':
        return row['Prices'] * row['Amount']
        return -row['Prices']*row['Amount']

so that when we want to apply the function to our dataframe, we can do..

df['Value'] = df.apply(lambda row: create_value(row), axis=1)

...and any modifications only need to occur in the small function itself.

Concise, Readable, and Neat!

What is the purpose of class methods?

@classmethod can be useful for easily instantiating objects of that class from outside resources. Consider the following:

import settings

class SomeClass:
    def from_settings(cls):
        return cls(settings=settings)

    def __init__(self, settings=None):
        if settings is not None:
            self.x = settings['x']
            self.y = settings['y']

Then in another file:

from some_package import SomeClass

inst = SomeClass.from_settings()

Accessing inst.x will give the same value as settings['x'].

How to calculate number of days between two given dates?

There is also a datetime.toordinal() method that was not mentioned yet:

import datetime
print(,9,26).toordinal() -,8,18).toordinal())  # 39


Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any date object d, date.fromordinal(d.toordinal()) == d.

Seems well suited for calculating days difference, though not as readable as timedelta.days.

SQL Server r2 installation error .. update Visual Studio 2008 to SP1

I used the Visual Studio 2008 Uninstall tool and it worked fine for me.

You can use this tool to uninstall Visual Studio 2008 official release and Visual Studio 2008 Release candidate (Only English version).

Found here, on the MSDN Forum: MSDN forum topic.

I found this answer here

Be sure you run the tool with admin-rights.

How can getContentResolver() be called in Android?

  //create activity object to get activity from Activity class for use to content resolver
    private final Activity ActivityObj;

  //create constructor with ActivityObj to get activity from Activity class
    public RecyclerViewAdapterClass(Activity activityObj) {
        this.ActivityObj = activityObj;


Check if date is a valid one

I just found a really messed up case.

moment('Decimal128', 'YYYY-MM-DD').isValid() // true

How to transfer data from JSP to servlet when submitting HTML form

Well, there are plenty of database tutorials online for java (what you're looking for is called JDBC). But if you are using plain servlets, you will have a class that extends HttpServlet and inside it you will have two methods that look like

public void doPost(HttpServletRequest req, HttpServletResponse resp){



public void doGet(HttpServletRequest req, HttpServletResponse resp){


One of them is called to handle GET operations and another is used to handle POST operations. You will then use the HttpServletRequest object to get the parameters that were passed as part of the form like so:

String name = req.getParameter("name");

Then, once you have the data from the form, it's relatively easy to add it to a database using a JDBC tutorial that is widely available on the web. I also suggest searching for a basic Java servlet tutorial to get you started. It's very easy, although there are a number of steps that need to be configured correctly.

using stored procedure in entity framework

Mindless passenger has a project that allows you to call a stored proc from entity frame work like this....

using (testentities te = new testentities())
    // Simple stored proc
    var parms1 = new testone() { inparm = "abcd" };
    var results1 = te.CallStoredProc<testone>(te.testoneproc, parms1);
    var r1 = results1.ToList<TestOneResultSet>();

... and I am working on a stored procedure framework (here) which you can call like in one of my test methods shown below...

public class TenantDataBasedTests : BaseIntegrationTest
    public void GetTenantForName_ReturnsOneRecord()
        // ARRANGE
        const int expectedCount = 1;
        const string expectedName = "Me";

        // Build the paraemeters object
        var parameters = new GetTenantForTenantNameParameters
            TenantName = expectedName

        // get an instance of the stored procedure passing the parameters
        var procedure = new GetTenantForTenantNameProcedure(parameters);

        // Initialise the procedure name and schema from procedure attributes

        // Add some tenants to context so we have something for the procedure to return!

        // ACT
        // Get the results by calling the stored procedure from the context extention method 
        var results = Context.ExecuteStoredProcedure(procedure);

        // ASSERT
        Assert.AreEqual(expectedCount, results.Count);

internal class GetTenantForTenantNameParameters
    public string TenantName { get; set; }

internal class GetTenantForTenantNameProcedure
    : StoredProcedureBase<TenantResultRow, GetTenantForTenantNameParameters>
    public GetTenantForTenantNameProcedure(
        GetTenantForTenantNameParameters parameters)
        : base(parameters)

If either of those two approaches are any good?

How do I copy the contents of one ArrayList into another?

Came across this while facing the same issue myself.

Saying arraylist1 = arraylist2 sets them both to point at the same place so if you alter either the data alters and thus both lists always stay the same.

To copy values into an independent list I just used foreach to copy the contents:

ArrayList list1 = new ArrayList();
ArrayList list2 = new ArrayList();

fill list1 in whatever way you currently are.

foreach(<type> obj in list1)

JVM option -Xss - What does it do exactly?

Each thread in a Java application has its own stack. The stack is used to hold return addresses, function/method call arguments, etc. So if a thread tends to process large structures via recursive algorithms, it may need a large stack for all those return addresses and such. With the Sun JVM, you can set that size via that parameter.

MyISAM versus InnoDB

I think this is an excellent article on explaining the differences and when you should use one over the other:

415 Unsupported Media Type - POST json to OData service in lightswitch 2012

It looks like this issue has to do with the difference between the Content-Type and Accept headers. In HTTP, Content-Type is used in request and response payloads to convey the media type of the current payload. Accept is used in request payloads to say what media types the server may use in the response payload.

So, having a Content-Type in a request without a body (like your GET request) has no meaning. When you do a POST request, you are sending a message body, so the Content-Type does matter.

If a server is not able to process the Content-Type of the request, it will return a 415 HTTP error. (If a server is not able to satisfy any of the media types in the request Accept header, it will return a 406 error.)

In OData v3, the media type "application/json" is interpreted to mean the new JSON format ("JSON light"). If the server does not support reading JSON light, it will throw a 415 error when it sees that the incoming request is JSON light. In your payload, your request body is verbose JSON, not JSON light, so the server should be able to process your request. It just doesn't because it sees the JSON light content type.

You could fix this in one of two ways:

  1. Make the Content-Type "application/json;odata=verbose" in your POST request, or
  2. Include the DataServiceVersion header in the request and set it be less than v3. For example:

    DataServiceVersion: 2.0;

(Option 2 assumes that you aren't using any v3 features in your request payload.)

Get input value from TextField in iOS alert in Swift

Updated for Swift 3 and above:

//1. Create the alert controller.
let alert = UIAlertController(title: "Some Title", message: "Enter a text", preferredStyle: .alert)

//2. Add the text field. You can configure it however you need.
alert.addTextField { (textField) in
    textField.text = "Some default text"

// 3. Grab the value from the text field, and print it when the user clicks OK.
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { [weak alert] (_) in
    let textField = alert.textFields![0] // Force unwrapping because we know it exists.
    print("Text field: \(textField.text)")

// 4. Present the alert.
self.present(alert, animated: true, completion: nil)

Swift 2.x

Assuming you want an action alert on iOS:

//1. Create the alert controller.            
var alert = UIAlertController(title: "Some Title", message: "Enter a text", preferredStyle: .Alert)

//2. Add the text field. You can configure it however you need.
alert.addTextFieldWithConfigurationHandler({ (textField) -> Void in
    textField.text = "Some default text."

//3. Grab the value from the text field, and print it when the user clicks OK. 
alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { [weak alert] (action) -> Void in
    let textField = alert.textFields![0] as UITextField
    println("Text field: \(textField.text)")

// 4. Present the alert.
self.presentViewController(alert, animated: true, completion: nil)

Python object.__repr__(self) should be an expression?

"but does that mean it should just be an example of the sort of expression you could use, or should it be an actual expression, that can be executed (eval etc..) to recreate the object? Or... should it be just a rehasing of the actual expression which was used, for pure information purposes?"

Wow, that's a lot of hand-wringing.

  1. An "an example of the sort of expression you could use" would not be a representation of a specific object. That can't be useful or meaningful.

  2. What is the difference between "an actual expression, that can ... recreate the object" and "a rehasing of the actual expression which was used [to create the object]"? Both are an expression that creates the object. There's no practical distinction between these. A repr call could produce either a new expression or the original expression. In many cases, they're the same.

Note that this isn't always possible, practical or desirable.

In some cases, you'll notice that repr() presents a string which is clearly not an expression of any kind. The default repr() for any class you define isn't useful as an expression.

In some cases, you might have mutual (or circular) references between objects. The repr() of that tangled hierarchy can't make sense.

In many cases, an object is built incrementally via a parser. For example, from XML or JSON or something. What would the repr be? The original XML or JSON? Clearly not, since they're not Python. It could be some Python expression that generated the XML. However, for a gigantic XML document, it might not be possible to write a single Python expression that was the functional equivalent of parsing XML.

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

Procedures: 1.Procedures are the collections of statements that defines parameterized computations. 2.Procedures cannot return values.

3.Procedures cannot be called from function.

Functions 1.Functions structurally resemble procedures but are semantically modeled on mathematical functions. 2.It can return values 3.Function can be called from procedures.

returning a Void object

The Void class is an uninstantiable placeholder class to hold a reference to the Class object representing the Java keyword void.

So any of the following would suffice:

  • parameterizing with Object and returning new Object() or null
  • parameterizing with Void and returning null
  • parameterizing with a NullObject of yours

You can't make this method void, and anything else returns something. Since that something is ignored, you can return anything.

Function or sub to add new row and data to table

Minor variation of phillfri's answer which was already a variation of Geoff's answer: I added the ability to handle completely empty tables that contain no data for the Array Code.

Sub AddDataRow(tableName As String, NewData As Variant)
    Dim sheet As Worksheet
    Dim table As ListObject
    Dim col As Integer
    Dim lastRow As Range

    Set sheet = Range(tableName).Parent
    Set table = sheet.ListObjects.Item(tableName)

    'First check if the last row is empty; if not, add a row
    If table.ListRows.Count > 0 Then
        Set lastRow = table.ListRows(table.ListRows.Count).Range
        If Application.CountBlank(lastRow) < lastRow.Columns.Count Then
        End If
    End If

    'Iterate through the last row and populate it with the entries from values()
    If table.ListRows.Count = 0 Then 'If table is totally empty, set lastRow as first entry
        table.ListRows.Add Position:=1
        Set lastRow = table.ListRows(1).Range
        Set lastRow = table.ListRows(table.ListRows.Count).Range
    End If
    For col = 1 To lastRow.Columns.Count
        If col <= UBound(NewData) + 1 Then lastRow.Cells(1, col) = NewData(col - 1)
    Next col
End Sub

Removing html5 required attribute with jQuery

Using Javascript:

document.querySelector('#edit-submitted-first-name').required = false;

Using jQuery:


How to call any method asynchronously in c#

Starting with .Net 4.5 you can use Task.Run to simply start an action:

void Foo(string args){}
Task.Run(() => Foo("bar"));

Task.Run vs Task.Factory.StartNew

How to include a PHP variable inside a MySQL statement

That's the easy answer:

$query="SELECT * FROM CountryInfo WHERE Name = '".$name."'";

and you define $name whatever you want.
And another way, the complex way, is like that:

$query = " SELECT '" . $GLOBALS['Name'] . "' .* " .
         " FROM CountryInfo " .
         " INNER JOIN District " .
         " ON District.CountryInfoId = CountryInfo.CountryInfoId " .
         " INNER JOIN City " .
         " ON City.DistrictId = District.DistrictId " .
         " INNER JOIN '" . $GLOBALS['Name'] . "' " .
         " ON '" . $GLOBALS['Name'] . "'.CityId = City.CityId " .
         " WHERE CountryInfo.Name = '" . $GLOBALS['CountryName'] .

how to configure lombok in eclipse luna

I have met with the exact same problem. And it turns out that the configuration file generated by gradle asks for java1.7.
While my system has java1.8 installed.

After modifying the compiler compliance level to 1.8. All things are working as expected.

What's onCreate(Bundle savedInstanceState)

As Dhruv Gairola answered, you can save the state of the application by using Bundle savedInstanceState. I am trying to give a very simple example that new learners like me can understand easily.

Suppose, you have a simple fragment with a TextView and a Button. Each time you clicked the button the text changes. Now, change the orientation of you device/emulator and notice that you lost the data (means the changed data after clicking you got) and fragment starts as the first time again. By using Bundle savedInstanceState we can get rid of this. If you take a look into the life cyle of the fragment.Fragment Lifecylce you will get that a method "onSaveInstanceState" is called when the fragment is about to destroyed.

So, we can save the state means the changed text value into that bundle like this

 int counter  = 0;
 public void onSaveInstanceState(Bundle outState) {

After you make the orientation the "onCreate" method will be called right? so we can just do this

public void onCreate(Bundle savedInstanceState) {

    if(savedInstanceState == null){
        //it is the first time the fragment is being called
        counter = 0;
        //not the first time so we will check SavedInstanceState bundle
        counter = savedInstanceState.getInt("value",0); //here zero is the default value

Now, you won't lose your value after the orientation. The modified value always will be displayed.

What is a callback URL in relation to an API?

It's a mechanism to invoke an API in an asynchrounous way. The sequence is the following

  1. your app invokes the url, passing as parameter the callback url
  2. the api respond with a 20x http code (201 I guess, but refer to the api docs)
  3. the api works on your request for a certain amount of time
  4. the api invokes your app to give you the results, at the callback url address.

So you can invoke the api and tell your user the request is "processing" or "acquired" for example, and then update the status when you receive the response from the api.

Hope it makes sense. -G

Compare two files report difference in python

import difflib
f=open('a.txt','r')  #open a file
f1=open('b.txt','r') #open another file to compare
str1=str1.split()  #split the words in file by default through the spce
d=difflib.Differ()     # compare and just print
print '\n'.join(diff)

How do I escape a single quote ( ' ) in JavaScript?

You should always consider what the browser will see by the end. In this case, it will see this:

<img src='something' onmouseover='change(' ex1')' />

In other words, the "onmouseover" attribute is just change(, and there's another "attribute" called ex1')' with no value.

The truth is, HTML does not use \ for an escape character. But it does recognise &quot; and &apos; as escaped quote and apostrophe, respectively.

Armed with this knowledge, use this:

document.getElementById("something").innerHTML = "<img src='something' onmouseover='change(&quot;ex1&quot;)' />";

... That being said, you could just use JavaScript quotes:

document.getElementById("something").innerHTML = "<img src='something' onmouseover='change(\"ex1\")' />";

Background color on input type=button :hover state sticks in IE

You need to make sure images come first and put in a comma after the background image call. then it actually does work:

    background:url(egg.png) no-repeat 70px 2px #82d4fe; /* Old browsers */
background:url(egg.png) no-repeat 70px 2px, -moz-linear-gradient(top, #82d4fe 0%, #1db2ff 78%) ; /* FF3.6+ */
background:url(egg.png) no-repeat 70px 2px, -webkit-gradient(linear, left top, left bottom, color-stop(0%,#82d4fe), color-stop(78%,#1db2ff)); /* Chrome,Safari4+ */
background:url(egg.png) no-repeat 70px 2px, -webkit-linear-gradient(top, #82d4fe 0%,#1db2ff 78%); /* Chrome10+,Safari5.1+ */
background:url(egg.png) no-repeat 70px 2px, -o-linear-gradient(top, #82d4fe 0%,#1db2ff 78%); /* Opera11.10+ */
background:url(egg.png) no-repeat 70px 2px, -ms-linear-gradient(top, #82d4fe 0%,#1db2ff 78%); /* IE10+ */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#82d4fe', endColorstr='#1db2ff',GradientType=0 ); /* IE6-9 */
background:url(egg.png) no-repeat 70px 2px, linear-gradient(top, #82d4fe 0%,#1db2ff 78%); /* W3C */

How to make a flex item not fill the height of the flex container?

The align-items, or respectively align-content attribute controls this behaviour.

align-items defines the items' positioning perpendicularly to flex-direction.

The default flex-direction is row, therfore vertical placement can be controlled with align-items.

There is also the align-self attribute to control the alignment on a per item basis.

#a {_x000D_
#a > div {_x000D_
 #a > #c {_x000D_
<div id="a">_x000D_
  <div id="b">left</div>_x000D_
  <div id="c">middle</div>_x000D_

css-tricks has an excellent article on the topic. I recommend reading it a couple of times.

SQL Server 2012 column identity increment jumping from 6 to 1000+ on 7th entry

Got the same problem, found the following bug report in SQL Server 2012 If still relevant see conditions that cause the issue - there are some workarounds there as well (didn't try though). Failover or Restart Results in Reseed of Identity

laravel the requested url was not found on this server

This looks like you have to enable .htaccess by adding this to your vhost:

<Directory /var/www/html/public/>
    Options Indexes FollowSymLinks
    AllowOverride All
    Require all granted

If that doesn't work, make sure you have mod_rewrite enabled.

Don't forget to restart apache after making the changes! (service apache2 restart)

What port is a given program using?

On Vista, you do need elevated privileges to use the -b option with netstat. To get around that, you could run "netstat -ano" which will show all open ports along with the associated process id. You could then use tasklist to lookup which process has the corresponding id.

C:\>netstat -ano

Active Connections

  Proto  Local Address          Foreign Address        State           PID
  TCP    [::]:49335             [::]:0                 LISTENING       1056

C:\>tasklist /fi "pid eq 1056"

Image Name                     PID Session Name        Session#    Mem Usage
========================= ======== ================ =========== ============
sqlservr.exe                  1056 Services                   0     66,192 K

Difference between webdriver.Dispose(), .Close() and .Quit()

close() is a webdriver command which closes the browser window which is currently in focus. Despite the familiar name for this method, WebDriver does not implement the AutoCloseable interface.

During the automation process, if there are more than one browser window opened, then the close() command will close only the current browser window which is having focus at that time. The remaining browser windows will not be closed. The following code can be used to close the current browser window:

quit() is a webdriver command which calls the driver.dispose method, which in turn closes all the browser windows and terminates the WebDriver session. If we do not use quit() at the end of program, the WebDriver session will not be closed properly and the files will not be cleared off memory. This may result in memory leak errors.

If the Automation process opens only a single browser window, the close() and quit() commands work in the same way. Both will differ in their functionality when there are more than one browser window opened during Automation.

For Above Ref : click here

Dispose Command Dispose() should call Quit(), and it appears it does. However, it also has the same problem in that any subsequent actions are blocked until PhantomJS is manually closed.

Ref Link

How do you specify a debugger program in Code::Blocks 12.11?

For Code::Blocks 17.12.

  1. Visit

  2. Follow installation's instructions.

  3. Alternatively I suggest this post.


Insert current date into a date column using T-SQL?

Couple of ways. Firstly, if you're adding a row each time a [de]activation occurs, you can set the column default to GETDATE() and not set the value in the insert. Otherwise,

UPDATE TableName SET [ColumnName] = GETDATE() WHERE UserId = @userId

Usage of the backtick character (`) in JavaScript

ECMAScript 6 comes up with a new type of string literal, using the backtick as the delimiter. These literals do allow basic string interpolation expressions to be embedded, which are then automatically parsed and evaluated.

let person = {name: 'RajiniKanth', age: 68, greeting: 'Thalaivaaaa!' };

let usualHtmlStr = "<p>My name is " + + ",</p>\n" +
  "<p>I am " + person.age + " old</p>\n" +
  "<strong>\"" + person.greeting + "\" is what I usually say</strong>";

let newHtmlStr =
 `<p>My name is ${},</p>
  <p>I am ${person.age} old</p>
  <p>"${person.greeting}" is what I usually say</strong>`;


As you can see, we used the ` around a series of characters, which are interpreted as a string literal, but any expressions of the form ${..} are parsed and evaluated inline immediately.

One really nice benefit of interpolated string literals is they are allowed to split across multiple lines:

var Actor = {"name": "RajiniKanth"};

var text =
`Now is the time for all good men like ${}
to come to the aid of their
// Now is the time for all good men like RajiniKanth
// to come to the aid of their
// country!

Interpolated Expressions

Any valid expression is allowed to appear inside ${..} in an interpolated string literal, including function calls, inline function expression calls, and even other interpolated string literals!

function upper(s) {
  return s.toUpperCase();
var who = "reader"
var text =
`A very ${upper("warm")} welcome
to all of you ${upper(`${who}s`)}!`;
// A very WARM welcome
// to all of you READERS!

Here, the inner `${who}s` interpolated string literal was a little bit nicer convenience for us when combining the who variable with the "s" string, as opposed to who + "s". Also to keep an note is an interpolated string literal is just lexically scoped where it appears, not dynamically scoped in any way:

function foo(str) {
  var name = "foo";
function bar() {
  var name = "bar";
  foo(`Hello from ${name}!`);
var name = "global";
bar(); // "Hello from bar!"

Using the template literal for the HTML is definitely more readable by reducing the annoyance.

The plain old way:

'<div class="' + className + '">' +
  '<p>' + content + '</p>' +
  '<a href="' + link + '">Let\'s go</a>'

With ECMAScript 6:

`<div class="${className}">
  <a href="${link}">Let's go</a>
  • Your string can span multiple lines.
  • You don't have to escape quotation characters.
  • You can avoid groupings like: '">'
  • You don't have to use the plus operator.

Tagged Template Literals

We can also tag a template string, when a template string is tagged, the literals and substitutions are passed to function which returns the resulting value.

function myTaggedLiteral(strings) {

myTaggedLiteral`test`; //["test"]

function myTaggedLiteral(strings, value, value2) {
  console.log(strings, value, value2);
let someText = 'Neat';
myTaggedLiteral`test ${someText} ${2 + 3}`;
//["test", ""]
// "Neat"
// 5

We can use the spread operator here to pass multiple values. The first argument—we called it strings—is an array of all the plain strings (the stuff between any interpolated expressions).

We then gather up all subsequent arguments into an array called values using the ... gather/rest operator, though you could of course have left them as individual named parameters following the strings parameter like we did above (value1, value2, etc.).

function myTaggedLiteral(strings, ...values) {

let someText = 'Neat';
myTaggedLiteral`test ${someText} ${2 + 3}`;
//["test", ""]
// "Neat"
// 5

The argument(s) gathered into our values array are the results of the already evaluated interpolation expressions found in the string literal. A tagged string literal is like a processing step after the interpolations are evaluated, but before the final string value is compiled, allowing you more control over generating the string from the literal. Let's look at an example of creating reusable templates.

const Actor = {
  name: "RajiniKanth",
  store: "Landmark"

const ActorTemplate = templater`<article>
  <h3>${'name'} is a Actor</h3>
  <p>You can find his movies at ${'store'}.</p>


function templater(strings, ...keys) {
  return function(data) {
    let temp = strings.slice();
    keys.forEach((key, i) => {
      temp[i] = temp[i] + data[key];
    return temp.join('');

const myTemplate = ActorTemplate(Actor);

Raw Strings

Our tag functions receive a first argument we called strings, which is an array. But there’s an additional bit of data included: the raw unprocessed versions of all the strings. You can access those raw string values using the .raw property, like this:

function showraw(strings, ...values) {

As you can see, the raw version of the string preserves the escaped \n sequence, while the processed version of the string treats it like an unescaped real new-line. ECMAScript 6 comes with a built-in function that can be used as a string literal tag: String.raw(..). It simply passes through the raw versions of the strings:

/* "Hello
World" */

// "Hello\nWorld"

How to directly initialize a HashMap (in a literal way)?

Map<String,String> test = new HashMap<String, String>()
        put(key1, value1);
        put(key2, value2);

How to upload a file from Windows machine to Linux machine using command lines via PuTTy?

Pscp.exe is painfully slow.

Uploading files using WinSCP is like 10 times faster.

So, to do that from command line, first you got to add the file to your %PATH%. It's not a top-level domain, but an executable .com file, which is located in your WinSCP installation directory.

Then just issue a simple command and your file will be uploaded much faster putty ever could: /command "open sftp://username:[email protected]:22" "put /var/www/somedirectory/" "exit"

And make sure your check the synchronize folders feature, which is basically what rsync does, so you won't ever want to use pscp.exe again. /command "help synchronize"

How do I combine two dataframes?

You can also use pd.concat, which is particularly helpful when you are joining more than two dataframes:

bigdata = pd.concat([data1, data2], ignore_index=True, sort=False)

Unable to create/open lock file: /data/mongod.lock errno:13 Permission denied

I had the same problem.

I solved it by changing selinux status to permissive with below command:

setenforce 0

CSS: Truncate table cells, but fit as much as possible

I had the same issue, but I needed to display multiple lines (where text-overflow: ellipsis; fails). I solve it using a textarea inside a TD and then style it to behave like a table cell.

    textarea {
        margin: 0;
        padding: 0;
        width: 100%;
        border: none;
        resize: none;

        /* Remove blinking cursor (text caret) */
        color: transparent;
        display: inline-block;
        text-shadow: 0 0 0 black; /* text color is set to transparent so use text shadow to draw the text */
        &:focus {
            outline: none;

Eclipse Bug: Unhandled event loop exception No more handles

in short: check out if the bold sections below may save your day :-)

(This answer may help but the source problem is still not found. I'll update my findings if satisfyingly solved.)


update: It just happened again and occurred on dragging/positioning of one XML file (Tomcats content.xml) underneath all other files. (Opened by "XML Editor": Provider: Eclipse Web Tools Platform, Plug-in Name: XML editor, Version: 1.0.700.v201005192212, Plug-in Id: org.eclipse.wst.xmleditor.doc.user)

update2: On further looking into it the error disappears when I move the editor back to the other files (all open editors in one area). Furthermore it appears only when entering or leaving this XML editor, not on e.g. making changes to it and saving it via CRTL+S. Other than that the JBoss-related exception from below occurs on the CTRL+S event, but independent of this issue (so it may not be related at all).

update3: Getting even closer: since some time there has been a new editor positioning feature around. (Initially I was a bit confused, but now I am getting the point and even visually can see what is meant and what makes the difference...). So there are two ways to position editors vertically or horizontally next to other editors:

  1. positioning it inside the same "panel" (indicated by a global and two inner panels/borders/rectangles around the editors) and
  2. positing it next to the old "panel" (indicated by a rectangle frame around the old panel and the new one.

So putting an editor in a new "global" panel (2.) works fine, putting it in a new "local" panel (1.) causes the issue (that's actually very helpful because I can still continue to work quite efficiently) (maybe somebody else could report this bug appropriately) (it also seems not related to the XML editor mentioned above since it also happens e.g. on property files)

update 4: I am using Windows 7 in hibernate mode. Meaning I don't start my Eclipse too often. Now I realized that Eclipse itself had been started (looking at the Task Manager) 2 times (visually and using ALT+TAB for open windows navigation this was not obvious). After (stopping/killing all open instances and) restarting the problem does not occur anymore.

update 5: In this duplicate question somebody stated it would have been solved by the latest windows update: . I'll check this out for myself, but currently I cannot reproduce the problem anyways.

update 6: In another situation I had this and it seemed related to some property window (in this case Jasper Reports) that updated its content automatically, based on the current editor (like an outline view). So it could be a good idea to close and re-open (all) outline and/or property windows.


The error in general indicates, that some program(s) have (propably) unusually many (probably thousands?) of operating system file handles open. So one should check if outside or inside of Eclipse a lot of files are opened at the same time or opened over a short period of time, but not properly closed (they could be visually closed, but the operating system still thinks they are beeing used because the application did not properly free the file handles somehow).

Now I have this issue currently as well. If I look in the Error Log (Window->Show View->General->Error Log) I can see a lot of the following org.jboss.ide.eclipse.archives.core.* exceptions immediately before. Since I don't use the installed JBoss Developer Studio Plugin (that is likely related to this one) right now and no associated window or editor is opened (only some toolbar "JBoss Central" and perspective "JBoss" buttons) I'll have a look if disabling these will help on this sporadic problem. Also I closed all open editors, restarted Eclipse and open them and can't see this issue right now again.

Problems occurred when invoking code from plug-in: "org.eclipse.core.resources".


    at org.jboss.ide.eclipse.archives.core.WorkspaceChangeListener$2.visit(
    at org.jboss.ide.eclipse.archives.core.WorkspaceChangeListener.resourceChanged(
    at org.eclipse.core.internal.resources.Workspace.broadcastPostChange(
    at org.eclipse.core.internal.resources.Workspace.endOperation(
    at org.eclipse.ui.editors.text.TextFileDocumentProvider.executeOperation(
    at org.eclipse.ui.editors.text.TextFileDocumentProvider.saveDocument(
    at org.eclipse.ui.texteditor.AbstractTextEditor.performSave(
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.ui.internal.SaveableHelper$
    at org.eclipse.ui.internal.SaveableHelper$
    at org.eclipse.jface.operation.ModalContext.runInCurrentThread(
    at org.eclipse.ui.internal.WorkbenchWindow$
    at org.eclipse.swt.custom.BusyIndicator.showWhile(
    at org.eclipse.ui.internal.SaveableHelper.runProgressMonitorOperation(
    at org.eclipse.ui.internal.SaveableHelper.runProgressMonitorOperation(
    at org.eclipse.ui.internal.SaveableHelper.savePart(
    at org.eclipse.ui.internal.WorkbenchPage.saveSaveable(
    at org.eclipse.ui.internal.WorkbenchPage.saveEditor(
    at org.eclipse.jface.action.Action.runWithEvent(
    at org.eclipse.jface.commands.ActionHandler.execute(
    at org.eclipse.ui.internal.handlers.E4HandlerProxy.execute(
    at sun.reflect.GeneratedMethodAccessor58.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.e4.core.internal.di.MethodRequestor.execute(
    at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(
    at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(
    at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(
    at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.execute(
    at org.eclipse.core.commands.Command.executeWithChecks(
    at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(
    at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(
    at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.executeCommand(
    at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.processKeyEvent(
    at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.filterKeySequenceBindings(
    at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.access$0(
    at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher$KeyDownFilter.handleEvent(
    at org.eclipse.swt.widgets.EventTable.sendEvent(
    at org.eclipse.swt.widgets.Display.filterEvent(
    at org.eclipse.swt.widgets.Widget.sendEvent(
    at org.eclipse.swt.widgets.Widget.sendEvent(
    at org.eclipse.swt.widgets.Widget.sendEvent(
    at org.eclipse.swt.widgets.Widget.sendKeyEvent(
    at org.eclipse.swt.widgets.Widget.sendKeyEvent(
    at org.eclipse.swt.widgets.Widget.wmChar(
    at org.eclipse.swt.widgets.Control.WM_CHAR(
    at org.eclipse.swt.widgets.Canvas.WM_CHAR(
    at org.eclipse.swt.widgets.Control.windowProc(
    at org.eclipse.swt.widgets.Canvas.windowProc(
    at org.eclipse.swt.widgets.Display.windowProc(
    at org.eclipse.swt.internal.win32.OS.DispatchMessageW(Native Method)
    at org.eclipse.swt.internal.win32.OS.DispatchMessage(
    at org.eclipse.swt.widgets.Display.readAndDispatch(
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(
    at org.eclipse.ui.internal.Workbench$
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.equinox.launcher.Main.invokeFramework(
    at org.eclipse.equinox.launcher.Main.basicRun(
    at org.eclipse.equinox.launcher.Main.main(


java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=de_DE
Framework arguments:  -product org.eclipse.epp.package.reporting.product
Command-line arguments:  -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.reporting.product

installed plugins (Help->About Eclipse->Installation Details->Installed Software: mark all + CTRL+C): (Eclipse Kepler Java EE and BIRT edition as base install)

  Apache Directory Studio LDAP Browser  2.0.0.v20130628   Apache Software Foundation
  DevUtilsFeature   null
  Eclipse IDE for Java and Report Developers epp.package.reporting   null
  GlassFish Tools    Oracle
  JarPlug   0.6.1
  Jaspersoft Studio feature 5.2.0 Jaspersoft Corporation
  Java EE 5 Documentation    Oracle
  Java EE 6 Documentation    Oracle
  Java EE 7 Documentation    Oracle
  JBoss Developer Studio (Core Features)    7.0.0.GA-v20130720-0044-B364    JBoss by Red Hat
  Log Viewer Feature    Andre Bossert
  MercurialEclipse  MercurialEclipse project
  MyLV  1.0.4  null
  Oracle ADF Documentation (   Oracle
  Oracle ADF Documentation (   Oracle
  Oracle ADF Documentation (   Oracle
  Oracle ADF Documentation (   Oracle
  Oracle ADF Documentation (12.1.2)    Oracle
  Oracle ADF Tools  Oracle
  Oracle Cloud Tools    Oracle
  Oracle Coherence Tools    Oracle
  Oracle Database Tools Oracle
  Oracle Java EE Tools   Oracle
  Oracle Maven Tools    Oracle
  Oracle Spring Tools   Oracle
  Oracle WebLogic Scripting Tools   Oracle
  Oracle WebLogic Server Tools Oracle
  Toad® Extension for Eclipse - Community Edition - Core Plugin    Quest Software, Inc.
  Toad® Extension for Eclipse - Community Edition - MySQL DB Plugin   Quest Software, Inc.
  Toad® Extension for Eclipse - Community Edition - Oracle Database Plugin Quest Software, Inc.
  Toad® Extension for Eclipse - Community Edition - PostgreSQL Plugin Quest Software, Inc.                

Can't find System.Windows.Media namespace?

The System.Windows.Media.Imaging namespace is part of PresentationCore.dll (if you are using Visual Studio 2008 then the WPF application template will automatically add this reference). Note that this namespace is not a direct wrapping of the WIC library, although a large proportion of the more common uses are still available and it is relatively obvious how these map to the WIC versions. For more information on the classes in this namespace check out

The easiest way to replace white spaces with (underscores) _ in bash

This is borderline programming, but look into using tr:

$ echo "this is just a test" | tr -s ' ' | tr ' ' '_'

Should do it. The first invocation squeezes the spaces down, the second replaces with underscore. You probably need to add TABs and other whitespace characters, this is for spaces only.

Eclipse says: “Workspace in use or cannot be created, chose a different one.” How do I unlock a workspace?

i was faced this issue when ever the eclipse is not closed (kill eclipse process the from task manager or computer power off), i was tried below steps, it worked for me.

1) Remove the file names start with ".fileTable" from this folder


2) Remove the log files like text files start with numeric names from this folder


3) Open Command prompt(cmd) navigate to this folder


type below command

eclipse clean start

enter image description here

Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

@Before(JUnit4) -> @BeforeEach(JUnit5) - method is called before every test

@After(JUnit4) -> @AfterEach(JUnit5) - method is called after every test

@BeforeClass(JUnit4) -> @BeforeAll(JUnit5) - static method is called before executing all tests in this class. It can be a large task as starting server, read file, making db connection...

@AfterClass(JUnit4) -> @AfterAll(JUnit5) - static method is called after executing all tests in this class.

What is href="#" and why is it used?

Putting the "#" symbol as the href for something means that it points not to a different URL, but rather to another id or name tag on the same page. For example:

<a href="#bottomOfPage">Click to go to the bottom of the page</a>
blah blah
blah blah
<a id="bottomOfPage"></a>

However, if there is no id or name then it goes "no where."

Here's another similar question asked HTML Anchors with 'name' or 'id'?

JavaScript global event mechanism

Try Atatus which provides Advanced Error Tracking and Real User Monitoring for modern web apps.

Let me explain how to get stacktraces that are reasonably complete in all browsers.

Error handling in JavaScript

Modern Chrome and Opera fully support the HTML 5 draft spec for ErrorEvent and window.onerror. In both of these browsers you can either use window.onerror, or bind to the 'error' event properly:

// Only Chrome & Opera pass the error object.
window.onerror = function (message, file, line, col, error) {
    console.log(message, "from", error.stack);
    // You can send data to your server
    // sendError(data);
// Only Chrome & Opera have an error attribute on the event.
window.addEventListener("error", function (e) {
    console.log(e.error.message, "from", e.error.stack);
    // You can send data to your server
    // sendError(data);

Unfortunately Firefox, Safari and IE are still around and we have to support them too. As the stacktrace is not available in window.onerror we have to do a little bit more work.

It turns out that the only thing we can do to get stacktraces from errors is to wrap all of our code in a try{ }catch(e){ } block and then look at e.stack. We can make the process somewhat easier with a function called wrap that takes a function and returns a new function with good error handling.

function wrap(func) {
    // Ensure we only wrap the function once.
    if (!func._wrapped) {
        func._wrapped = function () {
                func.apply(this, arguments);
            } catch(e) {
                console.log(e.message, "from", e.stack);
                // You can send data to your server
                // sendError(data);
                throw e;
    return func._wrapped;

This works. Any function that you wrap manually will have good error handling, but it turns out that we can actually do it for you automatically in most cases.

By changing the global definition of addEventListener so that it automatically wraps the callback we can automatically insert try{ }catch(e){ } around most code. This lets existing code continue to work, but adds high-quality exception tracking.

var addEventListener = window.EventTarget.prototype.addEventListener;
window.EventTarget.prototype.addEventListener = function (event, callback, bubble) {, event, wrap(callback), bubble);

We also need to make sure that removeEventListener keeps working. At the moment it won't because the argument to addEventListener is changed. Again we only need to fix this on the prototype object:

var removeEventListener = window.EventTarget.prototype.removeEventListener;
window.EventTarget.prototype.removeEventListener = function (event, callback, bubble) {, event, callback._wrapped || callback, bubble);

Transmit error data to your backend

You can send error data using image tag as follows

function sendError(data) {
    var img = newImage(),
        src = '' + encodeURIComponent(JSON.stringify(data));

    img.crossOrigin = 'anonymous';
    img.onload = function success() {
        console.log('success', data);
    img.onerror = img.onabort = function failure() {
        console.error('failure', data);
    img.src = src;

Disclaimer: I am a web developer at

Choosing a jQuery datagrid plugin?

A good plugin that I have used before is DataTables.

What is the backslash character (\\)?

\ is used for escape sequences in programming languages.

\n prints a newline
\\ prints a backslash
\" prints "
\t prints a tabulator
\b moves the cursor one back

How to add ASP.NET 4.0 as Application Pool on IIS 7, Windows 7

Chances are you need to install .NET 4 (Which will also create a new AppPool for you)

First make sure you have IIS installed then perform the following steps:

  1. Open your command prompt (Windows + R) and type cmd and press ENTER
    You may need to start this as an administrator if you have UAC enabled.
    To do so, locate the exe (usually you can start typing with Start Menu open), right click and select "Run as Administrator"
  2. Type cd C:\Windows\Microsoft.NET\Framework\v4.0.30319\ and press ENTER.
  3. Type aspnet_regiis.exe -ir and press ENTER again.
    • If this is a fresh version of IIS (no other sites running on it) or you're not worried about the hosted sites breaking with a framework change you can use -i instead of -ir. This will change their AppPools for you and steps 5-on shouldn't be necessary.
    • at this point you will see it begin working on installing .NET's framework in to IIS for you
  4. Close the DOS prompt, re-open your start menu and right click Computer and select Manage
  5. Expand the left-hand side (Services and Applications) and select Internet Information Services
    • You'll now have a new applet within the content window exclusively for IIS.
  6. Expand out your computer and locate the Application Pools node, and select it. (You should now see ASP.NET v4.0 listed)
  7. Expand out your Sites node and locate the site you want to modify (select it)
  8. To the right you'll notice Basic Settings... just below the Edit Site text. Click this, and a new window should appear
  9. Select the .NET 4 AppPool using the Select... button and click ok.
  10. Restart the site, and you should be good-to-go.

(You can repeat steps 7-on for every site you want to apply .NET 4 on as well).

Additional References:

  1. .NET 4 Framework
    The framework for those that don't already have it.
  2. How do I run a command with elevated privileges?
    Directions on how to run the command prompt with Administrator rights.
  3. aspnet_regiis.exe options
    For those that might want to know what -ir or -i does (or the difference between them) or what other options are available. (I typically use -ir to prevent any older sites currently running from breaking on a framework change but that's up to you.)

How to show/hide an element on checkbox checked/unchecked states using jQuery?

$(document).ready(function() {
    $(document).on("click", ".question", function(e) {
       var checked = $(this).find("input:checkbox").is(":checked");
       if (checked) {
       } else {

Java for loop syntax: "for (T obj : objects)"

That's the for each loop syntax. It is looping through each object in the collection returned by objectListing.getObjectSummaries().

Can I use jQuery with Node.js?

Yes you can, using a library I created called nodeQuery

var Express = require('express')
    , dnode = require('dnode')
    , nQuery = require('nodeQuery')
    , express = Express.createServer();

var app = function ($) {
    $.on('ready', function () {
        // do some stuff to the dom in real-time
        $('body').append('Hello World');
        $('body').append('<input type="text" />');
        $('input').live('click', function () {
            console.log('input clicked');
            // ...


    .use(Express.static(__dirname + '/public'))


How to maximize a window using Python

Try using 'Figure.set_size_inches' method, with the extra keyword argument forward=True. According to the documentation, this should resize the figure window.

Whether that actually happens will depend on the operating system you are using.

How to make war file in Eclipse

File -> Export -> Web -> WAR file

OR in Kepler follow as shown below :

enter image description here

ReferenceError: $ is not defined

Your widget has Underscore.js/LoDash.js as dependency.

You can get them here: underscore, lodash

Try prepending this to your code, so you can see if it works:

<script type="text/javascript" src="//"></script>

How to get Maven project version to the bash command line

A simple maven only solution

mvn -q -N org.codehaus.mojo:exec-maven-plugin:1.3.1:exec \
    -Dexec.executable='echo' \

And for bonus points parsed part of a version

mvn -q -N org.codehaus.mojo:build-helper-maven-plugin:3.0.0:parse-version \
    org.codehaus.mojo:exec-maven-plugin:1.3.1:exec \
    -Dexec.executable='echo' \

Improving bulk insert performance in Entity framework

Currently there is no better way, however there may be a marginal improvement by moving SaveChanges inside for loop for probably 10 items.

int i = 0;

foreach (Employees item in sequence)
   t = new Employees ();
   t.Text = item.Text;

   // this will add max 10 items together
   if((i % 10) == 0){
       // show some progress to user based on
       // value of i

You can adjust 10 to be closer to better performance. It will not greatly improve speed but it will allow you to show some progress to user and make it more user friendly.

Python: import module from another directory at the same level in project hierarchy

If I move to the main user_management directory, I can easily use: import Modules.LDAPManager to import --- this works.

Please, don't. In this way the LDAPManager module used by CreateUser will not be the same as the one imported via other imports. This can create problems when you have some global state in the module or during pickling/unpickling. Avoid imports that work only because the module happens to be in the same directory.

When you have a package structure you should either:

  • Use relative imports, i.e if the is in Scripts/:

     from ..Modules import LDAPManager

    Note that this was (note the past tense) discouraged by PEP 8 only because old versions of python didn't support them very well, but this problem was solved years ago. The current version of PEP 8 does suggest them as an acceptable alternative to absolute imports. I actually like them inside packages.

  • Use absolute imports using the whole package name( in Scripts/):

     from user_management.Modules import LDAPManager

In order for the second one to work the package user_management should be installed inside the PYTHONPATH. During development you can configure the IDE so that this happens, without having to manually add calls to sys.path.append anywhere.

Also I find it odd that Scripts/ is a subpackage. Because in a real installation the user_management module would be installed under the site-packages found in the lib/ directory (whichever directory is used to install libraries in your OS), while the scripts should be installed under a bin/ directory (whichever contains executables for your OS).

In fact I believe Script/ shouldn't even be under user_management. It should be at the same level of user_management. In this way you do not have to use -m, but you simply have to make sure the package can be found (this again is a matter of configuring the IDE, installing the package correctly or using PYTHONPATH=. python Scripts/ to launch the scripts with the correct path).

In summary, the hierarchy I would use is:

user_management  (package)
        |------- Modules/
        |           |
        |           |-----
        |           |-----
        |           |-----

 Scripts/  (*not* a package)

Then the code of and should use absolute imports to import the modules:

from user_management.Modules import LDAPManager

During installation you make sure that user_management ends up somewhere in the PYTHONPATH, and the scripts inside the directory for executables so that they are able to find the modules. During development you either rely on IDE configuration, or you launch adding the Scripts/ parent directory to the PYTHONPATH (I mean the directory that contains both user_management and Scripts):

PYTHONPATH=/the/parent/directory python Scripts/

Or you can modify the PYTHONPATH globally so that you don't have to specify this each time. On unix OSes (linux, Mac OS X etc.) you can modify one of the shell scripts to define the PYTHONPATH external variable, on Windows you have to change the environmental variables settings.

Addendum I believe, if you are using python2, it's better to make sure to avoid implicit relative imports by putting:

from __future__ import absolute_import

at the top of your modules. In this way import X always means to import the toplevel module X and will never try to import the file that's in the same directory (if that directory isn't in the PYTHONPATH). In this way the only way to do a relative import is to use the explicit syntax (the from . import X), which is better (explicit is better than implicit).

This will make sure you never happen to use the "bogus" implicit relative imports, since these would raise an ImportError clearly signalling that something is wrong. Otherwise you could use a module that's not what you think it is.