How to use Global Variables in C#?

In C# you cannot define true global variables (in the sense that they don't belong to any class).

This being said, the simplest approach that I know to mimic this feature consists in using a static class, as follows:

public static class Globals
{
    public const Int32 BUFFER_SIZE = 512; // Unmodifiable
    public static String FILE_NAME = "Output.txt"; // Modifiable
    public static readonly String CODE_PREFIX = "US-"; // Unmodifiable
}

You can then retrieve the defined values anywhere in your code (provided it's part of the same namespace):

String code = Globals.CODE_PREFIX + value.ToString();

In order to deal with different namespaces, you can either:

declare the Globals class without including it into a specific namespace (so that it will be placed in the global application namespace);
insert the proper using directive for retrieving the variables from another namespace.

set value of input field by php variable's value

One way to do it will be to move all the php code above the HTML, copy the result to a variable and then add the result in the <input> tag.
Try this -

<?php
//Adding the php to the top.
if(isset($_POST['submit']))
{
    $value1=$_POST['value1'];
    $value2=$_POST['value2'];
    $sign=$_POST['sign'];
    ...
        //Adding to $result variable
    if($sign=='-') {
      $result = $value1-$value2;
    }
    //Rest of your code...
}
?>
<html>
<!--Rest of your tags...-->
Result:<br><input type"text" name="result" value = "<?php echo (isset($result))?$result:'';?>">

accessing a variable from another class

I've tried making an object and tried using .getWidth and .getHeight but can't get it to work.

That´s because you are not setting the width and height fields in JFrame, but you are setting them on local variables. Fields HEIGHT and WIDTH are inhereted from ImageObserver

Fields inherited from interface java.awt.image.ImageObserver
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

See http://java.sun.com/javase/6/docs/api/javax/swing/JFrame.html

If width and height represent state of the frame, then you could refactorize them to fields, and write getters for them.

Then, you could create a Constructor that receives both values as parameters

public class DrawFrame extends JFrame {
 private int width;
 private int height;

 DrawFrame(int _width, int _height){

   this.width = _width;
   this.height = _height;

   //other stuff here
}
 public int getWidth(){}
 public int getHeight(){}

 //other methods
}

If widht and height are going to be constant (after created) then you should use the final modifier. This way, once they are assigned a value, they can´t be modified.

Also, the variables i use in DrawCircle, should I have them in the constructor or not?

The way it is writen now, will only allow you to create one type of circle. If you wan´t to create different circles, you should overload the constructor with one with arguments).

For example, if you want to change the attributes xPoint and yPoint, you could have a constructor

public DrawCircle(int _xpoint, int _ypoint){
  //build circle here.
 }

EDIT:

Where does _width and _height come from?

Those are arguments to constructors. You set values on them when you call the Constructor method.

In DrawFrame I set width and height. In DrawCircle I need to access the width and height of DrawFrame. How do I do this?

DrawFrame(){
   int width = 400;
   int height =400;

   /*
   * call DrawCircle constructor
   */
   content.pane(new DrawCircle(width,height));

   // other stuff

}

Now when the DrawCircle constructor executes, it will receive the values you used in DrawFrame as _width and _height respectively.

EDIT:

Try doing

 DrawFrame frame = new DrawFrame();//constructor contains code on previous edit.
 frame.setPreferredSize(new Dimension(400,400));

http://java.sun.com/docs/books/tutorial/uiswing/components/frame.html

Objective-C Static Class Level variables

u can rename the class as classA.mm and add C++ features in it.

How to add elements to an empty array in PHP?

$cart = array();
$cart[] = 11;
$cart[] = 15;

// etc

//Above is correct. but below one is for further understanding

$cart = array();
for($i = 0; $i <= 5; $i++){
          $cart[] = $i;  

//if you write $cart = [$i]; you will only take last $i value as first element in array.

}
echo "<pre>";
print_r($cart);
echo "</pre>";

How to store standard error in a variable

Redirected stderr to stdout, stdout to /dev/null, and then use the backticks or $() to capture the redirected stderr:

ERROR=$(./useless.sh 2>&1 >/dev/null)

How to initialize a variable of date type in java?

java.util.Date constructor with parameters like ~~new Date(int year, int month, int date, int hrs, int min)~~. is deprecated and preferably do not use it any more. Oracle docs prefers the way over java.util.Calendar. So you can set any date and instantiate Date object through the getTime() method.

Calendar calendar = Calendar.getInstance();
calendar.set(2018, 11, 31, 59, 59, 59);
Date happyNewYearDate = calendar.getTime();

Notice that month number starts from 0

How do I save and restore multiple variables in python?

If you need to save multiple objects, you can simply put them in a single list, or tuple, for instance:

import pickle

# obj0, obj1, obj2 are created here...

# Saving the objects:
with open('objs.pkl', 'w') as f:  # Python 3: open(..., 'wb')
    pickle.dump([obj0, obj1, obj2], f)

# Getting back the objects:
with open('objs.pkl') as f:  # Python 3: open(..., 'rb')
    obj0, obj1, obj2 = pickle.load(f)

If you have a lot of data, you can reduce the file size by passing protocol=-1 to dump(); pickle will then use the best available protocol instead of the default historical (and more backward-compatible) protocol. In this case, the file must be opened in binary mode (wb and rb, respectively).

The binary mode should also be used with Python 3, as its default protocol produces binary (i.e. non-text) data (writing mode 'wb' and reading mode 'rb').

Why does dividing two int not yield the right value when assigned to double?

In C++ language the result of the subexpresison is never affected by the surrounding context (with some rare exceptions). This is one of the principles that the language carefully follows. The expression c = a / b contains of an independent subexpression a / b, which is interpreted independently from anything outside that subexpression. The language does not care that you later will assign the result to a double. a / b is an integer division. Anything else does not matter. You will see this principle followed in many corners of the language specification. That's juts how C++ (and C) works.

One example of an exception I mentioned above is the function pointer assignment/initialization in situations with function overloading

void foo(int);
void foo(double);

void (*p)(double) = &foo; // automatically selects `foo(fouble)`

This is one context where the left-hand side of an assignment/initialization affects the behavior of the right-hand side. (Also, reference-to-array initialization prevents array type decay, which is another example of similar behavior.) In all other cases the right-hand side completely ignores the left-hand side.

ISO C90 forbids mixed declarations and code in C

To diagnose what really triggers the error, I would first try to remove = 0

If the error is tripped, then most likely the declaration goes after the code.
If no error, then it may be related to a C-standard enforcement/compile flags OR ...something else.

In any case, declare the variable in the beginning of the current scope. You may then initialize it separately. Indeed, if this variable deserves its own scope - delimit its definition in {}.

If the OP could clarify the context, then a more directed response would follow.

PHP class: Global variable as property in class

If you want to access a property from inside a class you should:

private $classNumber = 8;

Dynamic variable names in Bash

An extra method that doesn't rely on which shell/bash version you have is by using envsubst. For example:

newvar=$(echo '$magic_variable_'"${dynamic_part}" | envsubst)

How to reference a file for variables using Bash?

The short answer

Use the source command.

An example using `source`

For example:

config.sh

#!/usr/bin/env bash
production="liveschool_joe"
playschool="playschool_joe"
echo $playschool

script.sh

#!/usr/bin/env bash
source config.sh
echo $production

Note that the output from sh ./script.sh in this example is:

~$ sh ./script.sh 
playschool_joe
liveschool_joe

This is because the source command actually runs the program. Everything in config.sh is executed.

Another way

You could use the built-in export command and getting and setting "environment variables" can also accomplish this.

Running export and echo $ENV should be all you need to know about accessing variables. Accessing environment variables is done the same way as a local variable.

To set them, say:

export variable=value

at the command line. All scripts will be able to access this value.

How do JavaScript closures work?

Closures are hard to explain because they are used to make some behaviour work that everybody intuitively expects to work anyway. I find the best way to explain them (and the way that I learned what they do) is to imagine the situation without them:

_x000D_

const makePlus = function(x) {
    return function(y) { return x + y; };
}

const plus5 = makePlus(5);
console.log(plus5(3));

_x000D_

What would happen here if JavaScript didn't know closures? Just replace the call in the last line by its method body (which is basically what function calls do) and you get:

console.log(x + 3);

Now, where's the definition of x? We didn't define it in the current scope. The only solution is to let plus5 carry its scope (or rather, its parent's scope) around. This way, x is well-defined and it is bound to the value 5.

Environment variables in Eclipse

The .bashrc file is used for setting variables used by interactive login shells. If you want those environment variables available in Eclipse you need to put them in /etc/environment.

Python Function to test ping

This is my version of check ping function. May be if well be usefull for someone:

def check_ping(host):
if platform.system().lower() == "windows":
response = os.system("ping -n 1 -w 500 " + host + " > nul")
if response == 0:
return "alive"
else:
return "not alive"
else:
response = os.system("ping -c 1 -W 0.5" + host + "> /dev/null")
if response == 1:
return "alive"
else:
return "not alive"

More elegant way of declaring multiple variables at the same time

What's the problem , in fact ?

If you really need or want 10 a, b, c, d, e, f, g, h, i, j , there will be no other possibility, at a time or another, to write a and write b and write c.....

If the values are all different, you will be obliged to write for exemple

a = 12
b= 'sun'
c = A() #(where A is a class)
d = range(1,102,5)
e = (line in filehandler if line.rstrip())
f = 0,12358
g = True
h = random.choice
i = re.compile('^(!=  ab).+?<span>')
j = [78,89,90,0]

that is to say defining the "variables" individually.

Or , using another writing, no need to use _ :

a,b,c,d,e,f,g,h,i,j =\
12,'sun',A(),range(1,102,5),\
(line for line in filehandler if line.rstrip()),\
0.12358,True,random.choice,\
re.compile('^(!=  ab).+?<span>'),[78,89,90,0]

a,b,c,d,e,f,g,h,i,j =\
(12,'sun',A(),range(1,102,5),
 (line for line in filehandler if line.rstrip()),
 0.12358,True,random.choice,
 re.compile('^(!=  ab).+?<span>'),[78,89,90,0])

If some of them must have the same value, is the problem that it's too long to write

a, b, c, d, e, f, g, h, i, j = True, True, True, True, True, False, True ,True , True, True

Then you can write:

a=b=c=d=e=g=h=i=k=j=True
f = False

I don't understand what is exactly your problem. If you want to write a code, you're obliged to use the characters required by the writing of the instructions and definitions. What else ?

I wonder if your question isn't the sign that you misunderstand something.

When one writes a = 10 , one don't create a variable in the sense of "chunk of memory whose value can change". This instruction:

either triggers the creation of an object of type integer and value 10 and the binding of a name 'a' with this object in the current namespace
or re-assign the name 'a' in the namespace to the object 10 (because 'a' was precedently binded to another object)

I say that because I don't see the utility to define 10 identifiers a,b,c... pointing to False or True. If these values don't change during the execution, why 10 identifiers ? And if they change, why defining the identifiers first ?, they will be created when needed if not priorly defined

Your question appears weird to me

How to obtain values of request variables using Python and Flask

Adding more to Jason's more generalized way of retrieving the POST data or GET data

from flask_restful import reqparse

def parse_arg_from_requests(arg, **kwargs):
    parse = reqparse.RequestParser()
    parse.add_argument(arg, **kwargs)
    args = parse.parse_args()
    return args[arg]

form_field_value = parse_arg_from_requests('FormFieldValue')

Passing Variable through JavaScript from one html page to another page

Your best option here, is to use the Query String to 'send' the value.

how to get query string value using javascript

So page 1 redirects to page2.html?someValue=ABC
Page 2 can then read the query string and specifically the key 'someValue'

If this is anything more than a learning exercise you may want to consider the security implications of this though.

Global variables wont help you here as once the page is re-loaded they are destroyed.

Passing a variable from one php include file to another: global vs. not

This is all you have to do:

In front.inc

global $name;
$name = 'james';

How to pass a list from Python, by Jinja2 to JavaScript

To pass some context data to javascript code, you have to serialize it in a way it will be "understood" by javascript (namely JSON). You also need to mark it as safe using the safe Jinja filter, to prevent your data from being htmlescaped.

You can achieve this by doing something like that:

The view

import json

@app.route('/')
def my_view():
    data = [1, 'foo']
    return render_template('index.html', data=json.dumps(data))

The template

<script type="text/javascript">
    function test_func(data) {
        console.log(data);
    }
    test_func({{ data|safe }})
</script>

Edit - exact answer

So, to achieve exactly what you want (loop over a list of items, and pass them to a javascript function), you'd need to serialize every item in your list separately. Your code would then look like this:

The view

import json

@app.route('/')
def my_view():
    data = [1, "foo"]
    return render_template('index.html', data=map(json.dumps, data))

The template

{% for item in data %}
    <span onclick=someFunction({{ item|safe }});>{{ item }}</span>
{% endfor %}

Edit 2

In my example, I use Flask, I don't know what framework you're using, but you got the idea, you just have to make it fit the framework you use.

Edit 3 (Security warning)

NEVER EVER DO THIS WITH USER-SUPPLIED DATA, ONLY DO THIS WITH TRUSTED DATA!

Otherwise, you would expose your application to XSS vulnerabilities!

When should an Excel VBA variable be killed or set to Nothing?

VB6/VBA uses deterministic approach to destoying objects. Each object stores number of references to itself. When the number reaches zero, the object is destroyed.

Object variables are guaranteed to be cleaned (set to Nothing) when they go out of scope, this decrements the reference counters in their respective objects. No manual action required.

There are only two cases when you want an explicit cleanup:

When you want an object to be destroyed before its variable goes out of scope (e.g., your procedure is going to take long time to execute, and the object holds a resource, so you want to destroy the object as soon as possible to release the resource).
When you have a circular reference between two or more objects.

If objectA stores a references to objectB, and objectB stores a reference to objectA, the two objects will never get destroyed unless you brake the chain by explicitly setting objectA.ReferenceToB = Nothing or objectB.ReferenceToA = Nothing.

The code snippet you show is wrong. No manual cleanup is required. It is even harmful to do a manual cleanup, as it gives you a false sense of more correct code.

If you have a variable at a class level, it will be cleaned/destroyed when the class instance is destructed. You can destroy it earlier if you want (see item 1.).

If you have a variable at a module level, it will be cleaned/destroyed when your program exits (or, in case of VBA, when the VBA project is reset). You can destroy it earlier if you want (see item 1.).

Access level of a variable (public vs. private) does not affect its life time.

Is it possible to print a variable's type in standard C++?

You can use templates.

template <typename T> const char* typeof(T&) { return "unknown"; }    // default
template<> const char* typeof(int&) { return "int"; }
template<> const char* typeof(float&) { return "float"; }

In the example above, when the type is not matched it will print "unknown".

What is the purpose of the single underscore "_" variable in Python?

_ has 3 main conventional uses in Python:

To hold the result of the last executed expression(/statement) in an interactive interpreter session (see docs). This precedent was set by the standard CPython interpreter, and other interpreters have followed suit
For translation lookup in i18n (see the gettext documentation for example), as in code like
```
raise forms.ValidationError(_("Please enter a correct username"))
```
As a general purpose "throwaway" variable name:
1. To indicate that part of a function result is being deliberately ignored (Conceptually, it is being discarded.), as in code like:
```
label, has_label, _ = text.partition(':')
```
2. As part of a function definition (using either def or lambda), where the signature is fixed (e.g. by a callback or parent class API), but this particular function implementation doesn't need all of the parameters, as in code like:
```
def callback(_):
    return True
```
  [For a long time this answer didn't list this use case, but it came up often enough, as noted here, to be worth listing explicitly.]
This use case can conflict with the translation lookup use case, so it is necessary to avoid using _ as a throwaway variable in any code block that also uses it for i18n translation (many folks prefer a double-underscore, __, as their throwaway variable for exactly this reason).

Linters often recognize this use case. For example year, month, day = date() will raise a lint warning if day is not used later in the code. The fix, if day is truly not needed, is to write year, month, _ = date(). Same with lambda functions, lambda arg: 1.0 creates a function requiring one argument but not using it, which will be caught by lint. The fix is to write lambda _: 1.0. An unused variable is often hiding a bug/typo (e.g. set day but use dya in the next line).

How to delete an instantiated object Python?

object.__del__(self) is called when the instance is about to be destroyed.

>>> class Test:
...     def __del__(self):
...         print "deleted"
... 
>>> test = Test()
>>> del test
deleted

Object is not deleted unless all of its references are removed(As quoted by ethan)

Also, From Python official doc reference:

del x doesn’t directly call x.del() — the former decrements the reference count for x by one, and the latter is only called when x‘s reference count reaches zero

Getting the name of a variable as a string

You can try the following to retrieve the name of a function you defined (does not work for built-in functions though):

import re
def retrieve_name(func):
    return re.match("<function\s+(\w+)\s+at.*", str(func)).group(1)

def foo(x):
    return x**2

print(retrieve_name(foo))
# foo

Determine if variable is defined in Python

I think it's better to avoid the situation. It's cleaner and clearer to write:

a = None
if condition:
    a = 42

What is a None value?

All of these are good answers but I think there's more to explain why None is useful.

Imagine you collecting RSVPs to a wedding. You want to record whether each person will attend. If they are attending, you set person.attending = True. If they are not attending you set person.attending = False. If you have not received any RSVP, then person.attending = None. That way you can distinguish between no information - None - and a negative answer.

What does ${} (dollar sign and curly braces) mean in a string in Javascript?

You can also perform Implicit Type Conversions with template literals. Example:

let fruits = ["mango","orange","pineapple","papaya"];

console.log(`My favourite fruits are ${fruits}`);
// My favourite fruits are mango,orange,pineapple,papaya

Will using 'var' affect performance?

The C# compiler infers the true type of the var variable at compile time. There's no difference in the generated IL.

Create timestamp variable in bash script

Lots of answer but couldn't find what I was looking for :

date +"%s.%3N"

returns something like : 1606297368.210

VBA Check if variable is empty

For a number, it is tricky because if a numeric cell is empty VBA will assign a default value of 0 to it, so it is hard for your VBA code to tell the difference between an entered zero and a blank numeric cell.

The following check worked for me to see if there was an actual 0 entered into the cell:

If CStr(rng.value) = "0" then
    'your code here'
End If

Define a global variable in a JavaScript function

As the others have said, you can use var at global scope (outside of all functions and modules) to declare a global variable:

<script>
var yourGlobalVariable;
function foo() {
    // ...
}
</script>

(Note that that's only true at global scope. If that code were in a module — <script type="module">...</script> — it wouldn't be at global scope, so that wouldn't create a global.)

Alternatively:

In modern environments, you can assign to a property on the object that globalThis refers to (globalThis was added in ES2020):

<script>
function foo() {
    globalThis.yourGlobalVariable = ...;
}
</script>

On browsers, you can do the same thing with the global called window:

<script>
function foo() {
    window.yourGlobalVariable = ...;
}
</script>

...because in browsers, ~~all global variables~~ global variables declared with var are properties of the window object. (In the latest specification, ECMAScript 2015, the new let, const, and class statements at global scope create globals that aren't properties of the global object; a new concept in ES2015.)

(There's also the horror of implicit globals, but don't do it on purpose and do your best to avoid doing it by accident, perhaps by using ES5's "use strict".)

All that said: I'd avoid global variables if you possibly can (and you almost certainly can). As I mentioned, they end up being properties of window, and window is already plenty crowded enough what with all elements with an id (and many with just a name) being dumped in it (and regardless that upcoming specification, IE dumps just about anything with a name on there).

Instead, in modern environments, use modules:

<script type="module">
let yourVariable = 42;
// ...
</script>

The top level code in a module is at module scope, not global scope, so that creates a variable that all of the code in that module can see, but that isn't global.

In obsolete environments without module support, wrap your code in a scoping function and use variables local to that scoping function, and make your other functions closures within it:

<script>
(function() { // Begin scoping function
    var yourGlobalVariable; // Global to your code, invisible outside the scoping function
    function foo() {
        // ...
    }
})();         // End scoping function
</script>

Use YAML with variables

I had this same question, and after a lot of research, it looks like it's not possible.

The answer from cgat is on the right track, but you can't actually concatenate references like that.

Here are things you can do with "variables" in YAML (which are officially called "node anchors" when you set them and "references" when you use them later):

Define a value and use an exact copy of it later:

default: &default_title This Post Has No Title
title: *default_title

{ or }

example_post: &example
  title: My mom likes roosters
  body: Seriously, she does. And I don't know when it started.
  date: 8/18/2012
first_post: *example
second_post:
  title: whatever, etc.

For more info, see this section of the wiki page about YAML: http://en.wikipedia.org/wiki/YAML#References

Define an object and use it with modifications later:

default: &DEFAULT
  URL:          stooges.com
  throw_pies?:  true  
  stooges:  &stooge_list
    larry:  first_stooge
    moe:    second_stooge
    curly:  third_stooge

development:
  <<: *DEFAULT
  URL:      stooges.local
  stooges: 
    shemp: fourth_stooge

test:
  <<: *DEFAULT
  URL:    test.stooges.qa
  stooges: 
    <<: *stooge_list
    shemp: fourth_stooge

This is taken directly from a great demo here: https://gist.github.com/bowsersenior/979804

Splitting a continuous variable into equal sized groups

Without any extra package, 3 being the number of groups:

> findInterval(das$wt, unique(quantile(das$wt, seq(0, 1, length.out = 3 + 1))), rightmost.closed = TRUE)
 [1] 1 1 1 2 2 2 3 1 3 3 3 2 1 3 2

You can speed up the quantile computation by using a representative sample of the values of interest. Double check the documentation of the FindInterval function.

Mixing a PHP variable with a string literal

echo "{$test}y";

You can use braces to remove ambiguity when interpolating variables directly in strings.

Also, this doesn't work with single quotes. So:

echo '{$test}y';

will output

{$test}y

JUnit Testing private variables?

Despite the danger of stating the obvious: With a unit test you want to test the correct behaviour of the object - and this is defined in terms of its public interface. You are not interested in how the object accomplishes this task - this is an implementation detail and not visible to the outside. This is one of the things why OO was invented: That implementation details are hidden. So there is no point in testing private members. You said you need 100% coverage. If there is a piece of code that cannot be tested by using the public interface of the object, then this piece of code is actually never called and hence not testable. Remove it.

How do I use variables in Oracle SQL Developer?

Try this it will work, it's better create a procedure, if procedure is not possible you can use this script.

with param AS(
SELECT 1234 empid
FROM dual)
 SELECT *
  FROM Employees, param
  WHERE EmployeeID = param.empid;
END;

shared global variables in C

In the header file write it with extern. And at the global scope of one of the c files declare it without extern.

How to swap two variables in JavaScript

You can use ES6 destructuring assignment like so:

let a = 10;
let b = 20;

[a, b] = [b, a]; 

console.log(a, b); // a = 20, b = 10

Convert dictionary to bytes and back again python?

This should work:

s=json.dumps(variables)
variables2=json.loads(s)
assert(variables==variables2)

Convert Variable Name to String?

I searched for this question because I wanted a Python program to print assignment statements for some of the variables in the program. For example, it might print "foo = 3, bar = 21, baz = 432". The print function would need the variable names in string form. I could have provided my code with the strings "foo","bar", and "baz", but that felt like repeating myself. After reading the previous answers, I developed the solution below.

The globals() function behaves like a dict with variable names (in the form of strings) as keys. I wanted to retrieve from globals() the key corresponding to the value of each variable. The method globals().items() returns a list of tuples; in each tuple the first item is the variable name (as a string) and the second is the variable value. My variablename() function searches through that list to find the variable name(s) that corresponds to the value of the variable whose name I need in string form.

The function itertools.ifilter() does the search by testing each tuple in the globals().items() list with the function lambda x: var is globals()[x[0]]. In that function x is the tuple being tested; x[0] is the variable name (as a string) and x[1] is the value. The lambda function tests whether the value of the tested variable is the same as the value of the variable passed to variablename(). In fact, by using the is operator, the lambda function tests whether the name of the tested variable is bound to the exact same object as the variable passed to variablename(). If so, the tuple passes the test and is returned by ifilter().

The itertools.ifilter() function actually returns an iterator which doesn't return any results until it is called properly. To get it called properly, I put it inside a list comprehension [tpl[0] for tpl ... globals().items())]. The list comprehension saves only the variable name tpl[0], ignoring the variable value. The list that is created contains one or more names (as strings) that are bound to the value of the variable passed to variablename().

In the uses of variablename() shown below, the desired string is returned as an element in a list. In many cases, it will be the only item in the list. If another variable name is assigned the same value, however, the list will be longer.

>>> def variablename(var):
...     import itertools
...     return [tpl[0] for tpl in 
...     itertools.ifilter(lambda x: var is x[1], globals().items())]
... 
>>> var = {}
>>> variablename(var)
['var']
>>> something_else = 3
>>> variablename(something_else)
['something_else']
>>> yet_another = 3
>>> variablename(something_else)
['yet_another', 'something_else']

Java system properties and environment variables

System properties are set on the Java command line using the -Dpropertyname=value syntax. They can also be added at runtime using System.setProperty(String key, String value) or via the various System.getProperties().load() methods.
To get a specific system property you can use System.getProperty(String key) or System.getProperty(String key, String def).
Environment variables are set in the OS, e.g. in Linux export HOME=/Users/myusername or on Windows SET WINDIR=C:\Windows etc, and, unlike properties, may not be set at runtime.
To get a specific environment variable you can use System.getenv(String name).

How to check if a variable is set in Bash?

There are many ways to do this with the following being one of them:

if [ -z "$1" ]

This succeeds if $1 is null or unset

Expansion of variables inside single quotes in a command in Bash

just use printf

instead of

repo forall -c '....$variable'

use printf to replace the variable token with the expanded variable.

For example:

template='.... %s'

repo forall -c $(printf "${template}" "${variable}")

Viewing all defined variables

globals(), locals(), vars(), and dir() may all help you in what you want.

Check if object exists in JavaScript

Think it's easiest like this

if(myobject_or_myvar)
    alert('it exists');
else
   alert("what the hell you'll talking about");

Save current directory in variable using Bash?

Your assignment has an extra $:

export PATH=$PATH:${PWD}:/foo/bar

While variable is not defined - wait

Shorter way:

   var queue = function (args){
      typeof variableToCheck !== "undefined"? doSomething(args) : setTimeout(function () {queue(args)}, 2000);
};

You can also pass arguments

How can I simulate an array variable in MySQL?

Is an array variable really necessary?

I ask because I originally landed here wanting to add an array as a MySQL table variable. I was relatively new to database design and trying to think of how I'd do it in a typical programming language fashion.

But databases are different. I thought I wanted an array as a variable, but it turns out that's just not a common MySQL database practice.

Standard Practice

The alternative solution to arrays is to add an additional table, and then reference your original table with a foreign key.

As an example, let's imagine an application that keeps track of all the items every person in a household wants to buy at the store.

The commands for creating the table I originally envisioned would have looked something like this:

#doesn't work
CREATE TABLE Person(
  name VARCHAR(50) PRIMARY KEY
  buy_list ARRAY
);

I think I envisioned buy_list to be a comma-separated string of items or something like that.

But MySQL doesn't have an array type field, so I really needed something like this:

CREATE TABLE Person(
  name VARCHAR(50) PRIMARY KEY
);
CREATE TABLE BuyList(
  person VARCHAR(50),
  item VARCHAR(50),
  PRIMARY KEY (person, item),
  CONSTRAINT fk_person FOREIGN KEY (person) REFERENCES Person(name)
);

Here we define a constraint named fk_person. It says that the 'person' field in BuyList is a foreign key. In other words, it's a primary key in another table, specifically the 'name' field in the Person table, which is what REFERENCES denotes.

We also defined the combination of person and item to be the primary key, but technically that's not necessary.

Finally, if you want to get all the items on a person's list, you can run this query:

SELECT item FROM BuyList WHERE person='John';

This gives you all the items on John's list. No arrays necessary!

printf a variable in C

Your printf needs a format string:

printf("%d\n", x);

This reference page gives details on how to use printf and related functions.

How do you use script variables in psql?

FWIW, the real problem was that I had included a semicolon at the end of my \set command:

\set owner_password 'thepassword';

The semicolon was interpreted as an actual character in the variable:

\echo :owner_password thepassword;

So when I tried to use it:

CREATE ROLE myrole LOGIN UNENCRYPTED PASSWORD :owner_password NOINHERIT CREATEDB CREATEROLE VALID UNTIL 'infinity';

...I got this:

CREATE ROLE myrole LOGIN UNENCRYPTED PASSWORD thepassword; NOINHERIT CREATEDB CREATEROLE VALID UNTIL 'infinity';

That not only failed to set the quotes around the literal, but split the command into 2 parts (the second of which was invalid as it started with "NOINHERIT").

The moral of this story: PostgreSQL "variables" are really macros used in text expansion, not true values. I'm sure that comes in handy, but it's tricky at first.

MySQL: @variable vs. variable. What's the difference?

MSSQL requires that variables within procedures be DECLAREd and folks use the @Variable syntax (DECLARE @TEXT VARCHAR(25) = 'text'). Also, MS allows for declares within any block in the procedure, unlike mySQL which requires all the DECLAREs at the top.

While good on the command line, I feel using the "set = @variable" within stored procedures in mySQL is risky. There is no scope and variables live across scope boundaries. This is similar to variables in JavaScript being declared without the "var" prefix, which are then the global namespace and create unexpected collisions and overwrites.

I am hoping that the good folks at mySQL will allow DECLARE @Variable at various block levels within a stored procedure. Notice the @ (at sign). The @ sign prefix helps to separate variable names from table column names - as they are often the same. Of course, one can always add an "v" or "l_" prefix, but the @ sign is a handy and succinct way to have the variable name match the column you might be extracting the data from without clobbering it.

MySQL is new to stored procedures and they have done a good job for their first version. It will be a pleaure to see where they take it form here and to watch the server side aspects of the language mature.

How to return the output of stored procedure into a variable in sql server

You can use the return statement inside a stored procedure to return an integer status code (and only of integer type). By convention a return value of zero is used for success.

If no return is explicitly set, then the stored procedure returns zero.

   CREATE PROCEDURE GetImmediateManager
      @employeeID INT,
      @managerID INT OUTPUT
   AS
   BEGIN
     SELECT @managerID = ManagerID 
     FROM HumanResources.Employee 
     WHERE EmployeeID = @employeeID

     if @@rowcount = 0 -- manager not found?
       return 1;
   END

And you call it this way:

DECLARE @return_status int;
DECLARE @managerID int;

EXEC @return_status = GetImmediateManager 2, @managerID output;
if @return_status = 1
  print N'Immediate manager not found!';
else 
  print N'ManagerID is ' + @managerID;
go

You should use the return value for status codes only. To return data, you should use output parameters.

If you want to return a dataset, then use an output parameter of type cursor.

How can I print variable and string on same line in Python?

Python is a very versatile language. You may print variables by different methods. I have listed below five methods. You may use them according to your convenience.

Example:

a = 1
b = 'ball'

Method 1:

print('I have %d %s' % (a, b))

Method 2:

print('I have', a, b)

Method 3:

print('I have {} {}'.format(a, b))

Method 4:

print('I have ' + str(a) + ' ' + b)

Method 5:

print(f'I have {a} {b}')

The output would be:

I have 1 ball

PHP Multiple Checkbox Array

if (isset($_POST['submit'])) {

for($i = 0; $i<= 3; $i++){

    if(isset($_POST['books'][$i]))

        $book .= ' '.$_POST['books'][$i];
}

Using variables inside a bash heredoc

Don't use quotes with <<EOF:

var=$1
sudo tee "/path/to/outfile" > /dev/null <<EOF
Some text that contains my $var
EOF

Variable expansion is the default behavior inside of here-docs. You disable that behavior by quoting the label (with single or double quotes).

Remove an element from a Bash array

Actually, I just noticed that the shell syntax somewhat has a behavior built-in that allows for easy reconstruction of the array when, as posed in the question, an item should be removed.

# let's set up an array of items to consume:
x=()
for (( i=0; i<10; i++ )); do
    x+=("$i")
done

# here, we consume that array:
while (( ${#x[@]} )); do
    i=$(( $RANDOM % ${#x[@]} ))
    echo "${x[i]} / ${x[@]}"
    x=("${x[@]:0:i}" "${x[@]:i+1}")
done

Notice how we constructed the array using bash's x+=() syntax?

You could actually add more than one item with that, the content of a whole other array at once.

What is the meaning of @_ in Perl?

Also if a function returns an array, but the function is called without assigning its returned data to any variable like below. Here split() is called, but it is not assigned to any variable. We can access its returned data later through @_:

$str = "Mr.Bond|Chewbaaka|Spider-Man";
split(/\|/, $str);

print @_[0]; # 'Mr.Bond'

This will split the string $str and set the array @_.

Multiple left-hand assignment with JavaScript

coffee-script can accomplish this with aplomb..

for x in [ 'a', 'b', 'c' ] then "#{x}" : true

[ { a: true }, { b: true }, { c: true } ]

How do I get the type of a variable?

You can use the typeid operator:

#include <typeinfo>
...
cout << typeid(variable).name() << endl;

How can I determine if a variable is 'undefined' or 'null'?

I've just had this problem i.e. checking if an object is null.
I simply use this:

if (object) {
    // Your code
}

For example:

if (document.getElementById("enterJob")) {
    document.getElementById("enterJob").className += ' current';
}

How to trim whitespace from a Bash variable?

I would simply use sed:

function trim
{
    echo "$1" | sed -n '1h;1!H;${;g;s/^[ \t]*//g;s/[ \t]*$//g;p;}'
}

a) Example of usage on single-line string

string='    wordA wordB  wordC   wordD    '
trimmed=$( trim "$string" )

echo "GIVEN STRING: |$string|"
echo "TRIMMED STRING: |$trimmed|"

Output:

GIVEN STRING: |    wordA wordB  wordC   wordD    |
TRIMMED STRING: |wordA wordB  wordC   wordD|

b) Example of usage on multi-line string

string='    wordA
   >wordB<
wordC    '
trimmed=$( trim "$string" )

echo -e "GIVEN STRING: |$string|\n"
echo "TRIMMED STRING: |$trimmed|"

Output:

GIVEN STRING: |    wordAA
   >wordB<
wordC    |

TRIMMED STRING: |wordAA
   >wordB<
wordC|

c) Final note:
If you don't like to use a function, for single-line string you can simply use a "easier to remember" command like:

echo "$string" | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//'

Example:

echo "   wordA wordB wordC   " | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//'

Output:

wordA wordB wordC

Using the above on multi-line strings will work as well, but please note that it will cut any trailing/leading internal multiple space as well, as GuruM noticed in the comments

string='    wordAA
    >four spaces before<
 >one space before<    '
echo "$string" | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//'

Output:

wordAA
>four spaces before<
>one space before<

So if you do mind to keep those spaces, please use the function at the beginning of my answer!

d) EXPLANATION of the sed syntax "find and replace" on multi-line strings used inside the function trim:

sed -n '
# If the first line, copy the pattern to the hold buffer
1h
# If not the first line, then append the pattern to the hold buffer
1!H
# If the last line then ...
$ {
    # Copy from the hold to the pattern buffer
    g
    # Do the search and replace
    s/^[ \t]*//g
    s/[ \t]*$//g
    # print
    p
}'

Best way to retrieve variable values from a text file?

If your data has a regular structure you can read a file in line by line and populate your favorite container. For example:

Let's say your data has 3 variables: x, y, i.

A file contains n of these data, each variable on its own line (3 lines per record). Here are two records:

Here's how you read your file data into a list. (Reading from text, so cast accordingly.)

data = []
try:
    with open(dataFilename, "r") as file:
        # read data until end of file
        x = file.readline()
        while x != "":
            x = int(x.strip())    # remove \n, cast as int

            y = file.readline()
            y = int(y.strip())

            i = file.readline()
            i = int(i.strip())

            data.append([x,y,i])

            x = file.readline()

except FileNotFoundError as e:
    print("File not found:", e)

return(data)

how to define variable in jquery

in jquery we have to use selector($) to declare variables

var test=$("<%=ddl.ClientId%>");

here we can get the id of drop down to j query variable

Formatting a float to 2 decimal places

You can pass the format in to the ToString method, e.g.:

myFloatVariable.ToString("0.00"); //2dp Number

myFloatVariable.ToString("n2"); // 2dp Number

myFloatVariable.ToString("c2"); // 2dp currency

Standard Number Format Strings

How to access global variables

I suggest use the common way of import.

First I will explain the way it called "relative import" maybe this way cause of some error

Second I will explain the common way of import.

FIRST:

In go version >= 1.12 there is some new tips about import file and somethings changed.

1- You should put your file in another folder for example I create a file in "model" folder and the file's name is "example.go"

2- You have to use uppercase when you want to import a file!

3- Use Uppercase for variables, structures and functions that you want to import in another files

Notice: There is no way to import the main.go in another file.

file directory is:

root
|_____main.go
|_____model
          |_____example.go

this is a example.go:

package model

import (
    "time"
)

var StartTime = time.Now()

and this is main.go you should use uppercase when you want to import a file. "Mod" started with uppercase

package main

import (
    Mod "./model"
    "fmt"
)

func main() {
    fmt.Println(Mod.StartTime)
}

NOTE!!!

NOTE: I don't recommend this this type of import!

SECOND:

(normal import)

the better way import file is:

your structure should be like this:

root
|_____github.com
         |_________Your-account-name-in-github
         |                |__________Your-project-name
         |                                |________main.go
         |                                |________handlers
         |                                |________models
         |               
         |_________gorilla
                         |__________sessions

and this is a example:

package main

import (
    "github.com/gorilla/sessions"
)

func main(){
     //you can use sessions here
}

so you can import "github.com/gorilla/sessions" in every where that you want...just import it.

What is the correct way to declare a boolean variable in Java?

You don't have to, but some people like to explicitly initialize all variables (I do too). Especially those who program in a variety of languages, it's just easier to have the rule of always initializing your variables rather than deciding case-by-case/language-by-language.

For instance Java has default values for Boolean, int etc .. C on the other hand doesn't automatically give initial values, whatever happens to be in memory is what you end up with unless you assign a value explicitly yourself.

In your case above, as you discovered, the code works just as well without the initialization, esp since the variable is set in the next line which makes it appear particularly redundant. Sometimes you can combine both of those lines (declaration and initialization - as shown in some of the other posts) and get the best of both approaches, i.e., initialize the your variable with the result of the email1.equals (email2); operation.

How to store a command in a variable in a shell script?

var=$(echo "asdf")
echo $var
# => asdf

Using this method, the command is immediately evaluated and it's return value is stored.

stored_date=$(date)
echo $stored_date
# => Thu Jan 15 10:57:16 EST 2015
# (wait a few seconds)
echo $stored_date
# => Thu Jan 15 10:57:16 EST 2015

Same with backtick

stored_date=`date`
echo $stored_date
# => Thu Jan 15 11:02:19 EST 2015
# (wait a few seconds)
echo $stored_date
# => Thu Jan 15 11:02:19 EST 2015

Using eval in the $(...) will not make it evaluated later

stored_date=$(eval "date")
echo $stored_date
# => Thu Jan 15 11:05:30 EST 2015
# (wait a few seconds)
echo $stored_date
# => Thu Jan 15 11:05:30 EST 2015

Using eval, it is evaluated when eval is used

stored_date="date" # < storing the command itself
echo $(eval "$stored_date")
# => Thu Jan 15 11:07:05 EST 2015
# (wait a few seconds)
echo $(eval "$stored_date")
# => Thu Jan 15 11:07:16 EST 2015
#                     ^^ Time changed

In the above example, if you need to run a command with arguments, put them in the string you are storing

stored_date="date -u"
# ...

For bash scripts this is rarely relevant, but one last note. Be careful with eval. Eval only strings you control, never strings coming from an untrusted user or built from untrusted user input.

Thanks to @CharlesDuffy for reminding me to quote the command!

How can I define colors as variables in CSS?

If you have Ruby on your system you can do this:

http://unixgods.org/~tilo/Ruby/Using_Variables_in_CSS_Files_with_Ruby_on_Rails.html

This was made for Rails, but see below for how to modify it to run it stand alone.

You could use this method independently from Rails, by writing a small Ruby wrapper script which works in conjunction with site_settings.rb and takes your CSS-paths into account, and which you can call every time you want to re-generate your CSS (e.g. during site startup)

You can run Ruby on pretty much any operating system, so this should be fairly platform independent.

e.g. wrapper: generate_CSS.rb (run this script whenever you need to generate your CSS)

#/usr/bin/ruby  # preferably Ruby 1.9.2 or higher
require './site_settings.rb' # assuming your site_settings file is on the same level 

CSS_IN_PATH  = File.join( PATH-TO-YOUR-PROJECT, 'css-input-files')
CSS_OUT_PATH = File.join( PATH-TO-YOUR-PROJECT, 'static' , 'stylesheets' ) 

Site.generate_CSS_files( CSS_IN_PATH , CSS_OUT_PATH )

the generate_CSS_files method in site_settings.rb then needs to be modified like this:

module Site
#   ... see above link for complete contents

  # Module Method which generates an OUTPUT CSS file *.css for each INPUT CSS file *.css.in we find in our CSS directory
  # replacing any mention of Color Constants , e.g. #SomeColor# , with the corresponding color code defined in Site::Color
  #
  # We will only generate CSS files if they are deleted or the input file is newer / modified
  #
  def self.generate_CSS_files(input_path = File.join( Rails.root.to_s , 'public' ,'stylesheets') , 
                              output_path = File.join( Rails.root.to_s , 'public' ,'stylesheets'))
    # assuming all your CSS files live under "./public/stylesheets"
    Dir.glob( File.join( input_path, '*.css.in') ).each do |filename_in|
      filename_out = File.join( output_path , File.basename( filename_in.sub(/.in$/, '') ))

      # if the output CSS file doesn't exist, or the the input CSS file is newer than the output CSS file:
      if (! File.exists?(filename_out)) || (File.stat( filename_in ).mtime > File.stat( filename_out ).mtime)
        # in this case, we'll need to create the output CSS file fresh:
        puts " processing #{filename_in}\n --> generating #{filename_out}"

        out_file = File.open( filename_out, 'w' )
        File.open( filename_in , 'r' ).each do |line|
          if line =~ /^\s*\/\*/ || line =~ /^\s+$/             # ignore empty lines, and lines starting with a comment
            out_file.print(line)
            next
          end
          while  line =~ /#(\w+)#/  do                         # substitute all the constants in each line
            line.sub!( /#\w+#/ , Site::Color.const_get( $1 ) ) # with the color the constant defines
          end
          out_file.print(line)
        end
        out_file.close
      end # if ..
    end
  end # def self.generate_CSS_files

end # module Site

VBA: Selecting range by variables

I tried using:

Range(cells(1, 1), cells(lastRow, lastColumn)).Select

where lastRow and lastColumn are integers, but received run-time error 1004. I'm using an older VB (6.5).

What did work was to use the following:

Range(Chr(64 + firstColumn) & firstRow & ":" & Chr(64 + lastColumn) & firstColumn).Select.

Removing double quotes from variables in batch file creates problems with CMD environment

@echo off

Setlocal enabledelayedexpansion

Set 1=%1

Set 1=!1:"=!

Echo !1!

Echo "!1!"

Set 1=

Demonstrates with or without quotes reguardless of whether original parameter has quotes or not.

And if you want to test the existence of a parameter which may or may not be in quotes, put this line before the echos above:

If '%1'=='' goto yoursub

But if checking for existence of a file that may or may not have quotes then it's:

If EXIST "!1!" goto othersub

Note the use of single quotes and double quotes are different.

How can you print a variable name in python?

With eager evaluation, variables essentially turn into their values any time you look at them (to paraphrase). That said, Python does have built-in namespaces. For example, locals() will return a dictionary mapping a function's variables' names to their values, and globals() does the same for a module. Thus:

for name, value in globals().items():
    if value is unknown_variable:
        ... do something with name

Note that you don't need to import anything to be able to access locals() and globals().

Also, if there are multiple aliases for a value, iterating through a namespace only finds the first one.

python: how to identify if a variable is an array or a scalar

To answer the question in the title, a direct way to tell if a variable is a scalar is to try to convert it to a float. If you get TypeError, it's not.

N = [1, 2, 3]
try:
    float(N)
except TypeError:
    print('it is not a scalar')
else:
    print('it is a scalar')

How do I create a multiline Python string with inline variables?

A dictionary can be passed to format(), each key name will become a variable for each associated value.

dict = {'string1': 'go',
        'string2': 'now',
        'string3': 'great'}

multiline_string = '''I'm will {string1} there
I will go {string2}
{string3}'''.format(**dict)

print(multiline_string)

Also a list can be passed to format(), the index number of each value will be used as variables in this case.

list = ['go',
        'now',
        'great']

multiline_string = '''I'm will {0} there
I will go {1}
{2}'''.format(*list)

print(multiline_string)

Both solutions above will output the same:

I'm will go there
I will go now
great

Static variables in JavaScript

you can use arguments.callee to store "static" variables (this is useful in anonymous function too):

function () {
  arguments.callee.myStaticVar = arguments.callee.myStaticVar || 1;
  arguments.callee.myStaticVar++;
  alert(arguments.callee.myStaticVar);
}

Passing javascript variable to html textbox

instead of

_x000D_

document.getElementById("txtBillingGroupName").value = groupName;

_x000D_

You can use

_x000D_

$("#txtBillingGroupName").val(groupName);

_x000D_

instead of groupName you can pass string value like "Group1"

What is the naming convention in Python for variable and function names?

See Python PEP 8: Function and Variable Names:

Function names should be lowercase, with words separated by underscores as necessary to improve readability.

Variable names follow the same convention as function names.

mixedCase is allowed only in contexts where that's already the prevailing style (e.g. threading.py), to retain backwards compatibility.

Non-static variable cannot be referenced from a static context

The very basic thing is static variables or static methods are at class level. Class level variables or methods gets loaded prior to instance level methods or variables.And obviously the thing which is not loaded can not be used. So java compiler not letting the things to be handled at run time resolves at compile time. That's why it is giving you error non-static things can not be referred from static context. You just need to read about Class Level Scope, Instance Level Scope and Local Scope.

How would I access variables from one class to another?

var1 and var2 is an Instance variables of ClassA. Create an Instance of ClassB and when calling the methodA it will check the methodA in Child class (ClassB) first, If methodA is not present in ClassB you need to invoke the ClassA by using the super() method which will get you all the methods implemented in ClassA. Now, you can access all the methods and attributes of ClassB.

class ClassA(object):
    def __init__(self):
        self.var1 = 1
        self.var2 = 2

    def methodA(self):
        self.var1 = self.var1 + self.var2
        return self.var1


class ClassB(ClassA):
    def __init__(self):
        super().__init__()
        print("var1",self.var1)
        print("var2",self.var2)


object1 = ClassB()
sum = object1.methodA()
print(sum)

What is the PHP syntax to check "is not null" or an empty string?

Use empty(). It checks for both empty strings and null.

if (!empty($_POST['user'])) {
  // do stuff
}

From the manual:

The following things are considered to be empty:

"" (an empty string)  
0 (0 as an integer)  
0.0 (0 as a float)  
"0" (0 as a string)    
NULL  
FALSE  
array() (an empty array)  
var $var; (a variable declared, but without a value in a class)

When to create variables (memory management)

It's really a matter of opinion. In your example, System.out.println(5) would be slightly more efficient, as you only refer to the number once and never change it. As was said in a comment, int is a primitive type and not a reference - thus it doesn't take up much space. However, you might want to set actual reference variables to null only if they are used in a very complicated method. All local reference variables are garbage collected when the method they are declared in returns.

How do you know a variable type in java?

I agree with what Joachim Sauer said, not possible to know (the variable type! not value type!) unless your variable is a class attribute (and you would have to retrieve class fields, get the right field by name...)

Actually for me it's totally impossible that any a.xxx().yyy() method give you the right answer since the answer would be different on the exact same object, according to the context in which you call this method...

As teehoo said, if you know at compile a defined list of types to test you can use instanceof but you will also get subclasses returning true...

One possible solution would also be to inspire yourself from the implementation of java.lang.reflect.Field and create your own Field class, and then declare all your local variables as this custom Field implementation... but you'd better find another solution, i really wonder why you need the variable type, and not just the value type?

Capturing multiple line output into a Bash variable

How about this, it will read each line to a variable and that can be used subsequently ! say myscript output is redirected to a file called myscript_output

awk '{while ( (getline var < "myscript_output") >0){print var;} close ("myscript_output");}'

Convert string to variable name in JavaScript

You can do like this

_x000D_

var name = "foo";_x000D_
var value = "Hello foos";_x000D_
eval("var "+name+" = '"+value+"';");_x000D_
alert(foo);

_x000D_

How to define a variable in a Dockerfile?

To my knowledge, only ENV allows that, as mentioned in "Environment replacement"

Environment variables (declared with the ENV statement) can also be used in certain instructions as variables to be interpreted by the Dockerfile.

They have to be environment variables in order to be redeclared in each new containers created for each line of the Dockerfile by docker build.

In other words, those variables aren't interpreted directly in a Dockerfile, but in a container created for a Dockerfile line, hence the use of environment variable.

This day, I use both ARG (docker 1.10+, and docker build --build-arg var=value) and ENV.
Using ARG alone means your variable is visible at build time, not at runtime.

My Dockerfile usually has:

ARG var
ENV var=${var}

In your case, ARG is enough: I use it typically for setting http_proxy variable, that docker build needs for accessing internet at build time.

How do you create different variable names while in a loop?

I think the challenge here is not to call upon global()

I would personally define a list for your (dynamic) variables to be held and then append to it within a for loop. Then use a separate for loop to view each entry or even execute other operations.

Here is an example - I have a number of network switches (say between 2 and 8) at various BRanches. Now I need to ensure I have a way to determining how many switches are available (or alive - ping test) at any given branch and then perform some operations on them.

Here is my code:

import requests
import sys

def switch_name(branchNum):
    # s is an empty list to start with
    s = []
    #this FOR loop is purely for creating and storing the dynamic variable names in s
    for x in range(1,8,+1):
        s.append("BR" + str(branchNum) + "SW0" + str(x))

    #this FOR loop is used to read each of the switch in list s and perform operations on
    for i in s:
        print(i,"\n")
        # other operations can be executed here too for each switch (i) - like SSH in using paramiko and changing switch interface VLAN etc.


def main():  

    # for example's sake - hard coding the site code
    branchNum= "123"
    switch_name(branchNum)


if __name__ == '__main__':
    main()

Output is:

BR123SW01

BR123SW02

BR123SW03

BR123SW04

BR123SW05

BR123SW06

BR123SW07

How can I check if an element exists in the visible DOM?

Use querySelectorAll with forEach,

document.querySelectorAll('.my-element').forEach((element) => {
  element.classList.add('new-class');
});

as the opposite of:

const myElement = document.querySelector('.my-element');
if (myElement) {
  element.classList.add('new-class');
}

How do I check if a variable exists?

A way that often works well for handling this kind of situation is to not explicitly check if the variable exists but just go ahead and wrap the first usage of the possibly non-existing variable in a try/except NameError:

# Search for entry.
for x in y:
  if x == 3:
    found = x

# Work with found entry.
try:
  print('Found: {0}'.format(found))
except NameError:
  print('Not found')
else:
  # Handle rest of Found case here
  ...

Increment variable value by 1 ( shell programming)

There are more than one way to increment a variable in bash, but what you tried is not correct.

You can use for example arithmetic expansion:

i=$((i+1))

or only:

((i=i+1))

or:

((i+=1))

or even:

((i++))

Or you can use let:

let "i=i+1"

or only:

let "i+=1"

or even:

let "i++"

How to check if type of a variable is string?

you can do:

var = 1
if type(var) == int:
   print('your variable is an integer')

or:

var2 = 'this is variable #2'
if type(var2) == str:
    print('your variable is a string')
else:
    print('your variable IS NOT a string')

hope this helps!

php - insert a variable in an echo string

echo '<p class="paragraph'.$i.'"></p>';

const vs constexpr on variables

A constexpr symbolic constant must be given a value that is known at compile time. For example:

?constexpr int max = 100; 
void use(int n)
{
    constexpr int c1 = max+7; // OK: c1 is 107
    constexpr int c2 = n+7;   // Error: we don’t know the value of c2
    // ...
}

To handle cases where the value of a “variable” that is initialized with a value that is not known at compile time but never changes after initialization, C++ offers a second form of constant (a const). For Example:

?constexpr int max = 100; 
void use(int n)
{
    constexpr int c1 = max+7; // OK: c1 is 107
    const int c2 = n+7; // OK, but don’t try to change the value of c2
    // ...
    c2 = 7; // error: c2 is a const
}

Such “const variables” are very common for two reasons:

C++98 did not have constexpr, so people used const.
List item “Variables” that are not constant expressions (their value is not known at compile time) but do not change values after initialization are in themselves widely useful.

Reference : "Programming: Principles and Practice Using C++" by Stroustrup

Insert variable into Header Location PHP

We can also use this with the $_GET method

$employee_id = 'EMP-1234';

header('Location: employee.php?id='.$employee_id);

How do you check if a variable is an array in JavaScript?

I personally like Peter's suggestion: https://stackoverflow.com/a/767499/414784 (for ECMAScript 3. For ECMAScript 5, use Array.isArray())

Comments on the post indicate, however, that if toString() is changed at all, that way of checking an array will fail. If you really want to be specific and make sure toString() has not been changed, and there are no problems with the objects class attribute ([object Array] is the class attribute of an object that is an array), then I recommend doing something like this:

//see if toString returns proper class attributes of objects that are arrays
//returns -1 if it fails test
//returns true if it passes test and it's an array
//returns false if it passes test and it's not an array
function is_array(o)
{
    // make sure an array has a class attribute of [object Array]
    var check_class = Object.prototype.toString.call([]);
    if(check_class === '[object Array]')
    {
        // test passed, now check
        return Object.prototype.toString.call(o) === '[object Array]';
    }
    else
    {
        // may want to change return value to something more desirable
        return -1; 
    }
}

Note that in JavaScript The Definitive Guide 6th edition, 7.10, it says Array.isArray() is implemented using Object.prototype.toString.call() in ECMAScript 5. Also note that if you're going to worry about toString()'s implementation changing, you should also worry about every other built in method changing too. Why use push()? Someone can change it! Such an approach is silly. The above check is an offered solution to those worried about toString() changing, but I believe the check is unnecessary.

Is it necessary to assign a string to a variable before comparing it to another?

if ([statusString isEqualToString:@"Wrong"]) {
    // do something
}

bash script use cut command at variable and store result at another variable

You can avoid the loop and cut etc by using:

awk -F ':' '{system("ping " $1);}' config.txt

However it would be better if you post a snippet of your config.txt

Windows 7 environment variable not working in path

I had this problem in Windows 10 and it seemed to be solved after I closed "explorer.exe" in the Task Manager.

Removing spaces from a variable input using PowerShell 4.0

You also have the Trim, TrimEnd and TrimStart methods of the System.String class. The trim method will strip whitespace (with a couple of Unicode quirks) from the leading and trailing portion of the string while allowing you to optionally specify the characters to remove.

#Note there are spaces at the beginning and end
Write-Host " ! This is a test string !%^ "
 ! This is a test string !%^
#Strips standard whitespace
Write-Host " ! This is a test string !%^ ".Trim()
! This is a test string !%^
#Strips the characters I specified
Write-Host " ! This is a test string !%^ ".Trim('!',' ')
This is a test string !%^
#Now removing ^ as well
Write-Host " ! This is a test string !%^ ".Trim('!',' ','^')
This is a test string !%
Write-Host " ! This is a test string !%^ ".Trim('!',' ','^','%')
This is a test string
#Powershell even casts strings to character arrays for you
Write-Host " ! This is a test string !%^ ".Trim('! ^%')
This is a test string

TrimStart and TrimEnd work the same way just only trimming the start or end of the string.

Is it better in C++ to pass by value or pass by constant reference?

As a rule of thumb, value for non-class types and const reference for classes. If a class is really small it's probably better to pass by value, but the difference is minimal. What you really want to avoid is passing some gigantic class by value and having it all duplicated - this will make a huge difference if you're passing, say, a std::vector with quite a few elements in it.

How to use ES6 Fat Arrow to .filter() an array of objects

You can't implicitly return with an if, you would need the braces:

let adults = family.filter(person => { if (person.age > 18) return person} );

It can be simplified though:

let adults = family.filter(person => person.age > 18);

Add directives from directive in AngularJS

I wanted to add my solution since the accepted one didn't quite work for me.

I needed to add a directive but also keep mine on the element.

In this example I am adding a simple ng-style directive to the element. To prevent infinite compile loops and allowing me to keep my directive I added a check to see if what I added was present before recompiling the element.

angular.module('some.directive', [])
.directive('someDirective', ['$compile',function($compile){
    return {
        priority: 1001,
        controller: ['$scope', '$element', '$attrs', '$transclude' ,function($scope, $element, $attrs, $transclude) {

            // controller code here

        }],
        compile: function(element, attributes){
            var compile = false;

            //check to see if the target directive was already added
            if(!element.attr('ng-style')){
                //add the target directive
                element.attr('ng-style', "{'width':'200px'}");
                compile = true;
            }
            return {
                pre: function preLink(scope, iElement, iAttrs, controller) {  },
                post: function postLink(scope, iElement, iAttrs, controller) {
                    if(compile){
                        $compile(iElement)(scope);
                    }
                }
            };
        }
    };
}]);

Binding a generic list to a repeater - ASP.NET

Code Behind:

public class Friends
{
    public string   ID      { get; set; }
    public string   Name    { get; set; }
    public string   Image   { get; set; }
}

protected void Page_Load(object sender, EventArgs e)
{
        List <Friends> friendsList = new List<Friends>();

        foreach (var friend  in friendz)
        {
            friendsList.Add(
                new Friends { ID = friend.id, Name = friend.name }    
            );

        }

        this.rptFriends.DataSource = friendsList;
        this.rptFriends.DataBind();
}

.aspx Page

<asp:Repeater ID="rptFriends" runat="server">
            <HeaderTemplate>
                <table border="0" cellpadding="0" cellspacing="0">
                    <thead>
                        <tr>
                            <th>ID</th>
                            <th>Name</th>
                        </tr>
                    </thead>
                    <tbody>
            </HeaderTemplate>
            <ItemTemplate>
                    <tr>
                        <td><%# Eval("ID") %></td>
                        <td><%# Eval("Name") %></td>
                    </tr>
            </ItemTemplate>
            <FooterTemplate>
                    </tbody>
                </table>
            </FooterTemplate>
        </asp:Repeater>

Python OpenCV2 (cv2) wrapper to get image size?

I'm afraid there is no "better" way to get this size, however it's not that much pain.

Of course your code should be safe for both binary/mono images as well as multi-channel ones, but the principal dimensions of the image always come first in the numpy array's shape. If you opt for readability, or don't want to bother typing this, you can wrap it up in a function, and give it a name you like, e.g. cv_size:

import numpy as np
import cv2

# ...

def cv_size(img):
    return tuple(img.shape[1::-1])

If you're on a terminal / ipython, you can also express it with a lambda:

>>> cv_size = lambda img: tuple(img.shape[1::-1])
>>> cv_size(img)
(640, 480)

Writing functions with def is not fun while working interactively.

Edit

Originally I thought that using [:2] was OK, but the numpy shape is (height, width[, depth]), and we need (width, height), as e.g. cv2.resize expects, so - we must use [1::-1]. Even less memorable than [:2]. And who remembers reverse slicing anyway?

Show hide div using codebehind

I was having a problem where setting element.Visible = true in my code behind wasn't having any effect on the actual screen. The solution for me was to wrap the area of my page where I wanted to show the div in an ASP UpdatePanel, which is used to cause partial screen updates.

http://msdn.microsoft.com/en-us/library/bb399001.aspx

Having the element runat=server gave me access to it from the codebehind, and placing it in the UpdatePanel let it actually be updated on the screen.

How to plot a 2D FFT in Matlab?

Here is an example from my HOW TO Matlab page:

close all; clear all;

img   = imread('lena.tif','tif');
imagesc(img)
img   = fftshift(img(:,:,2));
F     = fft2(img);

figure;

imagesc(100*log(1+abs(fftshift(F)))); colormap(gray); 
title('magnitude spectrum');

figure;
imagesc(angle(F));  colormap(gray);
title('phase spectrum');

This gives the magnitude spectrum and phase spectrum of the image. I used a color image, but you can easily adjust it to use gray image as well.

ps. I just noticed that on Matlab 2012a the above image is no longer included. So, just replace the first line above with say

img = imread('ngc6543a.jpg');

and it will work. I used an older version of Matlab to make the above example and just copied it here.

On the scaling factor

When we plot the 2D Fourier transform magnitude, we need to scale the pixel values using log transform to expand the range of the dark pixels into the bright region so we can better see the transform. We use a c value in the equation

s = c log(1+r)

There is no known way to pre detrmine this scale that I know. Just need to try different values to get on you like. I used 100 in the above example.

enter image description here

Adding files to java classpath at runtime

Try this one on for size.

private static void addSoftwareLibrary(File file) throws Exception {
    Method method = URLClassLoader.class.getDeclaredMethod("addURL", new Class[]{URL.class});
    method.setAccessible(true);
    method.invoke(ClassLoader.getSystemClassLoader(), new Object[]{file.toURI().toURL()});
}

This edits the system class loader to include the given library jar. It is pretty ugly, but it works.

How to display gpg key details without importing it?

You may also use --keyid-format switch to show short or long key ID:

$ gpg2 -n --with-fingerprint --keyid-format=short --show-keys <filename>

which outputs like this (example from PostgreSQL CentOS repo key):

pub   dsa1024/442DF0F8 2008-01-08 [SCA]                                                                       ¦
      Key fingerprint = 68C9 E2B9 1A37 D136 FE74  D176 1F16 D2E1 442D F0F8                                    ¦              honor-keyserver-url
uid                    PostgreSQL RPM Building Project <[email protected]>                      ¦                     When  using --refresh-keys, if the key in question has a preferred keyserver URL, then use that
sub   elg2048/D43F1AF8 2008-01-08 [E]

Using the AND and NOT Operator in Python

You should write :

if (self.a != 0) and (self.b != 0) :

"&" is the bit wise operator and does not suit for boolean operations. The equivalent of "&&" is "and" in Python.

A shorter way to check what you want is to use the "in" operator :

if 0 not in (self.a, self.b) :

You can check if anything is part of a an iterable with "in", it works for :

Tuples. I.E : "foo" in ("foo", 1, c, etc) will return true
Lists. I.E : "foo" in ["foo", 1, c, etc] will return true
Strings. I.E : "a" in "ago" will return true
Dict. I.E : "foo" in {"foo" : "bar"} will return true

As an answer to the comments :

Yes, using "in" is slower since you are creating an Tuple object, but really performances are not an issue here, plus readability matters a lot in Python.

For the triangle check, it's easier to read :

0 not in (self.a, self.b, self.c)

Than

(self.a != 0) and (self.b != 0) and (self.c != 0)

It's easier to refactor too.

Of course, in this example, it really is not that important, it's very simple snippet. But this style leads to a Pythonic code, which leads to a happier programmer (and losing weight, improving sex life, etc.) on big programs.

How to take a screenshot programmatically on iOS

I'm answering this question as it's a highly viewed, and there are many answers out there plus there's Swift and Obj-C.

Disclaimer This is not my code, nor my answers, this is only to help people that land here find a quick answer. There are links to the original answers to give credit where credit is due!! Please honor the original answers with a +1 if you use their answer!

Using QuartzCore

#import <QuartzCore/QuartzCore.h> 

if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
    UIGraphicsBeginImageContextWithOptions(self.window.bounds.size, NO, [UIScreen mainScreen].scale);
} else {
    UIGraphicsBeginImageContext(self.window.bounds.size);
}

[self.window.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSData *imageData = UIImagePNGRepresentation(image);
if (imageData) {
    [imageData writeToFile:@"screenshot.png" atomically:YES];
} else {
    NSLog(@"error while taking screenshot");
}

In Swift

func captureScreen() -> UIImage
{

    UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, false, 0);

    self.view.drawViewHierarchyInRect(view.bounds, afterScreenUpdates: true)

    let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return image
}

Note: As the nature with programming, updates may need to be done so please edit or let me know! *Also if I failed to include an answer/method worth including feel free to let me know as well!

How to create a generic array in Java?

If you really want to wrap a generic array of fixed size you will have a method to add data to that array, hence you can initialize properly the array there doing something like this:

import java.lang.reflect.Array;

class Stack<T> {
    private T[] array = null;
    private final int capacity = 10; // fixed or pass it in the constructor
    private int pos = 0;

    public void push(T value) {
        if (value == null)
            throw new IllegalArgumentException("Stack does not accept nulls");
        if (array == null)
            array = (T[]) Array.newInstance(value.getClass(), capacity);
        // put logic: e.g.
        if(pos == capacity)
             throw new IllegalStateException("push on full stack");
        array[pos++] = value;
    }

    public T pop() throws IllegalStateException {
        if (pos == 0)
            throw new IllegalStateException("pop on empty stack");
        return array[--pos];
    }
}

in this case you use a java.lang.reflect.Array.newInstance to create the array, and it will not be an Object[], but a real T[]. You should not worry of it not being final, since it is managed inside your class. Note that you need a non null object on the push() to be able to get the type to use, so I added a check on the data you push and throw an exception there.

Still this is somewhat pointless: you store data via push and it is the signature of the method that guarantees only T elements will enter. So it is more or less irrelevant that the array is Object[] or T[].

PHP header(Location: ...): Force URL change in address bar

use

header("Location: index.php"); //this work in my site

read more on header() at php documentation.

HtmlSpecialChars equivalent in Javascript?

function htmlspecialchars(str) {
 if (typeof(str) == "string") {
  str = str.replace(/&/g, "&amp;"); /* must do &amp; first */
  str = str.replace(/"/g, "&quot;");
  str = str.replace(/'/g, "&#039;");
  str = str.replace(/</g, "&lt;");
  str = str.replace(/>/g, "&gt;");
  }
 return str;
 }

height: calc(100%) not working correctly in CSS

try setting both html and body to height 100%;

html, body {background: blue; height:100%;}

how to find seconds since 1970 in java

Based on your desire that 1317427200 be the output, there are several layers of issue to address.

First as others have mentioned, java already uses a UTC 1/1/1970 epoch. There is normally no need to calculate the epoch and perform subtraction unless you have weird locale rules.
Second, when you create a new Calendar it's initialized to 'now' so it includes the time of day. Changing the year/month/day doesn't affect the time of day fields. So if you want it to represent midnight of the date, you need to zero out the calendar before you set the date.
Third, you haven't specified how you're supposed to handle time zones. Daylight Savings can cause differences in the absolute number of seconds represented by a particular calendar-on-the-wall-date, depending on where your JVM is running. Since epoch is in UTC, we probably want to work in UTC times? You may need to seek clarification from the makers of the system you're interfacing with.
Fourth, months in Java are zero indexed. January is 0, October is 9.

Putting all that together

Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calendar.clear();
calendar.set(2011, Calendar.OCTOBER, 1);
long secondsSinceEpoch = calendar.getTimeInMillis() / 1000L;

that will give you 1317427200

C++ style cast from unsigned char * to const char *

Try reinterpret_cast

unsigned char *foo();
std::string str;
str.append(reinterpret_cast<const char*>(foo()));

How should I pass an int into stringWithFormat?

And for comedic value:

label.text = [NSString stringWithFormat:@"%@", [NSNumber numberWithInt:count]];

(Though it could be useful if one day you're dealing with NSNumber's)

How does one get started with procedural generation?

You should probably start with a little theory and simple examples such as the midpoint displacement algorithm. You should also learn a little about Perlin Noise if you are interested in generating graphics. I used this to get me started with my final year project on procedural generation.

Fractals are closely related to procedural generation.

Terragen and SpeedTree will show you some amazing possibilities of procedural generation.

Procedural generation is a technique that can be used in any language (it is definitely not restricted to procedural languages such as C, as it can be used in OO languages such as Java, and Logic languages such as Prolog). A good understanding of recursion in any language will strengthen your grasp of Procedural Generation.

As for 'serious' or non-game code, procedural generation techniques have been used to:

simulate the growth of cities in order to plan for traffic management
to simulate the growth of blood vessels
SpeedTree is used in movies and architectural presentations

How can I insert into a BLOB column from an insert statement in sqldeveloper?

Yes, it's possible, e.g. using the implicit conversion from RAW to BLOB:

insert into blob_fun values(1, hextoraw('453d7a34'));

453d7a34 is a string of hexadecimal values, which is first explicitly converted to the RAW data type and then inserted into the BLOB column. The result is a BLOB value of 4 bytes.

Adding an external directory to Tomcat classpath

I might be a bit late for the party but I follow below steps to make it fully configurable using IntelliJ's way of in-IDE app test. I believe the best way to go with is to Combine below with @BelusC's answer.

1. run the application using IDE's tomcat run config. 
2. ps -ef | grep -i tomcat //this will give you a good idea about what the ide doing actually.
3. Copy the -Dcatalina.base parameter value from the command. this is your application specific catalina base. In this folder you can play with catalina.properties, application root path etc.. basically everything you have been doing is doable here too.

How to iterate through two lists in parallel?

Python 3:

import itertools as it

for foo, bar in list(it.izip_longest(list1, list2)):
    print(foo, bar)

"NoClassDefFoundError: Could not initialize class" error

I had faced the same issue, because the jar library was copied by other Linux user(root), and the logged in user(process) did not have sufficient privilege to read the jar file content.

MySQL "WITH" clause

Update: MySQL 8.0 is finally getting the feature of common table expressions, including recursive CTEs.

Here's a blog announcing it: http://mysqlserverteam.com/mysql-8-0-labs-recursive-common-table-expressions-in-mysql-ctes/

Below is my earlier answer, which I originally wrote in 2008.

MySQL 5.x does not support queries using the WITH syntax defined in SQL-99, also called Common Table Expressions.

This has been a feature request for MySQL since January 2006: http://bugs.mysql.com/bug.php?id=16244

Other RDBMS products that support common table expressions:

Oracle 9i release 2 and later:
http://www.oracle-base.com/articles/misc/with-clause.php
Microsoft SQL Server 2005 and later:
http://msdn.microsoft.com/en-us/library/ms190766(v=sql.90).aspx
IBM DB2 UDB 8 and later:
http://publib.boulder.ibm.com/infocenter/db2luw/v8/index.jsp?topic=/com.ibm.db2.udb.doc/admin/r0000879.htm
PostgreSQL 8.4 and later:
https://www.postgresql.org/docs/current/static/queries-with.html
Sybase 11 and later:
http://dcx.sybase.com/1100/en/dbusage_en11/commontblexpr-s-5414852.html
SQLite 3.8.3 and later:
http://sqlite.org/lang_with.html
HSQLDB:
http://hsqldb.org/doc/guide/dataaccess-chapt.html#dac_with_clause
Firebird 2.1 and later (the first Open Source DBMS to support recursive queries): http://www.firebirdsql.org/file/documentation/release_notes/html/rlsnotes210.html#rnfb210-cte
H2 Database (but only recursive):
http://www.h2database.com/html/advanced.html#recursive_queries
Informix 14.10 and later: https://www.ibm.com/support/knowledgecenter/SSGU8G_14.1.0/com.ibm.sqls.doc/ids_sqs_with.htm

How can I stage and commit all files, including newly added files, using a single command?

I have in my config two aliases:

alias.foo=commit -a -m 'none'
alias.coa=commit -a -m

if I am too lazy I just commit all changes with

git foo

and just to do a quick commit

git coa "my changes are..."

coa stands for "commit all"

rotate image with css

The trouble looks like the image isn't square and the browser adjusts as such. After rotation ensure the dimensions are retained by changing the image margin.

.imagetest img {
  transform: rotate(270deg);
  ...
  margin: 10px 0px;
}

The amount will depend on the difference in height x width of the image. You may also need to add display:inline-block; or display:block to get it to recognize the margin parameter.

How to remove button shadow (android)

Kotlin

stateListAnimator = null

Java

setStateListAnimator(null);

XML

android:stateListAnimator="@null"

Reverting to a previous revision using TortoiseSVN

In the TortoiseSVN context menu, select 'Update to Revision', enter the desired revision number, and voilà :)

How do you delete a column by name in data.table?

DT[,c:=NULL] # remove column c

DateTime format to SQL format using C#

Your problem is in the "Date" property that truncates DateTime to date only. You could put the conversion like this:

DateTime myDateTime = DateTime.Now;
string sqlFormattedDate = myDateTime.ToString("yyyy-MM-dd HH:mm:ss"); // <- No Date.ToString()!

Rename a column in MySQL

https://dev.mysql.com/doc/refman/8.0/en/alter-table.html

For MySQL 8

alter table creditReportXml_temp change column applicationID applicantID int(11);

How to gzip all files in all sub-directories into one compressed file in bash

@amitchhajer 's post works for GNU tar. If someone finds this post and needs it to work on a NON GNU system, they can do this:

tar cvf - folderToCompress | gzip > compressFileName

To expand the archive:

zcat compressFileName | tar xvf -

Breaking out of a nested loop

It seems to me like people dislike a goto statement a lot, so I felt the need to straighten this out a bit.

I believe the 'emotions' people have about goto eventually boil down to understanding of code and (misconceptions) about possible performance implications. Before answering the question, I will therefore first go into some of the details on how it's compiled.

As we all know, C# is compiled to IL, which is then compiled to assembler using an SSA compiler. I'll give a bit of insights into how this all works, and then try to answer the question itself.

From C# to IL

First we need a piece of C# code. Let's start simple:

foreach (var item in array)
{
    // ... 
    break;
    // ...
}

I'll do this step by step to give you a good idea of what happens under the hood.

First translation: from foreach to the equivalent for loop (Note: I'm using an array here, because I don't want to get into details of IDisposable -- in which case I'd also have to use an IEnumerable):

for (int i=0; i<array.Length; ++i)
{
    var item = array[i];
    // ...
    break;
    // ...
}

Second translation: the for and break is translated into an easier equivalent:

int i=0;
while (i < array.Length)
{
    var item = array[i];
    // ...
    break;
    // ...
    ++i;
}

And third translation (this is the equivalent of the IL code): we change break and while into a branch:

    int i=0; // for initialization

startLoop:
    if (i >= array.Length) // for condition
    {
        goto exitLoop;
    }
    var item = array[i];
    // ...
    goto exitLoop; // break
    // ...
    ++i;           // for post-expression
    goto startLoop;

While the compiler does these things in a single step, it gives you insight into the process. The IL code that evolves from the C# program is the literal translation of the last C# code. You can see for yourself here: https://dotnetfiddle.net/QaiLRz (click 'view IL')

Now, one thing you have observed here is that during the process, the code becomes more complex. The easiest way to observe this is by the fact that we needed more and more code to ackomplish the same thing. You might also argue that foreach, for, while and break are actually short-hands for goto, which is partly true.

From IL to Assembler

The .NET JIT compiler is an SSA compiler. I won't go into all the details of SSA form here and how to create an optimizing compiler, it's just too much, but can give a basic understanding about what will happen. For a deeper understanding, it's best to start reading up on optimizing compilers (I do like this book for a brief introduction: http://ssabook.gforge.inria.fr/latest/book.pdf ) and LLVM (llvm.org).

Every optimizing compiler relies on the fact that code is easy and follows predictable patterns. In the case of FOR loops, we use graph theory to analyze branches, and then optimize things like cycli in our branches (e.g. branches backwards).

However, we now have forward branches to implement our loops. As you might have guessed, this is actually one of the first steps the JIT is going to fix, like this:

    int i=0; // for initialization

    if (i >= array.Length) // for condition
    {
        goto endOfLoop;
    }

startLoop:
    var item = array[i];
    // ...
    goto endOfLoop; // break
    // ...
    ++i;           // for post-expression

    if (i >= array.Length) // for condition
    {
        goto startLoop;
    }

endOfLoop:
    // ...

As you can see, we now have a backward branch, which is our little loop. The only thing that's still nasty here is the branch that we ended up with due to our break statement. In some cases, we can move this in the same way, but in others it's there to stay.

So why does the compiler do this? Well, if we can unroll the loop, we might be able to vectorize it. We might even be able to proof that there's just constants being added, which means our whole loop could vanish into thin air. To summarize: by making the patterns predictable (by making the branches predictable), we can proof that certain conditions hold in our loop, which means we can do magic during the JIT optimization.

However, branches tend to break those nice predictable patterns, which is something optimizers therefore kind-a dislike. Break, continue, goto - they all intend to break these predictable patterns- and are therefore not really 'nice'.

You should also realize at this point that a simple foreach is more predictable then a bunch of goto statements that go all over the place. In terms of (1) readability and (2) from an optimizer perspective, it's both the better solution.

Another thing worth mentioning is that it's very relevant for optimizing compilers to assign registers to variables (a process called register allocation). As you might know, there's only a finite number of registers in your CPU and they are by far the fastest pieces of memory in your hardware. Variables used in code that's in the inner-most loop, are more likely to get a register assigned, while variables outside of your loop are less important (because this code is probably hit less).

Help, too much complexity... what should I do?

The bottom line is that you should always use the language constructs you have at your disposal, which will usually (implictly) build predictable patterns for your compiler. Try to avoid strange branches if possible (specifically: break, continue, goto or a return in the middle of nothing).

The good news here is that these predictable patterns are both easy to read (for humans) and easy to spot (for compilers).

One of those patterns is called SESE, which stands for Single Entry Single Exit.

And now we get to the real question.

Imagine that you have something like this:

// a is a variable.

for (int i=0; i<100; ++i) 
{
  for (int j=0; j<100; ++j)
  {
     // ...

     if (i*j > a) 
     {
        // break everything
     }
  }
}

The easiest way to make this a predictable pattern is to simply eliminate the if completely:

int i, j;
for (i=0; i<100 && i*j <= a; ++i) 
{
  for (j=0; j<100 && i*j <= a; ++j)
  {
     // ...
  }
}

In other cases you can also split the method into 2 methods:

// Outer loop in method 1:

for (i=0; i<100 && processInner(i); ++i) 
{
}

private bool processInner(int i)
{
  int j;
  for (j=0; j<100 && i*j <= a; ++j)
  {
     // ...
  }
  return i*j<=a;
}

Temporary variables? Good, bad or ugly?

You might even decide to return a boolean from within the loop (but I personally prefer the SESE form because that's how the compiler will see it and I think it's cleaner to read).

Some people think it's cleaner to use a temporary variable, and propose a solution like this:

bool more = true;
for (int i=0; i<100; ++i) 
{
  for (int j=0; j<100; ++j) 
  {
     // ...
     if (i*j > a) { more = false; break; } // yuck.
     // ...
  }
  if (!more) { break; } // yuck.
  // ...
}
// ...

I personally am opposed to this approach. Look again on how the code is compiled. Now think about what this will do with these nice, predictable patterns. Get the picture?

Right, let me spell it out. What will happen is that:

The compiler will write out everything as branches.
As an optimization step, the compiler will do data flow analysis in an attempt to remove the strange more variable that only happens to be used in control flow.
If succesful, the variable more will be eliminated from the program, and only branches remain. These branches will be optimized, so you will get only a single branch out of the inner loop.
If unsuccesful, the variable more is definitely used in the inner-most loop, so if the compiler won't optimize it away, it has a high chance to be allocated to a register (which eats up valuable register memory).

So, to summarize: the optimizer in your compiler will go into a hell of a lot of trouble to figure out that more is only used for the control flow, and in the best case scenario will translate it to a single branch outside of the outer for loop.

In other words, the best case scenario is that it will end up with the equivalent of this:

for (int i=0; i<100; ++i) 
{
  for (int j=0; j<100; ++j)
  {
     // ...
     if (i*j > a) { goto exitLoop; } // perhaps add a comment
     // ...
  }
  // ...
}
exitLoop:

// ...

My personal opinion on this is quite simple: if this is what we intended all along, let's make the world easier for both the compiler and readability, and write that right away.

tl;dr:

Bottom line:

Use a simple condition in your for loop if possible. Stick to the high-level language constructs you have at your disposal as much as possible.
If everything fails and you're left with either goto or bool more, prefer the former.

Set the default value in dropdownlist using jQuery

val() should handle both cases

  <option value="1">it's me</option>      


$('select').val('1'); // selects "it's me"

$('select').val("it's me"); // also selects "it's me"

Is it possible to listen to a "style change" event?

The declaration of your event object has to be inside your new css function. Otherwise the event can only be fired once.

(function() {
    orig = $.fn.css;
    $.fn.css = function() {
        var ev = new $.Event('style');
        orig.apply(this, arguments);
        $(this).trigger(ev);
    }
})();

Can an Android NFC phone act as an NFC tag?

Check the Host-based Card Emulation (HCE) NFC mode available in Android 4.4.

API guide: https://developer.android.com/guide/topics/connectivity/nfc/hce.html

Adding hours to JavaScript Date object?

JavaScript itself has terrible Date/Time API's. Nonetheless, you can do this in pure JavaScript:

Date.prototype.addHours = function(h) {
  this.setTime(this.getTime() + (h*60*60*1000));
  return this;
}

Test a string for a substring

There are several other ways, besides using the in operator (easiest):

index()

>>> try:
...   "xxxxABCDyyyy".index("test")
... except ValueError:
...   print "not found"
... else:
...   print "found"
...
not found

find()

>>> if "xxxxABCDyyyy".find("ABCD") != -1:
...   print "found"
...
found

re

>>> import re
>>> if re.search("ABCD" , "xxxxABCDyyyy"):
...  print "found"
...
found

How to find out the number of CPUs using python

You can also use "joblib" for this purpose.

import joblib
print joblib.cpu_count()

This method will give you the number of cpus in the system. joblib needs to be installed though. More information on joblib can be found here https://pythonhosted.org/joblib/parallel.html

Alternatively you can use numexpr package of python. It has lot of simple functions helpful for getting information about the system cpu.

import numexpr as ne
print ne.detect_number_of_cores()

Accessing Arrays inside Arrays In PHP

Study up on multidimensional arrays. This question might help.

File inside jar is not visible for spring

The error message is correct (if not very helpful): the file we're trying to load is not a file on the filesystem, but a chunk of bytes in a ZIP inside a ZIP.

Through experimentation (Java 11, Spring Boot 2.3.x), I found this to work without changing any config or even a wildcard:

var resource = ResourceUtils.getURL("classpath:some/resource/in/a/dependency");
new BufferedReader(
  new InputStreamReader(resource.openStream())
).lines().forEach(System.out::println);

Implementing two interfaces in a class with same method. Which interface method is overridden?

Well if they are both the same it doesn't matter. It implements both of them with a single concrete method per interface method.

How to give ASP.NET access to a private key in a certificate in the certificate store?

I figured out how to do this in Powershell that someone asked about:

$keyname=(((gci cert:\LocalMachine\my | ? {$_.thumbprint -like $thumbprint}).PrivateKey).CspKeyContainerInfo).UniqueKeyContainerName
$keypath = $env:ProgramData + “\Microsoft\Crypto\RSA\MachineKeys\”
$fullpath=$keypath+$keyname

$Acl = Get-Acl $fullpath
$Ar = New-Object System.Security.AccessControl.FileSystemAccessRule("IIS AppPool\$iisAppPoolName", "Read", "Allow")
$Acl.SetAccessRule($Ar)
Set-Acl $fullpath $Acl

How to assign execute permission to a .sh file in windows to be executed in linux

The ZIP file format does allow to store the permission bits, but Windows programs normally ignore it. The zip utility on Cygwin however does preserve the x bit, just like it does on Linux. If you do not want to use Cygwin, you can take a source code and tweak it so that all *.sh files get the executable bit set. Or write a script like explained here

Creating dummy variables in pandas for python

Based on the official documentation:

dummies = pd.get_dummies(df['Category']).rename(columns=lambda x: 'Category_' + str(x))
df = pd.concat([df, dummies], axis=1)
df = df.drop(['Category'], inplace=True, axis=1)

There is also a nice post in the FastML blog.

Who is listening on a given TCP port on Mac OS X?

I am a Linux guy. In Linux it is extremely easy with netstat -ltpn or any combination of those letters. But in Mac OS X netstat -an | grep LISTEN is the most humane. Others are very ugly and very difficult to remember when troubleshooting.

Five equal columns in twitter bootstrap

In case you do no need the exact same width of columns you can try create 5-columns using nesting:

<div class="container">
    <div class="row">
        <div class="col-xs-5">
            <div class="row">
                <div class="col-xs-6 column">Column 1</div>
                <div class="col-xs-6 column">Column 2</div>
            </div>
        </div>
        <div class="col-xs-7">
            <div class="row">
                <div class="col-xs-4 column">Column 3</div>
                <div class="col-xs-4 column">Column 4</div>
                <div class="col-xs-4 column">Column 5</div>
            </div>
        </div>
    </div>
</div>

jsfiddle

The first two columns will have width equal 5/12 * 1/2 ~ 20.83%

The last three columns: 7/12 * 1/3 ~ 19.44%

Such hack gives the acceptable result in many cases and does not require any CSS changes (we're using only the native bootstrap classes).

What does API level mean?

This actually sums it up pretty nicely.

API Levels generally mean that as a programmer, you can communicate with the devices' built in functions and functionality. As the API level increases, functionality adds up (although some of it can get deprecated).

Choosing an API level for an application development should take at least two thing into account:

Current distribution - How many devices can actually support my application, if it was developed for API level 9, it cannot run on API level 8 and below, then "only" around 60% of devices can run it (true to the date this post was made).
Choosing a lower API level may support more devices but gain less functionality for your app. you may also work harder to achieve features you could've easily gained if you chose higher API level.

Android API levels can be divided to five main groups (not scientific, but what the heck):

Android 1.5 - 2.3 (Cupcake to Gingerbread) - (API levels 3-10) - Android made specifically for smartphones.
Android 3.0 - 3.2 (Honeycomb) (API levels 11-13) - Android made for tablets.
Android 4.0 - 4.4 (KitKat) - (API levels 14-19) - A big merge with tons of additional functionality, totally revamped Android version, for both phone and tablets.
Android 5.0 - 5.1 (Lollipop) - (API levels 21-22) - Material Design introduced.
Android 6.0 - 6.… (Marshmallow) - (API levels 23-…) - Runtime Permissions,Apache HTTP Client Removed

Python pip install fails: invalid command egg_info

This error can occur when you trying to install pycurl.

In this case you should do

sudo apt-get install libcurl4-gnutls-dev librtmp-dev

(founded here: https://gist.github.com/lxneng/1031014 )

How to Remove Array Element and Then Re-Index Array?

If you use array_merge, this will reindex the keys. The manual states:

Values in the input array with numeric keys will be renumbered with incrementing keys starting from zero in the result array.

http://php.net/manual/en/function.array-merge.php

This is where i found the original answer.

http://board.phpbuilder.com/showthread.php?10299961-Reset-index-on-array-after-unset()

How to know that a string starts/ends with a specific string in jQuery?

There is no need of jQuery to do that. You could code a jQuery wrapper but it would be useless so you should better use

var str = "Hello World";

window.alert("Starts with Hello ? " + /^Hello/i.test(str));        

window.alert("Ends with Hello ? " + /Hello$/i.test(str));

as the match() method is deprecated.

PS : the "i" flag in RegExp is optional and stands for case insensitive (so it will also return true for "hello", "hEllo", etc.).

Simple conversion between java.util.Date and XMLGregorianCalendar

Customizing the Calendar and Date while Marshaling

Step 1 : Prepare jaxb binding xml for custom properties, In this case i prepared for date and calendar

<jaxb:bindings version="2.1" xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc" 
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<jaxb:globalBindings generateElementProperty="false">
<jaxb:serializable uid="1" />
<jaxb:javaType name="java.util.Date" xmlType="xs:date"
    parseMethod="org.apache.cxf.tools.common.DataTypeAdapter.parseDate"
    printMethod="com.stech.jaxb.util.CalendarTypeConverter.printDate" />
<jaxb:javaType name="java.util.Calendar" xmlType="xs:dateTime"
    parseMethod="javax.xml.bind.DatatypeConverter.parseDateTime"
    printMethod="com.stech.jaxb.util.CalendarTypeConverter.printCalendar" />

Setp 2 : Add custom jaxb binding file to Apache or any related plugins at xsd option like mentioned below

<xsdOption>
  <xsd>${project.basedir}/src/main/resources/tutorial/xsd/yourxsdfile.xsd</xsd>
  <packagename>com.tutorial.xml.packagename</packagename>
  <bindingFile>${project.basedir}/src/main/resources/xsd/jaxbbindings.xml</bindingFile>
</xsdOption>

Setp 3 : write the code for CalendarConverter class

package com.stech.jaxb.util;

import java.text.SimpleDateFormat;

/**
 * To convert the calendar to JaxB customer format.
 * 
 */

public final class CalendarTypeConverter {

    /**
     * Calendar to custom format print to XML.
     * 
     * @param val
     * @return
     */
    public static String printCalendar(java.util.Calendar val) {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ss");
        return simpleDateFormat.format(val.getTime());
    }

    /**
     * Date to custom format print to XML.
     * 
     * @param val
     * @return
     */
    public static String printDate(java.util.Date val) {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        return simpleDateFormat.format(val);
    }
}

Setp 4 : Output

  <xmlHeader>
   <creationTime>2014-09-25T07:23:05</creationTime> Calendar class formatted

   <fileDate>2014-09-25</fileDate> - Date class formatted
</xmlHeader>

Proper way to use AJAX Post in jquery to pass model from strongly typed MVC3 view

If using MVC 5 read this solution!

I know the question specifically called for MVC 3, but I stumbled upon this page with MVC 5 and wanted to post a solution for anyone else in my situation. I tried the above solutions, but they did not work for me, the Action Filter was never reached and I couldn't figure out why. I am using version 5 in my project and ended up with the following action filter:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Mvc.Filters;

namespace SydHeller.Filters
{
    public class ValidateJSONAntiForgeryHeader : FilterAttribute, IAuthorizationFilter
    {
        public void OnAuthorization(AuthorizationContext filterContext)
        {
            string clientToken = filterContext.RequestContext.HttpContext.Request.Headers.Get(KEY_NAME);
            if (clientToken == null)
            {
                throw new HttpAntiForgeryException(string.Format("Header does not contain {0}", KEY_NAME));
            }

            string serverToken = filterContext.HttpContext.Request.Cookies.Get(KEY_NAME).Value;
            if (serverToken == null)
            {
                throw new HttpAntiForgeryException(string.Format("Cookies does not contain {0}", KEY_NAME));
            }

            System.Web.Helpers.AntiForgery.Validate(serverToken, clientToken);
        }

        private const string KEY_NAME = "__RequestVerificationToken";
    }
}

-- Make note of the using System.Web.Mvc and using System.Web.Mvc.Filters, not the http libraries (I think that is one of the things that changed with MVC v5. --

Then just apply the filter [ValidateJSONAntiForgeryHeader] to your action (or controller) and it should get called correctly.

In my layout page right above </body> I have @AntiForgery.GetHtml();

Finally, in my Razor page, I do the ajax call as follows:

var formForgeryToken = $('input[name="__RequestVerificationToken"]').val();

$.ajax({
  type: "POST",
  url: serviceURL,
  contentType: "application/json; charset=utf-8",
  dataType: "json",
  data: requestData,
  headers: {
     "__RequestVerificationToken": formForgeryToken
  },
     success: crimeDataSuccessFunc,
     error: crimeDataErrorFunc
});

Difference between a theta join, equijoin and natural join

Theta Join: When you make a query for join using any operator,(e.g., =, <, >, >= etc.), then that join query comes under Theta join.

Equi Join: When you make a query for join using equality operator only, then that join query comes under Equi join.

Example:

> SELECT * FROM Emp JOIN Dept ON Emp.DeptID = Dept.DeptID;
> SELECT * FROM Emp INNER JOIN Dept USING(DeptID)

This will show:
 _________________________________________________
| Emp.Name | Emp.DeptID | Dept.Name | Dept.DeptID |
|          |            |           |             |

Note: Equi join is also a theta join!

Natural Join: a type of Equi Join which occurs implicitly by comparing all the same names columns in both tables.

Note: here, the join result has only one column for each pair of same named columns.

Example

 SELECT * FROM Emp NATURAL JOIN Dept

This will show:
 _______________________________
| DeptID | Emp.Name | Dept.Name |
|        |          |           |

Rails 3 check if attribute changed

Check out ActiveModel::Dirty (available on all models by default). The documentation is really good, but it lets you do things such as:

@user.street1_changed? # => true/false

postgresql - sql - count of `true` values

The shortest and laziest (without casting) solution would be to use the formula:

SELECT COUNT(myCol OR NULL) FROM myTable;

Try it yourself:

SELECT COUNT(x < 7 OR NULL)
   FROM GENERATE_SERIES(0,10) t(x);

gives the same result than

SELECT SUM(CASE WHEN x < 7 THEN 1 ELSE 0 END)
   FROM GENERATE_SERIES(0,10) t(x);

How do I calculate square root in Python?

You have to write: sqrt = x**(1/2.0), otherwise an integer division is performed and the expression 1/2 returns 0.

This behavior is "normal" in Python 2.x, whereas in Python 3.x 1/2 evaluates to 0.5. If you want your Python 2.x code to behave like 3.x w.r.t. division write from __future__ import division - then 1/2 will evaluate to 0.5 and for backwards compatibility, 1//2 will evaluate to 0.

And for the record, the preferred way to calculate a square root is this:

import math
math.sqrt(x)

How to left align a fixed width string?

With the new and popular f-strings in Python 3.6, here is how we left-align say a string with 16 padding length:

string = "Stack Overflow"
print(f"{string:<16}..")
Stack Overflow  ..

If you have variable padding length:

k = 20
print(f"{string:<{k}}..")
Stack Overflow      ..

f-strings are more compact.

PHP multidimensional array search by value

Building off Jakub's excellent answer, here is a more generalized search that will allow the key to specified (not just for uid):

function searcharray($value, $key, $array) {
   foreach ($array as $k => $val) {
       if ($val[$key] == $value) {
           return $k;
       }
   }
   return null;
}

Usage: $results = searcharray('searchvalue', searchkey, $array);

how to run or install a *.jar file in windows?

The UnsupportedClassVersionError means that you are probably using (installed) an older version of Java as used to create the JAR.
Go to java.sun.com page, download and install a newer JRE (Java Runtime Environment).
if you want/need to develop with Java, you will need the JDK which includes the JRE.

Drop data frame columns by name

I keep thinking there must be a better idiom, but for subtraction of columns by name, I tend to do the following:

df <- data.frame(a=1:10, b=1:10, c=1:10, d=1:10)

# return everything except a and c
df <- df[,-match(c("a","c"),names(df))]
df

On design patterns: When should I use the singleton?

As everyone has said, a shared resource - specifically something that cannot handle concurrent access.

One specific example that I have seen, is a Lucene Search Index Writer.

sum two columns in R

tablename$column3=rowSums(cbind(tablename$column1,tablename$column2),na.rm=TRUE)

This can be used to ignore blank values in the excel sheet.
I have used for Euro stat dataset.

This example works in R:

crime_stat_data$All_theft <-rowSums(cbind(crime_stat_data$Theft,crime_stat_data$Theft_of_a_motorised_land_vehicle, crime_stat_data$Burglary, crime_stat_data$Burglary_of_private_residential_premises), na.rm=TRUE)

Generating a drop down list of timezones with PHP

Despite the number of existing answers, I've made yet another solution to this problem. The pro's of my implementation are:

The list of timezones is generated dynamically, and thus automatically updates when timezones might change (in PHP).
Timezone names are prettified. For example, "America/St_Barthelemy" becomes "America, St. Barthelemy".
Timezones are sorted on offset and name. Toland's answer only sorts on offset, resulting in unsorted groups of timezones within the same offset.
Offset information is not retrieved from DateTimeZone::listAbbreviations, since that method also returns historical timezone information. Favio's answer does use this method, which results in incorrect (historical) offsets
The list of timezones is only generated when first requested (and 'cached' using a static variable).

Here is the full code:

function timezone_list() {
    static $timezones = null;

    if ($timezones === null) {
        $timezones = [];
        $offsets = [];
        $now = new DateTime('now', new DateTimeZone('UTC'));

        foreach (DateTimeZone::listIdentifiers() as $timezone) {
            $now->setTimezone(new DateTimeZone($timezone));
            $offsets[] = $offset = $now->getOffset();
            $timezones[$timezone] = '(' . format_GMT_offset($offset) . ') ' . format_timezone_name($timezone);
        }

        array_multisort($offsets, $timezones);
    }

    return $timezones;
}

function format_GMT_offset($offset) {
    $hours = intval($offset / 3600);
    $minutes = abs(intval($offset % 3600 / 60));
    return 'GMT' . ($offset ? sprintf('%+03d:%02d', $hours, $minutes) : '');
}

function format_timezone_name($name) {
    $name = str_replace('/', ', ', $name);
    $name = str_replace('_', ' ', $name);
    $name = str_replace('St ', 'St. ', $name);
    return $name;
}

And here's an example of the output

Array
(
    [Pacific/Midway]    => (GMT-11:00) Pacific, Midway
    [Pacific/Niue]      => (GMT-11:00) Pacific, Niue
    [Pacific/Pago_Pago] => (GMT-11:00) Pacific, Pago Pago
    [America/Adak]      => (GMT-10:00) America, Adak
    [Pacific/Honolulu]  => (GMT-10:00) Pacific, Honolulu
    [Pacific/Johnston]  => (GMT-10:00) Pacific, Johnston
    [Pacific/Rarotonga] => (GMT-10:00) Pacific, Rarotonga
    [Pacific/Tahiti]    => (GMT-10:00) Pacific, Tahiti
    [Pacific/Marquesas] => (GMT-09:30) Pacific, Marquesas
    [America/Anchorage] => (GMT-09:00) America, Anchorage
    ...
)

Access cell value of datatable

public V[] getV(DataTable dtCloned)
{

    V[] objV = new V[dtCloned.Rows.Count];
    MyClasses mc = new MyClasses();
    int i = 0;
    int intError = 0;
    foreach (DataRow dr in dtCloned.Rows)
    {
        try
        {
            V vs = new V();
            vs.R = int.Parse(mc.ReplaceChar(dr["r"].ToString()).Trim());
            vs.S = Int64.Parse(mc.ReplaceChar(dr["s"].ToString()).Trim());
            objV[i] = vs;
            i++;
        }
        catch (Exception ex)
        {
            //
            DataRow row = dtError.NewRow();
            row["r"] = dr["r"].ToString();
            row["s"] = dr["s"].ToString();
            dtError.Rows.Add(row);
            intError++;
        }
    }
    return vs;
}

How to Automatically Close Alerts using Twitter Bootstrap

With delay and fade :

setTimeout(function(){
    $(".alert").each(function(index){
        $(this).delay(200*index).fadeTo(1500,0).slideUp(500,function(){
            $(this).remove();
        });
    });
},2000);

How can I revert multiple Git commits (already pushed) to a published repository?

git revert HEAD -m 1

In the above code line. "Last argument represents"

1 - reverts one commits. 2 - reverts last commits. n - reverts last n commits

git reset --hard siriwjdd

How to get query parameters from URL in Angular 5?

Simple Solution

 // in routing file
       {
            path: 'checkout/:cartId/:addressId',
            loadChildren: () => import('./pages/checkout/checkout.module').then(m => m.CheckoutPageModule)
          },

    // in Component file

            import { Router, ActivatedRoute } from '@angular/router';

                 constructor(
                      private _Router: ActivatedRoute
                  ) { }

                  ngOnInit() {
                    this.cartId = this._Router.snapshot.params.cartId;
                    this.addressId = this._Router.snapshot.params.addressId;
                    console.log(this.addressId, "addressId")
                    console.log(this.cartId, "cartId")
                  }

How can I get a list of Git branches, ordered by most recent commit?

Adds some color (since pretty-format isn't available)

[alias]
    branchdate = for-each-ref --sort=-committerdate refs/heads/ --format="%(authordate:short)%09%(objectname:short)%09%1B[0;33m%(refname:short)%1B[m%09"

How to quickly and conveniently create a one element arraylist

With Java 8 Streams:

Stream.of(object).collect(Collectors.toList())

or if you need a set:

Stream.of(object).collect(Collectors.toSet())

How to copy directories with spaces in the name

When you specify the last Directory on the path remove the last .

for example "\server\directory with space\directory with space".

that should do it.

Disable Proximity Sensor during call

If you have LineageOS 7.1.2 (and have root), try this solution from XDA.

After having tried all the solutions proposed here, none of which worked for my Nexus 4 (mako), I found one on XDA that solves the problem with the Android dialer (but not with other apps). Basically I downloaded a recompiled version of the Dialer.apk file, which simply ignores the proximity sensor and behaves in the same way as the stock dialer app does.

Rename /system/priv-app/Dialer/Dialer.apk to something, then place the downloaded file to that folder. After reboot, I had to install the new dialer manually (simply by clicking on it). So now the original app is replaced, and the calls should be handled by this new one.

[Downside: the new way to answer a call is by pulling down the status bar and clicking 'Answer' (or 'Dismiss'), the usual slider is missing. Also, you'll need to repeat this every time your Android updates to a newer version.]

How to call a web service from jQuery

You can make an AJAX request like any other requests:

$.ajax( {
type:'Get',
url:'http://mysite.com/mywebservice',
success:function(data) {
 alert(data);
}

})

Add click event on div tag using javascript

Pure Javascript

document.getElementsByClassName('drill_cursor')[0]
        .addEventListener('click', function (event) {
            // do something
        });

jQuery

$(".drill_cursor").click(function(){
//do something
});

How do you split a list into evenly sized chunks?

An old school approach that does not require itertools but still works with arbitrary generators:

def chunks(g, n):
  """divide a generator 'g' into small chunks
  Yields:
    a chunk that has 'n' or less items
  """
  n = max(1, n)
  buff = []
  for item in g:
    buff.append(item)
    if len(buff) == n:
      yield buff
      buff = []
  if buff:
    yield buff

Typescript ReferenceError: exports is not defined

my solution is a sum up of everything above with little tricks I added, basically I added this to my html code

<script>var exports = {"__esModule": true};</script>
<script src="js/file.js"></script>

this even allows you to use import instead of require if you're using electron or something, and it works fine with typescript 3.5.1, target: es3 -> esnext.

MySQL select statement with CASE or IF ELSEIF? Not sure how to get the result

Syntax:

CASE value WHEN [compare_value] THEN result 
[WHEN [compare_value] THEN result ...] 
[ELSE result] 
END

Alternative: CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...]

mysql> SELECT CASE  WHEN 2>3 THEN 'this is true' ELSE 'this is false' END; 
+-------------------------------------------------------------+
| CASE  WHEN 2>3 THEN 'this is true' ELSE 'this is false' END |
+-------------------------------------------------------------+
| this is false                                               | 
+-------------------------------------------------------------+

I am use:

SELECT  act.*,
    CASE 
        WHEN (lises.session_date IS NOT NULL AND ses.session_date IS NULL) THEN lises.location_id
        WHEN (lises.session_date IS NULL AND ses.session_date IS NOT NULL) THEN ses.location_id
        WHEN (lises.session_date IS NOT NULL AND ses.session_date IS NOT NULL AND lises.session_date>ses.session_date) THEN ses.location_id
        WHEN (lises.session_date IS NOT NULL AND ses.session_date IS NOT NULL AND lises.session_date<ses.session_date) THEN lises.location_id
    END AS location_id
FROM activity AS act
LEFT JOIN li_sessions AS lises ON lises.activity_id = act.id AND  lises.session_date >= now()
LEFT JOIN session AS ses ON  ses.activity_id = act.id AND  ses.session_date >= now()
WHERE act.id

Copy files to network computers on windows command line

Why for? What do you want to iterate? Try this.

call :cpy pc-name-1
call :cpy pc-name-2
...

:cpy
net use \\%1\{destfolder} {password} /user:{username}
copy {file} \\%1\{destfolder}
goto :EOF

What is the pythonic way to unpack tuples?

Refer https://docs.python.org/2/tutorial/controlflow.html#unpacking-argument-lists

 dt = datetime.datetime(*t[:7])

How do you set the width of an HTML Helper TextBox in ASP.NET MVC?

Set textbox with and maxlength in mvc3.0

@Html.TextBoxFor(model => model.SearchUrl, new { style = "width:650px;",maxlength = 250 })

Amazon Interview Question: Design an OO parking lot

In an Object Oriented parking lot, there will be no need for attendants because the cars will "know how to park".

Finding a usable car on the lot will be difficult; the most common models will either have all their moving parts exposed as public member variables, or they will be "fully encapsulated" cars with no windows or doors.

The parking spaces in our OO parking lot will not match the size and shape of the cars (an "impediance mismatch" between the spaces and the cars)

License tags on our lot will have a dot between each letter and digit. Handicaped parking will only be available for licenses beginning with "_", and licenses beginning with "m_" will be towed.

How do I concatenate const/literal strings in C?

Also malloc and realloc are useful if you don't know ahead of time how many strings are being concatenated.

#include <stdio.h>
#include <string.h>

void example(const char *header, const char **words, size_t num_words)
{
    size_t message_len = strlen(header) + 1; /* + 1 for terminating NULL */
    char *message = (char*) malloc(message_len);
    strncat(message, header, message_len);

    for(int i = 0; i < num_words; ++i)
    {
       message_len += 1 + strlen(words[i]); /* 1 + for separator ';' */
       message = (char*) realloc(message, message_len);
       strncat(strncat(message, ";", message_len), words[i], message_len);
    }

    puts(message);

    free(message);
}

Given a starting and ending indices, how can I copy part of a string in C?

Have you checked strncpy?

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

You must realize that begin and end actually defines a num of bytes to be copied from one place to another.

How to programmatically send a 404 response with Express/Node?

You don't have to simulate it. The second argument to res.send I believe is the status code. Just pass 404 to that argument.

Let me clarify that: Per the documentation on expressjs.org it seems as though any number passed to res.send() will be interpreted as the status code. So technically you could get away with:

res.send(404);

Edit: My bad, I meant res instead of req. It should be called on the response

Edit: As of Express 4, the send(status) method has been deprecated. If you're using Express 4 or later, use: res.sendStatus(404) instead. (Thanks @badcc for the tip in the comments)

First letter capitalization for EditText

use this code to only First letter capitalization for EditText

MainActivity.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/et"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:tag="true">
    </EditText>

</RelativeLayout>

MainActivity.java

EditText et = findViewById(R.id.et);
        et.addTextChangedListener(new TextWatcher() {
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
            }

            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2)
            {
                if (et.getText().toString().length() == 1 && et.getTag().toString().equals("true"))
                {
                    et.setTag("false");
                    et.setText(et.getText().toString().toUpperCase());
                    et.setSelection(et.getText().toString().length());
                }
                if(et.getText().toString().length() == 0)
                {
                    et.setTag("true");
                }
            }

            public void afterTextChanged(Editable editable) {

            }
        });

How to use youtube-dl from a python program?

If youtube-dl is a terminal program, you can use the subprocess module to access the data you want.

Check out this link for more details: Calling an external command in Python

Kubernetes Pod fails with CrashLoopBackOff

Pod is not started due to problem coming after initialization of POD.

Check and use command to get docker container of pod

docker ps -a | grep private-reg

Output will be information of docker container with id.

See docker logs:

docker logs -f <container id>

Properties file with a list as the value for an individual key

There's probably a another way or better. But this is how I do this in Spring Boot.

My property file contains the following lines. "," is the delimiter in each line.

mml.pots=STDEP:DETY=LI3;,STDEP:DETY=LIMA;
mml.isdn.grunntengingar=STDEP:DETY=LIBAE;,STDEP:DETY=LIBAMA;
mml.isdn.stofntengingar=STDEP:DETY=LIPRAE;,STDEP:DETY=LIPRAM;,STDEP:DETY=LIPRAGS;,STDEP:DETY=LIPRVGS;

My server config

@Configuration
public class ServerConfig {

    @Inject
    private Environment env;

    @Bean
    public MMLProperties mmlProperties() {
        MMLProperties properties = new MMLProperties();
        properties.setMmmlPots(env.getProperty("mml.pots"));
        properties.setMmmlPots(env.getProperty("mml.isdn.grunntengingar"));
        properties.setMmmlPots(env.getProperty("mml.isdn.stofntengingar"));
        return properties;
    }
}

MMLProperties class.

public class MMLProperties {
    private String mmlPots;
    private String mmlIsdnGrunntengingar;
    private String mmlIsdnStofntengingar;

    public MMLProperties() {
        super();
    }

    public void setMmmlPots(String mmlPots) {
        this.mmlPots = mmlPots;
    }

    public void setMmlIsdnGrunntengingar(String mmlIsdnGrunntengingar) {
        this.mmlIsdnGrunntengingar = mmlIsdnGrunntengingar;
    }

    public void setMmlIsdnStofntengingar(String mmlIsdnStofntengingar) {
        this.mmlIsdnStofntengingar = mmlIsdnStofntengingar;
    }

    // These three public getXXX functions then take care of spliting the properties into List
    public List<String> getMmmlCommandForPotsAsList() {
        return getPropertieAsList(mmlPots);
    }

    public List<String> getMmlCommandsForIsdnGrunntengingarAsList() {
        return getPropertieAsList(mmlIsdnGrunntengingar);
    }

    public List<String> getMmlCommandsForIsdnStofntengingarAsList() {
        return getPropertieAsList(mmlIsdnStofntengingar);
    }

    private List<String> getPropertieAsList(String propertie) {
        return ((propertie != null) || (propertie.length() > 0))
        ? Arrays.asList(propertie.split("\\s*,\\s*"))
        : Collections.emptyList();
    }
}

Then in my Runner class I Autowire MMLProperties

@Component
public class Runner implements CommandLineRunner {

    @Autowired
    MMLProperties mmlProperties;

    @Override
    public void run(String... arg0) throws Exception {
        // Now I can call my getXXX function to retrieve the properties as List
        for (String command : mmlProperties.getMmmlCommandForPotsAsList()) {
            System.out.println(command);
        }
    }
}

Hope this helps

Construct a manual legend for a complicated plot

You need to map attributes to aesthetics (colours within the aes statement) to produce a legend.

cols <- c("LINE1"="#f04546","LINE2"="#3591d1","BAR"="#62c76b")
ggplot(data=data,aes(x=a)) + 
  geom_bar(stat="identity", aes(y=h, fill = "BAR"),colour="#333333")+ #green
  geom_line(aes(y=b,group=1, colour="LINE1"),size=1.0) +   #red
  geom_point(aes(y=b, colour="LINE1"),size=3) +           #red
  geom_errorbar(aes(ymin=d, ymax=e, colour="LINE1"), width=0.1, size=.8) + 
  geom_line(aes(y=c,group=1,colour="LINE2"),size=1.0) +   #blue 
  geom_point(aes(y=c,colour="LINE2"),size=3) +           #blue
  geom_errorbar(aes(ymin=f, ymax=g,colour="LINE2"), width=0.1, size=.8) + 
  scale_colour_manual(name="Error Bars",values=cols) + scale_fill_manual(name="Bar",values=cols) +
  ylab("Symptom severity") + xlab("PHQ-9 symptoms") +
  ylim(0,1.6) +
  theme_bw() +
  theme(axis.title.x = element_text(size = 15, vjust=-.2)) +
  theme(axis.title.y = element_text(size = 15, vjust=0.3))

enter image description here

I understand where Roland is coming from, but since this is only 3 attributes, and complications arise from superimposing bars and error bars this may be reasonable to leave the data in wide format like it is. It could be slightly reduced in complexity by using geom_pointrange.

To change the background color for the error bars legend in the original, add + theme(legend.key = element_rect(fill = "white",colour = "white")) to the plot specification. To merge different legends, you typically need to have a consistent mapping for all elements, but it is currently producing an artifact of a black background for me. I thought guide = guide_legend(fill = NULL,colour = NULL) would set the background to null for the legend, but it did not. Perhaps worth another question.

ggplot(data=data,aes(x=a)) + 
  geom_bar(stat="identity", aes(y=h,fill = "BAR", colour="BAR"))+ #green
  geom_line(aes(y=b,group=1, colour="LINE1"),size=1.0) +   #red
  geom_point(aes(y=b, colour="LINE1", fill="LINE1"),size=3) +           #red
  geom_errorbar(aes(ymin=d, ymax=e, colour="LINE1"), width=0.1, size=.8) + 
  geom_line(aes(y=c,group=1,colour="LINE2"),size=1.0) +   #blue 
  geom_point(aes(y=c,colour="LINE2", fill="LINE2"),size=3) +           #blue
  geom_errorbar(aes(ymin=f, ymax=g,colour="LINE2"), width=0.1, size=.8) + 
  scale_colour_manual(name="Error Bars",values=cols, guide = guide_legend(fill = NULL,colour = NULL)) + 
  scale_fill_manual(name="Bar",values=cols, guide="none") +
  ylab("Symptom severity") + xlab("PHQ-9 symptoms") +
  ylim(0,1.6) +
  theme_bw() +
  theme(axis.title.x = element_text(size = 15, vjust=-.2)) +
  theme(axis.title.y = element_text(size = 15, vjust=0.3))

enter image description here

To get rid of the black background in the legend, you need to use the override.aes argument to the guide_legend. The purpose of this is to let you specify a particular aspect of the legend which may not be being assigned correctly.

ggplot(data=data,aes(x=a)) + 
  geom_bar(stat="identity", aes(y=h,fill = "BAR", colour="BAR"))+ #green
  geom_line(aes(y=b,group=1, colour="LINE1"),size=1.0) +   #red
  geom_point(aes(y=b, colour="LINE1", fill="LINE1"),size=3) +           #red
  geom_errorbar(aes(ymin=d, ymax=e, colour="LINE1"), width=0.1, size=.8) + 
  geom_line(aes(y=c,group=1,colour="LINE2"),size=1.0) +   #blue 
  geom_point(aes(y=c,colour="LINE2", fill="LINE2"),size=3) +           #blue
  geom_errorbar(aes(ymin=f, ymax=g,colour="LINE2"), width=0.1, size=.8) + 
  scale_colour_manual(name="Error Bars",values=cols, 
                      guide = guide_legend(override.aes=aes(fill=NA))) + 
  scale_fill_manual(name="Bar",values=cols, guide="none") +
  ylab("Symptom severity") + xlab("PHQ-9 symptoms") +
  ylim(0,1.6) +
  theme_bw() +
  theme(axis.title.x = element_text(size = 15, vjust=-.2)) +
  theme(axis.title.y = element_text(size = 15, vjust=0.3))

enter image description here

How to write "Html.BeginForm" in Razor

The following code works fine:

@using (Html.BeginForm("Upload", "Upload", FormMethod.Post, 
                                      new { enctype = "multipart/form-data" }))
{
    @Html.ValidationSummary(true)
    <fieldset>
        Select a file <input type="file" name="file" />
        <input type="submit" value="Upload" />
    </fieldset>
}

and generates as expected:

<form action="/Upload/Upload" enctype="multipart/form-data" method="post">    
    <fieldset>
        Select a file <input type="file" name="file" />
        <input type="submit" value="Upload" />
    </fieldset>
</form>

On the other hand if you are writing this code inside the context of other server side construct such as an if or foreach you should remove the @ before the using. For example:

@if (SomeCondition)
{
    using (Html.BeginForm("Upload", "Upload", FormMethod.Post, 
                                      new { enctype = "multipart/form-data" }))
    {
        @Html.ValidationSummary(true)
        <fieldset>
            Select a file <input type="file" name="file" />
            <input type="submit" value="Upload" />
        </fieldset>
    }
}

As far as your server side code is concerned, here's how to proceed:

[HttpPost]
public ActionResult Upload(HttpPostedFileBase file) 
{
    if (file != null && file.ContentLength > 0) 
    {
        var fileName = Path.GetFileName(file.FileName);
        var path = Path.Combine(Server.MapPath("~/content/pics"), fileName);
        file.SaveAs(path);
    }
    return RedirectToAction("Upload");
}

Import CSV file into SQL Server

Based SQL Server CSV Import

1) The CSV file data may have , (comma) in between (Ex: description), so how can I make import handling these data?

Solution

If you're using , (comma) as a delimiter, then there is no way to differentiate between a comma as a field terminator and a comma in your data. I would use a different FIELDTERMINATOR like ||. Code would look like and this will handle comma and single slash perfectly.

2) If the client create the csv from excel then the data that have comma are enclosed within " ... " (double quotes) [as the below example] so how do the import can handle this?

Solution

If you're using BULK insert then there is no way to handle double quotes, data will be inserted with double quotes into rows. after inserting the data into table you could replace those double quotes with ''.

update table
set columnhavingdoublequotes = replace(columnhavingdoublequotes,'"','')

3) How do we track if some rows have bad data, which import skips? (does import skips rows that are not importable)?

Solution

To handle rows which aren't loaded into table because of invalid data or format, could be handle using ERRORFILE property, specify the error file name, it will write the rows having error to error file. code should look like.

BULK INSERT SchoolsTemp
    FROM 'C:\CSVData\Schools.csv'
    WITH
    (
    FIRSTROW = 2,
    FIELDTERMINATOR = ',',  --CSV field delimiter
    ROWTERMINATOR = '\n',   --Use to shift the control to next row
    ERRORFILE = 'C:\CSVDATA\SchoolsErrorRows.csv',
    TABLOCK
    )

notifyDataSetChanged not working on RecyclerView

Clear your old viewmodel and set the new data to the adapter and call notifyDataSetChanged()

Regex matching in a Bash if statement

There are a couple of important things to know about bash's [[ ]] construction. The first:

Word splitting and pathname expansion are not performed on the words between the [[ and ]]; tilde expansion, parameter and variable expansion, arithmetic expansion, command substitution, process substitution, and quote removal are performed.

The second thing:

An additional binary operator, ‘=~’, is available,... the string to the right of the operator is considered an extended regular expression and matched accordingly... Any part of the pattern may be quoted to force it to be matched as a string.

Consequently, $v on either side of the =~ will be expanded to the value of that variable, but the result will not be word-split or pathname-expanded. In other words, it's perfectly safe to leave variable expansions unquoted on the left-hand side, but you need to know that variable expansions will happen on the right-hand side.

So if you write: [[ $x =~ [$0-9a-zA-Z] ]], the $0 inside the regex on the right will be expanded before the regex is interpreted, which will probably cause the regex to fail to compile (unless the expansion of $0 ends with a digit or punctuation symbol whose ascii value is less than a digit). If you quote the right-hand side like-so [[ $x =~ "[$0-9a-zA-Z]" ]], then the right-hand side will be treated as an ordinary string, not a regex (and $0 will still be expanded). What you really want in this case is [[ $x =~ [\$0-9a-zA-Z] ]]

Similarly, the expression between the [[ and ]] is split into words before the regex is interpreted. So spaces in the regex need to be escaped or quoted. If you wanted to match letters, digits or spaces you could use: [[ $x =~ [0-9a-zA-Z\ ] ]]. Other characters similarly need to be escaped, like #, which would start a comment if not quoted. Of course, you can put the pattern into a variable:

pat="[0-9a-zA-Z ]"
if [[ $x =~ $pat ]]; then ...

For regexes which contain lots of characters which would need to be escaped or quoted to pass through bash's lexer, many people prefer this style. But beware: In this case, you cannot quote the variable expansion:

# This doesn't work:
if [[ $x =~ "$pat" ]]; then ...

Finally, I think what you are trying to do is to verify that the variable only contains valid characters. The easiest way to do this check is to make sure that it does not contain an invalid character. In other words, an expression like this:

valid='0-9a-zA-Z $%&#' # add almost whatever else you want to allow to the list
if [[ ! $x =~ [^$valid] ]]; then ...

! negates the test, turning it into a "does not match" operator, and a [^...] regex character class means "any character other than ...".

The combination of parameter expansion and regex operators can make bash regular expression syntax "almost readable", but there are still some gotchas. (Aren't there always?) One is that you could not put ] into $valid, even if $valid were quoted, except at the very beginning. (That's a Posix regex rule: if you want to include ] in a character class, it needs to go at the beginning. - can go at the beginning or the end, so if you need both ] and -, you need to start with ] and end with -, leading to the regex "I know what I'm doing" emoticon: [][-])

CSS Box Shadow Bottom Only

Do this:

box-shadow: 0 4px 2px -2px gray;

It's actually much simpler, whatever you set the blur to (3rd value), set the spread (4th value) to the negative of it.

How to run Visual Studio post-build events for debug build only

Pre- and Post-Build Events run as a batch script. You can do a conditional statement on $(ConfigurationName).

For instance

if $(ConfigurationName) == Debug xcopy something somewhere

LINQ Group By into a Dictionary Object

I cannot comment on @Michael Blackburn, but I guess you got the downvote because the GroupBy is not necessary in this case.

Use it like:

var lookupOfCustomObjects = listOfCustomObjects.ToLookup(o=>o.PropertyName);
var listWithAllCustomObjectsWithPropertyName = lookupOfCustomObjects[propertyName]

Additionally, I've seen this perform way better than when using GroupBy().ToDictionary().

SQL LEFT JOIN Subquery Alias

I recognize that the answer works and has been accepted but there is a much cleaner way to write that query. Tested on mysql and postgres.

SELECT wpoi.order_id As No_Commande
FROM  wp_woocommerce_order_items AS wpoi
LEFT JOIN wp_postmeta AS wpp ON wpoi.order_id = wpp.post_id 
                            AND wpp.meta_key = '_shipping_first_name'
WHERE  wpoi.order_id =2198

Is there a simple, elegant way to define singletons?

As the accepted answer says, the most idiomatic way is to just use a module.

With that in mind, here's a proof of concept:

def singleton(cls):
    obj = cls()
    # Always return the same object
    cls.__new__ = staticmethod(lambda cls: obj)
    # Disable __init__
    try:
        del cls.__init__
    except AttributeError:
        pass
    return cls

See the Python data model for more details on __new__.

Example:

@singleton
class Duck(object):
    pass

if Duck() is Duck():
    print "It works!"
else:
    print "It doesn't work!"

Notes:

You have to use new-style classes (derive from object) for this.
The singleton is initialized when it is defined, rather than the first time it's used.
This is just a toy example. I've never actually used this in production code, and don't plan to.

How to find index of all occurrences of element in array?

Note: MDN gives a method using a while loop:

var indices = [];
var array = ['a', 'b', 'a', 'c', 'a', 'd'];
var element = 'a';
var idx = array.indexOf(element);
while (idx != -1) {
  indices.push(idx);
  idx = array.indexOf(element, idx + 1);
}

I wouldn't say it's any better than other answers. Just interesting.

RabbitMQ / AMQP: single queue, multiple consumers for same message?

Just read the rabbitmq tutorial. You publish message to exchange, not to queue; it is then routed to appropriate queues. In your case, you should bind separate queue for each consumer. That way, they can consume messages completely independently.

How to list branches that contain a given commit?

From the git-branch manual page:

 git branch --contains <commit>

Only list branches which contain the specified commit (HEAD if not specified). Implies --list.

 git branch -r --contains <commit>

Lists remote tracking branches as well (as mentioned in user3941992's answer below) that is "local branches that have a direct relationship to a remote branch".

As noted by Carl Walsh, this applies only to the default refspec

fetch = +refs/heads/*:refs/remotes/origin/*

If you need to include other ref namespace (pull request, Gerrit, ...), you need to add that new refspec, and fetch again:

git config --add remote.origin.fetch "+refs/pull/*/head:refs/remotes/origin/pr/*"
git fetch
git branch -r --contains <commit>

Using Oracle to_date function for date string with milliseconds

TO_DATE supports conversion to DATE datatype, which doesn't support milliseconds. If you want millisecond support in Oracle, you should look at TIMESTAMP datatype and TO_TIMESTAMP function.

Hope that helps.

Returning unique_ptr from functions

This is in no way specific to std::unique_ptr, but applies to any class that is movable. It's guaranteed by the language rules since you are returning by value. The compiler tries to elide copies, invokes a move constructor if it can't remove copies, calls a copy constructor if it can't move, and fails to compile if it can't copy.

If you had a function that accepts std::unique_ptr as an argument you wouldn't be able to pass p to it. You would have to explicitly invoke move constructor, but in this case you shouldn't use variable p after the call to bar().

void bar(std::unique_ptr<int> p)
{
    // ...
}

int main()
{
    unique_ptr<int> p = foo();
    bar(p); // error, can't implicitly invoke move constructor on lvalue
    bar(std::move(p)); // OK but don't use p afterwards
    return 0;
}

Convert date to datetime in Python

One way to convert from date to datetime that hasn't been mentioned yet:

from datetime import date, datetime
d = date.today()
datetime.strptime(d.strftime('%Y%m%d'), '%Y%m%d')

How to throw a C++ exception

Wanted to ADD to the other answers described here an additional note, in the case of custom exceptions.

In the case where you create your own custom exception, that derives from std::exception, when you catch "all possible" exceptions types, you should always start the catch clauses with the "most derived" exception type that may be caught. See the example (of what NOT to do):

#include <iostream>
#include <string>

using namespace std;

class MyException : public exception
{
public:
    MyException(const string& msg) : m_msg(msg)
    {
        cout << "MyException::MyException - set m_msg to:" << m_msg << endl;
    }

   ~MyException()
   {
        cout << "MyException::~MyException" << endl;
   }

   virtual const char* what() const throw () 
   {
        cout << "MyException - what" << endl;
        return m_msg.c_str();
   }

   const string m_msg;
};

void throwDerivedException()
{
    cout << "throwDerivedException - thrown a derived exception" << endl;
    string execptionMessage("MyException thrown");
    throw (MyException(execptionMessage));
}

void illustrateDerivedExceptionCatch()
{
    cout << "illustrateDerivedExceptionsCatch - start" << endl;
    try 
    {
        throwDerivedException();
    }
    catch (const exception& e)
    {
        cout << "illustrateDerivedExceptionsCatch - caught an std::exception, e.what:" << e.what() << endl;
        // some additional code due to the fact that std::exception was thrown...
    }
    catch(const MyException& e)
    {
        cout << "illustrateDerivedExceptionsCatch - caught an MyException, e.what::" << e.what() << endl;
        // some additional code due to the fact that MyException was thrown...
    }

    cout << "illustrateDerivedExceptionsCatch - end" << endl;
}

int main(int argc, char** argv)
{
    cout << "main - start" << endl;
    illustrateDerivedExceptionCatch();
    cout << "main - end" << endl;
    return 0;
}

NOTE:

0) The proper order should be vice-versa, i.e.- first you catch (const MyException& e) which is followed by catch (const std::exception& e).

1) As you can see, when you run the program as is, the first catch clause will be executed (which is probably what you did NOT wanted in the first place).

2) Even though the type caught in the first catch clause is of type std::exception, the "proper" version of what() will be called - cause it is caught by reference (change at least the caught argument std::exception type to be by value - and you will experience the "object slicing" phenomena in action).

3) In case that the "some code due to the fact that XXX exception was thrown..." does important stuff WITH RESPECT to the exception type, there is misbehavior of your code here.

4) This is also relevant if the caught objects were "normal" object like: class Base{}; and class Derived : public Base {}...

5) g++ 7.3.0 on Ubuntu 18.04.1 produces a warning that indicates the mentioned issue:

In function ‘void illustrateDerivedExceptionCatch()’: item12Linux.cpp:48:2: warning: exception of type ‘MyException’ will be caught catch(const MyException& e) ^~~~~

item12Linux.cpp:43:2: warning: by earlier handler for ‘std::exception’ catch (const exception& e) ^~~~~

Again, I will say, that this answer is only to ADD to the other answers described here (I thought this point is worth mention, yet could not depict it within a comment).

Getting list of tables, and fields in each, in a database

This will return the database name, table name, column name and the datatype of the column specified by a database parameter:

declare @database nvarchar(25)
set @database = ''

SELECT cu.table_catalog,cu.VIEW_SCHEMA, cu.VIEW_NAME, cu.TABLE_NAME,   
cu.COLUMN_NAME,c.DATA_TYPE,c.character_maximum_length
from INFORMATION_SCHEMA.VIEW_COLUMN_USAGE as cu
JOIN INFORMATION_SCHEMA.COLUMNS as c
on cu.TABLE_SCHEMA = c.TABLE_SCHEMA and c.TABLE_CATALOG = 
cu.TABLE_CATALOG
and c.TABLE_NAME = cu.TABLE_NAME
and c.COLUMN_NAME = cu.COLUMN_NAME
where cu.TABLE_CATALOG = @database
order by cu.view_name,c.COLUMN_NAME

how to convert rgb color to int in java

int color = (A & 0xff) << 24 | (R & 0xff) << 16 | (G & 0xff) << 8 | (B & 0xff);

NavigationBar bar, tint, and title text color in iOS 8

Updated with swift 4

override func viewDidLoad() {
    super.viewDidLoad()
        self.navigationController?.navigationBar.tintColor = UIColor.blue
        self.navigationController?.navigationBar.barStyle = UIBarStyle.black
}

What is the best way to clone/deep copy a .NET generic Dictionary<string, T>?

Try this if key/values are ICloneable:

    public static Dictionary<K,V> CloneDictionary<K,V>(Dictionary<K,V> dict) where K : ICloneable where V : ICloneable
    {
        Dictionary<K, V> newDict = null;

        if (dict != null)
        {
            // If the key and value are value types, just use copy constructor.
            if (((typeof(K).IsValueType || typeof(K) == typeof(string)) &&
                 (typeof(V).IsValueType) || typeof(V) == typeof(string)))
            {
                newDict = new Dictionary<K, V>(dict);
            }
            else // prepare to clone key or value or both
            {
                newDict = new Dictionary<K, V>();

                foreach (KeyValuePair<K, V> kvp in dict)
                {
                    K key;
                    if (typeof(K).IsValueType || typeof(K) == typeof(string))
                    {
                        key = kvp.Key;
                    }
                    else
                    {
                        key = (K)kvp.Key.Clone();
                    }
                    V value;
                    if (typeof(V).IsValueType || typeof(V) == typeof(string))
                    {
                        value = kvp.Value;
                    }
                    else
                    {
                        value = (V)kvp.Value.Clone();
                    }

                    newDict[key] = value;
                }
            }
        }

        return newDict;
    }

How do I create an iCal-type .ics file that can be downloaded by other users?

That will work just fine. You can export an entire calendar with File > Export…, or individual events by dragging them to the Finder.

iCalendar (.ics) files are human-readable, so you can always pop it open in a text editor to make sure no private events made it in there. They consist of nested sections with start with BEGIN: and end with END:. You'll mostly find VEVENT sections (each of which represents an event) and VTIMEZONE sections, each of which represents a time zone that's referenced from one or more events.

What does enctype='multipart/form-data' mean?

when should we use it

Quentin's answer is right: use multipart/form-data if the form contains a file upload, and application/x-www-form-urlencoded otherwise, which is the default if you omit enctype.

I'm going to:

add some more HTML5 references
explain why he is right with a form submit example

HTML5 references

There are three possibilities for enctype:

application/x-www-form-urlencoded
multipart/form-data (spec points to RFC7578)
text/plain. This is "not reliably interpretable by computer", so it should never be used in production, and we will not look further into it.

How to generate the examples

Once you see an example of each method, it becomes obvious how they work, and when you should use each one.

You can produce examples using:

nc -l or an ECHO server: HTTP test server accepting GET/POST requests
an user agent like a browser or cURL

Save the form to a minimal .html file:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8"/>
  <title>upload</title>
</head>
<body>
<form action="http://localhost:8000" method="post" enctype="multipart/form-data">
  <p><input type="text" name="text1" value="text default">
  <p><input type="text" name="text2" value="a&#x03C9;b">
  <p><input type="file" name="file1">
  <p><input type="file" name="file2">
  <p><input type="file" name="file3">
  <p><button type="submit">Submit</button>
</form>
</body>
</html>

We set the default text value to aωb, which means a?b because ? is U+03C9, which are the bytes 61 CF 89 62 in UTF-8.

Create files to upload:

echo 'Content of a.txt.' > a.txt

echo '<!DOCTYPE html><title>Content of a.html.</title>' > a.html

# Binary file containing 4 bytes: 'a', 1, 2 and 'b'.
printf 'a\xCF\x89b' > binary

Run our little echo server:

while true; do printf '' | nc -l 8000 localhost; done

Open the HTML on your browser, select the files and click on submit and check the terminal.

nc prints the request received.

Tested on: Ubuntu 14.04.3, nc BSD 1.105, Firefox 40.

multipart/form-data

Firefox sent:

POST / HTTP/1.1
[[ Less interesting headers ... ]]
Content-Type: multipart/form-data; boundary=---------------------------735323031399963166993862150
Content-Length: 834

-----------------------------735323031399963166993862150
Content-Disposition: form-data; name="text1"

text default
-----------------------------735323031399963166993862150
Content-Disposition: form-data; name="text2"

a?b
-----------------------------735323031399963166993862150
Content-Disposition: form-data; name="file1"; filename="a.txt"
Content-Type: text/plain

Content of a.txt.

-----------------------------735323031399963166993862150
Content-Disposition: form-data; name="file2"; filename="a.html"
Content-Type: text/html

<!DOCTYPE html><title>Content of a.html.</title>

-----------------------------735323031399963166993862150
Content-Disposition: form-data; name="file3"; filename="binary"
Content-Type: application/octet-stream

a?b
-----------------------------735323031399963166993862150--

For the binary file and text field, the bytes 61 CF 89 62 (a?b in UTF-8) are sent literally. You could verify that with nc -l localhost 8000 | hd, which says that the bytes:

61 CF 89 62

were sent (61 == 'a' and 62 == 'b').

Therefore it is clear that:

Content-Type: multipart/form-data; boundary=---------------------------735323031399963166993862150 sets the content type to multipart/form-data and says that the fields are separated by the given boundary string.

But note that the:
```
boundary=---------------------------735323031399963166993862150
```
has two less dadhes -- than the actual barrier
```
-----------------------------735323031399963166993862150
```
This is because the standard requires the boundary to start with two dashes --. The other dashes appear to be just how Firefox chose to implement the arbitrary boundary. RFC 7578 clearly mentions that those two leading dashes -- are required:

4.1. "Boundary" Parameter of multipart/form-data

As with other multipart types, the parts are delimited with a boundary delimiter, constructed using CRLF, "--", and the value of the "boundary" parameter.
every field gets some sub headers before its data: Content-Disposition: form-data;, the field name, the filename, followed by the data.

The server reads the data until the next boundary string. The browser must choose a boundary that will not appear in any of the fields, so this is why the boundary may vary between requests.

Because we have the unique boundary, no encoding of the data is necessary: binary data is sent as is.

TODO: what is the optimal boundary size (log(N) I bet), and name / running time of the algorithm that finds it? Asked at: https://cs.stackexchange.com/questions/39687/find-the-shortest-sequence-that-is-not-a-sub-sequence-of-a-set-of-sequences
Content-Type is automatically determined by the browser.

How it is determined exactly was asked at: How is mime type of an uploaded file determined by browser?

application/x-www-form-urlencoded

Now change the enctype to application/x-www-form-urlencoded, reload the browser, and resubmit.

Firefox sent:

POST / HTTP/1.1
[[ Less interesting headers ... ]]
Content-Type: application/x-www-form-urlencoded
Content-Length: 51

text1=text+default&text2=a%CF%89b&file1=a.txt&file2=a.html&file3=binary

Clearly the file data was not sent, only the basenames. So this cannot be used for files.

As for the text field, we see that usual printable characters like a and b were sent in one byte, while non-printable ones like 0xCF and 0x89 took up 3 bytes each: %CF%89!

Comparison

File uploads often contain lots of non-printable characters (e.g. images), while text forms almost never do.

From the examples we have seen that:

multipart/form-data: adds a few bytes of boundary overhead to the message, and must spend some time calculating it, but sends each byte in one byte.
application/x-www-form-urlencoded: has a single byte boundary per field (&), but adds a linear overhead factor of 3x for every non-printable character.

Therefore, even if we could send files with application/x-www-form-urlencoded, we wouldn't want to, because it is so inefficient.

But for printable characters found in text fields, it does not matter and generates less overhead, so we just use it.

C++ How do I convert a std::chrono::time_point to long and back

I would also note there are two ways to get the number of ms in the time point. I'm not sure which one is better, I've benchmarked them and they both have the same performance, so I guess it's a matter of preference. Perhaps Howard could chime in:

auto now = system_clock::now();

//Cast the time point to ms, then get its duration, then get the duration's count.
auto ms = time_point_cast<milliseconds>(now).time_since_epoch().count();

//Get the time point's duration, then cast to ms, then get its count.
auto ms = duration_cast<milliseconds>(tpBid.time_since_epoch()).count();

The first one reads more clearly in my mind going from left to right.

CSS :: child set to change color on parent hover, but changes also when hovered itself

If you don't care about supporting old browsers, you can use :not() to exclude that element:

.parent:hover span:not(:hover) {
    border: 10px solid red;
}

Demo: http://jsfiddle.net/vz9A9/1/

If you do want to support them, the I guess you'll have to either use JavaScript or override the CSS properties again:

.parent span:hover {
    border: 10px solid green;
}

Running Internet Explorer 6, Internet Explorer 7, and Internet Explorer 8 on the same machine

I wouldn't do it. Use virtual PCs instead. It might take a little setup, but you'll thank yourself in the long run. In my experience, you can't really get them cleanly installed side by side and unless they are standalone installs you can't really verify that it is 100% true-to-browser rendering.

Update: Looks like one of the better ways to accomplish this (if running Windows 7) is using Windows XP mode to set up multiple virtual machines: Testing Multiple Versions of IE on one PC at the IEBlog.

Update 2: (11/2014) There are new solutions since this was last updated. Microsoft now provides VMs for any environment to test multiple versions of IE: Modern.IE

get next sequence value from database using hibernate

I found the solution:

public class DefaultPostgresKeyServer
{
    private Session session;
    private Iterator<BigInteger> iter;
    private long batchSize;

    public DefaultPostgresKeyServer (Session sess, long batchFetchSize)
    {
        this.session=sess;
        batchSize = batchFetchSize;
        iter = Collections.<BigInteger>emptyList().iterator();
    }

        @SuppressWarnings("unchecked")
        public Long getNextKey()
        {
            if ( ! iter.hasNext() )
            {
                Query query = session.createSQLQuery( "SELECT nextval( 'mySchema.mySequence' ) FROM generate_series( 1, " + batchSize + " )" );

                iter = (Iterator<BigInteger>) query.list().iterator();
            }
            return iter.next().longValue() ;
        }

}

How to set the height and the width of a textfield in Java?

     f.setLayout(null);

add the above lines ( f is a JFrame or a Container where you have added the JTestField )

But try to learn 'LayoutManager' in java ; refer to other answers for the links of the tutorials .Or try This http://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html

.prop('checked',false) or .removeAttr('checked')?

I recommend to use both, prop and attr because I had problems with Chrome and I solved it using both functions.

if ($(':checkbox').is(':checked')){
    $(':checkbox').prop('checked', true).attr('checked', 'checked');
}
else {
    $(':checkbox').prop('checked', false).removeAttr('checked');
}

Changing button color programmatically

Here is an example using HTML:

<input type="button" value="click me" onclick="this.style.color='#000000';
this.style.backgroundColor = '#ffffff'" />

And here is an example using JavaScript:

document.getElementById("button").bgcolor="#Insert Color Here";

How to use enums in C++

You are looking for strongly typed enumerations, a feature available in the C++11 standard. It turns enumerations into classes with scope values.

Using your own code example, it is:

  enum class Days {Saturday, Sunday, Tuesday,Wednesday, Thursday, Friday};
  Days day = Days::Saturday;

  if (day == Days::Saturday)  {
    cout << " Today is Saturday !" << endl;
  }
  //int day2 = Days::Sunday; // Error! invalid

Using :: as accessors to enumerations will fail if targeting a C++ standard prior C++11. But some old compilers doesn't supported it, as well some IDEs just override this option, and set a old C++ std.

If you are using GCC, enable C+11 with -std=c++11 or -std=gnu11 .

Be happy!

Getting the difference between two Dates (months/days/hours/minutes/seconds) in Swift

Swift 5.1 • iOS 13

You can use RelativeDateFormatter that has been introduced by Apple in iOS 13.

let exampleDate = Date().addingTimeInterval(-15000)

let formatter = RelativeDateTimeFormatter()
formatter.unitsStyle = .full
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())

print(relativeDate) // 4 hours ago

See How to show a relative date and time using RelativeDateTimeFormatter.

break/exit script

You can use the pskill function in the R "tools" package to interrupt the current process and return to the console. Concretely, I have the following function defined in a startup file that I source at the beginning of each script. You can also copy it directly at the start of your code, however. Then insert halt() at any point in your code to stop script execution on the fly. This function works well on GNU/Linux and judging from the R documentation, it should also work on Windows (but I didn't check).

# halt: interrupts the current R process; a short iddle time prevents R from
# outputting further results before the SIGINT (= Ctrl-C) signal is received 
halt <- function(hint = "Process stopped.\n") {
    writeLines(hint)
    require(tools, quietly = TRUE)
    processId <- Sys.getpid() 
    pskill(processId, SIGINT)
    iddleTime <- 1.00
    Sys.sleep(iddleTime)
}

Case-insensitive search

I do this often and use a simple 5 line prototype that accepts varargs. It is fast and works everywhere.

myString.containsIgnoreCase('red','orange','yellow')

_x000D_

/**_x000D_
 * @param {...string} var_strings Strings to search for_x000D_
 * @return {boolean} true if ANY of the arguments is contained in the string_x000D_
 */_x000D_
String.prototype.containsIgnoreCase = function(var_strings) {_x000D_
  const thisLowerCase = this.toLowerCase()_x000D_
  for (let i = 0; i < arguments.length; i++) {_x000D_
    let needle = arguments[i]_x000D_
    if (thisLowerCase.indexOf(needle.toLowerCase()) >= 0) {_x000D_
      return true_x000D_
    }_x000D_
  }_x000D_
  return false_x000D_
}_x000D_
_x000D_
/**_x000D_
 * @param {...string} var_strings Strings to search for_x000D_
 * @return {boolean} true if ALL of the arguments are contained in the string_x000D_
 */_x000D_
String.prototype.containsAllIgnoreCase = function(var_strings) {_x000D_
  const thisLowerCase = this.toLowerCase()_x000D_
  for (let i = 0; i < arguments.length; i++) {_x000D_
    let needle = arguments[i]_x000D_
    if (thisLowerCase.indexOf(needle.toLowerCase()) === -1) {_x000D_
      return false_x000D_
    }_x000D_
  }_x000D_
  return true_x000D_
}_x000D_
_x000D_
// Unit test_x000D_
_x000D_
let content = `_x000D_
FIRST SECOND_x000D_
"At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat."_x000D_
"At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat."_x000D_
"At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat."_x000D_
"At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat."_x000D_
"At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat."_x000D_
"At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat."_x000D_
FOO BAR_x000D_
`_x000D_
_x000D_
let data = [_x000D_
  'foo',_x000D_
  'Foo',_x000D_
  'foobar',_x000D_
  'barfoo',_x000D_
  'first',_x000D_
  'second'_x000D_
]_x000D_
_x000D_
let result_x000D_
data.forEach(item => {_x000D_
  console.log('Searching for', item)_x000D_
  result = content.containsIgnoreCase(item)_x000D_
  console.log(result ? 'Found' : 'Not Found')_x000D_
})_x000D_
_x000D_
console.log('Searching for', 'x, y, foo')_x000D_
result = content.containsIgnoreCase('x', 'y', 'foo');_x000D_
console.log(result ? 'Found' : 'Not Found')_x000D_
_x000D_
console.log('Searching for all', 'foo, bar, foobar')_x000D_
result = content.containsAllIgnoreCase('foo', 'bar', 'foobar');_x000D_
console.log(result ? 'Found' : 'Not Found')_x000D_
_x000D_
console.log('Searching for all', 'foo, bar')_x000D_
result = content.containsAllIgnoreCase('foo', 'bar');_x000D_
console.log(result ? 'Found' : 'Not Found')

_x000D_

Angular 2 beta.17: Property 'map' does not exist on type 'Observable<Response>'

property 'map' does not exist on type 'observable response ' angular 6

Solution: Update Angular CLI And Core Version

ng update @angular/cli           //Update Angular CLi 
ng update @angular/core          //Update Angular Core 
npm install --save rxjs-compat   //For Map Call For Post Method

Comparing a variable with a string python not working when redirecting from bash script

When you read() the file, you may get a newline character '\n' in your string. Try either

if UserInput.strip() == 'List contents':

if 'List contents' in UserInput:

Also note that your second file open could also use with:

with open('/Users/.../USER_INPUT.txt', 'w+') as UserInputFile:     if UserInput.strip() == 'List contents': # or if s in f:         UserInputFile.write("ls")     else:         print "Didn't work"

How can I match a string with a regex in Bash?

Since you are using bash, you don't need to create a child process for doing this. Here is one solution which performs it entirely within bash:

[[ $TEST =~ ^(.*):\ +(.*)$ ]] && TEST=${BASH_REMATCH[1]}:${BASH_REMATCH[2]}

Explanation: The groups before and after the sequence "colon and one or more spaces" are stored by the pattern match operator in the BASH_REMATCH array.

Which websocket library to use with Node.js?

npm ws was the answer for me. I found it less intrusive and more straight forward. With it was also trivial to mix websockets with rest services. Shared simple code on this post.

var WebSocketServer = require("ws").Server;
var http = require("http");
var express = require("express");
var port = process.env.PORT || 5000;

var app = express();
    app.use(express.static(__dirname+ "/../"));
    app.get('/someGetRequest', function(req, res, next) {
       console.log('receiving get request');
    });
    app.post('/somePostRequest', function(req, res, next) {
       console.log('receiving post request');
    });
    app.listen(80); //port 80 need to run as root

    console.log("app listening on %d ", 80);

var server = http.createServer(app);
    server.listen(port);

console.log("http server listening on %d", port);

var userId;
var wss = new WebSocketServer({server: server});
    wss.on("connection", function (ws) {

    console.info("websocket connection open");

    var timestamp = new Date().getTime();
    userId = timestamp;

    ws.send(JSON.stringify({msgType:"onOpenConnection", msg:{connectionId:timestamp}}));


    ws.on("message", function (data, flags) {
        console.log("websocket received a message");
        var clientMsg = data;

        ws.send(JSON.stringify({msg:{connectionId:userId}}));


    });

    ws.on("close", function () {
        console.log("websocket connection close");
    });
});
console.log("websocket server created");

Obtain smallest value from array in Javascript?

_x000D_

function smallest(){_x000D_
  if(arguments[0] instanceof Array)_x000D_
    arguments = arguments[0];_x000D_
_x000D_
  return Math.min.apply( Math, arguments );_x000D_
}_x000D_
function largest(){_x000D_
  if(arguments[0] instanceof Array)_x000D_
    arguments = arguments[0];_x000D_
_x000D_
  return Math.max.apply( Math, arguments );_x000D_
}_x000D_
var min = smallest(10, 11, 12, 13);_x000D_
var max = largest([10, 11, 12, 13]);_x000D_
_x000D_
console.log("Smallest: "+ min +", Largest: "+ max);

_x000D_

How can I use inverse or negative wildcards when pattern matching in a unix/linux shell?

In Bash you can do it by enabling the extglob option, like this (replace ls with cp and add the target directory, of course)

~/foobar> shopt extglob
extglob        off
~/foobar> ls
abar  afoo  bbar  bfoo
~/foobar> ls !(b*)
-bash: !: event not found
~/foobar> shopt -s extglob  # Enables extglob
~/foobar> ls !(b*)
abar  afoo
~/foobar> ls !(a*)
bbar  bfoo
~/foobar> ls !(*foo)
abar  bbar

You can later disable extglob with

shopt -u extglob

Rank function in MySQL

select id,first_name,gender,age,
rank() over(partition by gender order by age) rank_g
from person

CREATE TABLE person (id int, first_name varchar(20), age int, gender char(1));

INSERT INTO person VALUES (1, 'Bob', 25, 'M');
INSERT INTO person VALUES (2, 'Jane', 20, 'F');
INSERT INTO person VALUES (3, 'Jack', 30, 'M');
INSERT INTO person VALUES (4, 'Bill', 32, 'M');
INSERT INTO person VALUES (5, 'Nick', 22, 'M');
INSERT INTO person VALUES (6, 'Kathy', 18, 'F');
INSERT INTO person VALUES (7, 'Steve', 36, 'M');
INSERT INTO person VALUES (8, 'Anne', 25, 'F');
INSERT INTO person VALUES (9,'AKSH',32,'M');

Inner join vs Where

Using JOIN makes the code easier to read, since it's self-explanatory.

There's no difference in speed(I have just tested it) and the execution plan is the same.

Using Javamail to connect to Gmail smtp server ignores specified port and tries to use 25

In Java you would do something similar to:

Transport transport = session.getTransport("smtps");
transport.connect (smtp_host, smtp_port, smtp_username, smtp_password);
transport.sendMessage(msg, msg.getAllRecipients());
transport.close();

Note 'smtpS' protocol. Also socketFactory properties is no longer necessary in modern JVMs but you might need to set 'mail.smtps.auth' and 'mail.smtps.starttls.enable' to 'true' for Gmail. 'mail.smtps.debug' could be helpful too.

Combining COUNT IF AND VLOOK UP EXCEL

Try this:

=IF(NOT(ISERROR(MATCH(A3,worksheet2!A:A,0))),COUNTIF(worksheet2!A:A,A3),"No Match Found")

Read large files in Java

You can consider using memory-mapped files, via FileChannels .

Generally a lot faster for large files. There are performance trade-offs that could make it slower, so YMMV.

How to search for a file in the CentOS command line

Try this command:

find / -name file.look

HTTP could not register URL http://+:8000/HelloWCF/. Your process does not have access rights to this namespace

Close iis express and all the browsers (if the url was opened in any of the browser). Also open the visual studio IDE in admin mode. This has resolved my issue.

Deep copy an array in Angular 2 + TypeScript

Alternatively, you can use the GitHub project ts-deepcopy, which is also available on npm, to clone your object, or just include the code snippet below.

/**
 * Deep copy function for TypeScript.
 * @param T Generic type of target/copied value.
 * @param target Target value to be copied.
 * @see Source project, ts-deepcopy https://github.com/ykdr2017/ts-deepcopy
 * @see Code pen https://codepen.io/erikvullings/pen/ejyBYg
 */
export const deepCopy = <T>(target: T): T => {
  if (target === null) {
    return target;
  }
  if (target instanceof Date) {
    return new Date(target.getTime()) as any;
  }
  if (target instanceof Array) {
    const cp = [] as any[];
    (target as any[]).forEach((v) => { cp.push(v); });
    return cp.map((n: any) => deepCopy<any>(n)) as any;
  }
  if (typeof target === 'object' && target !== {}) {
    const cp = { ...(target as { [key: string]: any }) } as { [key: string]: any };
    Object.keys(cp).forEach(k => {
      cp[k] = deepCopy<any>(cp[k]);
    });
    return cp as T;
  }
  return target;
};

Cannot open backup device. Operating System error 5

Yeah I just scored this one.

Look in Windows Services. Start > Administration > Services

Find the Service in the list called: SQL Server (MSSQLSERVER) look for the "Log On As" column (need to add it if it doesn't exist in the list).

This is the account you need to give permissions to the directory, right click in explorer > properties > Shares (And Security)

NOTE: Remember to give permissions to the actual directory AND to the share if you are going across the network.

Apply and wait for the permissions to propogate, try the backup again.

NOTE 2: if you are backing up across the network and your SQL is running as "Local Service" then you are in trouble ... you can try assigning permissions or it may be easier to backup locally and xcopy across outside of SQL Server (an hour later).

NOTE 3: If you're running as network service then SOMETIMES the remote machine will not recognize the network serivce on your SQL Server. If this is the case you need to add permissions for the actual computer itself eg. MyServer$.

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

All created by user files saved in C:\xampp\htdocs directory by default, so no need to type the default path in a browser window, just type http://localhost/yourfilename.php or http://localhost/yourfoldername/yourfilename.php this will show you the content of your new page.

Node.js + Nginx - What now?

You can run nodejs using pm2 if you want to manage each microservice means and run it. Node will be running in a port right just configure that port in nginx(/etc/nginx/sites-enabled/domain.com)

server{
    listen 80;
    server_name domain.com www.domain.com;

  location / {
     return 403;
  }
    location /url {
        proxy_pass http://localhost:51967/info;
    }
}

Check whether localhost is running or not by using ping.

And

Create one single Node.js server which handles all Node.js requests. This reads the requested files and evals their contents. So the files are interpreted on each request, but the server logic is much simpler.

This is best and as you said easier too

Receiver not registered exception error?

For anybody who will come upon this problem and they tried all that was suggested and nothing still works, this is how I sorted my problem, instead of doing LocalBroadcastManager.getInstance(this).registerReceiver(...) I first created a local variable of type LocalBroadcastManager,

private LocalBroadcastManager lbman;

And used this variable to carry out the registering and unregistering on the broadcastreceiver, that is

lbman.registerReceiver(bReceiver);

and

lbman.unregisterReceiver(bReceiver);

Using OR & AND in COUNTIFS

In a more general case:

N( A union B) = N(A) + N(B) - N(A intersect B) 
= COUNTIFS(A1:A196,"Yes",J1:J196,"Agree")+COUNTIFS(A1:A196,"No",J1:J196,"Agree")-A1:A196,"Yes",A1:A196,"No")

mysqldump data only

Best to dump to a compressed file

mysqldump --no-create-info -u username -hhostname -p dbname | gzip > /backupsql.gz

and to restore using pv apt-get install pv to monitor progress

pv backupsql.gz | gunzip | mysql -uusername -hhostip -p dbname

jQuery Combobox/select autocomplete?

jQuery 1.8.1 has an example of this under autocomplete. It's very easy to implement.

How to SSH into Docker?

Create docker image with openssh-server preinstalled:

Dockerfile

FROM ubuntu:16.04

RUN apt-get update && apt-get install -y openssh-server
RUN mkdir /var/run/sshd
RUN echo 'root:screencast' | chpasswd
RUN sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config

# SSH login fix. Otherwise user is kicked off after login
RUN sed 's@session\s*required\s*pam_loginuid.so@session optional pam_loginuid.so@g' -i /etc/pam.d/sshd

ENV NOTVISIBLE "in users profile"
RUN echo "export VISIBLE=now" >> /etc/profile

EXPOSE 22
CMD ["/usr/sbin/sshd", "-D"]

Build the image using:

$ docker build -t eg_sshd .

Run a test_sshd container:

$ docker run -d -P --name test_sshd eg_sshd
$ docker port test_sshd 22

0.0.0.0:49154

Ssh to your container:

$ ssh [email protected] -p 49154
# The password is ``screencast``.
root@f38c87f2a42d:/#

Source: https://docs.docker.com/engine/examples/running_ssh_service/#build-an-eg_sshd-image

How to convert string to float?

Use atof() or strtof()* instead:

printf("float value : %4.8f\n" ,atof(s)); 
printf("float value : %4.8f\n" ,strtof(s, NULL));

http://www.cplusplus.com/reference/clibrary/cstdlib/atof/
http://www.cplusplus.com/reference/cstdlib/strtof/

atoll() is meant for integers.
atof()/strtof() is for floats.

The reason why you only get 4.00 with atoll() is because it stops parsing when it finds the first non-digit.

*Note that strtof() requires C99 or C++11.

Convert negative data into positive data in SQL Server

You are thinking in the function ABS, that gives you the absolute value of numeric data.

SELECT ABS(a) AS AbsoluteA, ABS(b) AS AbsoluteB
FROM YourTable

Benefits of EBS vs. instance-store (and vice-versa)

Eric pretty much nailed it. We (Bitnami) are a popular provider of free AMIs for popular applications and development frameworks (PHP, Joomla, Drupal, you get the idea). I can tell you that EBS-backed AMIs are significantly more popular than S3-backed. In general I think s3-backed instances are used for distributed, time-limited jobs (for example, large scale processing of data) where if one machine fails, another one is simply spinned up. EBS-backed AMIS tend to be used for 'traditional' server tasks, such as web or database servers that keep state locally and thus require the data to be available in the case of crashing.

One aspect I did not see mentioned is the fact that you can take snapshots of an EBS-backed instance while running, effectively allowing you to have very cost-effective backups of your infrastructure (the snapshots are block-based and incremental)

How to change visibility of layout programmatically

this is a programatical approach:

 view.setVisibility(View.GONE); //For GONE
 view.setVisibility(View.INVISIBLE); //For INVISIBLE
 view.setVisibility(View.VISIBLE); //For VISIBLE

How to use Python to login to a webpage and retrieve cookies for later usage?

Here's a version using the excellent requests library:

from requests import session

payload = {
    'action': 'login',
    'username': USERNAME,
    'password': PASSWORD
}

with session() as c:
    c.post('http://example.com/login.php', data=payload)
    response = c.get('http://example.com/protected_page.php')
    print(response.headers)
    print(response.text)

Javascript Uncaught TypeError: Cannot read property '0' of undefined

There is no error when I use your code,

but I am calling the hasLetter method like this:

hasLetter("a",words);

How to find all occurrences of a substring?

Here's a (very inefficient) way to get all (i.e. even overlapping) matches:

>>> string = "test test test test"
>>> [i for i in range(len(string)) if string.startswith('test', i)]
[0, 5, 10, 15]

How to detect page zoom level in all modern browsers?

I have a solution for this as of Jan 2016. Tested working in Chrome, Firefox and MS Edge browsers.

The principle is as follows. Collect 2 MouseEvent points that are far apart. Each mouse event comes with screen and document coordinates. Measure the distance between the 2 points in both coordinate systems. Although there are variable fixed offsets between the coordinate systems due to the browser furniture, the distance between the points should be identical if the page is not zoomed. The reason for specifying "far apart" (I put this as 12 pixels) is so that small zoom changes (e.g. 90% or 110%) are detectable.

Reference: https://developer.mozilla.org/en/docs/Web/Events/mousemove

Steps:

Add a mouse move listener

window.addEventListener("mousemove", function(event) {
    // handle event
});

Capture 4 measurements from mouse events:

event.clientX, event.clientY, event.screenX, event.screenY

Measure the distance d_c between the 2 points in the client system
Measure the distance d_s between the 2 points in the screen system
If d_c != d_s then zoom is applied. The difference between the two tells you the amount of zoom.

N.B. Only do the distance calculations rarely, e.g. when you can sample a new mouse event that's far from the previous one.

Limitations: Assumes user will move the mouse at least a little, and zoom is unknowable until this time.

Is it possible to create a remote repo on GitHub from the CLI without opening browser?

CLI commands for github API v3 (replace all CAPS keywords):

curl -u 'USER' https://api.github.com/user/repos -d '{"name":"REPO"}'
# Remember replace USER with your username and REPO with your repository/application name!
git remote add origin [email protected]:USER/REPO.git
git push origin master

SQL "between" not inclusive

cast(created_at as date)

That will work only in 2008 and newer versions of SQL Server

If you are using older version then use

convert(varchar, created_at, 101)

Add days Oracle SQL

You can use the plus operator to add days to a date.

order_date + 20

How to submit an HTML form without redirection

See jQuery's post function.

I would create a button, and set an onClickListener ($('#button').on('click', function(){});), and send the data in the function.

Also, see the preventDefault function, of jQuery!

css transition opacity fade background

Wrap your image with a span element with a black background.

_x000D_

.img-wrapper {
  display: inline-block;
  background: #000;
}

.item-fade {
  vertical-align: top;
  transition: opacity 0.3s;
  -webkit-transition: opacity 0.3s;
  opacity: 1;
}

.item-fade:hover {
  opacity: 0.2;
}

_x000D_

<span class="img-wrapper">
   <img class="item-fade" src="http://placehold.it/100x100/cf5" />
</span>

_x000D_

how to open a jar file in Eclipse

Firstly, it's necessary to know what is a jar file.

From Oracle,

JAR (Java Archive) is a platform-independent file format that aggregates many files into one. Multiple Java applets and their requisite components (.class files, images and sounds) can be bundled in a JAR file and subsequently downloaded to a browser in a single HTTP transaction, greatly improving the download speed. The JAR format also supports compression, which reduces the file size, further improving the download time.

As you can see,

It has nothing to do with a Eclipse project. An Eclipse project can be a Java project, C++ project and so on. It's just a self contain project that can be recognized and operated as an unit by Eclipse.
The .class files are generally the main part of a jar file. It's impossible to view the source code(.java file) unless you decompile the executable file(.class file) by some tools. Take Eclipse for example, you can choose the plugin Eclipse Class Decompiler as the tool.

Autowiring fails: Not an managed Type

I got an very helpful advice from Oliver Gierke:

The last exception you get actually indicates a problem with your JPA setup. "Not a managed bean" means not a type the JPA provider is aware of. If you're setting up a Spring based JPA application I'd recommend to configure the "packagesToScan" property on the LocalContainerEntityManagerFactory you have configured to the package that contains your JPA entities. Alternatively you can list all your entity classes in persistence.xml, but that's usually more cumbersome.

The former error you got (NoClassDefFound) indicates the class mentioned is not available on the projects classpath. So you might wanna check the inter module dependencies you have. As the two relevant classes seem to be located in the same module it might also just be an issue with an incomplete deployment to Tomcat (WTP is kind of bitchy sometimes). I'd definitely recommend to run a test for verification (as you already did). As this seems to lead you to a different exception, I guess it's really some Eclipse glitch

Thanks!

Removing the title text of an iOS UIBarButtonItem

[[UIBarButtonItem appearance] setBackButtonBackgroundImage:backButtonImage forState:UIControlStateNormal barMetrics:UIBarMetricsDefaultPrompt];
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(10.0, NSIntegerMin) forBarMetrics:UIBarMetricsDefault];
[[UIBarButtonItem appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor whiteColor],
                                                               NSFontAttributeName:[UIFont systemFontOfSize:1]}
                                                    forState:UIControlStateNormal];

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

FooA, FooB and FooC implements IFoo

Services Provider:

services.AddTransient<FooA>(); // Note that there is no interface
services.AddTransient<FooB>();
services.AddTransient<FooC>();

services.AddSingleton<Func<Type, IFoo>>(x => type =>
{
    return (IFoo)x.GetService(type);
});

Destination:

public class Test
{
    private readonly IFoo foo;

    public Test(Func<Type, IFoo> fooFactory)
    {
        foo = fooFactory(typeof(FooA));
    }

    ....

}

If you want to change the FooA to FooAMock for test purposes:

services.AddTransient<FooAMock>();

services.AddSingleton<Func<Type, IFoo>>(x => type =>
{
    if(type.Equals(typeof(FooA))
        return (IFoo)x.GetService(typeof(FooAMock));
    return null;
});

IntelliJ IDEA "The selected directory is not a valid home for JDK"

For Windows, apparently the JDK has to be under C:\Program Files.

This does not work:

C:\dev\Java\jdk1.8.0_191

This works:

C:\Program Files\Java\jdk1.8.0_191

(I'm using IntelliJ IDEA Ultimate 2018.2.4.)

How to insert multiple rows from array using CodeIgniter framework?

Multiple insert/ batch insert is now supported by CodeIgniter.

$data = array(
   array(
      'title' => 'My title' ,
      'name' => 'My Name' ,
      'date' => 'My date'
   ),
   array(
      'title' => 'Another title' ,
      'name' => 'Another Name' ,
      'date' => 'Another date'
   )
);

$this->db->insert_batch('mytable', $data);

// Produces: INSERT INTO mytable (title, name, date) VALUES ('My title', 'My name', 'My date'), ('Another title', 'Another name', 'Another date')

Angular 4 img src is not found

You must use this code in angular to add the image path. if your images are under assets folder then.

<img src="../assets/images/logo.png" id="banner-logo" alt="Landing Page"/>

if not under the assets folder then you can use this code.

<img src="../images/logo.png" id="banner-logo" alt="Landing Page"/>

Remove empty strings from a list of strings

match using a regular expression and a filter

lstr = ['hello', '', ' ', 'world', ' ']
r=re.compile('^[A-Za-z0-9]+')
results=list(filter(r.match,lstr))
print(results)

Facebook Graph API : get larger pictures in one request

I researched Graph API Explorer extensively and finally found full_picture

https://graph.facebook.com/v2.2/$id/posts?fields=picture,full_picture

P.S. I noticed that full_picture won't always provide full size image I want. 'attachments' does

https://graph.facebook.com/v2.2/$id/posts?fields=picture,full_picture,attachments

Reverse Contents in Array

I would use the reverse() function from the <algorithm> library.

Run it online: repl.it/@abranhe/Reverse-Array

#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
  int arr [10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

  reverse(begin(arr), end(arr));

  for(auto item:arr)
  {
    cout << item << " ";
  }
}

Output:

10 9 8 7 6 5 4 3 2 1

Hope you like this approach.

entity object cannot be referenced by multiple instances of IEntityChangeTracker. while adding related objects to entity in Entity Framework 4.1

Error source:

ApplicationUser user = await UserManager.FindByIdAsync(User.Identity.Name);
ApplicationDbContext db = new ApplicationDbContent();
db.Users.Uploads.Add(new MyUpload{FileName="newfile.png"});
await db.SavechangesAsync();/ZZZZZZZ

Hope someone saves some precious time

How do I detect the Python version at runtime?

Sure, take a look at sys.version and sys.version_info.

For example, to check that you are running Python 3.x, use

import sys
if sys.version_info[0] < 3:
    raise Exception("Must be using Python 3")

Here, sys.version_info[0] is the major version number. sys.version_info[1] would give you the minor version number.

In Python 2.7 and later, the components of sys.version_info can also be accessed by name, so the major version number is sys.version_info.major.

python JSON only get keys in first level

A good way to check whether a python object is an instance of a type is to use isinstance() which is Python's 'built-in' function. For Python 3.6:

dct = {
       "1": "a", 
       "3": "b", 
       "8": {
            "12": "c", 
            "25": "d"
           }
      }

for key in dct.keys():
    if isinstance(dct[key], dict)== False:
       print(key, dct[key])
#shows:
# 1 a
# 3 b

Have log4net use application config file for configuration data

Add a line to your app.config in the configSections element

<configSections>
 <section name="log4net" 
   type="log4net.Config.Log4NetConfigurationSectionHandler, log4net, Version=1.2.10.0, 
         Culture=neutral, PublicKeyToken=1b44e1d426115821" />
</configSections>

Then later add the log4Net section, but delegate to the actual log4Net config file elsewhere...

<log4net configSource="Config\Log4Net.config" />

In your application code, when you create the log, write

private static ILog GetLog(string logName)
{
    ILog log = LogManager.GetLogger(logName);
    return log;
}

How to use php serialize() and unserialize()

preg_match_all('/\".*?\"/i', $string, $matches);
foreach ($matches[0] as $i => $match) $matches[$i] = trim($match, '"');

Changing the page title with Jquery

_x000D_

 var isOldTitle = true;_x000D_
        var oldTitle = document.title;_x000D_
        var newTitle = "New Title";_x000D_
        var interval = null;_x000D_
        function changeTitle() {_x000D_
            document.title = isOldTitle ? oldTitle : newTitle;_x000D_
            isOldTitle = !isOldTitle;_x000D_
        }_x000D_
        interval = setInterval(changeTitle, 700);_x000D_
_x000D_
        $(window).focus(function () {_x000D_
            clearInterval(interval);_x000D_
            $("title").text(oldTitle);_x000D_
        });

_x000D_

Changing Locale within the app itself

In Android M the top solution won't work. I've written a helper class to fix that which you should call from your Application class and all Activities (I would suggest creating a BaseActivity and then make all the Activities inherit from it.

Note: This will also support properly RTL layout direction.

Helper class:

public class LocaleUtils {

    private static Locale sLocale;

    public static void setLocale(Locale locale) {
        sLocale = locale;
        if(sLocale != null) {
            Locale.setDefault(sLocale);
        }
    }

    public static void updateConfig(ContextThemeWrapper wrapper) {
        if(sLocale != null && Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
            Configuration configuration = new Configuration();
            configuration.setLocale(sLocale);
            wrapper.applyOverrideConfiguration(configuration);
        }
    }

    public static void updateConfig(Application app, Configuration configuration) {
        if (sLocale != null && Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) {
            //Wrapping the configuration to avoid Activity endless loop
            Configuration config = new Configuration(configuration);
            // We must use the now-deprecated config.locale and res.updateConfiguration here,
            // because the replacements aren't available till API level 24 and 17 respectively.
            config.locale = sLocale;
            Resources res = app.getBaseContext().getResources();
            res.updateConfiguration(config, res.getDisplayMetrics());
        }
    }
}

Application:

public class App extends Application {
    public void onCreate(){
        super.onCreate();

        LocaleUtils.setLocale(new Locale("iw"));
        LocaleUtils.updateConfig(this, getBaseContext().getResources().getConfiguration());
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        LocaleUtils.updateConfig(this, newConfig);
    }
}

BaseActivity:

public class BaseActivity extends Activity {
    public BaseActivity() {
        LocaleUtils.updateConfig(this);
    }
}

What does "hard coded" mean?

Scenario

In a college there are many students doing different courses, and after an examination we have to prepare a marks card showing grade. I can calculate grade two ways

1. I can write some code like this

    if(totalMark <= 100 && totalMark > 90) { grade = "A+"; }
    else if(totalMark <= 90 && totalMark > 80) { grade = "A"; }
    else if(totalMark <= 80 && totalMark > 70) { grade = "B"; }
    else if(totalMark <= 70 && totalMark > 60) { grade = "C"; }

2. You can ask user to enter grade definition some where and save that data

Something like storing into a database table

In the first case the grade is common for all the courses and if the rule changes the code needs to be changed. But for second case we are giving user the provision to enter grade based on their requirement. So the code will be not be changed when the grade rules changes.

That's the important thing when you give more provision for users to define business logic. The first case is nothing but Hard Coding.

So in your question if you ask the user to enter the path of the file at the start, then you can remove the hard coded path in your code.

PHP Curl UTF-8 Charset

Simple: When you use curl it encodes the string to utf-8 you just need to decode them..

Description

string utf8_decode ( string $data )

This function decodes data , assumed to be UTF-8 encoded, to ISO-8859-1.

Error: Could not find or load main class

Project > Clean and then make sure BuildPath > Libraries has the correct Library.

How to update a git clone --mirror?

Regarding commits, refs, branches and "et cetera", Magnus answer just works (git remote update).

But unfortunately there is no way to clone / mirror / update the hooks, as I wanted...

I have found this very interesting thread about cloning/mirroring the hooks:

http://kerneltrap.org/mailarchive/git/2007/8/28/256180/thread

I learned:

The hooks are not considered part of the repository contents.
There is more data, like the .git/description folder, which does not get cloned, just as the hooks.
The default hooks that appear in the hooks dir comes from the TEMPLATE_DIR
There is this interesting template feature on git.

So, I may either ignore this "clone the hooks thing", or go for a rsync strategy, given the purposes of my mirror (backup + source for other clones, only).

Well... I will just forget about hooks cloning, and stick to the git remote update way.

Sehe has just pointed out that not only "hooks" aren't managed by the clone / update process, but also stashes, rerere, etc... So, for a strict backup, rsync or equivalent would really be the way to go. As this is not really necessary in my case (I can afford not having hooks, stashes, and so on), like I said, I will stick to the remote update.

Thanks! Improved a bit of my own "git-fu"... :-)

COLLATION 'utf8_general_ci' is not valid for CHARACTER SET 'latin1'

Firstly run this query

SHOW VARIABLES LIKE '%char%';

You have character_set_server='latin1'

If so,go into your config file,my.cnf and add or uncomment these lines:

character-set-server = utf8
collation-server = utf8_unicode_ci

Restart the server. Yes late to the party,just encountered the same issue.

How to upload a file in Django?

Extending on Henry's example:

import tempfile
import shutil

FILE_UPLOAD_DIR = '/home/imran/uploads'

def handle_uploaded_file(source):
    fd, filepath = tempfile.mkstemp(prefix=source.name, dir=FILE_UPLOAD_DIR)
    with open(filepath, 'wb') as dest:
        shutil.copyfileobj(source, dest)
    return filepath

You can call this handle_uploaded_file function from your view with the uploaded file object. This will save the file with a unique name (prefixed with filename of the original uploaded file) in filesystem and return the full path of saved file. You can save the path in database, and do something with the file later.

Getting each individual digit from a whole integer

This solution gives correct results over the entire range [0,UINT_MAX] without requiring digits to be buffered.

It also works for wider types or signed types (with positive values) with appropriate type changes.

This kind of approach is particularly useful on tiny environments (e.g. Arduino bootloader) because it doesn't end up pulling in all the printf() bloat (when printf() isn't used for demo output) and uses very little RAM. You can get a look at value just by blinking a single led :)

#include <limits.h>
#include <stdio.h>

int
main (void)
{
  unsigned int score = 42;   // Works for score in [0, UINT_MAX]

  printf ("score via printf:     %u\n", score);   // For validation

  printf ("score digit by digit: ");
  unsigned int div = 1;
  unsigned int digit_count = 1;
  while ( div <= score / 10 ) {
    digit_count++;
    div *= 10;
  }
  while ( digit_count > 0 ) {
    printf ("%d", score / div);
    score %= div;
    div /= 10;
    digit_count--;
  }
  printf ("\n");

  return 0;
}

Basic http file downloading and saving to disk in python?

For Python3+ URLopener is deprecated. And when used you will get error as below:

url_opener = urllib.URLopener() AttributeError: module 'urllib' has no attribute 'URLopener'

So, try:

import urllib.request 
urllib.request.urlretrieve(url, filename)

SqlServer: Login failed for user

For Can not connect to the SQL Server. The original error is: Login failed for user 'username'. error, port requirements on MSSQL server side need to be fulfilled.

There are other ports beyond default port 1433 needed to be configured on Windows Firewall.

https://stackoverflow.com/a/25147251/1608670

How to use template module with different set of variables?

For Ansible 2.x:

- name: template test
  template: 
    src: myTemplateFile
    dest: result1
  vars:
    myTemplateVariable: File1

- name: template test
  template: 
    src: myTemplateFile
    dest: result2
  vars:
    myTemplateVariable: File2

For Ansible 1.x:

Unfortunately the template module does not support passing variables to it, which can be used inside the template. There was a feature request but it was rejected.

I can think of two workarounds:

1. Include

The include statement supports passing variables. So you could have your template task inside an extra file and include it twice with appropriate parameters:

my_include.yml:

- name: template test
  template: 
        src=myTemplateFile
        dest=destination

main.yml:

- include: my_include.yml destination=result1 myTemplateVariable=File1

- include: my_include.yml destination=result2 myTemplateVariable=File2

2. Re-define myTemplateVariable

Another way would be to simply re-define myTemplateVariable right before every template task.

- set_fact:
     myTemplateVariable: File1

- name: template test 1
  template: 
        src=myTemplateFile
        dest=result1

- set_fact:
     myTemplateVariable: File2

- name: template test 2
  template: 
        src=myTemplateFile
        dest=result2

Is there a timeout for idle PostgreSQL connections?

A possible workaround that allows to enable database session timeout without an external scheduled task is to use the extension pg_timeout that I have developped.

Is there a better jQuery solution to this.form.submit();?

You can always JQuery-ize your form.submit, but it may just call the same thing:

$("form").submit(); // probably able to affect multiple forms (good or bad)

// or you can address it by ID
$("#yourFormId").submit();

You can also attach functions to the submit event, but that is a different concept.

Distinct() with lambda?

This will do what you want but I don't know about performance:

var distinctValues =
    from cust in myCustomerList
    group cust by cust.CustomerId
    into gcust
    select gcust.First();

At least it's not verbose.

How can I use regex to get all the characters after a specific character, e.g. comma (",")

You don't need regex to do this. Here's an example :

var str = "'SELECT___100E___7',24";
var afterComma = str.substr(str.indexOf(",") + 1); // Contains 24 //

Regexp Java for password validation

Also You Can Do like This.

 public boolean isPasswordValid(String password) {


    String regExpn =
            "^(?=.*[0-9])(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%^&+=])(?=\\S+$).{8,}$";

    CharSequence inputStr = password;

    Pattern pattern = Pattern.compile(regExpn,Pattern.CASE_INSENSITIVE);
    Matcher matcher = pattern.matcher(inputStr);

    if(matcher.matches())
        return true;
    else
        return false;
}

How to sort with a lambda?

To much code, you can use it like this:

#include<array>
#include<functional>

int main()
{
    std::array<int, 10> vec = { 1,2,3,4,5,6,7,8,9 };

    std::sort(std::begin(vec), 
              std::end(vec), 
              [](int a, int b) {return a > b; });

    for (auto item : vec)
      std::cout << item << " ";

    return 0;
}

Replace "vec" with your class and that's it.

Convert float to double without losing precision

I've encountered this issue today and could not use refactor to BigDecimal, because the project is really huge. However I found solution using

Float result = new Float(5623.23)
Double doubleResult = new FloatingDecimal(result.floatValue()).doubleValue()

And this works.

Note that calling result.doubleValue() returns 5623.22998046875

But calling doubleResult.doubleValue() returns correctly 5623.23

But I am not entirely sure if its a correct solution.

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

You can use list comprehensions.

[(k,v) for k,v in a.iteritems()]

will get you [ ('a', 1), ('b', 2), ('c', 3) ] and

[(v,k) for k,v in a.iteritems()]

the other example.

Read more about list comprehensions if you like, it's very interesting what you can do with them.

Where to find "Microsoft.VisualStudio.TestTools.UnitTesting" missing dll?

To resolve this issue, I had to do the following:

Launch the Visual Studio Installer with administrative privileges
If it prompts you to install updates to Visual Studio, do so before continuing
When prompted, click the button to Modify the existing installation
Click on the "Individual components" tab / header along the top
Scroll down to the "Debugging and testing" section
Check the box next to "Web performance and load testing tools"
Click the Modify button on the bottom right corner of the dialog to install the missing DLLs

Once the DLLs are installed, you can add references to them using the method that Agent007 indicated in his answer.

Plotting categorical data with pandas and matplotlib

You might find useful mosaic plot from statsmodels. Which can also give statistical highlighting for the variances.

from statsmodels.graphics.mosaicplot import mosaic
plt.rcParams['font.size'] = 16.0
mosaic(df, ['direction', 'colour']);

enter image description here

But beware of the 0 sized cell - they will cause problems with labels.

See this answer for details

MatPlotLib: Multiple datasets on the same scatter plot

You can also do this easily in Pandas, if your data is represented in a Dataframe, as described here:

http://pandas.pydata.org/pandas-docs/version/0.15.0/visualization.html#scatter-plot

CSS position:fixed inside a positioned element

Seems, css transforms can be used

"‘transform’ property establishes a new local coordinate system at the element",

but ... this is not cross-browser, seems only Opera works correctly

Best way to find the intersection of multiple sets?

From Python version 2.6 on you can use multiple arguments to set.intersection(), like

u = set.intersection(s1, s2, s3)

If the sets are in a list, this translates to:

u = set.intersection(*setlist)

where *a_list is list expansion

Note that set.intersection is not a static method, but this uses the functional notation to apply intersection of the first set with the rest of the list. So if the argument list is empty this will fail.

How to clear all <div>s’ contents inside a parent <div>?

$("#masterdiv > *").text("")

$("#masterdiv").children().text("")

jQuery UI Sortable Position

As per the official documentation of the jquery sortable UI: http://api.jqueryui.com/sortable/#method-toArray

In update event. use:

var sortedIDs = $( ".selector" ).sortable( "toArray" );

and if you alert or console this var (sortedIDs). You'll get your sequence. Please choose as the "Right Answer" if it is a right one.

SSH library for Java

There is a brand new version of Jsch up on github: https://github.com/vngx/vngx-jsch Some of the improvements include: comprehensive javadoc, enhanced performance, improved exception handling, and better RFC spec adherence. If you wish to contribute in any way please open an issue or send a pull request.

How to set timer in android?

ok since this isn't cleared up yet there are 3 simple ways to handle this. Below is an example showing all 3 and at the bottom is an example showing just the method I believe is preferable. Also remember to clean up your tasks in onPause, saving state if necessary.


import java.util.Timer;
import java.util.TimerTask;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.Handler.Callback;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class main extends Activity {
    TextView text, text2, text3;
    long starttime = 0;
    //this  posts a message to the main thread from our timertask
    //and updates the textfield
   final Handler h = new Handler(new Callback() {

        @Override
        public boolean handleMessage(Message msg) {
           long millis = System.currentTimeMillis() - starttime;
           int seconds = (int) (millis / 1000);
           int minutes = seconds / 60;
           seconds     = seconds % 60;

           text.setText(String.format("%d:%02d", minutes, seconds));
            return false;
        }
    });
   //runs without timer be reposting self
   Handler h2 = new Handler();
   Runnable run = new Runnable() {

        @Override
        public void run() {
           long millis = System.currentTimeMillis() - starttime;
           int seconds = (int) (millis / 1000);
           int minutes = seconds / 60;
           seconds     = seconds % 60;

           text3.setText(String.format("%d:%02d", minutes, seconds));

           h2.postDelayed(this, 500);
        }
    };

   //tells handler to send a message
   class firstTask extends TimerTask {

        @Override
        public void run() {
            h.sendEmptyMessage(0);
        }
   };

   //tells activity to run on ui thread
   class secondTask extends TimerTask {

        @Override
        public void run() {
            main.this.runOnUiThread(new Runnable() {

                @Override
                public void run() {
                   long millis = System.currentTimeMillis() - starttime;
                   int seconds = (int) (millis / 1000);
                   int minutes = seconds / 60;
                   seconds     = seconds % 60;

                   text2.setText(String.format("%d:%02d", minutes, seconds));
                }
            });
        }
   };


   Timer timer = new Timer();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        text = (TextView)findViewById(R.id.text);
        text2 = (TextView)findViewById(R.id.text2);
        text3 = (TextView)findViewById(R.id.text3);

        Button b = (Button)findViewById(R.id.button);
        b.setText("start");
        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Button b = (Button)v;
                if(b.getText().equals("stop")){
                    timer.cancel();
                    timer.purge();
                    h2.removeCallbacks(run);
                    b.setText("start");
                }else{
                    starttime = System.currentTimeMillis();
                    timer = new Timer();
                    timer.schedule(new firstTask(), 0,500);
                    timer.schedule(new secondTask(),  0,500);
                    h2.postDelayed(run, 0);
                    b.setText("stop");
                }
            }
        });
    }

    @Override
    public void onPause() {
        super.onPause();
        timer.cancel();
        timer.purge();
        h2.removeCallbacks(run);
        Button b = (Button)findViewById(R.id.button);
        b.setText("start");
    }
}

the main thing to remember is that the UI can only be modified from the main ui thread so use a handler or activity.runOnUIThread(Runnable r);

Here is what I consider to be the preferred method.


import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class TestActivity extends Activity {

    TextView timerTextView;
    long startTime = 0;

    //runs without a timer by reposting this handler at the end of the runnable
    Handler timerHandler = new Handler();
    Runnable timerRunnable = new Runnable() {

        @Override
        public void run() {
            long millis = System.currentTimeMillis() - startTime;
            int seconds = (int) (millis / 1000);
            int minutes = seconds / 60;
            seconds = seconds % 60;

            timerTextView.setText(String.format("%d:%02d", minutes, seconds));

            timerHandler.postDelayed(this, 500);
        }
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.test_activity);

        timerTextView = (TextView) findViewById(R.id.timerTextView);

        Button b = (Button) findViewById(R.id.button);
        b.setText("start");
        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Button b = (Button) v;
                if (b.getText().equals("stop")) {
                    timerHandler.removeCallbacks(timerRunnable);
                    b.setText("start");
                } else {
                    startTime = System.currentTimeMillis();
                    timerHandler.postDelayed(timerRunnable, 0);
                    b.setText("stop");
                }
            }
        });
    }

  @Override
    public void onPause() {
        super.onPause();
        timerHandler.removeCallbacks(timerRunnable);
        Button b = (Button)findViewById(R.id.button);
        b.setText("start");
    }

}

Programs & Examples On #Variables

How to use Global Variables in C#?

set value of input field by php variable's value

accessing a variable from another class

Objective-C Static Class Level variables

How to add elements to an empty array in PHP?

How to store standard error in a variable

How to initialize a variable of date type in java?

How do I save and restore multiple variables in python?

Why does dividing two int not yield the right value when assigned to double?

ISO C90 forbids mixed declarations and code in C

PHP class: Global variable as property in class

Dynamic variable names in Bash

How to reference a file for variables using Bash?

The short answer

An example using source

config.sh

script.sh

Another way

How do JavaScript closures work?

Environment variables in Eclipse

Python Function to test ping

More elegant way of declaring multiple variables at the same time

How to obtain values of request variables using Python and Flask

Passing Variable through JavaScript from one html page to another page

Passing a variable from one php include file to another: global vs. not

How to pass a list from Python, by Jinja2 to JavaScript

The view

The template

Edit - exact answer

The view

The template

Edit 2

Edit 3 (Security warning)

When should an Excel VBA variable be killed or set to Nothing?

Is it possible to print a variable's type in standard C++?

What is the purpose of the single underscore "_" variable in Python?

How to delete an instantiated object Python?

Getting the name of a variable as a string

Determine if variable is defined in Python

What is a None value?

What does ${} (dollar sign and curly braces) mean in a string in Javascript?

Will using 'var' affect performance?

Create timestamp variable in bash script

VBA Check if variable is empty

Define a global variable in a JavaScript function

Use YAML with variables

Define a value and use an exact copy of it later:

Define an object and use it with modifications later:

Splitting a continuous variable into equal sized groups

Mixing a PHP variable with a string literal

JUnit Testing private variables?

How do I use variables in Oracle SQL Developer?

shared global variables in C

How to swap two variables in JavaScript

Convert dictionary to bytes and back again python?

Convert Variable Name to String?

Java system properties and environment variables

How to check if a variable is set in Bash?

Expansion of variables inside single quotes in a command in Bash

Viewing all defined variables

Check if object exists in JavaScript

Save current directory in variable using Bash?

While variable is not defined - wait

How can I simulate an array variable in MySQL?

Is an array variable really necessary?

Standard Practice

printf a variable in C

How do you use script variables in psql?

MySQL: @variable vs. variable. What's the difference?

How to return the output of stored procedure into a variable in sql server

How can I print variable and string on same line in Python?

PHP Multiple Checkbox Array

Using variables inside a bash heredoc

Remove an element from a Bash array

What is the meaning of @_ in Perl?

Multiple left-hand assignment with JavaScript

How do I get the type of a variable?

How can I determine if a variable is 'undefined' or 'null'?

How to trim whitespace from a Bash variable?

An example using `source`