You should take a look to [psutil][1] : 

    &gt;&gt;&gt; import psutil
    &gt;&gt;&gt; psutil.virtual_memory()
    svmem(total=16717422592, available=5376126976, percent=67.8, used=10359984128, free=1831890944, active=7191916544, inactive=2325667840, buffers=525037568, cached=4000509952, shared=626225152)

  [1]: https://github.com/giampaolo/psutil

I&#39;m building a WebClient library. Now I&#39;m implementing a proxy feature, so I am making some research and I saw some code using the `CONNECT` method to request a URL.

But checking it within my web browser, it doesn&#39;t use the `CONNECT` method but calls the GET method instead.

So I&#39;m confused. When I should use both methods?

When should one use CONNECT and GET HTTP methods at HTTP Proxy Server?

I&#39;m having problem with nested loop. I have multiple number of posts, and each post has multiple number of images. 

I want to get total of 5 images from all posts. So I am using nested loop to get the images, and want to break the loop when the number reaches to 5. The following code will return the images, but does not seem to break the loop.


&lt;?

    foreach($query-&gt;posts as $post){
    		if ($images = get_children(array(
    					&#39;post_parent&#39; =&gt; $post-&gt;ID,
    					&#39;post_type&#39; =&gt; &#39;attachment&#39;,
    					&#39;post_mime_type&#39; =&gt; &#39;image&#39;))
    			){				
    				$i = 0;
    				foreach( $images as $image ) {
    					..
    					//break the loop?
    					if (++$i == 5) break;
    				}				
    			}
    }

Breaking the nested loop

&gt; **Possible Duplicate:**  
&gt; [How to get current CPU and RAM usage in Python?](https://stackoverflow.com/questions/276052/how-to-get-current-cpu-and-ram-usage-in-python)  

&lt;!-- End of automatically inserted text --&gt;

How can I get the available and currently used memory from Python? It need to be cross-platform and at least work on at least Windows, Mac OS X and Linux.

I&#39;d like to report the user in my application that he doesn&#39;t have enough memory free to proceed and do the next operation.


Available and used System Memory in Python?

> Possible Duplicate: 
> <a href="https://stackoverflow.com/questions/276052/how-to-get-current-cpu-and-ram-usage-in-python" target="_blank" rel="noopener noreferrer">How to get current CPU and RAM usage in Python?</a>

How can I get the available and currently used memory from Python? It need to be cross-platform and at least work on at least Windows, Mac OS X and Linux.
I'd like to report the user in my application that he doesn't have enough memory free to proceed and do the next operation.

Is there any python package that allows the efficient computation of the PDF (probability density function) of a [multivariate normal distribution][1]?

It doesn&#39;t seem to be included in Numpy/Scipy, and surprisingly a Google search didn&#39;t turn up any useful thing.


  [1]: https://en.wikipedia.org/wiki/Multivariate_normal_distribution

Multivariate normal density in Python?

I am having trouble installing psycopg2. I get the following error when I try to `pip install psycopg2`:

    Error: pg_config executable not found.
    
    Please add the directory containing pg_config to the PATH
    
    or specify the full executable path with the option:
    
    
    
        python setup.py build_ext --pg-config /path/to/pg_config build ...
    
    
    
    or with the pg_config option in &#39;setup.cfg&#39;.
    
    ----------------------------------------
    Command python setup.py egg_info failed with error code 1 in /tmp/pip-build/psycopg2


But the problem is `pg_config` is actually in my `PATH`; it runs without any problem:

    $ which pg_config
    /usr/pgsql-9.1/bin/pg_config

I tried adding the pg_config path to the `setup.cfg` file and building it using the source files I downloaded from their website (http://initd.org/psycopg/) and I get the following error message!

    Error: Unable to find &#39;pg_config&#39; file in &#39;/usr/pgsql-9.1/bin/&#39;


But it is actually THERE!!!

I am baffled by these errors. Can anyone help please?

By the way, I `sudo` all the commands. Also I am on RHEL 5.5.

pg_config executable not found

When I type small integers with a 0 in front into python, they give weird results. Why is this?

    &gt;&gt;&gt; 011
    9
    &gt;&gt;&gt; 0100
    64
    &gt;&gt;&gt; 027
    23

I&#39;m using Python 2.7.3. I have tested this in Python 3.0, and apparently this is now an error. So it is something version-specific.

They are apparently still integers:

    &gt;&gt;&gt; type(027)
    &lt;type &#39;int&#39;&gt;

What do numbers starting with 0 mean in python?

I want to figure out how to remove nan values from my array. My array looks something like this: 

    x = [1400, 1500, 1600, nan, nan, nan ,1700] #Not in this exact configuration

How can I remove the `nan` values from `x`?

Removing nan values from an array

I am trying to make a simple calculator to determine whether or not a certain year is a leap year. 

By definition, a leap year is divisible by four, but not by one hundred, unless it is divisible by four hundred.

Here is my code:

    def leapyr(n):
        if n%4==0 and n%100!=0:
            if n%400==0:
                print(n, &quot;is a leap year.&quot;)
        elif n%4!=0:
            print(n, &quot;is not a leap year.&quot;)
    print(leapyr(1900))

When I try this inside the Python IDLE, the module returns `None`. I am pretty sure that I should get `1900 is a leap year`.

How to determine whether a year is a leap year?

I&#39;m trying to understand the use of `dup2` and `dup`. 

From the man page : 

    DESCRIPTION
    
    dup and dup2 create a copy of the file descriptor oldfd.
    After successful return of dup or dup2, the old and new descriptors may
    be used interchangeably. They share locks, file position pointers and
    flags; for example, if the file position is modified by using lseek on
    one of the descriptors, the position is also changed for the other.
    
    The two descriptors do not share the close-on-exec flag, however.
    
    dup uses the lowest-numbered unused descriptor for the new descriptor.
    
    dup2 makes newfd be the copy of oldfd, closing newfd first if necessary.  
    
    RETURN VALUE
    
    dup and dup2 return the new descriptor, or -1 if an error occurred 
    (in which case, errno is set appropriately).  

Why would I need that system call? what is the use of duplicating the file descriptor? 

If I have the file descriptor, why would I want to make a copy of it? 

I&#39;d appreciate if you could explain and give me an example where `dup2` / `dup` is needed. 

Thanks

dup2 / dup - why would I need to duplicate a file descriptor?

Is there a way to detect the operating system in ruby? I am working on developing a sketchup tool that will need to detect Mac vs. Windows. 

Detecting Operating Systems in Ruby

For Linux this would give me `/`, for Windows on the C drive that would give me `C:\\`. Note that python is not necessarily installed on the C drive on windows.

A system independent way using python to get the root directory/drive on which python is installed

I&#39;m sure mutex isn&#39;t enough that&#39;s the reason the concept of condition variables exist; but it beats me and I&#39;m not able to convince myself with a concrete scenario when a condition variable is essential.

https://stackoverflow.com/questions/1055398/differences-between-conditional-variables-mutexes-and-locks question&#39;s accepted answer says that a condition variable is a 

&gt; lock with a &quot;signaling&quot; mechanism. It is used when threads need to
&gt; wait for a resource to become available. A thread can &quot;wait&quot; on a CV
&gt; and then the resource producer can &quot;signal&quot; the variable, in which
&gt; case the threads who wait for the CV get notified and can continue
&gt; execution

Where I get confused is that, a thread can wait on a mutex too, and when it gets signalled, is simply means the variable is now available, why would I need a condition variable?

P.S.: Also, a mutex is required to guard the condition variable anyway, when makes my vision more askew towards not seeing condition variable&#39;s purpose.

When is a condition variable needed, isn&#39;t a mutex enough?

Is there any good way to get the remaining memory available to the JVM at run time? The use case of this would be to have web services which fail gracefully when they are nearing their memory limits by refusing new connections with a nice error message &quot;too many people using this, try again later&quot;, rather than dying abruptly with an OutOfMemory error.

Note this has nothing to do with calculating/estimating the cost of each object beforehand. In principle I could estimate how much memory my objects take and refuse new connections based on that estimate, but that seems kind of hacky/fragile.



Java get available memory

Is there a package out there, for Ubuntu and/or CentOS, that has a command-line tool that can execute an XPath one-liner like `foo //element@attribute filename.xml` or `foo //element@attribute &lt; filename.xml` and return the results line by line?

I&#39;m looking for something that would allow me to just `apt-get install foo` or `yum install foo` and then just works out-of-the-box, no wrappers or other adaptation necessary.

Here are some examples of things that come close:

Nokogiri. If I write this wrapper I could call the wrapper in the way described above:

    #!/usr/bin/ruby

    require &#39;nokogiri&#39;

    Nokogiri::XML(STDIN).xpath(ARGV[0]).each do |row|
      puts row
    end

XML::XPath. Would work with this wrapper:

    #!/usr/bin/perl

    use strict;
    use warnings;
    use XML::XPath;

    my $root = XML::XPath-&gt;new(ioref =&gt; &#39;STDIN&#39;);
    for my $node ($root-&gt;find($ARGV[0])-&gt;get_nodelist) {
      print($node-&gt;getData, &quot;\n&quot;);
    }

`xpath` from XML::XPath returns too much noise, `-- NODE --` and `attribute = &quot;value&quot;`.

`xml_grep` from XML::Twig cannot handle expressions that do not return elements, so cannot be used to extract attribute values without further processing.

EDIT:

`echo cat //element/@attribute | xmllint --shell filename.xml` returns noise similar to `xpath`.

`xmllint --xpath //element/@attribute filename.xml` returns `attribute = &quot;value&quot;`.

`xmllint --xpath &#39;string(//element/@attribute)&#39; filename.xml` returns what I want, but only for the first match.

For another solution almost satisfying the question, here is an XSLT that can be used to evaluate arbitrary XPath expressions (requires dyn:evaluate support in the XSLT processor):

    &lt;?xml version=&quot;1.0&quot;?&gt;
    &lt;xsl:stylesheet xmlns:xsl=&quot;http://www.w3.org/1999/XSL/Transform&quot; version=&quot;1.0&quot;
        xmlns:dyn=&quot;http://exslt.org/dynamic&quot; extension-element-prefixes=&quot;dyn&quot;&gt;
      &lt;xsl:output omit-xml-declaration=&quot;yes&quot; indent=&quot;no&quot; method=&quot;text&quot;/&gt;
      &lt;xsl:template match=&quot;/&quot;&gt;
        &lt;xsl:for-each select=&quot;dyn:evaluate($pattern)&quot;&gt;
          &lt;xsl:value-of select=&quot;dyn:evaluate($value)&quot;/&gt;
          &lt;xsl:value-of select=&quot;&#39;&amp;#10;&#39;&quot;/&gt;
        &lt;/xsl:for-each&gt; 
      &lt;/xsl:template&gt;
    &lt;/xsl:stylesheet&gt;

Run with `xsltproc --stringparam pattern //element/@attribute --stringparam value . arbitrary-xpath.xslt filename.xml`.

How to execute XPath one-liners from shell?

I&#39;ve worked for some time with Corona SDK and love how fast and easy I can create powerful apps using Lua. But it can only compile for iOS and Android, which feels like too little now.

My main interest is for it to be able to compile to Desktop AND Mobile. At least for the following:

 - Windows + Mac for desktop, as standalone applications.  
 - iOS + Android for mobile.


I&#39;d prefer it to lean more towards Lua type scripting instead of ActionScript, but please feel free to post anything that you have worked with and love.

I&#39;ve found the following engines so far:

 - [Marmalade Quick][1] - After further looking into it, Marmalade Quick can only build for Mobile!
 - [IwGame][2] - Works on top of marmalade and says it can deploy to
   desktop and mobile with Lua. Any info is greatly appreciated on this
 - [sio2][3] - Says &quot;SIO2 is an OpenGLES based cross-platform 2D and 3D
   game engine for iOS, Android, MacOS and Windows&quot; and &quot;The engine also
   allows you to port your game on the Mac Store and on Windows.&quot;, but
   their forum and web title is &quot;Game Engine for Mobile Devices&quot;. Can&#39;t
   find any info on if it can deploy to desktop platforms, any info is
   greatly appreciated again.
 - [Loom Engine][4] - Loom is similar to Haxe + OpenFL (attempts to attract Flash developers) in that it uses AS3-like of ECMAScript, but it doesn&#39;t build native code from it. However it uses Cocos2D for rendering so it should in theory be as fast as Cocos2D. -- Thanks to Bojan. 
 - [SDL][5] - I&#39;ve read in multiple places that SDL can deploy to nearly any platform or device and has a Lua binding. But i can&#39;t find how this works as it&#39;s not an engine. Any one who can explain how it works and if it&#39;s possible is once again, very much appreciated.
 - [SFML][6] - &quot;Windows, Linux, Mac OS X and soon Android &amp; iOS. &quot; doesn&#39;t use Lua but can use other languages like Java and Python etc. Anyone have any information on this?
 - [Torgue2D][7] - &quot;Torque 2D was developed with OS X, Windows, and iOS devices in mind and works equally well on all the platforms.&quot; uses TorgueScript and no Android =(
 - [Sencha][8] - Seems to compile to all platforms, uses Javascript too which I know. But even with V8 JS would this work well performance wise compared to other options?
 - [GameMaker][9] - own scripting language GML and I actually remember this one as a tool for non-programmers. Has it actually grown into a real engine, I mean for serious development?
 - [Construct2][10] - Same question as gamemaker
 - [Corona][11] - Lua but mobile only (Android and iOS only as well)
 - [Cocos2D][12] - Seems like it has lots of options but not sure with the same language? Seems like you&#39;d have to re-write your entire code. Any info if cocos2D can deploy to desktop + mobile with almost the same code would be greatly appreciated.
 - [Angel2D][13] - Says it can deploy to everything except Android and uses Lua, anyone ever used this one before?
 - [libgdx][14] --- I&#39;ve only seen good things about this. Here is a benchmark test for libgdx and is where I saw it reaching 40k sprites at 60fps. http://www.sparkrift.com/2012/1/love2d-vs-allegro-vs-clanlib-vs-libgdx-vs-cocos2d-x-vs-monogame-vs-xna-vs-sfml . It seems libgdx barely goes over 30k actually. But still seems amazing. This is on the same level as Qt for me, almost perfect, except I&#39;m not really worried about performance on it. libgdx can build for everything pretty much.
 - [XNA][15] + [MonoGame][16] --- MonoGame&#39;s performance seems only slightly lower than libgdx, can build to most platforms. However I don&#39;t know much about XNA and I heard it won&#39;t be receiving future updates, but is quite stable? More information is welcome.
 - [Citrus][17] --- Don&#39;t have much information on Citrus either. AS3 game engine that can build for iOS, Android, Windows, Mac and more.
 - [Haxe][18] + [OpenFL][19] --- OpenFL (Haxe) builds to native on many platforms, not just to Flash. Windows, Mac, Linux and Android all get optional native deployment or OpenFL runtime called Neko which is in theory faster than Flash, and SDL 2.0 will enable iOS deployment soon(ish). -- Thanks to Bojan.
 - [Qt-Project][20] --- Just linking Qt project here, can build for everything and has a pretty big community with lots of third party libraries to help you even further.
 - [Moai][21] ---The only Lua engine that I know that can build for Desktop and Mobile. Only downside is the community isn&#39;t that big and documentation isn&#39;t the best. But if you can get passed those this is a great solution and the one I&#39;m currently using.
 - [Adobe][22] --- Can&#39;t forget to add adobe here since it can build to everything that supports flash.
 - [Unity3D][24] --- Recently announced 2D integration looks very promising, should be released Q3-Q4 of 2013.
 - [Cocos2d-x][29] --- An open source engine. Supports JS, Lua, C++ and multiple platforms.
 - [Html5][23] --- There seem to be a lot of emphasise on html5 mobile apps, here are just a few tools I found that can help port your html5 project to a platform:


    

 1. [Chromium embedded][25]

   

 2. [Sencha][26]

 3. [Phonegap][27]

    

 4. [Appcelerator/Titanium][28]
 5. Icenium

So, I&#39;d be happy if you could comment from your experiences with any engines and suggest which one you would recommend. 
Thank you for your help!

EDIT: Since this topic is getting popular I&#39;ll be adding other options I&#39;ve found over time. I suggest you choose what is most familiar to you and best for your project needs.


  [1]: http://www.madewithmarmalade.com/quick
  [2]: http://www.drmop.com/index.php/iwgame-engine/
  [3]: http://sio2interactive.com/index.php
  [4]: http://theengine.co/
  [5]: http://www.libsdl.org/
  [6]: http://www.sfml-dev.org/
  [7]: http://www.garagegames.com/products/torque-2d/features
  [8]: http://www.sencha.com/products/complete/
  [9]: http://www.yoyogames.com/gamemaker/studio
  [10]: https://www.scirra.com/construct2
  [11]: http://www.coronalabs.com/
  [12]: http://www.cocos2d-x.org/
  [13]: http://angel2d.com/
  [14]: http://libgdx.badlogicgames.com/
  [15]: http://en.wikipedia.org/wiki/Microsoft_XNA
  [16]: http://www.monogame.net/
  [17]: http://citrusengine.com/features/
  [18]: http://haxe.org/
  [19]: http://www.openfl.org/
  [20]: http://qt-project.org/
  [21]: http://getmoai.com/
  [22]: http://gaming.adobe.com/showcase/
  [23]: http://en.wikipedia.org/wiki/HTML5
  [24]: http://unity3d.com
  [25]: http://code.google.com/p/chromiumembedded/
  [26]: http://www.sencha.com/products/complete/
  [27]: http://phonegap.com/
  [28]: http://www.appcelerator.com/
  [29]: http://www.cocos2d-x.org/

2D Cross-Platform Game Development Engines

Android with [NDK][1] has support to C/C++ code and iOS with [Objective-C++][2] has support too, so how can I write applications with native C/C++ code shared between Android and iOS?


  [1]: https://developer.android.com/ndk/index.html
  [2]: https://en.wikipedia.org/wiki/Objective-C#Objective-C.2B.2B

How to use the same C++ code for Android and iOS?

I need to store a 128 bits long [UUID][1] in a variable. Is there a 128-bit datatype in C++? I do not need arithmetic operations, I just want to easily store and read the value very fast.

A new feature from C++11 would be fine, too.


  [1]: http://en.wikipedia.org/wiki/UUID

Content Type	Original Author	Original Content on Stackoverflow
Question	Johan Dahlin	View Question on Stackoverflow
Solution 1 - Python	Cédric Julien	View Answer on Stackoverflow

Available and used System Memory in Python?

Python Problem Overview

Python Solutions

Solution 1 - Python

Breaking the nested loop

When should one use CONNECT and GET HTTP methods at HTTP Proxy Server?

Attributions