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"""
The Pool module provides some classes for managing a fixed-size thread-safe pool of functionally identical objects. One use for this is database connections, which tend to take awhile to create.

Pool
class that manages the pool of objects.

Constructor
class used to create new instances of items in the Pool.

For more details, use pydoc or read the docstrings in the code.

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Install command line tools:

then run this:

git config --global diff.tool bc3
git config --global difftool.bc3 trustExitCode true
git config --global merge.tool bc3

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//
//  CustomCollectionFlowLayout.h
//  evilapples
//
//  http://stackoverflow.com/questions/13511733/how-to-make-supplementary-view-float-in-uicollectionview-as-section-headers-do-i
//
//

#import <UIKit/UIKit.h>

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#WSGI:(web server gateway interface)WEB服务器网关接口 WSGI是为python语言定义的web服务器和web应用程序或框架之间的一种简单而实用的借口。wsgi是一个web组件的接口规范，它将web组件分为三类：server，middleware，application

##wsgi server wsgi server可以理解为一个符合wsgi规范的web server，接收request请求，封装一系列环境变量，按照wsgi规范调用注册的wsgi app，最后将response返回给客户端。文字很难解释清楚wsgi server到底是什么东西，以及做些什么事情，最直观的方式还是看wsgi server的实现代码。以python自带的wsgiref为例，wsgiref是按照wsgi规范实现的一个简单wsgi server。其工作流程如下：

1. 服务器创建socket，监听端口，等待客户端连接。
2. 当有请求来时，服务器解析客户端信息放到环境变量environ中，并调用绑定的handler来处理请求。
3. handler解析这个http请求，将请求信息例如method，path等放到environ中。
4. wsgi handler再将一些服务器端信息也放到environ中，最后服务器信息，客户端信息，本次请求信息全部都保存到了环境变量environ中。

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# post_commit and post_rollback transaction signals for Django with monkey patching
# Author Grégoire Cachet <gregoire.cachet@gmail.com>
# http://gist.github.com/247844
# 
# Usage:
# You have to make sure to load this before you use signals.
# For example, create utils/__init__.py and then utils/transaction.py contening 
# this gist in you project. Then add "import utils.transaction" in your project
# __init__.py file
# 

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Transforming Code into Beautiful, Idiomatic Python

Notes from Raymond Hettinger's talk at pycon US 2013 video, slides.

The code examples and direct quotes are all from Raymond's talk. I've reproduced them here for my own edification and the hopes that others will find them as handy as I have!

Looping over a range of numbers

for i in [0, 1, 2, 3, 4, 5]:

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# Public Domain, i.e. feel free to copy/paste
# Considered a hack in Python 2

import inspect

def caller_name(skip=2):
    """Get a name of a caller in the format module.class.method
    
       `skip` specifies how many levels of stack to skip while getting caller
       name. skip=1 means "who calls me", skip=2 "who calls my caller" etc.

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import threading


# Based on tornado.ioloop.IOLoop.instance() approach.
# See https://github.com/facebook/tornado
class SingletonMixin(object):
	__singleton_lock = threading.Lock()
	__singleton_instance = None

	@classmethod