Python 上下文关系

import socket
import contextlib

@contextlib.contextmanager
def con(host,port):
    sk = socket.socket()
    sk.bind((host,port))
    sk.listen(5)
    try:
        print ("auto connect")
        yield
        print ("============")
    finally:
        print ("finally close")
        sk.close()


with con('127.0.0.1',8888) as sock:
    print ("sock auto close")
执行结果：

auto connect
sock auto close
============
finally close

 另一个示例：

__author__ = 'alex'
#coding:utf-8
import contextlib

@contextlib.contextmanager
def worker_state(state_list, worker_thread):
    """
    用于记录线程中正在等待的线程数
    """
    state_list.append(worker_thread)
    try:
        print ("begin yield")
        yield
        print ("stop yield")
    finally:
        print ("begin finally")
        state_list.remove(worker_thread)
        print ("stop finally")


free_list = []
current_list = "alex"

with worker_state(free_list,current_list):
    print (123)
    print (456)

执行结果：

begin yield
123
456
stop yield
begin finally
stop finally