上下文管理contextlib

contextmanager

from contextlib import contextmanager

class Query(object):

    def __init__(self, name):
        self.name = name

    def query(self):
        print('Query info about %s...' % self.name)

@contextmanager
def create_query(name):
    print('Begin')
    q = Query(name)
    try:
        yield q
    finally:
        print('End')

with create_query("zhangsan") as zs:
    zs.query()

输出

Begin
Query info about zhangsan...
End

cosling

返回一个在语句块执行完成时关闭 things 的上下文管理器。这基本上等价于

from contextlib import contextmanager

@contextmanager
def closing(thing):
    try:
        yield thing
    finally:
        thing.close()

from contextlib import closing
from urllib.request import urlopen

with closing(urlopen('http://www.python.org')) as page:
    for line in page:
        print(line)