- 常见的上下文管理 open 文件操作
with open('hello.txt', 'w') as f:
f.write('hello, world!')
f = open('hello.txt', 'w')
try:
f.write('hello, world')
finally:
f.close()
- 常用的上下文管理 threading.Lock 锁操作
some_lock = threading.Lock()
# Harmful:
some_lock.acquire()
try:
# Do something...
finally:
some_lock.release()
# Better:
with some_lock:
# Do something...
- context manager 上下文管理
如果想实现上下文管理机制， 需要做的只是 __enter__ and __exit__ 方法
或者是使用 contextmanager 装饰器
class ManagedFile:
def __init__(self, name):
self.name = name
def __enter__(self):
self.file = open(self.name, 'w')
return self.file
def __exit__(self, exc_type, exc_val, exc_tb):
if self.file:
self.file.close()
# 使用装饰器
from contextlib import contextmanager
@contextmanager
def managed_file(name):
try:
f = open(name, 'w')
yield f
finally:
f.close()
