python lock with-statement and timeout

Question

我使用的Python 3序列如下所示：

lock = threading.Lock()
res = lock.acquire(timeout=10)
if res:
    # do something ....
    lock.release()
else:
    # do something else ...

我更喜欢使用with-语句，而不是显式的"acquire“和"release"，但我不知道如何获得超时效果。

Answer 1

使用上下文管理器可以很容易地做到这一点：

import threading
from contextlib import contextmanager

@contextmanager
def acquire_timeout(lock, timeout):
    result = lock.acquire(timeout=timeout)
    yield result
    if result:
        lock.release()


# Usage:
lock = threading.Lock()

with acquire_timeout(lock, 2) as acquired:
    if acquired:
        print('got the lock')
        # do something ....
    else:
        print('timeout: lock not available')
        # do something else ...

*注意:这在Python2.x中不起作用，因为Lock.acquire没有timeout参数

Answer 2

稍微好一点的版本：

import threading
from contextlib import contextmanager


class TimeoutLock(object):
    def __init__(self):
        self._lock = threading.Lock()

    def acquire(self, blocking=True, timeout=-1):
        return self._lock.acquire(blocking, timeout)

    @contextmanager
    def acquire_timeout(self, timeout):
        result = self._lock.acquire(timeout=timeout)
        yield result
        if result:
            self._lock.release()

    def release(self):
        self._lock.release()

# Usage:
lock = TimeoutLock()

with lock.acquire_timeout(3) as result:
    if result:
        print('got the lock')
        # do something ....
    else:
        print('timeout: lock not available')
        # do something else ...

看起来你不能继承threading.Lock的子类，所以我不得不做一个包装类来代替。