python lock with-statement and timeout

问题

I am using a Python 3 sequence like this:

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

I would prefer to use a with-statement instead of explicit "acquire" and "release", but I don't know how to get the timeout effect.

回答1:

You can do this pretty easily with a context manager:

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 ...

*Note: This won't work in Python 2.x since there isn't a timeout argument to Lock.acquire

回答2:

Slightly nicer version:

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 ...

It appears you can't subclass threading.Lock, so I had to make a wrapper class instead.

来源：https://stackoverflow.com/questions/16740104/python-lock-with-statement-and-timeout

标签

python-3.x

locking

with-statement