Because sometimes you just need a spinlock

spinlock.py

@contextmanager
def spinlock(key, suffix=":lock", duration=1, spinsleep=0.01):
    """ A simple Redis-based spinlock for situations where pessimistic locking
        makes life simpler, and the chance of collisions is low enough that
        a spinlock is a reasonable tradeoff.

        The lock is held for at most ``duration`` seconds (after which it's
        ignored), and polled every ``spinsleep`` seconds.

        For example::

            with spinlock("my-key"):
                print "lock held on my-key"
    """

    end_time = time.time() + duration
    lock_key = "%s%s" %(key, suffix)
    with get_redis_connection() as cxn:
        while True:
            if time.time() > end_time:
                break
            first = cxn.set(lock_key, "held", nx=True, ex=duration)
            if first:
                break
            time.sleep(spinsleep)
        try:
            yield cxn
        finally:
            cxn.delete(lock_key)