twisted.internet.defer.DeferredLock : API documentation

A lock for event driven systems.

Instance Variables locked True when this Lock has been acquired, false at all other times. Do not change this value, but it is useful to examine for the equivalent of a "non-blocking" acquisition.

Method	acquire	Attempt to acquire the lock. Returns a `Deferred` that fires on lock acquisition with the `DeferredLock` as the value. If the lock is locked, then the Deferred is placed at the end of a waiting list.
Method	release	Release the lock. If there is a waiting list, then the first `Deferred` in that waiting list will be called back.
Method	_cancelAcquire	Remove a deferred d from our waiting list, as the deferred has been canceled.

Inherited from _ConcurrencyPrimitive:

Method	__init__	Undocumented
Method	run	Acquire, run, release.
Method	_releaseAndReturn	Undocumented

def _cancelAcquire(self, d): (source)

Remove a deferred d from our waiting list, as the deferred has been canceled.

Note: We do not need to wrap this in a try/except to catch d not being in self.waiting because this canceller will not be called if d has fired. release() pops a deferred out of self.waiting and calls it, so the canceller will no longer be called.

Parameters d The deferred that has been canceled.

def acquire(self): (source)

Attempt to acquire the lock. Returns a Deferred that fires on lock acquisition with the DeferredLock as the value. If the lock is locked, then the Deferred is placed at the end of a waiting list.

Returns a Deferred which fires on lock acquisition. (type: a Deferred )

def release(self): (source)

Release the lock. If there is a waiting list, then the first Deferred in that waiting list will be called back.

Should be called by whomever did the acquire() when the shared resource is free.

t.i.d.DeferredLock(_ConcurrencyPrimitive) : class documentation