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:mod:`mutex` --- Mutual exclusion support ========================================= .. module:: mutex :synopsis: Lock and queue for mutual exclusion. :deprecated: .. deprecated:: 2.6 The :mod:`mutex` module has been removed in Python 3. .. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il> The :mod:`mutex` module defines a class that allows mutual-exclusion via acquiring and releasing locks. It does not require (or imply) :mod:`threading` or multi-tasking, though it could be useful for those purposes. The :mod:`mutex` module defines the following class: .. class:: mutex() Create a new (unlocked) mutex. A mutex has two pieces of state --- a "locked" bit and a queue. When the mutex is not locked, the queue is empty. Otherwise, the queue contains zero or more ``(function, argument)`` pairs representing functions (or methods) waiting to acquire the lock. When the mutex is unlocked while the queue is not empty, the first queue entry is removed and its ``function(argument)`` pair called, implying it now has the lock. Of course, no multi-threading is implied -- hence the funny interface for :meth:`lock`, where a function is called once the lock is acquired. .. _mutex-objects: Mutex Objects ------------- :class:`mutex` objects have following methods: .. method:: mutex.test() Check whether the mutex is locked. .. method:: mutex.testandset() "Atomic" test-and-set, grab the lock if it is not set, and return ``True``, otherwise, return ``False``. .. method:: mutex.lock(function, argument) Execute ``function(argument)``, unless the mutex is locked. In the case it is locked, place the function and argument on the queue. See :meth:`unlock` for explanation of when ``function(argument)`` is executed in that case. .. method:: mutex.unlock() Unlock the mutex if queue is empty, otherwise execute the first element in the queue.