CloseableQueue 0.9.1.1

These classes and functions provide the facility to close a queue and to use it as an iterator.

The CloseableQueue module includes the Closeable*Queue classes as well as the Closed exception and some utility functions.

These classes and functions provide the facility to close a queue and to use it as an iterator.

The Closeable*Queue classes

The CloseableQueue class adds to Queue.Queue the means to permanently close a queue.

This is intended to provide queue support for functionality that would otherwise be implemented through the use of sentinel values or other mechanisms. Such workarounds can be particularly awkward in the case of multi-consumer queues.

CloseableQueue class provides both a close method and an extra parameter, last, to its put method.

CloseableLifoQueue and CloseablePriorityQueue are similar classes which subclass Queue.LifoQueue and Queue.PriorityQueue respectively.

Further details are available in the docstrings of the classes and their methods.

CloseableQueueFactory

This factory function is used to create the Closeable*Queue classes.

This approach is used instead of a mixin class because the Queue module’s classes are old-style.

It should be possible to apply this function to other Queue-derived classes, as long as they have not overridden get or put (or defined close or closed).

For example:

>>> CloseableFooQueue = CloseableQueueFactory(FooQueue,
...                                           "CloseableFooQueue")

The Closed exception class

Both the get and put methods of a CloseableQueue object may raise Closed if called on a closed queue.

Note that get will only raise Closed if the queue is empty.

Iteration utility functions

Transformation of iterables to and from queues is made convenient via the enqueue and dequeue functions.

The EnqueueThread function provides a further layer of convenience.

Although designed to work with closeable queues, these functions can also be meaningfully applied to other Queues.

See their docstrings for more information.

Tests

The CloseableQueue test suite is based on, and reuses much of the code from, the test suite for the standard library’s Queue module.

Regression tests are performed on the CloseableQueue class, in addition to tests of the closing functionality.

Although the tests are reasonably thorough, the author is by no means an expert in the area of concurrency; review by more experienced developers is quite welcome.

The test suite may provide guidance in the form of simplistic usage examples.

Some attempt has been made to write code which will work on older Pythons, however testing has only been performed on Python 2.6, and the author has little experience with older versions.

Distribution

CloseableQueue is available via PyPI, or from the github repo.

License

The CloseableQueue module is licensed under the permissive terms of the FreeBSD license.

See the file COPYING for details.