Queuelib is a collection of persistent (disk-based) queues for Python.

Queuelib goals are speed and simplicity. It was originally part of the Scrapy framework and stripped out on its own library.

Note: Queuelib isn't thread-safe.

• Python 2.7 or Python 3.3
• no external library requirements

You can install Queuelib either via the Python Package Index (PyPI) or from source.

To install using pip:

$ pip install queuelib

To install using easy_install:

$ easy_install queuelib

If you have downloaded a source tarball you can install it by running the following (as root):

# python setup.py install

Queuelib provides FIFO and LIFO queue implementations.

Here is an example usage of the FIFO queue:

>>> from queuelib import FifoDiskQueue
>>> q = FifoDiskQueue("queuefile")
>>> q.push(b'a')
>>> q.push(b'b')
>>> q.push(b'c')
>>> q.pop()
b'a'
>>> q.close()
>>> q = FifoDiskQueue("queuefile")
>>> q.pop()
b'b'
>>> q.pop()
b'c'
>>> q.pop()
>>>

The LIFO queue is identical (API-wise), but importing LifoDiskQueue instead.

A discrete-priority queue implemented by combining multiple FIFO/LIFO queues (one per priority).

First, select the type of queue to be used per priority (FIFO or LIFO):

>>> from queuelib import FifoDiskQueue
>>> qfactory = lambda priority: FifoDiskQueue('queue-dir-%s' % priority)

Then instantiate the Priority Queue with it:

>>> from queuelib import PriorityQueue
>>> pq = PriorityQueue(qfactory)

And use it:

>>> pq.push(b'a', 3)
>>> pq.push(b'b', 1)
>>> pq.push(b'c', 2)
>>> pq.push(b'd', 2)
>>> pq.pop()
b'b'
>>> pq.pop()
b'c'
>>> pq.pop()
b'd'
>>> pq.pop()
b'a'

Has nearly the same interface and implementation as a Priority Queue except that each element must be pushed with a (mandatory) key. Popping from the queue cycles through the keys "round robin".

Instantiate the Round Robin Queue similarly to the Priority Queue:

>>> from queuelib import RoundRobinQueue
>>> rr = RoundRobinQueue(qfactory)

And use it:

>>> rr.push(b'a', '1')
>>> rr.push(b'b', '1')
>>> rr.push(b'c', '2')
>>> rr.push(b'd', '2')
>>> rr.pop()
b'a'
>>> rr.pop()
b'c'
>>> rr.pop()
b'b'
>>> rr.pop()
b'd'

Use the scrapy-users mailing list for questions about Queuelib.

If you have any suggestions, bug reports or annoyances please report them to our issue tracker at: http://github.com/scrapy/queuelib/issues/

Development of Queuelib happens at GitHub: http://github.com/scrapy/queuelib

You are highly encouraged to participate in the development. If you don't like GitHub (for some reason) you're welcome to send regular patches.

All changes require tests to be merged.

Tests are located in queuelib/tests directory. They can be run using nosetests with the following command:

nosetests

The output should be something like the following:

$ nosetests
.............................................................................
----------------------------------------------------------------------
Ran 77 tests in 0.145s

OK

This software is licensed under the BSD License. See the LICENSE file in the top distribution directory for the full license text.

This software follows Semantic Versioning