A fixed size set in python.

This is a simple data structure that supports adding/removing elements as well as checking the set for membership.

Currently all that's supported is add, remove, __contains__, and __iter__.

There is currently no plans to support creating new sets from existing LRUSets (union, intersection, difference, etc.)

Example usage:

>>> import clruset
>>> s = clruset.LRUSet(max_size=5)
>>> for i in range(5): s.add(i)
...
>>> len(s)
5
>>> s.add(100)
>>> len(s)
5
>>> 0 in s
False

Once the max_size is reached, the LRU element is evicted. In the example above, this is 0, and 0 is shown to no longer be in the set. This behavior also applies to checking for membership:

>>> import clruset
>>> s = clruset.LRUSet(max_size=5)
>>> for i in range(5): s.add(i)
...
>>> 0 in s
True
>>> 1 in s
True
>>> # 2 is now the LRU so adding a new element will evict it.
...
>>> s.add(100)
>>> 2 in s
False

Iteration is in LRU order where the first element is the LRU element:

>>> import clruset
>>> s = clruset.LRUSet(max_size=5)
>>> for i in range(5): s.add(i)
...
>>> s.add(100)
>>> s.add(200)
>>> print list(iter(s))
[2, 3, 4, 100, 200]
>>> s.add('new')
>>> print list(iter(s))
[3, 4, 100, 200, 'new']

There's two implementations of LRUSet, a pure python verion (lruset.LRUSet), and a C version (clruset.LRUSet).