You can install from pypi using pip or easy_install:

easy_install lru

Usage:

>>> from lru import LRUCache
>>> cache = LRUCache(max_items=2)
>>> cache['foo'] = 1
>>> cache['bar'] = 10
>>> cache['baz'] = 100 # `foo` is removed
>>> cache['bar']
10
>>> cache['foo']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/2.6/site-packages/lru.py", line 18, in __getitem__
    raise KeyError, key
KeyError: 'foo'

A KeyError is raised if the key is requested but does not exist, just like a dictionary.