Note: This project is stable and production ready, but looking for a lead maintainer. Preferably someone who uses this library and made contributions to it.
A fixed size dict like container which evicts Least Recently Used (LRU) items once size limit is exceeded. There are many python implementations available which does similar things. This is a fast and efficient C implementation. LRU maximum capacity can be modified at run-time. If you are looking for pure python version, look else where.
This can be used to build a LRU cache. Usage is almost like a dict.
fromlruimportLRUl=LRU(5) # Create an LRU container that can hold 5 itemsprintl.peek_first_item(), l.peek_last_item() #return the MRU key and LRU key# Would print None Noneforiinrange(5):
l[i] =str(i)
printl.items() # Prints items in MRU order# Would print [(4, '4'), (3, '3'), (2, '2'), (1, '1'), (0, '0')]printl.peek_first_item(), l.peek_last_item() #return the MRU key and LRU key# Would print (4, '4') (0, '0')l[5] ='5'# Inserting one more item should evict the old itemprintl.items()
# Would print [(5, '5'), (4, '4'), (3, '3'), (2, '2'), (1, '1')]l[3] # Accessing an item would make it MRUprintl.items()
# Would print [(3, '3'), (5, '5'), (4, '4'), (2, '2'), (1, '1')]# Now 3 is in frontl.keys() # Can get keys alone in MRU order# Would print [3, 5, 4, 2, 1]dell[4] # Delete an itemprintl.items()
# Would print [(3, '3'), (5, '5'), (2, '2'), (1, '1')]printl.get_size()
# Would print 5l.set_size(3)
printl.items()
# Would print [(3, '3'), (5, '5'), (2, '2')]printl.get_size()
# Would print 3printl.has_key(5)
# Would print Trueprint2inl# Would print Truel.get_stats()
# Would print (1, 0)l.update(5='0') # Update an itemprintl.items()
# Would print [(5, '0'), (3, '3'), (2, '2')]l.clear()
printl.items()
# Would print []defevicted(key, value):
print"removing: %s, %s"% (key, value)
l=LRU(1, callback=evicted)
l[1] ='1'l[2] ='2'# callback would print removing: 1, 1l[2] ='3'# doesn't call the evicted callbackprintl.items()
# would print [(2, '3')]dell[2]
# doesn't call the evicted callbackprintl.items()
# would print []pip install lru-dict
or
easy_install lru_dict
Like mentioned above there are many python implementations of an LRU. Use this if you need a faster and memory efficient alternative. It is implemented with a dict and associated linked list to keep track of LRU order. See code for a more detailed explanation. To see an indicative comparison with a pure python module, consider a benchmark against pylru (just chosen at random, it should be similar with other python implementations as well).
$ python bench.py pylru.lrucache Time : 3.31 s, Memory : 453672 Kb $ python bench.py lru.LRU Time : 0.23 s, Memory : 124328 Kb