Skip to main content
Help us improve PyPI by participating in user testing. All experience levels needed!

An Dict like LRU container.

Project description

LRU Dict

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.

Usage

This can be used to build a LRU cache. Usage is almost like a dict.

from lru import LRU
l = LRU(5)         # Create an LRU container that can hold 5 items

print l.peek_first_item(), l.peek_last_item()  #return the MRU key and LRU key
# Would print None None

for i in range(5):
   l[i] = str(i)
print l.items()    # Prints items in MRU order
# Would print [(4, '4'), (3, '3'), (2, '2'), (1, '1'), (0, '0')]

print l.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 item
print l.items()
# Would print [(5, '5'), (4, '4'), (3, '3'), (2, '2'), (1, '1')]

l[3]               # Accessing an item would make it MRU
print l.items()
# Would print [(3, '3'), (5, '5'), (4, '4'), (2, '2'), (1, '1')]
# Now 3 is in front

l.keys()           # Can get keys alone in MRU order
# Would print [3, 5, 4, 2, 1]

del l[4]           # Delete an item
print l.items()
# Would print [(3, '3'), (5, '5'), (2, '2'), (1, '1')]

print l.get_size()
# Would print 5

l.set_size(3)
print l.items()
# Would print [(3, '3'), (5, '5'), (2, '2')]
print l.get_size()
# Would print 3
print l.has_key(5)
# Would print True
print 2 in l
# Would print True

l.get_stats()
# Would print (1, 0)


l.update(5='0')           # Update an item
print l.items()
# Would print [(5, '0'), (3, '3'), (2, '2')]

l.clear()
print l.items()
# Would print []

def evicted(key, value):
  print "removing: %s, %s" % (key, value)

l = LRU(1, callback=evicted)

l[1] = '1'
l[2] = '2'
# callback would print removing: 1, 1

l[2] = '3'
# doesn't call the evicted callback

print l.items()
# would print [(2, '3')]

del l[2]
# doesn't call the evicted callback

print l.items()
# would print []

Install

pip install lru-dict

or

easy_install lru_dict

When to use this

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

Project details


Release history Release notifications

This version
History Node

1.1.6

History Node

1.1.5

History Node

1.1.4

History Node

1.1.3

History Node

1.1.2

History Node

1.1.1

History Node

1.1

History Node

1.0

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, size & hash SHA256 hash help File type Python version Upload date
lru-dict-1.1.6.tar.gz (9.4 kB) Copy SHA256 hash SHA256 Source None Dec 10, 2016

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging CloudAMQP CloudAMQP RabbitMQ AWS AWS Cloud computing Fastly Fastly CDN DigiCert DigiCert EV certificate StatusPage StatusPage Status page