openmmtools.cache.LRUCache

class openmmtools.cache.LRUCache(capacity=None, time_to_live=None)

A simple LRU cache with a dictionary-like interface that supports maximum capacity and expiration.

It can be configured to have a maximum number of elements (capacity) and an element expiration (time_to_live) measured in number of accesses to the cache. Both read and write operations count as an access, but only successful reads (i.e. those not raising KeyError) increment the counter.

Parameters

capacityint, optional

Maximum number of elements in the cache. When set to None, the cache has infinite capacity (default is None).

time_to_liveint, optional

If an element is not accessed after time_to_live read/write operations, the element is removed. When set to None, elements do not have an expiration (default is None).

Examples

>>> cache = LRUCache(capacity=2, time_to_live=3)

When the capacity is exceeded, the least recently used element is removed.

>>> cache['1'] = 1
>>> cache['2'] = 2
>>> elem = cache['1']  # read '1', now '2' is the least recently used
>>> cache['3'] = 3
>>> len(cache)
2
>>> '2' in cache
False

After time_to_live read/write operations an element is deleted if it is not used.

>>> elem = cache['3']  # '3' is used, counter is reset
>>> elem = cache['1']  # access 1
>>> elem = cache['1']  # access 2
>>> elem = cache['1']  # access 3
>>> len(cache)
1
>>> '3' in cache
False

Attributes

capacity

Maximum number of elements that can be cached.

time_to_live

Number of read/write operations before an cached element expires.

Methods

empty()

Purge the cache.

__init__(capacity=None, time_to_live=None)

Methods

__init__([capacity, time_to_live])
empty()	Purge the cache.

Attributes

capacity	Maximum number of elements that can be cached.
time_to_live	Number of read/write operations before an cached element expires.