python-lru 0.2.1

LRU Cache Implementation

python-lru

Least Recently Used (LRU) Cache implementation

Usage

Instantiate a cache collection object specifying storage parameters. The cache object itself is thread safe. However, depending on the storage backend, it may not be safe to open a cache store multiple times.

from lru import LRUCache, ItemNotCached

# Open cache store (all arguments are optional)
cache = LRUCache(
    storage = MemoryStorage() or ShelvedStorage(path=''),
    max_size = 1000000,
    sizeof = lambda o: len(str(o)),
    max_age = timedelta(minutes=15))

# Add items with keys
cache['name'] = "Bob"
cache['age'] = 12

# Check for items in cache
try:
    age = cache['age']
except ItemNotCached:
    print("No age")

Cache Objects

Cached data can be any variable, and must be cached using a string key. It's up to you to ensure that you don't mutate objects returned from the cache, as storage won't automatically update from changes.

Cache Parameters

The LRUCache container parameters are:

• storage: Where to store cached data. See Storages.
• sizeof: Callable to estimate the size of an object being cached.
• max_size: Maximum size before starting to forget cached items.
• max_age: All cached items will expire after this amount of time.
• storage: Object to use to store cached data

Storages

There are a few storage classes provided. All are inherited from CacheStorage

• MemoryStorage: Caches data in memory
• ShelvedStorage: Caches data in shelve. Really only useful if you're caching large objects.
• Sqlite3Storage: Slowest storage engine, but possibly accessible from multiple processes?