lru_cache
- @lru_cache(user_function)
- @lru_cache(maxsize=128, typed=False)
Least-recently-used cache decorator.
If *maxsize* is set to None, the LRU features are disabled and the cache
can grow without bound.
If *typed* is True, arguments of different types will be cached
separately. For example, f(decimal.Decimal("3.0")) and f(3.0) will be
treated as distinct calls with distinct results. Some types such as
str and int may be cached separately even when typed is false.
Arguments to the cached function must be hashable.
View the cache statistics named tuple (hits, misses, maxsize, currsize)
with f.cache_info(). Clear the cache and statistics with
f.cache_clear(). Access the underlying function with f.__wrapped__.
See: https://en.wikipedia.org/wiki/Cache_replacement_policies#Least_recently_used_(LRU)© Python Software Foundation. PSF License Version 2 · Official docs ↗
Changed in 3.3, 3.8, 3.9
- 3.3: Added the typed option.
- 3.8: Added the user_function option.
- 3.9: Added the function cache_parameters()
Members of lru_cache
c
- cache_clear
- The decorator also provides a cache_clear() function for clearing or invalidating the cache.
- cache_info
- To help measure the effectiveness of the cache and tune the maxsize parameter, the wrapped function is instrumented with a cache_info() function that returns a named tuple showing hits, misses, maxsi…
1 Example
@lru_cache(maxsize=32) def get_pep(num): 'Retrieve text of a Python Enhancement Proposal' resource = f'https://peps.python.org/pep-{num:04d}' try: with urllib.request.urlopen(resource) as s: return s.read() except urllib.error.HTTPError: return 'Not Found' >>> for n in 8, 290, 308, 320, 8, 218, 320, 279, 289, 320, 9991: ... pep = get_pep(n) ... print(n, len(pep)) >>> get_pep.cache_info() CacheInfo(hits=3, misses=8, maxsize=32, currsize=8)
from the Python docs