Python 3.9+functoolsfunction

functools.cache

functools

Decorator for a simple unbounded cache (like lru_cache(maxsize=None)); added in 3.9.

Syntax

@functools.cache

cache never evicts anything: the dictionary keeps growing for as long as the function lives, so it is riskier than a bounded lru_cache on user-supplied input — and on methods it also keeps a reference to self alive. In exchange it is slightly faster, since there is no recency bookkeeping or eviction. Arguments must be hashable; a list or dict raises TypeError.

Examples

import functools
@functools.cache
def f(n):
    return n + 1
print(f(10), f(10))   # → 11 11

See also

Common errors

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