pocketpy/docs/modules/functools.md

---

icon: package

label: functools

functools

Helpers for caching calls, reducing a sequence, and pre-filling arguments.

API	Behavior
@cache	Cache results without a size limit.
@lru_cache(maxsize=128)	Keep up to maxsize recently used argument tuples.
reduce(function, sequence, initial=...)	Combine items from left to right. An empty sequence needs an initial value.
partial(function, *args, **kwargs)	Store arguments for later calls.

Cache a computation

from functools import lru_cache, reduce

@lru_cache(maxsize=32)
def fibonacci(n):
    if n < 2:
        return n
    return fibonacci(n - 1) + fibonacci(n - 2)

assert fibonacci(10) == 55
assert reduce(lambda total, value: total + value, [1, 2, 3], 0) == 6

The cache decorators accept positional calls only, with hashable arguments. Use a positive integer maxsize; the implementation does not support CPython's maxsize=None, zero-size mode, typed, or cache_info()/ cache_clear() methods. Cached mutable results are returned as the same object on later calls.

Partial calls

from functools import partial

def label(name, prefix='item'):
    return prefix + ': ' + name

enemy_label = partial(label, prefix='enemy')
assert enemy_label('slime') == 'enemy: slime'
assert enemy_label('slime', prefix='boss') == 'enemy: slime'

Stored positional arguments are prepended to new ones. Stored keyword arguments override keywords passed at call time in this implementation. This differs from CPython, where call-time keywords win.

Implementation: functools.py.