reslot 0.10

Class decorator to enable @cached_property on classes with __slots__

reslot

A class decorator that lets you use @cached_property on classes with __slots__.

The decorated class needs a __dict__ slot, but there won't exactly be a dictionary in it. Instead, @reslot will give it a custom MutableMapping with its own slots. @cached_property will keep its cache there.

The custom MutableMapping's slots will be exactly the slots needed to store the results of every @cached_property that was on the class at the time it was declared. This minimizes the memory footprint and makes lookup speedy.

Usage

from functools import cached_property

from reslot import reslot

BEANED = False

@reslot
class Spam:
    __slots__ = ("__dict__",)

    @cached_property
    def eggs(self):
        return {"delicious": False}

    @cached_property
    def beans(self):
        global BEANED
        BEANED = True
        return {"spam": 111000, "delicious": True}

spam = Spam()
print(spam.eggs)   # {"delicious": False}
print(BEANED)      # False
print(spam.beans)  # {"spam": 111000, "delicious": True}
print(BEANED)      # True