method-cache-max-size-none.md

Pattern: Use of lru_cache method

Issue: -

Description

By decorating a method with lru_cache the self argument will be linked to the lru_cache function and therefore is never garbage collected. Unless your instance will never need to be garbage collected (singleton) it is recommended to refactor code to avoid this pattern or add a maxsize to the cache.

Example of incorrect code:

import functools

class Fibonnaci:
    @functools.lru_cache(maxsize=None)  # [method-cache-max-size-none]
    def fibonacci(self, n):
        if n in {0, 1}:
            return n
        return self.fibonacci(n - 1) + self.fibonacci(n - 2)

Example of correct code:

import functools

@functools.cache
def cached_fibonacci(n):
    if n in {0, 1}:
        return n
    return cached_fibonacci(n - 1) + cached_fibonacci(n - 2)


class Fibonnaci:
    def fibonacci(self, n):
        return cached_fibonacci(n)