Memoize decorator in Python

Memoization trades memory for speed - standard for expensive pure functions.

def memoize(fn):
    cache = {}

    def wrapper(*args):
        if args not in cache:
            cache[args] = fn(*args)
        return cache[args]

    return wrapper

How it works

1. Wraps a function in a decorator.
2. A dict caches each result, keyed by the call's arguments.
3. Repeat calls with the same arguments return the cached value instantly.

Keywords and builtins used here

• def
• if
• memoize
• return
• wrapper

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Step 4 of 5 in Decorators & closures, step 8 of 53 in Pythonic Python.

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