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Memoization in Python in One Line

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I had a bit of a surprise today while going through some Python exercises. I needed to add memoization to a function and I had it all written with custom code. Then I decided to see if there was a more pythony way of solving the problem and I was very surprised by the answer.

One line of code

Okay, technically it is two lines of code if you count the import statement.

from functools import lru_cache
[...]

@lru_cache(maxsize = 1024) # <-- built-in memoization in one line
def my_function(self, x, y):
  return x + y

Add the lru_cache decorator and your function is wrapped with memoization functionality. You can use maxsize to control how big the cache is – use maxsize=None and the cache is unbounded. Additionally, the decoration provides information about the cache (hits, misses, size). I’m impressed.

Here is the documentation for lru_cache.

As a side note, LRU stands for Least Recently Used.

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