What is memoization and how can I use it in Python?

Question

I just started Python and I\'ve got no idea what memoization is and how to use it. Also, may I have a simplified example?

Answer 1

Let's not forget the built-in hasattr function, for those who want to hand-craft. That way you can keep the mem cache inside the function definition (as opposed to a global).

def fact(n):
    if not hasattr(fact, 'mem'):
        fact.mem = {1: 1}
    if not n in fact.mem:
        fact.mem[n] = n * fact(n - 1)
    return fact.mem[n]