memo = {}

def helper(x):

if x not in memo:

memo[x] = f(x)

return memo[x]

return helper

memoize

if n == 0:

return 0

elif n == 1:

return 1

else:

return fib(n-1) + fib(n-2)

fib

Executing:

fib = memoize(fib) helper is returned

if x not in memo:

memo[x] = f(x)

return memo[x]