A simple function to wrap a recursive function to make it memoize.

memoize.py

def memoize(F):
	# A hash table for storing previous states
	hashed_states = {}
	
	def memoized_F(*args):
		# if we haven't memoized this state, calculate
		# it. Then return it
		if args not in hashed_states:
			hashed_states[args] = F(*args)

		return hashed_states[args]
	
	return memoized_F

@memoize
def fibonacci(N):
	if N is 0 or N is 1:
		return N
	else:
		return fibonacci(N-1) + fibonacci(N-2)

print(fibonacci(100))