Memoization in Python

[Alec Mihailovs]

Following Antti Karttunen suggestion, I wrote the following simple decorator 
for creating functions with cache (something like 'option remember' in 
Maple). Just wanted to share it:

def function_with_cache(f):
    def new_f(*args):
        if args in new_f.cache: return new_f.cache[args]
        result=f(*args)
        new_f.cache[args]=result
        return result
    new_f.cache={}
    new_f.func_name=f.func_name
    return new_f

For example,

@function_with_cache
def A000045(n):
    if n<2: return n
    return A000045(n-1)+A000045(n-2)

A000045(3)
2

A000045.cache
{(2,): 1, (0,): 0, (3,): 2, (1,): 1}

Or, another example,

@function_with_cache
def binomial(m,n):
    if m <0 or n >m: return 0
    if n==0 or m==n: return 1
    return binomial(m-1,n)+binomial(m-1,n-1)

binomial(5,3)
10

binomial.cache
{(3, 2): 3, (3, 3): 1, (3, 1): 3, (2, 1): 2, (2, 0): 1, (4, 3): 4, (2, 2):
1, (4, 2): 6, (1, 0): 1, (1, 1): 1, (5, 3): 10}

Alec Mihailovs
http://mihailovs.com/Alec/