Python - factorial with cache

import time

cache = {}

def factorial(x):
    if x in cache:
        return cache[x]

    if x > 1:
        value = x * factorial(x-1)
    elif x > -1:
        value = 1
    else:
        print('Wrong number')
        exit(1)

    cache[x] = value
    return value

start = time.time()
result = factorial(980)
end = time.time()
print(end - start) # 0.002 second

start = time.time()
result = factorial(980)
end = time.time()
print(end - start) # 0.000002 second (2.0e-06)