Project Euler#20 Factorial digit sum

#n! means n × (n − 1) × ... × 3 × 2 × 1

#For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,
#and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.

#Find the sum of the digits in the number 100!

def fact(n):
    if n == 1:
        return n
    return n*fact(n-1)

digitsString = str(fact(100))
print digitsString
acc = 0

for i in range(len(digitsString)):
    acc = acc + int(digitsString[i])

print acc