けいさんしつりょう

質問:
1つの数の素因数の個数を計算し、1は素因数ではない.例えば20=2*2*5、2、2、5は20の3つの素因数です.
考え方:
小さい時から大きい時まで、Nの因数Mを探し当てて、再帰的にMとN/Mの素因数を探します.

def count_prime(number, expr):  
    count = 0  
    for i in range(2, number/2 + 1):  
        if number%i == 0:  
            (count_i, epxr) = count_prime(i, expr)  
            if count_i == 0:  
                expr += "%s * "%i  
                count += 1  
            else:  
                count += count_i  
            left = number/i  
            (count_left, expr) = count_prime(left, expr)  
            if count_left == 0:  
                expr += "%s * "%left  
                count += 1  
            else:  
                count += count_left  
            break  
    return (count, expr)  
  
number = input("input a number: ")  
(count, expr) = count_prime(number, "")  
print("There are %d primes for %d"%(count, number))  
print("expr is %s"%expr[:-3])