求各数位上的数字之和
法一：

def func(num):
    sum = 0
    while num!=0:
        n = num%10
        sum += n
        num = num//10
    return sum
print(func(12345))

法二：

def func(num):
    a = str(num)
    b = 0
    for i in a:
        b+=int(i)
    return b
print(func(12345))