python小例子

for A in range(1,10):
    for B in range(0,10):
        for C in range(0,10):
            for D in range(1,10):
                if (A*1000 + B * 100 + C * 10 +D)* 9 == (D*1000 + C*100 +B*10 + A):
                    print(‘{0}{1}{2}{3}*9 == {3}{2}{1}{0}‘.format(A,B,C,D))

def fact(n):
    if n == 0:
        return 1
    return n * fact(n-1)

while True:
    result = 0
    n  = input(‘Please input number:‘)
    if not n.isdigit():
        print(‘你输入的不是纯数字，请重新输入！‘)
        continue
    for i in range(0,int(n)+1):
        result+=fact(i)
    print(result)