python如何输入一个整数逆序输出_PYTHON习题练习（第五弹）

a = 2.0
b = 1.0
s = 0
for i in range(1,21):
    s += a/b
    t = a
    a = a + b
    b = t
print(s)

# 求1!+2！+3!+4!+5!+...+20!
n = 0
s = 0
t = 1
for n in range(1,21):
    t *= n
    s += t
print("1!+2！+3!+4!+5!+...+20!=%d" % s)

def fact(j):
    sum1 = 0
    if j == 0:
        sum1 = 1
    else:
        sum1 = j*fact(j-1)
    return sum1


for i in range(5):
    print("%d!=%d" % (i,fact(i)))

# 给一个不多于五位的正整数，要求1.求出它是几位数；2.逆序输出各位的数字
num = int(input("请输入一个不多于五位的正整数:"))

while True:
    if num <= 0:
        num = int(input("您输入的数据有误，请重新输入："))
    else:
        a = int(num / 10000)
        b = int((num % 10000) / 1000)
        c = int((num % 1000) / 100)
        d = int((num % 100) / 10)
        e = int(num % 10)
        if a != 0:
            print("5位数，逆序输出为：%d%d%d%d%d" % (e, d, c, b, a))
        elif b != 0:
            print("4位数，逆序输出为：%d%%d%d%d" % (e, d, c, b))
        elif c != 0:
            print("3位数，逆序输出为：%d%%d%d" % (e, d, c))
        elif d != 0:
            print("2位数，逆序输出为：%d%d" % (e, d))
        else:
            print("一位数，逆序输出为:%d" % e)
        break

num = str(input("请输入一个五位的正整数:"))
for i in range(2):
    if num[i] != num[-i-1]:
        print("不是回文数")
        break

else:
    print("是回文数")