验证输入的字符串是否为回文字符串

写法1(me)：

while True:
    s = input("请输入字符串")
    l = list(s)
    new_z = ''
    new_f = ''
    for i in range(len(l)):
        if l[i].isalnum():
            new_z = l[i] + new_z
    for i in range(len(l)):
        new_s1 = l.pop()
        if new_s1.isalnum():
            new_f = new_s1 + new_f
    if new_f == new_z:
        print("就是回文字符串")
    else:
        print("不是回文字符串")


写法2：

while True:
    s = input("请输入一个字符串:")
    new_s = ""
    for i in s:
        if i.isalnum():
            new_s = new_s + i

    new_s = new_s.lower()

    if new_s == new_s[::-1]:
        print("这个字符串是回文字符串")
    else:
        print("这个字符串不是回文字符串")