回文字符串就是正反顺序读都一样
    # s=”A man, a plan, a canal: Panama”
    s = input(“请输入一个字符串:”)

    new_s = “”

    for i in s:
    if i.isalnum():
    new_s = new_s + i
    print(new_s)

    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”)
    �