答案:方法一: str = input("请输入一个字符串:") for s in str : num = ord(s) #ord()把字符串转为ASCII码 if num 57 and num 122 : print("该字符串包含大写字母或者是符号!") break print("该字符串由小写字母和数字组成") 方法二: str = input("请输入一个字符串:") n = 0 slist=['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','0','1','2','3','4','5','6','7','8','9'] for s in str : if s not in slist : print("该字符串包含大写字母或者是符号!") break else: n = n 1 if n == len(str): print("该字符串由小写字母和数字组成") 方法三: import re str = input("请输入一个字符串:") if re.macth('^[0-9a-z] $',str): print("该字符串包含大写字母或者是符号!") else: print("该字符串由小写字母和数字组成")