python求输入一个字符串 分别统计出其中字母 数字和其他字符的个数

str = input("请输入一个字符串:")length1 = len(str)letter = 0digit = 0others = 0print(length1)i = 0for each in str:str1 = str[i]i += 1if str1.isalpha():letter += 1elif str1.isdigit():digit += 1else:others += 1print("字母有%d个，数字有%d个，其他字符有%d个" % (letter, digit, others))