练习题：

1.验证码：0-9，a-zA-Z

        def check_yzm():
        
            str_yzm=''
            for i in range(4):
                num1 = random.randrange(0, 6)
                if num1 == 1 or num1 == 3:
                    num2 = random.randrange(0, 10)
                    str_yzm += str(num2)
        
                elif num1 == 2 or num1 == 4:
                    num3 = random.randrange(97, 123)
                    str2 = chr(num3)
                    str_yzm += str(str2)
        
                else:
                    num4 = random.randrange(65, 91)
                    str1 = chr(num4)
                    str_yzm += str(str1)
            return str_yzm
        
        yzm = check_yzm()
        print(yzm)

2 写函数，计算传入字符串中【数字】、【字母】、【空格] 以及 【其他】的个数

def count_str(str):
    num_count = 0
    letter_count = 0
    space_count = 0
    others_count = 0
    for each_str in str :
        if each_str.isdigit():
            num_count += 1
        elif each_str.isalpha():
            letter_count += 1
        elif each_str.isspace():
            space_count += 1
        else:
            others_count += 1
    return '数字个数为：{num_count}，字母个位数为：{letter_count}，空格个数为：{space_count},其他的个数为:{others_count}'.format(num_count=num_count,letter_count=letter_count,space_count= space_count,others_count=others_count)


str1 = "123    ***qwe"
result = count_str(str1)
print(result)