from random import randint

def generate_code (code_len):

    """

    生成确定位数的验证码

    :param code_len: 验证码长度

    :return: 由大小写英文字母和数字构成的随机验证码

    """

    all_chars='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

    last_pos=len(all_chars)-1

    code=''

    for _ in range(code_len):

        index=randint(0,last_pos)

        code+=all_chars[index]

    return  code

if __name__ == '__main__':

    print(generate_code(4))