案例：验证码

# 案例：验证码
import random
def v_code():
    ret = ''
    for i in range(4):
        num = random.randint(0, 9)    #随机数字
        char = chr(random.randint(65, 122))  #随机A-z
        s = str(random.choice([num, char]))
        ret += s
    return ret


print(v_code())