随机验证码模块（random）

1. 生成一个6位数字+字母的验证码 (面试题)

import random

l = []
for i in range(6):
    alpha = chr(random.randint(65,90))
    alpha_lower = chr(random.randint(97,122))
    num = str(random.randint(0,9))
    ret = random.choice([alpha,num,alpha_lower])
    l.append(ret)
print(''.join(l))