python生成随机验证码

import random
def get_code(num=5):
    lis1 = ['1','2','3','4','5','6','7','8','9']
    for i in range(65, 90):
        lis1.append(chr(i))
    for i in range(97, 122):
        lis1.append(chr(i))
    l2 = random.sample(lis1,num)
    return ''.join(l2)