随机验证码

主要chr()内置函数，与之相关的函数是ord()

import random
li = list()
for i in range(4):
    ret = random.randrange(65,91)
    j = random.randrange(1,5)
    if j == 3 or j == 5:
        ret = random.randrange(0,10)
    else:
        ret = chr(ret)
    li.append(str(ret))
    code = ''.join(li)
print(code)