from threading import Timer

import random

class Code:

    def __init__(self):

        self.make_cache()

    def make_cache(self,interval =15):#生成的验证码保存在cache里，过15s重新生成验证码，更新cache

        self.cache = self.make_code()

        print(self.cache)

        self.t = Timer(interval,self.make_cache)

        self.t.start()

    def make_code(self,n=4):

        res = ''

        for i in range(n):

            s1= str(random.randint(0,9))

            s2=chr(random.randint(65,90))

            res += random.choice([s1,s2])

        return res

    def check(self):

        while True:

            code = input('请输入验证码>>:').strip()

            if code.upper() == self.cache:

                print('验证码正确')

                self.t.cancel()

                break

obj=Code()

obj.check()