云函数无法写入

import string
import requests

SCKEY = '666'
url2 = 'https://api.tokyo.biliob233.com/user/check-in'
cookie2 = '666'


def it():
headers = {
'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.163 Safari/537.36', 'cookie': cookie2
}
res = requests.post(url=url2, headers=headers).text
f = open("bilibiliob.txt", 'w+')
f.write(res)
f.close()


# 微信推送
ssckey = SCKEY
send_url = 'https://sc.ftqq.com/' + ssckey + '.send'
with open('bilibiliob.txt', 'a+') as f2:
text = f2.read()
punctuation_string = string.punctuation
for i in punctuation_string:
text = text.replace(i, '')

if 'code1msg 未登录' or 'code1msg 已经签过到了' in text:
params = {
'text': 'bilibiliob 签到失败提醒'
}
else:
params = {
'text': 'bilibiliob 签到提醒'
}

requests.post(send_url, params=params)


def main_handler(event, context):
return it()


if __name__ == '__main__':
it()

程序能行了，可放在云函数上不行，请问怎么让云函数能读写文件，或者让程序不需要创建文件就能执行