python - 如何使全局变量从数据库中刷新

Question

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Answer 1

使用类属性，仅在经过一段时间后才再次访问服务器。

from datetime import datetime, timedelta
import random

class MyThing(object):

    def __init__(self, refresh_interval=60*60*24):
        self.refresh_interval = refresh_interval
        self._n_users = None
        self._last_refresh = datetime.now() - timedelta(0, refresh_interval)
        # setup db connection stuff

    @property
    def n_users(self):
        if (datetime.now() - self._last_refresh).total_seconds() > self.refresh_interval:
            self._n_users = self.fetch_from_db()
            self._last_refresh = datetime.now()
        return self._n_users

    def fetch_from_db(self):
        # TODO
        return random.randint(0, 100)

t = MyThing(refresh_interval=3)
print t.n_users