cache.py

from dataclasses import dataclass
from datetime import datetime, timedelta
from typing import Generic, TypeVar, Callable, Optional

T = TypeVar('T')


@dataclass
class Cache(Generic[T]):
    func: Callable[[], T]
    interval: timedelta
    _value: Optional[T] = None
    _last_update_time: Optional[T] = None

    def get(self) -> T:
        if self._last_update_time is None or self._now() - self._last_update_time >= self.interval:
            self.update()
        return self._value

    def update(self) -> None:
        self._value = self.func()
        self._last_update_time = self._now()

    def _now(self) -> datetime:
        return datetime.now()