#!/usr/bin/env python3
-from abc import ABC, abstractmethod
+# © Copyright 2021-2022, Scott Gasch
+
+"""A Persistent is just a class with a load and save method. This
+module defines the Persistent base and a decorator that can be used to
+create a persistent singleton that autoloads and autosaves."""
+
import atexit
import datetime
import enum
import functools
import logging
+from abc import ABC, abstractmethod
from typing import Any
import file_utils
return False
mtime = file_utils.get_file_mtime_as_datetime(filename)
- assert mtime
+ assert mtime is not None
now = datetime.datetime.now()
return mtime.month == now.month and mtime.day == now.day and mtime.year == now.year
return False
mtime = file_utils.get_file_mtime_as_datetime(filename)
- assert mtime
+ assert mtime is not None
now = datetime.datetime.now()
return (now - mtime).total_seconds() <= limit_seconds
self.instance = None
def __call__(self, cls: Persistent):
+ @functools.wraps(cls) # type: ignore
def _load(*args, **kwargs):
# If class has already been loaded, act like a singleton
# memory.
if self.instance is not None:
logger.debug(
- f'Returning already instantiated singleton instance of {cls.__name__}.'
+ 'Returning already instantiated singleton instance of %s.', cls.__name__
)
return self.instance
# Otherwise, try to load it from persisted state.
was_loaded = False
- logger.debug(f'Attempting to load {cls.__name__} from persisted state.')
+ logger.debug('Attempting to load %s from persisted state.', cls.__name__)
self.instance = cls.load()
if not self.instance:
msg = 'Loading from cache failed.'
logger.warning(msg)
- logger.debug(f'Attempting to instantiate {cls.__name__} directly.')
+ logger.debug('Attempting to instantiate %s directly.', cls.__name__)
self.instance = cls(*args, **kwargs)
else:
- logger.debug(
- f'Class {cls.__name__} was loaded from persisted state successfully.'
- )
+ logger.debug('Class %s was loaded from persisted state successfully.', cls.__name__)
was_loaded = True
assert self.instance is not None
if self.persist_at_shutdown is PersistAtShutdown.ALWAYS or (
- not was_loaded
- and self.persist_at_shutdown is PersistAtShutdown.IF_NOT_LOADED
+ not was_loaded and self.persist_at_shutdown is PersistAtShutdown.IF_NOT_LOADED
):
- logger.debug(
- 'Scheduling a deferred called to save at process shutdown time.'
- )
+ logger.debug('Scheduling a deferred called to save at process shutdown time.')
atexit.register(self.instance.save)
return self.instance