#!/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 warnings
import file_utils
and implement their save() and load() methods.
"""
+
@abstractmethod
def save(self) -> bool:
"""
return False
mtime = file_utils.get_file_mtime_as_datetime(filename)
+ 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 mtime.month == now.month and mtime.day == now.day and mtime.year == now.year
def was_file_written_within_n_seconds(
- filename: str,
- limit_seconds: int,
+ filename: str,
+ limit_seconds: int,
) -> bool:
"""Returns True if filename was written within the pas limit_seconds
seconds.
return False
mtime = file_utils.get_file_mtime_as_datetime(filename)
+ assert mtime is not None
now = datetime.datetime.now()
return (now - mtime).total_seconds() <= limit_seconds
to disk. See details below.
"""
- NEVER = 0,
- IF_NOT_LOADED = 1,
- ALWAYS = 2,
+
+ NEVER = (0,)
+ IF_NOT_LOADED = (1,)
+ ALWAYS = (2,)
class persistent_autoloaded_singleton(object):
implementation.
"""
+
def __init__(
- self,
- *,
- persist_at_shutdown: PersistAtShutdown = PersistAtShutdown.IF_NOT_LOADED):
+ self,
+ *,
+ persist_at_shutdown: PersistAtShutdown = PersistAtShutdown.IF_NOT_LOADED,
+ ):
self.persist_at_shutdown = persist_at_shutdown
self.instance = None
def __call__(self, cls: Persistent):
- @functools.wraps(cls)
+ @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)
- warnings.warn(msg, stacklevel=2)
- 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
- )
+ if self.persist_at_shutdown is PersistAtShutdown.ALWAYS or (
+ 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.')
atexit.register(self.instance.save)
return self.instance
+
return _load