Source code for apeye.cache

#!/usr/bin/env python3
#
#  cache.py
"""
Caching functions for functions.

.. latex:vspace:: 10px

.. seealso::

	* The `cachier project <https://pypi.org/project/cachier/>`_
	* `DiskCache <http://www.grantjenks.com/docs/diskcache/index.html>`_

.. automodulesumm:: apeye.cache
	:autosummary-sections: ;;
"""
#
#  Copyright (c) 2020 Dominic Davis-Foster <dominic@davis-foster.co.uk>
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU Lesser General Public License as published by
#  the Free Software Foundation; either version 3 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
#  GNU Lesser General Public License for more details.
#
#  You should have received a copy of the GNU Lesser General Public License
#  along with this program; if not, write to the Free Software
#  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
#  MA 02110-1301, USA.
#

# stdlib
import inspect
import json
import shutil
import warnings
from functools import wraps
from typing import Any, Callable, Dict, Iterable, Optional

# 3rd party
import platformdirs
from domdf_python_tools.paths import PathPlus
from domdf_python_tools.utils import posargs2kwargs

__all__ = ["Cache"]


[docs]class Cache: """ Cache function arguments to and in-memory dictionary and a JSON file. :param app_name: The name of the app. This dictates the name of the cache directory. """ app_name: str #: The name of the app. This dictates the name of the cache directory. cache_dir: PathPlus #: The location of the cache directory on disk. caches: Dict[str, Dict[str, Any]] #: Mapping of function names to their caches. def __init__(self, app_name: str): self.app_name: str = str(app_name) self.cache_dir = PathPlus(platformdirs.user_cache_dir(f"{self.app_name}_cache")) self.cache_dir.maybe_make(parents=True) # Mapping of function names to their caches self.caches: Dict[str, Dict[str, Any]] = {}
[docs] def clear(self, func: Optional[Callable] = None) -> bool: """ Clear the cache. :param func: Optional function to clear the cache for. By default, the whole cache is cleared. :no-default func: :returns: True to indicate success. False otherwise. """ try: if func is None: shutil.rmtree(self.cache_dir) self.cache_dir.maybe_make() for function in self.caches: self.caches[function] = {} else: function_name = func.__name__ cache_file = self.cache_dir / f"{function_name}.json" if cache_file.is_file(): cache_file.unlink() if function_name in self.caches: del self.caches[function_name] self.caches[function_name] = {} return True except Exception as e: # pragma: no cover warnings.warn(f"Could not remove cache. The error was: {e}") return False
[docs] def load_cache(self, func: Callable) -> None: """ Loads the cache for the given function. :param func: """ cache_file: PathPlus = self.cache_dir / f"{func.__name__}.json" if cache_file.is_file(): cache = json.loads(cache_file.read_text()) else: cache = {} self.caches[func.__name__] = cache return cache
[docs] def __call__(self, func: Callable): """ Decorator to cache the return values of a function based on its inputs. :param func: """ function_name = func.__name__ posargs: Iterable[str] = inspect.getfullargspec(func).args cache_file: PathPlus = self.cache_dir / f"{function_name}.json" self.load_cache(func) @wraps(func) def wrapper(*args, **kwargs: Any): kwargs = posargs2kwargs(args, posargs, kwargs) key: str = json.dumps(kwargs) response: Any cache = self.caches[function_name] if key in cache: # Return cached response response = json.loads(cache[key]) else: response = func(**kwargs) if response is not None: # Don't cache None values. cache[key] = json.dumps(response) cache_file.write_text(json.dumps(cache)) return response return wrapper