Source code for satpy._compat

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2020 Satpy developers
# This file is part of satpy.
# satpy is free software: you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
# satpy 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 General Public License for more details.
# You should have received a copy of the GNU General Public License along with
# satpy.  If not, see <>.
"""Backports and compatibility fixes for satpy."""

from threading import RLock

_NOT_FOUND = object()

[docs] class CachedPropertyBackport: """Backport of cached_property from Python-3.8. Source: """ def __init__(self, func): # noqa self.func = func self.attrname = None self.__doc__ = func.__doc__ self.lock = RLock() def __set_name__(self, owner, name): # noqa if self.attrname is None: self.attrname = name elif name != self.attrname: raise TypeError( "Cannot assign the same cached_property to two different names " f"({self.attrname!r} and {name!r})." ) def __get__(self, instance, owner=None): # noqa if instance is None: return self if self.attrname is None: raise TypeError( "Cannot use cached_property instance without calling __set_name__ on it.") try: cache = instance.__dict__ # noqa except AttributeError: # not all objects have __dict__ (e.g. class defines slots) msg = ( f"No '__dict__' attribute on {type(instance).__name__!r} " f"instance to cache {self.attrname!r} property." ) raise TypeError(msg) from None val = cache.get(self.attrname, _NOT_FOUND) if val is _NOT_FOUND: with self.lock: # check if another thread filled cache while we awaited lock val = cache.get(self.attrname, _NOT_FOUND) if val is _NOT_FOUND: val = self.func(instance) try: cache[self.attrname] = val except TypeError: msg = ( f"The '__dict__' attribute on {type(instance).__name__!r} instance " f"does not support item assignment for caching {self.attrname!r} property." ) raise TypeError(msg) from None return val
try: from functools import cached_property # type: ignore except ImportError: # for python < 3.8 cached_property = CachedPropertyBackport # type: ignore try: from numpy.typing import ArrayLike, DTypeLike # noqa except ImportError: # numpy <1.20 from numpy import dtype as DTypeLike # noqa from numpy import ndarray as ArrayLike # noqa try: from functools import cache # type: ignore except ImportError: from functools import lru_cache as cache # noqa