59 lines
1.6 KiB
Python
59 lines
1.6 KiB
Python
# Copyright 2018 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import functools
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def has_upb():
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try:
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from google._upb import _message # pylint: disable=unused-import
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has_upb = True
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except ImportError:
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has_upb = False
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return has_upb
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def cached_property(fx):
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"""Make the callable into a cached property.
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Similar to @property, but the function will only be called once per
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object.
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Args:
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fx (Callable[]): The property function.
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Returns:
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Callable[]: The wrapped function.
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"""
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@functools.wraps(fx)
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def inner(self):
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# Sanity check: If there is no cache at all, create an empty cache.
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if not hasattr(self, "_cached_values"):
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object.__setattr__(self, "_cached_values", {})
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# If and only if the function's result is not in the cache,
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# run the function.
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if fx.__name__ not in self._cached_values:
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self._cached_values[fx.__name__] = fx(self)
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# Return the value from cache.
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return self._cached_values[fx.__name__]
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return property(inner)
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__all__ = ("cached_property",)
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