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