69 lines
1.9 KiB
Python
69 lines
1.9 KiB
Python
# Copyright (c) 2013 Red Hat, Inc.
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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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# http://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
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# 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 cached_getattr(meth):
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"""Caches attributes returned by __getattr__
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It can be used to cache results from
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__getattr__ and reduce the debt of calling
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it again when the same attribute is accessed.
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This decorator caches attributes by setting
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them in the object itself.
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The wrapper returned by this decorator won't alter
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the returned value.
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:returns: A wrapper around the decorated method.
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"""
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@functools.wraps(meth)
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def wrapper(self, method_name):
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attr = meth(self, method_name)
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setattr(self, method_name, attr)
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return attr
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return wrapper
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def lazy_property(write=False, delete=True):
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"""Creates a lazy property.
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:param write: Whether this property is "writable"
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:param delete: Whether this property can be deleted.
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"""
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def wrapper(fn):
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attr_name = '_lazy_' + fn.__name__
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def getter(self):
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if not hasattr(self, attr_name):
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setattr(self, attr_name, fn(self))
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return getattr(self, attr_name)
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def setter(self, value):
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setattr(self, attr_name, value)
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def deleter(self):
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delattr(self, attr_name)
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return property(fget=getter,
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fset=write and setter,
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fdel=delete and deleter,
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doc=fn.__doc__)
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return wrapper
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