254 lines
6.7 KiB
Python
254 lines
6.7 KiB
Python
"""Utilities for collecting objects based on "is" comparison."""
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# Copyright 2017 The TensorFlow Authors. All Rights Reserved.
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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 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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# ==============================================================================
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import collections
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import weakref
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# LINT.IfChange
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class _ObjectIdentityWrapper:
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"""Wraps an object, mapping __eq__ on wrapper to "is" on wrapped.
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Since __eq__ is based on object identity, it's safe to also define __hash__
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based on object ids. This lets us add unhashable types like trackable
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_ListWrapper objects to object-identity collections.
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"""
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__slots__ = ["_wrapped", "__weakref__"]
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def __init__(self, wrapped):
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self._wrapped = wrapped
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@property
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def unwrapped(self):
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return self._wrapped
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def _assert_type(self, other):
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if not isinstance(other, _ObjectIdentityWrapper):
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raise TypeError(
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"Cannot compare wrapped object with unwrapped object. "
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"Expect the object to be `_ObjectIdentityWrapper`. "
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f"Got: {other}"
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)
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def __lt__(self, other):
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self._assert_type(other)
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return id(self._wrapped) < id(other._wrapped)
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def __gt__(self, other):
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self._assert_type(other)
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return id(self._wrapped) > id(other._wrapped)
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def __eq__(self, other):
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if other is None:
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return False
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self._assert_type(other)
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return self._wrapped is other._wrapped
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def __ne__(self, other):
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return not self.__eq__(other)
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def __hash__(self):
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# Wrapper id() is also fine for weakrefs. In fact, we rely on
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# id(weakref.ref(a)) == id(weakref.ref(a)) and weakref.ref(a) is
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# weakref.ref(a) in _WeakObjectIdentityWrapper.
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return id(self._wrapped)
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def __repr__(self):
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return f"<{type(self).__name__} wrapping {self._wrapped!r}>"
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class _WeakObjectIdentityWrapper(_ObjectIdentityWrapper):
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__slots__ = ()
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def __init__(self, wrapped):
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super().__init__(weakref.ref(wrapped))
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@property
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def unwrapped(self):
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return self._wrapped()
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class Reference(_ObjectIdentityWrapper):
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"""Reference that refers an object.
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```python
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x = [1]
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y = [1]
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x_ref1 = Reference(x)
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x_ref2 = Reference(x)
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y_ref2 = Reference(y)
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print(x_ref1 == x_ref2)
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==> True
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print(x_ref1 == y)
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==> False
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```
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"""
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__slots__ = ()
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# Disabling super class' unwrapped field.
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unwrapped = property()
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def deref(self):
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"""Returns the referenced object.
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```python
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x_ref = Reference(x)
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print(x is x_ref.deref())
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==> True
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```
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"""
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return self._wrapped
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class ObjectIdentityDictionary(collections.abc.MutableMapping):
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"""A mutable mapping data structure which compares using "is".
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This is necessary because we have trackable objects (_ListWrapper) which
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have behavior identical to built-in Python lists (including being unhashable
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and comparing based on the equality of their contents by default).
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"""
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__slots__ = ["_storage"]
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def __init__(self):
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self._storage = {}
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def _wrap_key(self, key):
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return _ObjectIdentityWrapper(key)
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def __getitem__(self, key):
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return self._storage[self._wrap_key(key)]
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def __setitem__(self, key, value):
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self._storage[self._wrap_key(key)] = value
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def __delitem__(self, key):
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del self._storage[self._wrap_key(key)]
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def __len__(self):
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return len(self._storage)
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def __iter__(self):
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for key in self._storage:
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yield key.unwrapped
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def __repr__(self):
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return f"ObjectIdentityDictionary({repr(self._storage)})"
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class ObjectIdentityWeakKeyDictionary(ObjectIdentityDictionary):
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"""Like weakref.WeakKeyDictionary, but compares objects with "is"."""
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__slots__ = ["__weakref__"]
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def _wrap_key(self, key):
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return _WeakObjectIdentityWrapper(key)
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def __len__(self):
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# Iterate, discarding old weak refs
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return len(list(self._storage))
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def __iter__(self):
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keys = self._storage.keys()
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for key in keys:
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unwrapped = key.unwrapped
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if unwrapped is None:
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del self[key]
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else:
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yield unwrapped
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class ObjectIdentitySet(collections.abc.MutableSet):
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"""Like the built-in set, but compares objects with "is"."""
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__slots__ = ["_storage", "__weakref__"]
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def __init__(self, *args):
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self._storage = set(self._wrap_key(obj) for obj in list(*args))
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@staticmethod
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def _from_storage(storage):
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result = ObjectIdentitySet()
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result._storage = storage
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return result
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def _wrap_key(self, key):
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return _ObjectIdentityWrapper(key)
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def __contains__(self, key):
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return self._wrap_key(key) in self._storage
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def discard(self, key):
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self._storage.discard(self._wrap_key(key))
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def add(self, key):
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self._storage.add(self._wrap_key(key))
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def update(self, items):
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self._storage.update([self._wrap_key(item) for item in items])
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def clear(self):
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self._storage.clear()
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def intersection(self, items):
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return self._storage.intersection(
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[self._wrap_key(item) for item in items]
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)
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def difference(self, items):
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return ObjectIdentitySet._from_storage(
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self._storage.difference([self._wrap_key(item) for item in items])
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)
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def __len__(self):
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return len(self._storage)
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def __iter__(self):
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keys = list(self._storage)
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for key in keys:
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yield key.unwrapped
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class ObjectIdentityWeakSet(ObjectIdentitySet):
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"""Like weakref.WeakSet, but compares objects with "is"."""
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__slots__ = ()
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def _wrap_key(self, key):
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return _WeakObjectIdentityWrapper(key)
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def __len__(self):
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# Iterate, discarding old weak refs
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return len([_ for _ in self])
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def __iter__(self):
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keys = list(self._storage)
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for key in keys:
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unwrapped = key.unwrapped
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if unwrapped is None:
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self.discard(key)
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else:
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yield unwrapped
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# LINT.ThenChange(//tensorflow/python/util/object_identity.py)
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