94 lines
3.2 KiB
Python
94 lines
3.2 KiB
Python
# Copyright 2021 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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"""A set based on dict so that it preserves key insertion order.
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Python Dicts are order-preserving since 3.6
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(https://mail.python.org/pipermail/python-dev/2017-December/151283.html),
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but sets are not. This class implements a set on top of a dict so that we get
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deterministic iteration order across runs.
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"""
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import collections.abc
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class OrderPreservingSet(collections.abc.MutableSet):
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"""A set based on dict so that it preserves key insertion order."""
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def __init__(self, iterable=None):
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self._dict = {item: None for item in (iterable or [])}
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# abstract from collections.MutableSet
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def __len__(self):
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return len(self._dict)
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# abstract from collections.MutableSet
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def __contains__(self, value):
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return value in self._dict
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# override from collections.MutableSet
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def __iter__(self):
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return iter(self._dict)
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# abstract from collections.MutableSet
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def add(self, item):
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self._dict[item] = None
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# abstract from collections.MutableSet
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def discard(self, value):
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del self._dict[value]
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# override from collections.MutableSet
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def clear(self):
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self._dict = {}
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# override from collections.Set
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def __eq__(self, other):
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if not isinstance(other, OrderPreservingSet):
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return NotImplemented
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return self._dict.keys() == other._dict.keys()
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# override from collections.Set
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def __le__(self, other):
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if not isinstance(other, OrderPreservingSet):
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return NotImplemented
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return self._dict.keys() <= other._dict.keys()
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# override from collections.Set
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def __ge__(self, other):
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if not isinstance(other, OrderPreservingSet):
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return NotImplemented
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return self._dict.keys() >= other._dict.keys()
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# override from collections.Set
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def __and__(self, other):
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# collections.Set defaults to the ordering in other, we want to use self
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return self._from_iterable(value for value in self if value in other)
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# override from collections.Set
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def __or__(self, other):
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# ensure that other is ordered before performing __or__
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if not isinstance(other, OrderPreservingSet):
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raise TypeError(
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"cannot union an 'OrderPreservingSet' with an "
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"unordered iterable."
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)
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result = self._from_iterable(value for value in self)
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for value in other:
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result._dict[value] = None
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return result
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def union(self, other):
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return self | other
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