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46 lines
1.8 KiB
46 lines
1.8 KiB
# Copyright 2009-2022 Joshua Bronson. All rights reserved. |
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# |
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# This Source Code Form is subject to the terms of the Mozilla Public |
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# License, v. 2.0. If a copy of the MPL was not distributed with this |
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# file, You can obtain one at http://mozilla.org/MPL/2.0/. |
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# * Code review nav * |
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# (see comments in __init__.py) |
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#============================================================================== |
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# ← Prev: _base.py Current: _frozenbidict.py Next: _bidict.py → |
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#============================================================================== |
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"""Provide :class:`frozenbidict`, an immutable, hashable bidirectional mapping type.""" |
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from __future__ import annotations |
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import typing as t |
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from ._base import BidictBase |
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from ._typing import KT, VT |
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class frozenbidict(BidictBase[KT, VT]): |
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"""Immutable, hashable bidict type.""" |
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_hash: int |
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# Work around lack of support for higher-kinded types in Python. |
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# Ref: https://github.com/python/typing/issues/548#issuecomment-621571821 |
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if t.TYPE_CHECKING: |
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@property |
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def inverse(self) -> frozenbidict[VT, KT]: ... |
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def __hash__(self) -> int: |
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"""The hash of this bidict as determined by its items.""" |
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if getattr(self, '_hash', None) is None: |
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# The following is like hash(frozenset(self.items())) |
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# but more memory efficient. See also: https://bugs.python.org/issue46684 |
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self._hash = t.ItemsView(self)._hash() |
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return self._hash |
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# * Code review nav * |
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#============================================================================== |
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# ← Prev: _base.py Current: _frozenbidict.py Next: _bidict.py → |
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#==============================================================================
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