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bazarr/libs/bidict/_frozenbidict.py
2022-11-07 13:08:27 -05:00

45 lines
1.8 KiB
Python

# Copyright 2009-2022 Joshua Bronson. All rights reserved.
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
# * Code review nav *
# (see comments in __init__.py)
#==============================================================================
# ← Prev: _base.py Current: _frozenbidict.py Next: _bidict.py →
#==============================================================================
"""Provide :class:`frozenbidict`, an immutable, hashable bidirectional mapping type."""
import typing as t
from ._base import BidictBase
from ._typing import KT, VT
class frozenbidict(BidictBase[KT, VT]):
"""Immutable, hashable bidict type."""
_hash: int
# Work around lack of support for higher-kinded types in Python.
# Ref: https://github.com/python/typing/issues/548#issuecomment-621571821
if t.TYPE_CHECKING:
@property
def inverse(self) -> 'frozenbidict[VT, KT]': ...
def __hash__(self) -> int:
"""The hash of this bidict as determined by its items."""
if getattr(self, '_hash', None) is None:
# The following is like hash(frozenset(self.items()))
# but more memory efficient. See also: https://bugs.python.org/issue46684
self._hash = t.ItemsView(self)._hash() # type: ignore [attr-defined] # https://github.com/python/typeshed/pull/7153
return self._hash
# * Code review nav *
#==============================================================================
# ← Prev: _base.py Current: _frozenbidict.py Next: _bidict.py →
#==============================================================================