46 lines
1.8 KiB
Python
46 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."""
|
|
|
|
from __future__ import annotations
|
|
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()
|
|
return self._hash
|
|
|
|
|
|
# * Code review nav *
|
|
#==============================================================================
|
|
# ← Prev: _base.py Current: _frozenbidict.py Next: _bidict.py →
|
|
#==============================================================================
|