bazarr/libs/bidict/_abc.py

79 lines
3.1 KiB
Python

# Copyright 2009-2024 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)
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# ← Prev: __init__.py Current: _abc.py Next: _base.py →
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"""Provide the :class:`BidirectionalMapping` abstract base class."""
from __future__ import annotations
import typing as t
from abc import abstractmethod
from ._typing import KT
from ._typing import VT
class BidirectionalMapping(t.Mapping[KT, VT]):
"""Abstract base class for bidirectional mapping types.
Extends :class:`collections.abc.Mapping` primarily by adding the
(abstract) :attr:`inverse` property,
which implementers of :class:`BidirectionalMapping`
should override to return a reference to the inverse
:class:`BidirectionalMapping` instance.
"""
__slots__ = ()
@property
@abstractmethod
def inverse(self) -> BidirectionalMapping[VT, KT]:
"""The inverse of this bidirectional mapping instance.
*See also* :attr:`bidict.BidictBase.inverse`, :attr:`bidict.BidictBase.inv`
:raises NotImplementedError: Meant to be overridden in subclasses.
"""
# The @abstractmethod decorator prevents subclasses from being instantiated unless they
# override this method. But an overriding implementation may merely return super().inverse,
# in which case this implementation is used. Raise NotImplementedError to indicate that
# subclasses must actually provide their own implementation.
raise NotImplementedError
def __inverted__(self) -> t.Iterator[tuple[VT, KT]]:
"""Get an iterator over the items in :attr:`inverse`.
This is functionally equivalent to iterating over the items in the
forward mapping and inverting each one on the fly, but this provides a
more efficient implementation: Assuming the already-inverted items
are stored in :attr:`inverse`, just return an iterator over them directly.
Providing this default implementation enables external functions,
particularly :func:`~bidict.inverted`, to use this optimized
implementation when available, instead of having to invert on the fly.
*See also* :func:`bidict.inverted`
"""
return iter(self.inverse.items())
class MutableBidirectionalMapping(BidirectionalMapping[KT, VT], t.MutableMapping[KT, VT]):
"""Abstract base class for mutable bidirectional mapping types."""
__slots__ = ()
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