Source code for bidict._frozenordered

# -*- coding: utf-8 -*-
# Copyright 2009-2020 Joshua Bronson. All Rights Reserved.
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"""Provides :class:`FrozenOrderedBidict`, an immutable, hashable, ordered bidict."""

from ._frozenbidict import frozenbidict
from ._orderedbase import OrderedBidictBase
from .compat import DICTS_ORDERED


class FrozenOrderedBidict(OrderedBidictBase):
    """Hashable, immutable, ordered bidict type."""

    __slots__ = ()
    __hash__ = frozenbidict.__hash__

    # If the Python implementation's dict type is ordered (e.g. PyPy or CPython >= 3.6), then we can
    # delegate to `_fwdm` and `_invm` for faster implementations of several methods. Both `_fwdm`
    # and `_invm` will always be initialized with the provided items in the correct order, and since
    # `FrozenOrderedBidict` is immutable, their respective orders can't get out of sync after a
    # mutation.
    if DICTS_ORDERED:
        def __iter__(self, reverse=False):  # noqa: N802
            """Iterator over the contained keys in insertion order."""
            if reverse:
                return super().__iter__(reverse=True)
            return iter(self._fwdm._fwdm)  # pylint: disable=protected-access

        def keys(self):
            """A set-like object providing a view on the contained keys."""
            return self._fwdm._fwdm.keys()  # pylint: disable=protected-access

        def values(self):
            """A set-like object providing a view on the contained values."""
            return self._invm._fwdm.keys()  # pylint: disable=protected-access

        # We can't delegate for items because values in `_fwdm` are nodes.


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