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# -*- coding: utf-8 -*-
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# Copyright 2009-2021 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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#==============================================================================
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# * Welcome to the bidict source code *
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#==============================================================================
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# Doing a code review? You'll find a "Code review nav" comment like the one
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# below at the top and bottom of the most important source files. This provides
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# a suggested initial path through the source when reviewing.
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#
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# Note: If you aren't reading this on https://github.com/jab/bidict, you may be
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# viewing an outdated version of the code. Please head to GitHub to review the
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# latest version, which contains important improvements over older versions.
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#
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# Thank you for reading and for any feedback you provide.
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# * Code review nav *
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#==============================================================================
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# ← Prev: _abc.py Current: _base.py Next: _frozenbidict.py →
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#==============================================================================
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"""Provide :class:`BidictBase`."""
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import typing as _t
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from collections import namedtuple
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from copy import copy
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from weakref import ref
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from ._abc import BidirectionalMapping
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from ._dup import ON_DUP_DEFAULT, RAISE, DROP_OLD, DROP_NEW, OnDup
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from ._exc import DuplicationError, KeyDuplicationError, ValueDuplicationError, KeyAndValueDuplicationError
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from ._iter import _iteritems_args_kw
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from ._typing import _NONE, KT, VT, OKT, OVT, IterItems, MapOrIterItems
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_WriteResult = namedtuple('_WriteResult', 'key val oldkey oldval')
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_DedupResult = namedtuple('_DedupResult', 'isdupkey isdupval invbyval fwdbykey')
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_NODUP = _DedupResult(False, False, _NONE, _NONE)
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BT = _t.TypeVar('BT', bound='BidictBase') # typevar for BidictBase.copy
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class BidictBase(BidirectionalMapping[KT, VT]):
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"""Base class implementing :class:`BidirectionalMapping`."""
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__slots__ = ['_fwdm', '_invm', '_inv', '_invweak', '__weakref__']
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#: The default :class:`~bidict.OnDup`
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#: that governs behavior when a provided item
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#: duplicates the key or value of other item(s).
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#:
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#: *See also* :ref:`basic-usage:Values Must Be Unique`, :doc:`extending`
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on_dup = ON_DUP_DEFAULT
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_fwdm_cls: _t.Type[_t.MutableMapping[KT, VT]] = dict #: class of the backing forward mapping
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_invm_cls: _t.Type[_t.MutableMapping[VT, KT]] = dict #: class of the backing inverse mapping
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#: The object used by :meth:`__repr__` for printing the contained items.
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_repr_delegate: _t.Callable = dict
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_inv: 'BidictBase[VT, KT]'
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_inv_cls: '_t.Type[BidictBase[VT, KT]]'
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def __init_subclass__(cls, **kw):
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super().__init_subclass__(**kw)
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# Compute and set _inv_cls, the inverse of this bidict class.
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if '_inv_cls' in cls.__dict__:
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return
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if cls._fwdm_cls is cls._invm_cls:
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cls._inv_cls = cls
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return
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inv_cls = type(cls.__name__ + 'Inv', cls.__bases__, {
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**cls.__dict__,
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'_inv_cls': cls,
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'_fwdm_cls': cls._invm_cls,
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'_invm_cls': cls._fwdm_cls,
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})
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cls._inv_cls = inv_cls
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@_t.overload
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def __init__(self, __arg: _t.Mapping[KT, VT], **kw: VT) -> None: ...
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@_t.overload
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def __init__(self, __arg: IterItems[KT, VT], **kw: VT) -> None: ...
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@_t.overload
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def __init__(self, **kw: VT) -> None: ...
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def __init__(self, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
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"""Make a new bidirectional dictionary.
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The signature behaves like that of :class:`dict`.
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Items passed in are added in the order they are passed,
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respecting the :attr:`on_dup` class attribute in the process.
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"""
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#: The backing :class:`~collections.abc.Mapping`
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#: storing the forward mapping data (*key* → *value*).
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self._fwdm: _t.MutableMapping[KT, VT] = self._fwdm_cls()
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#: The backing :class:`~collections.abc.Mapping`
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#: storing the inverse mapping data (*value* → *key*).
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self._invm: _t.MutableMapping[VT, KT] = self._invm_cls()
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self._init_inv()
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if args or kw:
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self._update(True, self.on_dup, *args, **kw)
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def _init_inv(self) -> None:
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# Create the inverse bidict instance via __new__, bypassing its __init__ so that its
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# _fwdm and _invm can be assigned to this bidict's _invm and _fwdm. Store it in self._inv,
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# which holds a strong reference to a bidict's inverse, if one is available.
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self._inv = inv = self._inv_cls.__new__(self._inv_cls)
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inv._fwdm = self._invm
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inv._invm = self._fwdm
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# Only give the inverse a weak reference to this bidict to avoid creating a reference cycle,
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# stored in the _invweak attribute. See also the docs in
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# :ref:`addendum:Bidict Avoids Reference Cycles`
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inv._inv = None
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inv._invweak = ref(self)
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# Since this bidict has a strong reference to its inverse already, set its _invweak to None.
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self._invweak = None
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@property
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def _isinv(self) -> bool:
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return self._inv is None
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@property
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def inverse(self) -> 'BidictBase[VT, KT]':
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"""The inverse of this bidict."""
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# Resolve and return a strong reference to the inverse bidict.
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# One may be stored in self._inv already.
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if self._inv is not None:
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return self._inv
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# Otherwise a weakref is stored in self._invweak. Try to get a strong ref from it.
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assert self._invweak is not None
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inv = self._invweak()
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if inv is not None:
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return inv
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# Refcount of referent must have dropped to zero, as in `bidict().inv.inv`. Init a new one.
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self._init_inv() # Now this bidict will retain a strong ref to its inverse.
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return self._inv
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#: Alias for :attr:`inverse`.
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inv = inverse
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def __getstate__(self) -> dict:
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"""Needed to enable pickling due to use of :attr:`__slots__` and weakrefs.
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*See also* :meth:`object.__getstate__`
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"""
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state = {}
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for cls in self.__class__.__mro__:
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slots = getattr(cls, '__slots__', ())
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for slot in slots:
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if hasattr(self, slot):
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state[slot] = getattr(self, slot)
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# weakrefs can't be pickled.
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state.pop('_invweak', None) # Added back in __setstate__ via _init_inv call.
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state.pop('__weakref__', None) # Not added back in __setstate__. Python manages this one.
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return state
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def __setstate__(self, state: dict) -> None:
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"""Implemented because use of :attr:`__slots__` would prevent unpickling otherwise.
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*See also* :meth:`object.__setstate__`
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"""
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for slot, value in state.items():
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setattr(self, slot, value)
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self._init_inv()
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def __repr__(self) -> str:
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"""See :func:`repr`."""
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clsname = self.__class__.__name__
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if not self:
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return f'{clsname}()'
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return f'{clsname}({self._repr_delegate(self.items())})'
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# The inherited Mapping.__eq__ implementation would work, but it's implemented in terms of an
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# inefficient ``dict(self.items()) == dict(other.items())`` comparison, so override it with a
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# more efficient implementation.
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def __eq__(self, other: object) -> bool:
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"""*x.__eq__(other) ⟺ x == other*
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Equivalent to *dict(x.items()) == dict(other.items())*
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but more efficient.
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Note that :meth:`bidict's __eq__() <bidict.bidict.__eq__>` implementation
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is inherited by subclasses,
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in particular by the ordered bidict subclasses,
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so even with ordered bidicts,
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:ref:`== comparison is order-insensitive <eq-order-insensitive>`.
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*See also* :meth:`bidict.FrozenOrderedBidict.equals_order_sensitive`
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"""
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if not isinstance(other, _t.Mapping) or len(self) != len(other):
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return False
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selfget = self.get
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return all(selfget(k, _NONE) == v for (k, v) in other.items()) # type: ignore [arg-type]
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def equals_order_sensitive(self, other: object) -> bool:
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"""Order-sensitive equality check.
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*See also* :ref:`eq-order-insensitive`
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"""
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# Same short-circuit as in __eq__ above. Factoring out not worth function call overhead.
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if not isinstance(other, _t.Mapping) or len(self) != len(other):
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return False
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return all(i == j for (i, j) in zip(self.items(), other.items()))
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# The following methods are mutating and so are not public. But they are implemented in this
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# non-mutable base class (rather than the mutable `bidict` subclass) because they are used here
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# during initialization (starting with the `_update` method). (Why is this? Because `__init__`
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# and `update` share a lot of the same behavior (inserting the provided items while respecting
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# `on_dup`), so it makes sense for them to share implementation too.)
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def _pop(self, key: KT) -> VT:
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val = self._fwdm.pop(key)
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del self._invm[val]
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return val
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def _put(self, key: KT, val: VT, on_dup: OnDup) -> None:
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dedup_result = self._dedup_item(key, val, on_dup)
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if dedup_result is not None:
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self._write_item(key, val, dedup_result)
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def _dedup_item(self, key: KT, val: VT, on_dup: OnDup) -> _t.Optional[_DedupResult]:
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"""Check *key* and *val* for any duplication in self.
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Handle any duplication as per the passed in *on_dup*.
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(key, val) already present is construed as a no-op, not a duplication.
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If duplication is found and the corresponding :class:`~bidict.OnDupAction` is
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:attr:`~bidict.DROP_NEW`, return None.
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If duplication is found and the corresponding :class:`~bidict.OnDupAction` is
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:attr:`~bidict.RAISE`, raise the appropriate error.
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If duplication is found and the corresponding :class:`~bidict.OnDupAction` is
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:attr:`~bidict.DROP_OLD`,
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or if no duplication is found,
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return the :class:`_DedupResult` *(isdupkey, isdupval, oldkey, oldval)*.
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"""
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fwdm = self._fwdm
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invm = self._invm
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oldval: OVT = fwdm.get(key, _NONE)
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oldkey: OKT = invm.get(val, _NONE)
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isdupkey = oldval is not _NONE
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isdupval = oldkey is not _NONE
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dedup_result = _DedupResult(isdupkey, isdupval, oldkey, oldval)
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if isdupkey and isdupval:
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if self._already_have(key, val, oldkey, oldval):
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# (key, val) duplicates an existing item -> no-op.
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return None
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# key and val each duplicate a different existing item.
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if on_dup.kv is RAISE:
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raise KeyAndValueDuplicationError(key, val)
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if on_dup.kv is DROP_NEW:
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return None
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assert on_dup.kv is DROP_OLD
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# Fall through to the return statement on the last line.
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elif isdupkey:
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if on_dup.key is RAISE:
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raise KeyDuplicationError(key)
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if on_dup.key is DROP_NEW:
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return None
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assert on_dup.key is DROP_OLD
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# Fall through to the return statement on the last line.
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elif isdupval:
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if on_dup.val is RAISE:
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raise ValueDuplicationError(val)
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if on_dup.val is DROP_NEW:
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return None
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assert on_dup.val is DROP_OLD
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# Fall through to the return statement on the last line.
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# else neither isdupkey nor isdupval.
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return dedup_result
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@staticmethod
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def _already_have(key: KT, val: VT, oldkey: OKT, oldval: OVT) -> bool:
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# Overridden by _orderedbase.OrderedBidictBase.
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isdup = oldkey == key
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assert isdup == (oldval == val), f'{key} {val} {oldkey} {oldval}'
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return isdup
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def _write_item(self, key: KT, val: VT, dedup_result: _DedupResult) -> _WriteResult:
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# Overridden by _orderedbase.OrderedBidictBase.
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isdupkey, isdupval, oldkey, oldval = dedup_result
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fwdm = self._fwdm
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invm = self._invm
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fwdm[key] = val
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invm[val] = key
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if isdupkey:
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del invm[oldval]
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if isdupval:
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del fwdm[oldkey]
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return _WriteResult(key, val, oldkey, oldval)
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def _update(self, init: bool, on_dup: OnDup, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
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# args[0] may be a generator that yields many items, so process input in a single pass.
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if not args and not kw:
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return
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can_skip_dup_check = not self and not kw and isinstance(args[0], BidirectionalMapping)
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if can_skip_dup_check:
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self._update_no_dup_check(args[0]) # type: ignore [arg-type]
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return
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can_skip_rollback = init or RAISE not in on_dup
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if can_skip_rollback:
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self._update_no_rollback(on_dup, *args, **kw)
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else:
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self._update_with_rollback(on_dup, *args, **kw)
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def _update_no_dup_check(self, other: BidirectionalMapping[KT, VT]) -> None:
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write_item = self._write_item
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for (key, val) in other.items():
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write_item(key, val, _NODUP)
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def _update_no_rollback(self, on_dup: OnDup, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
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put = self._put
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for (key, val) in _iteritems_args_kw(*args, **kw):
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put(key, val, on_dup)
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def _update_with_rollback(self, on_dup: OnDup, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
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"""Update, rolling back on failure."""
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writes: _t.List[_t.Tuple[_DedupResult, _WriteResult]] = []
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append_write = writes.append
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dedup_item = self._dedup_item
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write_item = self._write_item
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for (key, val) in _iteritems_args_kw(*args, **kw):
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try:
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dedup_result = dedup_item(key, val, on_dup)
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except DuplicationError:
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undo_write = self._undo_write
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for dedup_result, write_result in reversed(writes):
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undo_write(dedup_result, write_result)
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raise
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if dedup_result is not None:
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write_result = write_item(key, val, dedup_result)
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append_write((dedup_result, write_result))
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def _undo_write(self, dedup_result: _DedupResult, write_result: _WriteResult) -> None:
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isdupkey, isdupval, _, _ = dedup_result
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key, val, oldkey, oldval = write_result
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if not isdupkey and not isdupval:
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self._pop(key)
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return
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fwdm = self._fwdm
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invm = self._invm
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if isdupkey:
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fwdm[key] = oldval
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invm[oldval] = key
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if not isdupval:
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del invm[val]
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if isdupval:
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invm[val] = oldkey
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fwdm[oldkey] = val
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if not isdupkey:
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del fwdm[key]
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def copy(self: BT) -> BT:
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"""A shallow copy."""
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# Could just ``return self.__class__(self)`` here instead, but the below is faster. It uses
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# __new__ to create a copy instance while bypassing its __init__, which would result
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# in copying this bidict's items into the copy instance one at a time. Instead, make whole
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# copies of each of the backing mappings, and make them the backing mappings of the copy,
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# avoiding copying items one at a time.
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cp: BT = self.__class__.__new__(self.__class__)
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cp._fwdm = copy(self._fwdm)
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cp._invm = copy(self._invm)
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cp._init_inv()
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return cp
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#: Used for the copy protocol.
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#: *See also* the :mod:`copy` module
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__copy__ = copy
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def __len__(self) -> int:
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"""The number of contained items."""
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return len(self._fwdm)
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def __iter__(self) -> _t.Iterator[KT]:
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"""Iterator over the contained keys."""
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return iter(self._fwdm)
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def __getitem__(self, key: KT) -> VT:
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"""*x.__getitem__(key) ⟺ x[key]*"""
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return self._fwdm[key]
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# On Python 3.8+, dicts are reversible, so even non-Ordered bidicts can provide an efficient
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# __reversed__ implementation. (On Python < 3.8, they cannot.) Once support is dropped for
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# Python < 3.8, can remove the following if statement to provide __reversed__ unconditionally.
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if hasattr(_fwdm_cls, '__reversed__'):
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def __reversed__(self) -> _t.Iterator[KT]:
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"""Iterator over the contained keys in reverse order."""
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return reversed(self._fwdm) # type: ignore [no-any-return,call-overload]
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# Work around weakref slot with Generics bug on Python 3.6 (https://bugs.python.org/issue41451):
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BidictBase.__slots__.remove('__weakref__')
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# * Code review nav *
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#==============================================================================
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# ← Prev: _abc.py Current: _base.py Next: _frozenbidict.py →
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#==============================================================================
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