# 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)
# ============================================================================
# ← Prev: _orderedbase.py Current: _orderedbidict.py <FIN>
# ============================================================================
"""Provide :class:`OrderedBidict`."""
from __future__ import annotations
import typing as t
from collections.abc import Set
from ._base import BidictKeysView
from ._bidict import MutableBidict
from ._orderedbase import OrderedBidictBase
from ._typing import KT
from ._typing import VT
class OrderedBidict(OrderedBidictBase[KT, VT], MutableBidict[KT, VT]):
"""Mutable bidict type that maintains items in insertion order."""
if t.TYPE_CHECKING:
@property
def inverse(self) -> OrderedBidict[VT, KT]: ...
@property
def inv(self) -> OrderedBidict[VT, KT]: ...
[docs]
def clear(self) -> None:
"""Remove all items."""
super().clear()
self._node_by_korv.clear()
self._sntl.nxt = self._sntl.prv = self._sntl
def _pop(self, key: KT) -> VT:
val = super()._pop(key)
node = self._node_by_korv[key if self._bykey else val]
self._dissoc_node(node)
return val
[docs]
def popitem(self, last: bool = True) -> tuple[KT, VT]:
"""*b.popitem() → (k, v)*
If *last* is true,
remove and return the most recently added item as a (key, value) pair.
Otherwise, remove and return the least recently added item.
:raises KeyError: if *b* is empty.
"""
if not self:
raise KeyError('OrderedBidict is empty')
node = getattr(self._sntl, 'prv' if last else 'nxt')
korv = self._node_by_korv.inverse[node]
if self._bykey:
return korv, self._pop(korv)
return self.inverse._pop(korv), korv
[docs]
def move_to_end(self, key: KT, last: bool = True) -> None:
"""Move the item with the given key to the end if *last* is true, else to the beginning.
:raises KeyError: if *key* is missing
"""
korv = key if self._bykey else self._fwdm[key]
node = self._node_by_korv[korv]
node.prv.nxt = node.nxt
node.nxt.prv = node.prv
sntl = self._sntl
if last:
lastnode = sntl.prv
node.prv = lastnode
node.nxt = sntl
sntl.prv = lastnode.nxt = node
else:
firstnode = sntl.nxt
node.prv = sntl
node.nxt = firstnode
sntl.nxt = firstnode.prv = node
# Override the keys() and items() implementations inherited from BidictBase,
# which may delegate to the backing _fwdm dict, since this is a mutable ordered bidict,
# and therefore the ordering of items can get out of sync with the backing mappings
# after mutation. (Need not override values() because it delegates to .inverse.keys().)
[docs]
def keys(self) -> t.KeysView[KT]:
"""A set-like object providing a view on the contained keys."""
return _OrderedBidictKeysView(self)
[docs]
def items(self) -> t.ItemsView[KT, VT]:
"""A set-like object providing a view on the contained items."""
return _OrderedBidictItemsView(self)
# The following MappingView implementations use the __iter__ implementations
# inherited from their superclass counterparts in collections.abc, so they
# continue to yield items in the correct order even after an OrderedBidict
# is mutated. They also provide a __reversed__ implementation, which is not
# provided by the collections.abc superclasses.
class _OrderedBidictKeysView(BidictKeysView[KT]):
_mapping: OrderedBidict[KT, t.Any]
def __reversed__(self) -> t.Iterator[KT]:
return reversed(self._mapping)
class _OrderedBidictItemsView(t.ItemsView[KT, VT]):
_mapping: OrderedBidict[KT, VT]
def __reversed__(self) -> t.Iterator[tuple[KT, VT]]:
ob = self._mapping
for key in reversed(ob):
yield key, ob[key]
# For better performance, make _OrderedBidictKeysView and _OrderedBidictItemsView delegate
# to backing dicts for the methods they inherit from collections.abc.Set. (Cannot delegate
# for __iter__ and __reversed__ since they are order-sensitive.) See also: https://bugs.python.org/issue46713
_OView = t.Union[t.Type[_OrderedBidictKeysView[KT]], t.Type[_OrderedBidictItemsView[KT, t.Any]]]
_setmethodnames: t.Iterable[str] = (
'__lt__ __le__ __gt__ __ge__ __eq__ __ne__ __sub__ __rsub__ '
'__or__ __ror__ __xor__ __rxor__ __and__ __rand__ isdisjoint'
).split()
def _override_set_methods_to_use_backing_dict(cls: _OView[KT], viewname: str) -> None:
def make_proxy_method(methodname: str) -> t.Any:
def method(self: _OrderedBidictKeysView[KT] | _OrderedBidictItemsView[KT, t.Any], *args: t.Any) -> t.Any:
fwdm = self._mapping._fwdm
if not isinstance(fwdm, dict): # dict view speedup not available, fall back to Set's implementation.
return getattr(Set, methodname)(self, *args)
fwdm_dict_view = getattr(fwdm, viewname)()
fwdm_dict_view_method = getattr(fwdm_dict_view, methodname)
if (
len(args) != 1
or not isinstance((arg := args[0]), self.__class__)
or not isinstance(arg._mapping._fwdm, dict)
):
return fwdm_dict_view_method(*args)
# self and arg are both _OrderedBidictKeysViews or _OrderedBidictItemsViews whose bidicts are backed by
# a dict. Use arg's backing dict's corresponding view instead of arg. Otherwise, e.g. `ob1.keys()
# < ob2.keys()` would give "TypeError: '<' not supported between instances of '_OrderedBidictKeysView' and
# '_OrderedBidictKeysView'", because both `dict_keys(ob1).__lt__(ob2.keys()) is NotImplemented` and
# `dict_keys(ob2).__gt__(ob1.keys()) is NotImplemented`.
arg_dict = arg._mapping._fwdm
arg_dict_view = getattr(arg_dict, viewname)()
return fwdm_dict_view_method(arg_dict_view)
method.__name__ = methodname
method.__qualname__ = f'{cls.__qualname__}.{methodname}'
return method
for name in _setmethodnames:
setattr(cls, name, make_proxy_method(name))
_override_set_methods_to_use_backing_dict(_OrderedBidictKeysView, 'keys')
_override_set_methods_to_use_backing_dict(_OrderedBidictItemsView, 'items')
# * Code review nav *
# ============================================================================
# ← Prev: _orderedbase.py Current: _orderedbidict.py <FIN>
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