Source code for bidict._orderedbase

# 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

#                             * Code review nav *
#                        (see comments in
# ============================================================================
# ← Prev:      Current:   Next: →
# ============================================================================

"""Provide :class:`OrderedBidictBase`."""

from __future__ import annotations

import typing as t
from weakref import ref as weakref

from ._base import BidictBase
from ._base import Unwrites
from ._bidict import bidict
from ._iter import iteritems
from ._typing import KT
from ._typing import MISSING
from ._typing import OKT
from ._typing import OVT
from ._typing import VT
from ._typing import MapOrItems

AT = t.TypeVar('AT')  # attr type

class WeakAttr(t.Generic[AT]):
    """Descriptor to automatically manage (de)referencing the given slot as a weakref.

    for an intro to using descriptors like this for managed attributes.

    def __init__(self, *, slot: str) -> None:
        self.slot = slot

    def __set__(self, instance: t.Any, value: AT) -> None:
        setattr(instance, self.slot, weakref(value))

    def __get__(self, instance: t.Any, __owner: t.Any = None) -> AT:
        return t.cast(AT, getattr(instance, self.slot)())

class Node:
    """A node in a circular doubly-linked list
    used to encode the order of items in an ordered bidict.

    A weak reference to the previous node is stored
    to avoid creating strong reference cycles.
    Referencing/dereferencing the weakref is handled automatically by :class:`WeakAttr`.

    prv: WeakAttr[Node] = WeakAttr(slot='_prv_weak')
    __slots__ = ('__weakref__', '_prv_weak', 'nxt')

    nxt: Node | WeakAttr[Node]  # Allow subclasses to use a WeakAttr for nxt too (see SentinelNode)

    def __init__(self, prv: Node, nxt: Node) -> None:
        self.prv = prv
        self.nxt = nxt

    def unlink(self) -> None:
        """Remove self from in between prv and nxt.
        Self's references to prv and nxt are retained so it can be relinked (see below).
        self.prv.nxt = self.nxt
        self.nxt.prv = self.prv

    def relink(self) -> None:
        """Restore self between prv and nxt after unlinking (see above)."""
        self.prv.nxt = self.nxt.prv = self

class SentinelNode(Node):
    """Special node in a circular doubly-linked list
    that links the first node with the last node.
    When its next and previous references point back to itself
    it represents an empty list.

    nxt: WeakAttr[Node] = WeakAttr(slot='_nxt_weak')
    __slots__ = ('_nxt_weak',)

    def __init__(self) -> None:
        super().__init__(self, self)

    def iternodes(self, *, reverse: bool = False) -> t.Iterator[Node]:
        """Iterator yielding nodes in the requested order."""
        attr = 'prv' if reverse else 'nxt'
        node = getattr(self, attr)
        while node is not self:
            yield node
            node = getattr(node, attr)

    def new_last_node(self) -> Node:
        """Create and return a new terminal node."""
        old_last = self.prv
        new_last = Node(old_last, self)
        old_last.nxt = self.prv = new_last
        return new_last

class OrderedBidictBase(BidictBase[KT, VT]):
    """Base class implementing an ordered :class:`BidirectionalMapping`."""

    _node_by_korv: bidict[t.Any, Node]
    _bykey: bool

[docs] def __init__(self, arg: MapOrItems[KT, VT] = (), /, **kw: VT) -> None: """Make a new ordered bidirectional mapping. The signature behaves like that of :class:`dict`. Items passed in are added in the order they are passed, respecting the :attr:`~bidict.BidictBase.on_dup` class attribute in the process. The order in which items are inserted is remembered, similar to :class:`collections.OrderedDict`. """ self._sntl = SentinelNode() self._node_by_korv = bidict() self._bykey = True super().__init__(arg, **kw)
if t.TYPE_CHECKING: @property def inverse(self) -> OrderedBidictBase[VT, KT]: ... @property def inv(self) -> OrderedBidictBase[VT, KT]: ... def _make_inverse(self) -> OrderedBidictBase[VT, KT]: inv = t.cast(OrderedBidictBase[VT, KT], super()._make_inverse()) inv._sntl = self._sntl inv._node_by_korv = self._node_by_korv inv._bykey = not self._bykey return inv def _assoc_node(self, node: Node, key: KT, val: VT) -> None: korv = key if self._bykey else val self._node_by_korv.forceput(korv, node) def _dissoc_node(self, node: Node) -> None: del self._node_by_korv.inverse[node] node.unlink() def _init_from(self, other: MapOrItems[KT, VT]) -> None: """See :meth:`BidictBase._init_from`.""" super()._init_from(other) bykey = self._bykey korv_by_node = self._node_by_korv.inverse korv_by_node.clear() korv_by_node_set = korv_by_node.__setitem__ self._sntl.nxt = self._sntl.prv = self._sntl new_node = self._sntl.new_last_node for k, v in iteritems(other): korv_by_node_set(new_node(), k if bykey else v) def _write(self, newkey: KT, newval: VT, oldkey: OKT[KT], oldval: OVT[VT], unwrites: Unwrites | None) -> None: """See :meth:`bidict.BidictBase._spec_write`.""" super()._write(newkey, newval, oldkey, oldval, unwrites) assoc, dissoc = self._assoc_node, self._dissoc_node node_by_korv, bykey = self._node_by_korv, self._bykey if oldval is MISSING and oldkey is MISSING: # no key or value duplication # {0: 1, 2: 3} | {4: 5} => {0: 1, 2: 3, 4: 5} newnode = self._sntl.new_last_node() assoc(newnode, newkey, newval) if unwrites is not None: unwrites.append((dissoc, newnode)) elif oldval is not MISSING and oldkey is not MISSING: # key and value duplication across two different items # {0: 1, 2: 3} | {0: 3} => {0: 3} # n1, n2 => n1 (collapse n1 and n2 into n1) # oldkey: 2, oldval: 1, oldnode: n2, newkey: 0, newval: 3, newnode: n1 if bykey: oldnode = node_by_korv[oldkey] newnode = node_by_korv[newkey] else: oldnode = node_by_korv[newval] newnode = node_by_korv[oldval] dissoc(oldnode) assoc(newnode, newkey, newval) if unwrites is not None: unwrites.extend(( (assoc, newnode, newkey, oldval), (assoc, oldnode, oldkey, newval), (oldnode.relink,), )) elif oldval is not MISSING: # just key duplication # {0: 1, 2: 3} | {2: 4} => {0: 1, 2: 4} # oldkey: MISSING, oldval: 3, newkey: 2, newval: 4 node = node_by_korv[newkey if bykey else oldval] assoc(node, newkey, newval) if unwrites is not None: unwrites.append((assoc, node, newkey, oldval)) else: assert oldkey is not MISSING # just value duplication # {0: 1, 2: 3} | {4: 3} => {0: 1, 4: 3} # oldkey: 2, oldval: MISSING, newkey: 4, newval: 3 node = node_by_korv[oldkey if bykey else newval] assoc(node, newkey, newval) if unwrites is not None: unwrites.append((assoc, node, oldkey, newval))
[docs] def __iter__(self) -> t.Iterator[KT]: """Iterator over the contained keys in insertion order.""" return self._iter(reverse=False)
[docs] def __reversed__(self) -> t.Iterator[KT]: """Iterator over the contained keys in reverse insertion order.""" return self._iter(reverse=True)
def _iter(self, *, reverse: bool = False) -> t.Iterator[KT]: nodes = self._sntl.iternodes(reverse=reverse) korv_by_node = self._node_by_korv.inverse if self._bykey: for node in nodes: yield korv_by_node[node] else: key_by_val = self._invm for node in nodes: val = korv_by_node[node] yield key_by_val[val] # * Code review nav * # ============================================================================ # ← Prev: Current: Next: → # ============================================================================