# -*- coding: utf-8 -*-
# Copyright 2009-2020 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/.
#==============================================================================
# * Welcome to the bidict source code *
#==============================================================================
# Doing a code review? You'll find a "Code review nav" comment like the one
# below at the top and bottom of the most important source files. This provides
# a suggested initial path through the source when reviewing.
#
# Note: If you aren't reading this on https://github.com/jab/bidict, you may be
# viewing an outdated version of the code. Please head to GitHub to review the
# latest version, which contains important improvements over older versions.
#
# Thank you for reading and for any feedback you provide.
# * Code review nav *
#==============================================================================
# ← Prev: _abc.py Current: _base.py Next: _frozenbidict.py →
#==============================================================================
"""Provide :class:`BidictBase`."""
import typing as _t
from collections import namedtuple
from copy import copy
from weakref import ref
from ._abc import BidirectionalMapping
from ._dup import ON_DUP_DEFAULT, RAISE, DROP_OLD, DROP_NEW, OnDup
from ._exc import DuplicationError, KeyDuplicationError, ValueDuplicationError, KeyAndValueDuplicationError
from ._iter import _iteritems_args_kw
from ._typing import _NONE, KT, VT, OKT, OVT, IterItems, MapOrIterItems
_WriteResult = namedtuple('_WriteResult', 'key val oldkey oldval')
_DedupResult = namedtuple('_DedupResult', 'isdupkey isdupval invbyval fwdbykey')
_NODUP = _DedupResult(False, False, _NONE, _NONE)
BT = _t.TypeVar('BT', bound='BidictBase') # typevar for BidictBase.copy
class BidictBase(BidirectionalMapping[KT, VT]):
"""Base class implementing :class:`BidirectionalMapping`."""
__slots__ = ['_fwdm', '_invm', '_inv', '_invweak', '_hash', '__weakref__']
#: The default :class:`~bidict.OnDup`
#: that governs behavior when a provided item
#: duplicates the key or value of other item(s).
#:
#: *See also* :ref:`basic-usage:Values Must Be Unique`, :doc:`extending`
on_dup = ON_DUP_DEFAULT
_fwdm_cls = dict #: class of the backing forward mapping
_invm_cls = dict #: class of the backing inverse mapping
#: The object used by :meth:`__repr__` for printing the contained items.
_repr_delegate = dict
def __init_subclass__(cls, **kw):
super().__init_subclass__(**kw)
# Compute and set _inv_cls, the inverse of this bidict class.
if '_inv_cls' in cls.__dict__:
return
if cls._fwdm_cls is cls._invm_cls:
cls._inv_cls = cls
return
inv_cls = type(cls.__name__ + 'Inv', cls.__bases__, {
**cls.__dict__,
'_inv_cls': cls,
'_fwdm_cls': cls._invm_cls,
'_invm_cls': cls._fwdm_cls,
})
cls._inv_cls = inv_cls
@_t.overload
def __init__(self, __arg: _t.Mapping[KT, VT], **kw: VT) -> None: ...
@_t.overload
def __init__(self, __arg: IterItems[KT, VT], **kw: VT) -> None: ...
@_t.overload
def __init__(self, **kw: VT) -> None: ...
def __init__(self, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
"""Make a new bidirectional dictionary.
The signature behaves like that of :class:`dict`.
Items passed in are added in the order they are passed,
respecting the :attr:`on_dup` class attribute in the process.
"""
#: The backing :class:`~collections.abc.Mapping`
#: storing the forward mapping data (*key* → *value*).
self._fwdm: _t.Dict[KT, VT] = self._fwdm_cls()
#: The backing :class:`~collections.abc.Mapping`
#: storing the inverse mapping data (*value* → *key*).
self._invm: _t.Dict[VT, KT] = self._invm_cls()
self._init_inv()
if args or kw:
self._update(True, self.on_dup, *args, **kw)
def _init_inv(self) -> None:
# Create the inverse bidict instance via __new__, bypassing its __init__ so that its
# _fwdm and _invm can be assigned to this bidict's _invm and _fwdm. Store it in self._inv,
# which holds a strong reference to a bidict's inverse, if one is available.
self._inv = inv = self._inv_cls.__new__(self._inv_cls) # type: ignore
inv._fwdm = self._invm
inv._invm = self._fwdm
# Only give the inverse a weak reference to this bidict to avoid creating a reference cycle,
# stored in the _invweak attribute. See also the docs in
# :ref:`addendum:Bidict Avoids Reference Cycles`
inv._inv = None
inv._invweak = ref(self)
# Since this bidict has a strong reference to its inverse already, set its _invweak to None.
self._invweak = None
@property
def _isinv(self) -> bool:
return self._inv is None
@property
def inverse(self) -> 'BidictBase[VT, KT]':
"""The inverse of this bidict."""
# Resolve and return a strong reference to the inverse bidict.
# One may be stored in self._inv already.
if self._inv is not None:
return self._inv # type: ignore
# Otherwise a weakref is stored in self._invweak. Try to get a strong ref from it.
assert self._invweak is not None
inv = self._invweak()
if inv is not None:
return inv
# Refcount of referent must have dropped to zero, as in `bidict().inv.inv`. Init a new one.
self._init_inv() # Now this bidict will retain a strong ref to its inverse.
return self._inv
#: Alias for :attr:`inverse`.
inv = inverse
def __getstate__(self) -> dict:
"""Needed to enable pickling due to use of :attr:`__slots__` and weakrefs.
*See also* :meth:`object.__getstate__`
"""
state = {}
for cls in self.__class__.__mro__:
slots = getattr(cls, '__slots__', ())
for slot in slots:
if hasattr(self, slot):
state[slot] = getattr(self, slot)
# weakrefs can't be pickled.
state.pop('_invweak', None) # Added back in __setstate__ via _init_inv call.
state.pop('__weakref__', None) # Not added back in __setstate__. Python manages this one.
return state
def __setstate__(self, state: dict) -> None:
"""Implemented because use of :attr:`__slots__` would prevent unpickling otherwise.
*See also* :meth:`object.__setstate__`
"""
for slot, value in state.items():
setattr(self, slot, value)
self._init_inv()
def __repr__(self) -> str:
"""See :func:`repr`."""
clsname = self.__class__.__name__
if not self:
return f'{clsname}()'
return f'{clsname}({self._repr_delegate(self.items())})'
# The inherited Mapping.__eq__ implementation would work, but it's implemented in terms of an
# inefficient ``dict(self.items()) == dict(other.items())`` comparison, so override it with a
# more efficient implementation.
def __eq__(self, other: object) -> bool:
"""*x.__eq__(other) ⟺ x == other*
Equivalent to *dict(x.items()) == dict(other.items())*
but more efficient.
Note that :meth:`bidict's __eq__() <bidict.bidict.__eq__>` implementation
is inherited by subclasses,
in particular by the ordered bidict subclasses,
so even with ordered bidicts,
:ref:`== comparison is order-insensitive <eq-order-insensitive>`.
*See also* :meth:`bidict.FrozenOrderedBidict.equals_order_sensitive`
"""
if not isinstance(other, _t.Mapping) or len(self) != len(other):
return False
selfget = self.get
return all(selfget(k, _NONE) == v for (k, v) in other.items()) # type: ignore
# The following methods are mutating and so are not public. But they are implemented in this
# non-mutable base class (rather than the mutable `bidict` subclass) because they are used here
# during initialization (starting with the `_update` method). (Why is this? Because `__init__`
# and `update` share a lot of the same behavior (inserting the provided items while respecting
# `on_dup`), so it makes sense for them to share implementation too.)
def _pop(self, key: KT) -> VT:
val = self._fwdm.pop(key)
del self._invm[val]
return val
def _put(self, key: KT, val: VT, on_dup: OnDup) -> None:
dedup_result = self._dedup_item(key, val, on_dup)
if dedup_result is not None:
self._write_item(key, val, dedup_result)
def _dedup_item(self, key: KT, val: VT, on_dup: OnDup) -> _t.Optional[_DedupResult]:
"""Check *key* and *val* for any duplication in self.
Handle any duplication as per the passed in *on_dup*.
(key, val) already present is construed as a no-op, not a duplication.
If duplication is found and the corresponding :class:`~bidict.OnDupAction` is
:attr:`~bidict.DROP_NEW`, return None.
If duplication is found and the corresponding :class:`~bidict.OnDupAction` is
:attr:`~bidict.RAISE`, raise the appropriate error.
If duplication is found and the corresponding :class:`~bidict.OnDupAction` is
:attr:`~bidict.DROP_OLD`,
or if no duplication is found,
return the :class:`_DedupResult` *(isdupkey, isdupval, oldkey, oldval)*.
"""
fwdm = self._fwdm
invm = self._invm
oldval: OVT = fwdm.get(key, _NONE)
oldkey: OKT = invm.get(val, _NONE)
isdupkey = oldval is not _NONE
isdupval = oldkey is not _NONE
dedup_result = _DedupResult(isdupkey, isdupval, oldkey, oldval)
if isdupkey and isdupval:
if self._already_have(key, val, oldkey, oldval):
# (key, val) duplicates an existing item -> no-op.
return None
# key and val each duplicate a different existing item.
if on_dup.kv is RAISE:
raise KeyAndValueDuplicationError(key, val)
if on_dup.kv is DROP_NEW:
return None
assert on_dup.kv is DROP_OLD
# Fall through to the return statement on the last line.
elif isdupkey:
if on_dup.key is RAISE:
raise KeyDuplicationError(key)
if on_dup.key is DROP_NEW:
return None
assert on_dup.key is DROP_OLD
# Fall through to the return statement on the last line.
elif isdupval:
if on_dup.val is RAISE:
raise ValueDuplicationError(val)
if on_dup.val is DROP_NEW:
return None
assert on_dup.val is DROP_OLD
# Fall through to the return statement on the last line.
# else neither isdupkey nor isdupval.
return dedup_result
@staticmethod
def _already_have(key: KT, val: VT, oldkey: OKT, oldval: OVT) -> bool:
# Overridden by _orderedbase.OrderedBidictBase.
isdup = oldkey == key
assert isdup == (oldval == val), f'{key} {val} {oldkey} {oldval}'
return isdup
def _write_item(self, key: KT, val: VT, dedup_result: _DedupResult) -> _WriteResult:
# Overridden by _orderedbase.OrderedBidictBase.
isdupkey, isdupval, oldkey, oldval = dedup_result
fwdm = self._fwdm
invm = self._invm
fwdm[key] = val
invm[val] = key
if isdupkey:
del invm[oldval]
if isdupval:
del fwdm[oldkey]
return _WriteResult(key, val, oldkey, oldval)
def _update(self, init: bool, on_dup: OnDup, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
# args[0] may be a generator that yields many items, so process input in a single pass.
if not args and not kw:
return
can_skip_dup_check = not self and not kw and isinstance(args[0], BidirectionalMapping)
if can_skip_dup_check:
self._update_no_dup_check(args[0]) # type: ignore
return
can_skip_rollback = init or RAISE not in on_dup
if can_skip_rollback:
self._update_no_rollback(on_dup, *args, **kw)
else:
self._update_with_rollback(on_dup, *args, **kw)
def _update_no_dup_check(self, other: BidirectionalMapping[KT, VT]) -> None:
write_item = self._write_item
for (key, val) in other.items():
write_item(key, val, _NODUP)
def _update_no_rollback(self, on_dup: OnDup, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
put = self._put
for (key, val) in _iteritems_args_kw(*args, **kw):
put(key, val, on_dup)
def _update_with_rollback(self, on_dup: OnDup, *args: MapOrIterItems[KT, VT], **kw: VT) -> None:
"""Update, rolling back on failure."""
writes: _t.List[_t.Tuple[_DedupResult, _WriteResult]] = []
append_write = writes.append
dedup_item = self._dedup_item
write_item = self._write_item
for (key, val) in _iteritems_args_kw(*args, **kw):
try:
dedup_result = dedup_item(key, val, on_dup)
except DuplicationError:
undo_write = self._undo_write
for dedup_result, write_result in reversed(writes):
undo_write(dedup_result, write_result)
raise
if dedup_result is not None:
write_result = write_item(key, val, dedup_result)
append_write((dedup_result, write_result))
def _undo_write(self, dedup_result: _DedupResult, write_result: _WriteResult) -> None:
isdupkey, isdupval, _, _ = dedup_result
key, val, oldkey, oldval = write_result
if not isdupkey and not isdupval:
self._pop(key)
return
fwdm = self._fwdm
invm = self._invm
if isdupkey:
fwdm[key] = oldval
invm[oldval] = key
if not isdupval:
del invm[val]
if isdupval:
invm[val] = oldkey
fwdm[oldkey] = val
if not isdupkey:
del fwdm[key]
def copy(self: BT) -> BT:
"""A shallow copy."""
# Could just ``return self.__class__(self)`` here instead, but the below is faster. It uses
# __new__ to create a copy instance while bypassing its __init__, which would result
# in copying this bidict's items into the copy instance one at a time. Instead, make whole
# copies of each of the backing mappings, and make them the backing mappings of the copy,
# avoiding copying items one at a time.
cp = self.__class__.__new__(self.__class__)
cp._fwdm = copy(self._fwdm)
cp._invm = copy(self._invm)
cp._init_inv()
return cp # type: ignore
#: Used for the copy protocol.
#: *See also* the :mod:`copy` module
__copy__ = copy
def __len__(self) -> int:
"""The number of contained items."""
return len(self._fwdm)
def __iter__(self) -> _t.Iterator[KT]:
"""Iterator over the contained keys."""
return iter(self._fwdm)
def __getitem__(self, key: KT) -> VT:
"""*x.__getitem__(key) ⟺ x[key]*"""
return self._fwdm[key]
# Work around weakref slot with Generics bug on Python 3.6 (https://bugs.python.org/issue41451):
BidictBase.__slots__.remove('__weakref__')
# * Code review nav *
#==============================================================================
# ← Prev: _abc.py Current: _base.py Next: _frozenbidict.py →
#==============================================================================