#!/usr/bin/env python
#
# frozenordereddict.py
"""
Provides FrozenOrderedDict, an immutable ordered dictionary.
"""
#
# Copyright © 2020 Dominic Davis-Foster <dominic@davis-foster.co.uk>
# Copyright © 2015 Warren Smith
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
# MA 02110-1301, USA.
#
# stdlib
import operator
from collections import OrderedDict
from functools import reduce
from typing import AbstractSet, Optional, Tuple, TypeVar, Union, ValuesView, overload
# this package
from .base import KT, VT, FrozenBase
__all__ = ["FrozenOrderedDict"]
T = TypeVar('T')
class FrozenOrderedDict(FrozenBase[KT, VT]):
"""
An immutable OrderedDict.
It can be used as a drop-in replacement for dictionaries where immutability is desired.
"""
dict_cls = OrderedDict
def __init__(self, *args, **kwargs):
if hasattr(self, "_dict"):
raise TypeError(f"`{self.__class__}` can only be initialised once.")
super().__init__(*args, **kwargs)
def copy(self, *args, **kwargs):
"""
Return a copy of the :class:`~cawdrey.frozenordereddict.FrozenOrderedDict`.
:param args:
:param kwargs:
"""
new_dict = self._dict.copy()
if args or kwargs:
new_dict.update(OrderedDict(*args, **kwargs))
return self.__class__(new_dict)
def __hash__(self) -> int:
"""
Return :func:`hash(self) <hash>`.
"""
if self._hash is None:
self._hash = reduce(operator.xor, map(hash, self.items()), 0)
return self._hash
@overload
def get(self, k: KT) -> Optional[VT]: ... # pragma: no cover
@overload
def get(self, k: KT, default: Union[VT, T]) -> Union[VT, T]: ... # pragma: no cover
def get(self, k, default=None):
"""
Return the value for ``k`` if ``k`` is in the dictionary, else ``default``.
:param k: The key to return the value for.
:param default: The value to return if ``key`` is not in the dictionary.
"""
return super().get(k, default)
def items(self) -> AbstractSet[Tuple[KT, VT]]:
r"""
Returns a set-like object providing a view on the :class:`~.FrozenOrderedDict`\'s items.
"""
return super().items()
def keys(self) -> AbstractSet[KT]:
r"""
Returns a set-like object providing a view on the :class:`~.FrozenOrderedDict`\'s keys.
"""
return super().keys()
def values(self) -> ValuesView[VT]:
r"""
Returns an object providing a view on the :class:`~.FrozenOrderedDict`\'s values.
"""
return super().values()
def __contains__(self, key: object) -> bool:
"""
Return ``key in self``.
:param key:
"""
return super().__contains__(key)
def __getitem__(self, key: KT) -> VT:
"""
Return ``self[key]``.
:param key:
"""
return super().__getitem__(key)