from __future__ import annotations import decimal import typing import typing_extensions """ MIT License  Copyright (c) 2020 Corentin Garcia  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. """ # above license is for the immutabledict class _K = typing.TypeVar("_K") _V = typing.TypeVar("_V", covariant=True) class immutabledict(typing.Mapping[_K, _V]): """  An immutable wrapper around dictionaries that implements  the complete :py:class:`collections.Mapping` interface.  It can be used as a drop-in replacement for dictionaries  where immutability is desired.   Note: custom version of this class made to remove __init__  """ dict_cls: typing.Type[typing.Dict[typing.Any, typing.Any]] = dict _dict: typing.Dict[_K, _V] _hash: typing.Optional[int] @classmethod def fromkeys( cls, seq: typing.Iterable[_K], value: typing.Optional[_V] = None ) -> "immutabledict[_K, _V]": return cls(dict.fromkeys(seq, value)) def __new__(cls, arg: typing.Dict): inst = super().__new__(cls) setattr(inst, '_dict', cls.dict_cls(arg)) setattr(inst, '_hash', None) return inst def __getitem__(self, key: _K) -> _V: return self._dict[key] def __contains__(self, key: object) -> bool: return key in self._dict def __iter__(self) -> typing.Iterator[_K]: return iter(self._dict) def __len__(self) -> int: return len(self._dict) def __repr__(self) -> str: return "%s(%r)" % (self.__class__.__name__, self._dict) def __hash__(self) -> int: if self._hash is None: h = 0 for key, value in self.items(): h ^= hash((key, value)) self._hash = h return self._hash def __or__(self, other: typing.Any) -> immutabledict[_K, _V]: if not isinstance(other, (dict, self.__class__)): return NotImplemented new = dict(self) new.update(other) return self.__class__(new) def __ror__(self, other: typing.Any) -> typing.Dict[typing.Any, typing.Any]: if not isinstance(other, (dict, self.__class__)): return NotImplemented new = dict(other) new.update(self) return new def __ior__(self, other: typing.Any) -> immutabledict[_K, _V]: raise TypeError(f"'{self.__class__.__name__}' object is not mutable") class MyDict(immutabledict[str, typing.Any]): @property def decimal(self) -> typing.Union[decimal.Decimal, None]: val = self.get("decimal") if val is None: return val return typing.cast( decimal.Decimal, val ) def __new__( cls: typing.Type[immutabledict], decimal: typing.Union[decimal.Decimal, None] = None ): arg = {} arg['decimal'] = decimal inst = super().__new__(cls, arg) return typing.cast(MyDict, inst) inst = MyDict(decimal=decimal.Decimal('3.14')) print(inst)