python dict & set

dict 属于 mapping 类型

from collections.abc import Mapping, MutableMapping
#dict属于mapping类型

a = {}
print (isinstance(a, MutableMapping))

dict 抽象基类

class MutableMapping(Mapping):

    __slots__ = ()

    """A MutableMapping is a generic container for associating
    key/value pairs.

    This class provides concrete generic implementations of all
    methods except for __getitem__, __setitem__, __delitem__,
    __iter__, and __len__.

    """

    @abstractmethod
    def __setitem__(self, key, value):
        raise KeyError

    @abstractmethod
    def __delitem__(self, key):
        raise KeyError

    __marker = object()

    def pop(self, key, default=__marker):
        '''D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
          If key is not found, d is returned if given, otherwise KeyError is raised.
        '''
        try:
            value = self[key]
        except KeyError:
            if default is self.__marker:
                raise
            return default
        else:
            del self[key]
            return value

    def popitem(self):
        '''D.popitem() -> (k, v), remove and return some (key, value) pair
           as a 2-tuple; but raise KeyError if D is empty.
        '''
        try:
            key = next(iter(self))
        except StopIteration:
            raise KeyError from None
        value = self[key]
        del self[key]
        return key, value

    def clear(self):
        'D.clear() -> None.  Remove all items from D.'
        try:
            while True:
                self.popitem()
        except KeyError:
            pass

    def update(self, other=(), /, **kwds):
        ''' D.update([E, ]**F) -> None.  Update D from mapping/iterable E and F.
            If E present and has a .keys() method, does:     for k in E: D[k] = E[k]
            If E present and lacks .keys() method, does:     for (k, v) in E: D[k] = v
            In either case, this is followed by: for k, v in F.items(): D[k] = v
        '''
        if isinstance(other, Mapping):
            for key in other:
                self[key] = other[key]
        elif hasattr(other, "keys"):
            for key in other.keys():
                self[key] = other[key]
        else:
            for key, value in other:
                self[key] = value
        for key, value in kwds.items():
            self[key] = value

    def setdefault(self, key, default=None):
        'D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D'
        try:
            return self[key]
        except KeyError:
            self[key] = default
        return default

class Mapping(Collection):

    __slots__ = ()

    """A Mapping is a generic container for associating key/value
    pairs.

    This class provides concrete generic implementations of all
    methods except for __getitem__, __iter__, and __len__.

    """

    @abstractmethod
    def __getitem__(self, key):
        raise KeyError

    def get(self, key, default=None):
        'D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.'
        try:
            return self[key]
        except KeyError:
            return default

    def __contains__(self, key):
        try:
            self[key]
        except KeyError:
            return False
        else:
            return True

    def keys(self):
        "D.keys() -> a set-like object providing a view on D's keys"
        return KeysView(self)

    def items(self):
        "D.items() -> a set-like object providing a view on D's items"
        return ItemsView(self)

    def values(self):
        "D.values() -> an object providing a view on D's values"
        return ValuesView(self)

    def __eq__(self, other):
        if not isinstance(other, Mapping):
            return NotImplemented
        return dict(self.items()) == dict(other.items())

    __reversed__ = None

dict 实现的方法

class dict(MutableMapping[_KT, _VT], Generic[_KT, _VT]):
    @overload
    def __init__(self: dict[_KT, _VT]) -> None: ...
    @overload
    def __init__(self: dict[str, _VT], **kwargs: _VT) -> None: ...
    @overload
    def __init__(self, map: SupportsKeysAndGetItem[_KT, _VT], **kwargs: _VT) -> None: ...
    @overload
    def __init__(self, iterable: Iterable[Tuple[_KT, _VT]], **kwargs: _VT) -> None: ...
    def __new__(cls: Type[_T1], *args: Any, **kwargs: Any) -> _T1: ...
    def clear(self) -> None: ...
    def copy(self) -> dict[_KT, _VT]: ...
    def popitem(self) -> Tuple[_KT, _VT]: ...
    def setdefault(self, __key: _KT, __default: _VT = ...) -> _VT: ...
    @overload
    def update(self, __m: Mapping[_KT, _VT], **kwargs: _VT) -> None: ...
    @overload
    def update(self, __m: Iterable[Tuple[_KT, _VT]], **kwargs: _VT) -> None: ...
    @overload
    def update(self, **kwargs: _VT) -> None: ...
    def keys(self) -> KeysView[_KT]: ...
    def values(self) -> ValuesView[_VT]: ...
    def items(self) -> ItemsView[_KT, _VT]: ...
    @classmethod
    @overload
    def fromkeys(cls, __iterable: Iterable[_T], __value: None = ...) -> dict[_T, Any | None]: ...
    @classmethod
    @overload
    def fromkeys(cls, __iterable: Iterable[_T], __value: _S) -> dict[_T, _S]: ...
    def __len__(self) -> int: ...
    def __getitem__(self, k: _KT) -> _VT: ...
    def __setitem__(self, k: _KT, v: _VT) -> None: ...
    def __delitem__(self, v: _KT) -> None: ...
    def __iter__(self) -> Iterator[_KT]: ...
    if sys.version_info >= (3, 8):
        def __reversed__(self) -> Iterator[_KT]: ...
    def __str__(self) -> str: ...
    __hash__: None  # type: ignore
    if sys.version_info >= (3, 9):
        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
        def __or__(self, __value: Mapping[_T1, _T2]) -> dict[_KT | _T1, _VT | _T2]: ...
        def __ror__(self, __value: Mapping[_T1, _T2]) -> dict[_KT | _T1, _VT | _T2]: ...
        def __ior__(self, __value: Mapping[_KT, _VT]) -> dict[_KT, _VT]: ...  # type: ignore

不建议直接继承 dict，如果有必要继承 collections 里的 user dict

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