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Pythonhttps://blog.csdn.net/weixin_45791458/category_12403403.html?spm=1001.2014.3001.5482

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        在python中，一切数据类型都是对象（即类的实例），包括整数、浮点数、字符串、列表、元组、集合、字典、复数、布尔、函数、自定义类等，它们都是根据相应的类创建的。

        python内建类的定义可以在库文件/stdlib/builtins.pyi中找到，下面的例1示例性地给出了整数类型的定义。

# 例1
class int:@overloaddef __new__(cls, x: ConvertibleToInt = ..., /) -> Self: ...@overloaddef __new__(cls, x: str | bytes | bytearray, /, base: SupportsIndex) -> Self: ...def as_integer_ratio(self) -> tuple[int, Literal[1]]: ...@propertydef real(self) -> int: ...@propertydef imag(self) -> Literal[0]: ...@propertydef numerator(self) -> int: ...@propertydef denominator(self) -> Literal[1]: ...def conjugate(self) -> int: ...def bit_length(self) -> int: ...if sys.version_info >= (3, 10):def bit_count(self) -> int: ...if sys.version_info >= (3, 11):def to_bytes(self, length: SupportsIndex = 1, byteorder: Literal["little", "big"] = "big", *, signed: bool = False) -> bytes: ...@classmethoddef from_bytes(cls,bytes: Iterable[SupportsIndex] | SupportsBytes | ReadableBuffer,byteorder: Literal["little", "big"] = "big",*,signed: bool = False,) -> Self: ...else:def to_bytes(self, length: SupportsIndex, byteorder: Literal["little", "big"], *, signed: bool = False) -> bytes: ...@classmethoddef from_bytes(cls,bytes: Iterable[SupportsIndex] | SupportsBytes | ReadableBuffer,byteorder: Literal["little", "big"],*,signed: bool = False,) -> Self: ...if sys.version_info >= (3, 12):def is_integer(self) -> Literal[True]: ...def __add__(self, value: int, /) -> int: ...def __sub__(self, value: int, /) -> int: ...def __mul__(self, value: int, /) -> int: ...def __floordiv__(self, value: int, /) -> int: ...def __truediv__(self, value: int, /) -> float: ...def __mod__(self, value: int, /) -> int: ...def __divmod__(self, value: int, /) -> tuple[int, int]: ...def __radd__(self, value: int, /) -> int: ...def __rsub__(self, value: int, /) -> int: ...def __rmul__(self, value: int, /) -> int: ...def __rfloordiv__(self, value: int, /) -> int: ...def __rtruediv__(self, value: int, /) -> float: ...def __rmod__(self, value: int, /) -> int: ...def __rdivmod__(self, value: int, /) -> tuple[int, int]: ...@overloaddef __pow__(self, x: Literal[0], /) -> Literal[1]: ...@overloaddef __pow__(self, value: Literal[0], mod: None, /) -> Literal[1]: ...@overloaddef __pow__(self, value: _PositiveInteger, mod: None = None, /) -> int: ...@overloaddef __pow__(self, value: _NegativeInteger, mod: None = None, /) -> float: ...# positive __value -> int; negative __value -> float# return type must be Any as `int | float` causes too many false-positive errors@overloaddef __pow__(self, value: int, mod: None = None, /) -> Any: ...@overloaddef __pow__(self, value: int, mod: int, /) -> int: ...def __rpow__(self, value: int, mod: int | None = None, /) -> Any: ...def __and__(self, value: int, /) -> int: ...def __or__(self, value: int, /) -> int: ...def __xor__(self, value: int, /) -> int: ...def __lshift__(self, value: int, /) -> int: ...def __rshift__(self, value: int, /) -> int: ...def __rand__(self, value: int, /) -> int: ...def __ror__(self, value: int, /) -> int: ...def __rxor__(self, value: int, /) -> int: ...def __rlshift__(self, value: int, /) -> int: ...def __rrshift__(self, value: int, /) -> int: ...def __neg__(self) -> int: ...def __pos__(self) -> int: ...def __invert__(self) -> int: ...def __trunc__(self) -> int: ...def __ceil__(self) -> int: ...def __floor__(self) -> int: ...def __round__(self, ndigits: SupportsIndex = ..., /) -> int: ...def __getnewargs__(self) -> tuple[int]: ...def __eq__(self, value: object, /) -> bool: ...def __ne__(self, value: object, /) -> bool: ...def __lt__(self, value: int, /) -> bool: ...def __le__(self, value: int, /) -> bool: ...def __gt__(self, value: int, /) -> bool: ...def __ge__(self, value: int, /) -> bool: ...def __float__(self) -> float: ...def __int__(self) -> int: ...def __abs__(self) -> int: ...def __hash__(self) -> int: ...def __bool__(self) -> bool: ...def __index__(self) -> int: ...

        如果一个类没有指定父类，则其默认继承object类，它是python中所有类的基类，如例2所示，注意在最后使用了issubclass函数进行了检验。

# 例2
class object:__doc__: str | None__dict__: dict[str, Any]__module__: str__annotations__: dict[str, Any]@propertydef __class__(self) -> type[Self]: ... # 注意这个属性@__class__.setterdef __class__(self, type: type[object], /) -> None: ... def __init__(self) -> None: ...def __new__(cls) -> Self: ...# N.B. `object.__setattr__` and `object.__delattr__` are heavily special-cased by type checkers.# Overriding them in subclasses has different semantics, even if the override has an identical signature.def __setattr__(self, name: str, value: Any, /) -> None: ...def __delattr__(self, name: str, /) -> None: ...def __eq__(self, value: object, /) -> bool: ...def __ne__(self, value: object, /) -> bool: ...def __str__(self) -> str: ...  # noqa: Y029def __repr__(self) -> str: ...  # noqa: Y029def __hash__(self) -> int: ...def __format__(self, format_spec: str, /) -> str: ...def __getattribute__(self, name: str, /) -> Any: ...def __sizeof__(self) -> int: ...# return type of pickle methods is rather hard to express in the current type system# see #6661 and https://docs.python.org/3/library/pickle.html#object.__reduce__def __reduce__(self) -> str | tuple[Any, ...]: ...def __reduce_ex__(self, protocol: SupportsIndex, /) -> str | tuple[Any, ...]: ...if sys.version_info >= (3, 11):def __getstate__(self) -> object: ...def __dir__(self) -> Iterable[str]: ...def __init_subclass__(cls) -> None: ...@classmethoddef __subclasshook__(cls, subclass: type, /) -> bool: ...print(issubclass(int, object)) # 注意使用类名int而不是int()# 输出
True

        type是一个python内置类，例3是它的定义，如所有其他类一样，它也继承了object类。

# 例3
class type:# object.__base__ is None. Otherwise, it would be a type.@propertydef __base__(self) -> type | None: ...__bases__: tuple[type, ...]@propertydef __basicsize__(self) -> int: ...@propertydef __dict__(self) -> types.MappingProxyType[str, Any]: ...  # type: ignore[override]@propertydef __dictoffset__(self) -> int: ...@propertydef __flags__(self) -> int: ...@propertydef __itemsize__(self) -> int: ...__module__: str@propertydef __mro__(self) -> tuple[type, ...]: ...__name__: str__qualname__: str@propertydef __text_signature__(self) -> str | None: ...@propertydef __weakrefoffset__(self) -> int: ...@overloaddef __init__(self, o: object, /) -> None: ...@overloaddef __init__(self, name: str, bases: tuple[type, ...], dict: dict[str, Any], /, **kwds: Any) -> None: ...@overloaddef __new__(cls, o: object, /) -> type: ...@overloaddef __new__(cls: type[_typeshed.Self], name: str, bases: tuple[type, ...], namespace: dict[str, Any], /, **kwds: Any) -> _typeshed.Self: ...def __call__(self, *args: Any, **kwds: Any) -> Any: ...def __subclasses__(self: _typeshed.Self) -> list[_typeshed.Self]: ...# Note: the documentation doesn't specify what the return type is, the standard# implementation seems to be returning a list.def mro(self) -> list[type]: ...def __instancecheck__(self, instance: Any, /) -> bool: ...def __subclasscheck__(self, subclass: type, /) -> bool: ...@classmethoddef __prepare__(metacls, name: str, bases: tuple[type, ...], /, **kwds: Any) -> MutableMapping[str, object]: ...if sys.version_info >= (3, 10):def __or__(self, value: Any, /) -> types.UnionType: ...def __ror__(self, value: Any, /) -> types.UnionType: ...if sys.version_info >= (3, 12):__type_params__: tuple[TypeVar | ParamSpec | TypeVarTuple, ...]print(issubclass(type, object)) # 注意使用类名type而不是type()# 输出
True

        type()类可以返回一个对象（即类的实例）的类，它实际上是返回一个对象（即类的实例）的__class__属性，而__class__属性在例化一个类时会自动设置，下面的例4说明了这一点。

# 例4
a=1
b=1.0
c="1"
d=[1,2,3]
e=(1,2,3)
f={1,2,3}
g={"a":1,"b":2}
h=1+2j
i=True
def j():pass
class k:pass
kk=k()print(type(a), a.__class__, issubclass(type(a), object))
print(type(b), b.__class__, issubclass(type(b), object))
print(type(c), c.__class__, issubclass(type(c), object))
print(type(d), d.__class__, issubclass(type(d), object))
print(type(e), e.__class__, issubclass(type(e), object))
print(type(f), f.__class__, issubclass(type(f), object))
print(type(g), g.__class__, issubclass(type(g), object))
print(type(h), h.__class__, issubclass(type(h), object))
print(type(i), i.__class__, issubclass(type(i), object))
print(type(j), j.__class__, issubclass(type(j), object))
print(type(kk), kk.__class__, issubclass(type(kk), object))# 输出
<class 'int'> <class 'int'> True
<class 'float'> <class 'float'> True
<class 'str'> <class 'str'> True    
<class 'list'> <class 'list'> True  
<class 'tuple'> <class 'tuple'> True
<class 'set'> <class 'set'> True
<class 'dict'> <class 'dict'> True
<class 'complex'> <class 'complex'> True
<class 'bool'> <class 'bool'> True
<class 'function'> <class 'function'> True
<class '__main__.k'> <class '__main__.k'> True

        注意到在type类针对实例kk使用时，实际上返回了其类名k，因此甚至可以使用返回值再次实例化一个对象，如下例5所示。

# 例5
class k:pass
kk=k()
kkk=type(kk)()   # type(kk)相当于k

        如果对类名再次使用type，返回的会是type类，因为所有的类都是type这个元类的实例，如下例6所示。

# 例6
class k:pass
kk=k()
print(type(type(kk)))
print(isinstance(type(kk), type)) # 检测自定义类是否是type类或其父类的实例# 输出
<class 'type'>
True

        总结来说就是，object类直接或间接是所有类的父类（可以用issubclass函数检测），而所有类又都是type类的实例（可以用isinstance函数检测）。