类中的特殊成员

Posted 2020-10-15 Twotigers

一些类中的特殊成员：

 

创建一个类:

class Foo:       """     这是一个注释     """       name=""       def f(self):           pass

查看他的所有成员有哪些:

import inspect   print(inspect.getmembers(Foo))

结果如下:

[(‘__class__‘, <class ‘type‘>), (‘__delattr__‘, <slot wrapper ‘__delattr__‘ of ‘object‘ objects>), (‘__dict__‘, mappingproxy({‘__dict__‘: <attribute ‘__dict__‘ of ‘Foo‘ objects>, ‘__doc__‘: ‘ 这是一个注释 ‘, ‘__module__‘: ‘__main__‘, ‘__weakref__‘: <attribute ‘__weakref__‘ of ‘Foo‘ objects>, ‘f‘: <function Foo.f at 0x048408A0>, ‘name‘: ‘‘})), (‘__dir__‘, <method ‘__dir__‘ of ‘object‘ objects>), (‘__doc__‘, ‘ 这是一个注释 ‘), (‘__eq__‘, <slot wrapper ‘__eq__‘ of ‘object‘ objects>), (‘__format__‘, <method ‘__format__‘ of ‘object‘ objects>), (‘__ge__‘, <slot wrapper ‘__ge__‘ of ‘object‘ objects>), (‘__getattribute__‘, <slot wrapper ‘__getattribute__‘ of ‘object‘ objects>), (‘__gt__‘, <slot wrapper ‘__gt__‘ of ‘object‘ objects>), (‘__hash__‘, <slot wrapper ‘__hash__‘ of ‘object‘ objects>), (‘__init__‘, <slot wrapper ‘__init__‘ of ‘object‘ objects>), (‘__le__‘, <slot wrapper ‘__le__‘ of ‘object‘ objects>), (‘__lt__‘, <slot wrapper ‘__lt__‘ of ‘object‘ objects>), (‘__module__‘, ‘__main__‘), (‘__ne__‘, <slot wrapper ‘__ne__‘ of ‘object‘ objects>), (‘__new__‘, <built-in method __new__ of type object at 0x69C5BAD0>), (‘__reduce__‘, <method ‘__reduce__‘ of ‘object‘ objects>), (‘__reduce_ex__‘, <method ‘__reduce_ex__‘ of ‘object‘ objects>), (‘__repr__‘, <slot wrapper ‘__repr__‘ of ‘object‘ objects>), (‘__setattr__‘, <slot wrapper ‘__setattr__‘ of ‘object‘ objects>), (‘__sizeof__‘, <method ‘__sizeof__‘ of ‘object‘ objects>), (‘__str__‘, <slot wrapper ‘__str__‘ of ‘object‘ objects>), (‘__subclasshook__‘, <built-in method __subclasshook__ of type object at 0x04B725B8>), (‘__weakref__‘, <attribute ‘__weakref__‘ of ‘Foo‘ objects>), (‘f‘, <function Foo.f at 0x048408A0>), (‘name‘, ‘‘)]

区分其中的字段和方法去看:

instance = []   function = []   for i in dir(Foo):       if callable(getattr(Foo, i)):           function.append(i)       else:           instance.append(i)   print(instance)   print(function)        # [‘__dict__‘, ‘__doc__‘, ‘__module__‘, ‘__weakref__‘, ‘name‘]   # [‘__class__‘, ‘__delattr__‘, ‘__dir__‘, ‘__eq__‘, ‘__format__‘, ‘__ge__‘, ‘__getattribute__‘, ‘__gt__‘, ‘__hash__‘, ‘__init__‘, ‘__le__‘, ‘__lt__‘, ‘__ne__‘, ‘__new__‘, ‘__reduce__‘, ‘__reduce_ex__‘, ‘__repr__‘, ‘__setattr__‘, ‘__sizeof__‘, ‘__str__‘, ‘__subclasshook__‘, ‘f‘]

我们看到有一下这些字段:

[‘__dict__‘, ‘__doc__‘, ‘__module__‘, ‘__weakref__‘, ‘name‘]

一个一个看:

__dict__	In [27]: Foo.__dict__ Out[27]: mappingproxy({‘__dict__‘: <attribute ‘__dict__‘ of ‘Foo‘ objects>, ‘__doc__‘: ‘ 这是一个注释 ‘, ‘__module__‘: ‘__main__‘, ‘__weakref__‘: <attribute ‘__weakref__‘ of ‘Foo‘ objects>, ‘f‘: <function __main__.Foo.f>, ‘name‘: ‘‘}) 是用来存储对象属性的一个字典，其键为属性名，值为属性的值
__doc__	In [31]: Foo.__doc__ Out[31]: ‘ 这是一个注释 ‘ 表示类的描述信息
__module__	In [32]: Foo.__module__ Out[32]: ‘__main__‘ 表示从哪个模块导入的
__weakref__	看这个就好了: 其实就是没啥用 https://stackoverflow.com/questions/36787603/what-exactly-is-weakref-in-python
‘name‘	其实就是我们定义的静态字段

接下来是方法

[‘__class__‘, ‘__delattr__‘, ‘__dir__‘, ‘__eq__‘, ‘__format__‘, ‘__ge__‘, ‘__getattribute__‘, ‘__gt__‘, ‘__hash__‘, ‘__init__‘, ‘__le__‘, ‘__lt__‘, ‘__ne__‘, ‘__new__‘, ‘__reduce__‘, ‘__reduce_ex__‘, ‘__repr__‘, ‘__setattr__‘, ‘__sizeof__‘, ‘__str__‘, ‘__subclasshook__‘, ‘f‘]

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__func__这样的都是内部方法

 

 

 

 

 

 

__init__ 构造方法:

def __init__(self): super().__init__()

__call__ 对象后面加括号，触发执行。

def __call__(self, *args, **kwargs): pass

 

`模拟一个list

# coding=utf-8   class Foo:       """模拟一个list"""       def  __getitem__(self, item):                if type(item)==int:               print(item)           else:               start=item.start               stop=item.stop               step=item.step               print(start)       def  __setitem__(self, key, value):           print(key,value)       def __delitem__(self, key):           print(key)        f=Foo()   f[1]   f[5:3:5]   del f[9]

 

 

 

 __iter__ 

用于迭代器，之所以列表、字典、元组可以进行for循环，是因为类型内部定义了 __iter__ 

In [46]: [1,2,3].__iter__() Out[46]: <list_iterator at 0x4b7e6b0>   In [47]: iter([1,2,3]) Out[47]: <list_iterator at 0x4b7e790>

 

 

__next__方法 :next(obj)

自动调用obj的iter方法

 

__new__ 和 __metaclass__看上一个博客

 

利用__new__方法可以创建单例模式