类的特殊成员方法

__doc__:显示类的描述

class Dog(object):
   '''
   描述狗狗的类
   '''
   print("一个方法")

d = Dog()
print(d.__doc__)

__doc__

__module__:输出模块 __class__：输出类

class C:
    def eat(self):
        print("eat")

lib/aa

from lib.aa import C
class Dog(object):
   def eat(self):
      print("eat for dog")
obj = C()
print(obj.__module__)
print(obj.__class__)
d = Dog()
print(d.__module__)
print(d.__class__)
'''
lib.aa
<class 'lib.aa.C'>
__main__
<class '__main__.Dog'>
'''

__module__ __class__

__call__ 使用：Dog()() 执行call方法

class Dog(object):
   '''
   描述狗狗的类
   '''
   def eat(self):
      print("一个方法")

   def __call__(self, *args, **kwargs):
      print("__call__",args,kwargs)

d = Dog()
d(1,2,3,4,name = "alex")
Dog()(4,5,6,7,7,name = "alex")

View Code

__dict__

class Dog(object):
   '''
   描述狗狗的类
   '''
   sex = "man"
   def __init__(self,name,age):
      self.name = name
      self.age =age
   def eat(self):
      print("一个方法")

   def __call__(self, *args, **kwargs):
      print("__call__",args,kwargs)

print(Dog.__dict__)#类直接调用的时候，打印类里的所有属性，不包括实例属性
# {'__module__': '__main__', '__doc__': '
   描述狗狗的类
   ', 'sex': 'man', '__init__': <function Dog.__init__ at 0x00000000024998C8>, 'eat': <function Dog.eat at 0x0000000002499950>, '__call__': <function Dog.__call__ at 0x00000000024999D8>, '__dict__': <attribute '__dict__' of 'Dog' objects>, '__weakref__': <attribute '__weakref__' of 'Dog' objects>}
d = Dog("alex",12)
print(d.__dict__)#实例调用的时候，打印实例的所有属性，不包括类的属性
# {'name': 'alex', 'age': 12}

View Code

__str__:如果一个类中定义了该方法，那么打印对象时，默认输出该方法的返回值（能够辨别类对象）

class Dog(object):
   '''
   描述狗狗的类
   '''
   def __init__(self,name):
      self.name = name
   def eat(self):
      print("一个方法")

   def __call__(self, *args, **kwargs):
      print("__call__",args,kwargs)

d = Dog("alex")
print(d)
# <__main__.Dog object at 0x00000000024E87F0>

没有__str__前

class Dog(object):
   '''
   描述狗狗的类
   '''
   def __init__(self,name):
      self.name = name
   def eat(self):
      print("一个方法")

   def __call__(self, *args, **kwargs):
      print("__call__",args,kwargs)

   def __str__(self):
      return "<obj:%s>"%self.name

d = Dog("alex")
print(d)
# <obj:alex>

有__str__后

__getitem__ __setitem__　　__delitem__

class Foo(object):
    def __init__(self):
       self.data = {}

    def __getitem__(self, key):
        print("__getitem__",key)

    def __setitem__(self, key, value):
        print("__setitem__",key,value)
    def __delitem__(self, key):
        print("__delitem__",key)

obj = Foo()
res = obj["a"]
obj["name"] = "alex"
del obj["name"]

认识

class Foo(object):
    def __init__(self):
       self.data = {}

    def __getitem__(self, key):
        print("__getitem__",key)
        return  self.data.get(key)

    def __setitem__(self, key, value):
        print("__setitem__",key,value)
        self.data[key] = value
    def __delitem__(self, key):
        print("__delitem__",key)

obj = Foo()
obj["name"] = "alex"#触发__setitem__
print(obj["name"])#触发__getitem__
print(obj.data)
del obj["name"] #触发__delitem__

View Code

__new__ ：先于__init__方法调用