浅谈面向对象的认识

class File():
	def file_add():pass


	def file_update():pass


	def file_del():pass


	def file_fetch():pass　　

class File():
	def __init__(self,name,age,email):
		self.name = name 
		self.age = age 
		self.email = email 
	def file_add():pass


	def file_update():pass


	def file_del():pass


	def file_fetch():pass

obj1 = File(‘oldboy‘,19,"asdf@live.com")
obj2 = File(‘oldboy1‘,119,"asdf12@live.com")　　　

class Base(object):
	def xxxx():pass

class File(Base):
	def __init__(self,name,age,email):
		self.name = name 
		self.age = age 
		self.email = email 
	def file_add():pass


	def file_update():pass


	def file_del():pass


	def file_fetch():pass

class DB(Base):
	def db_add():pass


	def db_update():pass


	def db_del():pass

	def xxxx():pass
	
	def db_fetch():pass　　

class Msg(object):
	def send():
		pass 
		
class WX(object):
	def send():
		pass 


def func(arg):
	arg.send()　　

__init__，初始化
__new__，创建对象
__call__，对象()
__getattr__，对象.xx 
__setattr__
__delattr__
__setitem__，对象[‘xx‘]
__getitem__
__delitem__

__mro__，查找成员顺序
__str__
__repr__
__iter__
__dict__
__add__　　

#方式一：
class Foo(object):pass 
#方式二：
Foo = type(‘Foo‘,(object,),{})

#方式一：
class MyType(type):
	pass 

class Foo(object,metaclass=MyType):
	# __metaclass__ = MyType    # py2
	pass 
#方式二：
Foo = MyType(‘Foo‘,(object,),{})

class Foo(object,metaclass=MyType):
	pass 
	
obj = Foo()



class MyType(type):
	def __init__(self,*args,**kwargs):
		print(‘111‘)
		super(MyType,self).__init__(*args,**kwargs)


class Base(object, metaclass=MyType):
	pass

class Foo(Base):
	pass

如果一类自己或基类中指定了metaclass，那么该类就是由metaclass指定的type或mytype创建。

同：
	class MyType(type):
		def __init__(self,*args,**kwargs):
			print(‘111‘)
			super(MyType,self).__init__(*args,**kwargs)


	# class Base(object, metaclass=MyType):
	#     pass

	Base = MyType(‘Base‘,(object,),{})

	class Foo(Base):
		pass
同：
	class MyType(type):
		def __init__(self,*args,**kwargs):
			print(‘111‘)
			super(MyType,self).__init__(*args,**kwargs)


	# class Base(object, metaclass=MyType):
	#     pass
	def with_metaclass(arg):
		Base = MyType(‘Base‘,(arg,),{})
		return Base

	class Foo(with_metaclass(object)):
		pass
- 创建类时，先执行type的__init__。
- 类的实例化时，执行type的__call__，__call__方法的的返回值就是实例化的对象。
	__call__内部调用：
		- 类.__new__，创建对象
		- 类.__init__，对象的初始化