python学习之元类

class Foo:
   pass

f=Foo()
print(type(f1)) #f1是通过Foo类实例化的对象
print(type(Foo)) #Foo是通过type类实例化的对象
print('===================>')

class Foo1:
   x=1
   def __init__(self,name,age):
      self.name=name
      self.age=age

   def test(self):
      pass

print(Foo1.__dict__)

f1=Foo1('mcc',11)

def __init__(self,name,age):
   self.name=name
   self.age=age

def test(self):
   print("=========>")
Foo2=type('Foo2',(object,),{'x':1,'__init__':__init__,'test':test})

print(Foo2.__dict__)
f2=Foo2('zcc',12)

元类type实例化（Foo,Foo1,Foo2）三个对象，同时这三个类又分别实例化(f,f1,f2)三个对象
实际应用：
class MyType(type):

   def __init__(self,a,b,c):
      pass
      # print(a)
      # print(b)
      # print(c)
   def __call__(self, *args, **kwargs):
      print('====>')
      print(self)
      obj=object.__new__(self)
      self.__init__(obj,*args,**kwargs)
      return obj

class Foo(metaclass=MyType):#MyType(Foo,'Foo',(object,),'__init__':__init__)
   def __init__(self,name,age):
      self.name=name
      self.age=age

f3=Foo('alan',12)
print(f3.__dict__)