依赖注入

 1 #!/usr/bin/env python
 2 class Mapper:
 3     __mapper_relation = {}#__私有化,其他类不能访问
 4 
 5     @staticmethod
 6     def register(cls,value):
 7         Mapper.__mapper_relation[cls] = value
 8 
 9     @staticmethod
10     def exist(cls):
11         if cls in Mapper.__mapper_relation:
12             return True
13         return False
14     @staticmethod
15     def value(cls):
16         return Mapper.__mapper_relation[cls]
17 
18 class MyType(type):
19 
20     def __call__(cls, *args, **kwargs):
21         obj = cls.__new__(cls, *args, **kwargs)
22         arg_list = list(args)
23         if Mapper.exist(cls):
24             value = Mapper.value(cls)
25             arg_list.append(value)
26         obj.__init__(*arg_list,**kwargs)
27         return obj
28 class Foo(metaclass=MyType):
29 
30     def __init__(self, name):
31         self.name = name
32 
33     def f1(self):
34         print(self.name)
35 
36 class Bar(metaclass=MyType):
37     def __init__(self, name):
38         self.name = name
39 
40     def f1(self):
41         print(self.name)
42 Mapper.register(Foo,‘666‘)
43 Mapper.register(Bar,‘999‘)
44 a = Foo()
45 b= Bar()
46 print(a.name)
47 print(b.name)