python 中的mixin特性

python支持 多继承后，但能否支持动态继承性质?在程序运行过程中，重定义类的继承，python是支持这种动态继承性质的。这也就是python中 的mixin，在定义类过程中改变类的继承顺序，继承类。当某个模块不能修改时，通过mixin方式可以动态添加该类的方法，动态改变类的原有继承体系。 弄懂了多继承，mixin特性就简单多了。 但需要注意mixin后的具体继承体系的改变。

 #!/usr/bin/env python

 import types

 def MixIn(pyClass,mixInClass,makeAncestor=0):

     if makeAncestor:
         pyClass.__bases__ = (mixInClass,) + pyClass.__bases__
     elif mixInClass not in pyClass.__bases__:
         pyClass.__bases__ = pyClass.__bases__ + (mixInClass,)
     else:
         pass

 class C1(object):
     def test(self):
         print 'test in C1'

 class C0MixIn(object):
     def test(self):
         print 'test in C0MixIn'

 class C2(C1,C0MixIn):
     def test(self):
         print 'test in C2'

 class C0(C1):
     pass

 if __name__ == "__main__":

     print C0.__mro__
     c1 = C0()
     c1.test()
     MixIn(C0,C0MixIn,1)
     c0 = C0()
     c0.test()
     print C0.__mro__

     print C2.__mro__
     MixIn(C2,C0MixIn)
     print C2.__mro__

运行结果如下: python mixin2.py

点击(此处)折叠或打开

 (<class '__main__.C0'>, <class '__main__.C1'>, <type 'object'>)
 test in C1
 test in C0MixIn
 (<class '__main__.C0'>, <class '__main__.C0MixIn'>, <class '__main__.C1'>, <type 'object'>)
 (<class '__main__.C2'>, <class '__main__.C1'>, <class '__main__.C0MixIn'>, <type 'object'>)
 (<class '__main__.C2'>, <class '__main__.C1'>, <class '__main__.C0MixIn'>, <type 'object'>)

参考资料

很详细的MixIn介绍:http://www.linuxjournal.com/node/4540/print