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

(<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: