Python Mixin Recipe

mixin.py

# http://littletutorials.com/2008/06/23/inheritance-not-for-code-reuse/
def mixin(mixin_cls):
    def mixin_decorator(cls):
        if not hasattr(cls, '__mixed__'):
            cls.__mixed__ = []

        for name, val in mixin_cls.__dict__.items():
            if not name.startswith('__') and not name.endswith('__'):
                if not hasattr(cls, name):
                    setattr(cls, name, val)
                    cls.__mixed__.append(name)
        return cls
        
    return mixin_decorator

mixin_examples.py

#!/usr/bin/env python
from mixin import mixin

class MixinMixin(object):

    def a_thing(self):
        return "This is a Thing!!!"

@mixin(MixinMixin)
class MyMixin(object):
    
    def i_want_this_one(self):
        return "This one"
    
    def also_this_one(self):
        return "this also"
        
    def this_one_also(self):
        return "again!"
        
class AnotherMixin(object):
    
    def here_is_something_great(self):
        return "WOO!!!!!!"
        
@mixin(AnotherMixin)
@mixin(MyMixin)
class MyClass(object):
    
    def mything(self):
        return "I'm doing my own thing here"

if __name__ == '__main__':
    print("yo!")
    my_class = MyClass()
    print my_class.mything()
    print my_class.a_thing()
    print my_class.i_want_this_one()
    print my_class.also_this_one()
    print my_class.this_one_also()
    print my_class.here_is_something_great()
    print my_class.__class__.__bases__ #Look MA! No extra parent classes!!!
    print "I just mixed in %s" % my_class.__mixed__

output

yo!
I'm doing my own thing here
This is a Thing!!!
This one
this also
again!
WOO!!!!!!
(<type 'object'>,)
I just mixed in ['this_one_also', 'i_want_this_one', 'also_this_one', 'a_thing', 'here_is_something_great']