replace the base class

[aspineux]

Larry: Using "as", I cannot use both Circle and ColorCircle or more
like 3DCircle ... at the same time, only one of them.
But this is a easy solution in some cases.


On 31 mai, 00:25, Matimus <mccre... at gmail.com> wrote:

Hi Martimus, your idea was a good one, I used it to meet my
_particular_ needs.
I was expecting something more complicate with metaclass, object
introspection ....

I used an interface (like in Java, a class with just method that must
work in //
with anoter class).
Finally the "replacement" of the base class in done with a simple :

class ColorCircle(ColorGraphInterface, Circle):
    graph_base_class=Circle


Here is my full working test code

class Graph:
    def plot(self):
        print 'Graph.plot'

class Circle(Graph):
    def draw(self):
        print 'Circle.draw'
        self.plot()

class Square(Graph):
    def draw(self):
        print 'Square.draw'
        self.plot()

class ColorGraphInterface:
    graph_base_class=None
    def plot(self):
        print 'ColorGraphInterface.plot'
        self.graph_base_class.plot(self)
    def draw(self):
        print 'ColorGraphInterface.draw'
        self.graph_base_class.draw(self)

class ColorCircle(ColorGraphInterface, Circle):
    graph_base_class=Circle

class ColorCircle(ColorGraphInterface, Square):
    graph_base_class=Square


cc=ColorCircle()
cc.draw()




> This is a rather simplistic example, but you may be able to use a
> mixin class to achieve what you need. The idea is that you write a
> class that overrides only what is needed to add the new functionality.
> For you it would be Color.
>
> [code]
> class Graph(object):
>     def _foo(self):
>         print "Graph._foo"
>
> class Color(object):
>     def _foo(self):
>         print "Color._foo"
>
> class Circle(Graph):
>     def bar(self):
>         self._foo()
>
> class ColorCircle(Color,Circle): # the order of parent classes is
> important
>     pass
>
> if __name__ == "__main__":
>     c1 = Circle()
>     c2 = ColorCircle()
>
>     c1.bar() #prints: Graph._foo
>     c2.bar() #pritns: Color._foo
> [/code]
>
> You might not have to do anything already. Try this and see if it
> works:
>
> [code]
>
> ColorCircle(ColorGraph,Circle):
>     pass
>
> [/code]
>
> Note that you will probably have to create an __init__ method, and
> explicitly call the __init__ methods for the base classes. If the
> __init__ for Circle ends up calling the __init__ method from Graph,
> you may have issues. That is why the Color mixin that I created
> inherited from object not Graph. It helps to avoid clashing __init__
> methods.

Yes I know, super() do a great job for that :-)

>
> Matt