Re: Reusing object methods?

[Joal Heagney]

Axel Straschil wrote:
Hello!
Why not:

class A:
    def a_lengthy_method(self, params):
         # do some work depending only on data in self and params
class B(A): pass

?
Lg,
AXEL.
As a rough guess, I think the original poster was wondering how to 
include *one* specific method from class A into B, without including all 
the methods of A. Jp Calderone's suggestion of defining a special Mixin 
class seems to be the cleanest implementation.

E.g.
class MyMixin:
        """ Defines only a single method. It may be a debug call, or
        a replacement for the classes' string representation. Etc. """
        def a_lengthy_method(self,params):
                # do some work
class A(MyMixin):
        def other_lengthy_procedures(self, params):
                pass
class B(MyMixin):
        pass
The advantage of this is that you can define a normal inheritance tree 
for a variety of classes, and then specifically override a single (or 
group) of methods by placing the MyMixin class at the front of the 
inheritance call. (The book "Programming Python" uses this a LOT in the 
Tkinter section.)

E.g.
class C:
        def well_now_what_do_we_do(self):
                # stuff
        def a_lengthy_method(self,params):
                # This does the wrong stuff.
class D(MyMixin, C):
        def __init__(self):
                # blahblahblah
Now class D has the "correct" a_lengthy_method, inherited from MyMixin, 
as well as all the other methods from class C, and the methods defined 
in it's own class statement.

Joal
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