One Python 2.1 idea

[Alex Martelli]

"Tim Peters" <tim.one at home.com> wrote in message
news:mailman.977978231.26163.python-list at python.org...
    [snip]
> About x.foo = x.foo, I never saw anyone suggest that to save time, before
> this thread.  Where it did come up several times over the years was people
> trying to customize how a method works for a particular instance, rather
> than make a proper subclass.  Since Python made instance.__class__
writable,
> I don't see any excuse for *that* form of trickery anymore.

Might I ask for a clarification of this latter thought...?

Say I have a class Ogre with a few methods:

class Ogre(Bugaboo):
    def fee(self):
        print 'fee'
    def fie(self):
        print 'fie'
    def foo(self):
        print 'foo'
    def fum(self):
        print 'fum'

and several instances thereof, one of which is referenced by
variable x.

Now, I find out that, for that one instance only, I want to
override the normal Ogre.foo method with another function
which I also happen to have around:

def fun(self):
    print 'have fun!'


What are the 'good Pythonic ways' to do this, as opposed to
'dirty tricks'?  It seemed to me that, say:

    x.foo = new.instancemethod(fun, x, Ogre)

might be simpler and clearer than some alternative such as:

    x.__class__ = new.classobj('NewOgre', (Ogre,), {'foo':fun})


Are you saying the second approach is preferable?  Or is there
some even-simpler one that I'm missing?  I do realize a cycle
of references is generated by the new.instancemethod, as
discussed on this thread -- is that the only issue, and does
GC solve it (if no __del__'s are present), or are there others?


Alex