[Edu-sig] Getting ready for class...

[Andre Roberge]

On 3/9/06, kirby urner <kirby.urner at gmail.com> wrote:
> Here's what I'm starting with today:
>
> http://www.4dsolutions.net/ocn/python/zoo.py
>
> Note:  inheriting from object at the top level, per André's suggestion.
>
> Kirby

I like your examples. I imagine you are presenting them to the same
group of students you mentioned before.  One example that I've seen on
comp.lang.python which I really like, especially because it has a
second level of inheritance, is the following (original by John
Gabriele, with comments modified slightly here):

#-----------------------------------------------------------------
class Grand_parent( object ):

     def speak( self ):
         print 'Grand_parent.speak()'
         self.advise()

     def advise( self ):
         print 'Grand_parent.advise()'
         self.critique()

     def critique( self ):
         print 'Grand_parent.critique()'

#-----------------------------------------------------------------
class Parent( Grand_parent ):

     def speak( self ):
         print '\tParent.speak()'
         self.advise()

     def advise( self ):
         print '\tParent.advise()'
         self.critique()

     # The Parent inherits his criticism method from his/her own parent

#-----------------------------------------------------------------
class Child( Parent ):

     def speak( self ):
         print '\t\tChild.speak()'
         self.advise()

     # Currently, the Child has no really useful advice to give.  The
child will just
     # parrot what he/she hears the parent say.

     def critique( self ):
         print '\t\tChild.critique()'

#-----------------------------------------------------------------
print 'speak() calls advise(), then advise() calls critique().'
print

people = [ Grand_parent(), Parent(), Child() ]
for person in people:
     person.speak()
     print

====================
The output is:

speak() calls advise(), then advise() calls critique().

Grand_parent.speak()
Grand_parent.advise()
Grand_parent.critique()

         Parent.speak()
         Parent.advise()
Grand_parent.critique()

                 Child.speak()
         Parent.advise()
                 Child.critique()

André