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

[Gregor Lingl]

Andre Roberge schrieb:
> 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):
> 

Sorry Andre, but I really dislike this example. For me and in my lessons 
   inheritance is connected to an "isa" relation.

A Monkey isa Mammal etc.

This is violated here and i consider the confusion, which would be 
caused by this example, would outweigh the benefits, if any ...

This doesn't work:

A parent "isa" grand_parent ? - no! A child "isa" parent ? - no! I 
understand that the exmples goes about inheriting habits or opinions, 
but I really think this shouldn't be done this way

Regards

Gregor

> #-----------------------------------------------------------------
> 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
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> 
> 

-- 
Gregor Lingl
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