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Re: A question about Python Classes

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On 21/04/2011 18:12, Pascal J. Bourguignon wrote:
> chad<cdalten@gmail.com>  writes:
>
>> Let's say I have the following....
>>
>> class BaseHandler:
>>      def foo(self):
>>          print "Hello"
>>
>> class HomeHandler(BaseHandler):
>>      pass
>>
>>
>> Then I do the following...
>>
>> test = HomeHandler()
>> test.foo()
>>
>> How can HomeHandler call foo() when I never created an instance of
>> BaseHandler?
>
> But you created one!
>
No, he didn't, he created an instance of HomeHandler.

> test is an instance of HomeHandler, which is a subclass of BaseHandler,
> so test is also an instance of BaseHandler.
>
test isn't really an instance of BaseHandler, it's an instance of
HomeHandler, which is a subclass of BaseHandler.

If you do this:

     class BaseHandler(object):
         def foo(self):
             print "Hello"

     class HomeHandler(BaseHandler):
         pass

     test = HomeHandler()

then you'll find:

 >>> isinstance(test, BaseHandler)
True

but:

 >>> type(test)
<class '__main__.HomeHandler'>

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Thread

A question about Python Classes chad <cdalten@gmail.com> - 2011-04-21 08:43 -0700
  Re: A question about Python Classes Jean-Michel Pichavant <jeanmichel@sequans.com> - 2011-04-21 18:30 +0200
    Re: A question about Python Classes chad <cdalten@gmail.com> - 2011-04-21 09:46 -0700
  Re: A question about Python Classes "Pascal J. Bourguignon" <pjb@informatimago.com> - 2011-04-21 19:12 +0200
    Re: A question about Python Classes MRAB <python@mrabarnett.plus.com> - 2011-04-21 19:00 +0100
      Re: A question about Python Classes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-22 01:53 +0000
    Re: A question about Python Classes Jean-Michel Pichavant <jeanmichel@sequans.com> - 2011-04-22 11:47 +0200
  Re: A question about Python Classes Terry Reedy <tjreedy@udel.edu> - 2011-04-21 13:39 -0400
  Re: A question about Python Classes Ethan Furman <ethan@stoneleaf.us> - 2011-04-21 11:34 -0700
    Re: A question about Python Classes "Kyle T. Jones" <onexpadREMOVE@EVOMERyahoodotyouknow.com> - 2011-04-22 08:49 -0500
      Re: A question about Python Classes Ethan Furman <ethan@stoneleaf.us> - 2011-04-22 12:38 -0700
      Re: A question about Python Classes Ian Kelly <ian.g.kelly@gmail.com> - 2011-04-22 13:40 -0600

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