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Re: Multiple inheritance, super() and changing signature

From Ben Finney <ben+python@benfinney.id.au>
Newsgroups comp.lang.python
Subject Re: Multiple inheritance, super() and changing signature
Date 2016-06-04 06:19 +1000
Message-ID <mailman.136.1464985213.1839.python-list@python.org> (permalink)
References (4 earlier) <d91f49c5-4572-9cc4-9688-b4b3ffbce691@shopzeus.com> <CALwzidnc=Yws6gSOpt_spYWGTJkq4zOuUmcVNuyF6Xuv3dK++Q@mail.gmail.com> <CAGgTfkO4g1bdBhZzZ4gaOgFRWOBXSgM4=uuPYWEFFDQBWSQVhw@mail.gmail.com> <36545ac2-0aab-3ee6-fb60-c539c9c7c95a@shopzeus.com> <85bn3i58l8.fsf@benfinney.id.au>

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Nagy László Zsolt <gandalf@shopzeus.com> writes:

> Fortunately, I can change all of the classes, and extracting the
> common parameter into a common base class worked.

This is why Liskov's Substitution Principle is good: Thinking of it as a
law helps lead to better design.

In this case, the same parameter doing different things in different
sub-classes meant that instances of those sub-classes had difficulty
substituting for the superclass. Interrogating the design against the
LSP reveals that.

> Problem solved. Thank you for all your help!
> Cooperative classes are fantastic! :-)

I'm glad you discovered them :-)

-- 
 \       “Truth is stranger than fiction, but it is because fiction is |
  `\     obliged to stick to possibilities, truth isn't.” —Mark Twain, |
_o__)                                          _Following the Equator_ |
Ben Finney

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Thread

Multiple inheritance, super() and changing signature Nagy László Zsolt <gandalf@shopzeus.com> - 2016-05-31 18:10 +0200
  Re: Multiple inheritance, super() and changing signature Steven D'Aprano <steve@pearwood.info> - 2016-06-01 12:18 +1000
    Re: Multiple inheritance, super() and changing signature Nagy László Zsolt <gandalf@shopzeus.com> - 2016-06-03 14:10 +0200
      Re: Multiple inheritance, super() and changing signature Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-04 13:06 +1200
        Re: Multiple inheritance, super() and changing signature Steven D'Aprano <steve@pearwood.info> - 2016-06-04 12:51 +1000
          Re: Multiple inheritance, super() and changing signature Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-04 23:50 +1200
        Re: Multiple inheritance, super() and changing signature Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-03 23:05 -0600
          Re: Multiple inheritance, super() and changing signature Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-04 23:52 +1200
            Re: Multiple inheritance, super() and changing signature Steven D'Aprano <steve@pearwood.info> - 2016-06-04 23:46 +1000
              Re: Multiple inheritance, super() and changing signature Nagy László Zsolt <gandalf@shopzeus.com> - 2016-06-04 16:42 +0200
    Re: Multiple inheritance, super() and changing signature Ben Finney <ben+python@benfinney.id.au> - 2016-06-03 22:21 +1000
      Re: Multiple inheritance, super() and changing signature Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-04 13:10 +1200
    Re: Multiple inheritance, super() and changing signature Nagy László Zsolt <gandalf@shopzeus.com> - 2016-06-03 14:14 +0200
    Re: Multiple inheritance, super() and changing signature Nagy László Zsolt <gandalf@shopzeus.com> - 2016-06-03 14:57 +0200
    Re: Multiple inheritance, super() and changing signature Nagy László Zsolt <gandalf@shopzeus.com> - 2016-06-03 16:06 +0200
    Re: Multiple inheritance, super() and changing signature Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-03 08:39 -0600
    Re: Multiple inheritance, super() and changing signature Michael Selik <michael.selik@gmail.com> - 2016-06-03 15:33 +0000
    Re: Multiple inheritance, super() and changing signature Nagy László Zsolt <gandalf@shopzeus.com> - 2016-06-03 17:59 +0200
    Re: Multiple inheritance, super() and changing signature Michael Selik <michael.selik@gmail.com> - 2016-06-03 16:28 +0000
    Re: Multiple inheritance, super() and changing signature Ben Finney <ben+python@benfinney.id.au> - 2016-06-04 06:16 +1000
    Re: Multiple inheritance, super() and changing signature Ben Finney <ben+python@benfinney.id.au> - 2016-06-04 06:19 +1000
    Re: Multiple inheritance, super() and changing signature Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-03 15:53 -0600
    Re: Multiple inheritance, super() and changing signature Ben Finney <ben+python@benfinney.id.au> - 2016-06-04 10:44 +1000

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