Re: learnpython.org - an online interactive Python tutorial

Date	2011-04-21 09:30 +0200
From	Heiko Wundram <modelnine@modelnine.org>
Subject	Re: learnpython.org - an online interactive Python tutorial
References	<506eb5e4-4f29-473a-8d47-2082322e005e@glegroupsg2000goo.googlegroups.com> <201104211710.19587.akabaila@pcug.org.au> <BANLkTimCG4v8j+St0aSaqkMomhyHp5VYhA@mail.gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.687.1303371055.9059.python-list@python.org> (permalink)

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Am 21.04.2011 09:19, schrieb Chris Angelico:
> On Thu, Apr 21, 2011 at 5:10 PM, Algis Kabaila <akabaila@pcug.org.au> wrote:
>> False: Python IS strongly typed, without doubt (though the
>> variables are not explicitly declared.)
> 
> Strongly duck-typed though. If I create a class that has all the right
> members, it can simultaneously be a file, an iterable, a database, and
> probably even a web browser if it feels like it. Is that strong typing
> or not?

Yes, that's strong typing, because your class only works in those
contexts that you "explicitly" allow it to work in (through implementing
an interface, be it an iterator, a file, etc.), independent of
"duck-typing" (which is pretty much described by the term
interface-based typing IMHO).

The difference between strong typing and weak typing is best described by:

Python 2.6.5 (r265:79063, Jun 12 2010, 17:07:01)
[GCC 4.3.4 20090804 (release) 1] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 1+'2'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
>>>

which means that the interface for implementing "+" on the input types
"int" and "str" isn't implemented (i.e., TypeError). Weakly typed
languages allow this to work:

modelnine@gj-celle ~ $ php
<?php echo 1+'2'; ?>
3
modelnine@gj-celle ~ $

through all kinds of type-casting magic, which isn't explicitly
specified as interfaces on the objects (PHP also has integer and string
objects) themselves.

-- 
--- Heiko.

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learnpython.org - an online interactive Python tutorial Ron <ron.reiter@gmail.com> - 2011-04-20 10:15 -0700
  Re: learnpython.org - an online interactive Python tutorial Matty Sarro <msarro@gmail.com> - 2011-04-20 13:57 -0400
  Re: learnpython.org - an online interactive Python tutorial Terry Reedy <tjreedy@udel.edu> - 2011-04-20 18:12 -0400
  Re: learnpython.org - an online interactive Python tutorial Chris Angelico <rosuav@gmail.com> - 2011-04-21 14:07 +1000
  Re: learnpython.org - an online interactive Python tutorial Algis Kabaila <akabaila@pcug.org.au> - 2011-04-21 17:10 +1000
    Re: learnpython.org - an online interactive Python tutorial harrismh777 <harrismh777@charter.net> - 2011-04-21 02:29 -0500
  Re: learnpython.org - an online interactive Python tutorial Chris Angelico <rosuav@gmail.com> - 2011-04-21 17:19 +1000
  Re: learnpython.org - an online interactive Python tutorial Heiko Wundram <modelnine@modelnine.org> - 2011-04-21 09:30 +0200
    Re: learnpython.org - an online interactive Python tutorial harrismh777 <harrismh777@charter.net> - 2011-04-22 01:38 -0500
      Re: learnpython.org - an online interactive Python tutorial Chris Angelico <rosuav@gmail.com> - 2011-04-22 17:08 +1000
        Re: learnpython.org - an online interactive Python tutorial harrismh777 <harrismh777@charter.net> - 2011-04-23 19:37 -0500
          Re: learnpython.org - an online interactive Python tutorial Cameron Simpson <cs@zip.com.au> - 2011-04-24 12:23 +1000
            Re: learnpython.org - an online interactive Python tutorial harrismh777 <harrismh777@charter.net> - 2011-04-23 21:39 -0500
              Re: Re: learnpython.org - an online interactive Python tutorial Dave Angel <davea@ieee.org> - 2011-04-24 07:16 -0400
                Re: learnpython.org - an online interactive Python tutorial harrismh777 <harrismh777@charter.net> - 2011-04-25 01:14 -0500
      Re: learnpython.org - an online interactive Python tutorial Mel <mwilson@the-wire.com> - 2011-04-22 09:07 -0400
        Re: learnpython.org - an online interactive Python tutorial Roy Smith <roy@panix.com> - 2011-04-22 09:22 -0400
      Re: learnpython.org - an online interactive Python tutorial Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-04-22 23:28 -0700
        Re: learnpython.org - an online interactive Python tutorial flebber <flebber.crue@gmail.com> - 2011-04-23 05:49 -0700
          Re: learnpython.org - an online interactive Python tutorial Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-04-23 11:01 -0700
        Re: learnpython.org - an online interactive Python tutorial rantingrick <rantingrick@gmail.com> - 2011-04-23 08:16 -0700
      Re: learnpython.org - an online interactive Python tutorial rantingrick <rantingrick@gmail.com> - 2011-04-23 08:21 -0700
      Re: learnpython.org - an online interactive Python tutorial Dotan Cohen <dotancohen@gmail.com> - 2011-04-23 19:51 +0300
      Re: learnpython.org - an online interactive Python tutorial Tim Chase <python.list@tim.thechases.com> - 2011-04-23 12:25 -0500
      Re: learnpython.org - an online interactive Python tutorial Westley Martínez <anikom15@gmail.com> - 2011-04-23 12:38 -0700
      Re: learnpython.org - an online interactive Python tutorial Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-24 00:42 +0000
        Re: learnpython.org - an online interactive Python tutorial Chris Angelico <rosuav@gmail.com> - 2011-04-24 11:35 +1000
          Re: learnpython.org - an online interactive Python tutorial Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-24 08:13 +0000
            Re: learnpython.org - an online interactive Python tutorial Chris Angelico <rosuav@gmail.com> - 2011-04-24 18:21 +1000
        Re: learnpython.org - an online interactive Python tutorial harrismh777 <harrismh777@charter.net> - 2011-04-23 22:10 -0500
          Re: learnpython.org - an online interactive Python tutorial Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-24 09:18 +0000
            Re: learnpython.org - an online interactive Python tutorial harrismh777 <harrismh777@charter.net> - 2011-04-25 01:20 -0500
              Re: learnpython.org - an online interactive Python tutorial Terry Reedy <tjreedy@udel.edu> - 2011-04-25 11:43 -0400
              Re: learnpython.org - an online interactive Python tutorial Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-04-26 13:06 +1200
          Re: learnpython.org - an online interactive Python tutorial jmfauth <wxjmfauth@gmail.com> - 2011-04-24 08:15 -0700
  Re: learnpython.org - an online interactive Python tutorial Westley Martínez <anikom15@gmail.com> - 2011-04-21 07:14 -0700
  Re: learnpython.org - an online interactive Python tutorial MRAB <python@mrabarnett.plus.com> - 2011-04-21 17:13 +0100
  Re: learnpython.org - an online interactive Python tutorial Dotan Cohen <dotancohen@gmail.com> - 2011-04-23 16:45 +0300

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