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Re: Python 3: dict & dict.keys()

References (6 earlier) <51f0d36c$0$29971$c3e8da3$5496439d@news.astraweb.com> <mailman.5087.1374740125.3114.python-list@python.org> <51f0f38b$0$29971$c3e8da3$5496439d@news.astraweb.com> <mailman.5091.1374748472.3114.python-list@python.org> <51f13cc5$0$29971$c3e8da3$5496439d@news.astraweb.com>
Date 2013-07-26 01:07 +1000
Subject Re: Python 3: dict & dict.keys()
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.5105.1374764885.3114.python-list@python.org> (permalink)

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On Fri, Jul 26, 2013 at 12:57 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> [ snip lengthy explanation of sets ]
> The union operator ought to
> be symmetrical, a ∪ b should be identical to b ∪ a, but isn't. Another
> leaky abstraction.

Right. I agree with all your theory, which is fine and good. If we had
a "set of real numbers", then each one would be both equal to and
indistinguishable from any other representation of itself. But Python
doesn't work with real numbers. It works with ints and floats and
Fractions and Decimals and Guido-knows-what. (Sorry, I don't normally
talk like that, but the expression begged to be said. :) )

So since Python already lets its abstraction leak a bit for
usefulness, why not retain the exact same leak when working with a
dict? A set is a dict with no values... a dict is a set with extra
payload. They're given very similar literal notation; if they were
meant to be more distinct, why was no alternative symbol used?

(I love how a random side comment can become a topic of its own.)

ChrisA

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Re: Python 3: dict & dict.keys() Ethan Furman <ethan@stoneleaf.us> - 2013-07-24 08:57 -0700
  Re: Python 3: dict & dict.keys() Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-25 05:48 +0000
    Re: Python 3: dict & dict.keys() Chris Angelico <rosuav@gmail.com> - 2013-07-25 16:02 +1000
      Re: Python 3: dict & dict.keys() Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-25 07:27 +0000
        Re: Python 3: dict & dict.keys() Chris Angelico <rosuav@gmail.com> - 2013-07-25 18:15 +1000
          Re: Python 3: dict & dict.keys() Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-25 09:44 +0000
            Re: Python 3: dict & dict.keys() Chris Angelico <rosuav@gmail.com> - 2013-07-25 20:34 +1000
              Re: Python 3: dict & dict.keys() Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-25 14:57 +0000
                Re: Python 3: dict & dict.keys() Chris Angelico <rosuav@gmail.com> - 2013-07-26 01:07 +1000
    Re: Python 3: dict & dict.keys() Johannes Bauer <dfnsonfsduifb@gmx.de> - 2013-07-25 15:22 +0200
    Re: Python 3: dict & dict.keys() Ethan Furman <ethan@stoneleaf.us> - 2013-07-25 06:57 -0700

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