Re: NaN comparisons - Call For Anecdotes

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Date	Wed, 9 Jul 2014 16:52:32 +1000
Subject	Re: NaN comparisons - Call For Anecdotes
From	Chris Angelico <rosuav@gmail.com>
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On Wed, Jul 9, 2014 at 4:43 PM, Steven D'Aprano <steve@pearwood.info> wrote:
> I don't understand this. You've just shown an example from Python 2 where
> 'in' uses 'is'. How is that a Python 3 change?

A docs change.

https://docs.python.org/2/reference/expressions.html#not-in
"""
For the list and tuple types, x in y is true if and only if there
exists an index i such that x == y[i] is true.
"""

https://docs.python.org/3/reference/expressions.html#not-in
"""
For container types such as list, tuple, set, frozenset, dict, or
collections.deque, the expression x in y is equivalent to any(x is e
or x == e for e in y).
"""

So the definition of the operator (as stated in the docs) has changed
to match its behaviour. That's definitely a change; the Py2 behaviour
is buggy according to its docs. Should the Py2 docs be updated to
match the Py3 docs, or should it be left as a minor technical
distinction that almost never is important?

ChrisA

Thread

NaN comparisons - Call For Anecdotes "Anders J. Munch" <2014@jmunch.dk> - 2014-07-08 16:53 +0200
  Re: NaN comparisons - Call For Anecdotes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-07-08 17:13 +0000
    Re: NaN comparisons - Call For Anecdotes Chris Angelico <rosuav@gmail.com> - 2014-07-09 03:21 +1000
    Re: NaN comparisons - Call For Anecdotes "Anders J. Munch" <2014@jmunch.dk> - 2014-07-08 21:02 +0200
      Re: NaN comparisons - Call For Anecdotes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-07-09 00:10 +0000
        Re: NaN comparisons - Call For Anecdotes Terry Reedy <tjreedy@udel.edu> - 2014-07-09 00:57 -0400
          Re: NaN comparisons - Call For Anecdotes Steven D'Aprano <steve@pearwood.info> - 2014-07-09 06:43 +0000
            Re: NaN comparisons - Call For Anecdotes Chris Angelico <rosuav@gmail.com> - 2014-07-09 16:52 +1000
        Re: NaN comparisons - Call For Anecdotes "Anders J. Munch" <2014@jmunch.dk> - 2014-07-09 17:08 +0200
          Re: NaN comparisons - Call For Anecdotes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-07-09 16:53 +0000
            Re: NaN comparisons - Call For Anecdotes Ian Kelly <ian.g.kelly@gmail.com> - 2014-07-09 11:26 -0600
            Re: NaN comparisons - Call For Anecdotes "Anders J. Munch" <2014@jmunch.dk> - 2014-07-09 19:44 +0200
        Re: NaN comparisons - Call For Anecdotes Chris Angelico <rosuav@gmail.com> - 2014-07-10 01:13 +1000
        Re: NaN comparisons - Call For Anecdotes "Anders J. Munch" <2014@jmunch.dk> - 2014-07-09 18:24 +0200
    Re: NaN comparisons - Call For Anecdotes "Anders J. Munch" <2014@jmunch.dk> - 2014-07-08 21:25 +0200
  Re: NaN comparisons - Call For Anecdotes Rustom Mody <rustompmody@gmail.com> - 2014-07-09 20:07 -0700

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