Author mark.dickinson
Recipients georg.brandl, mark.dickinson, rhettinger, terry.reedy
Date 2008-10-10.08:56:14
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> I don't think this is necessary.

I disagree.  I think some sort of warning is necessary;  it doesn't need
to be particularly prominent, but it should be there.

Almost *all* expectations are broken for sets in the absence of
transitivity of equality for the set elements.  Consider the following
(Python 2.6) snippet involving a set s:

>>> s.remove(17)
>>> 17 in s

An element is removed from a set s, and yet it's still present after the
removal!  Doesn't this deserve an explanation somewhere?

In case you haven't guessed, here's what s is:

>>> s
set([Fraction(17, 1), Decimal('17')])

Regardless of whether one wants to call this a bug or not, I think it's
sufficiently unintuitive and surprising that it should be documented.

Terry's suggestion and wordings for the reference and library warnings
look good to me.
Date User Action Args
2008-10-10 08:57:37mark.dickinsonsetrecipients: + mark.dickinson, georg.brandl, rhettinger, terry.reedy
2008-10-10 08:57:36mark.dickinsonsetmessageid: <>
2008-10-10 08:56:15mark.dickinsonlinkissue4090 messages
2008-10-10 08:56:14mark.dickinsoncreate