comparison with None
howe.steven at gmail.com
Thu Apr 19 02:19:39 EDT 2007
Alan Isaac wrote:
> "Terry Reedy" <tjreedy at udel.edu> wrote in message
> news:mailman.6686.1176934558.32031.python-list at python.org...
>> Should be in the reference manual section on comparisons.
> Only to this extent:
> objects of different types always compare unequal, and are ordered
> consistently but arbitrarily.
> (This unusual definition of comparison was used to simplify the
> definition of operations like sorting and the in and not in
> In the future, the comparison rules for objects of different types
> likely to change.)
> ... Most other types compare unequal unless they are the same
> the choice whether one object is considered smaller or larger than
> another one is made arbitrarily but consistently within one
> of a program.
> This does not provide a direct answer to "why" None comparisons.
> (As far as I can tell, None is less than any object.)
> However, Gary Herron's explanation makes sense: this provides a stable
> sort when None is involved, and meets the criterion that objects of
> different types must always compare unequal. However this would also
> be true if None always compared greater than any object, and the current
> behavior does not seem to be guaranteed.
> Is that about right?
> Alan Isaac
I love scripting languages ... but sometimes an explicit evaluation that
one would find in
a compiled language is better.
Which is why I suggested using the explicit type(x) == types.NoneType as
x is None
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