[Python-ideas] Disallow orderring comparison to NaN

[Nick Coghlan]

On Fri, Apr 29, 2011 at 8:10 AM, Guido van Rossum <guido at python.org> wrote:
> On Thu, Apr 28, 2011 at 12:25 PM, Alexander Belopolsky
> <alexander.belopolsky at gmail.com> wrote:
>> I posted a patch implementing this proposal on the tracker:
>>
>> http://bugs.python.org/issue11949
>
> Interesting indeed! I'd like to hear from the numpy folks about this.
>
> But isn't a similar change needed for Decimal?

decimal already works that way:

>>> from decimal import Decimal as d
>>> nan = d("nan")
>>> nan
Decimal('NaN')
>>> nan < 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python32\lib\decimal.py", line 887, in __lt__
    ans = self._compare_check_nans(other, context)
  File "C:\Python32\lib\decimal.py", line 788, in _compare_check_nans
    self)
  File "C:\Python32\lib\decimal.py", line 3926, in _raise_error
    raise error(explanation)
decimal.InvalidOperation: comparison involving NaN

+1 from me for making float NaNs raise ValueError for ordering comparisons.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia