Description

rhettinger

opened on Feb 22, 2024

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Feature or enhancement

Proposal:

With floating point data, the float('NaN') special value is commonly used as a placeholder for missing values. We provide math.isnan to support stripping out those values prior to sorting or summation:

>>> from math import isnan
>>> from itertools import filterfalse
>>> data = [3.3, float('nan'), 1.1, 2.2]
>>> sorted(filterfalse(isnan, data))
[1.1, 2.2, 3.3]

For non-float data, the None special value is commonly used as a placeholder for missing values. I propose a new function in the operator module analogous to math.isnan():

>>> data = ['c', None, 'a', 'b']
>>> sorted(filterfalse(is_none, data))
['a', 'b', 'c']

This helps fulfill a primary use case for the operator module which is to support functional programming with map(), filter(), etc.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-115808: Add is_none and is_not_none operators #115814

Reacted by Alex Waygood, Arie Bovenberg, Erlend E. Aasland, Kirill Podoprigora and Gouvernathor

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1. rhettinger

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Feb 22, 2024
2. ThexXTURBOXx

   added a commit that references this issue on Feb 22, 2024

   pythongh-115808: Add is_none operator

   63b788b
3. rhettinger commented on Feb 22, 2024

   

   rhettinger

   on Feb 22, 2024

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   For convenience, it might also be nice to have is_not_none(). The matches what would be done in a typical list comprehension: cleaned = [x for x in data if x is not None]. Also, it would save the need to know about filterfalse() in itertools module which is less well known that builtin functions. A simple builtin filter() call will suffice: mean(filter(is_not_none, data)).

   Reacted by Alex Waygood, Waket Zheng and Feuermurmel
4. AlexWaygood commented on Feb 22, 2024

   

   AlexWaygood

   on Feb 22, 2024

   Member

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   For convenience, it might also be nice to have is_not_none()

   Agreed -- I was going to suggest this. It also fits the general pattern of the operator module: we have both is_ and is_not, both truth and not_, etc.

   Reacted by Raymond Hettinger
5. ThexXTURBOXx

   added a commit that references this issue on Mar 4, 2024

   pythongh-115808: Add is_none operator

   72ccb45
6. AA-Turner

   added a commit that references this issue on Aug 10, 2024

   gh-115808: Add ``is_none`` and ``is_not_none`` to ``operator`` (#115814)

   5580f31
7. AA-Turner

   closed this as completedin #115814on Aug 10, 2024
8. blhsing

   added a commit that references this issue on Aug 22, 2024

   pythongh-115808: Add ``is_none`` and ``is_not_none`` to ``operator`` (p…

   34f25eb

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