Description

JelleZijlstra

opened on Jun 4, 2024

Issue body actions

Bug report

Bug description:

The __round__ method on floats accepts None as an explicit argument, but the one on int does not:

>>> (1.0).__round__(None)
1
>>> (1).__round__(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object cannot be interpreted as an integer

This goes against the general principle that any operation that works on a float should also work on an int.

(Note that both round(x) and round(x, None) work on both floats and ints; this issue is entirely about direct calls to .__round__().)

CPython versions tested on:

3.12, CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-120080: Accept None as a valid argument for direct call of the int.__round__ #120088
• [3.13] gh-120080: Accept None as a valid argument for direct call of the int.__round__ (GH-120088) #120197
• gh-120080: Mark test_round_with_none_arg_direct_call as cpython_only #120328

Activity

1. JelleZijlstra

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   easy

   3.12only security fixesonly security fixes

   3.13only security fixesonly security fixes

   3.14bugs and security fixesbugs and security fixes

   and removed

   3.12only security fixesonly security fixes

   3.13only security fixesonly security fixes

   on Jun 4, 2024
2. serhiy-storchaka commented on Jun 5, 2024

   

   serhiy-storchaka

   on Jun 5, 2024

   Member

   More actions

   I do not think that there is a bug. The operation that works on a float and on an int is round(x, None), the rest is an implementation detail. You do not expect that int.__add__ works on a float, aren't?

   Reacted by Gouvernathor
3. vstinner

   added a commit that references this issue on Jun 7, 2024

   gh-120080: Accept ``None`` as a valid argument for direct call of the…

   57ad769
4. miss-islington

   added a commit that references this issue on Jun 7, 2024

   pythongh-120080: Accept ``None`` as a valid argument for direct call …

   4e3866e
5. vstinner commented on Jun 7, 2024

   

   vstinner

   on Jun 7, 2024

   Member

   More actions

   Fixed by commit: 57ad769. See my rationale for the change: #120088 (comment).
6. vstinner

   closed this as completedon Jun 7, 2024
7. serhiy-storchaka commented on Jun 7, 2024

   

   serhiy-storchaka

   on Jun 7, 2024

   Member

   More actions

   Note that Decimal.__round__ does not accept None. And perhaps many third-party numeric types do not accept it. Implementing this for int.__round__ sends a false signal that this is required. It won't be long before somebody open an issue about Decimal.__round__, and then authors of third-party libraries will be under pressure to implement this unneeded feature in their code. This opened a can of worms, and we do not know what long term consequences will be.

   Not everything that can be implemented should be implemented, and I believe that this is such a case.

   Reacted by Erlend E. Aasland and Gouvernathor
8. vstinner commented on Jun 7, 2024

   

   vstinner

   on Jun 7, 2024

   Member

   More actions

   My motivation to merge the PR was to avoid <unrepresentable> in the function signature. This marker causes issues. See for example: https://discuss.python.org/t/ac-null-defaults-prevent-correct-signatures-lets-add-inspect-unrepresentable-to-fix-this/30753
9. serhiy-storchaka commented on Jun 7, 2024

   

   serhiy-storchaka

   on Jun 7, 2024

   Member

   More actions

   #73536 is the general solution of this problem.

   Reacted by Erlend E. Aasland
10. vstinner commented on Jun 7, 2024

    

    vstinner

    on Jun 7, 2024

    Member

    More actions

    #73536 is the general solution of this problem.

    Ok, but this issue is open since 2017 and is not fixed yet.

    IMO accepting None is just a harmless way to fix the issue.
11. serhiy-storchaka commented on Jun 7, 2024

    

    serhiy-storchaka

    on Jun 7, 2024

    Member

    More actions

    Few months ago I finally created a draft (#117671). I hope this will be included in 3.14.

    Reacted by Erlend E. Aasland and Victor Stinner
12. Eclips4

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

    pythongh-120080: Mark test as cpython_only

    769aae4
13. vstinner

    added a commit that references this issue on Jun 11, 2024

    gh-120080: Mark test_round_with_none_arg_direct_call as cpython_only (#…

    02c1dff
14. mrahtz

    added a commit that references this issue on Jun 30, 2024

    pythongh-120080: Mark test_round_with_none_arg_direct_call as cpython…

    22ffaf4
15. estyxx

    added 2 commits that reference this issue on Jul 17, 2024

    pythongh-120080: Accept ``None`` as a valid argument for direct call …

    86ce3ff

    pythongh-120080: Mark test_round_with_none_arg_direct_call as cpython…

    b973063

Issue actions