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skirpichev

opened on Nov 13, 2023

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See #106339 and #106320. But these functions are documented as public: https://docs.python.org/3/c-api/complex.html#complex-numbers-as-c-structures

I think c38c666 should be partially reverted and _Py_c_abs - documented.

On another hand, quick github search shows very little examples of using above functions. See also #106320 (comment). So, in a long term I propose to deprecate this API and related functions (PyComplex_FromCComplex/PyComplex_AsCComplex). Who knows, maybe someday we could use <complex.h>...

Linked PRs

• gh-112019: reversion of removal _Py_c_* functions in #106339 #112021
• gh-112019: Add Py_complex_abs() function #112107

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1. skirpichev

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

   on Nov 13, 2023
2. skirpichev commented on Nov 13, 2023

   

   skirpichev

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   CC @vstinner
3. Eclips4

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   topic-C-API

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4. skirpichev

   added a commit that references this issue on Nov 13, 2023

   pythongh-112019: reversion of removal _Py_c_* functions in python#106339

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5. vstinner commented on Nov 13, 2023

   

   vstinner

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   If these functions are useful, I would prefer to make them public.

   Previous discussion about this private API: #106320 (comment)
6. vstinner

   added 4 commits that reference this issue on Nov 15, 2023

   pythongh-112019: Add Py_complex_abs() function

   65c7cfe

   pythongh-112019: Add Py_complex_abs() function

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   pythongh-112019: Add Py_complex_abs() function

   78842d7

   pythongh-112019: Add Py_complex_abs() function

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7. vstinner commented on Nov 15, 2023

   

   vstinner

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   @skirpichev: Do you use these functions? Do you know a project using these functions? A code search on PyPI top 5,000 projects only found 1 line using _Py_c_pow() in the numba project.
8. skirpichev commented on Nov 15, 2023

   

   skirpichev

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   @mdickinson, should we expose these functions and details of the Py_complex struct, what do you think?

   If these functions are useful, I would prefer to make them public.

   Code search shows they aren't used too much.

   @skirpichev: Do you use these functions?

   Not outside of CPython itself.

   PS: (I'm moving discussion from #106320)

   The C99 complex API is documented at: https://en.cppreference.com/w/c/numeric/complex

   It seems, see e.g. (https://discuss.python.org/t/33433/23, llvm/llvm-project#8904), that none of popular compilers (icc maybe an exception) support this extension correctly.
9. vstinner commented on Nov 15, 2023

   

   vstinner

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   @mdickinson, should we expose these functions and details of the Py_complex struct, what do you think?

   Members of the Py_complex structure are public since the structure was added to Python 1.4 by commit f9fca92 in 1996. The structure was called complex and then was renamed to Py_complex.

   The Py_complex functions are already documented but have a _Py prefix.
10. skirpichev commented on Nov 15, 2023

    

    skirpichev

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    Also they take struct by value, a bit strange API.
11. vstinner commented on Nov 15, 2023

    

    vstinner

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    I restored removed _Py_c complex functions in #112115. The initial issue is fixed, so I close the issue.

    Later, we should consider deprecating these functions and make them fully internal. I restored these functions because they are documented.
12. vstinner

    closed this as completedon Nov 15, 2023
13. skirpichev commented on Nov 16, 2023

    

    skirpichev

    on Nov 16, 2023

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    Later, we should consider deprecating these functions and make them fully internal.

    Maybe we could keep this issue for that?
14. vstinner commented on Nov 16, 2023

    

    vstinner

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    Maybe we could keep this issue for that?

    I prefer to wait until a migration path is decision on how to get rid of private functions (which were reverted in Python 3.13. alpha2): capi-workgroup/api-evolution#24

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