gh-109218: Deprecate weird cases in the complex() constructor by serhiy-storchaka · Pull Request #119620 · python/cpython · GitHub

Passing a string as the "real" keyword argument is now an error; it should only be passed as a single positional argument.
Passing a complex number as the real or imag argument is now deprecated; it should only be passed as a single positional argument.

Issue: Invalid "equivalents" of the complex type constructor in docs #109218

📚 Documentation preview 📚: https://cpython-previews--119620.org.readthedocs.build/

* Passing a string as the "real" keyword argument is now an error; it should only be passed as a single positional argument. * Passing a complex number as the *real* or *imag* argument is now deprecated; it should only be passed as a single positional argument.

* Share common classes. * Use exactly representable floats and exact tests. * Check the sign of zero components. * Remove duplicated tests (mostly left after merging int and long). * Reorder tests in more consistent way. * Test more error messages. * Add tests for missed cases.

tmp == NULL condition on L1092 also now only partially covered.

Just checked coverage report after ./python -m test test_complex test_capi.test_complex

This inaccessible.

It is now covered by a new test added in #119635 for complex(imag=1.5).

Nit: this is not tested. Ditto for other warning.

Can this be false? If so, this is not tested.

Yes, it can be false. Added tests.

else if (PyErr_Occurred()) branch is not tested.

Hmm, it seems there is a coverage regression, not all branches are tested.

This should be covered by new tests added in test added in #119635.

Now it's better, yet one branch seems to be missed:

   1029         [ +  - ]:       3869 :     if (nbr == NULL ||

Looks like it's nbr!=NULL.

Actually, own_r condition here is inaccessible. If we are here - try_complex_special_method() call above was unsuccessful.

See #109642. Maybe it worth to include constructor-related changes from that pr.

I'll see.

This code will be removed after the end of the deprecation period. So it is not worth to spent effort to optimize it.

Thank you for your review @skirpichev. Much of coverage is added by test added in #119635.

This also looks untested:

    1072         [ +  - ]:         10 :         if (nbr == NULL ||
    1073   [ +  -  +  - ]:         10 :             (nbr->nb_float == NULL && nbr->nb_index == NULL))

One branch missed:

     952         [ +  - ]:         55 :     else if ((nbr = Py_TYPE(arg)->tp_as_number) != NULL &&
     953   [ +  +  +  + ]:         55 :              (nbr->nb_float != NULL || nbr->nb_index != NULL))

How to interpret this? It looks to me that all possible combinations are covered.

nbr == NULL: complex({})
nbr != NULL && nbr->nb_float != NULL: complex(MockFloat(4.25))
nbr != NULL && nbr->nb_float == NULL && nbr->nb_index != NULL: complex(MockIndex(42))
nbr != NULL && nbr->nb_float == NULL && nbr->nb_index == NULL: complex(MockInt())

Hmm, branch coverage output for C code looks cryptic. Try complex([]), i.e. nbr != NULL, but it has no nb_float/index, that works for me.

I think complex(MyInt()) (where MyInt has the __int__ method already covers this).

No. Oh, I see: that should be nbr == NULL condition. So complex(object()) will work too.

Would it be worth adding a comment above this function explaining the purpose (and explaining why this is different from complex_new)?

LGTM in principle, and works as expected in manual testing. I won't claim to have examined all the branching possibilities, but it looks as though @skirpichev is on top of that. :-)

FYI, this is not tested. But I'm not sure if that's a right logic. Complex subclasses should be covered by try_complex_special_method(), c.f. PyNumber_Float().

try_complex_special_method is relatively expensive in comparison to PyNumber_Float(), because there is no nb_complex slot. And __complex__ is looked up even for exact complex, float and int. I planned to do something with this, but in a different PR. We can not also completely exclude complex subclasses without __complex__.

try_complex_special_method is relatively expensive in comparison to PyNumber_Float()

That seems to be an implementation detail. I wonder if we could add nb_complex slot: there is a reserved slot right now anyway.

And complex is looked up even for exact complex, float and int.

The current (i.e. in the main) code - uses here same logic as the float constructor: there is a case for exact complex (as for exact float in PyNumber_Float()).

We can not also completely exclude complex subclasses without complex.

People could break thing in very crazy ways, but should we support such cases? (Looks as a variant of #112636.)

FYI, discourse thread: https://discuss.python.org/t/use-nb-reserved-slot-of-pynumbermethods-to-support-complex-method/56620

Hmm, branch coverage output for C code looks cryptic. Try complex([]), i.e. nbr != NULL, but it has no nb_float/index, that works for me.

IIUIC, this logic will be dropped after a deprecation period as well. I'm not sure if this is obvious, maybe worth a comment.

LGTM, except for useless PyComplex_Check() branch in the actual_complex_new() and one missing branch coverage here.

The rest, probably, not worth for improving, as it will be eventually removed. Though, I think that removing inaccessible cases (various own_r branches) will make code more readable.

No. Oh, I see: that should be nbr == NULL condition. So complex(object()) will work too.

Suggested change

      
                else if (PyComplex_Check(arg)) {
          
                    /* Note that if arg is of a complex subtype, we're only
          
                       retaining its real & imag parts here, and the return
          
                       value is (properly) of the builtin complex type. */
          
                    Py_complex c = ((PyComplexObject*)arg)->cval;
          
                    res = complex_subtype_from_doubles(type, c.real, c.imag);
          
                }

That seems redundant (and untested). Complex subclasses have __complex__() dunder, so they should be handled by try_complex_special_method() helper (even if the dunder is broken somehow).

…ythonGH-119620) * Passing a string as the "real" keyword argument is now an error; it should only be passed as a single positional argument. * Passing a complex number as the "real" or "imag" argument is now deprecated; it should only be passed as a single positional argument.

serhiy-storchaka requested a review from mdickinson May 27, 2024 17:09

bedevere-app Bot added the awaiting core review label May 27, 2024

bedevere-app Bot mentioned this pull request May 27, 2024

Invalid "equivalents" of the complex type constructor in docs #109218

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serhiy-storchaka force-pushed the complex-constructor branch from 9ec7587 to 9035969 Compare May 27, 2024 18:06

skirpichev reviewed May 28, 2024

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serhiy-storchaka added 6 commits May 28, 2024 10:19

Merge branch 'main' into complex-constructor-tests

607e2d5

Merge branch 'main' into complex-constructor

d7b2c2f

Merge branch 'complex-constructor-tests' into complex-constructor

d7a9120

Address review comments.

537cc4e

Add more tests.

e8b6ba9

Merge branch 'complex-constructor-tests' into complex-constructor

ddfed7b

skirpichev reviewed May 28, 2024

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Simplify some code.

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skirpichev mentioned this pull request May 28, 2024

gh-109802: removed inaccessible code from complexobject.c #109642

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mdickinson reviewed May 28, 2024

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mdickinson approved these changes May 28, 2024

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bedevere-app Bot added awaiting merge and removed awaiting core review labels May 28, 2024

skirpichev reviewed May 28, 2024

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skirpichev mentioned this pull request May 29, 2024

gh-109218: Improve documentation for the complex() constructor #119687

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serhiy-storchaka added 3 commits May 29, 2024 10:22

Polishing.

14598f0

Rename Mock to With.

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Merge branch 'main' into complex-constructor

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serhiy-storchaka merged commit ef01e95 into python:main May 30, 2024

bedevere-app Bot removed the awaiting merge label May 30, 2024

serhiy-storchaka deleted the complex-constructor branch May 30, 2024 20:31

hugovk mentioned this pull request Jul 24, 2024

gh-122085: Use include files for whatsnew/3.14.rst deprecations #122242

Merged

+                      if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
+                              "complex() argument 'real' must be a real number, not %T",
+                              r)) {
+                          return NULL;

-                                   Py_TYPE(r)->tp_name);
+                                   "complex() argument 'real' must be a real number, not %T",
+                                   r);
                       if (own_r) {

		@@ -930,31 +998,23 @@ complex_new_impl(PyTypeObject type, PyObject r, PyObject *i)
		if (r == NULL) {
		r = _PyLong_GetZero();

                   /* Special-case for a single argument when type(arg) is complex. */
                   if (PyComplex_CheckExact(r) && i == NULL &&
                       type == &PyComplex_Type) {

-                  }
                   tmp = try_complex_special_method(r);
                   if (tmp) {

		@@ -970,9 +1030,8 @@ complex_new_impl(PyTypeObject type, PyObject r, PyObject *i)
		(nbr->nb_float == NULL && nbr->nb_index == NULL && !PyComplex_Check(r)))

		if (nbr == NULL \|\|
		(nbr->nb_float == NULL && nbr->nb_index == NULL))

                   return result;
               }
+              static PyObject *

gh-109218: Deprecate weird cases in the complex() constructor by serhiy-storchaka · Pull Request #119620 · python/cpython · GitHub

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gh-109218: Deprecate weird cases in the complex() constructor - #119620

gh-109218: Deprecate weird cases in the complex() constructor#119620serhiy-storchaka merged 13 commits intopython:mainpython/cpython:mainfrom serhiy-storchaka:complex-constructorserhiy-storchaka/cpython:complex-constructorCopy head branch name to clipboard

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gh-109218: Deprecate weird cases in the complex() constructor#119620
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