Expand float and complex strict mode to allow ints and ints/float. Updates type hints to match better with `typing.SupportsIndex` #5879

InvincibleRMC · 2025-10-23T16:03:05Z

Description

Breaking change to allow Python ints into float when under strict typing. This change was also done to complex to allow floats and ints. Now that Python ints can be passed into floats it changes behavior for overload resolution. A method that takes float that is registered before a method that takes an int will now get executed when a Python int is passed in. This overload resolution also affects methods with std::complex.

This was done to better match PEP 484 numeric tower rules.

Add typing.SupportsIndex to the int/float input types to better match fall backs.
This corrects a mistake that these where supported but, the type hint was not updated.

Change complex input types to typing.SupportsComplex | typing.SupportsFloat | typing.SupportsIndex to match runtime conversion rules.

Resolves #5878
Provides a work around for #5767

Suggested changelog entry:

Expand float and complex strict mode to allow ints and ints/float. Updates type hints to match better with typing.SupportsIndex.

📚 Documentation preview 📚: https://pybind11--5879.org.readthedocs.build/

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

gentlegiantJGC · 2025-10-23T16:27:22Z

I have started working on this too.
Your code change is more complex than required.
I will finish up the documentation changes and commit what I have and you can take it from there.

This is known at compile time so it can be constexpr

gentlegiantJGC · 2025-10-23T16:49:05Z

Here is my implementation and documentation changes.
I have modified the behaviour of complex as well.
https://github.com/gentlegiantJGC/pybind11/tree/fix-pep-484
master...gentlegiantJGC:pybind11:fix-pep-484

It needs tests but I am going to stop for today.
You are welcome to use my commits.

…trict

gentlegiantJGC · 2025-10-23T17:57:43Z

You will need to remove the constexpr check. I didn't realise it was a newer C++ feature

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

InvincibleRMC · 2025-10-23T19:57:40Z

TODO: figure out why it doesn't work in C++11.

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

gentlegiantJGC · 2025-10-24T07:41:04Z

I have just found that a python float passed to an int argument will raise a TypeError.
It will happily except anything that implements __int__ (eg a numpy float) but explicity not a python float.

This is probably something we should resolve here because it effects these tests.

m.def("func", [](int){});

>>> func.__doc__
  func(arg: typing.SupportsInt) -> None
>>> func(5.5)
  TypeError
>>> func(numpy.float32(5.5))  # This works fine

gentlegiantJGC · 2025-10-24T07:56:18Z

Here is the commit that implemented that.
3f200fa

@rwgk Can I get your input on this?
The int type caster supports anything that implements __int__ with the explicit exception of the python float.

This conflicts with the typing.SupportsInt type hint.

The int type caster allows anything that implements __int__ with explicit exception of the python float. I can't see any reason for this. This modifies the int casting behaviour to accept a float. If the argument is marked as noconvert() it will only accept int.

gentlegiantJGC · 2025-10-24T08:20:39Z

Here is my proposed change. You will need to update the tests.
gentlegiantJGC@d42c8e8
https://github.com/gentlegiantJGC/pybind11/tree/pr-5879-jgc

Here are my unittests
test_cast.py
cast.cpp

InvincibleRMC · 2025-10-24T19:14:19Z

I noticed something else to have address. According to the documentation all of int,float,complex support falling back on __index__ when converting so updated the type hint from typing.SupportsInt -> typing.SupportsInt | typing.SupportsIndex. complex also supports a __float__ fall back so its type is now typing.SupportsComplex | typing.SupportsFloat | typing.SupportsIndex

rwgk · 2025-10-26T06:07:20Z

Here is the commit that implemented that. 3f200fa

@rwgk Can I get your input on this? The int type caster supports anything that implements __int__ with the explicit exception of the python float.

This conflicts with the typing.SupportsInt type hint.

I need to find a block of time to look at this carefully. Might be a couple days.

Thanks for working on this!

gentlegiantJGC · 2025-10-26T10:20:21Z

include/pybind11/complex.h

+#if defined(PYPY_VERSION)
+        object index;
+        if (PYBIND11_INDEX_CHECK(src.ptr())) {
+            index = reinterpret_steal<object>(PyNumber_Index(src.ptr()));
+            if (!index) {
+                PyErr_Clear();
+                if (!convert)
+                    return false;
+            } else {
+                src_or_index = index;
+            }
+        }
+#endif


Can you explain why you are doing this?
Doesn't PyComplex_AsCComplex handle that?

Without this I was getting failures on old pypy versions see https://github.com/pybind/pybind11/actions/runs/18790097220/job/53618039827.

See this issue for more info pypy/pypy#3383

So I copied the logic from the numeric caster. Ref

Okay I think I understand. Can you add a comment in the code explaining it?

tests/test_builtin_casters.py

tests/test_custom_type_casters.py

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

init

515a3ab

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

InvincibleRMC mentioned this pull request Oct 23, 2025

[BUG]: SupportsInt and SupportsFloat changes cause type checking failures on python classes that override these functions #5767

Open

3 tasks

gentlegiantJGC added 4 commits October 23, 2025 17:36

Add constexpr to is_floating_point check

aa2693f

This is known at compile time so it can be constexpr

Allow noconvert float to accept int

7948b27

Update noconvert documentation

47746af

Allow noconvert complex to accept int and float

507d31c

InvincibleRMC and others added 5 commits October 23, 2025 10:02

Merge remote-tracking branch 'collab/fix-pep-484' into expand-float-s…

f4115fe

…trict

Add complex strict test

4ea8bcb

style: pre-commit fixes

81e49f6

Update unit tests so int, becomes double.

0b94f21

style: pre-commit fixes

e9bf4e5

InvincibleRMC changed the title ~~Expand float strict to take int~~ Expand float strict to take int and complex strict to take float/int Oct 23, 2025

InvincibleRMC added 3 commits October 23, 2025 11:00

remove if (constexpr)

21f8447

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

fix spelling error

5806318

bump order in #else

a0fb6dc

Switch order in c++11 only section

2692820

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

InvincibleRMC marked this pull request as ready for review October 24, 2025 00:59

InvincibleRMC added 2 commits October 23, 2025 18:11

ci: trigger build

b12f5a8

ci: trigger build

2187a65

InvincibleRMC added 2 commits October 24, 2025 11:29

tests for py::float into int

16bdff3

Update complex_cast tests

358266f

InvincibleRMC and others added 4 commits October 24, 2025 12:15

Add SupportsIndex to int and float

dadbf05

style: pre-commit fixes

248b12e

fix assert

2163f50

Update docs to mention other conversions

c13f21e

InvincibleRMC changed the title ~~Expand float strict to take int and complex strict to take float/int~~ Expand float and complex strict mode to allow ints and ints/float. Updates type hints to match better with typing.SupportsIndex Oct 24, 2025

InvincibleRMC and others added 2 commits October 24, 2025 13:18

fix pypy __index__ problems

f4ed7b7

style: pre-commit fixes

fc815ec

InvincibleRMC mentioned this pull request Oct 26, 2025

Fix *args/**kwargs return types. Add type hinting to py::make_tuple #5881

Open

gentlegiantJGC reviewed Oct 26, 2025

View reviewed changes

InvincibleRMC and others added 7 commits October 26, 2025 13:52

extract out PyLong_AsLong __index__ deprecation

388366f

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

style: pre-commit fixes

a956052

Add back env.deprecated_call

962c9fa

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

remove note

7b1bc72

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

remove untrue comment

edbcbf2

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

fix noconvert_args

a3a4a5e

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

resolve error

d5dab14

Signed-off-by: Michael Carlstrom <rmc@carlstrom.com>

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Expand float and complex strict mode to allow ints and ints/float. Updates type hints to match better with typing.SupportsIndex #5879

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Expand float and complex strict mode to allow ints and ints/float. Updates type hints to match better with `typing.SupportsIndex` #5879

Expand float and complex strict mode to allow ints and ints/float. Updates type hints to match better with `typing.SupportsIndex` #5879

InvincibleRMC commented Oct 23, 2025 •

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