Issues related to numpy

[hauntsaninja]

This can be a tracking issue.

See also numpy/numpy#27957

[hauntsaninja]

PR adding mypy_primer to numpy's CI: numpy/numpy#28073

[hauntsaninja]

PR fixing a crash when using numpy with weird import following settings: #18351

[hauntsaninja]

PR improving diagnostics for some case someone ran into using numpy: #18352

[jorenham]

Not sure if this has been reported before, but the following line is causing stubtest to crash with numpy>=2.2.0 in case you have an empty numpy array as argument default (which is what least scipy==1.14.1 does):

mypy/mypy/stubtest.py

Line 673 in 60da03a

if runtime_arg.default != inspect.Parameter.empty:

Because since NumPy 2.2.0, ndarray.__bool__ will raise if the array is empty. And the reason why __bool__ gets called, is because ndarray.__ne__ returns another array with np.bool dtype of the same shape:

>>> import numpy as np
>>> np.__version__
'2.2.0'
>>> a = np.array([])
>>> a
array([], dtype=float64)
>>> a == object()  # numpy "vectorizes" the `==` over each element
array([], dtype=bool)
>>> bool(a == object())
Traceback (most recent call last):
  File "<python-input-24>", line 1, in <module>
    bool(a == object())
    ~~~~^^^^^^^^^^^^^^^
ValueError: The truth value of an empty array is ambiguous. Use `array.size > 0` to check that an array is not empty.

So when stubtest encounters a def f(a=np.array([])): ... (on the .py side), stubtest will crash:

$ stubtest --mypy-config-file=pyproject.toml --allowlist=.mypyignore --ignore-unused-allowlist scipy
Traceback (most recent call last):
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/bin/stubtest", line [8](https://github.com/jorenham/scipy-stubs/actions/runs/12246812991/job/34163454128?pr=288#step:7:9), in <module>
    sys.exit(main())
             ~~~~^^
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.13/site-packages/mypy/stubtest.py", line 20[9](https://github.com/jorenham/scipy-stubs/actions/runs/12246812991/job/34163454128?pr=288#step:7:10)8, in main
    return test_stubs(parse_options(sys.argv[1:]))
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.13/site-packages/mypy/stubtest.py", line 1971, in test_stubs
    for error in test_module(module):
                 ~~~~~~~~~~~^^^^^^^^
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.13/site-packages/mypy/stubtest.py", line 247, in test_module
    yield from verify(stub, runtime, [module_name])
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.13/site-packages/mypy/stubtest.py", line 423, in verify_mypyfile
    yield from verify(stub_entry, runtime_entry, object_path + [entry])
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.13/site-packages/mypy/stubtest.py", line 578, in verify_typeinfo
    yield from verify(stub_to_verify, runtime_attr, object_path + [entry])
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.13/site-packages/mypy/stubtest.py", line [10](https://github.com/jorenham/scipy-stubs/actions/runs/12246812991/job/34163454128?pr=288#step:7:11)64, in verify_funcitem
    for message in _verify_signature(stub_sig, runtime_sig, function_name=stub.name):
                   ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.[13](https://github.com/jorenham/scipy-stubs/actions/runs/12246812991/job/34163454128?pr=288#step:7:14)/site-packages/mypy/stubtest.py", line 902, in _verify_signature
    yield from _verify_arg_default_value(stub_arg, runtime_arg)
  File "/home/runner/work/scipy-stubs/scipy-stubs/.venv/lib/python3.13/site-packages/mypy/stubtest.py", line 664, in _verify_arg_default_value
    if runtime_arg.default != inspect.Parameter.empty:
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: The truth value of an empty array is ambiguous. Use `array.size > 0` to check that an array is not empty.
Error: Process completed with exit code 1.

Luckily, fixing this is just a matter of replacing != with is not when comparing against inspect.Parameter.empty (which happens in at least 2 two other places in mypy/stubtest.py as well, btw).

I could scrape together a PR if you'd like, but that could take some time (of which I don't have a lot the coming week) as I don't have a local dev env for mypy setup at the moment. And I can imagine that's more mypy-savvy could probably fix this in a coffee break on their nokia 3310 (assuming they don't get distracted and end up playing snake 2, of course). Anyway, I wouldn't mind either way, so let me know 🤷🏻.

[hamdanal]

Not sure if this has been reported before, but the following line is causing stubtest to crash with numpy>=2.2.0 in case you have an empty numpy array as argument default (which is what least scipy==1.14.1 does):

Thanks for the report, fix is here #18353

[jorenham]

It's not possible to annotate the following behavior:

>>> class Spam: ...
>>> np.object_(Spam())
<__main__.Spam object at 0x7f536d7b5160>

And it leads to incorrectly inferred types

class Spam: ...
reveal_type(np.object_(Spam()))   # numpy.object_  (wrong; should be `Spam`)

_{Pyright correctly reports Type of "np.object_(Spam())" is "Spam".}

---

The other numpy "scalar" constructors either return an instance of themselves, or an ndarray, dependening on the input. For example:

>>> np.int8(42)
np.int8(42)
>>> np.int8([42])
array([42], dtype=int8)

The bare minimum stub looks like

class int8:
    @overload
    def __new__(cls, x: int = 0, /) -> Self: ...
    @overload
    def __new__(cls, x: Sequence[int], /) -> np.ndarray[tuple[int], np.dtype[np.int8]]: ...

But a false positive (according to the typing spec) is reported:

Incompatible return type for "__new__" (returns "ndarray[tuple[int], dtype[signedinteger[_8Bit]]]", but must return a subtype of "int8")

But even so, the second overload isn't completely ignored, because the following isn't reported as an error:

reveal_type(int8(42))  # int8  (correct)
reveal_type(int8([42]))  # int8  (wrong; should be `numpy.ndarray`)

So it's as if the return type of second __new__ overload is ignored, and Self is used instead 🤔

---

I believe that #15182 is at least in part responsible for this behavior.

---

Oh and you might already know this, but this is also blocking a typeshed fix for (at least) builtins.reversed annotations (python/typeshed#11646). So the amount of people that will be happy once this is resolved isn't limited to the numpy community :)