No module named 'exceptiongroup'

[oliverfunk]

Hello,

I'm getting an error when trying to run pytest.

_pytest/_code/code.py", line 56, in <module>
    from exceptiongroup import BaseExceptionGroup
ModuleNotFoundError: No module named 'exceptiongroup'

I'm on Python 3.10 and from what I can find, pytest supports 3.8+

ExceptionGroup was only added in Python 3.11

(see https://docs.python.org/3.11/library/exceptions.html#exception-groups vs 3.10)

The following line is causing the issue:

pytest/src/_pytest/_code/code.py

Line 55 in 381593c

if sys.version_info[:2] < (3, 11):

I don't understand how I can be the first to pick up on this though so I'm pretty wary posting this issue.

Here are my versions:

pytest                        8.1.1
pytest-cov                    5.0.0
pytest-html                   4.1.1
pytest-json-report            1.5.0
pytest-metadata               3.1.1

[oliverfunk]

Okay I see what's happened.

For some reason, the exceptiongroup dep from this project did not install.

The dep. is listed here

pytest/pyproject.toml

Line 43 in 381593c

'exceptiongroup>=1.0.0rc8; python_version < "3.11"',

Best

[whateverforever]

same install problem here on python3.10 why this external dependency in the first place? especially in light of recent supply chain attacks

[The-Compiler]

@whateverforever You'll need to install pytest properly then, this it not a pytest issue. I feel like I'm stating the obvious here, but the response to supply chain attacks is not to stop using dependencies altogether and reinventing the wheel every time. The dependency is used to provide support for exception groups on older Python versions.

[whateverforever]

sure, every dependency is used for something. but why use a python3.11 feature if you want to support older versions? there are dependencies on which you depend, and there is fluff.

[The-Compiler]

You're free to use Python 3.11, in which case the backport isn't installed. 🤷

[nicoddemus]

but why use a python3.11 feature if you want to support older versions?

Just to clarify: we need to support the Python 3.11 feature in the same code base, that's why the backport is used. Note also that users in older versions might also be using the backport, in which case pytest will work as well.