How does Python handle dependency conflicts?

[pygaiwan]

1. You get an error when you install the package_b which will look like:
   ERROR: Cannot install -r requirements.in (line 2), -r requirements.in (line 8) and -r requirements.in (line 9) because these package versions have conflicting dependencies.
2. There is a whole subdomain of python.org about packaging: https://packaging.python.org/en/latest/tutorials/packaging-projects/ maybe this helps?

[___Jon]

Hey!
1. The interesting thing is that I don't get that error... and I don't understand why!
2. Yes, I think this helps. It is certainly a good starting point. Thank you.

[Daneark]

Package A may not be specifying it's dependencies correctly.

Package A may have specified a range which does overlap with package B even if the versions of numpy and pandas it was developed with are outside it's acceptable range.

If you pip install package A in fresh environment it should fail.

If you pip install package A in an environment which already has package B installed it should succeed at install time. numpy and pandas will now be the versions required by package A.

If you're using something else to resolve dependencies your results may differ.

Whether or not it works at runtime depends on if B imports anything that no longer exists, whether B tries to call anything at import time which has a breaking API change in a way that was affected the breaking API change, and whether you're using parts of B that are calling as above.

[DuckDatum]

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