drop support for python=3.9
#8937
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| # We require a "hack" to tell type checkers that e.g. Variable + DataArray = DataArray | ||
| # In reality this returns NotImplementes, but this is not a valid type in python 3.9. | ||
| # In reality this returns NotImplemented, but this is not a valid type in python 3.9. | ||
| # Therefore, we return DataArray. In reality this would call DataArray.__add__(Variable) | ||
| # TODO: change once python 3.10 is the minimum. |
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@headtr1ck, can you explain (or directly push a fix, if possible) what you meant by this?
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I'm not sure if I will be able to code anytime soon, so here an explanation first:
If you do operators, python checks the left obj First. Since DataArray is an array-like (and therefore part of VariableCompatible), the type checker thinks that Variable + DataArray = Variable, which is incorrect.
If you want to follow the runtime behavior, you should return NotImplemented, unfortunately it is not a valid type in Python 3.9. Therefore we return DataArray directly.
Now the "fix" would be to change the return type to NotImplemented and check if it works in Python >=3.10 (I have not actually confirmed that, in case just leave things like they are since it is technically working).
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This means we could replace |
Shouldn't pyupgrade / ruff do that for us? |
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it does, but only parts of it (other fixes it deems unsafe so they require manual intervention). I don't have time to go through each of them this week, but feel to push any of these directly to this PR. |
Because of [NEP29](https://numpy.org/neps/nep-0029-deprecation_policy) NumPy only supports ≥3.10 now. Also, Zarr, NetworkX, and ([soon](pydata/xarray#8937)) Xarray will support only ≥3.10.
According to our policy (and NEP-29) we can drop support for
python=3.9since about a week ago. Interestingly, SPEC0 says we could have started doing this about half a year ago (Q4 2023).We could delay this until we have a release that is compatible with
numpy>=2.0, though (numpy>=2.1will drop support forpython=3.9).whats-new.rst