fix: Fix from_arrow for struct type

[delsner]

Motivation

Using an arrow struct column type in an arrow table causes from_arrow to fail with the following error message:

tests/unit/dataframe/test_df.py:210: in test_from_arrow
    df = cast(pl.DataFrame, pl.from_arrow(b))
polars/convert/general.py:433: in from_arrow
    arrow_to_pydf(
polars/_utils/construction/dataframe.py:1171: in arrow_to_pydf
    elif isinstance(column.type, pa.StructType) and column.num_chunks > 1:
E   AttributeError: 'pyarrow.lib.StructArray' object has no attribute 'num_chunks'

Changes

• Fix arrow_to_pydf function to first check for the num_chunks attribute
• Update unit test
• Ruff updates

[ritchie46]

Thanks, can you add a test?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.50%. Comparing base (4c19115) to head (bebd395).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17839      +/-   ##
==========================================
- Coverage   80.51%   80.50%   -0.01%     
==========================================
  Files        1503     1504       +1     
  Lines      197038   197162     +124     
  Branches     2805     2806       +1     
==========================================
+ Hits       158641   158723      +82     
- Misses      37876    37918      +42     
  Partials      521      521              

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[delsner]

Thanks, can you add a test?

I added a unit test for both chunked and regular arrays and updated the existing unit test for from_array.

[delsner]

anything else that I should include in the PR @ritchie46?

[ritchie46]

Thank you @delsner

[AlexH-BoxFish]

I ran into this same issue and while this fix does work, I was wondering if the pa.StructType can ever have a num_chunks method? From the docs it doesn't look like it.

The only type I can see with a num_chunks method is pa.ChunkedArray, so perhaps there's another bug in this block?