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BUG: Fix read_parquet not working with data type pyarrow list (#57411) #58156

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BUG: Fix read_parquet not working with data type pyarrow list (#57411) #58156

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2 changes: 2 additions & 0 deletions pandas/core/dtypes/common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1623,6 +1623,8 @@ def pandas_dtype(dtype) -> DtypeObj:
return dtype.dtype
elif isinstance(dtype, (np.dtype, ExtensionDtype)):
return dtype
elif "list" in str(dtype) and "pyarrow" in str(dtype):
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This fix is too specific and probably doesn't fix the core issue

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@mroeschke I second this. A more general fix is needed.

return dtype

# registered extension types
result = registry.find(dtype)
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14 changes: 14 additions & 0 deletions pandas/tests/io/test_parquet.py
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Expand Up @@ -348,6 +348,20 @@ def test_cross_engine_fp_pa(df_cross_compat, pa, fp):
tm.assert_frame_equal(result, df[["a", "d"]])


def test_pyarrow_list():
pytest.importorskip("fastparquet")
import pyarrow as pa

list_int = pa.list_(pa.int64())
s = pd.Series([[1, 1], [2, 2]], dtype=pd.ArrowDtype(list_int))

df = pd.DataFrame(s, columns=["col"])
df.to_parquet("ex.parquet")

result = read_parquet(path="ex.parquet", dtype_backend="pyarrow")
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@WillAyd WillAyd Apr 5, 2024 •
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This seems off to me - so even with dtype_backend="pyarrow" we are trying to convert it to an object type? I think this should maintain the pyarrow type all the way through

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Hi William.
I do agree with you and I might be wrong.
But at least for this specific case, the object type is preserved.
Nevertheless, I will try to work on a better solution.

tm.assert_frame_equal(df, result)


class Base:
def check_error_on_write(self, df, engine, exc, err_msg):
# check that we are raising the exception on writing
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