[jira] [Created] (ARROW-9864) [Python] pathlib.Path not suppored in write_to_dataset with partition columns

["Joris Van den Bossche (Jira)" <ji...@apache.org>]

Joris Van den Bossche created ARROW-9864:
--------------------------------------------

             Summary: [Python] pathlib.Path not suppored in write_to_dataset with partition columns
                 Key: ARROW-9864
                 URL: https://issues.apache.org/jira/browse/ARROW-9864
             Project: Apache Arrow
          Issue Type: Bug
          Components: Python
            Reporter: Joris Van den Bossche


Copying over from https://github.com/pandas-dev/pandas/issues/35902


{code:python}
import pathlib

df = pd.DataFrame({'A':[1,2,3,4], 'B':'C'})

df.to_parquet('tmp_path1.parquet')  # OK
df.to_parquet(pathlib.Path('tmp_path2.parquet'))  # OK

df.to_parquet('tmp_path3.parquet', partition_cols=['B'])  # OK
df.to_parquet(pathlib.Path('tmp_path4.parquet'), partition_cols=['B'])  # TypeError
{code}

{{to_parquet}} method raises TypeError when using {{pathlib.Path()}} as an argument in case when `partition_cols` argument is not None. If no partition cols are provided, then {{pathlib.Path()}} is properly accepted

{code}
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-53-cae5a944d982> in <module>
      3 
      4 df.to_parquet('tmp_path3.parquet', partition_cols=['B']) # OK
----> 5 df.to_parquet(pathlib.Path('tmp_path4.parquet'), partition_cols=['B'])  # TypeError
...

~/miniconda3/lib/python3.7/site-packages/pyarrow/parquet.py in write_to_dataset(table, root_path, partition_cols, partition_filename_cb, filesystem, **kwargs)
   1790             subtable = pa.Table.from_pandas(subgroup, schema=subschema,
   1791                                             safe=False)
-> 1792             _mkdir_if_not_exists(fs, '/'.join([root_path, subdir]))
   1793             if partition_filename_cb:
   1794                 outfile = partition_filename_cb(keys)

TypeError: sequence item 0: expected str instance, PosixPath found
{code}



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