[jira] [Resolved] (ARROW-3654) [Python] Column with CategoricalIndex fails to be read back

["Sutou Kouhei (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-3654?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sutou Kouhei resolved ARROW-3654.
---------------------------------
    Resolution: Cannot Reproduce

> [Python] Column with CategoricalIndex fails to be read back
> -----------------------------------------------------------
>
>                 Key: ARROW-3654
>                 URL: https://issues.apache.org/jira/browse/ARROW-3654
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 0.11.1
>            Reporter: Armin Berres
>            Priority: Major
>              Labels: parquet
>
> When a column with a \{Categoricalndex} is written the data can never be read back.
>  {code:python}
> df = pd.DataFrame([['a', 'b'], ['c', 'd']], columns=['c1', 'c2'])
> df['c1'] = df['c1'].astype('category')
> df = df.set_index(['c1'])
> table = pa.Table.from_pandas(df)
> pq.write_table(table, 'test.parquet')
> pq.read_pandas('test.parquet').to_pandas()
> {code}
> Results in
> {code}
> KeyError                                  Traceback (most recent call last)
> ~/venv/mpptool/lib/python3.7/site-packages/pyarrow/pandas_compat.py in _pandas_type_to_numpy_type(pandas_type)
>     676     try:
> --> 677         return _pandas_logical_type_map[pandas_type]
>     678     except KeyError:
> KeyError: 'categorical'
> {code}
> The schema looks good:
> {code}
> column_indexes": [{"name": "c1", "field_name": "c1", "pandas_type": "categorical", "numpy_type": "int8", "metadata": {"num_categories": 2, "ordered": false}}]
> {code}



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