[jira] [Resolved] (ARROW-3652) [Python] CategoricalIndex is lost after reading back

["Wes McKinney (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-3652?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wes McKinney resolved ARROW-3652.
---------------------------------
    Fix Version/s:     (was: 1.0.0)
                   0.15.0
       Resolution: Fixed

Issue resolved by pull request 5117
[https://github.com/apache/arrow/pull/5117]

> [Python] CategoricalIndex is lost after reading back
> ----------------------------------------------------
>
>                 Key: ARROW-3652
>                 URL: https://issues.apache.org/jira/browse/ARROW-3652
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 0.11.1
>            Reporter: Armin Berres
>            Assignee: Wes McKinney
>            Priority: Major
>              Labels: parquet, pull-request-available
>             Fix For: 0.15.0
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> When a {{CategoricalIndex}} is written and read back the resulting index is not more categorical.
> {code}
> 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')
> ref_df = pq.read_pandas('test.parquet').to_pandas()
> print(df.index)
> # CategoricalIndex(['a', 'c'], categories=['a', 'c'], ordered=False, name='c1', dtype='category')
> print(ref_df.index)
> # Index(['a', 'c'], dtype='object', name='c1')
> {code}
> In the metadata the information is correctly contained:
> {code:java}
> {"name": "c1", "field_name": "c1", "p'
>             b'andas_type": "categorical", "numpy_type": "int8", "metadata": {"'
>             b'num_categories": 2, "ordered": false}
> {code}
>  



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