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https://issues.apache.org/jira/browse/ARROW-3654?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16831599#comment-16831599
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Joris Van den Bossche commented on ARROW-3654:
----------------------------------------------
[~aberres] I cannot reproduce this with pyarrow 0.13 and pandas 0.24.2:
{code:java}
In [4]: 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()
Out[4]:
c2
c1
a b
c d
In [5]: pa.__version__
Out[5]: '0.13.0'
In [6]: pd.__version__
Out[6]: '0.25.0.dev0+452.g331516126'
{code}
Can you still reproduce this? Or what version were you using?
> [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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