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Posted to dev@arrow.apache.org by "Armin Berres (JIRA)" <ji...@apache.org> on 2018/10/30 10:20:05 UTC
[jira] [Created] (ARROW-3652) [Python] CategoricalIndex is lost
after reading back
Armin Berres created ARROW-3652:
-----------------------------------
Summary: [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
Reporter: Armin Berres
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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