[ARROW-1992] [Python] to_pandas crashes when using strings_to_categoricals on empty string cols on 0.8.0

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.8.0
• Fix Version/s: 0.9.0
• Component/s: Python
• Labels: pull-request-available
• Environment: OS: Windows ; Python: PY36 x64 ; Pandas: 0.22.0 ; pyarrow: 0.8.0
• External issue URL: https://github.com/apache/arrow/issues/17975
• Assignee: Licht Takeuchi
• Reporter: Victor Uriarte
• Created: 12/Jan/18 02:14
• Updated: 11/Jan/23 07:18
• Resolved: 28/Jan/18 16:34

Description

When trying to read back a table, Python crashes when pyarrow is used to read/convert a table that has a column of 0 length `strings and strings_to_categorical=True`. Example code below.
This same test ran ok with pyarrow 0.7.1

import pandas as pd
import pyarrow as pa

df = pd.DataFrame({
    'Foo': ['A', 'A', 'B', 'B', 'C'],
    'Bar': ['A1', 'A2', 'B2', 'D3', ''],
    'Baz': ['', '', '', '', ''],
})

table = pa.Table.from_pandas(df)

df = table.to_pandas(strings_to_categorical=False)  # Works
print('Categoricals=False', len(df))

df = table.to_pandas(strings_to_categorical=True)  # Crashes
print('Categoricals=True', len(df))

Issue Links

• links to: GitHub Pull Request #1508