[ARROW-9594] [Python] DictionaryArray.to_numpy does not correctly convert null indexes to null values

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0.0
• Fix Version/s: 5.0.0
• Component/s: Python
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/25658
• Assignee: Alessandro Molina
• Reporter: Steve M. Kim
• Created: 29/Jul/20 13:14
• Updated: 11/Jan/23 08:07
• Resolved: 28/Apr/21 09:05

Description

Example

>>> a = pa.DictionaryArray.from_arrays(pa.array([0, 1, None, 0], type=pa.int32()), pa.array(['foo', 'bar']))
>>> a
<pyarrow.lib.DictionaryArray object at 0x7f12fc94ccf0>-- dictionary:
  [
    "foo",
    "bar"
  ]
-- indices:
  [
    0,
    1,
    null,
    0
  ]
>>> a.to_pandas()  # this works
0    foo
1    bar
2    NaN
3    foo
dtype: category
Categories (2, object): [foo, bar]
>>> a.to_numpy(zero_copy_only=False)  # this is broken
array(['foo', 'bar', 'bar', 'foo'], dtype=object)

 

Issue Links

• links to: GitHub Pull Request #10101