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Posted to issues@arrow.apache.org by "Joris Van den Bossche (JIRA)" <ji...@apache.org> on 2019/06/07 14:12:00 UTC

[jira] [Commented] (ARROW-2037) [Python]: Add tests for ARROW-1941 cases where pandas inferred type is 'empty'

    [ https://issues.apache.org/jira/browse/ARROW-2037?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16858688#comment-16858688 ] 

Joris Van den Bossche commented on ARROW-2037:
----------------------------------------------

Not fully sure what is left to do here. The referenced issue ARROW-1941 was closed by https://github.com/apache/arrow/pull/1449, which included a test for roundtrip of columns with empty lists.

Unless it is not related to that issue? Because the example of ARROW-1941 (column of empty lists) does not given an inferred type of 'empty' but 'mixed':

{code:python}
In [22]: empty_list_array = np.empty((3,), dtype=object) 
    ...: empty_list_array.fill([]) 
    ...:  
    ...: df = pd.DataFrame({'a': np.array(['1', '2', '3']), 
    ...:                    'b': empty_list_array})                                                                                                                                                                 

In [23]: df                                                                                                                                                                                                         
Out[23]: 
   a   b
0  1  []
1  2  []
2  3  []

In [25]: pd.api.types.infer_dtype(df['b'], skipna=True)                                                                                                                                                             
Out[25]: 'mixed'
{code}

> [Python]: Add tests for ARROW-1941 cases where pandas inferred type is 'empty'
> ------------------------------------------------------------------------------
>
>                 Key: ARROW-2037
>                 URL: https://issues.apache.org/jira/browse/ARROW-2037
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 0.8.0
>            Reporter: Phillip Cloud
>            Assignee: Phillip Cloud
>            Priority: Major
>             Fix For: 0.14.0
>
>




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