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https://issues.apache.org/jira/browse/ARROW-2124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16360859#comment-16360859
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ASF GitHub Bot commented on ARROW-2124:
---------------------------------------

wesm commented on issue #1586: ARROW-2124: [Python] Add test for empty item in 
array
URL: https://github.com/apache/arrow/pull/1586#issuecomment-364952601
 
 
   Rebased

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> [Python] ArrowInvalid raised if the first item of a nested list of numpy 
> arrays is empty
> ----------------------------------------------------------------------------------------
>
>                 Key: ARROW-2124
>                 URL: https://issues.apache.org/jira/browse/ARROW-2124
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 0.8.0
>            Reporter: George Sakkis
>            Assignee: Uwe L. Korn
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 0.9.0
>
>
> See example below:
> {noformat}
> In [1]: import numpy as np
> In [2]: import pandas as pd
> In [3]: import pyarrow as pa
> In [4]: num_lists = [[2,3,4], [3,6,7,8], [], [2]]
> In [5]: series = pd.Series([np.array(s, dtype=float) for s in num_lists])
> In [6]: pa.array(series)
> Out[6]: 
> <pyarrow.lib.ListArray object at 0x7f0db8ad1688>
> [
>   [2.0,
>    3.0,
>    4.0],
>   [3.0,
>    6.0,
>    7.0,
>    8.0],
>   [],
>   [2.0]
> ]
> In [7]: num_lists.append([])
> In [8]: series = pd.Series([np.array(s, dtype=float) for s in num_lists])
> In [9]: pa.array(series)
> Out[9]: 
> <pyarrow.lib.ListArray object at 0x7f0db8ad1e58>
> [
>   [2.0,
>    3.0,
>    4.0],
>   [3.0,
>    6.0,
>    7.0,
>    8.0],
>   [],
>   [2.0],
>   []
> ]
> In [10]: num_lists.insert(0, [])
> In [11]: series = pd.Series([np.array(s, dtype=float) for s in num_lists])
> In [12]: pa.array(series)
> ---------------------------------------------------------------------------
> ArrowInvalid                              Traceback (most recent call last)
> <ipython-input-99-fc3a903278e6> in <module>()
> ----> 1 pa.array(series)
> array.pxi in pyarrow.lib.array()
> array.pxi in pyarrow.lib._ndarray_to_array()
> error.pxi in pyarrow.lib.check_status()
> ArrowInvalid: trying to convert NumPy type object but got float64
> {noformat}



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