[jira] [Created] (ARROW-2124) ArrowInvalid raised if the first item of a nested list of numpy arrays is empty

["George Sakkis (JIRA)" <ji...@apache.org>]

George Sakkis created ARROW-2124:
------------------------------------

             Summary: 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
             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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