ASF GitHub Bot commented on ARROW-2141:

BryanCutler opened a new pull request #1689: ARROW-2141: [Python] Support 
variable length binary conversion from Pandas
URL: https://github.com/apache/arrow/pull/1689
   Currently, when performing `from_pandas` conversion with binary data and the 
user specifies the type as variable length binary `pa.binary()` then the type 
is inferred and a cast from binary to binary is attempted.  The casting then 
fails because the cast kernel does not support binary types.  This PR checks if 
the user specifies a variable length binary type in conversion, and then copies 
data to a BinaryArray instead of trying to infer the type and then casting.

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> [Python] Conversion from Numpy object array to varsize binary unimplemented
> ---------------------------------------------------------------------------
>                 Key: ARROW-2141
>                 URL: https://issues.apache.org/jira/browse/ARROW-2141
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Python
>    Affects Versions: 0.8.0
>            Reporter: Antoine Pitrou
>            Assignee: Bryan Cutler
>            Priority: Major
>              Labels: pull-request-available
> {code:python}
> >>> arr = np.array([b'xx'], dtype=np.object)
> >>> pa.array(arr, type=pa.binary(2))
> <pyarrow.lib.FixedSizeBinaryArray object at 0x7fe1ecaefa98>
> [
>   b'xx'
> ]
> >>> pa.array(arr, type=pa.binary())
> Traceback (most recent call last):
>   File "<ipython-input-12-e40948b94b33>", line 1, in <module>
>     pa.array(arr, type=pa.binary())
>   File "array.pxi", line 177, in pyarrow.lib.array
>   File "error.pxi", line 77, in pyarrow.lib.check_status
>   File "error.pxi", line 85, in pyarrow.lib.check_status
> ArrowNotImplementedError: 
> /home/antoine/arrow/cpp/src/arrow/python/numpy_to_arrow.cc:1585 code: 
> converter.Convert()
> /home/antoine/arrow/cpp/src/arrow/python/numpy_to_arrow.cc:1098 code: 
> compute::Cast(&context, *arr, type_, options, &casted)
> /home/antoine/arrow/cpp/src/arrow/compute/kernels/cast.cc:1022 code: 
> Cast(ctx, Datum(array.data()), out_type, options, &datum_out)
> /home/antoine/arrow/cpp/src/arrow/compute/kernels/cast.cc:1009 code: 
> GetCastFunction(*value.type(), out_type, options, &func)
> No cast implemented from binary to binary
> {code}

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