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https://issues.apache.org/jira/browse/ARROW-4675?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17661697#comment-17661697
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Rok Mihevc commented on ARROW-4675:
-----------------------------------
This issue has been migrated to [issue
#21205|https://github.com/apache/arrow/issues/21205] on GitHub. Please see the
[migration documentation|https://github.com/apache/arrow/issues/14542] for
further details.
> [Python] Error serializing bool ndarray in py2 and deserializing in py3
> -----------------------------------------------------------------------
>
> Key: ARROW-4675
> URL: https://issues.apache.org/jira/browse/ARROW-4675
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 0.12.0
> Environment: * pyarrow 0.12.0
> * numpy 1.16.1
> * Python 3.7.0, 2.7.15
> * (macOS 10.13.6)
> Reporter: Gabe Joseph
> Assignee: Wes McKinney
> Priority: Minor
> Labels: pull-request-available
> Fix For: 0.14.0
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> {{np.bool}} is the only dtype I've found that causes this issue. Both empty
> and non-empty arrays cause it.
> The issue only manifests from py2 to py3; staying within the same version
> succeeds, as does serializing from py3 and deserializing in py2.
> This appears to just be due to Python 2 {{str}} being deserialized in Python
> 3 as {{bytes}}; it should be {{unicode}} on the py2 end to come back as
> {{str}} in py3. I suppose something in the serialization implementation is
> writing the dtype (just for bool arrays?) using a {{str}}, but haven't dug
> into it yet.
> {code:bash}
> (two)bash-3.2$ python cereal.py
> (two)bash-3.2$ cat cereal.py
> # Python 2
> import numpy as np
> import pyarrow as pa
> data = np.array([], dtype=np.dtype('bool'))
> buf = pa.serialize(data).to_buffer()
> outstream = pa.output_stream("buffer")
> outstream.write(buf)
> outstream.close()
> # ...switch to python 3 venv...
> (three)bash-3.2$ cat decereal.py
> # Python 3
> import numpy as np
> import pyarrow as pa
> instream = pa.input_stream("buffer")
> buf = instream.read()
> data = pa.deserialize(buf)
> print(data)
> (three)bash-3.2$ python3 decereal.py
> Traceback (most recent call last):
> File "decereal.py", line 10, in <module>
> data = pa.deserialize(buf)
> File "pyarrow/serialization.pxi", line 448, in pyarrow.lib.deserialize
> File "pyarrow/serialization.pxi", line 411, in pyarrow.lib.deserialize_from
> File "pyarrow/serialization.pxi", line 262, in
> pyarrow.lib.SerializedPyObject.deserialize
> File "pyarrow/serialization.pxi", line 175, in
> pyarrow.lib.SerializationContext._deserialize_callback
> TypeError: can only concatenate str (not "bytes") to str
> {code}
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