[jira] [Created] (ARROW-1083) Object categoricals are not serialized when only None is present

["Marco Neumann (JIRA)" <ji...@apache.org>]

Marco Neumann created ARROW-1083:
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             Summary: Object categoricals are not serialized when only None is present
                 Key: ARROW-1083
                 URL: https://issues.apache.org/jira/browse/ARROW-1083
             Project: Apache Arrow
          Issue Type: Bug
          Components: Python
    Affects Versions: 0.4.0
            Reporter: Marco Neumann
            Priority: Minor


The following code sample fails with {{pyarrow.lib.ArrowNotImplementedError: NotImplemented: unhandled type}} but should not:

{noformat}
import pandas as pd
import pyarrow as pa
import pyarrow.parquet as pq

df = pd.DataFrame({'x': [None]})
df['x'] = df['x'].astype('category')

table = pa.Table.from_pandas(df)
buf = pa.InMemoryOutputStream()

pq.write_table(table, buf)
{noformat}



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