[ARROW-2646] [Python] Pandas roundtrip for date objects

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Fix Version/s: 0.10.0
• Component/s: Python
• Assignee: Unassigned
• Reporter: Florian Jetter
• Created: 30/May/18 09:03
• Updated: Thursday 15:41

Description

Arrow currently casts date objects to nanosecond precision datetime objects. I'd like to have a way to preserve the type during a roundtrip

>>> import pandas as pd
>>> import pyarrow as pa
>>> import datetime
>>> pa.date32().to_pandas_dtype()
dtype('<M8[ns]')
>>> df = pd.DataFrame({'date': [datetime.date(2018, 1, 1)]})
>>> df.dtypes
date object
dtype: object
>>> df_rountrip = pa.Table.from_pandas(df).to_pandas()
>>> df_rountrip.dtypes
date    datetime64[ns]
dtype: object

I'd expect something like this to work:

>>> import pandas.testing as pdt
>>> df_rountrip = pa.Table.from_pandas(df).to_pandas(date_as_object=True)
>>> pdt.assert_frame_equal(df_rountrip, df)

Issue Links

• is duplicated by: ARROW-2679 pyarrow table from/to dataframe is type-lossy