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From "Florian Jetter (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ARROW-1328) [Python] pyarrow.Table.from_pandas option timestamps_to_ms changes column values
Date Thu, 03 Aug 2017 15:33:01 GMT
Florian Jetter created ARROW-1328:
-------------------------------------

             Summary: [Python] pyarrow.Table.from_pandas option timestamps_to_ms changes column
values
                 Key: ARROW-1328
                 URL: https://issues.apache.org/jira/browse/ARROW-1328
             Project: Apache Arrow
          Issue Type: Bug
          Components: Python
    Affects Versions: 0.5.0
         Environment: MacOS 10.12.6
python 2.7.12

pyarrow==0.5.0
pandas==0.20.3
numpy==1.13.1
python-dateutil==2.6.1
            Reporter: Florian Jetter


The {{pyarrow.Table.from_pandas}} option {{timestamps_to_ms}} changes the value of the datetime
column

{code:none}
>>> import pyarrow as pa
>>> import pandas as pd
>>> from datetime import datetime
>>>
>>> df = pd.DataFrame({'datetime': [datetime(2017, 1, 1)]})
>>> dtype = df['datetime'].dtype
>>> pa_type = pa.from_numpy_dtype(dtype)
>>> schema = pa.schema([pa.field('datetime', pa_type)])
>>> table = pa.Table.from_pandas(df=df, schema=schema, timestamps_to_ms=True)
>>> table.to_pandas()
                    datetime
0 1970-01-01 00:24:43.228800

>>> dtype
dtype('<M8[ns]')
>>> pa_type
TimestampType(timestamp[ns])
{code}



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