Joris Van den Bossche created ARROW-7022:
--------------------------------------------
Summary: [Python] __arrow_array__ does not work for ExtensionTypes
in Table.from_pandas
Key: ARROW-7022
URL: https://issues.apache.org/jira/browse/ARROW-7022
Project: Apache Arrow
Issue Type: Bug
Components: Python
Reporter: Joris Van den Bossche
Fix For: 1.0.0
When someone has a custom ExtensionType defined in Python, and an array class
that gets converted to that (through {{\_\_arrow_array\_\_}}), the conversion
in pyarrow works with the array class, but not yet for the array stored in a
pandas DataFrame.
Eg using my definition of ArrowPeriodType in
https://github.com/pandas-dev/pandas/pull/28371, I see:
{code}
In [15]: pd_array = pd.period_range("2012-01-01", periods=3, freq="D").array
In [16]: pd_array
Out[16]:
<PeriodArray>
['2012-01-01', '2012-01-02', '2012-01-03']
Length: 3, dtype: period[D]
In [17]: pa.array(pd_array)
Out[17]:
<pyarrow.lib.ExtensionArray object at 0x7f657cf78768>
[
15340,
15341,
15342
]
In [18]: df = pd.DataFrame({'periods': pd_array})
In [19]: pa.table(df)
...
ArrowInvalid: ('Could not convert 2012-01-01 with type Period: did not
recognize Python value type when inferring an Arrow data type', 'Conversion
failed for column periods with type period[D]')
{code}
(this is working correctly for array objects whose {{\_\_arrow_array\_\_}} is
returning a built-in pyarrow Array).
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