[ARROW-17834] [Python] Allow creating ExtensionArray through pa.array(..) constructor

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 10.0.0
• Component/s: Python
• External issue URL: https://github.com/apache/arrow/issues/33054
• Assignee: Joris Van den Bossche
• Reporter: Joris Van den Bossche
• Created: 23/Sep/22 16:49
• Updated: 11/Jan/23 11:56
• Resolved: 05/Oct/22 08:00

Description

Currently, creating an ExtensionArray from a python sequence (or numpy array, ..) requires the following:

from pyarrow.tests.test_extension_type import IntegerType

storage_array = pa.array([1, 2, 3])
ext_arr = pa.ExtensionArray.from_storage(IntegerType(), storage_array)

While doing this directly in pa.array(..) doesn't work:

>>> pa.array([1, 2, 3], type=IntegerType())
ArrowNotImplementedError: extension

I think it should be possible to basically to the ExtensionArray.from_storage under the hood in pa.array(..) when the specified type is an extension type?

I think this should also enable converting from a pandas DataFrame (with a column with matching storage values) to a Table with a specified schema that includes an extension type. Like:

df = pd.DataFrame({'a': [1, 2, 3]})
pa.table(df, schema=pa.schema([('a', IntegerType())]))

Issue Links

• is related to: ARROW-17813 [Python] Nested ExtensionArray conversion to/from pandas/numpy