rustyconover opened a new issue, #44182: URL: https://github.com/apache/arrow/issues/44182
### Describe the bug, including details regarding any error messages, version, and platform. An exception is raised when attempting to use a sparse or dense union with `pa.Table.from_pylist()`. **Steps to Reproduce**: Run the following Python code: ```python import pyarrow as pa schema = pa.schema([ pa.field("data", pa.dense_union([ pa.field("age", pa.int32()), pa.field("weight", pa.int32() )]) ) ]) data = [ {"data": {"age": 20}}, ] table = pa.Table.from_pylist(data, schema=schema) ``` **Expected Behavior:** The code should create a `pa.Table` using the provided schema and data. **Actual Behavior** The following exception is raised: ``` pyarrow.lib.ArrowNotImplementedError: sparse_union ``` With a traceback of: ``` Traceback (most recent call last): File "/Users/rusty/Development/flight-cloud/src/flight_cloud/example-union.py", line 7, in <module> table = pa.Table.from_pylist(data, schema=schema) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "pyarrow/table.pxi", line 1984, in pyarrow.lib._Tabular.from_pylist File "pyarrow/table.pxi", line 6230, in pyarrow.lib._from_pylist File "pyarrow/table.pxi", line 4758, in pyarrow.lib.Table.from_arrays File "pyarrow/table.pxi", line 1562, in pyarrow.lib._sanitize_arrays File "pyarrow/array.pxi", line 398, in pyarrow.lib.asarray File "pyarrow/array.pxi", line 368, in pyarrow.lib.array File "pyarrow/array.pxi", line 42, in pyarrow.lib._sequence_to_array File "pyarrow/error.pxi", line 155, in pyarrow.lib.pyarrow_internal_check_status File "pyarrow/error.pxi", line 92, in pyarrow.lib.check_status pyarrow.lib.ArrowNotImplementedError: sparse_union ``` This occurs both when using `pa.sparse_union` and `pa.dense_union`. **PyArrow version: 18.0.0.dev** ### Component(s) Python -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@arrow.apache.org.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org