context from this thread: I just ran your code locally and tried materializing and got the following error with the example above:

dagster._core.errors.DagsterExecutionHandleOutputError: Error occurred while handling output "result" of step "iris_data":

  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/execution/plan/execute_plan.py", line 269, in dagster_event_sequence_for_step
    for step_event in check.generator(step_events):
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/execution/plan/execute_step.py", line 386, in core_dagster_event_sequence_for_step
    for evt in _type_check_and_store_output(step_context, user_event):
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/execution/plan/execute_step.py", line 439, in _type_check_and_store_output
    for evt in _store_output(step_context, step_output_handle, output):
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/execution/plan/execute_step.py", line 640, in _store_output
    for elt in iterate_with_context(
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_utils/__init__.py", line 469, in iterate_with_context
    with context_fn():
  File "/opt/homebrew/Cellar/python@3.10/3.10.9/Frameworks/Python.framework/Versions/3.10/lib/python3.10/contextlib.py", line 153, in __exit__
    self.gen.throw(typ, value, traceback)
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/execution/plan/utils.py", line 85, in op_execution_error_boundary
    raise error_cls(

The above exception was caused by the following exception:
AttributeError: 'NoneType' object has no attribute 'write'

  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/execution/plan/utils.py", line 55, in op_execution_error_boundary
    yield
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_utils/__init__.py", line 471, in iterate_with_context
    next_output = next(iterator)
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/execution/plan/execute_step.py", line 630, in _gen_fn
    gen_output = output_manager.handle_output(output_context, output.value)
  File "/opt/homebrew/lib/python3.10/site-packages/dagster/_core/storage/db_io_manager.py", line 139, in handle_output
    self._handlers_by_type[obj_type].handle_output(context, table_slice, obj, conn)
  File "/opt/homebrew/lib/python3.10/site-packages/dagster_gcp_pandas/bigquery/bigquery_pandas_type_handler.py", line 41, in handle_output
    pandas_gbq.to_gbq(
  File "/opt/homebrew/lib/python3.10/site-packages/pandas_gbq/gbq.py", line 1220, in to_gbq
    connector.load_data(
  File "/opt/homebrew/lib/python3.10/site-packages/pandas_gbq/gbq.py", line 614, in load_data
    chunks = tqdm.tqdm(chunks)
  File "/opt/homebrew/lib/python3.10/site-packages/tqdm/std.py", line 1109, in __init__
    self.refresh(lock_args=self.lock_args)
  File "/opt/homebrew/lib/python3.10/site-packages/tqdm/std.py", line 1361, in refresh
    self.display()
  File "/opt/homebrew/lib/python3.10/site-packages/tqdm/std.py", line 1509, in display
    self.sp(self.__str__() if msg is None else msg)
  File "/opt/homebrew/lib/python3.10/site-packages/tqdm/std.py", line 350, in print_status
    fp_write('\r' + s + (' ' * max(last_len[0] - len_s, 0)))
  File "/opt/homebrew/lib/python3.10/site-packages/tqdm/std.py", line 343, in fp_write
    fp.write(_unicode(s))
  File "/opt/homebrew/lib/python3.10/site-packages/tqdm/utils.py", line 89, in __getattr__
    return getattr(self._wrapped, name)

Does the io manager create the dataset and table automatically? Also I adjusted bellow so i can use these as the column headers in Bigquery:

names=[
            "sepal_length_cm",
            "sepal_width_cm",
            "petal_length_cm",
            "petal_width_cm",
            "species",
        ],

I’m having trouble replicating this error, but i have a few follow up questions/things for you to check: 1. Are you authenticated with GCP - ie have you run

google auth …

or have

GOOGLE_APPLICATION_CREDENTIALS

set 2. how are you running the code - ie materializing via the UI, running via the CLI, etc 3. can you update the asset to look like this just to confirm that the dataset is being downloaded correctly?

@asset
def iris_data() -> pd.DataFrame:
    df = pd.read_csv(
        "<https://archive.ics.uci.edu/ml/machine-learning-databases/iris/iris.data>",
        names=[
            "sepal_length_cm",
            "sepal_width_cm",
            "petal_length_cm",
            "petal_width_cm",
            "species",
        ],
    )
    print(df)
    return df

Thanks for the help.