As session.query(SomeModel.col1)
returns an array of tuples like this [('value_1',),('value_2',)]
if you want t cast the result to a plain array you can do it by using one of the following statements:
values = [value[0] for value in session.query(SomeModel.col1)]
values = [model.col1 for model in session.query(SomeModel).options(load_only('col1'))]
Result:
['value_1', 'value_2']