You just need to collect all Structural Columns in your project using a FilteredElementCollector:
structuralColumns = FilteredElementCollector(doc).WhereElementIsNotElementType().OfCategory(BuiltInCategory.OST_StructuralColumns).ToElements()
If you want to filter based on specific properties, add a filter.
Then go through your collection and pull the parameters you are looking for such as:
columnLength = i.get_Parameter(BuiltInParameter.INSTANCE_LENGTH_PARAM).AsDouble()
baseOffset = i.get_Parameter(BuiltInParameter.SCHEDULE_BASE_LEVEL_OFFSET_PARAM).AsDouble() # or .AsValueString() if you just want to "print" the data.
all the parameters you are looking for a Built In Parameters.