GetDistinctRows (7.0+)

#get unique values from column (7.0)
from Spotfire.Dxp.Data import DataValueCursor
from Spotfire.Dxp.Data import IndexSet

tableName = 'MyDataTable'
columnName = 'MycolumnName'

dt = Document.Data.Tables[tableName]
cursor = DataValueCursor.Create[str](dt.Columns[columnName])
distinctRows = dt.GetDistinctRows(None,cursor) #none param to grab them by the all
#distinctRows = dt.GetDistinctRows(IndexSet(dt.RowCount,True),cursor) #...or an index set with all true to get them all.

#get uniques
vals = []
distinctRows.Reset()
while distinctRows.MoveNext():vals.append(cursor.CurrentValue)

#show results
print vals