This is a Python function returning unique values from a field in an ArcGIS table, either a stand alone table or a feature class. It was adapted from code sample on ArcGIS resource center Help documentation on arcpy.da.SearchCursor http://resources.arcgis.com/en/help/main/10.2/index.html#//018w00000011000000

arcpy-unique-table-field-values.py

# Depends on first importing arcpy.da at top of script
def unique_values(input_table, field):
  
    # search cursor wrapped in list generator creating list of all values
    values = (row[0] for row in arcpy.da.SearchCursor(input_table, (field)))
  
    # pass list into set to get only unique values and return the result
    return sorted(set(values))