arcpy unique field values

unique_field_values.py

import arcpy
import os


def unique_values(vector_data, field):
    with arcpy.da.SearchCursor(vector_data, [field]) as cursor:
        return sorted({row[0] for row in cursor})


vector_data = os.path.join(r"/path/to/feature/class")
field = 'special_field'	

unique_vals = unique_values(vector_data, field)