For every unique value permutation in a feature class attribute field, create a unique layer displaying only these values utilizing a definition query.

add-layers-with-definition-query-from-attribute.py

# import arcpy...if already imported in your script, this is not necessary
import arcpy

def _uniqueValues(input_fc, field):
  
    # search cursor wrapped in list comprehension creating list of all values
    values = [row[0] for row in arcpy.da.SearchCursor(input_fc, (field))]
  
    # pass list into set to get only unique values and return the result reverse sorted
    return sorted(set(values), reverse=True)
    
def makeLayers(input_fc, attribute):
    
  # for every value in the unique values list
  for value in _uniqueValues(input_fc, attribute):
    
    # ensure field has correct delmiters
    sql_root = arcpy.AddFieldDelimiters(arcpy.Describe(input_fc).path, attribute)
    
    # if the field is a string data type
    if arcpy.ListFields(input_fc, attribute)[0].type == 'String':
      
      # add single quotes around value and if there are single quotes in string, escape them
      sql_tail = "'{0}'".format(value.replace("'","''"))
      
    # for all other data types, just use the value
    else:
      sql_tail = "{0}".format(value)
    
    # apply a definition query to the layer
    sql = """{0} = {1}""".format(sql_root, sql_tail)
    
    # create a layer and save the layer object to a variable, replacing / with - in the
    # name so it actually gets added
    layer = arcpy.MakeFeatureLayer_management(input_fc, value.replace("/", "-"), sql)[0]
    
    # turn layer off to speed up loop, eliminating redrawing every time a layer is added
    layer.visible = False