Find item in combined list

Question

I want to combine list and do some tasks with its items. Then I want to know to which initial list belongs current item. How can I do it in less ugly way than now:

 combined_list = sorted(max_peaks_eph + min_peaks_eph) # number of lists is about 10
        for item in combined_list:
            #do some tasks....
            if something ...........
                if item in max_peaks_eph:
                    label = 'max_peaks_eph'
                elif item in min_peaks_eph:
                    label = 'min_peaks_eph'
                print (label)

Answer 1

#If you don't have duplicate ones then this will work better than yours

 combined_list = A+B+C
 sorted_list = sort(combined_list)
 item = something # that you need to find
 index = combined_list(item)
 if index< len(A):
   print("Item in A")
 elif index < len(A) +len(B):
  print("Item in B")
 else:
  print("Item in C)

Why this method is efficient is we don't need to iterate each time to check the element in the list we can check with length of the list.