Exercise 1

def find_dups(list): ””” (list) -> set

Return the number of duplicates numbers from a list.
 Use the fact that sets does not accept duplicates.
 Length of a set remains the same when trying the add
 an already existing element.

find_dups([1,1,2,3,4,2]) {1,2} find_dups([1,2,3,4]) set{}

""" 
elem_set = set()
dups_set = set()
for entry in list:
    len_initial = len(elem_set)
    elem_set.add(entry)
    len_after = len(elem_set)
    if len_initial == len_after:
        dups_set.add(entry)
return(dups_set)