Find duplicated elements in a python list

This is a pretty neat python snippet to find duplicated elements in a list:

def find_duplicates(my_list):
  my_set = set()
  tmp = seen.add
  duplicates = set( x for x in my_list if x in my_set or tmp(x) )
  return list( duplicates )

Try it:

my_list = [1234, 456, 1234, 678, 'abc', 'abc', 'abc']
find_duplicates(my_list) # should be [1234, 'abc']