Remove non-unique elements from list

remove_non_unique_values_from_list.py

def remove_non_unique_values(test):
    return [el for el in test if test.count(el) > 1]

if __name__ == '__main__':
    list_1 = [1, 2, 3, 1, 3]
    list_2 = [1, 2, 3, 4, 5]
    list_3 = [5, 5, 5, 5, 5]
    list_4 = [10, 9, 10, 10, 9, 8]
    print "===="
    print "Input >> Output"
    for test_list in [list_1, list_2, list_3, list_4]:
        print "{0} >> {1}".format(test_list,
                                  remove_non_unique_values(test_list))
    print "===="