source_list = ['one', 'two', 'three', 'four', 'five']
diff_list = ['zero', 'one', 'two', 'three', 'four', 'six', 'seven']
print('Unique elements in source_list: {0}'.format(set(source_list) - set(
    diff_list)))
print('Unique elements in diff_list: {0}'.format(set(diff_list) - set(
    source_list)))
Efficient way to compare two lists remembering the origin for every unique element