What to fix about it? Looks good to me. You could use f-strings (introduced in Python 3.6) to get rid of the `.format(`. https://www.python.org/dev/peps/pep-04

What to fix about it? Looks good to me. You could use f-strings (introduced in Python 3.6) to get rid of the `.format(`. https://www.python.org/dev/peps/pep-0498/ https://www.python.org/dev/peps/pep-0498/ The `[str(value) for value in flatten(vertex)]` part is missing in your Ruby. I assume that happens in some method of the vertex? You could make your vertex iterable as well. Python philosophy prevents you from getting rid of the `str(x) for x in v` because "explicit is better than implicit", so join will not auto-convert stuff into strings.