This is because the start argument defaults to 0. It doesn't make sense to add a list and 0. The same thing does not work for a sequence of strings and an empt

This is because the start argument defaults to 0. It doesn't make sense to add a list and 0. The same thing does not work for a sequence of strings and an empty string. sum(["abc","def"], "") Throws TypeError: sum() can't sum strings [use ''.join(seq) instead]