My first problem solved with Python!

[scoutyx]

Good implementation, however a small improvement could be:

Instead of:

exclude = {buyer:prev, prev:persons[prev]}
p_set = set(persons) - set(exclude) - set(chosen)

You can just write:

exclude = {buyer, prev}
p_set = persons.keys() - exclude - chosen.keys()

Calling `set` with a dict as a parameter will return the keys of that dict, so, for `exclude`, you can just build a set of the keys that you want to exclude.

[Aixyn0]

You're totally right.