Question

I want to use sets as data structure. how should i make it possible?
what are the commands I need?

Like closedset = set()

is this ok?

And in a set, if i want to get some value out, what is the command for that one?

Answer 1

Correct. To create an empty set, write foo = set(). To retrieve values, you can iterate over the set:

for val in someset:
    print val

You can also write val in someset to check if an item is in a set.

Be sure to read the documentation for how to do set operations.