What's the difference between fronzensets/sets and what are their advantages/disadvantages?
Frozenset is immutable. Once created you cannot add/remove elements from it. This means that they can be used as keys in dictionaries etc. and in any other place where you would like an object to be hashable. A common practise is to be working with a set while constructing it, and if at any point you know it will no longer change - freeze it for a guarantee of it really not happening.