Sets are unordered collections of hashable objects; in other words, each object is unique. Sets are commonly used to see if a collection of objects contains a particular item, remove duplicates from a sequence, and compute a variety of mathematical operations.
Sets look like dictionaries, in that curly braces {} are used to create a set. However, unlike dictionaries, sets only have values; there are no key names within a set.
The following example shows how to create a set:
knights_set = {"Sir Galahad", "Sir Lancelot", "Sir Robin"}
Sets are also like dictionaries in that the objects they contain are unordered, and it is likely that calling a set will show a different order of objects compared to what was originally set.
There are actually two types of sets: set and frozenset. A regular set is mutable, in that it can be modified in-place. A frozenset is immutable and cannot be altered after creation. Therefore, a frozenset can be used as a dictionary key, like a tuple, but a regular set cannot.
Set-specific operations are covered in Set methods, though they can utilize many of the sequence methods listed in Sequence methods.