Data Structures

Sets

Sets allow you to accumulate items without duplicates. A set begins and ends with curly braces {} and each item is separated by a comma ,

Spaces don't matter here.

a = { 1, 1, 2, 1, 2, 2 }

Note that even though we've added multiple instances of 1 and 2, the set object only contains a single instance of 1 and 2.

>>> print(a)
{1, 2}

Alternate syntax

Unfortunately, Python also uses curly braces {} to define sets and dictionaries. The following will create an empty dictionary

a = {}

To create an empty set, you need to use the set() function without any arguments

a = set()

Set operations

The set data type supports many conventional set operations. You can find the union, intersection, and difference between two sets using the following methods

a = { 1, 2, 3, 4, 5 }
b = { 1, 5, 6, 7, 8 }
a.intersection(b)       # intersection
a.difference(b)         # difference
a.union(b)              # union

Adding and removing items

You can add and remove items from a set using the add and remove methods

a.add(10)
a.remove(2)

Indexing

Sets, which are inherently unordered collections, do not support indexing.