SETS

A set is an unordered collection that does not contain duplicate elements. Use curly braces or the set() function to create sets. Set objects support set-theoretic operations such as union, intersection, and difference.

NOTE

set() is required in order to create an empty set because {} creates an empty dictionary.

The following code snippets illustrate how to work with a set.

Create a list of elements:

>>> l = ['a', 'b', 'a', 'c']

Create a set from the preceding list:

>>> s = set(l)

>>> s

set(['a', 'c', 'b'])

Test if an element is in the set:

>>> 'a' in s

True

>>> 'd' in s

False

>>>

Create a set from a string:

>>> n = set('abacad')

>>> n

set(['a', 'c', 'b', 'd'])

>>>

Subtract n from s:

>>> s - n

set([])

Subtract s from n:

>>> n - s

set([&apos...