Python Set update()

1. Overview

The Python set update() method updates the set, adding items from other iterables.

The syntax of update() is:

A.update(iterable)

Here, A is a set, and iterable can be any iterable such as list, set, dictionary, string, etc. The elements of the iterable are added to the set A.

Let’s take another example:

A.update(iter1, iter2, iter3)

Here, the elements of iterables iter1, iter2, and iter3 are added to set A.

2. Return Value from update()

This set update() method returns None (returns nothing).

2.1. Example 1: Python set update()

A = {'a', 'b'}
B = {1, 2, 3}

result = A.update(B)

print('A =', A)
print('result =', result)

Output

A = {'a', 1, 2, 3, 'b'}
result = None

2.2. Example 2: Add elements of string and dictionary to Set

string_alphabet = 'abc'
numbers_set = {1, 2}

# add elements of the string to the set
numbers_set.update(string_alphabet)

print('numbers_set =', numbers_set)

info_dictionary = {'key': 1, 'lock' : 2}
numbers_set = {'a', 'b'}

# add keys of dictionary to the set
numbers_set.update(info_dictionary)
print('numbers_set =', numbers_set)

Output

numbers_set = {'c', 1, 2, 'b', 'a'}
numbers_set = {'key', 'b', 'lock', 'a'}

Note: If dictionaries are passed to the update() method, the keys of the dictionaries are added to the set.