Python – Append Multiple elements in set

In Python, sets are an unordered and mutable collection of data type what does not contains any duplicate elements. In this article, we will learn how to append multiple elements in the set at once.

Example:

Input: test_set = {6, 4, 2, 7, 9}, up_ele = [1, 5, 10]
Output: {1, 2, 4, 5, 6, 7, 9, 10}
Explanation: All elements are updated and reordered. (5 at 3rd position).
 
Input: test_set = {6, 4, 2, 7, 9}, up_ele = [1, 5, 8]
Output: {1, 2, 4, 5, 6, 7, 8, 9, 10}
Explanation: All elements are updated and reordered. (8 at 7th position).

Append Multiple Elements in Set in Python

There are various ways by which we can append elements given in a list to a Set in Python. They are as follows:

Using update() Method

In this method, we will use Python‘s in-built set update() function to get all the elements in the list aligned with the existing set.

Output:

The original set is : {2, 4, 6, 7, 9}
Set after adding elements : {1, 2, 4, 5, 6, 7, 9, 10}

Using | Operator (Pipe Operator)

The pipe operator internally calls the union() function, which can be used to perform the task of updating the Python set with new elements. 

Output:

The original set is : {2, 4, 6, 7, 9}
Set after adding elements : {1, 2, 4, 5, 6, 7, 9, 10}

Using List Comprehension

Here, we will use the Python list comprehension method to append only those elements in a set that are not already present in it. Then we use the set() constructor to convert the list to a Python set.

Output:

The original set is : [2, 4, 6, 7, 9]
Set after adding elements : {1, 2, 4, 5, 6, 7, 9, 10}

Using reduce() Method

This approach uses the reduce() function from the functools module to apply a union operation between each element of a list and the set, resulting in a new set in Python. The reduce() function takes a lambda function and the union() function

Output:

The original list is : {2, 4, 6, 7, 9}
Set after adding elements : {1, 2, 4, 5, 6, 7, 9, 10}