Convert List to Set Python

Introduction

• Data structure offers a method for effectively managing, organizing, and storing data.
• Data structures make it simple to navigate the data elements. Data structures offer productivity, reuse, and abstraction.
• We can think of lists as a box containing a finite number of elements. Similarly, a set can be considered a box where no duplicate elements are allowed.
• In the example below, we can see a list ([10, 50, 10, 70, 10, 50, 20, 70]) getting converted into a list, which comprises only the unique elements of the list.
• A list allows any number of variables in it, but a set doesn't allow duplicates.
• A compelling use case of sets is when we are given a list and have to return only the unique elements.
• A list looks something like this:

• A set looks something like this:

• The most striking difference between a list and a set is list is represented by [], whereas a set is represented by {}.
• Hence, this article will unravel the methods of converting lists into sets.

Method 1: Using the set() function to convert the list to a set in Python

• The set() function will help us to convert a list to a set.
• The order of the set would be different, as a set displays the items in random order. Syntax:

Example:

Output

As you can see, the set only contains unique elements from the list.

Note: A list can contain any data type; it can be a list of strings, integers, floats, etc.

Method 2: Using for-loop to convert list to set in Python

• In this technique, we access each list element using Python's for-loop method before adding it to a set using the add() function. Syntax:

The set automatically handles the repeated values.

Output

Method 4: Using Set comprehension to convert a list to set

• Set Comprehension is a method in Python from which we can generate sets in a single line.
• In Python, comprehensions are used to create new sequences from existing ones. You can read more about comprehension here
• Programmers use set comprehension when creating an extra/dummy set in their code.
• In set comprehension, we use an in-place for loop to convert a list into a set.

Output:

Time Complexity to convert list to set

• The general time complexity to convert a list into a set is O(N), where $N$ represents the number of elements in the list. A question might arise as to how we know if the available time complexity is O(N). We'll figure it out!
• The time complexity in a set to add/delete elements is O(1). Assuming the number of elements in our list to be $N$, we'd have to traverse every element in the list.
• Hence, the time complexity will be calculated as follows:

• The execution time of these 4 methods are compared below:

  Method	Execution Time
  Set Comprehension	0.00018
  Using set()	0.00016
  Using for-loop	0.00019
  Using dictionary	0.00021

Similar Topics

• What are lists in Python?
• What are sets in Python?
• Difference between dictionaries, list, tuple, and set.