Write a Python program to check whether the n th element exists in a given list

Python: Check whether the n-th element exists in a given list

Last update on October 08 2020 09:22:26 (UTC/GMT +8 hours)

Python | Check for Nth index existence in list

Check if element exists in list in Python

Python Program to check if element exists in list

In this tutorial, we will learn how to check if an element is present in a list or not. List is an ordered set of values enclosed in square brackets [ ]. List stores some values called elements in it, which can be accessed by their particular index. We will be discussing the various approaches by which we can check for an element in the given list.

The program will accept the list and the element which has to check, it should return True if it exists else, it will return False

Input: [6, 22, 7, 3, 0, 11] element= 0

Output: True

Let us look at the different approaches we can follow to execute the task.

(Python Example for Citizen Data Scientist & Business Analyst)

Write a Python program to check whether the n-th element exists in a given list.

Sample Solution

Python Code:

Sample Output:

6

How to Check if Element Exists in List in Python

The list is a crucial container in Python because it is able to store elements of all types of data as a collection. Knowing specific list operations is essential to be able to program day-to-day. This article will discuss one of the most fundamental list operations, which is to verify the existence of the elements on the list.

Method 1: Naive Method

In the Naive approach, one employs a loop to iterate through the entire list of elements to verify whether the element is a target element. This is the most efficient method of determining the presence of the element on the list.

Method 2: Using in

Python is the most common method of determining whether an element is present in a list. This method returns True if the element is present in the list and False if it is not within the set. The list does not need to be sorted in order to use this method of checking.

Code #1: A demonstration of how you can check whether an element is in the list by using the Naive method as well as in.

Output:

Method 3 : Using set() + in

Converting the list to the set and then using the in may make more sense than just making use of in. However, efficiency as a plus has some drawbacks. One of these concerns is that order in which the list is displayed isn't maintained. If you choose to make a list and make a new one, you'll need to make use of additional space. Another issue is that set doesn't allow duplicates, and therefore duplicate elements will be eliminated from the list.

Method 4 : Using sort() + bisect_left()

The traditional binary search method to determine the existence of elements means that list must be sorted first, thus not keeping the order of elements. Bisect_left() will return the very first instance of an element found. It works similarly with lower_bound() in C++ STL.

Note: The bisect function will only give the location of the element but not provide details of whether the element is there or not.

Code #2: Demonstrating to check existence of element in list using set() + in and sort() + bisect_left().

Output:

Method 5 : Using count()

We can make use of the built-in Python List method count() to verify whether the element passed is present in the List. If the element that we passed is in the List, then the count() technique will reveal how many instances it is present throughout the list. If it's a positive number, that means that an element exists within the List.

Code #3: Explaining how to verify the presence of elements on the list by counting().

Output:

How to check if a list is empty in Python?

In this short tutorial, find how to check if a list is empty in Python. We also look at why you need to do this so that you understand the purpose better.