Check if list index exist python

Checking if List Index Exists Using Exception Handling in Python

You can also check if an index exists using exception handling. When we try to access an element of a list with an index that is out of bounds, we will generate an IndexError.

Therefore, to check if a list index exists or not, we can see if our code raises an error when we try to access an element at a certain index.

Below is a Python function which uses exception handling to see if an index exists in a list.

def indexExists(list,index): try: list[index] return True except IndexError: return False print(indexExists([0,1,2,3,4,5],3)) print(indexExists(["This","is","a","list"],10)) #Output: True False

Hopefully this article has been useful for you to understand how to check if a list index exists in Python.

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Python – Check If Index Exists in List

Lists are a very versatile data structure in Python that is used to store an ordered collection. In this tutorial, we will look at how to check if an index exists in a list or not.

Lists are mutable, so you can perform operations like adding elements, removing elements, extending a list, etc. The values in a list are indexed starting from zero and we can use a value’s index in the list to access it.

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How to check if an index exists in a list?

A Python list uses integer values starting from zero as its index. So, the first element in the list will have index 0 and the last element in the list has an index equal to the length of the list – 1 (one less than the length of the list).

If the index under consideration is less than the length of the list, we can say that the index exists in the list. The following is the syntax –

We use the Python built-in len() function to get the length of a list. Here, we get True if the index exists in the list and False otherwise.

There are other methods as well that you can use to check if an index exists in a list or not. For example –

• Using try and except blocks. First, try to access the list value at the index under consideration inside a try block and use an except block to catch an IndexError . If the index exists in the list, no errors will be raised. If the index doesn’t exist, an IndexError is raised which will be handled by the except block (see the examples below).

Examples

Let’s look at some examples of using the above methods.

Example 1 – Check if an index exists using the list length

Let’s create a list and check if a valid index exists or not.

# create a list ls = ['milk', 'eggs', 'bread'] i = 2 # check if index i is present in the list print(i < len(ls))

Here, we created a list of length 3 and checked for the index 2. You can see that we get True as the output as the index 2 exists.

Let’s now access an index that does not exist.

# check if index 3 is present in the list print(3 < len(ls))

We get False as the output.

What if the list is empty? Let’s find out.

# create an empty list ls = [] # check if index 0 is present in the list print(0 < len(ls))

Here, we created an empty list and checked if the index 0 is present. We get False as the output.

Example – Check if an index exists using try – except

Alternatively, we can use error handling to check if an index exists in the list or not.

The idea is to try to access the list value at the given index inside a try block, now if the index exists, no errors will be raised but if the index does not exist, an IndexError gets raised which can be handled by an except block.

# create a list ls = ['milk', 'eggs', 'bread'] i = 3 # check if index i is present in the list try: ls[i] print("Index present") except IndexError: print("Index not present")

Here, we tried accessing the element at index 3 in a list with three values. Now, since index 3 does not exist, an IndexError got raised which was then handled by the except block. Thus, you can see the result, “Index does not exist”.

Summary

In this tutorial, we looked at some methods to check if an index exists in a Python list or not. The following are the key takeaways –

• If the index is less than the length of the list you can say that the index exists in the list.
• Alternatively, you can use error handling to check if an index exists or not. If an IndexError gets raised on trying to access the value at the given index, you can say that the index does not exist.

You might also be interested in –

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Piyush is a data professional passionate about using data to understand things better and make informed decisions. He has experience working as a Data Scientist in the consulting domain and holds an engineering degree from IIT Roorkee. His hobbies include watching cricket, reading, and working on side projects. View all posts

Data Science Parichay is an educational website offering easy-to-understand tutorials on topics in Data Science with the help of clear and fun examples.

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Check if List Index Exists in Python (2 Examples)

Hi there! In this tutorial, I will show you 2 ways of checking if a list index exists in Python.

First, here is a quick overview of this tutorial:

Create Python List

Let us create a simple Python list of animals.

animals = ["dog", "goat", "cow", "sheep", "rabbit"]

Example 1: Use Python’s len() Function

In this example, we will use the Python len() function to check if the list index exists.

index = 4 print(index  len(animals)) # True

What we have done is to check if the index number is less than the length of the list.

If yes, then it will print out the boolean value True, which indicates that the index does exist in the list. But if the index is greater than the length of the list, then it will print out False, which means that the index does not exist in the list.

Example 2: Use “try” and “except” Blocks

In this second example, we are going to use the Python try and except blocks. If the index exists in the list, no error will be raised; but if the index does not exist in the list, then an index error will be raised.

animals = ["dog", "goat", "cow", "sheep", "rabbit"] index = 4

try: animals[index] print("Index exists") except IndexError: print("Index doesn't exist") # Index exists

Let’s now adjust the index to 5, and see the output of the program.

animals = ["dog", "goat", "cow", "sheep", "rabbit"] index = 5

try: animals[index] print("Index exists") except IndexError: print("Index doesn't exist") # Index doesn't exist

This raises an error because index number 5 is greater than the index of the last element in the list. Remember, Python indexing starts at 0!

That is how to check if a list index exists in Python. Hope you found this helpful!

Video, Further Resources & Summary

Do you need more explanations on how to check if a list index exists in Python? Then you should have a look at the following YouTube video of the Statistics Globe YouTube channel.

In the video, we explain in some more detail how to check if a list index exists in Python.

The YouTube video will be added soon.

Furthermore, I encourage you to check out other interesting Python list tutorials on Statistics Globe, starting with these ones:

This post has shown how to check if a list index exists in Python. In case you have further questions, you may leave a comment below.

This page was created in collaboration with Ifeanyi Idiaye. You might check out Ifeanyi’s personal author page to read more about his academic background and the other articles he has written for the Statistics Globe website.

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Check if Index Exists in Python List

1. Check if Index Exists in Python List Using the List Range
2. Check if Index Exists in Python List Using The IndexError

We will introduce two methods to check if a list index exists using the list range and the IndexError exception.

Check if Index Exists in Python List Using the List Range

We will have to check if the index exists in the range of 0 and the length of the list.

fruit_list = ['Apple','Banana','Pineapple']  for index in range(0,5):  if 0  index  len(fruit_list):  print("Index ",index ," in range")  else:  print("Index ",index," not in range") 

Index 0 in range Index 1 in range Index 2 in range Index 3 not in range Index 4 not in range 

Check if Index Exists in Python List Using The IndexError

When we try to access an index that does not exist in a list, it will raise an IndexError exception.

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