Python Find String in List

Guide

You are working with Python and want to find out if a specific string is contained in a list? Whether it’s searching for keywords, user inputs, or specific data – Python offers several simple and efficient ways to do this.

In this guide, we will walk you through the step-by-step process of checking if a string is present in a list, explore different methods, and help you determine which one best suits your needs. Let’s get started! For your information: We can use Python in operator to check if a string is present in the list or not. There is also a not in operator to check if a string is not present in the list.

l1 = ['A', 'B', 'C', 'D', 'A', 'A', 'C']

# string in the list
if 'A' in l1:
    print('A is present in the list')

# string not in the list
if 'X' not in l1:
    print('X is not present in the list')

Output:

A is present in the list
X is not present in the list

Let’s look at another example where we will ask the user to enter the string to check in the list.

l1 = ['A', 'B', 'C', 'D', 'A', 'A', 'C']
s = input('Please enter a character A-Z:\n')

if s in l1:
    print(f'{s} is present in the list')
else:
    print(f'{s} is not present in the list')

Output:

Please enter a character A-Z:
A
A is present in the list

Python Find String in List using count()

We can also use count() function to get the number of occurrences of a string in the list. If its output is 0, then it means that string is not present in the list.

l1 = ['A', 'B', 'C', 'D', 'A', 'A', 'C']
s = 'A'

count = l1.count(s)
if count > 0:
    print(f'{s} is present in the list for {count} times.')

Finding all indexes of a string in the list

There is no built-in function to get the list of all the indexes of a string in the list. Here is a simple program to get the list of all the indexes where the string is present in the list.

l1 = ['A', 'B', 'C', 'D', 'A', 'A', 'C']
s = 'A'
matched_indexes = []
i = 0
length = len(l1)

while i < length:
    if s == l1[i]:
        matched_indexes.append(i)
    i += 1

print(f'{s} is present in {l1} at indexes {matched_indexes}')

Output:

A is present in ['A', 'B', 'C', 'D', 'A', 'A', 'C'] at indexes [0, 4, 5]

Register now in the ccenter for exclusive access to advanced tutorials and best practices, or contact our sales team for personalized consulting and tailored solutions! Check out our tutorial: Python: Convert String to List to learn about the different methods for efficiently converting a string into a list, when each method is best suited, and how to avoid common mistakes. This will help you deepen your Python knowledge and optimize your data processing.