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Python Find String in List – Guide

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]

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