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Replace a String character at given index in Python

Find position of a character in given string – Python

Last Updated : 30 Apr, 2025

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Given a string and a character, our task is to find the first position of the occurrence of the character in the string using Python. For example, consider a string s = “Geeks” and character k = ‘e’, in the string s, the first occurrence of the character ‘e’ is at index1. Let’s look at various methods of solving this problem:

Using Regular Expressions (re.search())

Regex (Regular Expressions) are patterns used to match sequences in text. With re.search(), we can find the first match of a pattern and get its position.

[GFGTABS]
Python

import re  s = 'Geeksforgeeks' k = 'for'  match = re.search(k, s) print("starting index", match.start()) print("start and end index", match.span())

[/GFGTABS]

Output

starting index 5 start and end index (5, 8)

Explanation:

re.search() returns the first match of the pattern.
.start() gives the index of the first character.
.span() gives a tuple (start, end) of the matched portion.

Using index()

The index() method returns the index of the first occurrence of a character. If not found, it raises a ValueError.

[GFGTABS]
Python

s = 'xyze' k = 'b'  try:     pos = s.index(k)     print(pos) except ValueError:     print(-1)

[/GFGTABS]

Output

-1

Explanation:

index() finds the first occurrence and returns its index.
If the character isn’t found, it raises an error-handled using try-except.

Using a Loop

We can also manually loop through the string to find the first match.

[GFGTABS]
Python

s = 'GeeksforGeeks' k = 'o'  res = -1 for i in range(len(s)):     if s[i] == k:         res = i         break  print(res)

[/GFGTABS]

Output

Explanation:

Loop checks each character.
If matched, it returns the index and exits early with break.

Using find()

find() method returns the index of the first match. If not found, it returns -1.

[GFGTABS]
Python

s1 = 'abcdef' s2 = 'xyze' k = 'b'  print(s1.find(k))   print(s2.find(k))

[/GFGTABS]

Output

1 -1

Explanation:

find() returns index of the first match.
If no match is found, it returns -1 instead of raising an error.

Using enumerate() with next()

This approach uses list comprehension and lazy evaluation to get the first index where the character matches.

[GFGTABS]
Python

def find_pos(s, k):     try:         return next(i for i, c in enumerate(s) if c == k)     except StopIteration:         return -1  s = 'xybze' k = 'b' print(find_pos(s, k))

[/GFGTABS]

Output

Explanation:

enumerate() gives index-character pairs.
next() returns the first matching index.
If not found, StopIteration is caught and -1 is returned.

Related articles:

rfind() method

re.search() method

enumerate() method

next()

Replace a String character at given index in Python

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