Replace substring in list of strings – Python

Last Updated : 22 Apr, 2025

We are given a list of strings, and our task is to replace a specific substring within each string with a new substring. This is useful when modifying text data in bulk. For example, given a = [“hello world”, “world of code”, “worldwide”], replacing “world” with “universe” should result in [“hello universe”, “universe of code”, “universewide”]. Let’s discuss different methods to do this in Python.

Using List Comprehension with replace()

replace() method replaces occurrences of a substring in a string. Using list comprehension, we can apply it to every string in the list efficiently.

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Python



a = ["hello world", "world of code", "worldwide"]  
old_substring = "world"  
new_substring = "universe"  

res = [s.replace(old_substring, new_substring) for s in a]  
print(res)

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Output

['hello universe', 'universe of code', 'universewide']

Explanation:

The replace() function replaces all occurrences of “world” with “universe” in each string.
List comprehension iterates through the list and applies replace() to every string.

Using map()

map() function applies replace() to each string in the list without using explicit loops.

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Python



a = ["hello world", "world of code", "worldwide"]  
s1 = "world"  
s2 = "universe"  

res = list(map(lambda s: s.replace(s1, s2), a))  
print(res)

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Output

['hello universe', 'universe of code', 'universewide']

Explanation:

map() applies the replace() function to each string in a.
The lambda function takes each string and replaces “world” with “universe”.
list(map(…)) ensures that the result is stored as a list.

Using for Loop and replace()

A for loop allows modifying the list step by step, storing results in a new list.

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Python



a = ["hello world", "world of code", "worldwide"]  
s1 = "world"  
s2 = "universe"  

res = []  
for s in a:  
    s3 = s.replace(s1, s2) 
    res.append(s3)  

print(res)

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Output

['hello universe', 'universe of code', 'universewide']

Explanation:

The for loop iterates over each string in a.
s.replace(s1, s2) replaces “world” with “universe” in each string.
The modified string is stored in result using append().

Using re.sub() for Pattern-Based Replacement

re.sub() function allows replacing substrings based on patterns.

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Python



import re  

a = ["hello world", "world of code", "worldwide"]  
s1 = "world"  
s2 = "universe"  

res = [re.sub(s1, s2, s) for s in a]  
print(res)

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Output

['hello universe', 'universe of code', 'universewide']

Explanation:

re.sub(pattern, replacement, string) replaces “world” with “universe” in each string.
This method is useful when replacing text based on complex patterns rather than exact substrings.

Using str.translate()

If replacing single characters instead of substrings, str.translate() is a faster alternative.

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Python



a = ["hello world", "world of code", "worldwide"]  

trans_table = str.maketrans("o", "0")  

res = [s.translate(trans_table) for s in a]  
print(res)

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Output

['hell0 w0rld', 'w0rld 0f c0de', 'w0rldwide']

Explanation:

str.maketrans(“o”, “0”) creates a mapping to replace “o” with “0”.
s.translate(trans_table) applies this mapping to each string in a.
This method is limited to character replacements rather than full substrings.

Related Articles:

Python Lists

Python String

List Comprehension in Python

Python String replace() Method

Python map() function

Python For Loops

re.sub() – Python RegEx

Python String translate() Method