Python String replace() Method

String replace() method returns a copy of the string where occurrences of a substring are replaced with another substring.

In this article, we will see how to replace string in Python.

String replace() Method Syntax

The replace string Python method in Python strings has the following syntax:

string.replace(old, new, count)

Parameters: 

• old – old substring you want to replace.
• new – new substring which would replace the old substring.
• count – (Optional ) the number of times you want to replace the old substring with the new substring. 

Return Value : It returns a copy of the string where all occurrences of a substring are replaced with another substring. 

String replace() Method Example

In this, we will see different examples of Python string replacement.

Example:

Great Morning

1. replace() all Instances of a Single Character in a String

In this example, we are only replacing a single character from a given string. The Python string replacement approach using replace() method is case-sensitive, and therefore it performs a case-sensitive substring substitution, i.e. R in FOR is unchanged.

Example:

grrks FOR grrks
geeks FOR geeks

Time Complexity: O(n)
Space Complexity: O(n)

2. replace() all Instances of a String in a String

Here, we will use Python string replacement approach using replace() to replace all the geeks with GeeksforGeeks using replace() function.

Example:

geeks for geeks 
geeks for geeks
GeeksforGeeks for GeeksforGeeks 
GeeksforGeeks for GeeksforGeeks

Time Complexity: O(m*n)
Space Complexity: O(n)

3. replace() only a Certain Number of Instances in a String

In this example, we will use the Python string replacement approach using replace() replacing certain numbers of words. i.e. “ek” with “a” with count=3.

gaaks for gaaks gaaks gaaks gaaks
geas for geas geas geeks geeks

Time Complexity: O(n)
Space Complexity: O(n)

4. replace() String using a list comprehension and join() method

Here, we will do string replacement without using replace(). First we will split the original string into a list of substrings using the split() method. Then use a list comprehension to replace each occurrence of old_substring with new_substring.

Join the list of substrings back into a string using the join() method.

geexs for geexs 

Time Complexity: O(n)
Space Complexity: O(n)

We have covered the string replace() method in Python. We have seen multiple Python string replace() method examples to completely understand the working of replace() function.

Check other String Methods

Hope this helps you in your Python Journey!