String replace() in Python 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 Python.
Replace() String Python Syntax
The replace string Python method in Python strings has the following syntax:
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.
Python Replace() String Example
In this, we will see different examples of Python string replacement.
Example
Python3
string = "Good Morning"new_string = string.replace("Good", "Great") print(new_string) |
Output
Great Morning
Python Replace() String all Instances of a Single Character
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.
Python3
string = "grrks FOR grrks" # replace all instances of 'r' (old) with 'e' (new)new_string = string.replace("r", "e" ) print(string)print(new_string) |
Output
grrks FOR grrks
geeks FOR geeks
Time Complexity: O(n)
Space Complexity: O(n)
Python Replace() String all Instances of a String
Here, we will use Python string replacement approach using replace() to replace all the geeks with Lazyroar using replace() function.
Python3
string = "geeks for geeks \ngeeks for geeks" print(string) # Prints the string by replacing only# 3 occurrence of Geeksprint(string.replace("geeks", "Lazyroar")) |
Output
geeks for geeks
geeks for geeks
Lazyroar for Lazyroar
Lazyroar for Lazyroar
Time Complexity: O(m*n)
Space Complexity: O(n)
Python Replace() String only a Certain Number of Instances
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.
Python3
string = "geeks for geeks geeks geeks geeks" # Prints the string by replacing# e by aprint(string.replace("e", "a")) # Prints the string by replacing only# 3 occurrence of ek by aprint(string.replace("ek", "a", 3)) |
Output
gaaks for gaaks gaaks gaaks gaaks
geas for geas geas geeks geeks
Time Complexity: O(n)
Space Complexity: O(n)
Python Replace() String using a list comprehension and join() method
Here, we will Python string replacement approach using replace() to Split the original string into a list of substrings using the split() method. 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.
Python3
my_string = "geeks for geeks "old_substring = "k"new_substring = "x" split_list = my_string.split(old_substring)new_list = [new_substring if i < len(split_list)-1 else '' for i in range(len(split_list)-1)]new_string = ''.join([split_list[i] + new_list[i] for i in range(len(split_list)-1)] + [split_list[-1]]) print(new_string) |
Output
geexs for geexs
Time Complexity: O(n)
Space Complexity: O(n)
