how to change elements of a string in python

string.replace(old, new, count)

# Python3 program to demonstrate the  
# use of replace() method   
  
string = "geeks for geeks geeks geeks geeks" 
   
# Prints the string by replacing geeks by Geeks  
print(string.replace("geeks", "Geeks"))  
  
# Prints the string by replacing only 3 occurrence of Geeks   
print(string.replace("geeks", "GeeksforGeeks", 3))