replace characters in string python

1my_text = 'Aello world'
2my_text = my_text.replace(my_text[0], 'H')
3print (my_text)

1
2# Python3 program to demonstrate the  
3# use of replace() method   
4  
5string = "geeks for geeks geeks geeks geeks" 
6   
7# Prints the string by replacing geeks by Geeks  
8print(string.replace("geeks", "Geeks"))  
9  
10# Prints the string by replacing only 3 occurrence of Geeks   
11print(string.replace("geeks", "GeeksforGeeks", 3)) 

1>>> x = 'xpple bxnxnx cherry'
2>>> a = x.replace(x,a)  # replaces x with a
3'apple banana cherry'
4
5>>> first_a = x.replace(x,a,1)  # only replaces first a
6'apple bxnxnx cherry'

1mytext = 'Hello Zorld'
2mytext = mytext.replace('Z', 'W')
3print mytext,

1>>> a = '&#'
2>>> print a.replace('&', r'\&')
3\&#
4>>> print a.replace('#', r'\#')
5&\#
6>>> 
7