Method # 1: Using split () + join ()
This is one way we can accomplish this task. In this, we break the elements apart and then return the last value and add a new element using join ().

# Python3 code to demonstrate how it works # Replace the trailing word in the line # using split () + join ()   # initialization string test_str = " GFG is good "    # print original line print ( "The original string is:" + test_str)    # initialize string replacement rep_str = "best"   # Replace the backword in the line # using split () + join () res =   "" . join (test_str.split ( `` ) [: - 1 ] + [rep_str ])   # print result print ( "The String after performing replace:" + res)

Output:

 The original string is: GFG is good The String after performing replace: GFG is best 

Method # 2: Using rfind () + join ()
A combination of these functions can also be used to accomplish this task. In this we perform the task of extracting the last word of a string using rfind () and join () is used to perform the replacement.

# Python3 code to demonstrate how it works # Replace the backword in the line # using rfind () + join ()   # initialization string test_str = " GFG is good "    # print original line print ( "The original string is:" + test_str)    # initialize string replacement rep_str = "best"   # Replace the backword in the line # using rfind () + join () res = test_str [: test_str.rfind ( ` ` )] + ` ` + rep_str   # print result print ( "The String after performing replace:" + res)

Output:

 The original string is: GFG is good The String after replace: GFG is best performing