how to do a echo function to a file's last word in python

The detailed question is : Write a function that takes a single string representing a filename as an argument and a number, x. Open the file and use a while loop to build and return a string containing the phrase from the file and the last word x times. Note the new lines.

def echo(filename, x):
    """
    >>> echo("phrase.txt", 2)
    'Hello World!\\nWorld!\\nWorld!\\n'
    >>> echo("phrase.txt", 4)
    'Hello World!\\nWorld!\\nWorld!\\nWorld!\\nWorld!\\n'
    """

if __name__=="__main__":
    import doctest
    doctest.testmod(verbose=True)

what Im trying to do is:

def echo(filename,x):
    files=open(filename,"r")
    text=files.read()
    filelist=text.split()
    last_word=filelist[len(filelist)-1]
    n=len(last_word)
    count=last_word
    while n<n*x:
        count=count+last_word
        n=n+1
    return count   

but unfortunately, this is not gonna work. as a new fish who still struggling in python, I really need somebody to give me a hand.