[Tutor] problem writing random_word function

[Matt Smith]

Hi,
I'm attempting to write a function that returns a random word of a
specified length for use in a hangman game.  The source of the words is a
text file with each word on a new line.  I got the function working
printing all of the words of the desired length.  I now want to make a
list of all the words of the correct length then pick a random item from
the list.  Here is the function and traceback:

def random_word(word_length):
    """Returns a random word of length word_length"""
    import random
    f = open("hangman_words.txt","r")
    while 1:
        n = 0
        text = f.readline()
        text = text[0:len(text)-2]
        if len(text) == word_length:
            word_list[n] = text
            n = n+1
    f.close()
    return word_list[random.randint(0,n)]

Traceback (most recent call last):
  File "/home/matt/hangman.py", line 15, in -toplevel-
    print random_word(5)
  File "/home/matt/hangman.py", line 9, in random_word
    word_list[n] = text
NameError: global name 'word_list' is not defined

Hope you can help,
Matt.