nameerror: name '--' is not defined

[nadiyaz]

hi, i was given a code to count the words in a paragraph, but i keep getting "NameError: name 'mobypara' is not defined" every time i run it (mobypara is the name of the paragraph).
i made sure the code and the paragraph are both saved in the same file, but that didn't change anything.

here is the code:

def countWords(filename):
    counts = {}
    inf = open(filename, 'r')
    for line in inf:
        words = line.split()
        for word in words:
            if word in counts:
                counts[word] += 1
            else:
                counts[word] = 1
    return counts

that's my input:

countWords(mobypara.txt)

and that's the output:

Traceback (most recent call last):

File "<ipython-input-3-2217261c2031>", line 1, in <module>
countWords(mobypara.txt)

NameError: name 'mobypara' is not defined

any idea what's wrong?
thanks
nadi