Zero Division Error

[moga2003]

Good evening,
For my project, I keep getting a Zero Division error when trying to calculate the score below. I can't seem to figure out exactly what I am doing incorrectly. The code snippet is below. Any help would be greatly appreciated.

Thank you.

 
@property
    def positivity(self):
        """"A positivity score calculated as follows:
            Create local tally variable with initial value of 0.
            Increment tally by 1 for every word in self.words found in positive.txt (in same directory)
            Decrement tally by 1 for every word in self.words found in negative.txt (in same directory)
            Calculate score as follows: 
            round( tally / self.word_count * 1000)"""
        tally = 0
        words = self._words()
        neg_word_list = re.findall(r'^\w+', 'negative.txt')
        pos_word_list = re.findall(r'^\w+', 'positive.txt')
        for item in words:
            if item in pos_word_list: tally = tally + 1
            if item in neg_word_list: tally = tally -1
        return (round(tally / self.word_count * 1000)) 

Error:
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-52-5bbe8bf0ab1a> in <module>()
    226 print("distinct_word_count", ta.distinct_word_count)
    227 #print("avg_word_length", ta.avg_word_length)
--> 228 print("positivity", ta.positivity)
    229 print(ta.common_words(minlen=5, maxlen=10))
    230 print("plot", ta.plot_common_words(minlen=5, maxlen=10))

<ipython-input-52-5bbe8bf0ab1a> in positivity(self)
    198             if item in pos_word_list: tally = tally + 1
    199             if item in neg_word_list: tally = tally -1
--> 200         return (round(tally / self.word_count * 1000))
    201 
    202 

ZeroDivisionError: division by zero