I am trying to see if a company from a list of companies is in a line in a file. If it is I utilize the index of that company to increment a variable in another array. The following is my python code. I keep getting the following error: AttributeError: 'set' object has no attribute 'index'. I cannot figure out what is going wrong and think the error is the line that is surrounded by **.

companies={'white house black market', 'macy','nordstrom','filene','walmart'}
positives=[0 for x in xrange(len(companies))]
negatives=[0 for x in xrange(len(companies))]

for line in f:
    for company in companies:
        if company in line.lower():
            words=tokenize.word_tokenize(line)
            bag=bag_of_words(words)
            classif=classifier.classify(bag)
            if classif=='pos':
                **indice =companies.index(company)**
                positives[indice]+=1
            elif classif=='neg':
                **indice =companies.index(company)**
                negatives[indice]+=1