class ABC(object):

    def __init__(self, query = None, cands = None):
        if query != None and cands != None:
           self.query = query
           self.cands = cands
           self.getIDF()


    def getIDF(self):
        self.i_dict = {}
        for term in query:
            count = 0
            for cand in cands:
                if term in cand:
                    count += 1
            self.i_dict[term] = count

NameError: name 'query' is not defined