Think Python - Denison University

128 Chapter 13. Casestudy: datastructure selection13.4 MostcommonwordsTo find the most common words, we can apply the DSU pattern; most_common takes a histogramand returns alistofword-frequency tuples, sortedinreverse order by frequency:def most_common(h):t = []for key, value in h.items():t.append((value, key))t.sort(reverse=True)return tHere isaloop that printsthe tenmost common words:t = most_common(hist)print 'The most common words are:'for freq, word in t[0:10]:print word, '\t', freqAnd here aretheresultsfrom Emma:The most common words are:to 5242the 5204and 4897of 4293i 3191a 3130it 2529her 2483was 2400she 236413.5 Optional parametersWehaveseenbuilt-infunctionsandmethodsthattakeavariablenumberofarguments. Itispossibleto write user-defined functions with optional arguments, too. For example, here is a function thatprintsthe most common words inahistogramdef print_most_common(hist, num=10):t = most_common(hist)print 'The most common words are:'for freq, word in t[0:num]:print word, '\t', freqThe firstparameter is required; the second isoptional. The default value ofnumis10.Ifyou only provide one argument:print_most_common(hist)