Word count class

#!/usr/bin/python2


"""Object-based word count demonstration"""


import sys
import collections
import csv
import re


class WordCount(object):
    """Count of words in a text

    Attributes:
    counts -- collections.Counter of words
    """
    def __init__(self, counts):
        """Intializes a WordCount

        Do not call directly, use WordCount.fromfile or WordCount.fromstring
        instead
        """
        self.counts = counts

    @classmethod
    def fromfile(cls, filename):
        """Creates a WordCount for the given file"""
        with open(filename, 'r') as infile:
            text = infile.read()
        return cls.fromstring(text)

    @classmethod
    def fromstring(cls, text):
        """Creates a WordCount for the given string"""
        wordlist = re.findall(r'\w+', text)
        counts = collections.Counter(wordlist)
        return cls(counts)

    @property
    def ordered(self):
        """List of (word, count) tuples in descending frequency"""
        items = self.counts.items()
        items.sort(key=lambda (word, count): (-count, word))
        return items

    def to_csv(self, filename):
        """Writes the ordered counts to file"""
        with open(filename, 'w') as outfile:
            writer = csv.writer(outfile)
            writer.writerows(self.ordered)



def main():
    """Counts words (and numbers) in a file"""
    try:
        infilename, outfilename = sys.argv[1:3]
    except IndexError:
        print "Usage: %s INFILE.txt OUTFILE.csv" % sys.argv[0]
        sys.exit(1)
    count = WordCount.fromfile(infilename)
    count.to_csv(outfilename)


if __name__ == '__main__':
    main()