Python - Me ayuden a comprender este codigo.

''' Module to generate max, total and docs json files. '''

import json

import argparse

from os import listdir

from os.path import isfile, join

import math

import sys

TITLE_FIELD = 'title'

WORDS_FIELD = 'words'

def gen_jsons(files):

    ''' Generate max, total and docs files from FILES files array. '''

    max_map = dict()

    total_map = dict()

    docs_map = dict()

    docs_count = 0

    for filename in files:

        f = open(filename, 'r')

        # each document

        docs = f.readlines()

        doc = docs[0:3]

        i = 3

        while i <= len(docs):

            content = doc[2]

            words = content.split(' ')[:-1] # omit \n char

            doc_id = doc[0][:-1] # omit \n char

            docs_map[doc_id] = dict() # add doc entry

            docs_map[doc_id][TITLE_FIELD] = doc[1][:-1] # add title entry, omit \n char

            docs_map[doc_id][WORDS_FIELD] = dict() # add words entry

            doc_words = docs_map[doc_id][WORDS_FIELD]

            for word in words:

                doc_words[word] = doc_words.get(word, 0) + 1

            for word in doc_words:

                doc_words[word] = doc_words[word] / float(len(doc_words))

                total_map[word] = total_map.get(word, 0) + 1 # add to total docs with  word

            doc = docs[i:i + 3]

            i += 3

            docs_count += 1

        f.close()

    for doc in docs_map:

        words = docs_map[doc][WORDS_FIELD]

        for word in words:

            words[word] = words[word] * math.log(docs_count / total_map[word])

            max_map[word] = words[word] if words[word] > max_map.get(word, -sys.maxint) else\

                max_map[word]

    for doc in docs_map:

        words = docs_map[doc][WORDS_FIELD]

        norm = 0.0

        for word in words:

            norm += math.pow(words[word], 2)

        docs_map[doc]['norm'] = math.pow(norm, 0.5)

    docs_str = json.dumps(docs_map)

    total_str = json.dumps(total_map)

    max_str = json.dumps(max_map)

    docs_file = open('docs.json', 'w')

    total_file = open('total.json', 'w')

    max_file = open('max.json', 'w')

    docs_file.write(docs_str)

    total_file.write(total_str)

    max_file.write(max_str)

    docs_file.close()

    total_file.close()

    max_file.close()

def main():

    ''' Main function. '''

    parser = argparse.ArgumentParser(description='Generate json files.')

    parser.add_argument('paths', metavar='path', type=str, nargs='+',

                        help='a path to directories or files')

    parser.add_argument('--dir', '-d', dest='directories', action='store_const',

                        const=True, default=False,

                        help='paths are directories (default: paths are files)')

    args = parser.parse_args()

    files = []

    if args.directories:

        # directories

        for path in args.paths:

            files = [join(path, f) for f in listdir(path) if isfile(join(path, f))]

    else:

        # files

        for path in args.paths:

            if isfile(path):

                files.append(path)

    gen_jsons(files)

if __name__ == "__main__":

    main()