wikirandom.py

# wikirandom.py: Functions for downloading random articles from Wikipedia
#
# Copyright (C) 2010  Matthew D. Hoffman
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import sys, urllib2, re, string, time, threading

def get_random_wikipedia_article():
    """
    Downloads a randomly selected Wikipedia article (via
    http://en.wikipedia.org/wiki/Special:Random) and strips out (most
    of) the formatting, links, etc. 

    This function is a bit simpler and less robust than the code that
    was used for the experiments in "Online VB for LDA."
    """
    failed = True
    while failed:
        articletitle = None
        failed = False
        try:
            req = urllib2.Request('http://en.wikipedia.org/wiki/Special:Random',
                                  None, { 'User-Agent' : 'x'})
            f = urllib2.urlopen(req)
            while not articletitle:
                line = f.readline()
                result = re.search(r'title="Edit this page" href="/w/index.php\?title=(.*)\&amp;action=edit" /\>', line)
                if (result):
                    articletitle = result.group(1)
                    break
                elif (len(line) < 1):
                    sys.exit(1)

            req = urllib2.Request('http://en.wikipedia.org/w/index.php?title=Special:Export/%s&action=submit' \
                                      % (articletitle),
                                  None, { 'User-Agent' : 'x'})
            f = urllib2.urlopen(req)
            all = f.read()
        except (urllib2.HTTPError, urllib2.URLError):
            print 'oops. there was a failure downloading %s. retrying...' \
                % articletitle
            failed = True
            continue
        print 'downloaded %s. parsing...' % articletitle

        try:
            all = re.search(r'<text.*?>(.*)</text', all, flags=re.DOTALL).group(1)
            all = re.sub(r'\n', ' ', all)
            all = re.sub(r'\{\{.*?\}\}', r'', all)
            all = re.sub(r'\[\[Category:.*', '', all)
            all = re.sub(r'==\s*[Ss]ource\s*==.*', '', all)
            all = re.sub(r'==\s*[Rr]eferences\s*==.*', '', all)
            all = re.sub(r'==\s*[Ee]xternal [Ll]inks\s*==.*', '', all)
            all = re.sub(r'==\s*[Ee]xternal [Ll]inks and [Rr]eferences==\s*', '', all)
            all = re.sub(r'==\s*[Ss]ee [Aa]lso\s*==.*', '', all)
            all = re.sub(r'http://[^\s]*', '', all)
            all = re.sub(r'\[\[Image:.*?\]\]', '', all)
            all = re.sub(r'Image:.*?\|', '', all)
            all = re.sub(r'\[\[.*?\|*([^\|]*?)\]\]', r'\1', all)
            all = re.sub(r'\&lt;.*?&gt;', '', all)
        except:
            # Something went wrong, try again. (This is bad coding practice.)
            print 'oops. there was a failure parsing %s. retrying...' \
                % articletitle
            failed = True
            continue

    return(all, articletitle)

class WikiThread(threading.Thread):
    articles = list()
    articlenames = list()
    lock = threading.Lock()

    def run(self):
        (article, articlename) = get_random_wikipedia_article()
        WikiThread.lock.acquire()
        WikiThread.articles.append(article)
        WikiThread.articlenames.append(articlename)
        WikiThread.lock.release()

def get_random_wikipedia_articles(n):
    """
    Downloads n articles in parallel from Wikipedia and returns lists
    of their names and contents. Much faster than calling
    get_random_wikipedia_article() serially.
    """
    maxthreads = 8
    WikiThread.articles = list()
    WikiThread.articlenames = list()
    wtlist = list()
    for i in range(0, n, maxthreads):
        print 'downloaded %d/%d articles...' % (i, n)
        for j in range(i, min(i+maxthreads, n)):
            wtlist.append(WikiThread())
            wtlist[len(wtlist)-1].start()
        for j in range(i, min(i+maxthreads, n)):
            wtlist[j].join()
    return (WikiThread.articles, WikiThread.articlenames)

if __name__ == '__main__':
    t0 = time.time()

    (articles, articlenames) = get_random_wikipedia_articles(1)
    for i in range(0, len(articles)):
        print articlenames[i]

    t1 = time.time()
    print 'took %f' % (t1 - t0)