crawl.py

"""Compare the speed of downloading URLs sequentially vs. using futures."""

import functools
import time
import timeit
import sys

try:
    from urllib2 import urlopen
except ImportError:
    from urllib.request import urlopen

from concurrent.futures import (as_completed, ThreadPoolExecutor,
                                ProcessPoolExecutor)

URLS = ['http://www.google.com/',
        'http://www.apple.com/',
        'http://www.ibm.com',
        'http://www.thisurlprobablydoesnotexist.com',
        'http://www.slashdot.org/',
        'http://www.python.org/',
        'http://www.bing.com/',
        'http://www.facebook.com/',
        'http://www.yahoo.com/',
        'http://www.youtube.com/',
        'http://www.blogger.com/']

def load_url(url, timeout):
    kwargs = {'timeout': timeout} if sys.version_info >= (2, 6) else {}
    return urlopen(url, **kwargs).read()

def download_urls_sequential(urls, timeout=60):
    url_to_content = {}
    for url in urls:
        try:
            url_to_content[url] = load_url(url, timeout=timeout)
        except:
            pass
    return url_to_content

def download_urls_with_executor(urls, executor, timeout=60):
    try:
        url_to_content = {}
        future_to_url = dict((executor.submit(load_url, url, timeout), url)
                             for url in urls)

        for future in as_completed(future_to_url):
            try:
                url_to_content[future_to_url[future]] = future.result()
            except:
                pass
        return url_to_content
    finally:
        executor.shutdown()

def main():
    for name, fn in [('sequential',
                      functools.partial(download_urls_sequential, URLS)),
                     ('processes',
                      functools.partial(download_urls_with_executor,
                                        URLS,
                                        ProcessPoolExecutor(10))),
                     ('threads',
                      functools.partial(download_urls_with_executor,
                                        URLS,
                                        ThreadPoolExecutor(10)))]:
        sys.stdout.write('%s: ' % name.ljust(12))
        start = time.time()
        url_map = fn()
        sys.stdout.write('%.2f seconds (%d of %d downloaded)\n' %
                         (time.time() - start, len(url_map), len(URLS)))

if __name__ == '__main__':
    main()