A very simple multithreading parallel URL fetching (without queue)

callback, multithreading, python, python-multithreading, urlfetch

Solution

Simplifying your original version as far as possible:

import threading
import urllib2
import time

start = time.time()
urls = ["http://www.google.com", "http://www.apple.com", "http://www.microsoft.com", "http://www.amazon.com", "http://www.facebook.com"]

def fetch_url(url):
    urlHandler = urllib2.urlopen(url)
    html = urlHandler.read()
    print "'%s\' fetched in %ss" % (url, (time.time() - start))

threads = [threading.Thread(target=fetch_url, args=(url,)) for url in urls]
for thread in threads:
    thread.start()
for thread in threads:
    thread.join()

print "Elapsed Time: %s" % (time.time() - start)

The only new tricks here are:

- Keep track of the threads you create.

- Don't bother with a counter of threads if you just want to know when they're all done; `join` already tells you that.

- If you don't need any state or external API, you don't need a `Thread` subclass, just a `target` function.

Problem

I spent a whole day looking for the simplest possible multithreaded URL fetcher in Python, but most scripts I found are using queues or multiprocessing or complex libraries. Finally I wrote one myself, which I am reporting as an answer. Please feel free to suggest any improvement. I guess other people might have been looking for something similar.

Original source