Using wget via Python

Question

How would I download files (video) with Python using wget and save them locally? There will be a bunch of files, so how do I know that one file is downloaded so as to automatically start downloding another one?

Thanks.

Answer 1

Don't do this. Use either urllib2 or urlgrabber instead.

Answer 2

If you use os.system() to spawn a process for the wget, it will block until wget finishes the download (or quits with an error). So, just call os.system('wget blah') in a loop until you've downloaded all of your files.

Alternatively, you can use urllib2 or httplib. You'll have to write a non-trivial amount code, but you'll get better performance, since you can reuse a single HTTP connection to download many files, as opposed to opening a new connection for each file.

Answer 3

No reason to use os.system. Avoid writing a shell script in Python and go with something like urllib.urlretrieve or an equivalent.

Edit... to answer the second part of your question, you can set up a thread pool using the standard library Queue class. Since you're doing a lot of downloading, the GIL shouldn't be a problem. Generate a list of the URLs you wish to download and feed them to your work queue. It will handle pushing requests to worker threads.

I'm waiting for a database update to complete, so I put this together real quick.

#!/usr/bin/python

import sys
import threading
import urllib
from Queue import Queue
import logging

class Downloader(threading.Thread):
    def __init__(self, queue):
        super(Downloader, self).__init__()
        self.queue = queue

    def run(self):
        while True:
            download_url, save_as = queue.get()
            # sentinal
            if not download_url:
                return
            try:
                urllib.urlretrieve(download_url, filename=save_as)
            except Exception, e:
                logging.warn("error downloading %s: %s" % (download_url, e))

if __name__ == '__main__':
    queue = Queue()
    threads = []
    for i in xrange(5):
        threads.append(Downloader(queue))
        threads[-1].start()

    for line in sys.stdin:
        url = line.strip()
        filename = url.split('/')[-1]
        print "Download %s as %s" % (url, filename)
        queue.put((url, filename))

    # if we get here, stdin has gotten the ^D
    print "Finishing current downloads"
    for i in xrange(5):
        queue.put((None, None))

Answer 4

No reason to use python. Avoid writing a shell script in Python and go with something like bash or an equivalent.