gistfile1.py

from datetime import datetime
import hashlib
import time
import urllib


def main():
    fn = 'current-%s.jpg' % datetime.now().strftime('%Y%m%d%H%M')
    lasthash = file('LATEST', 'r').read().strip()
    thishash, thisfile = None, None
    while True:
        thisfile = urllib.urlopen('http://www.doncaster.gov.uk/webcam/current.jpg').read()
        thishash = hashlib.md5(thisfile).hexdigest()
        if lasthash != thishash:
            break
        time.sleep(30) # sleep for 30 seconds
    file(fn, 'w').write(thisfile)
    file('LATEST', 'w').write(thishash)

if __name__ == '__main__':
    main()