On Dec 30, 12:31 pm, Philip Semanchuk <phi...@semanchuk.com> wrote: > On Dec 30, 2009, at 11:00 AM, Brian D wrote: > > > > > I'm actually using mechanize, but that's too complicated for testing > > purposes. Instead, I've simulated in a urllib2 sample below an attempt > > to test for a valid URL request. > > > I'm attempting to craft a loop that will trap failed attempts to > > request a URL (in cases where the connection intermittently fails), > > and repeat the URL request a few times, stopping after the Nth attempt > > is tried. > > > Specifically, in the example below, a bad URL is requested for the > > first and second iterations. On the third iteration, a valid URL will > > be requested. The valid URL will be requested until the 5th iteration, > > when a break statement is reached to stop the loop. The 5th iteration > > also restores the values to their original state for ease of repeat > > execution. > > > What I don't understand is how to test for a valid URL request, and > > then jump out of the "while True" loop to proceed to another line of > > code below the loop. There's probably faulty logic in this approach. I > > imagine I should wrap the URL request in a function, and perhaps store > > the response as a global variable. > > > This is really more of a basic Python logic question than it is a > > urllib2 question. > > Hi Brian, > While I don't fully understand what you're trying to accomplish by > changing the URL to google.com after 3 iterations, I suspect that some > of your trouble comes from using "while True". Your code would be > clearer if the while clause actually stated the exit condition. Here's > a suggestion (untested): > > MAX_ATTEMPTS = 5 > > count = 0 > while count <= MAX_ATTEMPTS: > count += 1 > try: > print 'attempt ' + str(count) > request = urllib2.Request(url, None, headers) > response = urllib2.urlopen(request) > if response: > print 'True response.' > except URLError: > print 'fail ' + str(count) > > You could also save the results (untested): > > MAX_ATTEMPTS = 5 > > count = 0 > results = [ ] > while count <= MAX_ATTEMPTS: > count += 1 > try: > print 'attempt ' + str(count) > request = urllib2.Request(url, None, headers) > f = urllib2.urlopen(request) > # Note that here I ignore the doc that says "None may be > # returned if no handler handles the request". Caveat emptor. > results.append(f.info()) > f.close() > except URLError: > # Even better, append actual reasons for the failure. > results.append(False) > > for result in results: > print result > > I guess if you're going to do the same number of attempts each time, a > for loop would be more expressive, but you probably get the idea. > > Hope this helps > Philip
Nice to have options, Philip. Thanks! I'll give your solution a try in mechanize as well. I really can't thank you enough for contributing to helping me solve this issue. I love Python. -- http://mail.python.org/mailman/listinfo/python-list
