Hello, I'm trying to play a little bit with Twisted to discover how it works and I thought it was a nice exercise with the following case.
I have a list of IP addresses that I want to get the reverse DNS value. I'm using the answer provided by JP at http://twistedmatrix.com/pipermail/twisted-python/2004-September/008715.html to perform the lookup and it's all good. I'm putting all the results of client.lookupPointer() into a DeferredList to display the result in order when everything is donew, which is also working fine. The code looks like this so far: def resolve(ip): ptr = '.'.join(ip.split('.')[::-1]) + '.in-addr.arpa' return client.lookupPointer(ptr) def display_results(result): for (succeeded, value) in result: if not succeeded: print "unknown" else: (ans, auth, add) = value name = ans[0].payload.name print name d = DeferredList([resolve(ip) for ip in IPS], consumeErrors=True).addCallback(display_results) Now, I would like to have access both to the result of the lookup but also the original IP address, so that I can print, especially, the addresses which failed to be resolved. At first, I added a callback to lookupPointer() like this: client.lookupPointer(ptr).addCallback(lambda r: (ip, r)) and it does the job: in display_results(), I now have the IP address and the result of the lookup. However, I'm stuck how to do this for the failures: I tried to add an errback the same way as I added the callback to lookupPointer(), but then, it seems that DeferredList() sees the result of the errback() as a ssuccess, so `succeeded` is True and I hav to ressort to a isinstance() call to compare to see if my item is a Failure exception or not, like this: def display_results(result): for (succeeded, value) in result: ip, answer = result if isinstance(answer, twisted.python.failure.Failure): succeeded = False ... My question is: is there a simpler way to pass values along the callbacks? Side question: why the reactor is not stopped in the final example below? Thanks! Jonathan ps: my final try looks like this: from twisted.internet import reactor from twisted.internet.defer import DeferredList from twisted.names import client import twisted.python.failure IPS = open('ips.txt').read().split()[0:10] def display_results(result): for (succeeded, value) in result: ip, answer = value if isinstance(answer, twisted.python.failure.Failure): succeeded = False if not succeeded: name = "(unknown)" else: (ans, auth, add) = answer name = str(ans[0].payload.name) print "%16s: %s" % (ip, name) def resolve(ip): ptr = '.'.join(ip.split('.')[::-1]) + '.in-addr.arpa' return client.lookupPointer(ptr).\ addCallback(lambda x: (ip, x)).\ addErrback(lambda x: (ip, x)) l = [resolve(ip) for ip in IPS] d = DeferredList( l, consumeErrors=True).\ addCallback(display_results).\ addCallback(lambda x: reactor.stop) reactor.run() _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
