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POFatal Errors and Deferreds in Twisted, stop a deferred
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copied!<p>I have a problem, with normal try except blocks in python you can just return if there is a fatal error, ex...</p> <pre><code>try: logon() except 404_Error: retry_logon(try = 2) except AuthenticationProblem: error_label.SetText( "You password or username was wrong. Make sure that CAPS LOCK key is not on." ) return#nothing more we can do here else: #display user information or whatever </code></pre> <p>So how do this with deferreds, if I just return it goes onto execute the callbacks thinking the error is handled but how do I inform the user something went wrong and destroy the down river chain.</p> <p>==== Update ===</p> <p>mg thanks for the help but it didn't work, even with a fatal error the defer still returns to the callbacks afterwords</p> <pre><code>from twisted.internet import reactor from twisted.internet.defer import Deferred as D class NonFatalError(Exception): 'non fatal error' class FatalError(Exception): 'fatal error' def c(s): print "Callback called" print "Data Received: %s" % s def e(f): print "Errorback Called" print "Error Type: %s" % type(f) print "Traceback" f.printTraceback() print "=======================================" f.trap(NonFatalError) return "Error Handled" def e_fatal(f, d): print "Errorback Called" print "Error Type: %s" % type(f) print "Traceback" f.printTraceback() print "=======================================" print "Fatal Error" f.trap(FatalError) return "Fatal Error... Crash and die. No more callbacks should be called." def trigger(): d.errback(FatalError("This error is fatal to the defer")) if __name__ == "__main__": d = D() d.addErrback(e) d.addErrback(e_fatal, d) d.addCallback(c) d.addCallback(c) d.addCallback(c) d.addCallback(c) reactor.callLater(3, trigger) reactor.callLater(10, reactor.stop) reactor.run() raw_input("Done.") </code></pre>

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