This change stops sleekxmpp from spending huge amounts of time unnecessarily computing logging data that may never be used. This is a HUGE performance improvement; in some of my test runs, unnecessary string creation was accounting for > 60% of all CPU time.

Note that using % in a string will _always_ perform the sting substitutions, because the strings are constructed before the function is called. So log.debug('%s' % expensiveoperation()) will take about the same CPU time whether or not the logging level is DEBUG or INFO. if you use , no substitutions are performed unless the string is actually logged

sleekxmpp/xmlstream/handler/waiter.py

@@ -91,7 +91,7 @@ class Waiter(BaseHandler):
             stanza = self._payload.get(True, timeout)
         except queue.Empty:
             stanza = False
-            log.warning("Timed out waiting for %s" % self.name)
+            log.warning("Timed out waiting for %s" , self.name)
         self.stream().remove_handler(self.name)
         return stanza