Removed redundant switch impl in pyevent hub. Added more exc_clears where needed. Slightly optimized switch a bit.

eventlet/hubs/hub.py

@@ -106,9 +106,8 @@ class BaseHub(object):
         if self.greenlet.dead:
             self.greenlet = greenlet.greenlet(self.run)
         try:
-            current = greenlet.getcurrent()
+            if self.greenlet.parent is not cur: 
-            if self.greenlet.parent is not current: 
+                cur.parent = self.greenlet
-                current.parent = self.greenlet
         except ValueError:
             pass  # gets raised if there is a greenlet parent cycle
         sys.exc_clear()

eventlet/hubs/poll.py

@@ -108,3 +108,4 @@ class Hub(BaseHub):
                 raise
             except:
                 self.squelch_exception(fileno, sys.exc_info())
+                sys.exc_clear()

eventlet/hubs/pyevent.py

@@ -46,23 +46,6 @@ class Hub(BaseHub):
         self.signal(2, lambda signalnum, frame: self.greenlet.parent.throw(KeyboardInterrupt))
         self.events_to_add = []
 
-    def switch(self):
-        cur = greenlet.getcurrent()
-        assert cur is not self.greenlet, 'Cannot switch to MAINLOOP from MAINLOOP'
-        switch_out = getattr(cur, 'switch_out', None)
-        if switch_out is not None:
-            try:
-                switch_out()
-            except:
-                traceback.print_exception(*sys.exc_info())
-        if self.greenlet.dead:
-            self.greenlet = greenlet.greenlet(self.run)
-        try:
-            greenlet.getcurrent().parent = self.greenlet
-        except ValueError:
-            pass
-        return self.greenlet.switch()
-
     def dispatch(self):
         loop = event.loop
         while True:

eventlet/hubs/selects.py

@@ -57,3 +57,4 @@ class Hub(BaseHub):
                     raise
                 except:
                     self.squelch_exception(fileno, sys.exc_info())
+                    sys.exc_clear()