Python3 compatibility (#66) (#67)

* Fixes for Python 3 compatibility

* remove unneeded imports

src/led_effect.py

@@ -24,9 +24,11 @@ def __getitem__(self, a):
             return super(colorArray, self).__getitem__(
                             slice(a*3, a*3+3))
         if isinstance(a, slice):
-            return colorArray(
+                start = a.start*3 if a.start != None else None
+                stop = a.stop*3 if a.stop != None else None
+                return colorArray(
                         super(colorArray, self).__getitem__(
-                            slice(a.start*3, a.stop*3, a.step)))
+                            slice(start, stop, a.step)))
     def __getslice__(self, a, b):
         return self.__getitem__(slice(a,b))
     def __setitem__(self, a, v):
@@ -37,19 +39,19 @@ def __setitem__(self, a, v):
     def __len__(self):
         return super(colorArray, self).__len__() // 3
     def reverse(self):
-        self[:] = [c for cl in range(len(self)-1,-1, -1)
-                        for c in self[cl]]
+        self.__init__([c for cl in range(len(self)-1,-1, -1)
+                        for c in self[cl]])
     def shift(self, shift=1, direction=True):
         if direction:
             #shift array to the right
-            self[:] = self[-shift:] + self[:-shift]
+            self.__init__(self[-shift:] + self[:-shift])
         else:
             #shift array to the left
-            self[:] = self[shift:] + self[:shift]
+            self.__init__(self[shift:] + self[:shift])
     def padLeft(self, v, a):
-        self[:] = v * a + self[:]
+        self.__init__(v * a + self)
     def padRight(self, v, a):
-        self[:] = self[:] + v * a
+        self += v * a
 
 ######################################################################
 # LED Effect handler
@@ -222,9 +224,11 @@ def _getFrames(self, eventtime):
                 chain.prev_data = None # workaround to force update of dotstars
             if not self.shutdown: 
                 chain.led_helper.update_func(chain.led_helper.led_state, None)
-
-        next_eventtime=min(self.effects, key=lambda x: x.nextEventTime)\
-                        .nextEventTime
+        if self.effects:
+            next_eventtime=min(self.effects, key=lambda x: x.nextEventTime)\
+                            .nextEventTime
+        else:
+            next_eventtime = eventtime
         # run at least with 10Hz
         next_eventtime=min(next_eventtime, eventtime + 0.1) 
         return next_eventtime
@@ -687,7 +691,7 @@ def __init__(self,  **kwargs):
 
             comet = colorArray([a * b for a, b in zip(gradient,decayTable)])
 
-            comet.padRight([0.0,0.0,0.0], self.ledCount)
+            comet.padRight([0.0,0.0,0.0], self.ledCount - len(comet))
 
             if self.direction: comet.reverse()