Added class simplifiing ledbar output

* also added rainbow.py, which uses this class to create rainbow effect

host_python/ledbar.py

@@ -0,0 +1,50 @@
+#!/usr/bin/python
+# vim:et:sw=4:ts=4:sts=4
+
+import sys
+import time
+
+class Ledbar:
+
+    def __init__(self, boxes=10, secs_per_frame=0.025):
+        self.boxes = boxes
+        self.secs_per_frame = secs_per_frame
+        self.last_update = time.time()
+        self.pixels = []
+        for i in xrange(boxes):
+            self.pixels.append([0, 0, 0])
+
+    def set_pixel(self, pixel, red, green, blue):
+        self.set_red(pixel, red)
+        self.set_green(pixel, green)
+        self.set_blue(pixel, blue)
+
+    def set_red(self, pixel, red):
+        if red < 0.0 or red > 1.0: raise ValueError('red has to be between 0.0 and 1.0')
+        self.pixels[pixel][0] = int(red*255.99)
+
+    def set_green(self, pixel, green):
+        if green < 0.0 or green > 1.0: raise ValueError('green has to be between 0.0 and 1.0')
+        self.pixels[pixel][1] = int(green*255.99)
+
+    def set_blue(self, pixel, blue):
+        if blue < 0.0 or blue > 1.0: raise ValueError('blue has to be between 0.0 and 1.0')
+        self.pixels[pixel][2] = int(blue*255.99)
+
+    def echo(self, s, no_newline=False):
+        sys.stderr.write(str(s) + ('' if no_newline else '\n'))
+
+    def update(self):
+        now = time.time()
+        delta = now - self.last_update
+        if delta < self.secs_per_frame:
+            time.sleep(self.secs_per_frame - delta)
+        try:
+            for p in self.pixels:
+                for c in p:
+                    sys.stdout.write(chr(c))
+            sys.stdout.flush()
+        except IOError:
+            return False
+        self.last_update += self.secs_per_frame
+        return True