Fallback to simpler algorithm for chaining using itertools

Ignores the case when self._points is a mix of list/tuple/float
Only works in cases where self._points is a list of iterables

examples/canvas/lines.py

@@ -140,7 +140,7 @@ class LinePlayground(FloatLayout):
     alpha = NumericProperty(0.5)
     close = BooleanProperty(False)
     points = ListProperty([(500, 500),
-                          300, 300, 500, 300,
+                          [300, 300, 500, 300],
                           [500, 400, 600, 400]])
     points2 = ListProperty([])
     joint = OptionProperty('none', options=('round', 'miter', 'bevel', 'none'))
@@ -152,12 +152,12 @@ def on_touch_down(self, touch):
         if super(LinePlayground, self).on_touch_down(touch):
             return True
         touch.grab(self)
-        self.points = self.points + list(touch.pos)
+        self.points.append(touch.pos)
         return True
 
     def on_touch_move(self, touch):
         if touch.grab_current is self:
-            self.points[-2:] = list(touch.pos)
+            self.points[-1] = touch.pos
             return True
         return super(LinePlayground, self).on_touch_move(touch)
 

kivy/graphics/vertex_instructions_line.pxi

@@ -672,13 +672,10 @@ cdef class Line(VertexInstruction):
             return self._points
 
         def __set__(self, points):
-            tmp = []
-            for p in points:
-                if isinstance(p, (list, tuple)):
-                    tmp = tmp + list(p)
-                else:
-                    tmp.append(p)
-            self._points = tmp
+            import itertools
+            if points and isinstance(points[0], (list, tuple)):
+                self._points = list(itertools.chain(*points))
+
             self.flag_update()
 
     property dash_length: