Spontaneous scene error

[hmathers]

The equivalent of the following code did not initially produce an error, but the next day it did:

from vpython import canvas,box
scene = None
def reset(scene=scene):
    if scene: scene.delete()
    scene = canvas()
reset(scene)
scene.camera.follow(box())

AttributeError: 'NoneType' object has no attribute 'camera'

I fixed it with:

from vpython import canvas,box
scene = None
def reset():
    global scene
    if scene: scene.delete()
    scene = canvas()
reset()
scene.camera.follow(box())

[BruceSherwood]

This isn't a VPython issue but a Python issue. There really is no way that the first version could have worked, since inside the reset function "scene" is a local variable and "scene = canvas()" has no effect on the global variable "scene", which still has the value None when scene.camera is referenced.