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from vpython import *
# John Coady

scene.title = "Mouse Drag"
scene.caption = """Click and drag mouse in 3D window to insert small sphere."""

scene.range = 3

b = box(pos=vector(0,0,0), color=color.green)

drag = False
s = None

def grab(evt):
    global s, drag
    scene.title = 'Drag the sphere'
    if evt.which == 1:
        drag = True
        loc = evt.pos
        s = sphere(pos=loc, radius=0.1, color=color.red)

def move(evt):
    if drag:
        s.pos = evt.pos

def drop(evt):
    global drag
    scene.title = 'Mouse Drag'
    s.color = color.cyan
    drag = False

scene.bind('mousedown',grab)
scene.bind('mousemove',move)
scene.bind('mouseup',drop)


    

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