Global variable assignment issue
def nodegen(slabel, dlabel, sx, xy, dx, dy, num):
   for i in range(1, num + 1):
      label = slabel + (i - 1)*dlabel
      global vars()["n" + str(label)]
      vars()["n" + str(label)] = Node(label, (sx + i*dx, sy + i*dy))
      vars()["n" + str(label)].info()

def fun(name, value):
    globals()[name] = value

def nodegen(nodes, slabel, dlabel, sx, xy, dx, dy, num):
    label = slabel + (i - 1) * dlabel
    key   = 'n{0}'.format(label)

    nodes[key] = [
        Node(label, (sx + i * dx, sy + i * dy))
        for i in range(1, num + 1) # use xrange in Python 2
    ]

some_nodes = {}
nodegen(some_nodes, ...)
nodegen(some_nodes, ...)