Consider the following simple class that provides a "__complex__" method.

class C(object):
  def __init__(self, x):
     self.x = x
  def __complex__(self):
    return self.x

x=C(-0j)

PYTHON 2.7.13
>>> x.x
-0j
>>> complex(x)
0j

PYTHON 3.6
>>> x.x
(-0-0j)
>>> complex(x)
(-0+0j)