This is not easy to avoid, I'm afraid, and it's a consequence of Python's usual rules for mixed-type arithmetic:  (-0-0j) is interpreted as 0 - (0.0 + 0.0j) --- that is, the 0j is promoted to a complex instance (by giving it zero real part) before the subtraction is performed.  Then the real part of the result is computed as 0.0 - 0.0, which is 0.0.  Note that the first 0.0 comes from converting the *integer* 0 to a complex number.  If you do -0.0-0.0j you'll see a different result:

>>> -0.0-0.0j
(-0+0j)