def _unsigned_zero(dtype):
    """
    Given a numpy dtype, finds its "zero" point, which is exactly in the
    middle of its range.
    """

    assert dtype.kind == 'u'
    return 1 << (1 - dtype.itemsize * 8)
dataset/ETHPy150Open spacetelescope/PyFITS/pyfits/util.py/_unsigned_zero/swapped operands of `-`