is numpy isclose function returning bad answer? Using numpy isclose in the following example:

import numpy as np
np.isclose(1533761040,1533748023.0, atol=1)


Returns True, which is False.
No, it uses both an absolute and relative tolerance, and the default of rtol is nonzero, adding some more tolerance. See https://docs.scipy.org/doc/numpy-1.14.0/reference/generated/numpy.isclose.html