def test_zero_is_multiplicative_nil(self):
o = FermionOperator.zero()
u = FermionOperator.identity()
f = FermionOperator(((0, 1), (5, 0), (6, 1)), 0.6j)
g = FermionOperator(((0, 0), (5, 0), (6, 1)), 0.3j)
self.assertTrue(o.isclose(o * u))
self.assertTrue(o.isclose(o * f))
self.assertTrue(o.isclose(o * g))
self.assertTrue(o.isclose(o * (f + g)))
def test_zero_is_additive_identity(self):
o = FermionOperator.zero()
f = FermionOperator(((0, 1), (5, 0), (6, 1)), 0.6j)
g = FermionOperator(((0, 0), (5, 0), (6, 1)), 0.3j)
h = f + g
self.assertTrue(f.isclose(o + f))
self.assertTrue(f.isclose(f + o))
self.assertTrue(g.isclose(o + g))
self.assertTrue(g.isclose(g + o))
self.assertTrue(h.isclose(o + h))
self.assertTrue(h.isclose(h + o))
o += h
self.assertTrue(h.isclose(o))
self.assertFalse(f.isclose(o))
# Method always returns new instances.
self.assertFalse(FermionOperator.zero().isclose(o))