Method test_relative_symmetry

Lib/test/test_statistics.py:316–330

(self)

    # Test symmetry of approx_equal.

    def test_relative_symmetry(self):
        # Check that approx_equal treats relative error symmetrically.
        # (a-b)/a is usually not equal to (a-b)/b. Ensure that this
        # doesn't matter.
        #
        #   Note: the reason for this test is that an early version
        #   of approx_equal was not symmetric. A relative error test
        #   would pass, or fail, depending on which value was passed
        #   as the first argument.
        #
        args1 = [2456, 37.8, -12.45, Decimal('2.54'), Fraction(17, 54)]
        args2 = [2459, 37.2, -12.41, Decimal('2.59'), Fraction(15, 54)]
        assert len(args1) == len(args2)
        for a, b in zip(args1, args2):
            self.do_relative_symmetry(a, b)

    def do_relative_symmetry(self, a, b):
        a, b = min(a, b), max(a, b)