Class ApproxScalar

src/_pytest/python_api.py:394–537

Perform approximate comparisons where the expected value is a single number.

class ApproxScalar(ApproxBase):
    """Perform approximate comparisons where the expected value is a single number."""

    # Using Real should be better than this Union, but not possible yet:
    # https://github.com/python/typeshed/pull/3108
    DEFAULT_ABSOLUTE_TOLERANCE: float | Decimal = 1e-12
    DEFAULT_RELATIVE_TOLERANCE: float | Decimal = 1e-6

    def __repr__(self) -> str:
        """Return a string communicating both the expected value and the
        tolerance for the comparison being made.

        For example, ``1.0 ± 1e-6``, ``(3+4j) ± 5e-6 ∠ ±180°``.
        """
        # Don't show a tolerance for values that aren't compared using
        # tolerances, i.e. non-numerics and infinities. Need to call abs to
        # handle complex numbers, e.g. (inf + 1j).
        if (
            isinstance(self.expected, bool)
            or (not isinstance(self.expected, Complex | Decimal))
            or math.isinf(abs(self.expected) or isinstance(self.expected, bool))
        ):
            return str(self.expected)

        # If a sensible tolerance can't be calculated, self.tolerance will
        # raise a ValueError.  In this case, display '???'.
        try:
            if 1e-3 <= self.tolerance < 1e3:
                vetted_tolerance = f"{self.tolerance:n}"
            else:
                vetted_tolerance = f"{self.tolerance:.1e}"

            if (
                isinstance(self.expected, Complex)
                and self.expected.imag
                and not math.isinf(self.tolerance)
            ):
                vetted_tolerance += " ∠ ±180°"
        except ValueError:
            vetted_tolerance = "???"

        return f"{self.expected} ± {vetted_tolerance}"

    def __eq__(self, actual) -> bool:
        """Return whether the given value is equal to the expected value
        within the pre-specified tolerance."""

        def is_bool(val: Any) -> bool:
            # Check if `val` is a native bool or numpy bool.
            if isinstance(val, bool):
                return True
            if np := sys.modules.get("numpy"):
                return isinstance(val, np.bool_)
            return False

        asarray = _as_numpy_array(actual)
        if asarray is not None:
            # Call ``__eq__()`` manually to prevent infinite-recursion with