pytest.approx: Please improve repr readability

It seems that pytest.approx repr is optimized for very high or very low tolerances, but is not as easily readable as it could be for values in between.
Some examples:

pytest.approx(42, abs=1) repr is 42 ± 1.0e+00, which could be just 42 ± 1.
pytest.approx(5, rel=0.01) repr is 5 ± 5.0e-02, but could be 5 ± 0.05 or maybe even 5 ± 1%
pytest.approx(24000, abs=500) repr is 24000 ± 5.0e+02 and could be 24000 ± 500
removing accuracy example: pytest.approx(1500, abs=555) repr is 1500 ± 5.6e+02 and could be 1500 ± 555

In these number ranges using the exact number instead of the exponential notation is both more accurate and easier readable for humans. Please adapt pytest.approx to switch it's repr style according to the input value ranges.

Hey, my team and I would like to look over this issue and resolve it if that's okay.

Of course, PRs are always welcome! Hopefully this one won't be too hard, either.

See https://docs.python.org/3/library/string.html#format-specification-mini-language - you probably want to use the n format specifier.

@Zac-HD

@Zac-HD is this issue still open, I would like to work on it

Improve approx repr for better readability (pytest-dev#12665)

I think this change has a regression on line 409. I am catching a FloatOperation exception as this change is comparing a float to a Decimal.

self = <[FloatOperation([<class 'decimal.FloatOperation'>]) raised in repr()] ApproxDecimal object at 0xffffa0403e00>

    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: # <--- This is the exact line causing the FloatOperation
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E           decimal.FloatOperation: [<class 'decimal.FloatOperation'>]

/usr/local/lib/python3.13/site-packages/_pytest/python_api.py:405: FloatOperation

chore(deps): update dependency pytest to v9 (#305)

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pytest.approx: Please improve repr readability #6985

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pytest.approx: Please improve repr readability #6985

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hodevin commented on Mar 30, 2020

kalekundert commented on Mar 30, 2020

Zac-HD commented on Mar 31, 2020

henzef commented on Apr 13, 2022

fazeelghafoor commented on Jul 28, 2024

rishid commented on Jun 17, 2025

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