Confusion over disallowed comparisons in pytest.approx docs

[HalfWhitt]

In the docs for pytest.approx, a note at the bottom says this:

In order to avoid inconsistent behavior, TypeError is raised for >, >=, < and <= comparisons. The example below illustrates the problem:

assert approx(0.1) > 0.1 + 1e-10  # calls approx(0.1).__gt__(0.1 + 1e-10)
assert 0.1 + 1e-10 > approx(0.1)  # calls approx(0.1).__lt__(0.1 + 1e-10)

In the second example one expects approx(0.1).__le__(0.1 + 1e-10) to be called. But instead, approx(0.1).__lt__(0.1 + 1e-10) is used to comparison. This is because the call hierarchy of rich comparisons follows a fixed behavior. More information: object.__ge__()

Either there's a typo here, or I'm misunderstanding something. I don't see how one would expect the second line to call __le__ instead of __lt__. Is the comparison shown supposed to be >=? Am I overlooking something?

[RonnyPfannschmidt]

The cpython documentation is clear in the call order and equivalents we just repeat it

[HalfWhitt]

Thank you for your quick reply. I'm not sure what you mean by "order". If you're referring to this paragraph:

There are no swapped-argument versions of these methods (to be used when the left argument does not support the operation but the right argument does); rather, __lt__() and __gt__() are each other’s reflection, __le__() and __ge__() are each other’s reflection, and __eq__() and __ne__() are their own reflection. If the operands are of different types, and the right operand’s type is a direct or indirect subclass of the left operand’s type, the reflected method of the right operand has priority, otherwise the left operand’s method has priority. Virtual subclassing is not considered.

Then yes, I understand that in this line...

assert 0.1 + 1e-10 > approx(0.1)  # calls approx(0.1).__lt__(0.1 + 1e-10)

...the reflected method of the righthand operand is being called. However, > corresponds to __gt__, whose reflection is __lt__. And that is, apparently, what's called. So why would I expect it to call __le__, as the passage in pytest's docs says I would?

[HalfWhitt]

Having found #2003, I now see how the reasoning is to avoid inequalities because of potentially differing expectations of how exactly they'd be implemented. But I still don't see how anyone would ever expect > to call __le__ (or, when not reflected, __ge__). That's just not how the operator is defined.

Would you be averse to a PR altering this section to explain the potential ambiguities differently?