如何使用 pytest 对小数位数进行近似计算？

Question

Looking through the documentation it says that by default the approx method evaluate until 3 decimal places on a number, but when i compare this value it returns False

pytest.approx(6.495) == 6.49  # False

How can i check if a number is approx. to another within decimal places?

Answer 1

It doesn't say that the default is within three decimal places, it says it's within 1e-6 - or 0.000001 .

By default, approx considers numbers within a relative tolerance of 1e-6 (ie one part in a million) of its expected value to be equal. This treatment would lead to surprising results if the expected value was 0.0, because nothing but 0.0 itself is relatively close to 0.0. To handle this case less surprisingly, approx also considers numbers within an absolute tolerance of 1e-12 of its expected value to be equal.

The rel argument can be used to change what's consider approximately the same value:

>>> pytest.approx(6.495, rel=1e-3) == 6.49
True