Search code examples
python-attrs

Approximately compare decimal attributes of a class defined with `attrs`

I have a Thing class with an float x attribute. And I want to approximately compare two instances of Thing with a relelative tolerance of 1e-5.

import attr

@attr.s
class Thing(object):
    x: float = attr.ib()


>>> assert Thing(3.141592) == Thing(3.1415926535)  # I want this to be true with a relelative tolerance of 1e-5
False

Do I need to override the __eq__ method or is there a clean way of telling attr to use math.isclose() or a custom comparison function?

Solution

  • Yes, setting eq=True and implementing your own __eq__/__ne__ is your way to go. In this case your need is so specific that I wouldn't even know how to abstract it away without making it confusing.