Re: [Python-ideas] Fwd: PEP 485: A Function for testing approximate equality

On Tue, Jan 27, 2015 at 12:16 AM, Chris Barker wrote:

On Sun, Jan 25, 2015 at 11:07 PM, Paul Moore wrote:

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I'm not sure what you're saying here - by "not setting defaults" do you mean making it mandatory for the user to supply a tolerance, as I suggested above?

I for one, think making it mandatory to set one would be better than just letting the zeros get used.

I've used the numpy version of this a lot for tests, , and my work flow is usually:

write a test with the defaults

if it pases, I'm done.

If it fails, then I look and see if my code is broken, or if I can accept a larger tolerance.

So I'm quite happy to have a default.

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I really think that having three tolerances, once of which is nearly always ignored, is poor API design. The user usually knows when they are comparing against an expected value of zero and can set an absolute error tolerance.

Agreed.

also agreed -- Nathanial -- can you live with this?

I can live with it, but I'd ignore the function and use allclose instead :-). In your workflow above, I'm guessing that with allclose then it's <1% of the time that you have a failure due to too-restrictive default tolerances, where you then have to switch from thinking about your problem to thinking about floating point details. With no absolute tolerance, this rises to ~30% (assuming my super quick and dirty github statistics are typical). That's a lot of workflow disruption. -n -- Nathaniel J. Smith Postdoctoral researcher - Informatics - University of Edinburgh http://vorpus.org