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

[Chris Barker]

On Tue, Jan 27, 2015 at 10:05 AM, Nathaniel Smith <njs at pobox.com> wrote:

> On Tue, Jan 27, 2015 at 4:20 PM, Guido van Rossum <guido at python.org>
> wrote:
> > When does a program need *both* absolute and relative tolerance in a
> single
> > test?
>
> It's reasonably common in numpy, where the equivalent function is
> vectorized to do multiple checks at once,


exactly -- as do a buch of the the unittest assertXXXX methods

or if folks write their own equivalent in a comprehension.



> if 'math' doesn't provide this then many people will use libraries
> that will or else write their own.


sure -- that's what been done for ages... you could say that about anything
new being proposed for the stdlib.



> I guess I don't have a good sense
> of what the audience for 'math' is these days -- I'm sure it has one,
> but aside from tiny one-off usages I'm not sure what it is. None of
> the production numerical code I see even bothers importing it.


Well, I'm a heavy numpy user as well, but I still use the math module when
I have something simple to calculate (actually, not so much simple as small
-- if I'm not working with a lot of numbers) or if I don't want the numpy
dependency.

A lot of people do at least some math with python -- I have no idea how
many. And the statistics package was recently added -- I would have thought
that would be next to useless without numpy, but shows you what I know.


> It's
> possible that it largely serves a kind of pedagogical role? high
> schoolers learning to program etc.?


anyone learning python may need a bit of math -- there's some pretty basic
stuff in there.

The most compelling argument I see is that if we care about unittest,
> then it would be good to have a better alternative to
> assertAlmostEqual. (...I don't know anyone who uses the unittest API
> directly these days, though!)
>

I agree -- adding it to unitest would be a very good idea.

-Chris


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Christopher Barker, Ph.D.
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