A good summary on floating point comparison algorithms can be found at http://www.boost.org/doc/libs/1_34_0/libs/test/doc/components/test_tools/floating_point_comparison.html
I, too, redefine almostEquals so that the comparison is more robust +1 On Sun, Mar 28, 2010 at 2:06 AM, Steven D'Aprano <st...@pearwood.info>wrote: > On Sun, 28 Mar 2010 02:54:19 pm Charles McCreary wrote: > > Perhaps not just absolute but relative tolerance, e.g.: > > > > def isclose(x, y, rtol=1.e-5, atol=1.e-8): > > return abs(x-y) <= atol + rtol * abs(y) > > I'm not sure why you add the tolerances like that. Surely a more > appropriate approach is to compare the values against the tolerances > individually, and return True if they meet either condition. > > For what it's worth, here's a recipe I wrote for approximately equal, > following someone's complaint on comp.lang.python that Python has no > approximately-equal operator. > > http://code.activestate.com/recipes/577124-approximately-equal/ > > Comments and criticism welcome. > > I've never found unittest.TestCase.assertAlmostEqual to be useful. I > generally write my own comparison function, then call: > > assert_(compare(x, y)) > > as needed. I'm +0.5 on Michael's suggested change -- it will make > assertAlmostEqual marginally more useful, which is a plus, but I'm not > sure that absolute tolerances are better than relative. But how general > do we want to be? "Almost equal" means something different to everyone. > > > > > On Fri, Mar 26, 2010 at 7:59 PM, Michael Foord > <fuzzy...@voidspace.org.uk>wrote: > > > Hello all, > > > > > > A user has suggested an optional argument to > > > unittest.TestCase.assertAlmostEqual for specifying a maximum > > > difference between the expected and actual values, instead of using > > > rounding. > [snip] > > > > -- > Steven D'Aprano > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/charles.r.mccreary%40gmail.com > -- Charles McCreary P.E. CRM Engineering 903.643.3490 - office 903.224.5701 - mobile/GV
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