See Nathanials note -- but I think the key thing is that assertAlmostEqual is NOT really intended for float comparisons -- rather, it's intended for decimal numbers that happen to be stored in floats (does it pre-date the Decimal object?)

In practical use, most of us are used to thinking in terms of decimal numbers, it's what we all learn in grade school. An in practice, Python, and every other language I've seen, takes decimal literals for floats, and displays floats as decimals. Also in practical use, using floats for decimal numbers works just fine, particularly if you round on output.

So I that's the use-case for assertAlmostEqual -- it provides an easy way to check if numbers are almost equal to N decimal places. I guess that's a pretty common use case. So maybe folks would want to keep it around.

(by the way -- does it work for Decimal objects -- it really should, it's more appropriate for them anyway!)

On the other hand, those of us trained in science and engineering are used to working with scientific or engineering notation -- i.e. x.xxxEn (some number times ten raised to a power)-- a mantissa and an exponent. While we still decimal, it's a better match for floating point numbers.

We are also trained to consider "significant figures" -- or the number of digits of accuracy of a value -- measured or computed.

123,000,000

has the same number of significant figures as
0.000123

But they are not of the same value at all.

Anyway, a relative comparison provides something akin to a comparison to a certain number of significant figures -- really common and useful, and familiar to at least those trained in most disciplines of science or engineering.

Key here is that I'm not suggesting a better or more correct assertAlmostEqual. I'm suggesting something different (arguably more useful).

I'm honestly not sure how useful assertAlmostEqual is -- but apparently is was useful enough to put in the first place ,and to get used since then.

 

even if it isn't a replacemen --  that sequence behavior is nice -- and Steven has already written it as well.