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

[Nikolaus Rath]

Nathaniel Smith <njs-e+AXbWqSrlAAvxtiuMwx3w at public.gmane.org> writes:
> It's an observable fact, though, that people generally do take care to
> ensure that their numbers are within a few orders of magnitude of 1,
> e.g. by choosing appropriate units, log-transforming, etc.

Do you have a credible source for that, or are you just speculating? At
least in my field I'm regularly working with e.g. particle densities in
the order of 10^19, and I've never seen anyone log-transforming these
numbers (let alone inventing new units for them).

> You could just as reasonably ask why in the world SI prefixes exist
> when we have access to scientific notation. And I wouldn't know the
> answer :-). But they do!

Because they are shorter to write, and easier to parse. Compare

 3.12 x 10^-6 s

(13 characters, not counting ^) with

 3.12 µs

(7 characters).

HTH,
-Nikolaus
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