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[Python-ideas] Hexadecimal floating literals

Tim Peters tim.peters at gmail.com
Fri Sep 22 13:15:51 EDT 2017 
[Antoine Pitrou <solipsis at pitrou.net>]
> ...
> The main difference is familiarity.  "scientific" notation should be
> well-known and understood even by high school kids.  Who knows about
> hexadecimal notation for floats, apart from floating-point experts?

Here's an example:  you <0x0.2p0 wink>.  For people who understand
both hex and (decimal) scientific notation, learning what hex float
notation means is easy.


> So for someone reading code, the scientific notation poses no problem
> as they understand it intuitively (even if they may not grasp the
> difficulties of the underlying conversion to binary FP), while for
> hexadecimal float notation need they have to go out of their way to
> learn about it, parse the number slowly and try to make out what its
> value is.

I've seen plenty of people on StackOverflow who (a) don't understand
hex notation for integers; and/or (b) don't understand scientific
notation for floats.  Nothing is self-evident about either; they both
have to be learned at first.  Same for hex float notation.  Of course
it's true that many (not all) people do know about hex integers and/or
decimal scientific notation from prior (to Python) experience.

My objection is that we already have a way to use hex float notation,
and the _need_ for it is rare. If someone uninitiated sees a rare:

    x = 0x1.aaap-4

they're going to ask on StackOverflow what the heck it's supposed to
mean.  But if they see a rare:

    x = float.fromhex("0x1.aaap-4")

they can Google for "python fromhex" and find the docs themselves at
once.  The odd method name makes it highly "discoverable", and I think
that's a feature for rare gimmicks with a small, specialized audience.
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