[docs] [issue16239] PEP8 arithmetic operator examples

Ezio Melotti report at bugs.python.org
Thu Oct 25 19:50:21 CEST 2012


Ezio Melotti added the comment:

> >-      x = x * 2 - 1
> >-      hypot2 = x * x + y * y
>
> Why you remove this?

As I explained in my previous message, even if valid, these are IMHO less clear than x*2 - 1 and x*x + y*y.

> >-      c = (a+b) * (a-b)
> >+      c = a+b * a-b
>
> This changes the semantic.

It does indeed, but I think it's worth pointing out that misleading spacing should be avoided.  Maybe a different example could be used.

> >but otoh 'x*2 - 1' is a better alternative.
>
> Can you justify this?

x*2 - 1  gives a visual hint of what gets executed first,
x * 2-1  gives a wrong/misleading hint of what gets executed first,
x * 2 - 1 gives no hint at all.

I think that providing the correct hint is better than not providing any hints (and clearly better than providing the wrong hint!).

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<http://bugs.python.org/issue16239>
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