RFC: For Loop Invariants

[Rhodri James]

On 10/04/2020 21:44, Elliott Dehnbostel wrote:
> Hello Everyone,
> 
> I've also posted this to the python-ideas mailing list, but I thought to
> post here as well for a more general audience.
> 
> If I've done this incorrectly, please let me know so that I can
> improve/revise. I'm new to the Python community and quite enjoy the more
> functional features of Python 3, but have I have a peeve about it. I'd like
> to propose and discuss the following enhancement to Python 3:
> 
> *Consider the following trivial for-loop:*
> 
> chars = "abcaaabkjzhbjacvb"
> seek = {'a','b','c'}
> count = 0for a in chars:
>       if a in seek:
>            count += 1
> 
> Gross. Twice nested for a simple count.

a) I don't personally think that's gross (apart from the missing 
newline, which is just an email artefact I assume).

b) If it's simple like this and you care enough, refactor it as a 
comprehension:

   count = sum(1 for a in chars if a in seek)

It it's not so simple, neither the comprehension nor your proposal are 
going to be as readable as the twice nesting.

-- 
Rhodri James *-* Kynesim Ltd