[Python-ideas] Reduce/fold and scan with generator expressions and comprehensions

[Paul Moore]

On 23 October 2016 at 17:10, Danilo J. S. Bellini
<danilo.bellini at gmail.com> wrote:
>> Ah, that makes SIX existing solutions. Do we need a seventh?
>
> It might have dozens of solutions, perhaps an infinity of solutions.
> Brainfuck and assembly can be used, or even turing machine instructions...
>
> But there should be one, and preferably only one, OBVIOUS way to do it.
> Readability counts.

Sure, but you haven't explained why your proposal is more obvious than
any of the other six. Built in does not equate to obvious. More
obvious is often to have a dedicated tool, in a module designed to
provide tools in that particular area. That's partially why reduce got
moved to the functools module (another part is the fact that Guido
doesn't find functional-style approaches that "obvious" - and what's
obvious to a Dutchman is the benchmark here :-))

I'm not against powerful "windowed function" capabilities - my
background is SQL, and windowed functions in SQL have even more power
than the sort of thing we're talking about here. But I wouldn't call
them "obvious" - at least not based on the number of times I get to do
explanations of them to colleagues, or the number of tutorials on them
I see. So the idea seems fine to me, but I'd very definitely class it
as an "advanced" feature, and typically that sort of feature in Python
is handled in a library.

> Reduce lost the built-in status on Python 3. Lambdas lost the decomposing
> arguments like "lambda (a, b), c: a + b * c".

Which can be interpreted as evidence that this type of approach is not
considered a core feature.

In general, I like the idea, but I don't think it fits well in Python
in its proposed form.

Paul