[Python-ideas] + operator on generators

[Stephan Houben]

Hi Steven,

To put this into perspective, I did some greps on Sagemath,
being the largest Python project I have installed on this machine
(1955 .py files).

Occurrences:
enumerate: 922
zip: 585
itertools.product: 67
itertools.combinations: 18
itertools.islice: 17
chain: 14 (with or without itertools. prefix)

This seems to confirm my gut feeling that "chain" just isn't that
common an operation;
even among itertools functions, product, combinations and islice are
more common.

Based on this I would say there is little justification to even put
"chain" in builtins,
let alone to give it dedicated syntax.

I also note that * for repetition is only supported for a few
iterables (list, tuple),
incidentally the same ones which support + for sequence chaining.

Stephan




2017-06-27 12:38 GMT+02:00 Steven D'Aprano <steve at pearwood.info>:
> On Tue, Jun 27, 2017 at 11:01:32AM +0200, Stephan Houben wrote:
>> Hi all,
>>
>> Is "itertools.chain" actually that common?
>> Sufficiently common to warrant its own syntax?
>
> I think it's much more common than (say) sequence repetition:
>
> a = [None]*5
>
> which has had an operator for a long, long time.
>
>> In my experience, "enumerate" is far more common
>> among the iterable operations.
>> And that doesn't have special syntax either.
>
> True. But enumerate is a built-in, and nearly always used in a single
> context:
>
> for i, x in enumerate(sequence):
>     ...
>
> A stranger to Python could almost be forgiven for thinking that
> enumerate is part of the for-loop syntax.
>
> In contrast, chaining (while not as common as, say, numeric addition)
> happens in variable contexts: in expressions, as arguments to function
> calls, etc.
>
> It is absloutely true that this proposal brings nothing new to the
> language that cannot already be done. It's syntactic sugar. So I guess
> the value of it depends on whether or not you chain iterables enough
> that you would rather use an operator rather than a function.
>
>> A minimal  proposal would be to promote "chain" to builtins.
>
> Better than nothing, I suppose.
>
>
>
> --
> Steve
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