[Python-ideas] Batching/grouping function for itertools

[Steven D'Aprano]

On Sun, Dec 08, 2013 at 01:30:56PM +0200, Serhiy Storchaka wrote:
> 08.12.13 11:25, Steven D'Aprano написав(ла):
> >In the second case, there is a question about what to do with sequences
> >that are not a multiple of the window size. Similar to zip(), there are
> >two things one might do:
> >
> >- pad with some given object;
> >- raise an exception
> 
> 3) emit last chunk incompleted;

Given a window size of two, and input data [a, b, c], are you suggesting 
a variety that returns this?

(a,b), (c,)

There is no need for a separate function for that. Given a version that 
takes a pad object, if the pad argument is not given, return a partial 
chunk at the end.


> 4) skip incomplete chunk.

The very next sentence in my post references that:

"If you want to just ignore extra items, just catch the exception and
continue."

There is no need for an extra function covering that case.


> There is also a question about result's type. Sometimes you need an 
> iterator of subsequences (i.e. split string on equal string chunks), 
> sometimes an iterator of iterators is enough.

None of the other itertools functions treat strings specially. Why 
should this one? If you want to re-join them into strings, you can do so 
with a trivial wrapper:

(''.join(elements) for elements in group("some string", 3, pad=' '))

ought to do the trick, assuming group returns tuples or lists of 
characters.

Re-combining the iterated-upon elements into the input type is not the 
responsibility of itertools.



-- 
Steven