[Python-Dev] Adding concat function to itertools

[Mike Klaas]

On 28-Sep-07, at 10:45 AM, Raymond Hettinger wrote:

> [Bruce Frederiksen]
>>>  I've added a new function to itertools called 'concat'.  This  
>>> function is
>>> much like chain, but takes all of the iterables as a single  
>>> argument.
>
> Any practical use cases or is this just a theoretical improvement?
>
> For Py2.x, I'm not willing to unnecessarily expand the module.
> However, for Py3k, I'm open to changing the signature for chain().

For me, a fraction of chain() uses are of the * variety:

d = defaultdict(list)
allvals = chain(*d.values())

return chain(*imap(cache.__getitem__, keylist))

Interestingly, they seem to all have something to do with dictionary  
values() that are themselves iterable.

-Mike