Initializing a list with copies

[Ralf Juengling]

Alex Martelli <aleax at aleax.it> writes:

> Ralf Juengling wrote:
>         ...
> > BTW: It is not easy to add __iter__ to list's meta-type, is it?
> 
> And giving list a different metaclass than all the other types
> would no doubt be weird.

agree.

> Further, it would be utterly weird if 'take' was introduced,
> operated correctly on iterables (including iterators), but
> returned a list rather than an iterator!  It would freak me
> out... we finally have a 'lazy' paradigm, and we'd just
> throw it away like this?!  take and drop should both accept

I see what you mean from what I left out (i.e. that your version
of take(n, it) yields an iterator that raises StopIteration at the 
latest after n calls to it.next()).

However, I think it's good idea to let take() yield a list of
elements and drop() an iterator. Why this difference? Iterators 
are potentially "lists whithout end". But they always have *one* 
tail, i.e. a beginning.
I think of take() as of a convenient way to 'take' some elements
from the beginning of the list at once (which I would do otherwise 
by repetitive calls the iterators next method) and of drop() as of
a convenient way to drop some of these elements I'm not interested 
in.

So we wouldn't through away the 'lazy paradigm' with a take()
that yields a list. We would just use take() in cases where we 
actually want some elements at once, e.g. here:

> >>> List2D = list(take(5, iter(list, '')))
> >>> List2D
> [[], [], [], [], []]
> >>>

Ralf