Flattening lists

Rhamphoryncus rhamph at gmail.com
Fri Feb 6 22:23:48 CET 2009


On Feb 5, 1:16 pm, Michele Simionato <michele.simion... at gmail.com>
wrote:
> On Feb 5, 7:24 pm, a... at pythoncraft.com (Aahz) wrote:
>
> > In article <a22c77c4-a812-4e42-8972-6f3eedf72... at l33g2000pri.googlegroups.com>,
> > Michele Simionato  <michele.simion... at gmail.com> wrote:
>
> > >Looks fine to me. In some situations you may also use hasattr(el,
> > >'__iter__') instead of isinstance(el, list) (it depends if you want to
> > >flatten generic iterables or only lists).
>
> > Of course, once you do that, you need to special-case strings...
>
> Strings are iterable but have no __iter__ method, which is fine in
> this context, since I would say 99.9% of times one wants to treat them
> as atomic objects, so no need to special case.

Don't worry, that little oddity was fixed for you:

Python 3.0+ (unknown, Dec  8 2008, 14:26:15)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> str.__iter__
<slot wrapper '__iter__' of 'str' objects>
>>> bytes.__iter__
<slot wrapper '__iter__' of 'bytes' objects>
>>> bytearray.__iter__
<slot wrapper '__iter__' of 'bytearray' objects>


I'm in the "why do you need more than 1 depth?" camp.  Dispatching
based on your own type should be given an extra look.  Dispatching
based passed in types should be given three extra looks.

I didn't realize itertools.chain(*iterable) worked.  I guess that
needs to be pushed as the canonical form.



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