[Numpy-discussion] List of Lists in C

Hanni Ali hanni.ali@gmail....
Mon Jan 26 03:01:57 CST 2009


Correct, however other areas of the application expect an empty list to be
present, otherwise I would have used None.

2009/1/26 Matthieu Brucher <matthieu.brucher@gmail.com>

> 2009/1/26 Hanni Ali <hanni.ali@gmail.com>:
> > Yes fair point, but when it's a empty list and new elements are replaced
> > with a new list instance it's fine, especially as [[]]*100000 is
> > significantly faster than [[] for i in xrange(100000)] as I was
> previously
> > doing.
>
> In this case, why do you put a list in it in the first place ? You
> could put None, and it would be safer ;)
>
> > In fact I think that's partly answered my question [[]]*x must create a
> list
> > of pointers pointing at the same list. Rather than [[] for i in
> > xrange(100000)] which must create a list of new separate lists instances.
> > Hence the significant difference in speed.
> >
> > Hanni
>
> I agree. Less memory allocations and initialization, thus more speed.
>
> Matthieu
> --
> Information System Engineer, Ph.D.
> Website: http://matthieu-brucher.developpez.com/
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> LinkedIn: http://www.linkedin.com/in/matthieubrucher
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