[Numpy-discussion] List of Lists in C

[Matthieu Brucher]

2009/1/26 Hanni Ali <hanni.ali at 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
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