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 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 2009/1/26 Matthieu Brucher <matthieu.bruc...@gmail.com> > Hi, > > Don't remember that you are using the same list in each element of the > outer list. If you don't want this, use [[] for i in range(5)]. I > don't think there is another way in C either (or too complicated). > > Matthieu > > 2009/1/26 Hanni Ali <hanni....@gmail.com>: > > Hi, > > > > Quick question, I've been doing a fair bit of extension writing in C > > recently, but wondered how best to implement: > > > >>>> l = [[]] * 5 > > > > to create a list of a given length containing the initialization variable > > desired. > > > > A loop seems the straight forward manner, but I would have thought there > was > > a more efficient way... > > > > > > Currently I just do it in Python and pass through the already initialized > > list as it seems perfectly efficient. > > > > Cheers, > > > > Hanni > > > > > > > > _______________________________________________ > > Numpy-discussion mailing list > > Numpy-discussion@scipy.org > > http://projects.scipy.org/mailman/listinfo/numpy-discussion > > > > > > > > -- > Information System Engineer, Ph.D. > Website: http://matthieu-brucher.developpez.com/ > Blogs: http://matt.eifelle.com and http://blog.developpez.com/?blog=92 > LinkedIn: http://www.linkedin.com/in/matthieubrucher > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion >
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