On 22/04/2013 17:06, Oscar Benjamin wrote: > On 22 April 2013 16:50, Blind Anagram <blindanag...@nowhere.org> wrote: >>> >>> It would be very easy to subclass list and add this functionality in >>> cython if you decide that you do need a builtin method. > [snip] >> >> But I was really wondering if there was a simple solution that worked >> without people having to add libraries to their basic Python installations. > > There are simple solutions and some have already been listed. You are > attempting to push your program to the limit of your hardware > capabilities and it's natural that in a high-level language you'll > often want special libraries for that.
Hi Oscar Yes, but it is a tribute to Python that I can do this quite fast for huge lists provided that I only count on the full list. And, unless I have completely misunderstood Python internals, it would probably be just as fast on a sub-sequence if I had a list.count(value, limit) function (however, I admit that I could be wrong here since the fact that count on lists does not offer this may mean that it is not as easy to implement as it might seem). > I don't know what your application is but I would say that my first > port of call here would be to consider a different algorithmic > approach. An obvious question would be about the sparsity of this data > structure. How frequent are the values that you are trying to count? > Would it make more sense to store a list of their indices? Actually it is no more than a simple prime sieve implemented as a Python class (and, yes, I realize that there are plenty of these around). > If the problem needs to be solved the way that you are currently doing > it and the available methods are not fast enough then you will need to > consider additional libraries. >> >> As I have never tried building an extension with cython, I am inclined >> to try this as a learning exercise if nothing else. > > I definitely recommend this over writing a C extension directly. Thanks again - I will definitely look at this. Brian -- http://mail.python.org/mailman/listinfo/python-list
