Hi, I am looking for a fast internal vector representation so that (a1,b2,c1)+(a2,b2,c2)=(a1+a2,b1+b2,c1+c2).
So I have a list l = ['a'a,'bb','ca','de'...] I want to count all items that start with an 'a', 'b', and 'c'. What I can do is: count_a = sum(int(x[1]=='a') for x in l) count_b = sum(int(x[1]=='b') for x in l) count_c = sum(int(x[1]=='c') for x in l) But this loops through the list three times, which can be slow. I'd like to have something like this: count_a, count_b, count_c = sum( (int(x[1]=='a',int(x[1]=='b',int(x[1]=='c') for x in l) I hesitate to use numpy array, because that will literally create and destroy a ton of the arrays, and is likely to be slow. -- http://mail.python.org/mailman/listinfo/python-list
