Question

print sum(1 for x in alist if x[1] == 8)

This code runs fine, but it is so slow. Is there a way better than this. Because, my list is very large and the computation takes a lot of time. Do you know a better and faster way to do it?

Answer 1

You’d have to create indexes or cached counts to speed up such code; trade memory for speed.

Wherever you handle your list (add to it, remove from it, edit entries) you also maintain your indices. For example, if you had a counts dict with ids as keys and their frequency as values, all you had to do is look up the count directly, and ensure that the counts stayed up-to-date as you manipulate alist.

The best way to manage this is by encapsulating your list in a custom type, so that you can control all manipulations of the data structure and maintain the extra information.