I would be grateful for any advice people can offer on the fastest way to count items in a sub-sequence of a large list.
I have a list of boolean values that can contain many hundreds of millions of elements for which I want to count the number of True values in a sub-sequence, one from the start up to some value (say hi). I am currently using: sieve[:hi].count(True) but I believe this may be costly because it copies a possibly large part of the sieve. Ideally I would like to be able to use: sieve.count(True, hi) where 'hi' sets the end of the count but this function is, sadly, not available for lists. The use of a bytearray with a memoryview object instead of a list solves this particular problem but it is not a solution for me as it creates more problems than it solves in other aspects of the program. Can I assume that one possible solution would be to sub-class list and create a C based extension to provide list.count(value, limit)? Are there any other solutions that will avoid copying a large part of the list? -- http://mail.python.org/mailman/listinfo/python-list
