Paul McGuire wrote:
Pythonistically speaking, even though a dict is a mutable thing, I'm learning that the accepted practice for methods like this is not so much to update in place as it is to use generator expressions to construct a new object.
I disagree. The convention is that mutation methods should return None. > For example, given a list of integers to 100,
instead of removing all of the even numbers (with the attendant hassles of updating a list while iterating over it), just create a new list of the numbers that are not even.
This is because each removal is O(n), making the entire process O(n*2), whereas a new list is O(n) -- and the hassle of remembering to iterate in reverse when doing removals.
Perhaps I am overgeneralizing from comments I have read here on c.l.py about creating new lists instead updating old ones.
I think so. Removals and insertions are importantly different from change in place. If I wanted to square each number in a list, and *did not need the original list*, I would not hesitate to do it in place.
The newish sorted() and reversed() built-ins were meant to complement list.sort and list.reverse, not replace them.
tjr -- http://mail.python.org/mailman/listinfo/python-list
