On 10/9/06, Edward Waugh <[EMAIL PROTECTED]> wrote: > Consider the following (working) Python code: > > import sys > > def sum(list): > # total = 0 does not work for non-numeric types > total = list[0].__class__() > for v in list: > total += v > return total > > l = [1, 2, 3] > print sum(l) > > l = [1.1, 2.2, 3.3] > print sum(l) > > l = ["a", "b", "c"] > print sum(l) > > In order for sum() to be generic I initialize total to the value of > list[0].__class__(). This works but I would like to know if this is the > correct or preferred way of doing it. It means that sum() must be given a > list whose elements are types or classes that have a no-arg constructor > (through this is probably almost always the case). >
I'd do this: >>> def sum(list): ... total = list[0] ... for v in list[1:]: ... total += v ... return total I'm not sure if regular slice notation makes a copy of the list or not, if it does you can use itertools: >>> def sum(list): ... total = list[0] ... for v in itertools.islice(list, 1, len(list)): ... total += v ... return total > Thanks, > Edward > -- http://mail.python.org/mailman/listinfo/python-list
