How to detect the last element in a for loop

[Tom Verbeure]

Hello All,

I often have the case where I need to loop through a bunch of elements, but 
do something special on for the last line of code. 

Currently, I can solve it this way:

    first = 1
    for port in self.portDefsList:
        if first == 0:
            string += ", "
        else:
            first = 0
        string += str(port)
        pass

This works fine, but it introduces an extra variable. Is there a cleaner 
way to do this?

Thanks,
Tom