On Fri, Feb 5, 2010 at 11:31 AM, Gerald Britton <gerald.brit...@gmail.com> wrote: > I think it's because when you do ['a'].extend([]) or whatever, the > result is whatever the method "extend" returns. But "extend" has no > return value, hence you will see None if you do this interactively. >
That sums it up. In Python the convention is to raise an exception on error, return a new value in the case where a new value is created, and - as in this case - to return None for modification of an existing value. Returning "None" is vexing if you are used to another language that has a different convention but is expected for well behaved python libraries. So yeah, Python does it that way because the intent is to loudly and regularly announce that something was modified or to loudly and regularly announce that something new was /not/ created. It's a boring story with no whiz-bang feature behind it, but I like that the language behaves that way for exactly that reason. -Jack -- http://mail.python.org/mailman/listinfo/python-list
