On Sat, Feb 21, 2009 at 2:55 PM, spir <[email protected]> wrote: > Le Sat, 21 Feb 2009 11:38:49 -0800, > Moos Heintzen <[email protected]> s'exprima ainsi: > >> Hi, >> >> This behavior was totally unexpected. I only caught it because it was >> the only thing I changed.
Yes, it is a common trap and a FAQ: http://effbot.org/pyfaq/why-are-default-values-shared-between-objects.htm >> I guess I have to do it like this. It seems to work. (i.e. every foo >> instance with default lst now has a unique new list.) >> >> def__init__(self, lst=None): >> self.items = lst or [] > > This is the right remedy. Except that I would write > self.items = [] if lst is None else lst > to avoid "tricking" with bools (personal taste). These two versions have different behaviour if an empty list is passed in. Most likely the second one will be what was intended. Kent _______________________________________________ Tutor maillist - [email protected] http://mail.python.org/mailman/listinfo/tutor
