Jeremy Winters napisal(a): > class SegmentValue: > def > __init__(self,seg=[0,0,0,0,0,0],value=0,description=""): > self.segment=seg > self.value=value > self.description=description > > #that's my class! note the default of a 6 item list > for the seg parameter... which is then bound(?) to the > segment attribute of the instance... > > now here's the session I just did > > >>> from SegmentValue import * > >>> a=SegmentValue([1,2,3,4,5,6],22,"segment a") > >>> b=SegmentValue() > >>> c=SegmentValue() > >>> b.segment[0]=1 > >>> b.segment > [1, 0, 0, 0, 0, 0] > >>> c.segment > [1, 0, 0, 0, 0, 0] > >>> a.segment > [1, 2, 3, 4, 5, 6] > > so... what I'm seeing here is that when I explicitly > set seg during instantiation... it creates a unique > sequence that can be manipulated without affecting > other instances... but if I instantiate using the > default... it seems to refer back to the default when > maniuplating the segment attribute. > > in a continuation of the session... > > >>> d=SegmentValue() > >>> d.segment > [1, 0, 0, 0, 0, 0] > > ...you'll note that any new instances now refer to the > *modified default sequence*. > > what is going on here? how do I instantiate without > explicitly defining a new sequence each time? or is > this even possible? > > thanks in advance, > jeremy > Read the doc: http://docs.python.org/tut/node6.html#SECTION006710000000000000000 Important warning: The default value is evaluated only once.
-- http://mail.python.org/mailman/listinfo/python-list
