Frank Millman wrote: > nagy wrote: > >>Thanks, Kirk. >>I considered the += as only a shorthand notation for the assignment >>operator. >>Since for lists + is simply a concatetation, I am not sure it x=x+[2] >>is creating a brand >>new list. Could you refer me to any documentation on this? >>Thanks, >>Nagy > > > My habit is to check the id. > > >>>>x = [1,2] >>>>id(x) > > -1209327188 > >>>>x += [4] >>>>x > > [1,2,4] > >>>>id(x) > > -1209327188 > >>>>x = x + [6] >>>>x > > [1,2,4,6] > >>>>id(x) > > -1209334664 > > So it looks as if x += [] modifies the list in place, while x = x + [] > creates a new list. > > I am not sure if this is 100% guaranteed,
It is. This is true for any mutable type. > as I have noticed in the past > that id's can be reused under certain circumstances. Perhaps one of the > resident gurus can comment. > -- http://mail.python.org/mailman/listinfo/python-list
