On May 6, 12:56 am, John O'Hagan <resea...@johnohagan.com> wrote: > On Tue, 5 May 2009, Sion Arrowsmith wrote: > > John O'Hagan <resea...@johnohagan.com> wrote: > > >I can see that it's tantalizing, though, because _somebody_ must know > > > about the assignment; after all, we just executed it! > > > Except we haven't, if we're talking about reporting from the > > > object's __init__: > > >>> class Brian: > > > ... def __init__(self): > > ... print "I'm Brian!" > > ... > > > >>> l = [] > > >>> l[1] = Brian() > > > I'm Brian! > > Traceback (most recent call last): > > File "<stdin>", line 1, in <module> > > IndexError: list assignment index out of range > > > (Yeah, I know that's a setitem call not an assignment. Point stands. > > It also demonstrates why the whole idea of "what name is a newly- > > created object assigned to" is broken.) > > I guess what I meant was that if I type: > > brian = Brian() > > in the python shell and then hit return, it seems to me that _somewhere_ (in > the interpreter? I have no idea how it's done) it must be written that the > new Brian object will later be assigned the name "brian", even as the process > of creating the instance begins. As you've just demonstrated, the actual > assignment occurs afterwards. > > But even if this is true I'm guessing it'd be black magic to get to it. > > Regards, > > John
In principle, you can't get all the names an object is bound to, since it might be a temporary value or member of a container at some time. If it was in a dictionary, would you want its key? Or sequence and index? Furthermore, we don't have a data structure for two-way lookup. Sometimes you would want to lookup name by object, sometimes object by name. Lastly, it would make code significantly less readable </subjective>. -- http://mail.python.org/mailman/listinfo/python-list
