On Wed, Feb 20, 2019 at 5:28 AM Grant Edwards <grant.b.edwa...@gmail.com> wrote: > > On 2019-02-19, Chris Angelico <ros...@gmail.com> wrote: > > On Wed, Feb 20, 2019 at 3:23 AM Grant Edwards <grant.b.edwa...@gmail.com> > > wrote: > > > >> Those object _may_ each have different identies. Is it required that > >> they do? If an assignment is done on name referring to an object with > >> no other references, would it be allowed that the "old" object is > >> destroyed and its ID reused for a new object being created by the RHS > >> of the assignment? > >> > >> Admittedly, that would be a rather odd way to do things. One would > >> expect that first the RHS is evaluated (perhaps creating a new > >> object), then the name is rebound. > > > > Correct, the RHS is evaluated first. So the old object is still > > around (important for statements like "x = x.lower()"). > > Not doing the unbinding until after the RHS evaluation is also > important for preventing surprises due to exceptions raised while the > RHS is evaluated. One would reasonably expect that if that happens > the original binding of the name on the LHS is unchanged. > > Dunno if that's actually specified anywhere... >
It is, yes: https://docs.python.org/3/reference/expressions.html#evaluation-order ChrisA -- https://mail.python.org/mailman/listinfo/python-list
