> >From that link: > > > > """ > > An augmented assignment expression like x += 1 can be rewritten as x = > > x + 1 to achieve a similar, but not exactly equal effect. In the > > augmented version, x is only evaluated once. Also, when possible, the > > actual operation is performed in-place, meaning that rather than > > creating a new object and assigning that to the target, the old object > > is modified instead. > > """ > > > > The significance here is that the augmented assignment may not > > necessarily be at all comparable to the non-augmented version, but > > ought to have *approximately* the same *intention*.
This is not my reading. > > of situations where the two will differ, eg when there are multiple > > references to the same object: > > > > >>> a = b = [1,2] > > >>> a += [3] > > >>> a,b > > ([1, 2, 3], [1, 2, 3]) > > >>> a = a + [4] > > >>> a,b > > ([1, 2, 3, 4], [1, 2, 3]) > > OK but this behavior is in conformance with the Reference Manual (cf. your quote above : "when possible, the actual operation is performed in-place"). This is not my point because the doc explictly claims that "an augmented assignment [...] performs the binary operation specific to the type of assignment on the two operands". -- https://mail.python.org/mailman/listinfo/python-list
