[Tim]
I expected that, given that expressions "naturally nest", chained targets could still be specified:
a := b := c:= 5
but since they're all plain names there's no way to tell whether the bindings occur "left to right" or "right to left" short of staring at the generated code.
[Nick Coghlan <ncoghlan@gmail.com>]
The fact class namespaces are ordered by default now allow us to demonstrate the order of multiple target assignments and tuple unpacking without staring at generated code:
class AssignmentOrder: ... a = b = c = 0 ... d, e, f = range(3) ... class ReversedAssignmentOrder: ... c = b = a = 0 ... f, e, d = range(3) ... [attr for attr in AssignmentOrder.__dict__ if not attr.startswith("_")] ['a', 'b', 'c', 'd', 'e', 'f'] [attr for attr in ReversedAssignmentOrder.__dict__ if not attr.startswith("_")] ['c', 'b', 'a', 'f', 'e', 'd']
So that's a situation where "name = alias = value" could end up matching "alias := name := value"
Cool! So this is really a killer-strong argument for getting rid of classes - way overdue, too ;-)
(Even in earlier versions, you can illustrate the same assignment ordering behaviour with the enum module, and there it makes even more of a difference, as it affects which name binding is considered the canonical name, and which are considered aliases).
So if binding expressions can be chained, they'll need to ape "left-to-right" binding order. Or they can't be allowed to chain to begin with. Either way would be fine by me.