Carl M. Johnson wrote:
Agreed, sure, we have to treat the LHS of = as a local. But += is fundamentally different.
No it's not. It is fundamentally the same. Augmented assignment in Python *is* assignment, equivalent to x = x.__iadd__(other). That alone should be enough to kill this proposal stone dead. += is not, except by accident, an in-place addition operator. It is always a re-binding. (Mutable objects are free to mutate in place, if they choose, but the re-binding still takes place.)
You cannot have a += statement unless somewhere out there there is a matching = statement. It cannot exist independently. It never works on its own.
Neither does *any* attempt to access an unbound local. Python doesn't, and shouldn't, try to guess what you actually intended so as to make it work. If you want x to refer to a nonlocal, or a global, declare it as such. print x; x = 1 will fail unless there is an earlier x = something. x = x+1 will fail unless there is an earlier x = something. x += 1 will fail unless there is an earlier x = something. Why single out x += 1 for changed semantics to the rule that any assignment makes x a local? What if you don't have a non-local x, should Python guess that you wanted a global? Currently, the rule is simple: any assignment tells the compiler to treat x as local. If you want nonlocal or global, you have to declare it as such. Nice and simple. What actual real-world problem are you trying to solve that you want to change this behaviour? -1 on this change. -- Steven