when reading PEP 572 I actually liked it a lot - I think it's actually a cool idea. I think it's actually that cool an idea that it should be made the default way of doing an assignment, over time phasing out the good ole =.
This would have several benefits:
in this case, for sure, we should make it possible to chain :=s, for example by making it bind right-to-left, so that a := b := 3 would be a := (b := 3)
I'm sorry if somebody brought that up already, but the discussion has grown so huge that I couldn't read through it entirely.