Carol, if you're willing to go into the lion's den that is Python-ideas with this, you have my eternal gratitude. :-)

Steven, sorry, there really is no rush. I really don't think I ever said there is. However, I think it would be much easier to change the behavior while the thing is in alpha. Isn't that the purpose of alpha? 

(If I'm wrong here, please disregard. I would be fine to see this happening few years from now. I believe in "Python in the limit", not actual versions, but too many times I have been said "what you ask makes sense in the ideal world, but that ship has sailed long ago".)

Yes, of course (name := expression) is an improvement over what we have now, and I'm grateful for that. It's just that when I explain it to my students (" = is just assignment, := is for assignment and displaying"), I have no good reason to tell them why they must put the parentheses---except "Python is too worried you will make a mistake", and that just doesn't seem like something Python usually does. (That's something Java would do to people.:)

Yes, Jupyter sometimes does allow things that would otherwise be SyntaxErrors (though much less than they used to, since Python gave them a lot of headache by introducing decorators---if you remember that story;), and going to Jupyter was the next thing on my mind after I'm rejected here. I just thought it would be much easier to just allow this "at the source", so Jupyter people don't have to think "what if they finally allow toplevel walruses, but with different semantics (e.g., printing result even if it is None)?".

Carol and Victor, I'm sorry I have usurped a bugtracker issue for this discussion. First, I really thought this is about implementation of assignment expressions, and this is the best place to put it. Second, I didn't expect a discussion---I thought it would be either "that makes no sense, go away" or "yeah, good idea, we'll do it". For the next such issue (there will probably be one:), do you suggest that the more appropriate thing would be to open a new issue?

(Let me just reiterate that I'm not going to python-ideas. You probably can't understand how stressful that place is, but believe me, it is. I'm not the only one that thinks so. If that's the only sanctioned method to improve Python, even when it is about details, then I'll just withdraw from the game.)