PEP-505 isn't anywhere close to being finished. I only submitted the draft because somebody off list asked me to send a draft so I could get a PEP number assigned. So I literally sent him what I had open in my text editor, which was just a few minutes of brain dumping and had several mistakes (grammatical and technical).

If there's absolutely no point in continuing to work on it, I'll drop it. But from the outset, I thought the plan was to present this in its best light (and similar to the ternary operator PEP, offer several alternatives) if for no other reason than to have a good record of the reasoning for rejecting it.

I'm sorry if I misunderstood the PEP process; I would have kept it to myself longer if I knew the first submission was going to be reviewed critically. I thought this e-mail chain was more of an open discussion on the general idea, not specifically a referendum on the PEP itself.

On Mon, Sep 21, 2015 at 11:40 AM, Guido van Rossum <guido@python.org> wrote:
Just to cut this thread short, I'm going to reject PEP 505, because ? is just too ugly to add to Python IMO. Sorry.

I commend Mark for his clean write-up, without being distracted, giving some good use cases. I also like that he focused on a minimal addition to the language and didn't get distracted by hyper-generalizations.

I also like that he left out f?(...) -- the use case is much weaker; usually it's the object whose method you're calling that might be None, as in title?.upper().

Some nits for the PEP:

- I don't think it ever gives the priority for the ?? operator. What would "a ?? b or c" mean?
- You don't explain why it's x ?? y but x ?= y. I would have expected either x ? y or x ??= y.
- You don't explain or show how far ?. reaches; I assume x?y.z is equivalent to None if x is None else x.y.z, so you don't have to write x?.y?.z just to handle x.y.z if x is None.
- The specification section is empty.

--
--Guido van Rossum (python.org/~guido)



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Mark E. Haase
202-815-0201