TL;DR:
+1 for the idea-1 on the propagating member-access or index operators
+1 on spelling it "or?"
C# has had null-coalescing since about 2005, and it's one feature I miss in every other language that I use. I view null/None as a necessary evil, so getting rid of them as soon possible is a good thing in my book. Nearly every bit of Python I've ever written would have benefitted from it, if just to get rid of the "x if x is not None else []" mess.
That said, I think the other (propagating) operators are a mistake, and I think they were a mistake in C# as well. I'm not I've ever had a situation where I wished they existed, in any language. Better to get rid of the Nones as soon as possible than bring them along. It's worth reading the C# design team's notes and subsequent discussion on the associativity of "?." [1] since it goes around and around with no really good answer and no particularly intuitive behaviour.
Rather than worry about that, I'd prefer to see just the basic None-coalescing added. I like Alessio's suggestion of "or?" (which seems like it should be read in a calm but threatening tone, a la Liam Neeson). It just seems more Pythonic; ?? is fine in C# but seems punctuation-heavy for Python. It does mean the ?= and ?. and ?[] are probably out, and I'm OK with that.
- Jeff