Following a long discussion on python-ideas, I've posted my draft of
PEP-498. It describes the "f-string" approach that was the subject of
the "Briefer string format" thread. I'm open to a better title than
"Literal String Formatting".

I need to add some text to the discussion section, but I think it's in
reasonable shape. I have a fully working implementation that I'll get
around to posting somewhere this weekend.

>>> def how_awesome(): return 'very'
...
>>> f'f-strings are {how_awesome()} awesome!'
'f-strings are very awesome!'

I'm open to any suggestions to improve the PEP. Thanks for your feedback.