For that reason, I'd like to make a more modest proposal
to *only* add a verbatim versions of keywords as necessary,
e.g., "\where" or "\given". That way, there will be no
temptation to use that syntax in any other place. If a new
version of Python comes out with a new keyword, say "abc",
then all of the old Python versions can get a minor revision
that knows about "\abc". This would ensure that the
backslash syntax is only used to avoid collisions with new
keywords.
When 3.7 hits end-of-life, the "\given" (or whatever) can
be deprecated.