If we're just talking about the python stack arguably there's not much else on top of it. You get the extra stuff through osmosis in the same 1 - 2 years. The applications for python aren't wide ranging enough to include much else unless you're thinking about data science and ML stuff.
I guess it depends on your definition of "senior", but I don't see why language choice should affect it this much, given that much of what makes seniors senior is not knowledge of specific tech, but experience with software engineering as a process.
