Can you provide an example of where Python has broken backwards compatibility recently between 3.x version? I'll admit (despite googling for 5 or so minutes) that i don't actually know if it does. It obviously breaks forward compatibility continuously all the time - new language features are landing, and they just aren't present in previous versions - but I don't know if I've ever run into people being tripped up by that.

I know some Python Libraries break backwards compatibility (Pandas being a big one) - but, for the most part, hasn't the language been backwards compatible since at least Python 3.4? (And possibly further back, for all I know).

On this page you'll see them. Check the "Porting to X.X" items under each release:

https://docs.python.org/3/whatsnew/index.html

Keep in mind they have deferred a number of them because of the impending EOL of Python 2.7. There are fewer breaking changes during the latter 3.X series, which should resume in 3.9 or 3.10 now that Python2 has passed on.

Here's a commonly mentioned one:

Changes in Python Behavior: async and await names are now reserved keywords. Code using these names as identifiers will now raise a SyntaxError. (Contributed by Jelle Zijlstra in bpo-30406.)

Note: I think this is a bad idea, I'd rather all these small breaking changes and parser be deferred to 4.X. But they need to be small breaking changes, of course, not a new language.

async keyword 3.5

If we look back in python history, the rolling breaking changes have been handled mostly fine, and the actual Python 3 caused a lot of pain in the ecosystem. So I hope they stay away from major versions and keep up the other things they are doing.

That was due to the scope of the breakage, not number format. A good way to handle that and maintain predictability is to constrain breaking changes, yet defer them to 4.X.