>> Python 2->3 transition

> taking backwards compatibility so seriously

Python’s backward compatibility story still isn’t great compared to things like the Go 1.x compatibility promise, and languages with formal specs like JS and C.

The Python devs still make breaking changes, they’ve just learned not to update the major version number when they do so.

Indeed, Python's version format is semver but it's just aesthetics, they remove stuff in most (every?) minor version. Just yesterday I wasted hours trying to figure out a bug before realizing my colleague hadn't read the patch notes.