I can’t tell if we’re in agreement or disagreement. I don’t disagree that one should avoid exotic dependencies or unstable behaviors from specific versions of libraries. Version pinning is more about just making sure someone else can run the program. It’s not about (or at least shouldn’t be about) creating a reliance on odd corner case behaviors. We almost never manually pin versions — pip-tools does that automatically.

Your argument probably would be that the dependencies used should be so simple and core that the risk of it not working with someone else’s package set should be minimal or zero. That’s just a bit too extreme for my taste. I want builds to be 100% reproducible. This is exactly what modern build tools for other languages do.

Re: Docker, I don’t think anyone is claiming pip and virtualenv are somehow a replacement for that.

Re: apt-get, we tend to actually avoid this. It’s really not a good package manager at all and can easily break. We’re going in the direction of nix instead and may even port our entire Python workflow over to it or bazel at some point.