[StavrosK]

How can you have an upper bound on compatibility? When a library is released, it knows that it works with version 1.3.2 with its dependency, but how can it ever know it doesn't work with 1.4, unless the developer goes back and re-releases the app?

[AgentME]

If the library follows semantic versioning, then you can always declare that you work with everything from the current version to before the next major version.

[StavrosK]

That's what I usually do (although I pin minor, because you never know). I should also be better about following semver, but it just feels wrong to have your library be at version 5.43.55 :/

[sametmax]

Python 2.7 <=> Python 3