Sometimes, an app or library developer wants to target multiple Linux distributions. For example, I want my own Python apps to work equally well on Debian olds

Sometimes, an app or library developer wants to target multiple Linux distributions. For example, I want my own Python apps to work equally well on Debian oldstable (which currently provides Python 3.9) and Arch Linux (currently on 3.11). That means that I’m going to choose the lowest common version (3.9) as the language level for my app or library. And if I program against a 3.9 language level, I absolutely *refuse* to use any other interpreter than a 3.9 one at development time. (If I used a newer one, then my linter and type checker would helpfully give me false alarms all the time, unaware of the actual language level.) Hence, I use pyenv and poetry to get exactly the interpreter for the language level I want, and to allow pylint and mypy to be perfectly aware of the language level I’m using at development time, allowing them to give me findings that actually make sense.