In the ideal world, library developers would properly use the python_requires[1] option and dependency resolvers would correctly identify the latest version of

In the ideal world, library developers would properly use the python_requires[1] option and dependency resolvers would correctly identify the latest version of a library that works with the installed version of Python. Unfortunately I have found that is not always the case. When I make public modules, I personally weigh whether using a new feature is worth losing users stuck on an older version. That sweet spot for me right now is targeting Python 3.6 and using backported modules where necessary (e.g. mypy-extensions). I'm a big type hint fan and type hinting became much more usable in >= 3.6. [1] https://packaging.python.org/guides/distributing-packages-using-setuptools/#python-requires https://packaging.python.org/guides/distributing-packages-us...