This really isn't enough information to know exactly what's going on in your case, but there are things that are known to be slow for CLI startups.  Probably the biggest contributor is pkg_resources.  Of course, that's a third party library that's popular for handling entry points, so it's not really a Python problem.  There are some other third party libraries on PyPI that may be more performant for you.  Entry point handling is something that I'd like to try to address in 3.8 in a manner similar to importlib.resources.