Import magic ends up causing all kinds of problems. There's no way to tell it "I just want to import your classes; I don't want you to patch!" without literally patching the library.
In general, I'm a fan of "let me call the initializer myself, at program startup." It's especially important when you want reversibility, i.e. teardown in addition to initialization, which pops up all the time for unit tests.
Also networking/web apps with lifecycle hooks, where careless import-time logic can break the setup procedures. To quote zen of python, "explicit is better than implicit"
In general, I'm a fan of "let me call the initializer myself, at program startup." It's especially important when you want reversibility, i.e. teardown in addition to initialization, which pops up all the time for unit tests.