Don't run any functions at the root level of your module. Instead, if you really need long-lasting objects which get initiated once, then use an object, and pu

Don't run any functions at the root level of your module. Instead, if you really need long-lasting objects which get initiated once, then use an object, and put any initialisation stuff in it's `__init__` method. Then the module can be imported whenever, but your initialisation stuff is only called when the user of your library creates a new instance of that class. For bonus points, make your classes able to be used with the `with ...` syntax, so then lifetime is kept to a minimum, and errors/whatever are dealt with by default. If you really really need to monkey around and take control of the whole python interpreter (gevent, twisted, and possibly some GUI frameworks come to mind...) then don't do that at import time, do it with a `run_forever()` or `take_control` type function. But yes, a virtualenv for every project does help a lot with not accumulation cruft.