Most new modules in the standard library come with that warning. It's pragmatic. Python has a relatively large standard library (one of its selling points), an

Most new modules in the standard library come with that warning. It's pragmatic. Python has a relatively large standard library (one of its selling points), and not everything in the standard library can be right the first time. No matter how long a Python release spends in beta, there are probably flaws that will only be discovered when people start using new modules to do their actual jobs (where they won't be using a beta version of Python). In Python 1 and 2, if a standard library module had a flaw that required a backwards-incompatible change to fix, the flaw would have to remain there. In Python 3 they acknowledge that the first version may require backwards-incompatible changes.