You can't write code that is guaranteed to work on Python 4, but you definitively can write code that is guaranteed that will not work on Python 4. That's what

You can't write code that is guaranteed to work on Python 4, but you definitively can write code that is guaranteed that will not work on Python 4. That's what this article is about, anyway. Based on the issues with Py3 I'm quite confident that switch from 3 to 4 will be similar as from 1 to 2.