I don't think "without breaking anyone's code" even needs to be a goal. Python has rolling deprecations and feature removals planned in the 3.x release series,

I don't think "without breaking anyone's code" even needs to be a goal. Python has rolling deprecations and feature removals planned in the 3.x release series, and careful such feature transitions could be used to help JIT features or similar, too. To back up that fact: Python 3.10 will remove long-deprecated features, see issue tracker: https://bugs.python.org/issue41165 https://bugs.python.org/issue41165 and What's new, the Removed section: https://docs.python.org/3.10/whatsnew/3.10.html#removed https://docs.python.org/3.10/whatsnew/3.10.html#removed