Like Antoine, I don’t think the change is huge. I agree with his points and I’ll add a few extra bits of context:
- “pure” Python code doesn’t require any changes to continue working. The exception is that there are some bugs that are triggered rarely with the GIL (maybe 1 in a million runs) but are triggered much more often without the GIL because thread “interleavings” happen much more often without the GIL. I’ve found and fixed a few of these bugs in CPython (and occasionally written a few of these sorts of bugs in packages I’ve worked on.)
- Most C API extensions don’t require any changes, and for those that do require changes, the changes are small. For example, for “nogil” Python I’m providing binary wheels for ~35 extensions that are slow or difficult to build from source and only about seven projects required code changes (PyTorch, pybind11, Cython, numpy, scikit-learn, viztracer, pyo3). For four of those projects, the code changes have already been contributed and adopted upstream. For comparison, many of those same projects also frequently require changes to support minor releases of CPython.
I don’t have a strong opinion about version numbering, but if the PEP were adopted and labeled as Python 4, I would like to avoid using the version bump as an opportunity to introduce other backwards incompatible changes.
EDIT: six → seven projects