> Pypi has what, 500k projects on it? Many abandoned. Most of them don't contain C extensions. > Whom exactly is going to update those? Its developers of cou

> Pypi has what, 500k projects on it? Many abandoned. Most of them don't contain C extensions. > Whom exactly is going to update those? Its developers of course. Many are presumably watching PEP-703, others will require lobbying by their users. But there is no rush to do so because... > Or do packages get an automatic “doesn’t work with no-GIL” unless the author explicitly opts to enable it? > Or do we live in a future where any package, with any dependency may or may not have undefined behaviour in no-GIL mode? ... the interpreter will indeed fall back to enable the GIL if an extension is loaded that doesn't declare support of the no-GIL mode. Additionally, some extensions are actually safe to use without GIL as long as their Python APIs prevent concurrent access to them and thus act like the GIL themselves. In these cases, the interpreter can be forced to run without the GIL. Isolating the C extension to another process is another possibility to reduce the impact on applications where all others can already run without the GIL. Actually, multiprocessing is already a common approach in the Python ecosystem for concurrent and parallel processing.