#01 1. Where the GIL Came From and How PEP 703 Removes It
The Global Interpreter Lock has been a sore point for Python programmers since the language's earliest days. It kept C extensions simple and made single-threaded reference counting very fast, but it also reduced modern multi-core CPUs to decoration.
Python 3.13 is the milestone break: with the GIL gone, threads execute Python bytecode in parallel directly, and there is no longer any need to lean on heavyweight multiprocessing IPC just to use more than one core!