To be even more pedantic, python already runs on multiple cores. They poll the GIL until they can run. I believe some version of Python 3 fixes this behavior so they don't have to poll the GIL.
The GIL is not a spinlock. Since only one core gets the GIL at a time, it's still just using one core (even if that one core is being switched around).
The GIL is released during the execution of some C code, so another thread may execute Python code in the meantime, but that's probably besides the point too.
As we are in the <pedantic> sub-thread, we can point out that actually a Python process can use more than one core at the same time, just trying to acquire the GIL.
This is how Python programs can show up using more than 100% CPU in `top`.
