What the GIL is

Question

What the GIL is

Accepted Answer

The GIL is a design choice in CPython (the reference implementation) that simplifies memory management by ensuring only one thread runs at a time. This means CPU-bound tasks do not truly parallelize with threads - if you spawn 4 threads to crunch numbers, they still take turns rather than running simultaneously. The workarounds are: use multiprocessing (separate processes, each with its own GIL), use I/O-bound threads (threads release the GIL while waiting on I/O), or use a GIL-free runtime like Jython or PyPy-STM.