What is the Python Global Interpreter Lock

Short answer

The GIL is a mutex that prevents multiple native threads from executing Python bytecode simultaneously. It simplifies memory management but limits thread-based parallelism for CPU-bound tasks. For CPU-bound parallelism, see how to use python multiprocessing module. For asynchronous I/O, see python asyncio.

Steps

1. Recognize that threads in CPython do not run Python code in parallel
2. Use multiprocessing for CPU-bound work to bypass the GIL
3. Use threading for I/O-bound work where the GIL is released
4. Consider alternative interpreters like Jython or IronPython
5. Profile your application to identify true bottlenecks

Tips

• C extensions can release the GIL during long computations
• For many workloads, asyncio and multiprocessing together work best
• For profiling code, see how to profile python code for performance