What is GIL in Python?

GIL (Global Interpreter Lock) is a mechanism in CPython, the main implementation of Python, which ensures that only one thread executes Python bytecode at a time. This is done to simplify memory management and prevent issues with concurrent access to objects.

Due to the GIL, multithreaded programs in Python cannot effectively utilize multiple CPU cores for compute-intensive tasks, as threads do not run in parallel but rather take turns.

However, the GIL does not hinder multithreading in I/O-bound tasks, where threads often block and release the GIL, allowing other threads to run.

To bypass GIL limitations, the following are used:

• Multiprocessing (the multiprocessing module), where each process has its own interpreter and GIL.
• Using alternative Python implementations without GIL (e.g., Jython, IronPython).
• Calls to native libraries that release the GIL during execution.