Why is GIL needed at all, given that it imposes such restrictions?

GIL (Global Interpreter Lock) is a mechanism in CPython that ensures only one thread executes Python bytecode at any given time. This limitation is related to the memory management and internal structures of the interpreter, which are not thread-safe.

Why it is needed:

• It simplifies the implementation of the interpreter, avoiding complex issues with concurrent access to objects and garbage collection.
• It simplifies the development of C extensions, which do not need to worry about multithreading.

Although the GIL limits parallel execution of threads in CPU-bound tasks, it does not hinder multithreading in I/O-bound operations, where threads often wait for external resources.

To bypass GIL limitations, multiprocessing, alternative Python implementations (Jython, IronPython), or C extensions that release the GIL during heavy computations are used.