Explain the concept of GIL in Python and its impact on multithreading.

GIL (Global Interpreter Lock) is a mechanism in CPython that ensures that at any given moment, only one thread executes Python bytecode.

This means that multithreading in Python is limited: even if you have multiple threads, they cannot execute Python code simultaneously, which reduces the efficiency of multithreading for CPU-intensive tasks.

However, GIL does not prevent parallel execution of I/O operations, so multithreading is useful for I/O-bound tasks.

To bypass GIL limitations, the following are used:

• Multiprocessing, where each process has its own interpreter and GIL.
• Using alternative Python implementations without GIL (e.g., Jython, IronPython).
• Writing critical sections in C or using extensions that release the GIL.