What restrictions does the global interpreter lock impose in Python and how does it affect multithreading?

The Global Interpreter Lock (GIL) in Python is a mechanism that ensures that only one thread executes Python bytecode at a time. This imposes the following limitations:

• Multithreading in Python does not provide true parallelism for CPU-intensive tasks, as threads acquire control sequentially.
• Threads are useful for I/O-bound tasks, where they can wait for operations to complete, freeing the GIL for other threads.
• For parallel execution of CPU tasks, it is recommended to use multiprocessing (the multiprocessing module), where each process has its own interpreter and GIL.

Thus, the GIL simplifies the implementation of the interpreter and memory management but limits the efficiency of multithreading in computationally heavy tasks.