Does GIL limit the execution of threads in Python and how does it affect multithreading?

GIL (Global Interpreter Lock) in Python is a mechanism that restricts the execution of Python bytecode to only one thread at a time within a process. This means that even if you have multiple threads, only one thread executes Python code at any given moment.

This limitation affects multithreading in Python as follows:

• For CPU-intensive tasks, multithreading does not provide a performance boost due to the GIL.
• For tasks that involve a lot of waiting for input/output (e.g., network requests, file operations), threads can switch and work efficiently because the GIL is released during waiting.

If true parallelism for CPU tasks is needed, usually multiprocessing (processes) or alternative Python implementations without GIL (e.g., Jython, IronPython) or libraries that release the GIL during heavy computations in C are used.