GIL (Global Interpreter Lock)

The Global Interpreter Lock (GIL) is a mechanism in CPython, the standard Python implementation, that allows only one thread to execute Python bytecode at a time. Think of it as a gate that prevents multiple threads from running Python code simultaneously, even on multi-core processors. This simplifies memory management and ensures thread safety but limits true parallel execution, particularly for CPU-bound tasks. As a result, multi-threaded Python programs may not experience performance improvements on multi-core systems, though they can still be useful for I/O-bound operations like waiting for data or network responses.