The GIL is quite popular in the Python concurrent programming community. Designed as a lock that will only allow one thread to access and control the Python interpreter at any given time, the GIL in Python is often known as the infamous GIL that prevents multithreaded programs from reaching their fully optimized speed. In this section, we will discuss the concept behind the GIL, and its goals: why it was designed and implemented, and how it affected multithreaded programming in Python.