What is the global interpreter lock (GIL) in CPython?

Question

What is a global interpreter lock and why is it an issue?

A lot of noise has been made around removing the GIL from Python, and I\'d like to understand why that is s

Answer 1

Why Python (CPython and others) uses the GIL

From http://wiki.python.org/moin/GlobalInterpreterLock

In CPython, the global interpreter lock, or GIL, is a mutex that prevents multiple native threads from executing Python bytecodes at once. This lock is necessary mainly because CPython's memory management is not thread-safe.

How to remove it from Python?

Like Lua, maybe Python could start multiple VM, But python doesn't do that, I guess there should be some other reasons.

In Numpy or some other python extended library, sometimes, releasing the GIL to other threads could boost the efficiency of the whole programme.