For every bytecode compiled language, the most interesting part of its implementation is its virtual machine (also referred to as the bytecode interpreter) where the bytecode execution takes place. Because this is such a crucial part of the language machinery, its implementation has to be highly performant. Even if you are not a compiler engineer, learning about such internal implementation can give you new performance tricks and insights that you may be able to use in other places of your job. And, if you are a compiler engineer then you should always look around how other languages are implemented to pickup implementation details that you may not be aware of.

In this article, we are going to be discussing the bytecode instruction format of CPython, followed by the implementation of the bytecode evaluation loop of the interpreter where the bytecode execution takes place.