From Source Code to Bytecode: The Secret Life of CPython
Is Python a compiled or interpreted language? The answer is both. In this lecture, we take a deep dive into the internal workings of CPython to understand exactly what happens between hitting "run" and seeing your output.
As we peel back the layers of the *CPython runtime**, we explore the two-stage process that makes Python unique. First, we examine the **Compilation Stage**, where your human-readable source code undergoes a series of complex transformations: from tokenisation and parse trees to the **Abstract Syntax Tree (AST)* and Control Flow Graphs (CFG), eventually resulting in platform-independent **bytecode**.
We then transition to the *Interpretation Stage**, where the **Python Virtual Machine (PVM)* takes over. You will learn about the critical role of *code objects* and how they are transformed into **frame objects**—the runtime representation of your code—during evaluation.
*Key topics covered in this lesson:*
*The Hybrid Approach:* Why Python uses both a compiler and an interpreter to balance portability and ease of use.
*Compiler Internals:* How the compiler generates bytecode and bundles it into `.pyc` files.
*Performance & Memory:* A comparative look at how Python’s execution model differs from traditional compiled languages in terms of speed, memory consumption, and error detection.
*Runtime Initialization:* An overview of how the runtime environment initializes *interpreter states* and *thread states* to manage code execution.
*The Frame Object:* Understanding the link between code objects and the PVM's evaluation loop.
Whether you are a student of computer science or a veteran developer, understanding these "under the hood" mechanics will change the way you write and debug Python code.
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