Python Compilation Process Explained Step-by-Step for Beginners

In my earlier article (https://hashnode.com/post/cmdxai7na000502le26b681e2), I talked about how programming languages act as translators between humans and machines — converting binary into human-readable form and vice versa. This enables communication between humans and computers.

💡 Terminology Alert!

High-Level Language: Language that is understandable by humans (e.g., Python, Java)
Low-Level Language: Language understandable by machines — usually binary (0’s and 1’s)

🤔 But How Does This Translation Happen?

This process of converting high-level language to low-level (machine) language is called compilation.

Now let’s understand how Python handles this process step by step.

🔁 Python Compilation Stages (5-Step Process)

Source Code
Python Interpreter
Bytecode
Python Virtual Machine (PVM)
Output

🔹 1. Source Code

This is the code written by a developer — it’s the .py file you create.

Just like we save images as .jpg or .png, Python source code must be saved with the .py extension.

Example:

print("Hello, Python!!")

Save this as hello.py.

🔸 2. Python Interpreter

The interpreter is what starts the process.

It reads the source code
Compiles it to an intermediate format called bytecode, which is not human-readable but still not binary.
Then passes it on to the next stage

This is what allows your Python code to be run and understood by your system.

🔹 3. Bytecode (.pyc)

Once compiled, Python generates a bytecode file automatically.

It will be saved as a .pyc file
Stored inside a folder called __pycache__
Example: __pycache__/hello.cpython-311.pyc

This file contains a translated version of your original code — not in binary, but in a form Python can process faster.

🧠 Why it's useful:
If you run the same program multiple times, Python won’t compile it again — it just reuses the .pyc file, saving time.

🔸 4. Python Virtual Machine (PVM)

The Python Virtual Machine now steps in.

It reads and executes the bytecode
Executes it line by line
This is where all the actual actions (like printing, calculations, etc.) happen

You can think of the PVM as Python’s runtime engine.

🔹 5. Output

After all the behind-the-scenes work is done, Python finally shows you the output on your screen.

In our case:

Hello, Python!!

🧪 Let’s See This in Action

print("Hello, Python!!")

Save this code as hello.py
Run it using:
```
 python hello.py
```
Python creates a .pyc file like:
__pycache__/hello.cpython-311.pyc
The PVM executes the bytecode
Output appears:
```
 Hello, Python!!
```

🔁 In Short

Your code (.py)

↓

Compiled to Bytecode (.pyc)

↓

Run by PVM

↓

Output on Screen

🧠 Final Thoughts

Knowing what happens behind the scenes gives you more control and confidence as a Python programmer. You’re not just writing code — you understand how it runs.

In the next article, we’ll take our first step into actual Python coding with variables and data.

Thanks for reading! 😊

How Python Runs Your Code: Compilation Process Explained (With First Program)