source code

Source code, sometimes just called “source” or “code”, consists of human-readable computer instructions written by programmers. It’s the original form of a computer program, before it’s translated into a form that a machine can run. In Python, source code is compiled into bytecode, the internal representation that the Python virtual machine executes.

Here’s an example of some source code written in Python:

Python example.py 
def do_twice(func):
    def wrapper_do_twice(*args, **kwargs):
        func(*args, **kwargs)
        func(*args, **kwargs)
    return wrapper_do_twice

@do_twice
def greet(name):
    print(f"Hello, {name}!")

When programmers talk about “reading the source” or “checking the source code,” they mean examining these original, human-readable program files. The source code represents the authoritative version of how a program works and contains all the implementation details of its functionality.

How to Run Your Python Scripts

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How to Run Your Python Scripts and Code

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By Dan Bader • Updated Sept. 23, 2026
Python Glossary Share Feedback