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13. Understanding Python Scripts vs Modules

1. Introduction​

In Python, you will often hear the terms script and module.
They are both Python files, but they serve slightly different purposes.
Understanding this difference is important when you start organizing larger projects.

2. What is a Script?​

  • A script is a Python file meant to be run directly.
  • It usually performs a specific task when executed.
  • Example: hello.py
print("Hello, this is a script!")

Run it from the command line:

python3 hello.py

Output:

Hello, this is a script!

3. What is a Module?​

  • A module is a Python file that provides functions, classes, or variables for other Python files to use.
  • Instead of running it directly, you import it.

Example: mymath.py

def add(a, b):
    return a + b

Use it in another file test.py:

import mymath
print(mymath.add(2, 3))

Output:

5

4. Using __name__ == "__main__"​

Sometimes a file can act as both a script and a module.
This is done using the special variable __name__.

Example: dual.py

def greet(name):
    print("Hello,", name)

if __name__ == "__main__":
    # This runs only if the file is executed directly
    greet("World")
  • Run directly:
python3 dual.py

Output:

Hello, World
  • Import as module:
import dual
dual.greet("Alice")

Output:

Hello, Alice

5. Built-in Modules​

Python comes with many built-in modules.
Example:

import math
print(math.sqrt(16))

Output:

4.0

6. Creating Your Own Modules​

  • Any .py file can be a module.
  • Keep related functions together in one file.
  • Example: geometry.py for shapes, strings.py for text utilities.
  • You can import them into any script in the same directory.

7. Why the Distinction Matters​

  • Scripts → run tasks.
  • Modules → provide reusable code.
  • Understanding this distinction helps organize code into projects with many files.

8. Next Steps​

✅ You now understand the difference between Python scripts and modules.
In the next chapter, we’ll cover debugging basics to help you fix errors in your programs.