Is the Modules & Imports lesson free?

Yes. The first 5 lessons on PyRun are free forever — no signup, no card. Modules & Imports runs real Python in your browser via Pyodide.

How long does the Modules & Imports lesson take?

About 6 minutes end-to-end. It's a hands-on lesson — you read a paragraph, edit the code, and run it in the same tab.

Do I need to install Python to try the Modules & Imports lesson?

No install required. PyRun runs real CPython in your browser via Pyodide (Python compiled to WebAssembly). Works on Chrome, Firefox, Safari, and Edge — desktop or mobile.

What level is the Modules & Imports lesson?

Intermediate level. Best after finishing the Beginner track (syntax, control flow, functions, data types).

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Intermediate·6 min·intermediate · modules

Modules & Imports

You’ll be able to

Import from the standard library with import
Import specific names with from ... import ...
Organize your own code into reusable modules
Understand __name__ == "__main__" for scripts vs libraries

Why this matters

Circular imports and misuse of __name__ == "__main__" are the top reasons Django and Flask apps fail to boot. Understanding sys.path, package __init__.py, and relative imports is what makes monorepos and installable packages actually work.

Common pitfalls

Circular imports from top-level from x import y — defer imports into function bodies or restructure modules.
Running python module.py inside a package — relative imports break; use python -m package.module.
Shadowing stdlib names like email.py or types.py in your project — silently breaks unrelated imports.

A module is just a .py file. A package is a folder with an __init__.py.

Four import shapes

import math — use as math.pi
import math as m — alias
from math import pi — pull a name into your namespace
from math import pi as PI — pull and alias

Where Python looks

Built-ins → 2. The current file's directory → 3. Installed site-packages → 4. sys.path

Try it

Try from collections import defaultdict — build one.
Import random and generate 5 random ints between 1 and 100.

Practice

3 graded exercises

Write the code, click Check. We’ll tell you exactly what to fix.

Progress0 / 3

Exercise 1
Use importlib.import_module to load the 'math' module dynamically, then print math.pi rounded to 4 decimal places. Expected output: 3.1416.
Exercise 2
Use the older __import__ builtin to load the 'json' module, then use it to serialize the dict {'a': 1, 'b': 2} to a JSON string and print the result.
Exercise 3
Every imported module is cached in sys.modules. Import os, then verify that 'os' in sys.modules AND that sys.modules['os'] is os. Print True if both are true.

← PreviousContext Managers (`with`)Next →JSON

Modules & Imports

You’ll be able to

Import from the standard library with import
Import specific names with from ... import ...
Organize your own code into reusable modules
Understand __name__ == "__main__" for scripts vs libraries

Why this matters

Common pitfalls

Circular imports from top-level from x import y — defer imports into function bodies or restructure modules.
Running python module.py inside a package — relative imports break; use python -m package.module.
Shadowing stdlib names like email.py or types.py in your project — silently breaks unrelated imports.

A module is just a .py file. A package is a folder with an __init__.py.

Four import shapes

import math — use as math.pi
import math as m — alias
from math import pi — pull a name into your namespace
from math import pi as PI — pull and alias

Where Python looks

Built-ins → 2. The current file's directory → 3. Installed site-packages → 4. sys.path

Try it

Try from collections import defaultdict — build one.
Import random and generate 5 random ints between 1 and 100.

Practice

3 graded exercises

Write the code, click Check. We’ll tell you exactly what to fix.

Progress0 / 3

Exercise 1
Use importlib.import_module to load the 'math' module dynamically, then print math.pi rounded to 4 decimal places. Expected output: 3.1416.
Exercise 2
Use the older __import__ builtin to load the 'json' module, then use it to serialize the dict {'a': 1, 'b': 2} to a JSON string and print the result.
Exercise 3
Every imported module is cached in sys.modules. Import os, then verify that 'os' in sys.modules AND that sys.modules['os'] is os. Print True if both are true.