Modules & Imports

Overview

Organize your code by dividing it across multiple files, and import them as modules.

Learning Objectives

• Import code using import, from, and as.
• Prevent circular import dependency errors.
• Use name to create script entry points.

Concept Explanation

Every Python file is a module. Importing a module runs its code and binds its namespace. Use if __name__ == '__main__' to write code that only executes when the script is run directly, and not when it is imported into another file.

Code Examples

Example 1 — Basics

This example introduces the fundamental syntax and concepts.

import math
print(math.sqrt(16))

Example 2 — Everyday Usage

This example demonstrates a realistic scenario handling business parameters.

from datetime import datetime as dt
print(f'Current time is: {dt.now()}')

Example 3 — Advanced Example

This example shows clean, production-grade code structure following senior development standards.

def run_operations():
    print('Running standalone calculations.')

if __name__ == '__main__':
    # Executes only if run directly
    run_operations()

Visual Flow

The following execution flow represents the step-by-step evaluation inside the interpreter:

Trigger Import → Search sys.modules → Load code → Execute module statements → Bind namespace

Common Mistakes

Review these common pitfalls when working with this topic:

• Creating circular imports where module A imports B, and B imports A.
• Using wildcard imports (from math import *) that pollute namespaces.
• Naming local scripts the same as standard modules (e.g. naming your file 'math.py').
• Forgetting script check guards inside files that are meant to be imported as libraries.

Best Practices

Enforce these Pythonic best practices in your codebase:

from math import * # Pollutes namespace

import math # Clean namespace references

Quick Revision

Use these key summaries for last-minute revision:

• Modules are standard .py files.
• import statement exposes code tools.
• Wildcard imports make code harder to debug.
• name checks if a file is the main script.
• Python caches imports inside sys.modules.
• Avoid shadowing standard library names.