Modules

Overview

A module is a .py file; a package is a directory with __init__.py. The import system lets you reuse code, access the standard library, and install third-party packages with pip.

Syntax / Usage

# Import entire module
import math
math.sqrt(16)  # 4.0

# Import specific names
from datetime import datetime, timedelta

# Alias
import numpy as np

# Relative imports (inside packages)
from .utils import helper
from ..models import User

# __name__ guard for script vs module
if __name__ == "__main__":
    main()

Project layout example:

myapp/
  __init__.py
  models.py
  services/
    __init__.py
    auth.py

Examples

Create a reusable utility module string_utils.py:

def slugify(text: str) -> str:
    return text.lower().strip().replace(" ", "-")

Use it elsewhere:

from string_utils import slugify
slugify("Hello World")  # "hello-world"

Install and use a third-party package:

pip install requests

import requests
response = requests.get("https://api.github.com")
data = response.json()

Common Mistakes

• Circular imports between modules—restructure or use lazy imports
• Using from module import * and polluting the namespace
• Running scripts from the wrong working directory, breaking imports
• Naming your file json.py and shadowing the standard library

See Also

python-functions python-file-io python-classes