Working with Python Modules and Packages

What You'll Learn

• What are modules and why they're useful
• How to use built-in Python modules like math, random, datetime, etc.
• How to create your own modules
• Understanding and building Python packages
• How to import specific elements (from ... import)
• Directory structure of a real Python package
• Best practices in modular programming

What is a Module?

A module is simply a Python file (.py) containing functions, variables, or classes that you can reuse in other files.

💡 Helps organize your code better and promotes reusability.

Example: Creating and using a Module

math_tools.py

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

main.py

import math_tools
print(math_tools.add(3, 4))  # 7
print(math_tools.multiply(2, 5))  # 10

Built-in Python Modules (No Installation Needed)

Python provides hundreds of pre-built modules.

Example: math and random

import math
import random


print(math.sqrt(16))  # 4.0
print(random.randint(1, 10))  # Random number between 1-10

Importing from Modules

You can import specific function instead of the whole module:

from math import sqrt, pow
print(sqrt(49))  # 7.0
print(pow(2, 3))  # 8.0

You can also alias functions:

import datetime as dt
print(dt.datetime.now())

What is a Python Package?

A package is a directory that contains multiple related modules. It must have an __init__.py file (can by empty) to be recognized as a package.

Example Directory Structure

my_package/
├── __init__.py
├── math_tools.py
├── string_tools.py

Usage in another file:

from my_package import math_tools
print(math_tools.add(5, 6))

🏗 Create Your Own Package (Step-by-Step)

1. Create a folder: my_package/
2. Add a blank file __init__.py
3. Add modules like math_ops.py, file_ops.py
4. Use it in your main program

🛠 Task for You

1. Create a package called utilities
2. Add a module file_utils.py with functions:
   • read_file(filepath)
   • write_file(filepath, content)
3. Import it in a separate script and use the functions.

✔ Best Practices

• Group related functions in a module
• Use packages for project structure
• Use meaningful module and function names
• Avoid circular imports
• Use __init__.py to initialize packages or define what gets imported

Summary