Modules and Packages

Introduction

Modules are Python files that contain functions, classes, and variables. Packages are directories containing multiple modules.

Importing Modules

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

# Import specific items
from math import sqrt, pi
print(sqrt(16) * pi)

# Alias imports
import numpy as np
import pandas as pd
from datetime import datetime as dt

Creating Modules

# my_module.py
def add(a, b):
    return a + b

class Calculator:
    def multiply(self, a, b):
        return a * b

# main.py
from my_module import add, Calculator

Package Structure

mypackage/
    __init__.py
    module1.py
    module2.py
    subpackage/
        __init__.py
        module3.py

Standard Library Modules

import os        # Operating system
import sys       # System parameters
import json      # JSON handling
import datetime  # Date and time
import random    # Random numbers
import re        # Regular expressions

Practice Problems

1. Create a utility module with common functions
2. Build a package with multiple related modules
3. Use init.py to control imports
4. Create and use a custom package
5. Organize a project into modules