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Modules & Packages

Apr 1, 2026•5 min read•By Mohammed Vasim

PythonProgrammingTutorialBeginner

Introduction

In this tutorial, you'll learn how to organize your Python code into modules and packages. This allows you to reuse code across files and projects, and use the vast ecosystem of Python libraries.

What You'll Learn

What are modules
Creating and importing modules
The import statement variations
Standard library modules
Installing external packages with pip
Creating packages

What are Modules?

A module is simply a Python file (.py file) containing code you can reuse. Modules help organize code into manageable, reusable pieces.

Creating a Module

Create a file named greetings.py:

python

# greetings.py

def say_hello(name):
    return f"Hello, {name}!"

def say_goodbye(name):
    return f"Goodbye, {name}!"

def say_welcome(name):
    return f"Welcome, {name}!"

# You can also define variables
VERSION = "1.0.0"

Using a Module

In another file:

python

# main.py
import greetings

# Call functions from the module
print(greetings.say_hello("Alice"))
print(greetings.say_goodbye("Bob"))

# Access variables
print(greetings.VERSION)

Import Statements

Different Import Styles

python

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

# Import specific items
from math import sqrt, pi
print(sqrt(16))         # 4.0
print(pi)               # 3.14159...

# Import with alias (aliasing)
import math as m
print(m.sqrt(16))       # 4.0

# Import everything (not recommended)
from math import *
print(sqrt(16))         # 4.0

When to Use What

Import Style	Use When
`import module`	Using multiple items from module
`from module import specific`	Using one or few items
`import module as alias`	Module name is long or conflicts
`from module import *`	Rarely - can cause name conflicts

Standard Library Modules

Python comes with a rich standard library. Here are commonly used ones:

math Module

python

import math

print(math.pi)          # 3.14159...
print(math.e)           # 2.71828...
print(math.sqrt(16))    # 4.0
print(math.floor(3.7))  # 3
print(math.ceil(3.2))   # 4
print(math.sin(math.pi / 2))  # 1.0

random Module

python

import random

print(random.randint(1, 10))    # Random integer 1-10
print(random.random())          # Random float 0-1
print(random.choice([1, 2, 3])) # Random choice from list
print(random.shuffle([1, 2, 3])) # Shuffle list in place

# Generate random password
import string
chars = string.ascii_letters + string.digits
password = ''.join(random.choice(chars) for _ in range(8))
print(password)

datetime Module

python

import datetime

# Current date and time
now = datetime.datetime.now()
print(now)               # 2024-01-15 10:30:45.123456

# Specific date
date = datetime.date(2024, 1, 15)
print(date)              # 2024-01-15

# Date arithmetic
from datetime import timedelta
tomorrow = now + timedelta(days=1)
print(tomorrow)

# Format dates
print(now.strftime("%Y-%m-%d"))  # 2024-01-15
print(now.strftime("%B %d, %Y")) # January 15, 2024

json Module

python

import json

# Convert Python to JSON
data = {"name": "Alice", "age": 25}
json_str = json.dumps(data)
print(json_str)  # {"name": "Alice", "age": 25}

# Convert JSON to Python
parsed = json.loads(json_str)
print(parsed)    # {'name': 'Alice', 'age': 25}

# Write to file
with open("data.json", "w") as f:
    json.dump(data, f, indent=2)

# Read from file
with open("data.json", "r") as f:
    loaded = json.load(f)

os Module

python

import os

# File operations
print(os.getcwd())           # Current directory
os.mkdir("new_folder")      # Create directory
os.rename("old", "new")     # Rename
os.remove("file.txt")       # Delete file
os.path.exists("file.txt")  # Check if exists

# List files
print(os.listdir("."))

Installing External Packages

Python has a vast ecosystem of packages. Install them using pip.

Using pip

bash

# Install a package
pip install requests

# Install specific version
pip install requests==2.28.0

# Upgrade
pip install --upgrade requests

# Uninstall
pip uninstall requests

Popular Packages

Package	Purpose
`requests`	HTTP requests
`numpy`	Numerical computing
`pandas`	Data analysis
`matplotlib`	Data visualization
`flask`	Web framework
`django`	Full web framework

Using Installed Packages

python

import requests

response = requests.get("https://api.github.com")
print(response.status_code)
print(response.json())

Creating Packages

A package is a directory containing multiple modules and a special __init__.py file.

Package Structure

my_package/
├── __init__.py
├── module1.py
├── module2.py
└── subpackage/
    ├── __init__.py
    └── module3.py

init.py

This file makes a directory a package. It can be empty or contain initialization code:

python

# __init__.py
from .module1 import function1
from .module2 import function2

__version__ = "1.0.0"
__all__ = ["function1", "function2"]

Using the Package

python

# Import from package
import my_package
my_package.function1()

# Or import specific
from my_package import function1

# From subpackage
from my_package.subpackage import module3

Practical Example: Calculator Package

Create the Package

calculator/
├── __init__.py
├── operations.py
└── helpers.py

python

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

def subtract(a, b):
    return a - b

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

def divide(a, b):
    if b == 0:
        raise ValueError("Cannot divide by zero")
    return a / b

python

# helpers.py
def validate_numbers(*numbers):
    for num in numbers:
        if not isinstance(num, (int, float)):
            raise TypeError(f"{num} is not a number")
    return True

python

# __init__.py
from .operations import add, subtract, multiply, divide
from .helpers import validate_numbers

__all__ = ["add", "subtract", "multiply", "divide", "validate_numbers"]

Using the Package

python

# main.py
from calculator import add, divide, validate_numbers

try:
    validate_numbers(10, 5)
    result = divide(10, 5)
    print(f"Result: {result}")
except (TypeError, ValueError) as e:
    print(f"Error: {e}")

Summary

In this tutorial, you learned:

✅ What modules are and how to create them
✅ Different import statement styles
✅ Common standard library modules
✅ Installing external packages with pip
✅ Creating your own packages

🧑‍💻 Practice Exercise

Create a package called string_utils with:

A module text.py with functions: reverse_string(), count_vowels(), is_palindrome()
A module format.py with functions: to_title_case(), remove_whitespace()
An __init__.py that exports all functions
A test script that uses the package

Click to see solution

python

# Create folder structure:
# string_utils/
# ├── __init__.py
# ├── text.py
# └── format.py

# text.py
def reverse_string(text):
    return text[::-1]

def count_vowels(text):
    vowels = "aeiouAEIOU"
    return sum(1 for char in text if char in vowels)

def is_palindrome(text):
    cleaned = text.lower().replace(" ", "")
    return cleaned == cleaned[::-1]

# format.py
def to_title_case(text):
    return text.title()

def remove_whitespace(text):
    return "".join(text.split())

# __init__.py
from .text import reverse_string, count_vowels, is_palindrome
from .format import to_title_case, remove_whitespace

__all__ = [
    "reverse_string", "count_vowels", "is_palindrome",
    "to_title_case", "remove_whitespace"
]

# test_string_utils.py
from string_utils import (
    reverse_string, count_vowels, is_palindrome,
    to_title_case, remove_whitespace
)

# Test text functions
print("=== Text Functions ===")
print(f"Reverse: {reverse_string('hello')}")  # olleh
print(f"Vowels in 'hello': {count_vowels('hello')}")  # 2
print(f"Is 'racecar' palindrome: {is_palindrome('racecar')}")  # True
print(f"Is 'hello' palindrome: {is_palindrome('hello')}")  # False

# Test format functions
print("\n=== Format Functions ===")
print(f"Title case: {to_title_case('hello world')}")  # Hello World
print(f"Remove whitespace: {remove_whitespace('hello   world')}")  # helloworld

Output:

=== Text Functions ===
Reverse: olleh
Vowels in 'hello': 2
Is 'racecar' palindrome: True
Is 'hello' palindrome: False

=== Format Functions ===
Title case: Hello World
Remove whitespace: helloworld

What's Next

In the next tutorial, we'll learn about Object-Oriented Programming (OOP) - a paradigm for structuring code using classes and objects.

Introduction to OOP →

Modules & Packages

Introduction

What You'll Learn

What are Modules?

Creating a Module

Using a Module

Import Statements

Different Import Styles

When to Use What

Standard Library Modules

math Module

random Module

datetime Module

json Module

os Module

Installing External Packages

Using pip

Popular Packages

Using Installed Packages

Creating Packages

Package Structure

init.py

Using the Package

Practical Example: Calculator Package

Create the Package

Using the Package

Summary

🧑‍💻 Practice Exercise

What's Next

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