Modules & Packages

Learn how to organize Python code with modules, import variations, packages, and external libraries.

What are Modules?

Modules are Python files containing functions, classes, and variables.
They help organize code into reusable and logical components.
Use the 'import' keyword to access code from other files.
Python provides many built-in modules (math, random, datetime, etc.).

# Using built-in modules
import math

print(math.pi)           # 3.141592653589793
print(math.sqrt(16))     # 4.0
print(math.ceil(4.3))    # 5

import random
print(random.randint(1, 10))  # Random number 1-10

Import Variations

import module → Import entire module
from module import item → Import specific items
import module as alias → Use a shorter name
from module import * → Import everything (not recommended)

# Different import styles
import math
print(math.sqrt(16))

from math import sqrt, pi
print(sqrt(16))
print(pi)

import math as m
print(m.sqrt(16))

# Import with alias
from math import sqrt as square_root
print(square_root(16))

Creating Your Own Modules

Any .py file can be a module.
Define functions, classes, and variables in the file.
Import it in other files using the filename (without .py).

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

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

PI = 3.14159

# File: main.py
import mymath

result = mymath.add(5, 3)
print(result)  # 8
print(mymath.PI)  # 3.14159

# Or import specific items
from mymath import add, PI
print(add(10, 20))  # 30

Packages

Packages are directories containing multiple modules.
Must include an __init__.py file (can be empty).
Organize related modules together for better structure.
Use dot notation to access submodules.

# Directory structure:
# mypackage/
#   __init__.py
#   math_utils.py
#   string_utils.py

# File: mypackage/math_utils.py
def add(a, b):
    return a + b

# File: mypackage/string_utils.py
def uppercase(text):
    return text.upper()

# Using the package
from mypackage import math_utils, string_utils

print(math_utils.add(5, 3))
print(string_utils.uppercase("hello"))

Popular Built-in Modules

math → Mathematical functions
random → Random number generation
datetime → Date and time operations
os → Operating system interface
json → JSON encoding/decoding

# math module
import math
print(math.pow(2, 3))  # 8.0

# random module
import random
print(random.choice(['a', 'b', 'c']))

# datetime module
from datetime import datetime
now = datetime.now()
print(now.strftime("%Y-%m-%d %H:%M:%S"))

# os module
import os
print(os.getcwd())  # Current directory

# json module
import json
data = {"name": "Alice", "age": 25}
json_str = json.dumps(data)
print(json_str)

Installing External Packages

Use pip to install packages from PyPI.
Popular third-party packages: requests, numpy, pandas, flask.
Use requirements.txt to list project dependencies.

# Install a package
# pip install requests

# Use the package
import requests

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

# Create requirements.txt
# requests==2.28.0
# numpy==1.23.0

# Install from requirements.txt
# pip install -r requirements.txt

Real-life Use Case

Modules and packages allow for clean project structure.
External libraries (via pip) extend Python’s power.
Example: Using requests and json modules to fetch and process API data.

import requests, json

# Fetch GitHub API data
response = requests.get("https://api.github.com/users/octocat")
if response.status_code == 200:
    data = response.json()
    print(json.dumps(data, indent=2))