APY-02 Modules

Introduction

• A module is a file containing Python code that defines functions, classes, or variables.
• Modules are the building blocks of your Python projects; they allow you to organize, reuse, and maintain your code with ease.
• Why use module?
  • Reusability of code.
  • Organization of code into logical files.
  • Namespace separation.

Importing a Module in Python

• Importing a module using import

import math
print(math.sqrt(25))

• Importing specific functions using from import

from math import sqrt
print(sqrt(25))

• Import all functions/variables from a module

from math import *
print(sqrt(25))

Module Search Path

• Where does Python look for modules?
  • Current directory
  • Standard libraries directory
  • Environment variable PYTHONPATH
• To check search paths:

import sys
print(sys.path)

Package

• A package is a collection of modules in a directory hierarchy. It contains an __init__.py file to indicate that the directory is a Python package.
• Structure of Package:

my_package/
	__init__.py
	module1.py
	module2.py

Creating a User-defined Package

1. Create a directory with an __init__.py file.
2. Add modules inside this directory.
3. Import the package using import package_name.

import my_package.module1
my_package.module1.function_name()

Random Module

• Used to generate random numbers and perform random actions.
• Common Functions:
  • random.random() — generates a random float between 0 and 1.
  • random.randint(a, b) — generates a random integer between a and b.

import random
print(random.randint(1, 10))

Date & Time Module

• datetime is the most common module for handling dates and times

import datetime
print(datetime.datetime.now())

Math Module

• Provides mathematical functions like trigonometric functions, square root, etc.

import math
print(math.pi)

Built-in Exceptions

• Common Built-in Exceptions:
  • TypeError
  • ValueError
  • FileNotFoundError

try:
	x = int("abc")
except ValueError:
	print("Invalid value")

User-defined Exceptions

• To create an user-defined exceptions define a new exception class that inherits from Exception.

class MyCustomError(Exception):
	pass
raise My Custom Error("Something went wrong")

Raising Exceptions

• Raise an exception manually when a certain condition is met.

if age < 18:
	raise ValueError("Age must be 18 or older")

Try, Except, Finally Block

• Syntax

try:
	# Code that may raise an exception
except Exception Type:
	# Code that runs if exception is caught
finally:
	# Code that runs regardless of exception

try:
	x = 10 / 0
except ZeroDivisionError:
	print("Cannot divide by zero")
finally:
	print("Execution completed")

Introduction to Files and Its Types

• There are 2 types of files in python:
  • Text Files: Human-readable files (.txt, .csv, .log).
  • Binary Files: Files that contain non-text data (.png, .jpg, .exe).

Working with Binary Files

• Opening a Binary Files

with open('image.png', 'rb') as file:
	data = file.read()

• Writing to a Binary File:

with open('output.bin', 'wb') as file:
	file.write(data)

Working with Text Files

• Reading from a Text File

with open('example.txt', 'r') as file:
	content = file.read()
	print(content)

• Writing to a Text File

with open('example.txt', 'w') as file:
	file.write("Hello, World!")

Reading & Writing Files

• Modes for Opening Files
  • 'r' – read (default mode)
  • 'w' – write (creates a new file or overwrites an existing one)
  • 'a' – append
  • 'b' – binary mode

with open('data.txt', 'a') as file:
	file.write("Adding new data\n")

Questions

1. What are modules in Python? Explain the process of importing a module using examples. (3)
2. Write a Python program to demonstrate the use of the random module to generate random numbers (4)
3. Explain how to handle exceptions in Python using the try, except, and finally blocks. Provide examples. (5)
4. Write a Python program to raise and handle a user-defined exception. (5)
5. Discuss the module search path in Python. How can we modify it? (3)
6. Explain the difference between binary and text files. Write a program to read and write a text file. (4)
7. What is the role of the math module in Python? Demonstrate its use with examples of common functions. (4)
8. Write a Python program to create and use a user-defined package containing multiple modules. (5)
9. Discuss the concept of built-in exceptions in Python. Provide examples of at least three such exceptions. (3)
10. Explain the difference between from module import and import module. Give code examples. (3)

Resources

1. W3School Python Modules
2. W3School File Handling
3. Random Module | Python Docs
4. Random Module | W3School
5. DateTime Module | Python Docs
6. DateTime Module | W3School
7. Math Module | Python Docs
8. Math Module | W3School
9. Exceptions | Python Docs
10. Exceptions | W3School