Lesson 11: Python File Handling and I/O | Coding Class Series

Introduction

Welcome to Lesson 11!
In this lesson, we will learn how to work with files in Python, including reading, writing, and appending data. File handling is crucial for data storage, logs, and application input/output.

1. Opening a File

Use the built-in open() function to open a file:

# Open a file in read mode
file = open("example.txt", "r")
print(file.read())
file.close()

Modes of File:

• "r" → Read (default)
• "w" → Write (creates or overwrites)
• "a" → Append (adds data at end)
• "rb" / "wb" → Read/Write in binary mode

2. Reading Files

• Read all content at once:

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

• Read line by line:

with open("example.txt", "r") as file:
    for line in file:
        print(line.strip())

• Read specific characters:

with open("example.txt", "r") as file:
    print(file.read(10))  # Reads first 10 characters

3. Writing to Files

• Write new content (overwrites existing file):

with open("example.txt", "w") as file:
    file.write("Hello, Python File Handling!")

• Append content to existing file:

with open("example.txt", "a") as file:
    file.write("\nThis is appended text.")

4. Using with Statement

The with statement automatically closes the file, even if an error occurs:

with open("example.txt", "r") as file:
    data = file.read()
    print(data)
# File is automatically closed here

5. Handling CSV Files

Python provides csv module to handle CSV files:

import csv

# Writing to a CSV
with open("data.csv", "w", newline="") as file:
    writer = csv.writer(file)
    writer.writerow(["Name", "Age", "City"])
    writer.writerow(["Alice", 25, "New York"])
    writer.writerow(["Bob", 30, "London"])

# Reading from a CSV
with open("data.csv", "r") as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

6. Practice Exercises

1. Create a text file and write your favorite poem into it.
2. Read the text file line by line and print lines containing the word "Python".
3. Create a CSV file for your friends' names, age, and city, and read it using Python.
4. Append new data to the existing CSV file and verify it.

Lesson 10: Python Modules and Libraries | Coding Class Series

Introduction

Welcome to Lesson 10!
In this lesson, we will learn about Python Modules and Libraries. These are essential for reusing code, extending Python functionality, and making development faster and easier.

1. What is a Module?

A module is a Python file (.py) that contains functions, classes, and variables which you can use in other Python programs.

Example:

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

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

You can use this module in another file using import:

import math_module

print(math_module.add(10, 5))       # Output: 15
print(math_module.subtract(10, 5))  # Output: 5

2. Built-in Python Modules

Python has many built-in modules ready to use:

• math → Mathematical functions
• random → Random number generation
• datetime → Date and time functions
• os → Operating system functionalities

Example:

import math
import random
from datetime import datetime

print(math.sqrt(25))          # Output: 5.0
print(random.randint(1, 10))  # Output: Random number between 1 and 10
print(datetime.now())         # Output: Current date and time

3. Installing Third-Party Libraries

Python libraries like requests, numpy, pandas, etc., can be installed using pip:

pip install requests
pip install numpy

Example using requests:

import requests

response = requests.get("https://api.github.com")
print(response.status_code)  # Output: 200

4. Creating Your Own Library

You can combine multiple modules into a package (your own library):

my_library/
│
├── __init__.py
├── math_utils.py
└── string_utils.py

Usage:

from my_library.math_utils import add
print(add(5, 10))  # Output: 15

5. Practice Exercises

1. Create a module calc.py with functions multiply and divide. Import it in another file and test it.
2. Use the random module to generate a random list of numbers and find the max and min.
3. Install requests and fetch data from any public API.
4. Create a simple package with 2 modules and use it in a program.

Lesson 9: Object-Oriented Programming (OOP) in Python | Coding Class Series

Introduction

Welcome to Lesson 9!
In this lesson, we will learn Object-Oriented Programming (OOP) in Python, which is a powerful way to structure code using classes and objects. OOP helps you write reusable, organized, and maintainable programs.

1. What is OOP?

Object-Oriented Programming (OOP) is a programming paradigm that uses objects to represent real-world entities.
Key concepts:

• Class → Blueprint of an object
• Object → Instance of a class
• Attributes → Properties of an object
• Methods → Functions of an object

2. Creating a Class and Object

Example:

class Person:
    def __init__(self, name, age):
        self.name = name  # Attribute
        self.age = age    # Attribute

    def greet(self):
        print(f"Hello, my name is {self.name} and I am {self.age} years old.")

# Creating an object
person1 = Person("Alice", 20)
person1.greet()  # Output: Hello, my name is Alice and I am 20 years old.

Explanation:

• __init__ → Constructor method, runs automatically when object is created
• self → Refers to the current object

3. Inheritance

Inheritance allows a class to reuse code from another class.

class Student(Person):
    def __init__(self, name, age, student_id):
        super().__init__(name, age)
        self.student_id = student_id

    def show_id(self):
        print(f"My student ID is {self.student_id}")

student1 = Student("Bob", 18, "S123")
student1.greet()      # Inherited method
student1.show_id()    # Own method

Benefits:

• Reuse existing code
• Create hierarchical relationships
• Simplify complex programs

4. Encapsulation

Encapsulation is the concept of hiding private details of an object.

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance  # Private attribute

    def deposit(self, amount):
        self.__balance += amount

    def get_balance(self):
        return self.__balance

account = BankAccount(1000)
account.deposit(500)
print(account.get_balance())  # Output: 1500

Note: Prefix __ to make an attribute private.

5. Polymorphism

Polymorphism allows methods with the same name to behave differently depending on the object.

class Dog:
    def speak(self):
        print("Woof!")

class Cat:
    def speak(self):
        print("Meow!")

animals = [Dog(), Cat()]
for animal in animals:
    animal.speak()
# Output: Woof! Meow!

6. Practice Exercises

1. Create a class Car with attributes brand and year, and method display_info().
2. Create a subclass ElectricCar that inherits from Car and adds battery_capacity.
3. Create objects of both classes and call their methods.
4. Make a class Account with private balance and methods deposit and withdraw.

Lesson 8: File Handling and Exception Handling | Coding Class Series

Introduction

Welcome to Lesson 8!
In this lesson, we will learn about file handling in Python and how to manage errors using exception handling. These skills are essential to make your programs robust and data-driven.

1. File Handling

File handling allows your program to read from and write to files on your computer.

Opening a file:

file = open("example.txt", "w")  # 'w' mode to write
file.write("Hello, Python!")
file.close()

Reading a file:

file = open("example.txt", "r")  # 'r' mode to read
content = file.read()
print(content)  # Output: Hello, Python!
file.close()

Using with statement (recommended):

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

File Modes:

• r → read
• w → write (overwrite)
• a → append
• rb / wb → read/write binary

2. Exception Handling

Exceptions occur when your program runs into an error.
Python allows you to handle exceptions gracefully using try, except, finally blocks.

Example:

try:
    num = int(input("Enter a number: "))
    print(10 / num)
except ZeroDivisionError:
    print("Cannot divide by zero!")
except ValueError:
    print("Invalid input! Enter a number.")
finally:
    print("Execution completed.")

Key Points:

• try: Block where error might occur
• except: Handles specific errors
• finally: Executes always, even if an error occurs

3. Combining File Handling and Exceptions

You can handle file errors with exception handling:

try:
    with open("data.txt", "r") as file:
        print(file.read())
except FileNotFoundError:
    print("File not found. Please check the file name!")

Benefits:

• Prevents program crashes
• Provides useful error messages
• Improves program reliability

4. Practice Exercises

1. Create a file notes.txt and write 5 lines of text in it.
2. Read the file and count the number of words.
3. Write a program that asks the user for a filename and prints its content. Handle errors if the file does not exist.
4. Create a program that divides two numbers and handles division by zero and invalid input using exception handling.

Lesson 7: Functions and Modules | Coding Class Series

Introduction

Welcome to Lesson 7!
In this lesson, we will learn about functions and modules in Python. Functions allow you to reuse code, while modules help you organize your programs efficiently.

1. Functions

A function is a block of code that performs a specific task and can be reused multiple times.

Syntax:

def greet(name):
    print(f"Hello, {name}!")

greet("Alice")  # Output: Hello, Alice!

Key Points:

• Functions start with the def keyword.
• Arguments can be passed inside parentheses.
• return keyword is used to give back a result.

Example with Return:

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

result = add(5, 3)
print(result)  # Output: 8

2. Modules

A module is a file containing Python definitions and functions.
You can import modules to use their functions in your program.

Importing a module:

import math

print(math.sqrt(16))  # Output: 4.0

From module import specific function:

from math import pow

print(pow(2, 3))  # Output: 8.0

Creating your own module:

1. Create a file my_module.py:

def welcome():
    print("Welcome to my module!")

2. Import in another file:

import my_module

my_module.welcome()  # Output: Welcome to my module!

3. Advantages of Functions and Modules

• Reusability: Write once, use multiple times.
• Organization: Keeps code clean and structured.
• Efficiency: Saves time and reduces errors.
• Scalability: Easier to maintain and expand large programs.

Practice Exercises

1. Create a function multiply(a, b) that returns the product of two numbers.
2. Write a function that takes a list of numbers and returns the largest number.
3. Create a module math_utils.py with a function square(n) that returns the square of a number. Import it and test.
4. Use the random module to generate 5 random numbers between 1 and 50.

Lesson 6: Lists, Tuples, and Dictionaries | Coding Class Series

Introduction

Welcome to Lesson 6!
In this lesson, we will learn about Python data structures: lists, tuples, and dictionaries. These structures help you store and organize multiple values efficiently.

1. Lists

A list is an ordered and mutable collection of items.
You can add, remove, or change elements in a list.

Syntax:

fruits = ["apple", "banana", "cherry"]
print(fruits[0])  # Access first item

Common List Methods:

fruits.append("orange")     # Add item
fruits.remove("banana")     # Remove item
fruits.sort()               # Sort items
print(fruits)

2. Tuples

A tuple is ordered but immutable.
Once created, you cannot change its elements.

Syntax:

coordinates = (10, 20)
print(coordinates[0])

Why use tuples?

• They are faster than lists
• Useful for data that should not change, like coordinates or constants.

3. Dictionaries

A dictionary stores key-value pairs.
You can access values using keys, not indexes.

Syntax:

student = {"name": "Alice", "age": 16, "grade": "A"}
print(student["name"])  # Output: Alice

Common Dictionary Methods:

student["age"] = 17        # Update value
student["city"] = "Delhi"  # Add new key-value pair
print(student.keys())      # Show all keys
print(student.values())    # Show all values

Practice Exercises

1. Create a list of your 5 favorite movies. Print them in alphabetical order.
2. Create a tuple of your 3 favorite colors and try to change one color (observe what happens).
3. Create a dictionary for a book: title, author, year. Update the year and print all keys and values.
4. Use a list of dictionaries to store 3 students’ information and print each student’s name and grade.

Lesson 5: Conditional Statements and Loops | Coding Class Series

Introduction

Welcome to Lesson 5!
In this lesson, we will learn how to make decisions in your code using conditional statements (if, elif, else) and how to repeat tasks efficiently using loops (for and while).

Conditional Statements

Conditional statements let your program execute code based on certain conditions.

Syntax in Python:

age = 18

if age >= 18:
    print("You are an adult.")
else:
    print("You are not an adult.")

Explanation:

• if age >= 18: → checks if the condition is True
• else: → executes if the condition is False

Example with multiple conditions:

marks = 75

if marks >= 90:
    print("Grade: A")
elif marks >= 75:
    print("Grade: B")
else:
    print("Grade: C")

Loops

Loops allow repeating code multiple times without rewriting it.

For Loop

Used to iterate over sequences like lists, strings, or ranges.

for i in range(1, 6):
    print(f"Number: {i}")

Output:

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

While Loop

Executes code as long as a condition is True.

count = 1
while count <= 5:
    print(f"Count: {count}")
    count += 1

Output:

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

Practice Exercises

1. Write a program to check if a number is positive, negative, or zero using if-elif-else.
2. Print all even numbers from 1 to 50 using a for loop.
3. Use a while loop to print the first 10 Fibonacci numbers.
4. Write a program to count the number of vowels in a string using a loop.

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