Python Casting

In Python, casting means converting a variable from one data type to another. Python is dynamically typed, which means the type is decided automatically when you assign a value. However, you may want to convert data into a specific type for calculations or formatting.

Why Use Casting?

• To ensure values are in the right format for calculations.
• To avoid errors when working with different data types.
• To convert user input (which is always a string) into numbers.

Types of Casting in Python

int() — Convert to Integer

Converts a number or a numeric string into an integer. Decimals are truncated, not rounded.

x = int(1)       # 1
y = int(2.9)     # 2
z = int("10")    # 10
print(x, y, z)   # Output: 1 2 10

float() — Convert to Floating Point

Converts a number or numeric string into a floating-point (decimal) number.

a = float(1)       # 1.0
b = float(2.5)     # 2.5
c = float("3.14")  # 3.14
print(a, b, c)     # Output: 1.0 2.5 3.14

str() — Convert to String

Converts numbers and other values into text.

p = str(10)      # "10"
q = str(3.14)    # "3.14"
r = str(True)    # "True"
print(p, q, r)   # Output: 10 3.14 True

Practical Examples

# Example 1: Math with input
age = input("Enter your age: ")  # input is string
age_num = int(age)
print(age_num + 5)

# Example 2: String concatenation
price = 99
print("The price is " + str(price))

Key Points

• int() removes the decimal part (does not round).
• float() can handle decimal values and numeric strings.
• str() is used when combining numbers with text.
• Invalid conversions (e.g. int("abc")) cause ValueError.

Practice Questions

1. What is the difference between int(2.9) and round(2.9)?
2. Write a program that asks for age and prints: In 5 years, you will be X years old.
3. Convert the string "15.75" into both float and int. What happens?
4. Why does int("3.5") raise an error while float("3.5") works?
5. Write a program that takes a float price, casts it to int, and prints both values.

Python Strings

In Python, a string is a sequence of characters enclosed in either single quotes (' ') or double quotes (" "). Strings are one of the most commonly used data types in Python.

Creating Strings

# Single or double quotes
a = "Hello"
b = 'World'
print(a, b)   # Output: Hello World

Multiline Strings

Use triple quotes (''' or """) for strings that span multiple lines.

text = """This is
a multiline
string."""
print(text)

Accessing Characters

Strings are arrays of characters, and indexing starts at 0.

word = "Python"
print(word[0])   # P
print(word[5])   # n

Slicing Strings

You can extract a portion of a string using slicing.

word = "Python"
print(word[0:4])   # Pyth
print(word[2:])    # thon
print(word[:3])    # Pyt

String Length

txt = "Hello World"
print(len(txt))   # 11

String Methods

Python has many built-in string methods:

• upper() → Converts to uppercase
• lower() → Converts to lowercase
• strip() → Removes whitespace
• replace() → Replaces a substring
• split() → Splits string into a list

txt = " Hello World "
print(txt.upper())      # HELLO WORLD
print(txt.lower())      # hello world
print(txt.strip())      # "Hello World"
print(txt.replace("World", "Python"))  # Hello Python
print(txt.split())      # ['Hello', 'World']

String Concatenation

a = "Hello"
b = "World"
print(a + " " + b)   # Hello World

String Formatting

You can insert variables into strings using f-strings or format().

name = "Alice"
age = 25
print(f"My name is {name}, and I am {age} years old.")
print("My name is {}, and I am {} years old.".format(name, age))

Escape Characters

Use the backslash (\) to escape special characters.

txt = "We are \"Python\" developers"
print(txt)   # We are "Python" developers

Practice Questions

1. Create a multiline string about your favorite hobby and print it.
2. Write a program to display the first and last character of the string "Programming".
3. Take a user’s full name as input and print it in uppercase.
4. Replace the word "World" with "Python" in "Hello World".
5. Format a string that says: "My favorite number is X", where X is an integer variable.

Python Booleans

In Python, a boolean represents one of two values: True or False. Booleans are often used in conditional statements, loops, and logical operations.

Boolean Values

print(True)   # True
print(False)  # False
print(type(True))   # <class 'bool'>

Boolean Expressions

A boolean expression evaluates to either True or False.

x = 10
y = 5

print(x > y)   # True
print(x == y)  # False
print(x < y)   # False

Using Booleans in If Statements

is_raining = True

if is_raining:
    print("Take an umbrella")
else:
    print("Enjoy the sunshine")

bool() Function

The bool() function can convert values to a boolean:

print(bool(1))       # True
print(bool(0))       # False
print(bool("Hello")) # True
print(bool(""))      # False

Falsy Values in Python

The following are considered False in Python:

• 0
• "" (empty string)
• [] (empty list)
• () (empty tuple)
• {} (empty dictionary)
• None
• False

Booleans in Logical Operations

a = True
b = False

print(a and b)   # False
print(a or b)    # True
print(not a)     # False

Practice Questions

1. Write a boolean expression to check if a number is greater than 100.
2. Use an if statement to check if a string is empty or not.
3. Convert the values 0, "Python", and [] into booleans using bool().
4. What will be the result of 5 > 2 and 3 < 1?
5. Create a program that checks if a person’s age is 18 or older and prints "Adult" or "Minor".

Python Operators

In Python, operators are special symbols that perform operations on variables and values. Operators are the building blocks of programming because they help us perform calculations, compare values, and make decisions.

Types of Python Operators

• Arithmetic Operators
• Comparison (Relational) Operators
• Assignment Operators
• Logical Operators
• Identity Operators
• Membership Operators
• Bitwise Operators

1. Arithmetic Operators

Used for mathematical calculations:

x = 10
y = 3

print(x + y)  # Addition → 13
print(x - y)  # Subtraction → 7
print(x * y)  # Multiplication → 30
print(x / y)  # Division → 3.33
print(x % y)  # Modulus → 1 (remainder)
print(x ** y) # Exponentiation → 1000
print(x // y) # Floor division → 3

2. Comparison Operators

Used to compare two values. Returns True or False.

a = 5
b = 10

print(a == b)  # False
print(a != b)  # True
print(a > b)   # False
print(a < b)   # True
print(a >= b)  # False
print(a <= b)  # True

3. Assignment Operators

Used to assign values to variables.

x = 5
x += 3   # x = x + 3 → 8
x -= 2   # x = x - 2 → 6
x *= 4   # x = x * 4 → 24
x /= 6   # x = x / 6 → 4.0
x %= 3   # x = x % 3 → 1

4. Logical Operators

Used to combine conditional statements.

a = True
b = False

print(a and b) # False
print(a or b)  # True
print(not a)   # False

5. Identity Operators

Check if two objects are the same in memory.

x = ["apple", "banana"]
y = ["apple", "banana"]
z = x

print(x is z)     # True (same object)
print(x is y)     # False (different objects with same values)
print(x == y)     # True (values are equal)

6. Membership Operators

Check if a value is present in a sequence.

fruits = ["apple", "banana", "cherry"]

print("apple" in fruits)   # True
print("mango" not in fruits) # True

7. Bitwise Operators

Used to compare binary numbers.

a = 6   # 110 in binary
b = 3   # 011 in binary

print(a & b)  # AND → 2 (010)
print(a | b)  # OR  → 7 (111)
print(a ^ b)  # XOR → 5 (101)
print(~a)     # NOT → -7
print(a << 1) # Left shift → 12
print(a >> 1) # Right shift → 3

Practice Questions

1. Write a program to calculate the square of a number using the exponent operator (**).
2. Check if two numbers are equal or not using comparison operators.
3. Create a program that uses logical operators to check if a number is between 10 and 50.
4. Use membership operators to check if "python" exists in the list ["java", "python", "c++"].
5. Write a small code that uses bitwise operators to perform AND, OR, and XOR on 5 and 7.

Python Lambda

In Python, a lambda function is a small, anonymous function. It can take any number of arguments but can only have one expression. Lambda functions are often used when you need a function for a short period of time.

Syntax

lambda arguments : expression

- lambda keyword is used to define the function.
- arguments are the inputs (like normal function parameters).
- expression is evaluated and returned. (It is always a single line.)

Example: Simple Lambda

add = lambda a, b: a + b
print(add(5, 3))  # Output: 8

Why Use Lambda Functions?

• When you need a simple function for a short time.
• To make code shorter and cleaner.
• Useful with functions like map(), filter(), and sorted().

Lambda with Single Argument

square = lambda x: x * x
print(square(4))  # Output: 16

Lambda with Multiple Arguments

multiply = lambda a, b, c: a * b * c
print(multiply(2, 3, 4))  # Output: 24

Using Lambda with map()

map() applies a function to each element in a list.

nums = [1, 2, 3, 4, 5]
squares = list(map(lambda x: x**2, nums))
print(squares)  # [1, 4, 9, 16, 25]

Using Lambda with filter()

filter() selects items based on a condition.

nums = [10, 15, 20, 25, 30]
even = list(filter(lambda x: x % 2 == 0, nums))
print(even)  # [10, 20, 30]

Using Lambda with sorted()

sorted() can use a lambda to customize sorting.

students = [("Alice", 25), ("Bob", 20), ("Charlie", 23)]
# Sort by age
sorted_students = sorted(students, key=lambda x: x[1])
print(sorted_students)  
# Output: [('Bob', 20), ('Charlie', 23), ('Alice', 25)]

Practice Questions

1. Write a lambda function to add 15 to a number.
2. Use a lambda function to check if a number is even.
3. With map() and lambda, convert a list of temperatures from Celsius to Fahrenheit.
4. Use filter() and lambda to find numbers divisible by 5 in a list.
5. Sort a list of tuples [("apple", 50), ("banana", 20), ("cherry", 30)] by price using a lambda.

Python Arrays

In Python, an array is a collection of elements of the same type. Arrays are useful when you need to store multiple values in a single variable and perform operations on them. Unlike lists, arrays are more memory-efficient and require importing the array module.

Creating an Array

To use arrays, you need to import the array module:

import array as arr

numbers = arr.array('i', [1, 2, 3, 4, 5])
print(numbers)  # array('i', [1, 2, 3, 4, 5])

- The first argument 'i' specifies the **type code** (here, integer). - Common type codes: 'i' → int, 'f' → float, 'u' → Unicode character.

Accessing Array Elements

print(numbers[0])   # 1
print(numbers[3])   # 4

Modifying Array Elements

numbers[1] = 10
print(numbers)   # array('i', [1, 10, 3, 4, 5])

Array Methods

• append(x) → Add an element at the end
• insert(i, x) → Insert element at position i
• remove(x) → Remove first occurrence of x
• pop() → Remove last element
• index(x) → Returns first index of x
• reverse() → Reverse the array

numbers.append(6)
numbers.insert(2, 7)
numbers.remove(3)
numbers.pop()
print(numbers)   # array('i', [1, 10, 7, 4])

Iterating Through an Array

for num in numbers:
    print(num)
# Output:
# 1
# 10
# 7
# 4

Practice Questions

1. Create an array of integers from 1 to 10 and print it.
2. Add the number 15 at the end of the array.
3. Insert the number 20 at the 3rd position in the array.
4. Remove the first occurrence of 7 from the array.
5. Reverse the array and print all elements using a loop.

Python Classes / Objects

Python is an object-oriented programming (OOP) language. In Python, a class is a blueprint for creating objects, and an object is an instance of a class. Classes allow you to group data (attributes) and functions (methods) together.

Creating a Class

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 Objects

p1 = Person("Alice", 25)
p2 = Person("Bob", 30)

p1.greet()  # Hello, my name is Alice and I am 25 years old.
p2.greet()  # Hello, my name is Bob and I am 30 years old.

Attributes and Methods

- Attributes are variables that belong to an object.
- Methods are functions that belong to an object.

print(p1.name)  # Alice
print(p2.age)   # 30

The __init__ Method

The __init__ method is called automatically when an object is created. It is used to initialize the attributes of the object.

Practice Questions

1. Create a class Car with attributes brand and year, and a method that prints these details.
2. Create two objects of the Car class and display their details.
3. Add a method to the Person class that calculates the year of birth using the age attribute.
4. Modify an attribute of an object after it is created and display the updated value.
5. Create a class Rectangle with width and height, and a method to calculate the area.

Python Inheritance

In Python, inheritance is a feature of object-oriented programming that allows a class (child class) to inherit attributes and methods from another class (parent class). Inheritance helps in code reusability and makes programs easier to maintain.

Syntax

class Parent:
    # parent class code

class Child(Parent):
    # child class code

Example: Simple Inheritance

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

    def greet(self):
        print(f"Hello, my name is {self.name}")

# Child class inherits from Person
class Student(Person):
    def __init__(self, name, age, student_id):
        super().__init__(name, age)  # call parent constructor
        self.student_id = student_id

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

# Creating objects
s1 = Student("Alice", 20, "S101")
s1.greet()         # Inherited method → Hello, my name is Alice
s1.display_id()    # Child class method → My student ID is S101

Types of Inheritance

• Single Inheritance: Child inherits from one parent.
• Multiple Inheritance: Child inherits from multiple parents.
• Multilevel Inheritance: Chain of inheritance (grandparent → parent → child).
• Hierarchical Inheritance: Multiple children inherit from the same parent.
• Hybrid Inheritance: Combination of two or more types of inheritance.

Practice Questions

1. Create a parent class Vehicle with a method vehicle_type(). Create a child class Car that inherits it and adds a method car_brand().
2. Implement multilevel inheritance: Grandparent → Parent → Child with a method in each class and call them from the child object.
3. Create two parent classes and a child class using multiple inheritance, then call methods from both parents.
4. Modify the child class to override a method from the parent class and test the output.
5. Design a Teacher class that inherits from a Person class and adds a subject attribute. Create an object and display all details.

Python Iterators

In Python, an iterator is an object that allows you to traverse through all the elements of a collection (like lists, tuples, or dictionaries) one by one. Iterators are used with loops and are memory-efficient because they do not store all elements at once.

Iterator vs Iterable

• Iterable: Any Python object capable of returning its elements one by one (e.g., list, tuple, string).
• Iterator: The object returned by the iter() function, which is used to traverse an iterable.

Creating an Iterator

my_list = [1, 2, 3, 4]

# Get an iterator using iter()
my_iter = iter(my_list)

# Access elements using next()
print(next(my_iter))  # 1
print(next(my_iter))  # 2
print(next(my_iter))  # 3
print(next(my_iter))  # 4
# next(my_iter)  # Raises StopIteration

Using Iterators in Loops

Iterators are commonly used with for loops, which handle the StopIteration automatically.

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)
# Output:
# apple
# banana
# cherry

Creating a Custom Iterator

class Counter:
    def __init__(self, low, high):
        self.current = low
        self.high = high

    def __iter__(self):
        return self

    def __next__(self):
        if self.current > self.high:
            raise StopIteration
        else:
            self.current += 1
            return self.current - 1

# Using the custom iterator
for num in Counter(1, 5):
    print(num)
# Output: 1 2 3 4 5

Practice Questions

1. Convert a list of numbers into an iterator and print all elements using next().
2. Create a string iterator and print each character one by one.
3. Write a custom iterator that generates the first N even numbers.
4. Explain the difference between iter() and next() with examples.
5. Create a loop that prints elements of a tuple using an iterator instead of a for loop.

Python Polymorphism

In Python, polymorphism means the ability of a function, method, or object to take multiple forms. It allows the same operation to behave differently on different data types or classes.

Polymorphism with Functions

The same function name can work with different data types.

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

print(add(5, 10))        # Output: 15 (integers)
print(add("Hello ", "World"))  # Output: Hello World (strings)
print(add([1, 2], [3, 4]))     # Output: [1, 2, 3, 4] (lists)

Polymorphism with Methods

Different classes can have methods with the same name, performing different tasks.

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!

Polymorphism with Inheritance

Child classes can override methods of the parent class while maintaining the same method name.

class Vehicle:
    def start(self):
        print("Vehicle starts")

class Car(Vehicle):
    def start(self):
        print("Car starts")

v = Vehicle()
c = Car()
v.start()  # Vehicle starts
c.start()  # Car starts

Key Points

• Polymorphism increases flexibility and reusability of code.
• It allows the same interface to work for different types of objects.
• Commonly used in object-oriented programming with method overriding.

Practice Questions

1. Write a function that adds two numbers or concatenates two strings using the same function name.
2. Create two classes Bird and Fish with a method move(), each printing different outputs. Call move() for both objects.
3. Demonstrate method overriding with a parent class Shape and child classes Circle and Square.
4. Explain how polymorphism is useful when working with a list of different objects.
5. Create a list of objects from different classes that share a method name and call that method in a loop.

Python Scope

In Python, scope refers to the region of the program where a variable is accessible. Understanding scope is important to avoid naming conflicts and to know where a variable can be used.

Types of Scope in Python

• Local Scope: Variables defined inside a function. Accessible only within that function.
• Global Scope: Variables defined outside any function. Accessible anywhere in the file.
• Enclosing Scope: Variables in the local scope of enclosing functions (used in nested functions).
• Built-in Scope: Names preassigned in Python, like print(), len(), etc.

Local Scope Example

def greet():
    name = "Alice"  # Local variable
    print(name)

greet()           # Output: Alice
# print(name)     # Error: name is not defined outside the function

Global Scope Example

name = "Bob"  # Global variable

def greet():
    print(name)   # Can access global variable

greet()         # Output: Bob
print(name)     # Output: Bob

Using global Keyword

To modify a global variable inside a function, use the global keyword.

x = 10

def modify():
    global x
    x = 20

modify()
print(x)  # Output: 20

Enclosing (Nested) Scope Example

def outer():
    x = "Outer variable"
    def inner():
        print(x)  # Accesses variable from enclosing function
    inner()

outer()  # Output: Outer variable

Practice Questions

1. Define a local variable inside a function and try to print it outside the function. What happens?
2. Create a global variable and modify it inside a function using the global keyword.
3. Write a nested function and access the variable from the outer function.
4. Explain the difference between local and global scope with an example.
5. List some Python built-in functions and explain their scope.

Python Modules

In Python, a module is a file containing Python code, such as functions, classes, or variables, that can be imported and used in other Python programs. Modules help organize code, make it reusable, and improve readability.

Creating a Module

Create a Python file (e.g., mymodule.py) with functions or variables:

# mymodule.py
def greet(name):
    print(f"Hello, {name}!")

pi = 3.14159

Using a Module

# main.py
import mymodule

mymodule.greet("Alice")  # Output: Hello, Alice!
print(mymodule.pi)       # Output: 3.14159

Importing Specific Items

from mymodule import greet

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

Renaming Modules

import mymodule as mm

mm.greet("Charlie")  # Output: Hello, Charlie!

Built-in Modules

Python provides many built-in modules, such as:

• math – mathematical operations
• random – generate random numbers
• datetime – work with dates and times
• os – operating system functionality
• sys – system-specific parameters and functions

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

import random
print(random.randint(1, 10))  # Output: Random number between 1 and 10

Practice Questions

1. Create a module calculator.py with functions for addition, subtraction, multiplication, and division. Import and use it in another file.
2. Import only the sqrt() function from the math module and calculate the square root of 49.
3. Use the random module to generate a random number between 50 and 100.
4. Rename a module during import and use its function.
5. List 5 other built-in modules in Python and explain their purpose.

Python Dates

In Python, the datetime module is used to work with dates and times. It allows you to create, manipulate, and format date and time objects easily.

Importing the datetime Module

import datetime

Getting the Current Date and Time

now = datetime.datetime.now()
print(now)            # Output: 2025-09-29 13:45:12.345678
print(now.year)       # Current year
print(now.month)      # Current month
print(now.day)        # Current day

Creating a Specific Date

my_date = datetime.datetime(2025, 12, 25)
print(my_date)        # Output: 2025-12-25 00:00:00

Formatting Dates

You can format dates using the strftime() method:

today = datetime.datetime.now()
print(today.strftime("%Y-%m-%d"))    # 2025-09-29
print(today.strftime("%d/%m/%Y"))    # 29/09/2025
print(today.strftime("%A, %B %d"))   # Monday, September 29

Timedelta: Date Arithmetic

The timedelta class allows you to add or subtract days, seconds, or other time intervals.

from datetime import datetime, timedelta

today = datetime.now()
tomorrow = today + timedelta(days=1)
yesterday = today - timedelta(days=1)

print("Tomorrow:", tomorrow)
print("Yesterday:", yesterday)

Practice Questions

1. Get the current date and time and print only the year, month, and day separately.
2. Create a datetime object for your birthday and print it.
3. Format the current date as DD-MM-YYYY and Month Day, Year.
4. Calculate the date 10 days from today using timedelta.
5. Write a program to calculate the number of days between two dates.

Python Math Module

In Python, the math module provides a wide range of mathematical functions and constants. It is commonly used for advanced mathematical operations like square root, trigonometry, factorials, and more.

Importing the math Module

import math

Common Math Functions

• math.sqrt(x) – Returns the square root of x.
• math.pow(x, y) – Returns x raised to the power y.
• math.ceil(x) – Returns the smallest integer greater than or equal to x.
• math.floor(x) – Returns the largest integer less than or equal to x.
• math.factorial(x) – Returns the factorial of x.
• math.gcd(x, y) – Returns the greatest common divisor of x and y.
• math.sin(x), math.cos(x), math.tan(x) – Trigonometric functions (x in radians).

Examples

import math

print(math.sqrt(16))      # 4.0
print(math.pow(2, 3))     # 8.0
print(math.ceil(4.2))     # 5
print(math.floor(4.8))    # 4
print(math.factorial(5))  # 120
print(math.gcd(12, 18))   # 6
print(math.sin(math.pi/2))# 1.0

Constants in Math Module

• math.pi – Value of π (3.14159…)
• math.e – Value of Euler’s number e (2.71828…)

Practice Questions

1. Calculate the square root of 49 using the math module.
2. Find 3 to the power of 4 using math.pow().
3. Use math.ceil() and math.floor() on 7.3 and 7.7 and print results.
4. Calculate factorial of 6 using math.factorial().
5. Compute the sine of 90 degrees (Hint: convert degrees to radians first).

Python JSON

In Python, JSON (JavaScript Object Notation) is a popular data format used for exchanging data between a server and a client. Python provides the json module to work with JSON data, allowing you to convert between Python objects and JSON strings.

Importing the json Module

import json

Converting Python Object to JSON

Use json.dumps() to convert Python objects to JSON strings:

import json

data = {
    "name": "Alice",
    "age": 25,
    "city": "New York"
}

json_string = json.dumps(data)
print(json_string)
# Output: {"name": "Alice", "age": 25, "city": "New York"}

Converting JSON to Python Object

Use json.loads() to parse a JSON string back into a Python object:

json_data = '{"name": "Bob", "age": 30, "city": "London"}'
python_obj = json.loads(json_data)
print(python_obj)
# Output: {'name': 'Bob', 'age': 30, 'city': 'London'}
print(python_obj["name"])  # Bob

Reading JSON from a File

import json

with open("data.json", "r") as file:
    data = json.load(file)
print(data)

Writing JSON to a File

import json

data = {"name": "Charlie", "age": 28, "city": "Paris"}

with open("data.json", "w") as file:
    json.dump(data, file)

Practice Questions

1. Convert a Python dictionary {"fruit": "apple", "quantity": 10} to a JSON string.
2. Parse the JSON string '{"name": "Eve", "age": 22}' into a Python dictionary and print the age.
3. Write a Python list of dictionaries to a JSON file.
4. Read the JSON file created above and print each item.
5. Explain the difference between json.load() and json.loads().

Python RegEx (Regular Expressions)

In Python, RegEx (Regular Expressions) is a powerful tool for searching, matching, and manipulating strings. Python provides the re module to work with regular expressions.

Importing the re Module

import re

Basic Functions in re Module

• re.match(pattern, string) – Checks if the string starts with the pattern.
• re.search(pattern, string) – Searches the entire string for the pattern.
• re.findall(pattern, string) – Returns a list of all matches in the string.
• re.split(pattern, string) – Splits the string by the pattern.
• re.sub(pattern, replacement, string) – Replaces occurrences of the pattern with the replacement.

Example: Searching a Pattern

import re

text = "My phone number is 123-456-7890"
pattern = r"\d{3}-\d{3}-\d{4}"

match = re.search(pattern, text)
if match:
    print("Found:", match.group())
# Output: Found: 123-456-7890

Example: Finding All Matches

text = "Email me at alice@example.com or bob@example.com"
pattern = r"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}"
emails = re.findall(pattern, text)
print(emails)
# Output: ['alice@example.com', 'bob@example.com']

Example: Replacing Text

text = "I love cats"
new_text = re.sub(r"cats", "dogs", text)
print(new_text)
# Output: I love dogs

Practice Questions

1. Write a regular expression to match all phone numbers in the format XXX-XXX-XXXX in a string.
2. Find all email addresses in a given text using RegEx.
3. Replace all occurrences of "Python" with "Java" in a string using re.sub().
4. Split a string by one or more spaces using re.split().
5. Explain the difference between re.match() and re.search() with examples.

Python PIP

PIP stands for "Python Package Installer". It is a tool used to install and manage Python packages from the Python Package Index (PyPI). Using PIP, you can easily add external libraries to your Python projects.

Checking if PIP is Installed

pip --version
# Output example: pip 23.1.2 from /usr/lib/python3/site-packages/pip (python 3.10)

Installing a Package

pip install package_name
# Example:
pip install requests

Upgrading a Package

pip install --upgrade package_name
# Example:
pip install --upgrade requests

Uninstalling a Package

pip uninstall package_name
# Example:
pip uninstall requests

Listing Installed Packages

pip list

Searching for Packages

pip search keyword
# Example:
pip search flask

Practice Questions

1. Check if PIP is installed on your system and note the version.
2. Install the numpy package using PIP.
3. Upgrade the numpy package to the latest version.
4. Uninstall the numpy package using PIP.
5. List all installed packages and find the version of requests.

Python Try…Except

In Python, the try…except block is used to handle exceptions (errors) gracefully. Instead of stopping the program when an error occurs, you can catch the error and take appropriate action.

Basic Syntax

try:
    # Code that might raise an exception
except ExceptionType:
    # Code to handle the exception

Example: Handling Division by Zero

try:
    x = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero!")
# Output: Cannot divide by zero!

Handling Multiple Exceptions

try:
    x = int(input("Enter a number: "))
    y = 10 / x
except ValueError:
    print("Invalid input! Please enter a number.")
except ZeroDivisionError:
    print("Cannot divide by zero!")

Using else and finally

- else block executes if no exception occurs.
- finally block executes regardless of whether an exception occurred or not.

try:
    x = 10 / 2
except ZeroDivisionError:
    print("Cannot divide by zero!")
else:
    print("Division successful!")
finally:
    print("Execution complete.")
# Output:
# Division successful!
# Execution complete.

Practice Questions

1. Write a program that catches a ValueError when a user enters a non-integer value.
2. Handle ZeroDivisionError when dividing two numbers input by the user.
3. Create a try…except block to handle multiple exceptions in one program.
4. Use finally to print a message after executing a try…except block, regardless of errors.
5. Write a program that reads a file and handles FileNotFoundError gracefully.

Python User Input

In Python, the input() function is used to take input from the user. By default, the input is taken as a string, but it can be converted into other data types as needed.

Basic Syntax

variable = input("Enter something: ")

Example: Taking String Input

name = input("Enter your name: ")
print("Hello, " + name + "!")

Example: Taking Integer Input

age = int(input("Enter your age: "))
print("You are", age, "years old.")

Example: Taking Float Input

price = float(input("Enter the price: "))
print("The price is", price)

Using Input in Calculations

a = int(input("Enter first number: "))
b = int(input("Enter second number: "))
sum = a + b
print("Sum:", sum)

Practice Questions

1. Take a string input from the user and print it in uppercase.
2. Take two integers as input and print their sum, difference, and product.
3. Take a float input for the radius of a circle and calculate its area.
4. Write a program that asks for the user's name and age and prints a greeting message.
5. Take a number input and check if it is even or odd.

Python String Formatting

In Python, string formatting allows you to create strings dynamically by inserting variables or expressions into them. It makes your output readable and customizable.

1. Using the % Operator

name = "Alice"
age = 25
print("My name is %s and I am %d years old." % (name, age))
# Output: My name is Alice and I am 25 years old.

2. Using the str.format() Method

name = "Bob"
age = 30
print("My name is {} and I am {} years old.".format(name, age))
# Output: My name is Bob and I am 30 years old.

# Using positional arguments
print("I am {1} years old and my name is {0}.".format(name, age))

3. Using f-Strings (Python 3.6+)

name = "Charlie"
age = 28
print(f"My name is {name} and I am {age} years old.")
# Output: My name is Charlie and I am 28 years old.

# Using expressions
print(f"Next year, I will be {age + 1} years old.")
# Output: Next year, I will be 29 years old.

4. Formatting Numbers

pi = 3.14159265
print("Pi rounded to 2 decimal places: {:.2f}".format(pi))
# Output: Pi rounded to 2 decimal places: 3.14

print(f"Pi rounded to 3 decimal places: {pi:.3f}")
# Output: Pi rounded to 3 decimal places: 3.142

Practice Questions

1. Print your name and age using the % operator.
2. Use str.format() to print a sentence with your favorite color and hobby.
3. Create an f-string that shows the result of 5 + 10 in a sentence.
4. Format the number 123.456789 to display only 2 decimal places using f-strings.
5. Use string formatting to align text in a table-like output for three items and their prices.

Python File Handling

In Python, file handling allows you to create, read, update, and delete files. The built-in open() function is used to work with files in different modes.

Opening a File

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

File Modes

• "r" – Read (default), file must exist
• "w" – Write, creates a new file or truncates existing file
• "a" – Append, adds content to the end of the file
• "x" – Create, creates a new file, fails if file exists
• "b" – Binary mode (used with other modes, e.g., "rb", "wb")

Writing to a File

file = open("example.txt", "w")
file.write("Hello, World!\n")
file.write("Python File Handling")
file.close()

Appending to a File

file = open("example.txt", "a")
file.write("\nThis is appended text.")
file.close()

Using with Statement

The with statement automatically closes the file after its block finishes:

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

Reading Line by Line

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

Practice Questions

1. Create a file named data.txt and write your name and age into it.
2. Read the content of data.txt and print it line by line.
3. Append a new line to data.txt containing your favorite hobby.
4. Use the with statement to read and print the file content.
5. Create a binary file and write some bytes into it, then read the bytes back.

Python Requests

In Python, the Requests library is used to send HTTP requests easily. It allows you to interact with web services, APIs, and websites by sending GET, POST, PUT, DELETE, and other HTTP requests.

Installing Requests

pip install requests

Making a GET Request

import requests

response = requests.get("https://jsonplaceholder.typicode.com/posts/1")
print(response.status_code)  # 200
print(response.text)         # JSON data as string
print(response.json())       # JSON data as Python dictionary

Making a POST Request

import requests

data = {"title": "foo", "body": "bar", "userId": 1}
response = requests.post("https://jsonplaceholder.typicode.com/posts", json=data)
print(response.status_code)  # 201
print(response.json())       # Response data

Adding Headers

headers = {"Authorization": "Bearer YOUR_TOKEN"}
response = requests.get("https://api.example.com/data", headers=headers)
print(response.json())

Handling Query Parameters

params = {"userId": 1}
response = requests.get("https://jsonplaceholder.typicode.com/posts", params=params)
print(response.json())

Practice Questions

1. Install the Requests library and make a GET request to https://api.github.com.
2. Send a POST request to https://jsonplaceholder.typicode.com/posts with custom data and print the response.
3. Use query parameters to fetch posts for a specific user from the JSONPlaceholder API.
4. Add custom headers to a GET request and print the JSON response.
5. Explain the difference between response.text and response.json().

Python BeautifulSoup

BeautifulSoup is a powerful Python library used for web scraping. It helps you parse and navigate HTML or XML documents to extract specific information such as titles, links, tables, and text data. It’s often used alongside the requests library to download webpage content and then process it locally.

Installation

pip install beautifulsoup4
pip install requests

After installation, import both libraries in your Python file to start scraping:

from bs4 import BeautifulSoup
import requests

Basic Example

from bs4 import BeautifulSoup
import requests

url = "https://example.com"
response = requests.get(url)
soup = BeautifulSoup(response.text, "html.parser")

print(soup.title.text)  # Print the page title
print(soup.find("p").text)  # Print the first paragraph

Finding Elements

# Find first <h1> tag
h1_tag = soup.find("h1")
print(h1_tag.text)

# Find all <p> tags
paragraphs = soup.find_all("p")
for p in paragraphs:
    print(p.text)

Accessing Attributes

link = soup.find("a")
print(link["href"])  # Get href attribute of the first <a> tag

Using CSS Selectors

# Find elements by CSS selectors
titles = soup.select("h2.article-title")
for title in titles:
    print(title.text)

# Find elements by class or ID
content = soup.select_one("#main-content")
print(content.text)

Extracting Links, Images, and Text

# Extract all hyperlinks
for a in soup.find_all("a", href=True):
    print(a["href"])

# Extract all image sources
for img in soup.find_all("img", src=True):
    print(img["src"])

# Extract all text content from the page
print(soup.get_text())

Real-World Use Cases

• Scraping headlines, prices, or product details from e-commerce websites.
• Extracting news articles or blog posts for analysis.
• Collecting research data from public databases or documentation sites.
• Building automated bots for monitoring web updates or SEO analysis.

Common Errors and Fixes

• Problem: Page returns empty content. Fix: Check if JavaScript loads the data — use Selenium or an API instead.
• Problem: "NoneType" error when using .text. Fix: Add a condition:

  if tag:
      print(tag.text)

• Problem: Encoding issues. Fix: Use response.encoding = "utf-8" before parsing.

Practice Questions

1. Install BeautifulSoup and requests library, and fetch the title of https://example.com.
2. Extract and print all paragraph texts from a given webpage.
3. Find all hyperlinks (<a> tags) and print their URLs.
4. Parse an HTML string and extract the text from a specific tag.
5. Explain the difference between find() and find_all() in BeautifulSoup.
6. Use select() to extract all headings with a specific CSS class.
7. Scrape all image URLs from a blog page and save them into a list.
8. Build a mini script that collects all article titles from a news website.

BeautifulSoup is an essential tool for ethical hackers, data analysts, and developers who want to automate information gathering. When combined with Python libraries like requests, pandas, or re, it becomes a powerful way to extract and structure data from any website efficiently.

Top Python Projects for Cyber Security

Python is one of the most widely used languages in cybersecurity due to its simplicity and the powerful libraries it provides for networking, automation, and ethical hacking. Building real-world projects is the best way to strengthen your understanding of security concepts and practical hacking skills.

Beginner Level Projects

Perfect for those just starting out in cybersecurity and Python. These projects help you understand the basics of networking, automation, and data handling.

• Password Strength Checker – Create a tool that analyzes password complexity and suggests improvements.
• Port Scanner – Build a simple port scanner using the socket module to find open ports on a target system.
• Network Packet Sniffer – Capture and analyze packets using scapy to understand how data travels in networks.
• Keylogger (for learning purposes only) – Understand how keystroke capturing works in ethical environments.
• Website Vulnerability Scanner – Use requests and BeautifulSoup to identify outdated headers or open directories.

Intermediate Level Projects

These projects involve multiple libraries and simulate real-world security automation tasks and penetration testing workflows.

• Brute Force Attack Simulator – Write a tool that tests password lists against login forms or SSH services.
• Network Intrusion Detection System (IDS) – Use scapy and socket to detect suspicious packet patterns.
• Steganography Tool – Hide and extract secret messages inside images using PIL or OpenCV.
• Phishing URL Detector – Train a machine learning model with scikit-learn to detect fake or malicious URLs.
• File Encryption/Decryption Tool – Implement AES or RSA algorithms using the cryptography module.

Advanced Level Projects

For professionals who want to master ethical hacking automation, real-time monitoring, and AI-powered defense systems.

• Automated Penetration Testing Suite – Combine tools like Nmap, Whois, and Shodan APIs to automate reconnaissance.
• AI-based Malware Detection System – Use Python with TensorFlow or PyTorch to classify files as safe or malicious.
• Web Application Security Scanner – Build a full scanner to check SQLi, XSS, and CSRF vulnerabilities.
• Custom VPN or Proxy Server – Use socket and ssl modules to create a secure communication channel.
• Cyber Threat Intelligence (CTI) Dashboard – Collect real-time threat data from APIs, analyze it, and display results using Flask or Django.

Practice Tasks

1. Create a basic port scanner using the socket library and display all open ports for a given IP.
2. Develop a password strength checker that validates password length, symbols, and entropy.
3. Build a simple encryption/decryption app using the cryptography module.
4. Analyze HTTP headers of a website and print possible security risks.
5. Design a script that detects phishing URLs using pattern matching.

These projects help you move from basic scripting to real-world cybersecurity applications. Each one enhances your Python skills while preparing you for ethical hacking, network defense, and security automation tasks.

Elite Python Series – Certification Program

Welcome to the Elite Python Series — a rapid, hands-on course designed to help you master Python programming from fundamentals to advanced topics in the shortest time possible. Each topic in this series includes detailed explanations, examples, and practice questions to strengthen your concepts.

🎓 Certification Notice: To receive your official Elite Python Series Certification, you must register yourself for the program. Registration gives you access to live sessions, assignments, evaluation tests, and a personalized digital certificate upon completion.

👉 Register now for the Elite Python Series Certification through the official Cyber_Squad6351 platform to begin your certified Python learning journey.

Python Requests

In Python, the Requests library is one of the most popular tools for working with the web. It allows you to send HTTP requests to interact with websites, APIs, and servers effortlessly — enabling everything from downloading data to automating web interactions in a few lines of code.

Installing Requests

pip install requests

Making a GET Request

import requests

response = requests.get("https://jsonplaceholder.typicode.com/posts/1")
print(response.status_code)  # 200 means OK
print(response.text)         # Prints the response body as text
print(response.json())       # Converts JSON response into a Python dictionary

Making a POST Request

import requests

data = {"title": "foo", "body": "bar", "userId": 1}
response = requests.post("https://jsonplaceholder.typicode.com/posts", json=data)
print(response.status_code)  # 201 means created successfully
print(response.json())       # Prints the newly created resource details

Adding Headers

headers = {"Authorization": "Bearer YOUR_TOKEN"}
response = requests.get("https://api.example.com/data", headers=headers)
print(response.json())

Handling Query Parameters

params = {"userId": 1}
response = requests.get("https://jsonplaceholder.typicode.com/posts", params=params)
print(response.json())

Common Use Cases

• Fetching live data from APIs (e.g., weather, crypto prices, social media).
• Testing web applications and performing automated API checks.
• Sending form data or authentication tokens for login automation.
• Scraping lightweight data from static websites when combined with BeautifulSoup.

Practice Questions

1. Install the Requests library and make a GET request to https://api.github.com.
2. Send a POST request to https://jsonplaceholder.typicode.com/posts with custom data and print the response.
3. Use query parameters to fetch posts for a specific user from the JSONPlaceholder API.
4. Add custom headers to a GET request and print the JSON response.
5. Explain the difference between response.text and response.json().

The Requests library simplifies the way you interact with the web — making API integration, automation, and data retrieval in Python smooth and intuitive. Once you master Requests, you’ll have a strong foundation for projects involving APIs, data collection, and web automation.

💡 Tip: Complete this lesson and take the short quiz available after registration to earn progress points toward your Elite Python Certification.

Python BeautifulSoup

BeautifulSoup is another essential Python library, mainly used for web scraping. It helps you parse HTML or XML documents and extract meaningful data such as titles, links, images, or table data. When combined with the requests library, it becomes a complete toolset for web data extraction and automation.

Installation

pip install beautifulsoup4
pip install requests

Basic Example

from bs4 import BeautifulSoup
import requests

url = "https://example.com"
response = requests.get(url)
soup = BeautifulSoup(response.text, "html.parser")

print(soup.title.text)
print(soup.find("p").text)

Finding Elements

# Find first 
 tag
h1_tag = soup.find("h1")
print(h1_tag.text)

# Find all 
 tags
paragraphs = soup.find_all("p")
for p in paragraphs:
    print(p.text)

Accessing Attributes

link = soup.find("a")
print(link["href"])  # Get href attribute of the first  tag

# Find elements by CSS selectors
titles = soup.select("h2.article-title")
for title in titles:
    print(title.text)

# Find elements by class or ID
content = soup.select_one("#main-content")
print(content.text)

# Extract all hyperlinks
for a in soup.find_all("a", href=True):
    print(a["href"])

# Extract all image sources
for img in soup.find_all("img", src=True):
    print(img["src"])

# Extract all text content from the page
print(soup.get_text())

• Go to python.org/downloads.
• Choose the version suitable for your operating system (Windows/macOS/Linux).
• Run the installer and check the box “Add Python to PATH.”
• After installation, open the terminal or CMD and type: python --version to verify the installation.

Which IDE is best for Python development?

The best IDE depends on your workflow:

• VS Code – lightweight and powerful with Python extensions.
• PyCharm – professional IDE with smart debugging tools.
• Jupyter Notebook – great for data science and AI projects.
• Thonny – simple IDE for beginners learning Python.

How do I run a Python program?

Save your Python code in a file with the .py extension (for example, hello.py). Then open your terminal or command prompt and run:
python hello.py
This will execute your program. You can also run Python code inside IDEs like VS Code, PyCharm, or Jupyter.

What are Python libraries and modules?

Libraries and modules are reusable pieces of code that add functionality to your Python programs. For example:

• Requests – for handling web requests.
• BeautifulSoup – for web scraping.
• Pandas – for data manipulation.
• Flask/Django – for web app development.

How do I learn Python effectively?

Start by understanding core concepts like variables, loops, and functions. Then, move on to projects—automation scripts, small games, or data analysis tasks. Practice regularly, read official documentation, and explore open-source projects on GitHub. Joining Python communities (Reddit, Discord, or Stack Overflow) also accelerates your learning.

Can I use Python for cybersecurity or ethical hacking?

Yes! Python is one of the most used languages in cybersecurity. You can create network scanners, brute-force tools, packet sniffers, and vulnerability checkers. Libraries like Scapy, Socket, and Requests make it easy to interact with networks and servers. Always use these tools ethically and with permission.

What’s new in the latest Python versions?

Python 3.12+ introduces performance boosts, more precise error messages, and improved type hinting. These updates help developers write faster and more reliable code. You can check the latest release notes on the official Python documentation.

Is Python free and open-source?

Yes, Python is completely free and open-source. It is maintained by the Python Software Foundation (PSF) and has a global community of contributors. You can use it for personal, academic, or commercial purposes without paying any licensing fees.