In Python, comments are notes written inside the code that are not executed by the compiler/interpreter. They are used to explain the code, make it easier to understand, and help others (or yourself) when revisiting the code later.

Types of Comments in Python:

1. Single-line Comment

• Starts with a # (hash symbol)
• Anything written after # on that line is ignored by Python

# This is a single-line comment
print("Hello, World!") # This prints a message

2. Multi-line Comment

Python does not have a special syntax for multi-line comments. We can use triple quotes (''' or """) as a docstring-like block (not assigned to anything).

'''
This is another way
to write multi-line comments
using triple quotes
'''
print("Python comments example")

1. Integer (int)

• Whole numbers (positive, negative, or zero)
• Do not have a decimal point
• Example values: -10, 0, 25, 1000

x = 25
y = -7
print("x:", x)  # Output: 25
print("y:", y)  # Output: -7

2. Float (float)

• Numbers that have a decimal point
• Can represent numbers in scientific notation (e.g., 1.2e3 means 1200.0)
• Example values: 3.14, -0.5, 2.0, 1.2e3

a = 3.14
print("a:", a)  # Output: 3.14

Operator Precedence

Operator precedence means the order in which math operations happen. In Python, operators with higher precedence are evaluated first. If two operators have the same precedence, then associativity (left-to-right or right-to-left) decides the order.

x = 100 / 5 * 2 + 3
print(x)
# Output: 43.0

The regular if-else uses multiple lines and is clear and easier to understand for beginners. The shorthand if-else fits into one line (also called ternary operator) and is best for simple conditions and compact code. Both do the same thing.

Regular if-else:

age = 18
if age >= 18:
    status = "Adult"
else:
    status = "Minor"

Shorthand if-else:

status = "Adult" if age >= 18 else "Minor"

The range() function is used in a for loop to generate a sequence of numbers. It does not create a list directly but gives a range object that produces numbers one by one. Mostly used to repeat a loop a specific number of times.

Syntax:

range(start, stop, step)
# start → (optional) starting number (default = 0)
# stop → ending number (not included)
# step → (optional) difference between numbers (default = 1)

Example:

for i in range(0, 10, 2):
    print(i)
# Output: 0 2 4 6 8

In Python, default parameters let you set a value that is used if no argument is passed.

Example:

def greet(name="Guest"):
    print("Hello", name)

greet()        # Output: Hello Guest
greet("Ali")  # Output: Hello Ali

If you don’t give a name, it uses “Guest” as default.

Modular Programming

Modular programming is dividing a big program into small, independent modules (functions or files). Benefits include:

• A function/module written once can be used again in different programs
• Errors can be found easily since each module is separate
• If a formula changes, we only update that specific function, not the whole program
• Code is organized into logical sections (functions/files)
• Easier for others (and yourself) to understand
• Python allows importing your own modules (import mymodule) or built-in ones (import math)

Example:

# Modular program using functions
def area_rectangle(length, width):
    return length * width

def area_circle(radius):
    return 3.14 * radius * radius

# Main program
print("Area of rectangle:", area_rectangle(10, 5))
print("Area of circle:", area_circle(7))

Class:

In Python, a class is a blueprint or template that defines the structure and behavior of objects. It contains attributes (variables) and methods (functions) which describe what the object will have and what it can do. A class itself does not take up memory; it only provides the design for creating objects.

Object:

An object, on the other hand, is an instance of a class. It is the actual entity that is created from the class and stored in memory. Each object has its own unique data, even though it follows the structure defined by the class.

Example:

If we create a class named Car with attributes like brand and color, and a method to drive, then creating:

car1 = Car("Toyota", "Red")
car2 = Car("Honda", "Blue")

will give us two different objects. Both are created from the same class but have different values. The class is like the design of a car, while the object is the actual car built from that design.