Python Basics

On This Page

• 2.1  Variables — Naming & Assignment Rules
• 2.2  Data Types in Python
• 2.3  Type Casting / Type Conversion
• 2.4  Input and Output
• 2.5  Comments in Python
• 2.6  Keywords in Python
• 2.7  Operators
• 2.8  Expressions
• 2.9  Practical Exercises
• 2.10  Module Quiz (MCQs)
• 2.11  Module Assignment
• 2.12  Interview Questions — Module 2
• 2.13  Student Notes Page

Module 2: Python Basics

2.1  Variables — Naming & Assignment Rules

A variable is simply a named container used to store data in memory so that it can be used and modified later in the program. Unlike some languages, Python does not require you to declare the type of a variable — it figures that out automatically based on the value you assign.

name = "Iqubal"
age = 28
course_fee = 15000.50
is_enrolled = True

print(name, age, course_fee, is_enrolled)

Rules for Naming Variables

• Must start with a letter or underscore (_), never a number
• Can contain letters, numbers, and underscores only — no spaces or special characters
• Case-sensitive: Name and name are different variables
• Cannot use Python keywords (like class, for) as variable names
• Use meaningful names: student_fee is better than x

# Assign multiple variables in one line
a, b, c = 10, 20, 30
print(a, b, c)

# Assign the same value to multiple variables
x = y = z = 100
print(x, y, z)

2.2  Data Types in Python

Every value in Python has a data type that determines what kind of operations can be performed on it. Python automatically detects the data type — this is called dynamic typing.

x = 28
y = 28.5
z = "Samantus"
print(type(x))
print(type(y))
print(type(z))

2.3  Type Casting / Type Conversion

Type casting means converting a value from one data type to another — for example, converting user input (which is always text/string) into a number so you can perform calculations on it.

a = "25"          # string
b = int(a)        # convert to integer
print(b + 5)      # now math works

c = 9.8
d = int(c)        # float to int (drops decimal)
print(d)

e = 100
f = str(e)        # int to string
print("Fee: " + f)

2.4  Input and Output

The input() function lets your program take data from the user, and print() displays output back to the screen.

name = input("Enter your name: ")
age = int(input("Enter your age: "))
print("Hello", name, "- you are", age, "years old")

name = "Priya"
fee = 15000
print(f"Hi {name}, your course fee is Rs.{fee}")

2.5  Comments in Python

Comments are notes in your code that Python ignores when running the program. They help you and others understand what the code does.

# This is a single-line comment
print("Hello")   # this comment is at the end of a line

"""
This is a multi-line comment / docstring
often used to explain what a function does
"""

2.6  Keywords in Python

Keywords are reserved words that have special meaning in Python and cannot be used as variable names.

2.7  Operators

Operators are special symbols used to perform operations on variables and values.

a = 10
b = 3
print(a + b)   # 13
print(a % b)   # 1  (remainder)
print(a ** b)  # 1000 (power)
print(a // b)  # 3  (floor division)

2.8  Expressions

An expression is any combination of values, variables, and operators that Python can evaluate to produce a result.

price = 500
quantity = 3
discount = 0.10

total = price * quantity * (1 - discount)
print(total)

2.9  Practical Exercises

Basic (5 Questions)

1. Create variables for your name, age, and city, and print them together.

2. Store two numbers in variables and print their sum, difference, and product.

3. Take a number as input from the user and print its data type.

4. Write a program using an f-string to print 'My name is ___ and I am ___ years old'.

5. Add comments explaining each line of one of your earlier programs.

Intermediate (5 Questions)

1. Take two numbers as input (as strings) and correctly convert and add them.

2. Write a program to swap the values of two variables without using a third variable.

3. Create a simple bill calculator: price, quantity, and print the total using an expression.

4. Demonstrate the difference between int(9.9) and round(9.9) with printed output.

5. List 5 Python keywords and explain what each one is used for.

Advanced (5 Questions)

1. Write a program that calculates GST (18%) on a product price and prints the final amount.

2. Explain, with an example, why input() always needs type casting for numeric operations.

3. Create a program using multiple assignment to initialize 4 variables in a single line.

4. Research the difference between is and == in Python and demonstrate with a code example.

5. Build a simple 'Student Fee Calculator' that takes fee, discount %, and prints the final payable fee.

2.10  Module Quiz (MCQs)

2.11  Module Assignment

Assignment: Personal Expense Calculator

• Take 3 expense items and their amounts as input from the user (e.g., food, travel, shopping).
• Convert inputs to appropriate data types using type casting.
• Calculate the total expense using an expression.
• Print a clean, formatted summary using an f-string, e.g. 'Your total expense this month is Rs.____'.

Expected Output: A working script that takes 3 inputs, correctly type-casts them, computes the total using an expression, and prints a nicely formatted summary line.

2.12  Interview Questions — Module 2

• Q: What is the difference between a variable and a keyword?
  A: A variable is a name you create to store data, while a keyword is a reserved word (like if, for, class) with special meaning that cannot be used as a variable name.
• Q: Why does Python not require explicit type declaration?
  A: Python uses dynamic typing — it automatically infers a variable's type from the assigned value at runtime.
• Q: What is type casting? Give an example.
  A: Type casting is converting a value from one data type to another, e.g. int("25") converts the string "25" into the integer 25.
• Q: What is the difference between == and =?
  A: = is the assignment operator used to store a value in a variable, while == is the comparison operator used to check equality.

2.13  Student Notes Page

Use this space to write down key points, doubts, and your own examples from today's session.