PART 1 • LEVEL 02

📦 Data Types & I/O

Learn how Python stores values, identifies their types, accepts keyboard input, converts data and produces clear formatted output.

⏱ 75–90 minutes📚 8 concepts💻 5 programs🧠 6-question quiz

Start Lesson ↓ Jump to Problems

student_profile.pyPython 3

name = input("Name: ")
age = int(input("Age: "))
next_age = age + 1

print(f"Hello, {name}!")
print(f"Next year: {next_age}")

OUTPUTHello, Venu!
Next year: 21

LEARNING OUTCOMES

By the End of This Level

You will be able to store, inspect, receive, convert and display data correctly.

Create variables using meaningful names and assignment.

Distinguish numeric, text, Boolean and empty values.

Use input() and convert text into required data types.

Produce readable output with commas and f-strings.

STORE VALUES

Variables and Assignment

A variable is a meaningful name that refers to a value. Python creates the variable when an assignment statement runs.

In student_name = "Venu", the assignment operator = evaluates the value on the right and associates it with the name on the left.

Remember

= assigns a value; it does not mean “is mathematically equal to.”

EXAMPLE 1

Create and Update Variables

course = "Python"
lessons = 12
progress = 2

progress = progress + 1

print(course)
print("Completed:", progress)

OUTPUT

Python
Completed: 3

Start Correctly

name
student_name
marks2

Begin with a letter or underscore; digits may appear later.

Use Valid Characters

total_marks
course1
_count

Use letters, digits and underscores—never spaces or hyphens.

Avoid Keywords

# Invalid names
class = 10
if = True

Reserved Python keywords cannot be variable names.

Choose Meaningful Names

student_age = 20
total_price = 499.0

Clear names explain the value without needing extra comments.

NUMBER VALUES

Python Numeric Data Types

Python provides different numeric types because whole numbers, decimal values and complex values represent different kinds of information.

🔢

`int`

Whole numbers without a decimal point, such as 25, -7 and 0.

📏

`float`

Numbers with a decimal point, such as 72.5 and -0.25.

🧮

`complex`

Numbers containing real and imaginary parts, such as 3 + 2j.

✅

`bool`

Logical values True and False; Boolean is related to integers.

Value	Type	Typical use
`42`	`int`	Count, age, score
`85.75`	`float`	Average, price, measurement
`2 + 3j`	`complex`	Scientific and engineering calculations
`True`	`bool`	Conditions and yes/no states

OTHER CORE VALUES

Strings, Boolean Values and `None`

TEXT

🔤 String — `str`

A string stores text inside matching quotes.

name = "CodeBhavya"
grade = 'A'
message = "Learn and build"

LOGICAL STATE

🚦 Boolean — `bool`

A Boolean records whether something is true or false.

is_registered = True
is_completed = False

NO VALUE YET

⭕ None — `NoneType`

None represents the intentional absence of a value.

result = None
selected_course = None

Important

"25" is a string because it is inside quotes, while 25 is an integer. Their appearance is similar, but their behavior is different.

INSPECT DATA

Check a Value with `type()`

The built-in type() function reports the data type of a value or variable.

EXAMPLE 2

Inspect Several Values

age = 20
average = 87.5
name = "Venu"
is_ready = True

print(type(age))
print(type(average))
print(type(name))
print(type(is_ready))

OUTPUT

<class 'int'>
<class 'float'>
<class 'str'>
<class 'bool'>

READ USER DATA

Keyboard Input with `input()`

input() displays an optional prompt, waits for the user, and always returns the entered data as a string.

1Show Promptinput("Age: ")

→

2User Types20

→

3String Returned"20"

EXAMPLE 3

Receive and Display a Name

name = input("Enter your name: ")
city = input("Enter your city: ")

print("Student:", name)
print("City:", city)

SAMPLE OUTPUT

Enter your name: Venu
Enter your city: Hyderabad
Student: Venu
City: Hyderabad

Critical rule

Even when the user types digits, input() returns text. Convert the value before performing numeric calculations.

CHANGE REPRESENTATION

Type Conversion

Type conversion creates a value of another compatible type. Common conversion functions are int(), float(), str() and bool().

Function	Purpose	Example	Result
`int()`	Convert to integer	`int("25")`	`25`
`float()`	Convert to decimal number	`float("7.5")`	`7.5`
`str()`	Convert to text	`str(100)`	`"100"`
`bool()`	Convert to logical value	`bool(1)`	`True`

EXAMPLE 4

Calculate Using Converted Input

length = float(input("Length: "))
width = float(input("Width: "))

area = length * width

print("Area =", area)

SAMPLE OUTPUT

Length: 8
Width: 5
Area = 40.0

✓ VALID

age = int("20")
price = float("49.5")

The text contains a compatible numeric value.

✕ VALUEERROR

age = int("twenty")
count = int("4.5")

The text cannot be directly represented as an integer.

DISPLAY CLEARLY

Formatted Output

Use commas for simple labelled output and f-strings when values must appear naturally inside a message.

COMMA-SEPARATED

name = "Venu"
score = 92
print("Student:", name)
print("Score:", score)

print() automatically places a space between comma-separated values.

F-STRING

name = "Venu"
score = 92
print(f"{name} scored {score}")

Prefix the string with f and place expressions inside braces.

EXAMPLE 5

Student Result Card

name = input("Name: ")
marks = float(input("Marks: "))

print(f"Student: {name}")
print(f"Marks: {marks}")
print(f"Passed: {marks >= 40}")

SAMPLE OUTPUT

Name: Venu
Marks: 78.5
Student: Venu
Marks: 78.5
Passed: True

DEBUGGING CORNER

Common Data and Input Mistakes

TypeError

"Age: " + 20

A string and integer cannot be joined with + without conversion.

ValueError

int("twenty")

The text does not contain a valid integer representation.

Wrong result

age = input()
print(age + "1")

Entering 20 produces 201 because both values are strings.

Before calculating:1. Read input2. Identify required type3. Convert4. Calculate5. Display

QUICK REVISION

📌 Data Types & I/O — Quick Revision

Review the complete Level 2 lesson before attempting the quiz and programming problems.

A variable is created when a value is assigned using =.

int stores whole numbers and float stores decimal numbers.

str stores text inside matching quotes.

bool has the values True and False.

None represents the intentional absence of a value.

type() reports the data type of a value.

input() always returns a string.

Use int() or float() before numeric calculations.

f-strings insert values using braces such as f"Age: {age}".

A failed incompatible conversion normally raises a ValueError.

KNOWLEDGE CHECK

Level 2 Quick Quiz

Select one answer for every question, then check your score.

6 Questions

1What type is the value 25.0? int str float bool

2What does input() return? Always an integer A string Always a float A Boolean

3Which statement correctly reads an integer age? age = input.int() age = input(integer) age = str(input()) age = int(input())

4What is the output type of str(100)? str int float NoneType

5Which is a valid variable name? 2marks student-name student_marks class

6What does f"Total: {price}" represent? A comment A formatted string A Boolean expression A conversion error

PRACTICE

🎯 5 Programming Problems — Data Types & I/O

Solve every problem in the browser workspace. The runner uses the displayed sample input, so you can practise input(), conversion, variables, calculations and output.

📈 Data Types & I/O Practice Progress

Solved0 / 5

Completed with Solution0

Total Score0 / 500

Completion0%

A problem counts as Solved when its output passes before the official solution is opened.

1. Personal Greeting

Read a name and display the exact two-line welcome message.

Sample input: VenuExpected output: Hello, Venu! and Welcome to CodeBhavya.

💡 Read the name with input(), then use an f-string.

Official Python Program

name = input()
print(f"Hello, {name}!")
print("Welcome to CodeBhavya.")

2. Age Next Year

Read the current age as an integer and display the age next year.

Sample input: 20Expected output: Next age = 21

💡 Convert the result of input() using int() before adding 1.

Official Python Program

age = int(input())
next_age = age + 1
print("Next age =", next_age)

3. Rectangle Area

Read integer length and width, calculate the area and display it.

Sample input: 8, 5Expected output: Area = 40

💡 Convert both inputs with int(), then multiply them.

Official Python Program

length = int(input())
width = int(input())
area = length * width
print("Area =", area)

4. Shopping Bill

Read a decimal price and integer quantity, then display the total amount.

Sample input: 249.5, 2Expected output: Total = 499

💡 Use float() for price and int() for quantity.

Official Python Program

price = float(input())
quantity = int(input())
total = price * quantity
print("Total =", total)

5. Celsius to Fahrenheit

Read Celsius temperature, convert it and display the Fahrenheit value.

Sample input: 25Expected output: Fahrenheit = 77

💡 Use the formula celsius * 9 / 5 + 32.

Official Python Program

celsius = float(input())
fahrenheit = celsius * 9 / 5 + 32
print("Fahrenheit =", fahrenheit)

KEY TAKEAWAY

🎯 Give Every Value the Right Journey

1Read

Receive raw text using input().

→

2Convert

Choose int, float or another suitable type.

→

3Process

Calculate using clearly named variables.

→

4Present

Display a labelled result with print() or an f-string.

Correct programs depend on correct data representation. Before every operation, ask: “What value do I have, and what type does this operation require?”

INTERACTIVE LEARNING

🎬 Input, Conversion and Output — Visual Flow

Follow user data from the keyboard until Python displays the calculated result.

PROGRAM TRACING

🔎 Program Tracing — Student Input

Move through the program one statement at a time and observe input consumption, variable types, calculations and output.

INTERVIEW PREPARATION

🎤 Data Types & I/O — Interview Questions

Answer aloud before opening each explanation.

What is dynamic typing in Python?

What is the difference between int and float?

int represents whole numbers, while float represents floating-point numbers that can contain a fractional part.

Why must numeric keyboard input often be converted?

input() returns a string. Numeric calculations require a compatible numeric type such as int or float.

What is the difference between implicit and explicit conversion?

Implicit conversion is performed automatically by Python in compatible operations; explicit conversion is requested by the programmer using functions such as int() or float().

What does None represent?

None is a special singleton value representing no value or a value that has not yet been assigned meaningfully.

Why are f-strings useful?

EXTRA TIPS

💡 Data Types & I/O — Extra Tips

01
Name variables according to meaning: prefer total_marks over x.
02
Use type() while learning or debugging unexpected data behavior.
03
Convert input immediately when the rest of the program expects a number.
04
Use float() when valid input may contain a decimal point.
05
Keep input, processing and output as three clear stages in beginner programs.
06
Test conversions with normal, boundary and invalid values to understand failures.

EXTRA PRACTICE

✍️ Data Types & I/O — Extra Practice Questions

Create variables for a student's name, roll number, percentage and pass status; display their types.
Read two integers and display their sum, difference and product.
Read length and breadth as decimal values and display a rectangle's area and perimeter.
Read a name and department, then create a two-line profile using f-strings.
Convert the string "125" to an integer and add 25.
Predict the results of type("10"), type(10) and type(10.0).
Explain why input() + input() may join digits instead of adding numbers.
Correct the error in total = "Price: " + 499 using two different approaches.
Read minutes and convert them into hours and remaining minutes.
Build a bill program that reads item name, price and quantity and prints a formatted summary.

LEVEL 2 CHECKPOINT

Data Types & I/O Complete

When you can choose suitable types, convert input correctly and solve the five programs without help, mark this level complete and continue.

Continue to Level 3 →

📦 Data Types & I/O

By the End of This Level

Variables and Assignment

Create and Update Variables

Start Correctly

Use Valid Characters

Avoid Keywords

Choose Meaningful Names

Python Numeric Data Types

int

float

complex

bool

Strings, Boolean Values and None

🔤 String — str

🚦 Boolean — bool

⭕ None — NoneType

Check a Value with type()

Inspect Several Values

Keyboard Input with input()

Receive and Display a Name

Type Conversion

Calculate Using Converted Input

Formatted Output

Student Result Card

Common Data and Input Mistakes

📌 Data Types & I/O — Quick Revision

Level 2 Quick Quiz

🎯 5 Programming Problems — Data Types & I/O

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

Python Code Editor

Program Output

Test Case

🎯 Give Every Value the Right Journey

🎬 Input, Conversion and Output — Visual Flow

⌨️ How Python Processes User Input

1. User Enters Data

🔎 Program Tracing — Student Input

🎤 Data Types & I/O — Interview Questions

💡 Data Types & I/O — Extra Tips

✍️ Data Types & I/O — Extra Practice Questions

Data Types & I/O Complete

`int`

`float`

`complex`

`bool`

Strings, Boolean Values and `None`

🔤 String — `str`

🚦 Boolean — `bool`

⭕ None — `NoneType`

Check a Value with `type()`

Keyboard Input with `input()`