Programming · Grade 10 · Chapter 6

Data Types & Operators

Why Python cares whether something is a number or text — and how operators behave differently depending on type.

Learning objectives

What We'll Cover

Understand Python's four core data types: int, float, str, bool
Use arithmetic, comparison, and logical operators correctly
Convert between data types with type casting
Use type() to inspect what type a value is
Identify and fix TypeError bugs
Understand operator precedence (order of operations)

The bug

"5" + 3 = ???

A student writes a program to add two numbers entered by the user. They input 5 and 3. The result is "53". What happened?

Think first: input() always returns a string — even if the user typed a number. So Python added "5" + "3" = "53" (string concatenation), not 5 + 3 = 8.

The four types

Python's Core Data Types

Type	Meaning	Example	type() returns
int	Whole numbers	42, -7, 0	<class 'int'>
float	Decimal numbers	3.14, -0.5, 1.0	<class 'float'>
str	Text (characters)	"hello", "123"	<class 'str'>
bool	True or False only	True, False	<class 'bool'>

Inspecting types

The type() Function

Use type() to check what data type a value or variable is at runtime.

      print(type(42))       # <class 'int'>

      print(type(3.14))     # <class 'float'>

      print(type("hello"))  # <class 'str'>

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

      x = input("Enter: ")

      print(type(x))       # Always <class 'str'>

Quick check · 1

What type does this expression produce? 7 / 2

Aint (3)

Bfloat (3.5)

Cstr ("3.5")

DTypeError

Click to reveal answer

Note: In Python 3, / always produces a float. Use // for integer (floor) division.

Arithmetic operators

The Arithmetic Operators

Operator	Meaning	Example	Result
+	Addition	10 + 3	13
-	Subtraction	10 - 3	7
*	Multiplication	10 * 3	30
/	Division (float)	10 / 3	3.333...
//	Floor division	10 // 3	3
%	Modulo (remainder)	10 % 3	1
**	Exponentiation	2 ** 8	256

Predict the output

What Does Each Print?

Class challenge — predict before running:

      print(17 % 5)     # ?

      print(17 // 5)    # ?

      print(2 ** 10)    # ?

      print(9 / 3)      # ?

      print(9 // 3)     # ?

Answers: 2, 3, 1024, 3.0, 3

Type casting

Converting Between Types

Use built-in functions to convert values between types. This is essential when working with input().

      # String → Integer

      age = int(input("Age: "))

      # String → Float

      price = float(input("Price: "))

      # Integer → String (for concatenation)

      msg = "Score: " + str(score)

      # Float → Integer (truncates decimal)

      whole = int(3.99)  # = 3, not 4

Quick check · 2

What does int(3.99) return in Python?

A4 (rounds up)

B3 (truncates towards zero)

C3.99 unchanged

DError

Click to reveal answer

Comparison operators

Comparison Operators — Always Return bool

Operator	Meaning	Example	Result
==	Equal to	5 == 5	True
!=	Not equal	5 != 3	True
>	Greater than	10 > 7	True
<	Less than	3 < 1	False
>=	Greater or equal	5 >= 5	True
<=	Less or equal	4 <= 3	False

Common mistake: Using = (assignment) instead of == (equality check) inside a condition.

Logical operators

Logical Operators: and, or, not

      x = 10

      # and: both must be True

      print(x > 5 and x < 20)  # True

      # or: at least one must be True

      print(x < 5 or x == 10)  # True

      # not: reverses the boolean

      print(not x > 5)          # False

Predict the output

True or False?

The class votes thumbs up (True) or down (False) before revealing:

      print(10 > 5 and 3 == 4)  # ?

      print(10 > 5 or 3 == 4)   # ?

      print(not (5 == 5))        # ?

      print(True and False)       # ?

Answers: False, True, False, False

Operator precedence

Order of Operations (PEMDAS in Python)

Python evaluates operators in a specific order. Same as mathematics — with some additions:

1st: () Parentheses
2nd: ** Exponentiation
3rd: * / // % Multiplication/Division
4th: + - Addition/Subtraction
5th: == != > < >= <= Comparisons
6th: not, then and, then or

Rule: When in doubt, use parentheses to make your intent explicit.

Quick check · 3

What does 3 + 4 * 2 evaluate to in Python?

A14 (left to right)

B11 (* evaluated before +)

CError

D24

Click to reveal answer

String type behaviour

How Operators Behave on Strings

String + String = Concatenation

"Hello" + " World"
→ "Hello World"

"ha" * 3
→ "hahaha"

❌ String + Number = TypeError

"Score: " + 5
TypeError: can only concatenate str (not "int") to str

Fix: "Score: " + str(5)
or: f"Score: {5}"

Debugging activity

Fix the Type Errors

Find and fix the bug in each snippet:

      # Bug 1

      years = input("Years: ")

      print("Months: " + years * 12)

      # Bug 2

      price = 29.99

      print("Price is: " + price)

      # Bug 3

      a = "5"

      b = "3"

      print(a + b)  # Expects 8, gets "53"

Fixes: 1) int(years)*12 2) str(price) or f-string 3) int(a)+int(b)

Quick check · 4

Which type would the expression 5 == 5.0 produce?

Aint

Bfloat

Cbool (True)

DTypeError

Click to reveal answer

Note: Python compares int and float values — 5 == 5.0 is True. Both are numerically equal.

Booleans in depth

Everything Has a Boolean Value

In Python, any value can be evaluated as True or False. This is called truthiness.

Truthy values

Any non-zero number: 1, -1, 3.14
Any non-empty string: "hello"
Any non-empty list: [1,2,3]

Falsy values

Zero: 0, 0.0
Empty string: ""
None
Empty list: []

bool(0) → False | bool(42) → True | bool("") → False | bool("hi") → True

Guided practice

Grade Calculator

Live-code a program that asks for a score (0–100) and prints the percentage rounded to 1 decimal place.

      score = int(input("Score (0-100): "))

      total = 100

      percentage = (score / total) * 100

      print(f"Your score: {score}/{total}")

      print(f"Percentage: {percentage:.1f}%")

Note: :.1f inside an f-string formats a float to 1 decimal place.

Quick check · 5

What is 10 % 3 in Python?

A3

B1

C3.33

D0

Click to reveal answer

Modulo returns the remainder: 10 = 3×3 + 1, so 10 % 3 = 1. Used heavily in programming for cycling, checking even/odd, etc.

Real-world application

Why Data Types Matter in Real Systems

Banking

Financial calculations must use the right types. "50" - 30 crashes the transfer system. Type validation is a security requirement.

AI Models

Neural networks operate on float tensors. Feeding string data without conversion causes the entire training pipeline to fail.

Games

Score, health, and coordinates must be numbers. A string score breaks comparison logic and leaderboard sorting.

Web Forms

Web applications must validate and cast all user input — form fields return strings, but databases may expect integers or booleans.

Challenge

Build a Temperature Converter

Write a program to convert between Celsius and Fahrenheit.

      celsius = float(input("Enter temperature in °C: "))

      fahrenheit = (celsius * 9 / 5) + 32

      print(f"{celsius}°C = {fahrenheit:.1f}°F")

Extension: Add the reverse converter. Stretch: Ask the user which direction to convert and handle both cases.

Quick check · 6

What is the output of: print("ha" * 3)?

AError

Bhahaha

Cha3

D3ha

Click to reveal answer

Exit ticket

Reflection: The Type System

Think about everything we covered today about data types and operators.

Discuss or write: Why do you think Python requires explicit type conversion instead of just automatically figuring it out? What problems could arise if Python silently converted types for you?

Before you go

Today We Learned...

Python has 4 core types: int, float, str, bool
Operators behave differently depending on the type (+ adds numbers, concatenates strings)
Always convert input() values with int() or float() when you need a number
Comparison operators return bool; logical operators combine booleans
Operator precedence follows PEMDAS — use parentheses when unsure

Next chapter: Conditionals — using these comparison operators to make Python make decisions.