Programming · Grade 7 · Chapter 4
Data Types & Operators
Storing, categorizing, and performing operations on data in Python.
Chapter Goals
What We Will Master Today
- Variables: Store and update values in memory using snake_case names.
- Four Data Types: Master `str`, `int`, `float`, and `bool`.
- Operators: Calculate with arithmetic (`+`, `-`, `*`, `/`, `//`, `%`, `**`).
- Type Casting: Convert between data types using `int()`, `float()`, `str()`.
The Memory Box
How Does Python Remember Information?
In video games, your score increases, player health decreases, and high scores save automatically. Where do these numbers live?
Concept: A variable is a labeled memory container inside your computer's RAM.
Core Concept 1
Creating Variables (Assignment =)
In Python, we create a variable by giving it a name and assigning it a value using =.
player_name = "Alex" # String variable
score = 150 # Integer variable
health = 98.5 # Float variable
is_alive = True # Boolean variable
Rulebook
Python Variable Naming Rules
✓ Valid Names (snake_case)
player_score = 10
user_2 = "Maya"
_secret_key = "x99"
✗ Invalid Names (SyntaxError)
2nd_user = "Maya" (starts with number)
player score = 10 (contains space)
class = 7 (reserved keyword)
Core Concept 2
The 4 Core Data Types in Python
str
String
Text enclosed in quotes.
"Hello"
int
Integer
Whole numbers without decimals.
42, -7
float
Float
Decimal / floating-point numbers.
3.14, 0.5
bool
Boolean
Truth values.
True or False
Built-in Function
Checking Data Types with type()
print(type("Grade 7")) # Outputs: <class 'str'>
print(type(100)) # Outputs: <class 'int'>
print(type(9.99)) # Outputs: <class 'float'>
print(type(True)) # Outputs: <class 'bool'>
Core Concept 3
Python Arithmetic Operators
Standard Math
+ Addition (5 + 3 = 8)
- Subtraction (10 - 4 = 6)
* Multiplication (4 * 3 = 12)
/ Division (7 / 2 = 3.5)
Special Operators
// Floor Division (7 // 2 = 3)
% Modulo Remainder (7 % 2 = 1)
** Exponentiation (2 ** 3 = 8)
Deep Dive
Understanding Floor Division // and Modulo %
Imagine dividing 17 cookies equally among 5 friends:
17 // 5
= 3 cookies per friend (Whole quotient)17 % 5
= 2 cookies left over in jar (Remainder)
Modulo % 2 is frequently used in coding to check if a number is Even (0) or Odd (1)!
Math Sandbox
Predict the Output of These Operations!
a = 20 % 6 # What is 20 divided by 6 remainder?
b = 20 // 6 # What is whole part of 20 / 6?
c = 3 ** 3 # What is 3 to the power of 3?
print(a, b, c) # Output?
Core Concept 4
String Operations: Concatenation & Multiplication
# 1. Concatenation (+) joins strings together
first = "Super"
second = "Mario"
full_name = first + " " + second # Outputs: "Super Mario"
# 2. String Repetition (*) repeats text
banner = "=" * 10 # Outputs: "=========="
Trap Alert
"10" + "5" is NOT 15!
String Concatenation
print("10" + "5")
Output: "105" (Glued together)
Integer Math
print(10 + 5)
Output: 15 (Numeric addition)
Core Concept 5
Type Casting (Converting Data Types)
We use functions like int(), float(), and str() to change a value's data type.
age_text = "13" # str
age_num = int(age_text) # Converted to int 13
price = 19.99 # float
price_int = int(price) # Drops decimal -> 19
score = 100 # int
score_str = str(score) # Converted to str "100"
User Input
Casting User Input
The input() function ALWAYS returns data as a String. To do math, you must cast it!
# Asking user for age:
user_age = input("Enter your age: ") # returns "13" (str)
next_year = int(user_age) + 1 # 13 + 1 = 14
print("Next year you will be " + str(next_year))
Spot the Mistake
Can You Fix This TypeError?
# Broken script:
score = 100
print("Your total score is: " + score)
TypeError: can only concatenate str (not "int") to str
Fix: Wrap score inside str(score) so string addition works!
Smartboard Voting
Identify the Data Type!
Value 1
"3.14"
(Is it float or str?)
Value 2
5 == 5
(Is it int or bool?)
Value 3
10 / 2
(Is it int or float?)
Quick Check · Quiz 1
What is the result of 15 % 4 in Python?
A3.75
B3
C3 (Remainder)
D0
Click to reveal answer
Quick Check · Quiz 2
Which of the following is a valid variable name in Python?
A1st_score
Buser name
Ctotal_score_2
Dclass
Click to reveal answer
Quick Check · Quiz 3
What data type does division / ALWAYS produce in Python 3?
Click to reveal answer
Quick Check · Quiz 4
What will "Go!" * 3 produce in Python?
AError
B"Go!Go!Go!"
C"Go! 3"
D"Go!Go!"
Click to reveal answer
Guided Practice
Build a Shopping Receipt Calculator
item_price = 12.50
quantity = 4
subtotal = item_price * quantity
tax = subtotal * 0.10
total = subtotal + tax
print("Final Bill: $" + str(total))
Variable Flexibility
Variable Reassignment in Python
A variable can be updated to store a new value at any point in the program!
count = 1 # count is 1
count = count + 1 # count is now 2
count = "Done" # count is now a String "Done"
Summary & Takeaways
What We Learned in Chapter 4
- Variables store data using snake_case names without quotes.
- Python has 4 primary data types: `str`, `int`, `float`, and `bool`.
- Floor division `//` gives whole quotient; Modulo `%` gives remainder.
- Use `int()`, `float()`, and `str()` to cast between incompatible data types.
Exit Ticket
Data Type Matching Challenge
Write on your ticket:
1. Data type of "Grade 7"
2. Output of 19 // 5
3. Output of 19 % 5
Next Chapter: How AI Models Work!