Core Data Types

In Plain English

Computers are very particular about what kind of data they handle. Text is a String (str), whole numbers are Integers (int), decimals are Floats (float), and true/false states are Booleans (bool). Python figures this out automatically when you type.

The Mental Model

"Imagine your backpack. Books are strings of text, whole coins in your pocket are integers, a receipt with $4.99 is a float with decimals, and whether your zipper is open or closed is a boolean (True or False). You treat each item according to its kind."

Deep Dive: How It Works

String (str): Text wrapped in quotes ("hello", 'world'). Strings can contain letters, numbers, spaces, and punctuation.

Integer (int): Whole numbers positive, negative, or zero (42, -7, 0) without any decimal points.

Float (float): Numbers that contain a fractional part with a decimal point (3.14159, 99.95, -0.5).

Boolean (bool): Exactly two values: True or False (capitalized in Python). Used for logic, checks, and switches.

You can inspect the type of any variable or value at runtime using the built-in type() function: type(42) returns <class 'int'>.

Syntax Blueprint

name = "Zen"     # str
count = 10        # int
price = 19.99     # float
is_active = True  # bool

Python automatically assigns the correct data type based on how the value is written.

Core Rules to Remember

String (str): Text in quotes, like "ZenCompiler" or "Pizza".

Integer (int): Whole counting numbers, like 42, 100, or -5.

Float (float): Numbers with decimals, like 3.14 or 99.99.

Boolean (bool): True or False. The bedrock of computer decisions.

Common Beginner Traps & How to Fix Them

Mistake:Putting quotes around numbers: age = "20"

Why it happens: Wrapping numbers in quotes turns them into text. "20" + "20" produces "2020", not 40.

How to fix: Leave numbers unquoted if you plan to do math with them.

Pro Tip: Use type(variable_name) whenever you are unsure what data type a variable holds.

Live Interactive Example

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Inspecting Data Types with type()

Python 3.12

Output Console

Click "Run Code" to view the rendered output.

How it works: The type() function reveals the underlying class that Python created for each value.

Your Turn: Micro Challenge

No pressure! Edit the starter code below and test your solution with instant feedback.

Micro Exercise

Check the data type of a variable

Create a variable called score with the integer value 100.
Use print(type(score)) to print its data type.

Sandbox Output

Click "Run & Check" to test your solution.

Finished reading and practicing?