Basic hints

Learn basic type hints like int, str, list.

Basic hints

Type hints add type information to variables, parameters and return values. Python does not enforce them; tools (mypy, IDEs) check them.

Basic types: int, str, float, bool. You write count: int = 0 for a variable; for a function you write def add(a: int, b: int) -> int:.

def add(a: int, b: int) -> int:
    return a + b

name: str = "Ayşe"
count: int = 0

The arrow -> marks the return type. Hints do not change runtime behavior; they improve readability and tooling.

Reading hinted functions

A hinted function signature tells you what type it expects and what it returns. This helps when reading code and using IDE completion.

Example: def greet(name: str) -> str: takes a string and returns a string. def is_even(n: int) -> bool: takes an integer and returns true or false.

If you pass the wrong type, Python still runs; a hint is only a declaration. But tools like mypy catch the error.

Exercise Write a hinted add function

Define a function add(a: int, b: int) -> int. The body contains return a + b. Call print(add(3, 4)).

Show example solution

def add(a: int, b: int) -> int:
    return a + b

print(add(3, 4))

Test yourself

When are type hints enforced by Python?
- Only during import
- On every function call
- Never at runtime; only tools check them
- Only when an error occurs
Show answer

Never at runtime; only tools check them — Hints are inert at runtime; mypy or an IDE checks them.

Add the return type

def add(a: int, b: int) ____ int:
    return a + b

Show answer

def add(a: int, b: int) -> int:
    return a + b

Match the type and meaning

int

Integer
str

String
float

Decimal number
bool

True/false

Next lesson: Optional and Union

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