Variable & Function Hints

Variable type hints

TypeScript:

let name: string = 'John';
let age: number = 25;
let price: number = 99.99;
let active: boolean = true;

Python:

name: str = "John"
age: int = 25
price: float = 99.99
active: bool = True

Same idea as TypeScript — name: type. You saw these exact four types back in Phase 1 without the annotation; now you're just labeling them explicitly.

You can also annotate a variable without giving it a value yet — this is common in places like class bodies (Phase 4) and data models, where you're describing a shape rather than assigning something right away:

name: str
age: int

Function hints — a recap

Phase 3 already covered this, so this is just a reminder of the shape, now that you've seen the plain-variable version too:

def get_user(user_id: int) -> dict:
    ...

function getUser(userId: number): object {
  // ...
}

user_id: int is a parameter hint (same as a variable hint), and -> dict is the return type — exactly like the return type after : in TypeScript.

As a reminder from Phase 3: none of this is enforced by Python itself. It's the frameworks you build with — FastAPI especially — that actually read these hints and act on them.