FastAPI
Build production-ready APIs with FastAPI through hands-on challenges, one concept at a time.
FastAPI 0.139
Python 3.13Path Operations & Routing
Learn how FastAPI turns URLs into handlers: typing the values inside the path so conversion and rejection happen before your code runs, ordering fixed paths ahead of parameterized ones, constraining a segment to a fixed set of choices, and capturing a whole nested path in one parameter.
Typed Path Parameters
Route Order And Fixed Paths
Enum Constrained Categories
Storage Browser Routes
Query Parameters
Learn how FastAPI reads the values that arrive in the address bar: declaring them so they convert themselves, filling in the ones a caller leaves out, putting limits on what is allowed, collecting a parameter sent more than once, and binding a public name Python cannot spell.
Optional Search Filters
Constrained Query Rules
Repeated And Aliased Parameters
Catalog Search Contract
Request Body and Pydantic Models
Learn how FastAPI reads what a caller sends in the body: describing its shape as a model, giving optional parts sensible defaults, putting a rule on every field, refusing keys the model never declared, and nesting models inside each other so a mistake is reported at the exact place it happened.
Item Creation Model
Field Constrained Order
Nested Shipment Structure
Booking Request Payload
Response Models and Status Codes
Learn how FastAPI shapes what leaves your API: declaring a response model so internal values never escape, answering each outcome with the code it deserves, tuning how much of a record goes on the wire, and publishing the same contract in the generated description.