Backend and FastAPI on kodkod | Intro Course

Backend and HTTP: Who Does What, Methods and Status Codes

Mon, 01 Jan 0001 00:00:00 +0000

In this lesson

This lesson is built from two chapters, in the same order as the slides:

Chapter 1 — what a Backend is: Client, Server, Database, API and Endpoint
Chapter 2 — HTTP Methods and Status Codes

Chapter 1: What a Backend Is — Client, Server, Database, API and Endpoint

What will we learn?

Now we move from programs that run on our own computer to software that others talk to over the network. This lesson gives the big picture and the words:

FastAPI from Scratch: Installation, app = FastAPI(), a First Route and Running the Server

Mon, 01 Jan 0001 00:00:00 +0000

What will we learn?

This lesson is a full setup, from scratch, of a real server:

A virtual environment (venv): where libraries are installed.
Installing FastAPI with pip.
main.py: importing, creating app, and a first Route.
Running it with uvicorn.
Testing: the browser, curl, and the automatic documentation page /docs.

Why do we need this?

In the networking topic we saw what a “manual” server involves: bind, listen, accept, and decoding text. That is a lot of work, and it is easy to crash on bad input. FastAPI does all of this for us: it receives the request, decodes HTTP, finds the right function, converts the response to JSON, and checks types. We write only the logic.

Path Params, Query Parameters and Body

Mon, 01 Jan 0001 00:00:00 +0000

What will we learn?

A Client needs to tell the server what exactly it wants. It has three ways:

Way	Where	Example
Path Parameter	Part of the path itself	`/students/7`
Query Parameters	After `?` in the URL	`/students?city=Haifa&limit=10`
Body	In the body of the request (JSON)	`{"name": "Dana", "age": 24}`

Why do we need this?

In the next lesson we will write the first server, and in FastAPI each of the three is defined in a different way. If you don’t understand the difference, you put information in the wrong place: an identifier in the Body, or a password in the URL. And every real API you will consume (GitHub, weather, payments) uses all three.

FastAPI: Path Params, Query, Body and HTTPException

Mon, 01 Jan 0001 00:00:00 +0000

What will we learn?

In the previous lesson the functions received no input at all. Now they will receive the three kinds we learned:

Middleware: Code That Runs on Every Request

Mon, 01 Jan 0001 00:00:00 +0000

What will we learn?

Which problem there is when you want to do something on every request.
What Middleware is, and how it is related to the Decorator we already know.
@app.middleware("http"), call_next, async and await.
A log and time measurement for every request in the students API, and a Header that is added to every response.

Why do we need this?

The students API from the previous lesson works. Now we want to know what happens in it: which request arrived, which code came back, and how long it took. The first way that comes to mind — add a log line to every Route: