Create a RESTful API with Python 3 and FastAPI

In this article, we'll create a simple RESTful API using Python 3 and FastAPI.

But whats is FastAPI?

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints.

First, lets go to import necessary modules and classes:

 pip3 install fastapi uvicorn 

Now the imports:

 from fastapi import FastAPI, HTTPException from pydantic import BaseModel from typing import Optional from uuid import UUID, uuid4 

• FastAPI from the fastapi package to create our web application.
• HTTPException to handle error responses.
• BaseModel from pydantic for data validation and settings management using Python type annotations.
• Optional from typing to denote optional fields.
• UUID and uuid4 for generating and working with universally unique identifiers.

Defining Data Models

We define a Pydantic model named Item to represent the data structure of an item in our API. This model includes fields for name, description, price, and on_offer, with description being optional and on_offer defaulting to False.

 class Item(BaseModel): name: str description: Optional[str] = None price: float on_offer: bool = False 

FastAPI app instance and in-memory data

 app = FastAPI() items = {} 

We create items = {} to save itens in memory to our test.

RESTful operations

Now Let's go to create our operations to save itens. To do this we'll create a RESTfull API with post, put, get and delete:

starting by post:

 @app.post("/items/", response_model=Item) async def create_item(item: Item): item_id = uuid4() items[item_id] = item return item 

This code will create a new Item with uuid to create a index.

Next, lets go to create two methods, one to list all itens and other to list by id:

 @app.get("/items/", response_model=dict) async def read_items(): return items @app.get("/items/{item_id}", response_model=Item) async def read_item(item_id: UUID): if item_id not in items: raise HTTPException(status_code=404, detail="Item not found") return items[item_id] 

Next step will be the Update and Delete methods:

 @app.put("/items/{item_id}", response_model=Item) async def update_item(item_id: UUID, item: Item): if item_id not in items: raise HTTPException(status_code=404, detail="Item not found") items[item_id] = item return item @app.delete("/items/{item_id}", response_model=Item) async def delete_item(item_id: UUID): if item_id not in items: raise HTTPException(status_code=404, detail="Item not found") return items.pop(item_id) 

And now let's go to test. To do this, at your terminal past this command below:

 uvicorn main:app --reload 

This command will create a server at port 8000.

Now to create a new Item we can use this curl below:

 import requests import json url = "localhost:8000/items" payload = json.dumps({ "name": "Example", "description": "This is an example description for the item.", "price": 10.99, "on_offer": False }) headers = { 'Content-Type': 'application/json' } response = requests.request("POST", url, headers=headers, data=payload) print(response.text) 

And open localhost:8000/docs and test your endpoints using swagger :)