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 :)

Blog

Create a RESTful API with Python 3 and FastAPI

Thiago da Silva Adriano

Defining Data Models

FastAPI app instance and in-memory data

RESTful operations

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