{"id":492,"date":"2025-04-06T14:21:29","date_gmt":"2025-04-06T12:21:29","guid":{"rendered":"https:\/\/pythonium.net\/?p=492"},"modified":"2025-04-06T14:21:03","modified_gmt":"2025-04-06T12:21:03","slug":"fastapi","status":"publish","type":"post","link":"https:\/\/pythonium.net\/blog\/fastapi","title":{"rendered":"Build a REST API with FastAPI"},"content":{"rendered":"\n

Let he who has never coded an API cast the first stone. Indeed, APIs have been everywhere for quite a few years. In this tutorial, we will explore the basic concepts of FastAPI and how to use it to quickly create REST APIs.<\/p>\n\n\n\n

By the end of this tutorial, you will be able to create production-ready<\/s> APIs (getting a bit ahead of myself here...) and will have the necessary knowledge to dive deeper into your specific use cases (But later on, AI can assist you).<\/p>\n\n\n\n

FastAPI: What is it?<\/h2>\n\n\n\n

FastAPI is a modern, fast, and high-performance framework for building APIs in Python, based on standard Python type annotations.<\/p>\n\n\n\n

Basically, when you want to build an API in Python, there's a good chance you'll use FastAPI (Well, there are alternatives: Flask, Django Rest Framework, Tornado, ...).<\/p>\n\n\n\n

FastAPI offers high performance, comparable to NodeJS and Go. It speeds up development, reduces human errors, and provides great editor support with auto-completion, minimizing debugging time. The framework is easy to learn, reduces code duplication, and ensures production-ready code with automatic interactive documentation. Based on open standards like OpenAPI and JSON Schema, FastAPI simplifies the process of building robust and efficient APIs.<\/p>\n\n\n\n

Install FastAPI<\/h2>\n\n\n\n

Like any Python project, it's best to start by creating a virtual environment (optional), and then install FastAPI<\/p>\n\n\n\n

$ python -m pip install fastapi[standard] uvicorn[standard]<\/code><\/pre>\n\n\n\n
Your first API: Just the basics<\/h2>\n\n\n\n
In this tutorial, we\u2019ll see how to create a simple \"products\" API and cover the basics of retrieving and updating products. This is a fake API \u2014 we won\u2019t be handling data persistence, as that\u2019s beyond the scope of this FastAPI introduction.<\/p>\n\n\n\n
FastAPI is very intuitive: it provides a decorator for each HTTP method. Here\u2019s a summary table:<\/p>\n\n\n\n
HTTP method<\/th>FastAPI Decorator <\/th><\/tr><\/thead>
GET<\/td>@app.get()<\/code><\/td><\/tr>
POST<\/td>@app.post()<\/code><\/td><\/tr>
PUT<\/td>@app.put()<\/code><\/td><\/tr>
DELETE<\/td>@app.delete()<\/code><\/td><\/tr>
PATCH<\/td>@app.patch()<\/code><\/td><\/tr>
OPTIONS<\/td>@app.options()<\/code><\/td><\/tr>
TRACE<\/td>@app.trace()<\/code><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Get<\/a><\/h3>\n\n\n\n
Create a file main.py<\/code> with the following basic FastAPI content:<\/p>\n\n\n\n
from typing import Union\nfrom fastapi import FastAPI\n\napp = FastAPI()\n\n@app.get(\"\/\")\ndef read_root():\n    return {\"msg\": \"Hello !\"}<\/code><\/pre>\n\n\n\n
Run it<\/strong><\/p>\n\n\n\n
fastapi dev main.py<\/code><\/pre>\n\n\n\n
Open your browser at\u00a0http:\/\/127.0.0.1:8000<\/a><\/p>\n\n\n\n
{\"msg\":\"Hello !\"}<\/code><\/pre>\n\n\n\n
And there you go, your API is now available and already returns a JSON object. For now, it doesn't do much \u2014 but we\u2019re about to start building our products API:<\/p>\n\n\n\n
from typing import Union\nfrom fastapi import FastAPI\n\napp = FastAPI()\n\n@app.get(\"\/\")\ndef read_root():\n    return {\"msg\": \"Hello !\"}\n\n@app.get(\"\/products\/{product_id}\")\ndef read_product(product_id: int, name: Union[str, None] = None):\n    return {\"id\": product_id, \"name\": name}\n\n<\/code><\/pre>\n\n\n\n
Here's a bit of explanation:<\/p>\n\n\n\n