FastAPI is a modern, fast web framework for building APIs with Python 3.6+ that is designed to be easy to use and performant. It is based on standard Python type hints for input and output validation and auto-generates interactive API documentation with the OpenAPI standard.
In this tutorial, we will go through how to create a simple web app using FastAPI.
Installation:
First, you will need to install FastAPI and Uvicorn, which is a lightning-fast ASGI server. You can do this using pip:
pip install fastapi uvicornCreating a FastAPI app:
To create a new FastAPI app, create a new Python file, for example app.py, and import FastAPI:
from fastapi import FastAPI
app = FastAPI()Defining routes:
You can define routes in FastAPI using Python functions. Routes are defined using decorators:
@app.get("/")
def read_root():
return {"message": "Hello, World!"}
@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = None):
return {"item_id": item_id, "q": q}Launching the app:
To run the FastAPI app, use the uvicorn command with the name of the file and the app name:
uvicorn app:app --reloadThis command will start the ASGI server and reload the app whenever a change is made, making development easier.
OpenAPI documentation:
By default, FastAPI provides an interactive OpenAPI documentation for your API. You can access it by going to http://localhost:8000/docs in your browser. This documentation is generated based on your route definitions and input/output types.
Input and output validation:
FastAPI uses Python type hints to automatically validate input and output data. For example, in the read_item function above, item_id is defined as an integer, so FastAPI will automatically validate that it is an integer type.
Static files and templates:
FastAPI also supports serving static files and templates through the StaticFiles and Jinja2Templates classes. You can use them to serve HTML files and other assets in your app.
Middleware:
FastAPI also supports the use of middleware, which allows you to modify the request and response objects before and after they are processed by your routes. Middleware can be used for things like authentication, logging, and error handling.
Conclusion:
FastAPI is a powerful and easy-to-use web framework for building APIs with Python. It provides features like automatic input/output validation, interactive API documentation, and support for middleware and templates. I hope this tutorial has given you a good introduction to FastAPI and how to build web apps with it.
