Comparing FastAPI and Flask: An In-Depth Tutorial

FastAPI is a modern web framework for building APIs with Python, based on standard Python type hints. FastAPI is becoming increasingly popular due to its speed, ease of use, and built-in support for modern Python features like type hinting and async/await syntax.

In this tutorial, we will compare FastAPI with Flask, another popular web framework for Python, and show you how to get started with FastAPI.

FastAPI vs Flask

Both FastAPI and Flask are popular web frameworks for building APIs with Python. However, there are some key differences between the two that you should be aware of before choosing which one to use for your project.

• Performance: FastAPI is built on top of Starlette, a high-performance ASGI framework, and uses Pydantic for data validation. This makes FastAPI faster than Flask, especially for data-intensive applications. FastAPI also supports asynchronous programming with async/await syntax, which can further improve performance.

• Type hints: FastAPI uses standard Python type hints to define request and response data structures, which are then validated and automatically converted to and from JSON. This makes it easier to write type-safe code and catch bugs at compile-time. Flask, on the other hand, relies on decorators for request handling, which can be less intuitive and error-prone.

• Automatic documentation: FastAPI automatically generates API documentation based on type hints and docstrings, using tools like Swagger UI and ReDoc. This can be very helpful for API users to understand how to interact with your API. Flask also supports documentation generation, but it requires additional setup and configuration.

• Middleware and plugins: FastAPI has built-in support for middleware, which allows you to add custom processing logic to your API requests and responses. Flask also supports middleware, but FastAPI’s middleware system is more powerful and easier to use. FastAPI also has a plugin system for adding additional functionality to your API easily.

Getting started with FastAPI

To get started with FastAPI, you first need to install it using pip:

pip install fastapi

You will also need to install an ASGI server like uvicorn to run your FastAPI application:

pip install uvicorn

Next, create a new Python file with the following code to define a simple FastAPI application:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

This code creates a new FastAPI application with a single route ("/") that returns a JSON response with the message "Hello, World".

You can run your FastAPI application using uvicorn:

uvicorn app:app --reload

This command starts the uvicorn server and reloads your FastAPI application whenever you make changes to your code.

You can now access your FastAPI application in a web browser or using tools like curl or Postman. Try accessing http://localhost:8000/ in your browser to see the "Hello, World" message.

That’s it! You have now created a simple API using FastAPI. You can now add more routes, request validation, authentication, and other features to your API to build a full-featured application.

In conclusion, FastAPI is a modern web framework for building APIs with Python that offers superior performance, type safety, automatic documentation, and middleware support compared to Flask. If you are starting a new project or looking to switch to a faster and more modern framework, give FastAPI a try!