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FastAPI Part 1: Introduction to FastAPI

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1. The Power of APIs

In today’s digital age, APIs (Application Programming Interfaces) are more than a technical asset—they are the very infrastructure that supports the seamless integration and function of different software systems. APIs enable a myriad of services that make modern conveniences possible. From booking flights and managing bank transactions online to social media interactions and even enabling smart home devices to communicate, APIs provide the essential linkage between disparate systems, facilitating efficient and secure data exchange.

APIs operate as intermediaries that allow software applications to communicate with each other. They define the methods and data formats that applications can use to communicate. This function is crucial because it allows developers to build complex software systems where components can rely on each other's data without needing to understand every detail of their internal workings.

2. What is FastAPI?

FastAPI is a cutting-edge, high-performance web framework designed specifically for building APIs for Python 3.6 and above. What sets FastAPI apart is its speed and ease of use, enabling developers to quickly write code that’s not only fast but also robust and scalable. FastAPI leverages modern Python features such as asynchronous programming and type hints. Asynchronous programming helps handle more requests simultaneously, making it highly scalable, while type hints ensure that the code is more readable and less prone to bugs.

This framework comes with automatic interactive API documentation, validation, and serialization out of the box, meaning developers can concentrate on writing business logic rather than boilerplate code. Previous frameworks heavily inspired its design and added the best modern features, making it an excellent choice for modern web applications.

3. The Perks of FastAPI

FastAPI is built on the ASGI specification instead of the traditional WSGI, which underpins other frameworks like Flask and Django. ASGI supports asynchronous request handling, which means FastAPI can efficiently manage asynchronous tasks and real-time WebSocket connections. This capability allows it to perform comparably to high-performance frameworks in other languages like Node.js and Go, handling thousands of requests per second.

Another highlight is the integration of Pydantic for data validation. This provides powerful, flexible, and extensible data validation and parsing using Python type annotations. This ensures that all incoming data conforms to your code's expected formats and types, significantly reducing bugs and the overhead associated with manual data handling.

FastAPI's automatic documentation with Swagger UI and ReDoc offers a detailed, interactive, and up-to-date schema of your API's capabilities. This not only aids in development but also in ensuring that all stakeholders, from developers to end-users, can understand and interact with your API’s functionalities without digging through the source code.

4. Comparing FastAPI with Flask and Django

Flask: A lightweight, extendable micro-framework with numerous plugins. Flask provides a simple base for web development and is particularly well-suited for small to medium applications that require customizability over convention.

Django: A full-featured framework that includes almost everything a developer needs out of the box (hence often referred to as "batteries included"). Django is ideal for developers who want to implement detailed database-driven websites and comes packed with extras like a built-in admin panel and options for handling forms, authentication, and more.

FastAPI's Niche: FastAPI excels in scenarios where performance, data integrity, and developer efficiency are key. Its modern architecture makes it ideal for real-time applications that require high performance, such as IoT devices, real-time data processing services, and more. It is particularly advantageous for projects where robust API functionality needs to be developed quickly and be easily maintained.

5. Setting Up Your FastAPI Environment

Getting started with FastAPI is straightforward. First, install the necessary packages using pip:

pip install fastapi uvicorn
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Then, create your first API endpoint:

from fastapi import FastAPI

app = FastAPI()

async def root():
    return {"message": "Hello, World!"}
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Here, FastAPI() creates an instance of the FastAPI class, @app.get("/") defines a route that listens for HTTP GET requests to the root URL, and the function returns a JSON response.

6. Running Your API Locally

To run your application, you'll use Uvicorn, a lightning-fast ASGI server. Execute the following command:

uvicorn main:app --reload
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The --reload option restarts the server after code changes, which is very useful during development. Now, open your browser and navigate to You should see the greeting "Hello, World!" displayed.

Forward Look

In the upcoming posts, we will explore some of the advanced features of FastAPI. This will include routing, security, dependency injection, and handling of complex data structures. You can just stick around to learn how you can make your applications even more efficient and powerful.

FastAPI Part 2: Routing, Path Parameters, and Query Parameters

FastAPI Part 3: Pydantic Data Models

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Top comments (3)

behainguyen profile image
Be Hai Nguyen

Great introduction to FastAPI. I have looked at Flask, Django, but not yet FastAPI.

With Flask, we can integrate it with Swagger UI, too. But it requires some works.

jamesbmour profile image

I've never used Swagger UI with Flask, but in FastAPI, it saves me a lot of time. Are you using Flask just as an API or as a web framework?

behainguyen profile image
Be Hai Nguyen

I have used Flask for both. I played with Swagger UI for learning purpose, not any real project yet.

One of my project with Flask, this is an API one, ( I have stopped hosting it on though ):