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Shariq Ahmed
Shariq Ahmed

Posted on • Originally published at Medium

What’s the Difference Between Flask and FastAPI?

There are many microframeworks in Python, including Django, Flask, Bottle, and Flask. But two are the most popular now: Flask and FastAPI.

Now, the second question that may pop up in your mind is, what is the difference between the two? Well, there are certain similarities between the two since both are microframeworks. However, there is a stark difference between them. Let’s discuss the difference between them.

1. Speed

If you prefer speed in your apps, then go for FastAPI. This is because FastAPI handles more requests per second. If you made a high-load application that benefits from asynchronous I/O operations, FastAPI should be your preferred choice. On the contrary, you can use Flask when your app doesn’t need to handle many concurrent connections. Instead, you like simplicity and easiness.

2. Asynchronous Tasks

FastAPI can handle asynchronous tasks because it is built with async/await syntax. This means that FastAPI can handle large volumes of concurrent connections, which is what makes it best for web apps that depend on real-time data and high-performance APIs. Flask does support asynchronous tasks, but it uses Flask-AsyncIO, which isn’t made to work best with async programming. Due to this, better performance in I/O-bound needs more work.

3. Beginner-Friendly

Flask is beginner-friendly. Moreover, you may not get stuck on complex issues because of the huge community support. You can also say it’s a backend and front-end solution packed into one. Now, FastAPI is also easy. It is also good when it comes to building API. But it is new compared to Flask. This means that its community isn’t that extensive.

4. Display of Error Messages

FastAPI uses pydantic models. This means that detailed and developer-friendly error messages are automatically created. On the other hand, Flask relies on customer error handlers.

5. Parameters and Data Validation

In Flask, parameters are passed through URLs and forms. Result? Support of basic data validation. Unfortunately, it doesn’t provide built-in validation. You have to rely on external libraries. On the other hand, FastAPI is better here because of its use of Pydantic models. This makes use of Python-type annotations when it comes to request and response data validation.

All in all, you need to choose only the framework that fulfils your needs. If you want your web app to automatically display error messages, support asynchronous programming, perform better, and contain well-structured documentation, then use FastAPI. But if you prefer a simple micro-framework with extensive community support that is simple, supports asynchronous tasks, and relies on custom error handlers, then use Flask.

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