The BlogFlask vs FastAPI: A Detailed Comparison GuidePosted on October 14, 2024October 14, 2024

The selection of an appropriate framework is crucial when it comes to web development. Flask and FastAPI are two of the leading Python rivals, each delivering their own set of features.

Understanding how Flask and FastAPI differ might help you choose the right tool for your project, regardless of whether you’re working on a straightforward website or a sophisticated API.

This article will discuss the differences between Flask and FastAPI. Regardless of your experience level as a developer, this guide will assist you in selecting the framework that best meets your requirements.

What is Flask?

Flask is a microweb framework that allows easy creation of lightweight web apps.

It is also known as a micro web framework since it does not require any specific tools or libraries and attempts to keep the core simple yet protractible. It merely offers the components required for development, like request handling and routing.

Additionally, Flask is a terrific application for novices because it is straightforward to get started with. It is suitable for both simple and complicated applications.

The Flask framework enables Flask developers to create websites, FastAPI e-commerce stores, and other applications. Additionally, it helps deploy machine learning models quickly and easily. Prominent businesses like Netflix, Reddit, and Mozilla use it.

Key Features

• Lightweight: Flask is an excellent choice for beginners to create complex applications effortlessly because it is a lightweight framework that does not require external libraries.

• Jinja2 Templating Engine: Flask includes Jinja2, which is a fast, expressive, extensible templating engine, as its templating support.

• WSGI compliant: Flask is a WSGI (Web Server Gateway Interface) application. It translates incoming HTTP requests into a WSGI environment and turns a WGSI response into an HTTP response.

• Modular: Flask offers an organized approach to developing apps by segmenting applications into manageable modules.

What is FastAPI?

Flask is one of the most well-known Python frameworks for building REST services and has been around for a long time. Although it works well for creating microservices and is simple to use and deploy, Flask has some drawbacks. That’s why the FastAPI framework was built to make up for them.

FastAPI is a state-of-the-art, high-performance web framework designed for Python 3.6+ API development. It has excellent performance that is comparable to GO and NodeJS. Reputable businesses like Netflix and Uber use it to develop their apps.

To begin utilizing FastAPI, install FastAPI and Uvicorn with pip. Uvicorn is a production-purpose Asynchronous Server Gateway Interface (ASGI) server.

One benefit of using FastAPI is that it can process requests asynchronously. When declaring endpoints, all you have to do is place the async keyword before a function. 

Key Features

• Built-in Security: Fast API incorporates security mechanisms via features like user input sanitization and validation.

• Scalability: It is one of the few Python frameworks that can help you construct scalable apps.

• Automatic Data Validation: Compared to conventional validation, FastAPI’s automatic data validation mechanism is substantially faster and guarantees that the data is up to date.

• High Performance: The performance of the modern framework, FastAPI, is comparable to that of NodeJS and Go. 

Is Flask the foundation of FastAPI?

FastAPI is built using Flask. It is a Python library that allows you to construct web applications conveniently using HTML/CSS or Python. FastAPI lacks a built-in development server, unlike Flask, so an ASGI server akin to Daphne or Uvicorn is utilized when necessary. The speed of FastAPI is mainly due to ASGI, the server on which it was built, and its support for asynchronous code.

WSGI and ASGI

WSGI, introduced in 1999, is a Python standard designed primarily for web applications and servers to interface with one another. It can occasionally be challenging for inexperienced programmers to get started using Python. However, those with experience with Ruby or PHP will find it easier to understand.

The creators of FastAPI introduced ASGI. It is a specification for creating asynchronous, event-driven web applications. It includes an API framework, meaning you can use any framework to develop an application. 

FastAPI and ASGI are equivalent in the following respects.

• They enable you to have readily usable tools and libraries.
• They let you write any asynchronous, event-driven code.

Flask vs. FastAPI: Comparison

Flask and FastAPI are Python web frameworks that allow you to create online apps and APIs. Nonetheless, the two frameworks differ in a few significant ways.

HTTP Methods

Flask

The micro framework Flask supports all HTTP methods, including GET, POST, PUT, DELETE, and so forth. With decorators, you can use HTTP methods in Flask, making route handling simple. Here’s how to use Flask’s GET and POST methods.

@app.route(“/”, methods = [“GET”])

@app.route(“/”, methods = [“POST”])

FastAPI

FastAPI includes more modern Python capabilities like type hints and asynchronous support. With this asynchronous support, I/O-bound activities and asynchronous operations become easy to manage. Here’s how to use the GET and POST methods in FastAPI. 

@app.get(“/”)

@app.post(“/”)

Data Validation

Flask

There is no built-in data validation support in Flask. The program will crash if you attempt to pass an incorrect input type instead of the intended input type. Developers can utilize external libraries to validate data.

FastAPI

On the other hand, FastAPI has built-in automated data validation. FastAPI accomplishes this because it is integrated with Pydantic models. These models make use of Python annotations to validate API requests and responses.

Error Message Display

Flask

Flask displays bespoke error messages using custom error handlers defined by developers. Flask uses HTML pages by default to give error messages.

FastAPI 

Using Pydantic models, FastAPI automatically provides comprehensive and straightforward error messages. FastAPI shows error messages in JSON format by default.

Asynchronous Tasks

Flask

Flask does not handle asynchronous tasks; instead, it uses external resources. The likelihood of achieving high performance with asynchronous tasks becomes challenging due to its non-inherent design for asynchronous programming.

FastAPI 

FastAPI ASGI allows asynchronous tasks. FastAPI’s asynchronous programming approach makes it perfect for real-time applications since it can manage high volumes of concurrent requests.

Performance

Flask

The Asyncio library can be beneficial for operations that need waiting, such as retrieving data from APIs, querying a database, and reading the contents of a file. As previously indicated, Flask is limited in a WSGI application, whereas FastAPI implements ASGI standards.

FastAPI

FastAPI fulfills its promises. If you’ve used languages like NodeJS or Go before, you’ll notice that its performance is comparable. FastAPI employs the asyncio library, enabling Python developers to write concurrent code.

Documentation Support

Flask

Flask supports manual documentation. One has to use external tools to automate the Flask application’s documentation process.

FastAPI 

FastAPI includes built-in automatic documentation support. It assists in providing a user interface for testing your service. Use API’s endpoint to be tested with /docs to access this automatically created documentation.

Community Support

Flask

Despite being an older framework, Flask has a strong community. Numerous resources are available, including third-party plugins, extensions, tutorials, and guidelines.

FastAPI

FastAPI is a relatively new framework with a small but growing community due to its excellent features and performance.

Pros & Cons of Flask and FastAPI

Evaluating the advantages and disadvantages of Flask and FastAPI is crucial. It will assist in analyzing the Flask vs. FastAPI performance benchmark so you can choose the most suitable for you.

Pros of Flask

• Easy to Learn: Projects needing sophisticated functionality should consider Flask because of its ease of learning curve and abundance of third-party libraries. It also requires a small, easy-to-understand codebase. Flask is simple to understand, and its syntax is straightforward, making it an excellent choice for beginners.
• Built-in Development Server & Unit Testing: A development environment differs vastly from a production environment. Stimulating your application’s production environment before it is pushed to production is crucial to avoid issues and problems. Flask allows you to test your application before deploying it into production. It provides unit testing, which may help simulate different scenarios and test your application’s operation to verify code readability and efficiency.
• Ensures no Global Variables in an  Application: Since Flask assigns a namespace to each request, it will ensure that your application does not contain any global variables. It aids in maintaining track of where objects belong. Additionally, it facilitates debugging and helps find what one needs when creating code.
• Many Third-Party Libraries: There are no limitations to how you can use Flask. Although you can use the list of tools it provides to meet all your needs, you are free to perform tasks other than those listed.
• Scalability: You can quickly and effectively scale your application with Flask. Developers can effortlessly add functionality on the go.

Cons of Flask

• Complex Framework: The Flask framework is more complicated than FastAPI. Individuals who lack the time or expertise to study it may encounter difficulties carrying out specific tasks. It also applies to those who have never dealt with Python before.
• Not Very Well-Documented: Flask is not as well documented as FastAPI. There aren’t many guides that go over every feature in detail. That’s a problem because new features, such as private methods, provide you more control over your application with each version.
• Not as Quick as FastAPI: The Flask framework is not as fast. For small websites that don’t need to load quickly, this makes it a good option; nevertheless, it isn’t the best option for projects that require speed. 
• Single-Threaded and Synchronous: In the single-threaded Flask framework, a process can begin only after the conclusion of its predecessor. It is also known as the application’s synchronous behavior.
• Session Management: Since Flask lacks an integrated session management system, it is up to the developer to connect the requests and answers of a user’s interaction with your application. 

Pros of FastAPI

• Designed to Build API Conveniently: FastAPI emphasizes dependability, security, and simplicity. Its purpose is to quickly and easily create APIs. Even people who are not programmers can use it because it requires no programming skills.
• Feature-Rich: Many capabilities are available with FastAPI, such as SSL/TLS encryption, XML/JSON responses, OAuth authentication, HTTP requests, and more. It is handled via a web interface, which allows you to tailor your account settings to the API’s behavior.
• Built-In Monitoring Tools: You can use the built-in monitoring tools to keep track of API usage. It sends notifications when you reach significant thresholds, such as response timestamp expiration and request count limits.
• Additional Functionality Aside From Flask’s Features: The FastAPI framework is used to create Flask-based APIs. It is a web application framework extension that offers more capabilities besides things you would expect from Flask.
• Easy to Learn: FastAPI can be helpful when adopting a toolkit-based approach instead of starting from scratch or using numerous boilerplate generators online. It takes concepts from different libraries. It implies that learning and adjusting to the FastAPI framework will be simple if you are already familiar with other relevant libraries or frameworks.
• Dependency Injection: FastAPI ensures that classes are not interconnected and includes a built-in solution for dependency injection. It increases your application’s modularity and efficiency and facilitates conflict-free application modification.

Cons of Fast API

• Expensive: The primary drawback of the FastAPI framework is its high cost. It varies depending on the country you use it in and the number of API calls you make monthly. However, it is expensive overall.
• Difficult to Scale: Scaling your project can be challenging. You will encounter difficulties scaling to a larger project if your code utilizes MySQL or PostgreSQL or is written in PHP. While using FastAPI with Python makes things more convenient, it is not the recommended framework for long-term scalability.
• Security & Small Community: FastAPI lacks a built-in security system. Furthermore, compared to Flask, an older framework, FastAPI is a newer framework with a smaller community and less material.
• Learning Curve: Learning asynchronous programming and how to use Pydantic for data validation might be time-consuming.

Usage Differences

FastAPI is a full-stack framework that includes everything you need to develop an API. However, Flask is a micro framework and lacks some of the functionality of FastAPI. However, Flask is ideal for quickly prototyping a concept or creating a small web application. 

The primary distinction between Flask and FastAPI is in their respective applications. FastAPI is a framework for developing APIs, while Flask is used to prototype new concepts and applications. It provides many ways to construct a backend server quickly without any coding experience.

Small-Scale Websites & Web Applications

FastAPI is simple to understand, lightweight, and can be used to create small-scale websites and apps. It has an object-relational mapping (ORM) layer that manages the application’s data objects so that you can quickly access them via coding.

The ORM layer helps manage all your databases, saving you the trouble of updating them by hand whenever new content is added, changed, or removed from the website or application.

Machine Learning Models

FastAPI is a framework for creating modern web APIs. It is developed with Flask, allowing you to develop robust and fast RESTful APIs and machine learning models.

It is an excellent option for ML models due to its various features:

• Extensible plugins enable you to add new functionality without changing the main code.
• It supports numerous libraries, such as NiFi, TensorFlow, and Keras.
• Flexible architecture enables you to tweak your API and even create new modules from scratch. 

When Should You Use Flask?

Flask can be used when developing:

• web apps
• quick prototypes.

When Should You Use FastAPI?

FastAPI can be used to:

• develop APIs from scratch
• lower the number of bugs and errors

Conclusion: Which One to Choose?

On the one hand, we have the widely used Flask framework. On the other hand, we have the well-liked FastAPI framework, famous for its numerous built-in functionalities. Both Python frameworks are straightforward and simple to use. However, FastAPI is superior since it makes up for Flask’s shortcomings.

The data validation capability of FastAPI is helpful for writing and debugging code that communicates with an API. The icing on the cake is the built-in documentation support listed with every endpoint. It also performs better during runtime. As we’ve discussed, it also has many more features, fewer flaws, and requires less time to write.

Considering these points, using the FastAPI framework in your upcoming REST project is more feasible. It’s entirely up to you to decide what to do, but you may want to consider using FastAPI.

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