Top 20 Python API Frameworks with OpenAPI Support

by Adrian Machado

It seems like every month, a new Python web framework is launched - with a new set of features, better performance, or a cleaner syntax than its predecessors. One feature that often gets ignored, however, is OpenAPI support. We've talked at great lengths about the benefits of OpenAPI - including marketing your API - but in short, OpenAPI generation via web framework is the best way to make sure your API documentation matches your API implementation. It seems like newer frameworks are starting to realize the importance of OpenAPI - with some frameworks like Robyn, adding OpenAPI docs generation as a part of the beta.

In this article, we will explore 20 of the most popular API frameworks and libraries for building APIs with Python, that have support for generating OpenAPI/Swagger specifications, either built-in or through an external library/extension.

1. FastAPI#

What is FastAPI?#

FastAPI is a modern, high-performance web framework for building APIs with Python 3.6+ based on standard Python type hints. It is designed for quick development and high efficiency. Zuplo is a proud sponsor of the FastAPI project, to help drive API development in Python.

FastAPI OpenAPI/Swagger Support#

• Built-in Support: FastAPI automatically generates OpenAPI (formerly Swagger) schemas from your code.
• Interactive Documentation: Provides Swagger UI and ReDoc interfaces out of the box, accessible via /docs and /redoc endpoints.

FastAPI Pros and Cons#

Pros

• High Performance: Comparable to NodeJS and Go, thanks to its use of asynchronous programming.
• Automatic Documentation: Generates OpenAPI schema and interactive docs automatically.
• Ease of Use: Developer-friendly with concise syntax.
• Validation: Uses Pydantic for data validation based on type hints.
• Asynchronous Support: Built on Starlette, supports async programming.

Cons

• Learning Curve: Requires understanding of Python type hints and async programming.
• Relatively New: Less mature than some older frameworks, though it has a growing community.

2. Django REST Framework (DRF)#

What is Django REST Framework?#

Django REST Framework is a powerful and flexible toolkit for building Web APIs using Django, the popular high-level Python web framework. Zuplo proudly sponsors the DRF project to continue improving the Django API development ecosystem.

Django Rest Framework OpenAPI/Swagger Support#

• Third-Party Packages: OpenAPI support via packages like drf-yasg (OpenAPI 2.x / Swagger) and drf-spectacular (OpenAPI 3.x).

Django REST Framework Pros and Cons#

Pros

• Integration with Django: Leverages Django's robust features like ORM, authentication.
• Comprehensive: Rich in features for serialization, authentication, permissions.
• Community Support: Large ecosystem and community.

Cons

• Complexity: Can be overkill for simple APIs.
• Performance: Potentially slower due to abstraction layers.

3. Flask#

What is Flask?#

Flask is a micro web framework written in Python. It is known for its simplicity and extensibility.

Flask OpenAPI/Swagger Support#

• Extensions Required: Uses extensions like APIFairy, or Flask-Smorest for OpenAPI support.
• Automatic Documentation: These extensions can generate Swagger UI and OpenAPI specs.

Flask Pros and Cons#

Pros

• Lightweight: Minimalist core, easy to get started.
• Flexible: Highly extensible with numerous plugins.
• Large Community: Abundant resources and support.

Cons

• Manual Setup: Requires additional setup for features like OpenAPI support.
• Inconsistent Extensions: Varying quality and maintenance status among extensions.

4. Connexion#

What is Connexion?#

Connexion is a framework that automagically handles HTTP requests based on OpenAPI specification, built on top of Flask.

Connexion OpenAPI/Swagger Support#

• First-Class OpenAPI Integration: Uses your OpenAPI specs to route requests and validate inputs.
• Automatic Documentation: Provides Swagger UI based on your OpenAPI files.

Connexion Pros and Cons#

Pros

• API-First Development: Encourages designing API contracts before implementation.
• Input Validation: Automatically validates requests against the OpenAPI schema.
• Less Boilerplate: Reduces code duplication.

Cons

• Rigid Structure: Requires maintaining OpenAPI specs in sync with code.
• Complexity: Can be challenging for those unfamiliar with API-first/Spec-first approaches.

5. Eve#

What is Eve?#

Eve is an out-of-the-box REST API framework powered by Flask, MongoDB, and Redis.

Eve OpenAPI/Swagger Support#

• Extension Required: Uses eve-swagger to generate Swagger/OpenAPI documentation.

Eve Pros and Cons#

Pros

• Quick Setup: Rapid API development with minimal configuration.
• Data Handling: Built-in support for MongoDB with data validation.
• Features: Supports pagination, sorting, filtering, and more.

Cons

• Database Dependency: Primarily designed for MongoDB.
• Flexibility: Less flexible if you need to deviate from its conventions.

6. Sanic#

What is Sanic#

Sanic is a Python 3.7+ web server and web framework that is written to be fast. It allows for asynchronous request handling. Zuplo is a proud sponsor of Sanic, to help push the envelope on Python API performance.

Sanic OpenAPI/Swagger Support#

• Built-in Support: Out of the box, Sanic Extensions provides automatically generated API documentation using the v3.0 OpenAPI specification.

Sanic Pros and Cons#

Pros

• High Performance: Asynchronous capabilities make it very fast.
• Async/Await Syntax: Modern Python async support.

Cons

• Smaller Ecosystem: Fewer extensions and community support compared to larger frameworks.
• Less Mature: Not as battle-tested as some alternatives.

7. Falcon#

What is Falcon?#

Falcon is a minimalist WSGI library for building speedy web APIs and app backends.

Falcon OpenAPI/Swagger Support#

• Extensions Required: Libraries like falcon-openapi or falcon-apispec enable OpenAPI support. It's worth noting that it's been many years since either of these extensions have been updated.
• Manual Integration: May require more hands-on setup to integrate OpenAPI.

Falcon Pros and Cons#

Pros

• Performance: Highly optimized for speed.
• Lightweight: Minimalistic design with few dependencies.

Cons

• Less Out-of-the-Box Features: Requires additional work for features like authentication.
• Smaller Community: Fewer resources and extensions.

8. Hug#

What is Hug#

Hug is a Python 3 framework that allows you to develop APIs as simple as possible, but no simpler.

Hug OpenAPI/Swagger Support#

• Built-in Support: Automatically generates documentation and OpenAPI schemas from your code annotations. Unfortunately this is not in the OpenAPI or Swagger formats, so you will need to transform it yourself. I created a simple script to help you get started.

Hug Pros and Cons#

Pros

• Simplicity: Minimal setup with clean syntax.
• Multiple Interfaces: Can expose APIs over HTTP, CLI, or local functions.

Cons

• Community Size: Smaller user base, which may impact support.
• Development Activity: Less frequent updates compared to more popular frameworks.

9. Bottle#

What is Bottle?#

Bottle is a fast, simple, and lightweight WSGI micro web-framework for Python.

Bottle OpenAPI/Swagger Support#

• Extensions Required: Use bottle-swagger or bottle-openapi-3.
• Manual Configuration: Might require manual steps to document APIs.

Bottle Pros and Cons#

Pros

• No Dependencies: Single-file module with no external dependencies.
• Lightweight: Ideal for small applications and prototyping.

Cons

• Limited Features: Minimalist by design; lacks advanced features out of the box.
• Smaller Ecosystem: Fewer plugins and extensions.

10.Pyramid#

What is Pyramid?#

Pyramid is a small, fast, down-to-earth Python web framework. It is designed to make creating web applications easier.

Pyramid OpenAPI/Swagger Support#

• Extensions Required:pyramid_openapi3 is the latest extension, while others use Yelp's pyramid_swagger. If you use cornice to build APIs on top of Pyramid, you can use the cornice-swagger extension to add OpenAPI support.

Pyramid Pros and Cons#

Pros

• Flexibility: Suitable for both small and large applications.
• Security: Strong emphasis on security practices.

Cons

• Complexity: Steeper learning curve.
• Popularity: Less mainstream compared to Django or Flask.

11. Molten (deprecated)#

What is Molten?#

Molten is a minimal, fast, and extensible framework for building HTTP APIs in Python. The project was deprecated in April 2024.

Molten OpenAPI/Swagger Support#

• Built-in Support: Automatically generates OpenAPI documentation from route definitions.
• Type Annotations: Uses type hints for routing and validation.

Molten Pros and Cons#

Pros

• Performance: Optimized for speed.
• Modern Features: Supports dependency injection and type annotations.

Cons

• Limited Adoption: Smaller community and fewer resources.
• Less Mature: Not as widely used or tested.

12. BlackSheep#

What is BlackSheep?#

BlackSheep is an asynchronous web framework to build event-based web applications with Python.

BlackSheep OpenAPI/Swagger Support#

• Built-in Support: BlackSheep implements automatic generation of OpenAPI documentation for most common scenarios, and provides methods to enrich the documentation with details.

BlackSheep Pros and Cons#

Pros

• Async Support: Designed for modern asynchronous Python.
• Performance: High-performance routing and handling.

Cons

• Community Size: Smaller user base.
• Documentation: Less comprehensive documentation.

13. Quart#

What is Quart?#

Quart is an ASGI web framework based on Flask, aiming to provide Flask's ease of use with the added benefit of async support.

Quart OpenAPI/Swagger Support#

• Extensions Required: Similar to Flask, relies on extensions for OpenAPI support. quart-schema is a newer extension, with the other being the older quart-openapi.
• Compatibility: Can use many Flask extensions directly.

Quart Pros and Cons#

Pros

• Async Support: Full support for async and await.
• Familiarity: Similar API to Flask.

Cons

• Extension Compatibility: Not all Flask extensions are compatible.
• Smaller Ecosystem: Fewer Quart-specific resources.

14. Responder#

What is Responder?#

Responder is a web framework for Python that aims to bring the best of Flask, Falcon, and others into one.

Responder OpenAPI/Swagger Support#

• Built-in Support: Automatically generates OpenAPI documentation.
• Interactive Documentation: Provides Swagger UI.

Responder Pros and Cons#

Pros

• Simplicity: Easy to learn and use.
• Automatic Documentation: Reduces overhead in maintaining API docs.

Cons

• Maintenance Status: As of 2023, it is less actively maintained.
• Community Size: Smaller user base and fewer resources.

15. Tornado#

What is Tornado?#

Tornado is a Python web framework and asynchronous networking library.

Tornado OpenAPI/Swagger Support#

• Extensions Required: Use tornado-swagger or similar libraries.
• Manual Setup: May require additional effort to integrate.

Tornado Pros and Cons#

Pros

• Scalability: Good for applications requiring long-lived connections.
• Asynchronous: Built-in async capabilities.

Cons

• Less Conventional: Different from standard WSGI frameworks.
• Complexity: May be more complex to work with.

16. Robyn#

What is Robyn#

Robyn is a high-performance, async Python web framework with a focus on speed and efficiency. It leverages Rust's Tokio runtime via PyO3 to achieve impressive performance metrics. Robyn aims to be one of the fastest Python web frameworks available.

OpenAPI/Swagger Support#

• Built-in Support: Robyn has OpenAPI support built-in, with both the spec on /openapi.json and documentation UI on /docs.

Robyn Pros and Cons#

Pros

• High Performance: Utilizing Rust's async runtime provides significant speed advantages.
• Asynchronous: Built with async and await syntax for modern Python development.
• Minimalistic: Lightweight framework that avoids unnecessary overhead.

Cons

• Maturity: Being relatively new, it may lack features and stability compared to more established frameworks.
• Community Support: Smaller community means fewer resources, plugins, and third-party extensions.
• Documentation: May have less comprehensive documentation due to its newer status.

17. Uvicorn#

What is Uvicorn?#

Uvicorn is a lightning-fast ASGI server implementation, using uvloop and httptools. It is designed to run asynchronous Python web applications, particularly those built with frameworks like FastAPI, Starlette, and others.

Uvicorn OpenAPI/Swagger Support#

• Not a Framework: Uvicorn is an ASGI server, not a web framework. It doesn't provide features like routing, middleware, or OpenAPI support.
• Usage with Frameworks: When used with frameworks like FastAPI or Starlette, Uvicorn serves the application, and the framework handles OpenAPI/Swagger support.

Uvicorn Pros and Cons#

Pros

• High Performance: Extremely fast due to the use of uvloop and httptools.
• Standards-Compliant: Implements the ASGI specification, ensuring compatibility with various frameworks.
• Lightweight: Minimal overhead and easy to deploy.

Cons

• Not a Full Framework: Doesn't include web framework features; you'll need to use it in conjunction with an ASGI-compatible framework.

18. Starlette#

What is Starlette?#

Starlette is a lightweight ASGI framework/toolkit, ideal for building high-performance async services in Python. It provides the essential components needed to build web applications, including routing, middleware, sessions, and more.

Starlette OpenAPI/Swagger Support#

• Built-in Support: Starlette supports generating API schemas by inspecting the routes on the application through app.routes, and using the docstrings or other attributes on the endpoints in order to determine a complete API schema.

Starlette Pros and Cons#

Pros

• High Performance: Designed for speed and efficiency, suitable for building performant APIs.
• Asynchronous: Fully supports async and await, leveraging modern Python features.
• Modular Design: Allows developers to pick and choose components as needed.

Cons

• Minimalist: Lacks some higher-level features out of the box, such as automatic OpenAPI documentation.
• Learning Curve: May be challenging for those new to async programming or who prefer batteries-included frameworks.

19. Litestar#

What is Litestar?#

Litestar (formerly known as Starlite) is a newly developed ASGI framework inspired by Starlette and FastAPI, aiming to provide a balance between performance and ease of use.

Litestar OpenAPI/Swagger Support#

• Built-in Support: Litestar has built-in OpenAPI schema generation and automatic documentation.
• Interactive Documentation: Provides Swagger UI and ReDoc out of the box.

Litestar Pros and Cons#

Pros

• Performance: Designed to be fast and efficient.
• Ease of Use: Simplifies API development with sensible defaults.
• Modern Features: Supports async/await, type annotations, and dependency injection.

Cons

• Newness: As a newer framework, it may have less community support and resources.
• Evolving API: Frequent updates might lead to breaking changes.

20. API Star (Deprecated)#

What is API Star?#

APIStar was a framework for building web APIs with OpenAPI support. The project was deprecated in February 2022.

API Star OpenAPI/Swagger Support#

• Built-in Support: Used OpenAPI schemas directly in code.

API Star Pros and Cons#

Pros

• Strong Typing: Emphasized type annotations.

Cons

• Deprecated: No longer maintained; not recommended for new projects.

How to Pick a Python API Framework?#

When choosing a framework with OpenAPI/Swagger support, consider the following:

• Project Requirements: The size and complexity of your project. It might be hard to find developers for niche frameworks, and difficult to train-up existing teammates on the new paradigms/concepts.
• Community and Support: Frameworks with larger communities tend to have more resources.
• Performance Needs: If high performance is crucial, consider asynchronous frameworks like FastAPI or Sanic.
• Development Style: Whether you prefer code-first or API-first/Spec-first development.

What is the Best Python API Framework?#

FastAPI stands out for its built-in OpenAPI support, high performance, thriving community, and modern features. Django REST Framework is ideal if you're already using Django and need a robust, feature-rich API framework. Flask offers flexibility and simplicity but requires extensions for OpenAPI support - so we don't recommend it for newer projects..

What is the Fastest Python API Framework?#

As of November 2024, Robyn claims to be the fastest framework:

Python API Essentials - Don't Forget These!#

Regardless of which Python API framework you choose, you will need the 3 pillars of APIs before you go to prod:

1. Authentication (ex. API Key Authentication)
2. Documentation (ex. Developer documentation portal with API reference, auth, billing, analytics, code samples, etc.)
3. Protection (ex. Rate limiting and quotas)

Zuplo can take care of all of these for you - for free! You can start for free or grab time with our team and see Zuplo in action.

Frequently Asked Questions#

What is WSGI?#

WSGI stands for Web Server Gateway Interface. It is a specification that defines a standard interface between web servers and Python web applications or frameworks. WSGI allows developers to write portable web applications that can run on any WSGI-compliant web server, promoting interoperability and flexibility in the Python web ecosystem.

What is ASGI?#

ASGI stands for Asynchronous Server Gateway Interface. It is a specification that defines a standard interface between asynchronous Python web servers, frameworks, and applications. ASGI was developed as a successor to WSGI (Web Server Gateway Interface) to support asynchronous, event-driven applications and protocols beyond HTTP, such as WebSockets.

What are the Differences Between WSGI and ASGI#

Where Should I Host my Python API?#

There are many options for hosting your Python API including

• Platform as a Service (PaaS) providers like PythonAnywhere or Render
• Infrastructure as a Service (IaaS) aka big clouds like AWS EC2, Azure VM, GCP Compute Engine
• Virtual Private Servers (VPS) like DigitalOCean or Linode
• Containers (Docker + Kubernetes) using Google Kubernetes Engine
• Serverless Platforms like AWS Lambda or Google Cloud Functions

What is the Best API Gateway for Python APIs?#

Zuplo's edge API gateway provides superior caching performance, an intuitive developer experience using git, and full OpenAPI support. This makes it a natural choice for most Python API frameworks, especially the ones with OpenAPI support.

What is the Best Way to Document a Python API?#

Many Python frameworks (ex. FastAPI, Litestar) have built-in support for OpenAPI, which most API documentation platforms (ex. Zudoku) support out-of-the-box. For a complete API documentation experience, consider Zuplo's Developer Portal - which features docs, built-in authentication, self-serve billing, and usage analytics.

What is the Best Way to Monetize a Python API?#

The fastest and most affordable way to set up monetization is using Zuplo's API monetization feature - which integrates directly with payment platforms like Stripe. You can easily create plans, allow users to sign up, issue API keys, control subscriptions, and enforce quotas.