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A developer centric, performant Python web framework

Project description


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Xpresso is an ASGI web framework built on top of Starlette, Pydantic and di, with heavy inspiration from FastAPI.

Some of the standout features are:

  • ASGI support for high performance (within the context of Python web frameworks)
  • OpenAPI documentation generation
  • Automatic parsing and validation of request bodies and parameters, with hooks for custom extractors
  • Full support for OpenAPI parameter serialization
  • Highly typed and tested codebase with great IDE support
  • A powerful dependency injection system, backed by di


Python 3.7+


pip install xpresso

You'll also want to install an ASGI server, such as Uvicorn.

pip install uvicorn


Create a file named

from pydantic import BaseModel
from xpresso import App, Path, FromPath, FromQuery

class Item(BaseModel):
    item_id: int
    name: str

async def read_item(item_id: FromPath[int], name: FromQuery[str]) -> Item:
    return Item(item_id=item_id, name=name)

app = App(

Run the application:

uvicorn example:app

Navigate to in your browser. You will get the following JSON response:


Now navigate to to poke around the interactive Swagger UI documentation:

Swagger UI

For more examples, tutorials and reference materials, see our documentation.

Inspiration and relationship to other frameworks

Xpresso is mainly inspired by FastAPI. FastAPI pioneered several ideas that are core to Xpresso's approach:

  • Leverage Pydantic for JSON parsing, validation and schema generation.
  • Leverage Starlette for routing and other low level web framework functionality.
  • Provide a simple but powerful dependency injection system.
  • Use that dependency injection system to provide extraction of request bodies, forms, query parameters, etc.

Xpresso takes these ideas and refines them by:

Current state

This project is under active development. It should not be considered "stable" or ready to be used in production. It is however ready for experimentation and learning!

What is implemented and mostly stable?

  1. Extraction and OpenAPI documentation of parameters (query, headers, etc.) and request bodies (including multipart requests).
  2. Parameter serialization.
  3. Routing, including applications, routers and routes.
  4. Dependency injection and testing utilities (dependency overrides).

Most of this APIs will be generally stable going forward, although some minor aspects like argument names will probably change at some point.

What is not implemented or unstable?

  1. Low-level API for binders (stuff in xpresso.binders): this is public, but should be considered experimental and is likely to change. The high level APIs (FromPath[str] and Annotated[str, PathParam(...)]) are likely to be stable.
  2. Security dependencies and OpenAPI integration. This part used to exist, but needed some work. It is planned for the future, but we need to think about the scope of these features and the API.

See this release on GitHub: v0.46.0

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