🚀 Highly scalable, performant, easy to learn, easy to code and for every application. 🚀

Documentation: https://esmerald.dev 📚

Source Code: https://github.com/dymmond/esmerald

The official supported version is always the latest released.

Esmerald is a modern, powerful, flexible, high performant, web framework designed to build not only APIs but also full scalable applications from the smallest to enterprise level.

Esmerald is designed to build with python 3.8+ and based on standard python type hints. Initially built on the top of Starlette and later on moved to Lilya and Pydantic/msgspec.

Check out the Esmerald documentation 📚

The official supported version is always the latest released.

There are great frameworks out there like FastAPI, Starlite, Flama, Flask, Django... All of them solving majority of the current day-to-day problems of 99% of the applications but leaving the 1% that is usually around structure and design/business without to much to do.

Esmerald got the inspiration from those great frameworks out there and was built with all the known amazing features but with business in mind as well. Starlite, for example, gave the inspiration for the transformers and for the Signature models, something very useful that helped Esmerald integerating with pydantic. FastAPI gave the inspiration for API designing, Django for the permissions, Flask for the simplicity, NestJS for the controllers and the list goes on.

For a job to be done properly, usually it is never done alone and there is always a driver and inspiration to it.

• python 3.8+

Esmerald wouldn't be possible without two colossals:

• Starlette
• Pydantic

$ pip install esmerald

An ASGI server is also needed to run in production, we recommend Uvicorn but it is entirely up to you.

$ pip install uvicorn

If you want install esmerald with specifics:

Support for template system such as jinja2 and mako:

$ pip install esmerald[templates]

Support for the internal scheduler:

$ pip install esmerald[schedulers]

Support for the jwt used internally by Esmerald:

$ pip install esmerald[jwt]

Support for ORJSON and UJSON:

$ pip install esmerald[encoders]

If you want to use the esmerald testing client:

$ pip install esmerald[test]

If you want to use the esmerald shell:

More details about this topic in the docs

$ pip install esmerald[ipython] # default shell
$ pip install esmerald[ptpython] # ptpython shell

!!! Warning This is for more advanced users that are already comfortable with Esmerald (or Python in general) or feel like it is not a problem using these directives. If you do not feel comfortable yet to use this, please continue reading the documentation and learning more about Esmerald.

If you wish to start an Esmerald project with a default suggested structure.

esmerald createproject <YOUR-PROJECT-NAME>

This will generate a scaffold for your project with some pre-defined files in a simple fashion. This will also generate a file for the tests using the EsmeraldTestClient, so make sure you run:

$ pip install esmerald[test]

Or you can skip this step if you don't want to use the EsmeraldTestClient.

You can find more information about this directive and how to use it.

• Fluid and Fast: Thanks to Starlette and Pydantic/msgspec.
• Fast to develop: Thanks to the simplicity of design, the development times can be reduced exponentially.
• Intuitive: If you are used to the other frameworks, Esmerald is a no brainer to develop.
• Easy: Developed with design in mind and easy learning.
• Short: With the OOP available natively there is no need for code duplication. SOLID.
• Ready: Get your application up and running with production-ready code.
• OOP and Functional: Design APIs in any desired way. OOP or Functional is available.
• Async and Sync: Do you prefer sync or async? You can have both.
• Middleware: Apply middlewares on the application level or API level.
• Exception Handlers: Apply exception handlers on any desired level.
• Permissions: Apply specific rules and permissions on each API.
• Interceptors: Intercept requests and add logic before reaching the endpoint.
• Pluggables: Create plugins for Esmerald and hook them into any application and/or distribute them.
• DAO and AsyncDAO: Avoid database calls directly from the APIs. Use business objects instead.
• ORM Support: Native support for Saffier and Edgy.
• ODM Support: Native support for Mongoz.
• APIView: Class Based endpoints for your beloved OOP design.
• JSON serialization/deserialization: Both UJSON and ORJON support.
• Lifespan: Support for the newly lifespan and on_start/on_shutdown events.
• Scheduler: Yes, that's right, it comes with a scheduler for those automated tasks.
• Dependency Injection: Like any other great framework out there.
• Simplicity from settings: Yes, we have a way to make the code even cleaner by introducing settings based systems.
• msgspec - Support for msgspec.

Esmerald uses Starlette under the hood. The reason behind this decison comes with the fact that performance is there and no issues with routing.

Once the application is up, all the routes are mounted and therefore the url paths are defined. Esmerald encourages standard practices and design in mind which means that any application, big or small, custom or enterprise, fits within Esmerald ecosystem without scalability issues.

Like every other framework, when starting an application, a lot of settings can/need to be passed to the main object and this can be very dauting and hugly to maintain and see.

Esmerald comes with the settings in mind. A set of defaults that can be overridden by your very own settings module but not limited to it as you can still use the classic approach of passing everything into a Esmerald instance directly when instantiating.

Example of classic approach:

from example import ExampleObject

# ExampleObject is an instance of another application
# and it serves only for example

app = ExampleObject(setting_one=..., setting_two=..., setting_three=...)

Inspired by the great Django and using pydantic, Esmerald has a default object ready to be used out-of-the-box.

Esmerald:

from esmerald import Esmerald

app = Esmerald()

And that's it! All the default settings are loaded! This is simple of course but can you override inside the object as well? Yes!

from esmerald import Esmerald

app = Esmerald(app_name='My App', title='My title')

Same as the classics.

So how does Esmerald know about the default settings? Enters Esmerald settings module.

This is the way Esmerald defaults the values. When starting an application, the system looks for a ESMERALD_SETTINGS_MODULE environment variable. If no variable is supplied then the system will default to EsmeraldAPISettings settings and start.

Separation of settings by enviromment is a must have these days and starting with default of Esmerald will not be enough for any application.

The settings are pydantic standard settings and therefore compatible with Esmerald. The system brings some defaults that can be used out-of-the-box but it's not mandatory to be used. The environment defaults to production.

from esmerald import EsmeraldAPISettings
from esmerald.conf.enums import EnvironmentType

class Development(EsmeraldAPISettings):
    app_name: bool = 'My app in dev'
    environment: str = EnvironmentType.DEVELOPMENT

Load the settings into your Esmerald application:

Assuming your Esmerald app is inside an src/app.py.

ESMERALD_SETTINGS_MODULE='myapp.settings.Development' python -m src.app.py

Starlette offers the Route classes for simple path assignments but this is also very limiting if something more complex in mind. Esmerald extends that functionality and adds some flair and levels up by having the Gateway, WebSocketGateway and Include.

Those are special objects that allow all the magic of Esmerald to happen.

For a classic, direct, one file single approach.

In a nutshell:

from esmerald import Esmerald, get, status, Request, UJSONResponse, Gateway, WebSocketGateway, Websocket

@get(status_code=status.HTTP_200_OK)
async def home() -> UJSONResponse:
    return UJSONResponse({
        "detail": "Hello world"
    })


@get()
async def another(request: Request) -> dict:
    return {
        "detail": "Another world!"
    }

@websocket(path="/{path_param:str}")
async def world_socket(socket: Websocket) -> None:
    await socket.accept()
    msg = await socket.receive_json()
    assert msg
    assert socket
    await socket.close()


app = Esmerald(routes=[
    Gateway(handler=home),
    Gateway(handler=another),
    WebSocketGateway(handler=world_socket),
])

Good design is always encouraged and Esmerald allows complex routing on any level.

from esmerald import get, post, put, status, websocket, APIView, Request, JSONResponse, Response, WebSocket
from pydantic import BaseModel


class Product(BaseModel):
    name: str
    sku: str
    price: float


@put('/product/{product_id}')
def update_product(product_id: int, data: Product) -> dict:
    return {"product_id": product_id, "product_name": product.name }


@get(status_code=status.HTTP_200_OK)
async def home() -> JSONResponse:
    return JSONResponse({
        "detail": "Hello world"
    })


@get()
async def another(request: Request) -> dict:
    return {
        "detail": "Another world!"
    }


@websocket(path="/{path_param:str}")
async def world_socket(socket: Websocket) -> None:
    await socket.accept()
    msg = await socket.receive_json()
    assert msg
    assert socket
    await socket.close()


class World(APIView):

    @get(path='/{url}')
    async def home(request: Request, url: str) -> Response:
        return Response(f"URL: {url}")

    @post(path='/{url}', status_code=status.HTTP_201_CREATED)
    async def mars(request: Request, url: str) -> JSONResponse:
        ...

    @websocket(path="/{path_param:str}")
    async def pluto(self, socket: Websocket) -> None:
        await socket.accept()
        msg = await socket.receive_json()
        assert msg
        assert socket
        await socket.close()

If a path is not provided, defaults to /.

from esmerald import Gateway, WebSocketGateway
from .views import home, another, world_socket, World

route_patterns = [
    Gateway(handler=update_product),
    Gateway(handler=home),
    Gateway(handler=another),
    Gateway(handler=World),
    WebSocketGateway(handler=world_socket),
]

If a path is not provided, defaults to /.

This is a very special object that allows the import of any route from anywhere in the application.

Include accepts the import via namespace or via routes list but not both.

When using a namespace, the Include will look for the default route_patterns object list in the imported namespace unless a different pattern is specified.

The pattern only works if the imports are done via namespace and not via routes.

Importing using namespace:

from esmerald import Include

route_patterns = [
    Include(namespace='myapp.accounts.urls')
]

Importing using routes:

from esmerald import Include
from myapp.accounts import urls

route_patterns = [
    Include(routes=urls.route_patterns)
]

If a path is not provided, defaults to /.

from esmerald import Gateway, WebSocketGateway
from .views import home, another, world_socket, World

my_urls = [
    Gateway(handler=update_product),
    Gateway(handler=home),
    Gateway(handler=another),
    Gateway(handler=World),
    WebSocketGateway(handler=world_socket),
]

Importing using namespace:

from esmerald import Include

route_patterns = [
    Include(namespace='myapp.accounts.urls', pattern='my_urls')
]

The Include can be very helpful mostly when the goal is to avoid a lot of imports and massive list of objects to be passed into one single object. This can be particulary useful to make a Esmerald instance.

Example:

from esmerald import Include

route_patterns = [
    Include(namespace='myapp.accounts.urls', pattern='my_urls')
]

from esmerald import Esmerald, Include

app = Esmerald(routes=[Include('src.urls')])

As mentioned before, we recomment uvicorn for production but it's not mandatory.

Using uvicorn:

uvicorn src:app --reload

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [28720]
INFO:     Started server process [28722]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

Using uvicorn:

ESMERALD_SETTINGS_MODULE=myapp.AppSettings uvicorn src:app --reload

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [28720]
INFO:     Started server process [28722]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

Esmerald also comes with OpenAPI docs integrated. For those used to that, this is roughly the same and to make it happen, there were inspirations that helped Esmerald getting there fast.

Esmerald starts automatically the OpenAPI documentation by injecting the OpenAPIConfig default from the settings and makes Swagger, ReDoc an Stoplight elements available to you out of the box.

To access the OpenAPI, simply start your local development and access:

• Swagger - /docs/swagger.
• Redoc - /docs/redoc.
• Stoplight Elements - /docs/elements.

There are more details about how to configure the OpenAPIConfig within the documentation.

There is also a good explanation on how to use the OpenAPIResponse as well.

This is just a very high-level demonstration of how to start quickly and what Esmerald can do. There are plenty more things you can do with Esmerald. Enjoy! 😊

Currently there are no sponsors of Esmerald but you can financially help and support the author though GitHub sponsors and become a Special one or a Legend.