Esmerald

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

---

Documentation: https://esmerald.dev 📚

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

---

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 3.9+ based on standard python type hints and on the top of the heavily known Lilya and Pydantic/msgspec.

Success

The official supported version is always the latest released.

Motivation

There are great frameworks out there like FastAPI, 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, at the very beginning, 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.

Requirements

• Python 3.9+

Esmerald wouldn't be possible without at least these two:

• Lilya
• Pydantic

Installation

$ 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

Support for the internal scheduler:

$ pip install esmerald[schedulers]

Support for the jwt used internally by Esmerald:

$ pip install esmerald[jwt]

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

Start a project using directives

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 simple suggested structure.

esmerald createproject <YOUR-PROJECT-NAME> --simple

This will generate a scaffold for your project with some pre-defined files in a simple fashion with a simple ready to go Esmerald application.

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 with a detailed example.

Warning

Running this directive will generate only the scaffold of the project but some additional information is still needed to start the project. This only provides a structure of files that can be used to start an Esmerald application but it is not mandatory.

Key Features

• Fluid and Fast: Thanks to Lilya and Pydantic/msgpec.
• 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 ORJSON support.
• Lifespan: Support for the newly Lilya lifespan.
• Dependency Injection: Like any other great framework out there.
• Scheduler: Yes, that's right, we come with a scheduler for those background tasks.
• Simplicity from settings: Yes, we have a way to make the code even cleaner by introducing settings based systems.
• msgspec - Support for msgspec.

Relation to Lilya and other frameworks

Esmerald uses Lilya 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.

Quickstart

To quickly start with Esmerald, you can just do this. Using uvicorn as example.

#!/usr/bin/env python
import uvicorn

from esmerald import Esmerald, Gateway, JSONResponse, Request, get


@get()
def welcome() -> JSONResponse:
    return JSONResponse({"message": "Welcome to Esmerald"})


@get()
def user(user: str) -> JSONResponse:
    return JSONResponse({"message": f"Welcome to Esmerald, {user}"})


@get()
def user_in_request(request: Request) -> JSONResponse:
    user = request.path_params["user"]
    return JSONResponse({"message": f"Welcome to Esmerald, {user}"})


app = Esmerald(
    routes=[
        Gateway("/esmerald", handler=welcome),
        Gateway("/esmerald/{user}", handler=user),
        Gateway("/esmerald/in-request/{user}", handler=user_in_request),
    ]
)


if __name__ == "__main__":
    uvicorn.run(app, port=8000)

Then you can access the endpoints.

Using Esmerald as a decorator

To quickly start with Esmerald you can also use it as decorator, you can just do this. Using uvicorn as example.

#!/usr/bin/env python
import uvicorn

from esmerald import Esmerald, JSONResponse, Request


app = Esmerald()


@app.get("/esmerald")
def welcome() -> JSONResponse:
    return JSONResponse({"message": "Welcome to Esmerald"})


@app.get("/esmerald/{user}")
def user(user: str) -> JSONResponse:
    return JSONResponse({"message": f"Welcome to Esmerald, {user}"})


@app.get("/esmerald/in-request/{user}")
def user_in_request(request: Request) -> JSONResponse:
    user = request.path_params["user"]
    return JSONResponse({"message": f"Welcome to Esmerald, {user}"})


if __name__ == "__main__":
    uvicorn.run(app, port=8000)

Settings

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 ugly 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 ApplicationObjectExample

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

app = ApplicationObjectExample(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 by default! Why? Because the application looks for a ESMERALD_SETTINGS_MODULE environment variable to startup and if not found, defaults to the application global settings. This is simple of course but can you override inside the object as well? Yes, absolutely.

from esmerald import Esmerald


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

Same as the classics.

Let's talk Esmerald settings module.

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.

Custom Settings

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 is 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: str = '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.

MacOS & LinuxWindows

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

$env:ESMERALD_SETTINGS_MODULE="myapp.settings.Development"; python -m src.app.py

Gateway, WebSocketGateway and Include

Lilya offers the 'Path' 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

src/app.py

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


@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()


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

Design in mind

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

The handlers (controllers)

src/myapp/accounts/controllers.py

from pydantic import BaseModel

from esmerald import (
    APIView,
    JSONResponse,
    Request,
    Response,
    WebSocket,
    get,
    post,
    put,
    status,
    websocket,
)


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": data.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(self, request: Request, url: str) -> Response:
        return Response(f"URL: {url}")

    @post(path="/{url}", status_code=status.HTTP_201_CREATED)
    async def mars(self, 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 /.

The gateways (urls)

myapp/accounts/urls.py

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


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

If a path is not provided, defaults to /.

The Include

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.

Note

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

Importing using namespaceImporting using routes

src/urls.py

from esmerald import Include

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

src/myapp/urls.py

from myapp.accounts.urls import route_patterns

from esmerald import Include

route_patterns = [Include(routes=route_patterns)]

If a path is not provided, defaults to /.

Using a different pattern

src/myapp/accounts/urls.py

from esmerald import Gateway, WebSocketGateway

from .controllers import World, another, home, world_socket

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

Importing using namespace

src/myapp/urls.py

from esmerald import Include

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

Include and Esmerald

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:

src/urls.py

from esmerald import Include

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

src/app.py

from esmerald import Esmerald, Include

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

Run the application

As mentioned before, we recommend uvicorn for production, but it is 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.

Run the application with custom settings

Using uvicorn:

MacOS & LinuxWindows

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.

$env: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.

OpenAPI documentation

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.
• Rapidoc - /docs/rapidoc.

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

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

Notes

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! 😊

Sponsors

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.