molten: modern API framework¶
Release v1.0.2. (Installation, Changelog, Discuss, Source Code)
molten is a minimal, extensible, fast and productive framework for building HTTP APIs with Python.
Here’s a quick taste:
from molten import App, Route
def hello(name: str, age: int) -> str:
return f"Hi {name}! I hear you're {age} years old."
app = App(routes=[Route("/hello/{name}/{age}", hello)])
For more, take a look at the examples folder in the GitHub repo.
Features¶
Here’s a selection of molten’s features that we’re most proud of.
Request Validation¶
molten can automatically validate requests according to predefined schemas, ensuring that your handlers only ever run if given valid input:
from molten import App, Route, field, schema
from typing import Optional
@schema
class Todo:
id: Optional[int] = field(response_only=True)
description: str
status: str = field(choices=["todo", "done"], default="todo")
def create_todo(todo: Todo) -> Todo:
# Do something to store the todo here...
return todo
app = App(routes=[Route("/todos", create_todo, method="POST")])
Schemas are PEP484-compatible, which means mypy and molten go hand-in-hand, making your code more easy to maintain. Schema instances are automatically serializable and you can pick and choose which fields to exclude from responses and requests.
Dependency Injection¶
Write clean, decoupled code by leveraging DI. Define components for everything from settings to DB access and business logic, test them in isolation and swap them out as needed:
from molten import App, Include, Route
class TodoManager:
def __init__(self, db: DB) -> None:
self.db = db
def get_all(self) -> List[Todo]:
...
def save(self, todo: Todo) -> Todo:
...
class TodoManagerComponent:
is_cacheable = True
is_singleton = True
def can_handle_parameter(self, parameter: Parameter) -> bool:
return parameter.annotation is TodoManager
def resolve(self, db: DB) -> TodoManager:
return TodoManager(db)
def list_todos(todo_manager: TodoManager) -> List[Todo]:
return todo_manager.get_all()
def create_todo(todo: Todo, todo_manager: TodoManager) -> Todo:
return todo_manager.save(todo)
app = App(
components=[
DBComponent(),
TodoManagerComponent(),
],
routes=[
Include("/todos", [
Route("/", list_todos),
Route("/", create_todo, method="POST"),
]),
],
)
Here we’ve declared a Todo manager whose job it is to store and load
Todos in the DB. In order for handlers to be able to request manager
instances from the DI system, we also define a component that knows
how and when to instantiate a TodoManager. In this case, a
TodoManager is injected whenever a parameter is annotated with
TodoManager and the component itself requests an instance of the
DB object.
For a full example, check out the todo API example.
Functional Middleware¶
molten has support for function-based middleware:
def auth_middleware(handler: Callable[..., Any]) -> Callable[..., Any]:
def middleware(authorization: Optional[Header]) -> Any:
if authorization != "secret":
raise HTTPError(HTTP_403, {"error": "forbidden"})
return handler()
return middleware
As you would expect, middleware functions can request dependencies
from the DI system. In the above example, you can see how the auth
middleware requests the Authorization header via DI and either
cancels the request or proceeds with it based on its value.
Batteries Included¶
The molten.contrib package contains various functionality commonly required by APIs in the real world such as configuration files, prometheus metrics, request ids, sessions, SQLAlchemy, templating, websockets and more.
Type Safe¶
molten uses PEP484 type hints and mypy extensively. It is also compatible with PEP561 so if your app uses mypy then it’ll automatically pick up the annotations in the molten package.
Get It Now¶
molten is available on PyPI:
$ pip install -U molten
Read the Motivation behind it or the User Guide if you’re ready to get started.
User Guide¶
This part of the documentation is focused primarily on teaching you how to use molten.
API Reference¶
This part of the documentation is focused on detailing the various bits and pieces of the molten developer interface.
