Kui Framework

Kui Web Framework Guide

Kui is a Python web framework supporting both ASGI (async) and WSGI (sync). It provides type-safe parameter binding via Annotated, dependency injection, OpenAPI documentation generation, class-based views, and middleware composition.

ASGI imports: from kui.asgi import ... WSGI imports: from kui.wsgi import ...

The two modules expose nearly identical APIs; ASGI handlers are async def, WSGI handlers are plain def. All examples below use ASGI unless noted.

1. Application

from kui.asgi import Kui, OpenAPI

app = Kui(
    routes=[],                  # Initial routes
    http_middlewares=[],         # App-level HTTP middleware
    socket_middlewares=[],       # App-level WebSocket middleware (ASGI only)
    cors_config=None,           # Optional CORSConfig dict
    exception_handlers={},      # {status_or_exc_type: handler}
     # Lifespan callbacks (ASGI only)
    templates=None,             # Optional Jinja2Templates instance
    response_converters={},     # {type: converter_func}
    json_encoder={},            # {type: serializer_func}
)

app is a standard ASGI callable (async def __call__(scope, receive, send)). For WSGI it is a standard def __call__(environ, start_response).

Shared state

app.state.db = create_pool()   # Set once; ImmutableAttribute prevents reassignment

2. Routing

2.1 Decorator style (most common)

@app.router.http.get("/users/{user_id:int}")
async def get_user(user_id: Annotated[int, Path()]):
    return {"id": user_id}

@app.router.http.post("/users")
async def create_user(body: Annotated[UserCreate, Body()]):
    return body, 201

# Any HTTP method
@app.router.http("/health")
async def health():
    return "ok"

Available method shortcuts: .get(), .post(), .put(), .patch(), .delete().

Decorator parameters: path, name=, middlewares=[], summary=, description=, tags=.

2.2 Route objects with << operator

from kui.asgi import HttpRoute, SocketRoute

app.router <<= HttpRoute("/", homepage)
app.router <<= SocketRoute("/ws", ws_handler)

# Chain multiple
app.router <<= (
    app.router
    << HttpRoute("/a", handler_a)
    << HttpRoute("/b", handler_b)
)

2.3 Routes container with prefix

from kui.asgi import Routes, HttpRoute

api_routes = Routes(
    HttpRoute("/users", list_users),
    HttpRoute("/posts", list_posts),
    namespace="api",           # Prefixes route names
    tags=["API"],              # OpenAPI tags for all routes
    http_middlewares=[auth_mw],
)

# Prefix with // operator
app.router <<= "/api/v1" // api_routes

2.4 Reverse URL lookup

app.router.url_for("route-name") # "/path"
app.router.url_for("user", {"id": 42}) # "/users/42"

2.5 Route middleware via @ operator

from kui.asgi import HttpRoute, required_method, allow_cors

route = HttpRoute("/data", handler) @ required_method("GET") @ allow_cors()
app.router <<= route

2.6 Path parameters

Supported converters: {name} (string), {name:int}, {name:decimal}, {name:date}, {name:uuid}, {name:any} (rest-of-path). str cannot match /; use any for rest-of-path (must be at the end).

2.7 WebSocket routing (ASGI only)

@app.router.websocket("/ws")
async def ws_handler():
    await websocket.accept()
    data = await websocket.receive_json()
    await websocket.send_json({"echo": data})
    await websocket.close()

3. Parameter Binding

All parameter bindings use typing_extensions.Annotated. The framework inspects the handler signature, extracts and validates parameters via Pydantic, and injects them as keyword arguments.

from typing_extensions import Annotated
from kui.asgi import Path, Query, Header, Cookie, Body

@app.router.http.get("/items/{item_id:int}")
async def get_item(
    item_id: Annotated[int, Path()],
    q: Annotated[str, Query(...)],                  # required query param
    limit: Annotated[int, Query(10)],                # default value
    x_token: Annotated[str, Header(alias="x-token")],  # header (alias lowercased)
    session: Annotated[str, Cookie()] = "",           # optional cookie
):
    ...

Request body

from pydantic import BaseModel

class Item(BaseModel):
    name: str
    price: float

@app.router.http.post("/items")
async def create_item(item: Annotated[Item, Body(...)]):
    return item

# Exclusive body: entire JSON body maps to one parameter
@app.router.http.post("/raw")
async def raw_body(data: Annotated[dict, Body(exclusive=True)]):
    return data

Field options

Path(), Query(), Header(), Cookie(), Body() all accept standard Pydantic Field kwargs: default, default_factory, alias, title, description, plus any validation kwargs (ge, le, min_length, max_length, pattern, etc.).

File upload

from kui.asgi import UploadFile, Body

@app.router.http.post("/upload")
async def upload(file: Annotated[UploadFile, Body(...)]):
    return {"filename": file.filename, "content": file.read().decode()}

UploadFile attributes: filename, content_type, headers, file. Methods: awrite, aread, aseek, asave, aclose.

4. Dependency Injection

from kui.asgi import Depends

# Simple dependency
async def get_db():
    return db_pool.acquire()

# Generator dependency (with cleanup)
async def get_connection():
    conn = await db_pool.acquire()
    try:
        yield conn
    finally:
        await conn.release()

@app.router.http.get("/")
async def handler(
    conn: Annotated[Connection, Depends(get_connection)],
):
    return await conn.fetch("SELECT 1")

• cache=True (default): result cached per request; same dependency injected once even if declared multiple times.
• cache=False: called fresh each time.
• Dependencies can declare their own Annotated parameters (nested injection).
• Both sync and async dependencies work. Generators and async generators are supported for setup/teardown.

5. Class-Based Views

HttpView

from kui.asgi import HttpView

@app.router.http("/users")
class UserView(HttpView):
    @classmethod
    async def get(cls):
        return [{"id": 1}]

    @classmethod
    async def post(cls):
        return {"created": True}, 201

Supported methods: get, post, put, patch, delete, head, options, trace. OPTIONS auto-generated if not defined. Returns 405 for unsupported methods.

SocketView (ASGI only)

from kui.asgi import SocketView, websocket

@app.router.websocket("/chat")
class Chat(SocketView):
    encoding = "json"  # "text", "bytes", "json", "anystr"

    async def on_connect(self):
        await websocket.accept()

    async def on_receive(self, data):
        await websocket.send_json({"echo": data})

    async def on_disconnect(self, close_code: int):
        await websocket.close(code=close_code)

MultimethodRoutes

Merge multiple single-method handlers for the same path into one class-based view automatically:

from kui.asgi import MultimethodRoutes as Routes, HttpView

routes = Routes(base_class=HttpView)

@routes.http.get("/users")
async def list_users():
    return []

@routes.http.post("/users")
async def create_user():
    return {}, 201

6. Middleware

A middleware is a function (endpoint) -> new_endpoint:

def logging_middleware(endpoint):
    async def wrapper():
        print("before")
        result = await endpoint()
        print("after")
        return result
    return wrapper

Important: Do NOT use @functools.wraps on middleware wrappers. The framework raises RuntimeError if it detects this.

Apply middleware

# Per-route via decorator parameter
@app.router.http.get("/", middlewares=[logging_middleware])
async def handler(): ...

# Per-route via @ operator
app.router <<= HttpRoute("/", handler) @ logging_middleware

# Per-Routes group
routes = Routes(..., http_middlewares=[logging_middleware])

# App-level
app = Kui(http_middlewares=[logging_middleware])

# Via Routes decorator
@routes.http_middleware
def mw(endpoint):
    async def wrapper():
        return await endpoint()
    return wrapper

Middleware can declare its own Annotated parameters for automatic binding:

def auth_middleware(endpoint):
    async def wrapper(token: Annotated[str, Header(alias="authorization")]):
        verify(token)
        return await endpoint()
    return wrapper

7. Response Types

Handlers can return any of these types; the framework auto-converts:

OpenAPI response documentation

Use return type annotations:

@app.router.http.get("/")
async def handler() -> Annotated[Any, JSONResponse[200, {}, UserModel]]:
    ...

# Status-only: JSONResponse[200]
# Status + headers: JSONResponse[200, {"X-Custom": {"schema": {"type": "string"}}}]
# Status + headers + body schema: JSONResponse[200, {}, UserModel]

Available: JSONResponse, HTMLResponse, PlainTextResponse, FileResponse, RedirectResponse, SendEventResponse, StreamResponse.

Server-sent events

@app.router.http.get("/events")
async def events():
    async def generate():
        for i in range(10):
            yield {"id": i, "data": "hello"}
            await asyncio.sleep(1)
    return generate()

Custom response converters

from dataclasses import dataclass

@dataclass
class Error:
    code: int
    message: str

app = Kui(
    response_converters={
        Error: lambda e, status=400, headers=None: JSONResponse(
            {"code": e.code, "message": e.message}, status, headers
        ),
    }
)

Active conversion

Use convert_response(value) to explicitly trigger the response converter pipeline outside of normal handler return flow.

8. Request & WebSocket Objects

Access via context variables (no parameter needed):

from kui.asgi import request, websocket

@app.router.http.get("/")
async def handler():
    request.method         # "GET"
    request.url            # Full URL object
    request.headers        # Headers mapping
    request.cookies        # Cookies dict
    request.path_params    # Extracted path params
    request.query_params   # Query params
    request.state          # Per-request State dict
    request.app            # The Kui instance
    await request.json     # Parse JSON body (cached property, no parentheses)
    await request.form     # Parse form body (cached property, no parentheses)
    await request.data()   # Auto-detect body format (method call)

Per-request state

request.state.user = current_user     # write
name = request.state.user.name        # read
del request.state.user                # delete

WebSocket methods (ASGI only):

await websocket.accept()
await websocket.receive_text() / .receive_bytes() / .receive_json()
await websocket.send_text(s) / .send_bytes(b) / .send_json(obj)
await websocket.close(code=1000)

9. OpenAPI Documentation

from kui.asgi import OpenAPI, Routes

openapi = OpenAPI(
    info={"title": "My API", "version": "1.0.0"},
    template_name="swagger",  # "swagger" | "redoc" | "rapidoc"
    reload=True,
)
app.router <<= "/docs" // openapi.routes

Serves:

• GET /docs/ -- Interactive HTML UI
• GET /docs/json -- OpenAPI 3.1.0 JSON schema
• GET /docs/heartbeat -- SSE for hot reload

Documentation is auto-generated from:

• Handler docstrings (first paragraph = summary, rest = description)
• summary=, description=, tags= parameters on routes
• Annotated parameter types (Path, Query, Header, Cookie, Body)
• Return type annotations with response classes
• Dependency functions

Extra documentation

Use describe_extra_docs to supplement OpenAPI docs for a specific endpoint. The descriptions will be merged into the generated documentation.

Custom Content-Type

Override HttpRequest.data() with a ContentType annotation to change the documented request Content-Type:

from typing import Any
from typing_extensions import Annotated
from baize.datastructures import ContentType
from kui.asgi import HttpRequest, FactoryClass, Kui

class MsgPackRequest(HttpRequest):
    async def data(self) -> Annotated[Any, ContentType("application/x-msgpack")]:
        ...

app = Kui(factory_class=FactoryClass(http=MsgPackRequest))

10. Exception Handling

from kui.asgi import HTTPException

# Raise in handlers
raise HTTPException(404)
raise HTTPException(403, content="Forbidden", headers={"X-Reason": "auth"})

# Register handlers
@app.exception_handler(404)
async def not_found(exc):
    return {"error": "not found"}, 404

@app.exception_handler(ValueError)
async def value_error(exc):
    return {"error": str(exc)}, 400

Validation errors return 422 by default. Path validation errors return 404.

11. Authentication

from kui.asgi import Depends, bearer_auth, basic_auth, api_key_auth_dependency

# Bearer token: Authorization: Bearer <token>
@app.router.http.get("/me")
async def me(token: Annotated[str, Depends(bearer_auth)]):
    return decode_jwt(token)

# Basic auth: Authorization: Basic <base64>
@app.router.http.get("/admin")
async def admin(creds: Annotated[tuple[str, str], Depends(basic_auth)]):
    username, password = creds
    ...

# API key from header/query/cookie
api_key = api_key_auth_dependency("X-API-Key", position="header")

@app.router.http.get("/data")
async def data(key: Annotated[str, Depends(api_key)]):
    ...

All raise HTTPException(401) with appropriate WWW-Authenticate headers when auth fails. OpenAPI security schemes are auto-documented.

12. CORS

import re
from kui.asgi import allow_cors, Kui

# App-level
app = Kui(cors_config={
    "allow_origins": [re.compile(r"https://example\.com")],
    "allow_methods": ["GET", "POST"],
    "allow_headers": [],
    "expose_headers": [],
    "allow_credentials": False,
    "max_age": 600,
})

# Per-route
cors = allow_cors(allow_origins=[re.compile(".*")])
app.router <<= HttpRoute("/api", handler) @ cors

13. Lifespan (ASGI only)

Pass an async generator function to Kui(lifespan=...). Code before yield runs on startup; code after yield runs on shutdown:

async def lifespan(app: Kui):
    app.state.pool = await create_pool()
    yield
    await app.state.pool.close()

app = Kui(lifespan=lifespan)

on_startup/on_shutdown and asynccontextmanager_lifespan are deprecated.

14. Background Tasks

from kui.asgi import request

@app.router.http.post("/notify")
async def notify():
    request.background_tasks.append(send_email, to="user@example.com")
    return {"status": "queued"}

async def send_email(to: str):
    ...

Background tasks run after the response is sent.

15. Templates (Jinja2)

from kui.asgi import Jinja2Templates, TemplateResponse, request

templates = Jinja2Templates("templates")
app = Kui(templates=templates)

@app.router.http.get("/")
async def homepage():
    return TemplateResponse("index.html", {"request": request, "name": "World"})

16. Advanced

Custom factory classes

from kui.asgi import Kui, FactoryClass, HttpRequest, WebSocket

class CustomRequest(HttpRequest): ...
class CustomWS(WebSocket): ...

app = Kui(factory_class=FactoryClass(http=CustomRequest, websocket=CustomWS))

Custom JSON encoder

from datetime import datetime
app = Kui(json_encoder={datetime: lambda dt: dt.isoformat()})

app.should_exit

Set app.should_exit = True to signal graceful shutdown (requires server support).

Complete Example

import asyncio
from pathlib import Path as FilePath
from typing_extensions import Annotated

from kui.asgi import (
    Kui, OpenAPI, HttpRoute, SocketRoute,
    Path, Query, Body, Depends,
    HTTPException, HttpView,
    allow_cors, required_method, websocket,
)
from pydantic import BaseModel

class Item(BaseModel):
    name: str
    price: float

items_db: list[Item] = []

async def get_items_db():
    return items_db

app = Kui(
    routes=[
        HttpRoute("/", lambda: "Welcome to Kui!"),
    ],
    http_middlewares=[allow_cors()],
)

@app.router.http.get("/items")
async def list_items(
    skip: Annotated[int, Query(0)],
    limit: Annotated[int, Query(10)],
    db: Annotated[list, Depends(get_items_db)],
):
    return db[skip:skip + limit]

@app.router.http.post("/items")
async def create_item(
    item: Annotated[Item, Body(exclusive=True)],
    db: Annotated[list, Depends(get_items_db)],
):
    db.append(item)
    return item, 201

app.router <<= "/docs" // OpenAPI(template_name="swagger").routes

Source: abersheeran/kui — distributed by TomeVault.