qh

Quick HTTP web-service construction - From Python functions to production-ready HTTP services, with minimal boilerplate.

qh (pronounced "quick") is a convention-over-configuration framework for exposing Python functions as HTTP services. Built on FastAPI, it provides a delightfully simple API while giving you escape hatches for advanced use cases.

pip install qh

For AI agents

qh publishes its documentation in forms made for coding agents. If you are one, start here.

The documentation, machine-readable: llms.txt indexes every page; qh.md is the whole documentation in one file; every page has a .md twin; objects.inv maps symbols to URLs.

If you can't let go of the old ways, the rest of this README is written for you, starting at Quickstart: From Function to API in 3 Lines.

Quickstart: From Function to API in 3 Lines

from qh import mk_app


def add(x: int, y: int) -> int:
    return x + y


app = mk_app([add])

That's it! You now have a FastAPI app with:

• ✅ Automatic request/response handling
• ✅ Type validation from your annotations
• ✅ OpenAPI documentation at /docs
• ✅ Multiple input formats (JSON body, query params, etc.)

Run it:

uvicorn your_module:app

Or test it:

from qh.testing import test_app

with test_app(app) as client:
    response = client.post("/add", json={"x": 3, "y": 5})
    print(response.json())  # 8

What You Can Do From Here

🚀 Async Task Processing (NEW in v0.5.0)

Handle long-running operations without blocking:

import time


def expensive_computation(n: int) -> int:
    time.sleep(5)  # Simulate heavy processing
    return n * 2


# Enable async support
app = mk_app([expensive_computation], async_funcs=["expensive_computation"])

Now clients can choose sync or async execution:

# Synchronous (blocks for 5 seconds)
POST /expensive_computation?n=10
→ 20

# Asynchronous (returns immediately)
POST /expensive_computation?n=10&async=true
→ {"task_id": "abc-123", "status": "submitted"}

# Check status
GET /tasks/abc-123/status
→ {"status": "running", "started_at": 1234567890}

# Get result (blocks until ready, or returns immediately if done)
GET /tasks/abc-123/result?wait=true&timeout=10
→ {"status": "completed", "result": 20}

Advanced async configuration:

from qh import mk_app, TaskConfig, ProcessPoolTaskExecutor

app = mk_app(
    [cpu_bound_func, io_bound_func],
    async_funcs=["cpu_bound_func", "io_bound_func"],
    async_config={
        "cpu_bound_func": TaskConfig(
            executor=ProcessPoolTaskExecutor(
                max_workers=4
            ),  # Use processes for CPU-bound
            ttl=3600,  # Keep results for 1 hour
        ),
        "io_bound_func": TaskConfig(
            async_mode="always",  # Always async, no query param needed
        ),
    },
)

Task management endpoints are automatically created:

• GET /tasks/ - List all tasks
• GET /tasks/{id} - Get complete task info
• GET /tasks/{id}/status - Get task status
• GET /tasks/{id}/result - Get result (with optional wait)
• DELETE /tasks/{id} - Cancel/delete task

📝 Convention-Based Routing

def get_user(user_id: str):
    return {"id": user_id, "name": "Alice"}


def list_users():
    return [{"id": "1", "name": "Alice"}]


def create_user(name: str, email: str):
    return {"id": "123", "name": name, "email": email}


app = mk_app([get_user, list_users, create_user], use_conventions=True)

This automatically creates RESTful routes:

• GET /users/{user_id} → get_user(user_id)
• GET /users → list_users()
• POST /users → create_user(name, email)

🎯 Explicit Configuration

from qh import mk_app, RouteConfig


def add(x: int, y: int) -> int:
    return x + y


app = mk_app(
    {
        add: RouteConfig(
            path="/calculate/sum",
            methods=["GET", "POST"],
            tags=["math"],
            summary="Add two numbers",
        )
    }
)

Or use dictionaries:

app = mk_app(
    {
        add: {
            "path": "/calculate/sum",
            "methods": ["GET", "POST"],
        }
    }
)

🔄 Parameter Transformation

import numpy as np
from qh import mk_app, RouteConfig, TransformSpec, HttpLocation


def add_arrays(a, b):
    return (a + b).tolist()


app = mk_app(
    {
        add_arrays: RouteConfig(
            param_overrides={
                "a": TransformSpec(
                    http_location=HttpLocation.JSON_BODY,
                    ingress=np.array,  # Convert JSON array to numpy
                ),
                "b": TransformSpec(
                    http_location=HttpLocation.JSON_BODY, ingress=np.array
                ),
            }
        )
    }
)

Now you can send:

POST /add_arrays
{"a": [1,2,3], "b": [4,5,6]}
→ [5, 7, 9]

🌐 OpenAPI & Client Generation

from qh import mk_app, export_openapi, mk_client_from_app


def greet(name: str) -> str:
    return f"Hello, {name}!"


app = mk_app([greet])

# Export OpenAPI spec
export_openapi(app, "api.json")

# Generate Python client
client = mk_client_from_app(app)
result = client.greet(name="World")  # "Hello, World!"

# Generate TypeScript client
from qh import export_ts_client

export_ts_client(app, "client.ts")

🎨 Custom Types

from qh import register_type
from datetime import datetime


def custom_serializer(dt: datetime) -> str:
    return dt.isoformat()


def custom_deserializer(s: str) -> datetime:
    return datetime.fromisoformat(s)


register_type(datetime, serialize=custom_serializer, deserialize=custom_deserializer)


def get_event_time(event_id: str) -> datetime:
    return datetime.now()


app = mk_app([get_event_time])

⚙️ Global Configuration

from qh import mk_app, AppConfig

app = mk_app(
    funcs=[add, multiply, divide],
    config=AppConfig(
        path_prefix="/api/v1",
        default_methods=["POST"],
        title="Math API",
        version="1.0.0",
    ),
)

🧪 Testing Utilities

from qh import test_app, serve_app, quick_test

# Quick inline testing
with test_app(app) as client:
    response = client.post("/add", json={"x": 3, "y": 5})
    assert response.json() == 8

# Serve for external testing
with serve_app(app, port=8001) as url:
    import requests

    response = requests.post(f"{url}/add", json={"x": 3, "y": 5})

# Quick smoke test
quick_test(app)  # Tests all endpoints with example data

Features

Built-in

• ✅ Minimal boilerplate - Define functions, get HTTP service
• ✅ Type-driven - Uses Python type hints for validation
• ✅ FastAPI-powered - Full async support, high performance
• ✅ Automatic OpenAPI - Interactive docs at /docs
• ✅ Client generation - Python, TypeScript, JavaScript clients
• ✅ Convention over configuration - RESTful routing from function names
• ✅ Flexible parameter handling - JSON, query, path, headers, forms
• ✅ Custom transformations - Transform inputs/outputs as needed
• ✅ Testing utilities - Built-in test client and helpers

Phase 4 (NEW): Async Task Processing

• ✅ Background tasks - Long-running operations without blocking
• ✅ Task tracking - Status monitoring and result retrieval
• ✅ Flexible execution - Thread pools, process pools, or custom executors
• ✅ Client-controlled - Let users choose sync vs async
• ✅ Standard HTTP patterns - Poll for status, wait for results
• ✅ Task management - List, query, cancel tasks via HTTP

Examples

Simple CRUD API

from qh import mk_app

# In-memory database
users = {}


def create_user(name: str, email: str) -> dict:
    user_id = str(len(users) + 1)
    users[user_id] = {"id": user_id, "name": name, "email": email}
    return users[user_id]


def get_user(user_id: str) -> dict:
    return users.get(user_id, {})


def list_users() -> list:
    return list(users.values())


app = mk_app([create_user, get_user, list_users], use_conventions=True)

File Processing with Async

from qh import mk_app, TaskConfig
import time


def process_large_file(file_path: str) -> dict:
    time.sleep(10)  # Simulate heavy processing
    return {"status": "processed", "path": file_path}


app = mk_app(
    [process_large_file],
    async_funcs=["process_large_file"],
    async_config=TaskConfig(
        async_mode="always",  # Always async
        ttl=3600,  # Keep results for 1 hour
    ),
)

# Client usage:
# POST /process_large_file -> Returns task_id immediately
# GET /tasks/{task_id}/result?wait=true -> Blocks until done

Mixed Sync/Async API

def quick_lookup(key: str) -> str:
    """Fast operation - always synchronous"""
    return cache.get(key)


def expensive_aggregation(days: int) -> dict:
    """Slow operation - supports async"""
    time.sleep(days * 2)
    return {"result": "..."}


app = mk_app(
    [quick_lookup, expensive_aggregation],
    async_funcs=["expensive_aggregation"],  # Only expensive_aggregation supports async
)

# quick_lookup is always synchronous
# expensive_aggregation can be called with ?async=true

Data Science API

import numpy as np
import pandas as pd
from qh import mk_app, RouteConfig, TransformSpec


def analyze_data(data: pd.DataFrame) -> dict:
    return {"mean": data.mean().to_dict(), "std": data.std().to_dict()}


app = mk_app(
    {
        analyze_data: RouteConfig(
            param_overrides={"data": TransformSpec(ingress=pd.DataFrame)}
        )
    }
)

# POST /analyze_data
# {"data": {"col1": [1,2,3], "col2": [4,5,6]}}

Philosophy

Convention over configuration, but configuration when you need it.

qh follows a layered approach:

1. Simple case - Just pass functions, get working HTTP service
2. Common cases - Use conventions (RESTful routing, type-driven validation)
3. Advanced cases - Explicit configuration for full control

You write Python functions. qh handles the HTTP layer.

Comparison

Feature	qh	FastAPI	Flask
From functions to HTTP	1 line	~10 lines	~15 lines
Type validation	Automatic	Automatic	Manual
OpenAPI docs	Automatic	Automatic	Extensions
Client generation	✅ Built-in	❌ External tools	❌ Manual
Convention routing	✅ Yes	❌ No	❌ No
Async tasks	✅ Built-in	❌ Manual setup	❌ Extensions
Task tracking	✅ Automatic	❌ Manual	❌ Manual
Learning curve	Minutes	Hours	Hours
Suitable for production	Yes (it's FastAPI!)	Yes	Yes

Under the Hood

qh is built on:

• FastAPI - Modern, fast web framework
• i2 - Function signature manipulation
• Pydantic - Data validation

When you create an app with qh, you get a fully-featured FastAPI application. All FastAPI features are available.

Advanced Topics

Using au Package (External Async Backend)

The built-in async functionality is perfect for most use cases, but if you need distributed task processing, you can integrate with au:

pip install au

from au import async_compute, RQBackend
from qh import mk_app, TaskConfig


# Configure au with Redis backend
@async_compute(backend=RQBackend("redis://localhost:6379"))
def heavy_computation(n: int) -> int:
    return n * 2


# Use with qh
app = mk_app([heavy_computation])
# Now heavy_computation can be distributed across multiple workers

Custom Task Executors

from qh import TaskExecutor, TaskConfig
from concurrent.futures import ThreadPoolExecutor


class MyCustomExecutor(TaskExecutor):
    def __init__(self):
        self.pool = ThreadPoolExecutor(max_workers=10)

    def submit_task(self, task_id, func, args, kwargs, callback):
        # Custom task submission logic
        def wrapper():
            try:
                result = func(*args, **kwargs)
                callback(task_id, result, None)
            except Exception as e:
                callback(task_id, None, e)

        self.pool.submit(wrapper)

    def shutdown(self, wait=True):
        self.pool.shutdown(wait=wait)


app = mk_app(
    [my_func],
    async_funcs=["my_func"],
    async_config=TaskConfig(executor=MyCustomExecutor()),
)

Middleware and Extensions

Since qh creates a FastAPI app, you can use all FastAPI features:

from qh import mk_app
from fastapi.middleware.cors import CORSMiddleware

app = mk_app([my_func])

# Add CORS
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_methods=["*"],
    allow_headers=["*"],
)


# Add custom routes
@app.get("/health")
async def health():
    return {"status": "healthy"}

Migration Guide

From v0.4.0 to v0.5.0

The async task feature is fully backward compatible. Existing apps will work without changes.

To enable async:

# Old (still works)
app = mk_app([my_func])

# New (with async support)
app = mk_app([my_func], async_funcs=["my_func"])

Contributing

We welcome contributions! See CONTRIBUTING.md for guidelines.

License

Apache 2.0

Links

• Documentation: https://github.com/i2mint/qh
• Source Code: https://github.com/i2mint/qh
• Issue Tracker: https://github.com/i2mint/qh/issues
• Related Projects:
  • i2 - Function signature manipulation
  • au - Async utilities for distributed computing
  • FastAPI - The underlying web framework

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Made with ❤️ by the i2mint team