Show and tell: Lanes – A Flask‑like async web framework for MicroPython (now on uPyPi)

[SeaMite43981045]

TL;DR: Lanes is a lightweight, asynchronous web framework for MicroPython with a familiar Flask‑like API. It now has a package on uPyPi – you can install it directly onto your device with mip 🚀

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Hi everyone 👋,

I’m excited to share a project I’ve been working on: Lanes – a web framework for MicroPython designed to run efficiently on resource‑constrained devices like the ESP32, ESP8266, and RP2040.

It was built because I wanted a simple, Flask‑like way to build web interfaces and REST APIs directly on my IoT devices, without needing a separate server.

✨ Features

• Async from the ground up – Built on asyncio for concurrent request handling.
• Familiar Flask‑like syntax – @app.get(), @app.post(), etc.
• Dynamic routing – Extract URL parameters: /user/:id
• Blueprint support – Modularise larger applications.
• Middleware support – Run code before each request.
• Static file serving – Serve CSS, JS, images from any folder.
• Cookie handling – Set and read cookies easily.
• JSON auto‑serialisation – Return dict / list as JSON.
• Tiny memory footprint – Works with ~300KB free heap on ESP32.

📦 Installation

Thanks to uPyPi, you can now install Lanes with a single line:

Remote install (inside REPL):

import mip
mip.install("github:SeaMite43981045/Lanes-esp")

Local install (using mpremote):

mpremote mip install github:SeaMite43981045/Lanes-esp

Or simply copy lanes.py to your device's /lib folder.

🚀 Quick Start

import lanes

app = lanes.Lanes()

@app.get('/')
def index(req):
    return "Hello, Lanes!"

@app.get('/user/:name')
def greet_user(req, name):
    return {"message": f"Hello, {name}!"}

app.run(host='0.0.0.0', port=80)

🔧 Status & Roadmap

The current release is 1.0.0-pre – stable for development and experimental on some boards.

Next steps:

• urlencoded form parsing
• Proper Content‑Length for static files
• Security hardening for static file serving
• Full error handler support

I’d love your help with: testing on different devices, feedback on the API, and contributions (especially on the items above!)

🔗 Links

• uPyPi package: https://upypi.net/en/pkgs/lanes/1.0.0-pre
• GitHub repository: https://github.com/SeaMite43981045/Lanes-esp
• Documentation: see the README on GitHub

I’d really appreciate any feedback, bug reports, or ideas. If you end up using Lanes in one of your projects, I’d love to hear about it!

Thanks for reading 🙏

[mattytrentini]

Congrats on releasing!

However, I can't use mip to install; there's an error in your package.json (each url should have two items).

Also, the https://upypi.net/pkgs/lanes/1.0.0-pre URL is a 404.

Finally, the community has a popular flask-like alternative in microdot; I, for one, would really appreciate having a comparison - what are the unique features of your library?

[SeaMite43981045]

Before we begin, thank you very much for your feedback!

Also, I'm sorry about there's an error in my package.json, I'll fix it just later. ( Forgive me, this is the first library I uploaded to uPyPI :) )

Regarding the issue of the 404 URL, I can access it through https://upypi.net/en/pkgs/lanes/1.0.0-pre (don't forget the en before /pkgs), and if it still doesn't work, I will try to fix this problem.

Framework Comparison: Lanes vs. Microdot

Feature / Dimension	Lanes (This Project)	Microdot
Design Philosophy & Focus	Hyper-focused on providing a blazing-fast, lightweight API backend for SPA (Single Page Applications) and IoT control interfaces.	A versatile, Flask-like micro-framework designed to handle a broad spectrum of tasks, from HTML rendering to general APIs.
Routing Engine	Utilizes highly efficient string-splitting for route matching and :id parameter extraction. This drastically reduces RAM usage and CPU overhead, though it lacks the flexibility of Regex or strict type casting.	Uses Regex-compiled URLPattern matching, offering powerful dynamic segments and type casting (e.g., int:id) at the cost of higher memory consumption.
Request & Memory Model	Implements strict lowercase dictionaries for headers and streamlined parsing. This actively minimizes garbage collection (GC) overhead on microcontrollers, but requires developers to handle specific tasks like URL decoding manually.	Features rich NoCaseDict and MultiDict structures with automatic URL decoding. It provides a highly forgiving developer experience but has a significantly heavier memory footprint.
Handler Concurrency	Business callbacks are executed synchronously by default, keeping the API surface extremely simple and predictable, though developers must be cautious not to block the event loop with heavy blocking tasks.	Native support for mixed programming. The framework automatically detects and awaits async coroutines while still supporting synchronous handlers.
Modularity & Grouping	Features an intuitive Blueprint system (similar to Sanic/Flask) that merges routes before server startup, providing excellent developer ergonomics for organizing complex APIs.	Relies on a sub-application mounting pattern (app.mount()) to group routes, rather than dedicated blueprint objects.
Middleware & State Sharing	Streamlined before_request interceptors combined with a built-in req.ctx dictionary. This makes it exceptionally fast for JWT/Auth state sharing, though it intentionally omits post-request modification hooks.	Comprehensive lifecycle hooks including before_request, after_request, and after_error_request for deep and complex response modifications.
Error Handling (developing)	Direct, lightweight HTTP status code capturing via @app.error_handler (e.g., globally catching 404 or 500 status codes).	Advanced exception capturing that walks up the Python Method Resolution Order (MRO) to handle specific Python Exception classes (e.g., ValueError).

I would be very grateful if you could give me more feedback or give me a star :)

[mattytrentini]

I see you've updated the uPyPi link (to include an 'en') and you've also updated package.json. Unfortunately your install instructions still fail:

And if you're going to use AI tooling to do a comparison like that fine, but please review it. There are a lot of (dramatic!) words there with little meaning; it's a poor comparison and I still don't understand the goals of the library, particularly given that other alternatives exist.

The kind of comparison I'd like to see: "Microdot has a flexible routing system but I wanted lanes to use less memory so I've chosen a method that is more constrained. Here are the memory use measurements over x requests...".

[SeaMite43981045]

I am really sorry, I will revise it carefully.

[SeaMite43981045]

I have corrected my package.json file, and now you can install Lanes using mip.install("github:SeaMite43981045/Lanes-esp")!

[andypiper]

Why wouldn’t I mip install from GitHub instead of uPyPi - I thought mip was its own package manager and index?

[SeaMite43981045]

You’re right that mip is MicroPython’s package manager – it works like pip.
However, mip itself doesn’t host packages; it needs an index to fetch them from.
By default, mip uses uPyPi (the official MicroPython package index), just like pip uses PyPI.

The ability to install directly from GitHub is an additional feature, not a replacement for uPyPi. You would use GitHub instead of uPyPi when:

1. You want the latest development version (e.g., a commit that hasn’t been published to uPyPi yet).
2. You’re testing your own library that hasn’t been uploaded to uPyPi.
3. You need a specific branch or fork that isn’t available on uPyPi.

So, mip is the tool, uPyPi is the default index, and GitHub is an alternative source for edge cases. They serve different purposes and both are useful depending on your workflow.

[mattytrentini]

This is almost entirely incorrect.

mip does not use uPyPi by default and it is most certainly not the official MicroPython package index. As far as I am aware, uPyPi has nothing to do with the MicroPython team or project.

Installing from GitHub was the first supported source for mip. uPyPi is only tangentially supported because mip allows using direct URLs. No-one has even submitted a PR to extend mip to use 'upypi:' syntax that currently exists for GitHub, GitLab and Codeberg. See the docs for more details.

[SeaMite43981045]

Thanks for clearing that up and correcting my misunderstanding. I appreciate you taking the time to explain the history and the actual layout of mip—it makes total sense now. I'll make sure to check out the docs to get properly up to speed.

[SeaMite43981045]

I have now corrected my mistake and look forward to more of your feedback :)