Picolet

Compile a Python program into a small self-contained native executable. Like PyInstaller, but the binary is hundreds of kilobytes rather than tens of megabytes, starts in milliseconds, and has no runtime Python dependency on the host.

The shape of it

A Picolet binary is one file. Inside:

• A trimmed MicroPython interpreter (~410–650 KB depending on renderer).
• Your application's .py code, compiled to bytecode and frozen into the binary.
• Optional bundled assets (HTML, fonts, images, schemas) as a read-only ROM filesystem appended to the executable.
• Optionally: a GUI renderer (system webview or native LVGL) for HTML/JS or native UIs.

The result runs on any matching-OS/arch machine without installing Python.

Three ways to use it

1. Bundle a single CLI script

The simplest case:

picolet build hello.py
./hello                # Linux  ≈ 647 KB
./hello.exe            # Windows ≈ 409 KB

hello.py becomes a self-contained executable. Sub-second startup. No python interpreter needed on the host machine. Roughly 20–50× smaller than the equivalent PyInstaller bundle, with no first-launch unpacking delay.

2. Manifest-driven build

For multi-module apps, drive the build from a MicroPython manifest.py:

# manifest.py
require("argparse")                   # frozen micropython-lib module
require("typing")
freeze("./src", "main.py")            # your entry
freeze("./src/lib", "utils.py")       # additional modules
freeze("./src/lib", "data_model.py")

picolet build --manifest manifest.py

The manifest is the canonical MicroPython mechanism for declaring what's frozen into a build. Picolet uses it directly — everything declared is included.

Medium-term: romfs contents (HTML, fonts, etc.) declared in the same manifest, per upstream evolution.

3. GUI application

Add a picolet.toml to pick a renderer and bundle UI assets:

[app]
name = "my-app"
entry = "src/main.py"

[ui]
renderer = "webview"            # or "lvgl" for native
root = "ui"

[window]
title = "My App"
size = [900, 600]

[romfs]
include = ["ui", "assets"]

picolet build

For Vue or other JS framework frontends:

[ui.frontend]
framework = "vue"               # builds Vite output into romfs automatically

The IPC bridge is set up automatically:

// JS side
await window.picolet.invoke('list_items', { filter: 'active' });
window.picolet.on('progress', e => bar.update(e.pct));

# Python side
@picolet.command
async def list_items(args):
    return [...]

Four worked examples under examples/ (pydfu, notes, config-editor, dashboard) demonstrate the patterns end-to-end, each with a distinct visual aesthetic.

Caveats

Read these before adopting.

• MicroPython, not CPython. The standard library subset is smaller. Pure-Python code using os, sys, json, re, time, asyncio, struct, io etc. typically works. Code that depends on C extensions (numpy, pandas, Pillow, lxml, etc.) does not. Picolet cannot make a CPython library "just work" — it would have to be ported or replaced with a MicroPython equivalent.

• micropython-lib fills most stdlib gaps. Modules like argparse, pathlib, dataclasses, typing, unittest are available via micropython-lib and are declared with require("name") in the manifest.

• Custom C modules are straightforward. A Picolet binary is a MicroPython build under the hood, so any C module written against the standard MicroPython API works. Drop a directory under user_c_modules/ and reference it in the manifest. Once upstream PR #18229 lands in the fork, c_module("./path/to/mymodule") can declare it directly in the manifest.

• Python C-API extensions (CPython .so/.pyd) do NOT work. MicroPython's runtime is binary-incompatible with CPython. Write a MicroPython C module instead.

• Async semantics differ slightly. MicroPython's asyncio is a subset of CPython's. Coroutines, tasks, queues, locks, gather, wait_for work; asyncio.run with policies, debug mode, the loop.add_signal_handler interface, and some niche APIs don't. Most app code is unaffected.

• First-class platform support is Linux x64 and Windows x64. macOS (Intel + Apple Silicon) is source-complete but requires GitHub Actions CI for native builds — local cross-compile from Linux is not supported. ARM Linux and mobile platforms are on the backlog.

See docs/caveats.md for a full catalogue.

Toolchain expectations

• The picolet CLI runs on Linux, macOS, or Windows (host).
• Building Windows binaries from Linux uses dockcross; Docker is required for that path.
• Building macOS binaries uses GitHub Actions runners (macos-13 Intel, macos-14 Apple Silicon).
• Node.js + npm are required only when building Vue/React frontends.

Getting started

Install the CLI. uv tool install is the recommended path (no separate package manager needed if you already use uv); pipx is the fallback for environments without uv. Plain pip install is deliberately not listed — most modern distros (PEP 668) block it system-wide.

uv tool install picolet-cli                       # recommended
# or:
pipx install picolet-cli                          # fallback

picolet init my-app --template hello-cli          # see --list-templates for the full set
cd my-app
picolet dev                                        # live rebuild on file changes
picolet build                                      # produce target/<os-arch>/my-app[.exe]

Templates: hello-cli, hello-webview, hello-lvgl, hello-vue, pydfu, notes, config-editor, dashboard.

Examples gallery

pydfu DFU firmware flasher (industrial control-panel aesthetic)	notes Markdown notes (editorial / refined)
config-editor Schema-driven TOML/YAML/JSON editor (brutalist terminal)	dashboard Live system metrics (data-dense)

See docs/examples.md for a longer tour of each.

Renderers

Repository layout

picolet/
├── packages/
│   ├── picolet-cli/         # picolet init|dev|build|run|test
│   ├── picolet-runtime/     # the MicroPython runtime + variants + user_c_modules
│   ├── picolet-bridge-js/   # JS shim: window.picolet.invoke(...)
│   ├── picolet-templates/   # `picolet init --template <name>` starter packs
│   └── picolet-testing/     # AppHarness for autonomous test/screenshot
├── examples/              # four worked example apps
├── tests/                 # per-phase test suites
└── docs/                  # architecture, caveats, examples, CLI reference

More

• Getting started — step-by-step tutorial
• manifest.py guide — declaring frozen modules + require() from micropython-lib and community packages
• Architecture — design decisions
• Caveats — MicroPython compatibility reference
• Examples tour — what each example app demonstrates
• CLI reference — every picolet subcommand
• SBOM — supply-chain documentation
• History — phase artefacts and version-specific specs/plans/audits

License

MIT throughout. See LICENSE.