PyLage

PyLage is a server-driven differential UI framework for Python.

Build interactive web applications using pure Python components, reactive state, routing, styling, themes, events, and live browser synchronization — without writing a separate frontend application.

import pylage as pl

count = pl.state(0)

def increment():
    count.set(count.value + 1)

app = pl.column(
    pl.heading("Hello PyLage"),
    pl.text(count),
    pl.button("Increment", on_click=increment),
)

pl.run(app)

Why PyLage?

PyLage keeps your application logic in Python while delivering a reactive browser UI.

Python Application
        │
        ▼
     PyLage
        │
        ├── Components
        ├── Reactive State
        ├── Layout
        ├── Styling & Themes
        ├── Events
        ├── Routing
        └── Differential UI Updates
                │
                ▼
             Browser

The browser communicates with the Python runtime over WebSocket. Updates are sent as targeted differential patches instead of full page rebuilds.

Features

• Python-first UI development
• Server-driven architecture
• Reactive state management
• Differential browser updates
• WebSocket-based live synchronization
• Component-based composition
• Layout primitives (row, column, etc.)
• Event handling
• Input binding
• Routing & navigation
• Styling API + style overrides
• Light & dark themes
• Responsive support
• Interactive Playground
• CLI support
• Python 3.10+
• Comprehensive test suite + browser verification

Installation

Requires Python 3.10+.

pip install pylage

For development and browser testing:

pip install "pylage[test]"

Core runtime dependencies:

• websockets >= 10.0
• granian >= 2.7.4
• msgpack >= 1.0.7

Quickstart

import pylage as pl

app = pl.column(
    pl.heading("Hello PyLage"),
    pl.text("A server-driven UI built entirely in Python."),
    pl.button("Click me"),
)

pl.run(app)

Import everything from the root package:

import pylage as pl

Common public APIs:

pl.column(...)
pl.row(...)
pl.text(...)
pl.heading(...)
pl.button(...)
pl.input(...)
pl.state(...)
pl.style(...)
pl.set_theme(...)
pl.get_current_theme(...)
pl.run(...)

Reactive State

import pylage as pl

count = pl.state(0)

def increment():
    count.set(count.value + 1)

app = pl.column(
    pl.heading("Counter"),
    pl.text(count),
    pl.button("Increment", on_click=increment),
)

pl.run(app)

When state changes, PyLage automatically tracks affected UI and sends only the required differential updates to the browser.

Components & Layout

import pylage as pl

app = pl.column(
    pl.heading("Dashboard"),
    pl.text("Welcome to PyLage"),
    pl.row(
        pl.button("Save"),
        pl.button("Cancel"),
    ),
)

pl.run(app)

Components support nesting, properties, event handlers, reactive values, and recursive layout composition.

Events

import pylage as pl

message = pl.state("Waiting...")

def save():
    message.set("Saved")

app = pl.column(
    pl.text(message),
    pl.button("Save", on_click=save),
)

pl.run(app)

Flow:

Browser Event → WebSocket → Python Handler → State Change → Differential Patch → Browser

Inputs & Binding

import pylage as pl

name = pl.state("")

app = pl.column(
    pl.heading("Profile"),
    pl.input(value=name),
    pl.text(name),
)

pl.run(app)

Routing

PyLage includes built-in routing for multi-view applications with navigation, browser history support, and reactive route state — all within the same server-driven model.

Styling & Themes

import pylage as pl

pl.set_theme("dark")

app = pl.column(
    pl.heading("Styled UI"),
    pl.button(
        "Save",
        style=pl.style(padding="1rem"),
    ),
)

pl.run(app)

Inspect the active theme:

pl.get_current_theme()

Architecture

Python Application
       │
       ▼
Component Tree
       │
       ▼
Reactive Runtime
       │
       ▼
Differential Update
       │
       ▼
WebSocket
       │
       ▼
Browser

Only the necessary changes are transmitted.

Playground

PyLage ships with a public Playground for interactive exploration of components, reactive behavior, and the public API.

CLI

pylage

Development

git clone https://github.com/aanalyst-rachit/pylage.git
cd pylage

python3 -m venv .venv
source .venv/bin/activate

pip install -e ".[test]"

Testing

# Full suite
pytest

# Browser tests
pytest test/browser -q

# Focused
pytest test/reactive -q

Current verification baseline:

• 1326 tests collected
• 1325 passed
• 1 skipped

Additional tooling: Ruff, Playwright, package build verification, dependency auditing.

Documentation

Documentation lives in docs/ and is built with MkDocs:

mkdocs build

Key pages:

• docs/index.md
• docs/first_app.md
• docs/deployment.md

Project Structure

pylage/
├── pylage/
│   ├── ENGINE/
│   ├── UI/
│   ├── __init__.py
│   └── cli.py
├── docs/
├── playground/
├── demo/
├── test/
├── scripts/
├── .github/
├── CHANGELOG.md
├── Dockerfile
├── mkdocs.yml
├── pyproject.toml
├── README.md
└── tracker.md

Deployment

See docs/deployment.md for production server configuration and deployment guidance.

Release Status

• Current release: PyLage 1.0.3
• Release status: Public release preparation complete

Release process includes full public API audit, documentation & playground verification, package builds, fresh-install checks, and regression testing.

License

This project is licensed under the Apache License 2.0.

See the LICENSE file for the full license text.

Links

• Repository: https://github.com/aanalyst-rachit/pylage
• PyPI: https://pypi.org/project/pylage/
• Issues: https://github.com/aanalyst-rachit/pylage/issues
• Playground: https://aanalyst-rachit.github.io/pylage/playground/
• Docs: https://aanalyst-rachit.github.io/pylage/

Contributing

Contributions, bug reports, and documentation improvements are welcome.

Before submitting:

pytest
ruff check .
git diff --check