tessl/pypi-brython

Python-to-JavaScript transpiler that enables Python 3 development in web browsers with full DOM integration and standard library support

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Brython

Name: tessl/pypi-brython
Author: tessl

Brython (Browser Python) is a Python-to-JavaScript transpiler that enables Python 3 development directly in web browsers. It provides a complete Python 3 runtime environment with full DOM integration, event handling, and access to browser APIs, eliminating the need for server-side Python execution for client-side web application logic.

Package Information

Package Name: brython
Package Type: PyPI (Python) and npm (JavaScript)
Language: Python (runtime in JavaScript)
Installation: pip install brython
Browser CDN: https://cdn.jsdelivr.net/npm/brython@3.13.2/brython.min.js

Core Imports

Browser-side Python imports:

from browser import document, window, console, alert
from browser.html import DIV, P, A, INPUT, BUTTON

CLI usage:

import brython
# Access via brython-cli command-line tool

Basic Usage

HTML Setup:

<!DOCTYPE html>
<html>
<head>
    <script src="https://cdn.jsdelivr.net/npm/brython@3.13.2/brython.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/brython@3.13.2/brython_stdlib.js"></script>
</head>
<body onload="brython({debug: 1})">
    <div id="output"></div>
    <button id="click-me">Click Me</button>
    
    <script type="text/python">
    from browser import document, bind
    from browser.html import P
    
    # DOM manipulation
    document["output"] <= P("Hello from Python!")
    
    # Event handling
    @bind(document["click-me"], 'click')
    def handle_click(event):
        document["output"] <= P("Button clicked!")
    </script>
</body>
</html>

Local Development Setup:

# Install Brython CLI
pip install brython

# Initialize new project
mkdir my-brython-app
cd my-brython-app
brython-cli install

# Start development server
brython-cli start_server 8000

Architecture

Brython consists of several key components:

CLI Tools: Project initialization, package management, and development server
Runtime Engine: JavaScript-based Python 3 interpreter running in browsers
Browser Module: Python interface to DOM, events, and browser APIs
Standard Library: Browser-compatible versions of Python standard modules
UI Framework: Widget-based GUI toolkit for web applications

This architecture enables full-stack Python development where client-side logic runs as Python in the browser while maintaining compatibility with existing JavaScript libraries and browser APIs.

Capabilities

CLI Development Tools

Command-line interface for managing Brython projects, installing packages, creating distributions, and running development servers.

# Main CLI commands accessed via brython-cli
def install(install_dir=".", no_demo=False): ...
def update(update_dir="."): ...
def add_package(package, dest_dir=None): ...
def make_package(package_name, src_dir=".", exclude_dirs=None, output_path=None): ...
def make_modules(output_path=None, reset=False, modules_paths=None): ...
def start_server(port=8000, bind="localhost"): ...

CLI Tools

Browser Runtime Engine

JavaScript-based Python interpreter that executes Python 3 code in web browsers with full language support.

function brython(options?: BrythonOptions): void;
function $B.runPythonSource(src: string, options?: RunOptions): any;
function $B.py2js(src: string, module: string, locals_id?: string, parent_scope?: any): string;

Runtime Engine

DOM and Browser Integration

Python interface to HTML DOM elements, events, and browser APIs with Pythonic syntax and full browser functionality access.

# Core browser objects
browser.document: DOMDocument
browser.window: BrowserWindow  
browser.console: Console

# Event binding decorator
def bind(element: Element, event: str, options: dict = None) -> Callable: ...

# Template engine for dynamic HTML
class Template:
    def __init__(self, element: Element | str, callbacks: list = None): ...
    def render(self, **kwargs) -> None: ...

Browser Integration

HTML Element Creation

Python classes for all HTML5 elements with attribute management, styling, and event handling capabilities.

class DIV(Element): ...
class P(Element): ...
class A(Element): ...
class BUTTON(Element): ...
class INPUT(Element): ...
class FORM(Element): ...
class TABLE(Element): ...
# ... all HTML5 elements available

HTML Elements

AJAX and Networking

HTTP request handling with Python-friendly interfaces for web service communication and data exchange.

class Ajax:
    def __init__(self): ...
    def bind(self, event: str, callback: Callable) -> Ajax: ...
    def open(self, method: str, url: str, async_: bool = True) -> None: ...
    def send(self, data: Any = None) -> None: ...

AJAX and Networking

Storage and Data Persistence

Browser storage APIs including localStorage, sessionStorage, and IndexedDB with Python interfaces.

class LocalStorage:
    def __getitem__(self, key: str) -> str: ...
    def __setitem__(self, key: str, value: str) -> None: ...
    def __delitem__(self, key: str) -> None: ...

class IndexedDB:
    def __init__(self, name: str, version: int = 1): ...
    def open(self) -> None: ...
    def transaction(self, stores: list, mode: str = 'readonly') -> Transaction: ...

Storage

Timers and Animation

Timer functions and animation frame requests for time-based functionality and smooth animations.

def set_timeout(func: Callable, interval: int, *args) -> int: ...
def set_interval(func: Callable, interval: int, *args) -> int: ...
def clear_timeout(timer_id: int) -> None: ...
def clear_interval(timer_id: int) -> None: ...
def request_animation_frame(func: Callable) -> int: ...

Timers and Animation

UI Framework

Widget-based GUI toolkit with layout management, styling, and event handling for creating desktop-like web applications.

class Widget:
    def __init__(self, parent: Widget = None): ...
    
class Button(Widget):
    def __init__(self, text: str = "", parent: Widget = None): ...
    
class Entry(Widget):
    def __init__(self, value: str = "", parent: Widget = None): ...
    
class Dialog(Widget):
    def __init__(self, title: str = "", parent: Widget = None): ...

UI Framework

WebSocket Communication

Real-time bidirectional communication with WebSocket support for live data and interactive applications.

class WebSocket:
    def __init__(self, url: str, protocols: list = None): ...
    def send(self, data: str | bytes) -> None: ...
    def close(self, code: int = 1000, reason: str = "") -> None: ...

WebSocket

Types

# Configuration types
class BrythonOptions:
    debug: int  # Debug level 0-3
    cache: bool  # Enable module caching
    indexeddb: bool  # Use IndexedDB for caching
    pythonpath: list[str]  # Additional module paths
    ids: list[str]  # Specific script IDs to run
    args: list[str]  # Command line arguments

# DOM element base
class Element:
    def __init__(self, content: str = "", **attrs): ...
    def bind(self, event: str, callback: Callable) -> Element: ...
    def unbind(self, event: str, callback: Callable = None) -> Element: ...
    
# Event handling
class Event:
    target: Element
    type: str
    preventDefault: Callable
    stopPropagation: Callable

# Browser objects
class DOMDocument:
    def __getitem__(self, id: str) -> Element: ...
    def createElement(self, tag: str) -> Element: ...
    def createTextNode(self, text: str) -> TextNode: ...

class BrowserWindow:
    location: Location
    history: History
    localStorage: Storage
    sessionStorage: Storage

Install with Tessl CLI