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Externum — Browser Playground

How It Works​

The Externum playground executes entirely in your browser — no server, no API keys, no network requests.

┌─────────────────────────────────────────────────┐
│  Browser                                        │
│                                                 │
│  ┌───────────────┐    ┌──────────────────────┐  │
│  │  Externum     │    │  Pyodide             │  │
│  │  Playground   │───►│  (Python → WASM)     │  │
│  │  (React UI)   │    │                      │  │
│  └───────────────┘    └──────────────────────┘  │
│         │                       │               │
│         ▼                       ▼               │
│  ┌───────────────┐    ┌──────────────────────┐  │
│  │  Code Editor  │    │  Externum Transpiler │  │
│  │  (textarea)   │    │  (runs in WASM)      │  │
│  └───────────────┘    └──────────────────────┘  │
│         │                       │               │
│         ▼                       ▼               │
│  ┌──────────────────────────────────────────┐   │
│  │  Output Panel                            │   │
│  │  (stdout / stderr / errors)              │   │
│  └──────────────────────────────────────────┘   │
└─────────────────────────────────────────────────┘

Tech Stack​

  • Pyodide — Python runtime compiled to WebAssembly
  • Externum transpiler — the Python-based transpiler runs inside Pyodide
  • React — UI components (editor, output, controls)
  • No server — everything runs client-side

Usage​

  1. Write Externum code in the editor
  2. Click ▶ Run
  3. The transpiler converts to Python
  4. Pyodide executes the Python output
  5. stdout/stderr displayed in the output panel

Limitations​

  • Shell integration (`cmd`, %% ... %%) — not available in browser
  • File I/O — browser sandboxed, no real filesystem
  • Binary compilation — not available (Python transpilation only)
  • Module imports — limited to built-in modules

Running Locally​

# The playground is part of the Docs site
cd docs-site
npm install
npm run start

# Navigate to /externum/playground

Why WebAssembly?​

Pyodide brings the full Python runtime to the browser via WebAssembly. This means:

  • Zero server costs — no backend to maintain
  • Instant execution — no network latency
  • Offline capable — works without internet (after initial load)
  • Privacy — code never leaves the user's browser
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