tywrap

TypeScript wrapper for Python libraries with full type safety.

⚠️ Experimental — APIs may change before v1.0.0. See the releases page for breaking changes.

Features

• Full Type Safety - TypeScript definitions generated from Python source analysis
• Development Hot Reload - Real Node watch sessions regenerate wrappers and swap the active bridge without re-importing generated modules
• Generic-Aware Declarations - Preserves simple TypeVar and callable ParamSpec generics in generated .ts and .d.ts output
• Multi-Runtime - Node.js (subprocess) and browsers (Pyodide)
• Rich Data Types - numpy, pandas, scipy, torch, sklearn, and stdlib types
• Efficient Serialization - Apache Arrow binary format with JSON fallback

Why tywrap?

| Feature | tywrap | pythonia | node-calls-python | pymport | | ------------------------------- | --------- | --------- | ----------------- | --------- | | Auto-generated TypeScript types | ✅ | ❌ | ❌ | ❌ | | Browser / WASM (Pyodide) | ✅ | ❌ | ❌ | ❌ | | numpy / pandas type mappings | ✅ | ❌ | ❌ | ❌ | | Node.js + Bun + Deno | All three | Node only | Node only | Node only | | Apache Arrow binary transport | ✅ | ❌ | ❌ | ❌ |

Requirements

• Node.js 20+ (or Bun 1.1+ / Deno 1.46+)

• Python 3.10+ with tywrap-ir:

  pip install tywrap-ir

Quick Start

npm install tywrap
pip install tywrap-ir  # Python component for code generation
npx tywrap init        # Create config (and package.json scripts if present)
npx tywrap generate    # Generate wrappers

tywrap and tywrap-ir are versioned independently. Install the latest published release of each package unless you need to pin them explicitly.

For CI (or to verify a dependency upgrade didn’t change the generated surface):

npx tywrap generate --check

For local Node development, tywrap/dev gives you real hot reload: watch local Python package trees, regenerate wrappers, and swap the active bridge while keeping the last known good state if regeneration fails.

import { NodeBridge } from 'tywrap/node';
import { setRuntimeBridge } from 'tywrap/runtime';
import * as math from './generated/math.generated.js';

const bridge = new NodeBridge({ pythonPath: 'python3' });
setRuntimeBridge(bridge);

const result = await math.sqrt(16); // 4

If tywrap saves you time, a ⭐ on GitHub helps others find it.

Runtime Bridges

Node.js

import { NodeBridge } from 'tywrap/node';
const bridge = new NodeBridge({
  pythonPath: 'python3',
  virtualEnv: './venv',
  timeoutMs: 30000,
});

NodeBridge is the public Node runtime bridge. It runs in single-process mode by default and also supports pooled execution through minProcesses, maxProcesses, and maxConcurrentPerProcess.

OptimizedNodeBridge is now only a deprecated compatibility alias for older deep imports. It is not part of the package exports and should not be used in new code.

By default, NodeBridge inherits only PATH/PYTHON*/TYWRAP_* from process.env to keep the subprocess environment minimal. Set inheritProcessEnv: true if you need the full environment. Large JSONL responses are capped by maxLineLength (defaults to TYWRAP_CODEC_MAX_BYTES when set, otherwise 1MB).

You can cap payload sizes with TYWRAP_CODEC_MAX_BYTES (responses) and TYWRAP_REQUEST_MAX_BYTES (requests) to keep JSONL traffic bounded.

Development Hot Reload

import { startNodeWatchSession } from 'tywrap/dev';
import { NodeBridge } from 'tywrap/node';

const session = await startNodeWatchSession({
  configFile: './tywrap.config.ts',
  createBridge: async config =>
    new NodeBridge({
      pythonPath: config.runtime.node?.pythonPath ?? 'python3',
      timeoutMs: config.runtime.node?.timeout ?? 30000,
    }),
});

• Node: full watch + wrapper regeneration + bridge swap
• Pyodide: use createBridgeReloader(...) from tywrap/dev for manual bridge replacement
• HTTP: restart or redeploy the remote server outside tywrap

The Node watch session manages local package trees, refreshes nested directory watchers when package layouts change, and keeps the last known good generated output and bridge active if regeneration returns structured failures.

Browser (Pyodide)

import { PyodideBridge } from 'tywrap/pyodide';
const bridge = new PyodideBridge({
  indexURL: 'https://cdn.jsdelivr.net/pyodide/v0.28.0/full/',
});
await bridge.init();

Deno / Bun

import { NodeBridge } from 'npm:tywrap'; // Deno
import { NodeBridge } from 'tywrap'; // Bun

Configuration

// tywrap.config.ts
import { defineConfig } from 'tywrap';

export default defineConfig({
  pythonModules: {
    pandas: {
      runtime: 'node',
      typeHints: 'strict',
      classes: ['DataFrame'],
      functions: ['read_csv'],
    },
    numpy: {
      runtime: 'node',
      typeHints: 'strict',
      alias: 'np',
    },
  },
  output: { dir: './src/generated' },
});

See Configuration Guide for all options.

Supported Data Types

| Python | TypeScript | Notes | | ------------------------------------- | ------------------------ | ---------------- | | numpy.ndarray | Uint8Array / array | Arrow or JSON | | pandas.DataFrame | Arrow Table / object[] | Arrow or JSON | | scipy.sparse.* | SparseMatrix | CSR, CSC, COO | | torch.Tensor | TorchTensor | CPU only | | sklearn estimator | SklearnEstimator | Params only | | datetime, Decimal, UUID, Path | string | Standard formats |

For Arrow encoding with numpy/pandas:

import { registerArrowDecoder } from 'tywrap';
import { tableFromIPC } from 'apache-arrow';
registerArrowDecoder(bytes => tableFromIPC(bytes));

Documentation

• Getting Started
• Configuration
• API Reference
• Troubleshooting

Contributing

npm install
npm test

See CONTRIBUTING.md for guidelines.

License

MIT © tywrap contributors

Links

• GitHub
• npm
• PyPI
• Issues