Building a WebAssembly-Powered Python Application with Umi.
Published: 2023-10-07 13:16:22

**Introduction**

In this tutorial, we'll explore the integration of Umi, a framework primarily designed for JavaScript, with a Python-based web application. Umi allows us to run WebAssembly (Wasm) code in the browser, opening up exciting possibilities for combining Python and Rust for web development.

We will create a simple application that adds two numbers using Rust and WebAssembly within a Python Flask web application. This example demonstrates the power of WebAssembly and how it can be seamlessly integrated into Python projects.

**Prerequisites**

Before we dive into the code, make sure you have the following installed:

1. Python
2. Node.js
3. Emscripten

**Setting Up the Environment**

To begin, let's set up our development environment:

1. Create a new directory for our project:

```bash
mkdir umi-python-example
cd umi-python-example
```

2. Initialize a Python virtual environment:

```bash
python -m venv venv
source venv/bin/activate  # On Windows, use `venv\Scripts\activate`
```

3. Install the necessary Python packages:

```bash
pip install uwsgi flask
```

**Creating a Python Flask Application**

Now, let's create a Python Flask application:

1. Create a Python file called `app.py`:

```python
from flask import Flask, render_template

app = Flask(__name__)

@app.route('/')
def index():
    return render_template('index.html')

if __name__ == '__main__':
    app.run()
```

2. Create a `templates` folder and an `index.html` file inside it. This HTML file will serve as the entry point for our Umi application:

`templates/index.html`:

```html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Umi Python Example</title>
</head>
<body>
    <div id="root"></div>
    <script src="/static/umi.js"></script>
</body>
</html>
```

**Creating a Umi Application**

Now, let's create a Umi application within our project:

1. Run the following command to create a Umi app:

```bash
npx create-umi@2
```

Follow the prompts to configure your Umi project. Make sure to select the appropriate options for your use case.

2. In the `umi/src/pages/index.tsx` file, we'll create a simple Rust function that adds two numbers using WebAssembly:

```tsx
import React from 'react';
import styles from './index.css';

const wasm = import('../../pkg');

const App: React.FC = () => {
  const [result, setResult] = React.useState<number | null>(null);

  React.useEffect(() => {
    wasm
      .then((module) => module.add(4, 5))
      .then((sum) => setResult(sum));
  }, []);

  return (
    <div className={styles.container}>
      <h1>Umi Python Example</h1>
      <p>Result of adding 4 and 5 using Rust and WebAssembly:</p>
      <p>{result}</p>
    </div>
  );
};

export default App;
```

**Building and Running the Application**

Now that our application is set up, let's build and run it:

1. Build the Umi application:

```bash
cd umi
npm install
npm run build
```

2. Copy the Umi build output to your Flask application's static folder:

```bash
cp -r dist ../static
```

3. Run the Flask application:

```bash
python app.py
```

Visit http://localhost:5000 in your web browser to see your Umi-powered Python application in action.

**Conclusion**

In this tutorial, we've explored the integration of Umi, a JavaScript-based framework, into a Python Flask web application. By leveraging WebAssembly and Rust, we were able to add two numbers using a Umi-powered module, demonstrating the potential of combining different technologies for web development.

This example serves as a starting point for exploring more complex integrations and use cases. Umi's flexibility allows developers to harness the power of WebAssembly alongside their existing Python applications, creating a richer and more dynamic web experience.