BCS Blog

COBOL, z/OS performance measurement, and systems programming updates.

Open Portal

Python In A Browser

By Arch Brooks on July 17, 2026 in Programming

Back to Blog ← Back

Permalink

1. Pyodide (Best for client-side Python)

Pyodide compiles CPython to WebAssembly, allowing Python to run entirely in the browser without a server.

Advantages:

No installation required for users
Access to many scientific libraries (NumPy, Pandas, Matplotlib)
Can interact with JavaScript and the DOM
Runs offline after loading

Example:

<!DOCTYPE html>
<html>
<head>
    <script src="https://cdn.jsdelivr.net/pyodide/v0.28.0/full/pyodide.js"></script>
</head>
<body>
<pre id="output"></pre>

<script>
async function main() {
    let pyodide = await loadPyodide();

    let result = await pyodide.runPythonAsync(`
sum(range(1,11))
    `);

    document.getElementById("output").textContent = result;
}

main();
</script>

</body>
</html>

2. PyScript (Easiest)

PyScript builds on Pyodide and lets you write Python directly in HTML.

<html>
<head>
    <link rel="stylesheet"
          href="https://pyscript.net/releases/2025.5.1/core.css">
    <script type="module"
            src="https://pyscript.net/releases/2025.5.1/core.js"></script>
</head>

<body>

<py-script>
print("Hello World!")

for i in range(5):
    print(i)
</py-script>

</body>
</html>

3. Brython

Brython is a Python interpreter written in JavaScript.

<script src="brython.min.js"></script>

<body onload="brython()">

<script type="text/python">
print("Hello from Python")
</script>

</body>

4. Server-side Python

The browser displays HTML, while Python runs on the server.

Frameworks include:

Flask
Django
FastAPI
Bottle
Tornado

This is the standard approach for production web applications.

5. WebAssembly (CPython)

The newest versions of CPython can be compiled to WebAssembly, enabling a nearly full Python interpreter in the browser.

Can Python manipulate HTML?

Yes.

Example with PyScript:

from pyscript import document

document.querySelector("#message").innerHTML = "<h1>Hello</h1>"

Can Python call JavaScript?

Yes.

from js import alert

alert("Hello from Python!")

Which is best?

Purpose	Recommendation
Full web application	Flask, FastAPI, or Django
Interactive browser application	PyScript
Scientific computing in browser	Pyodide
Teaching Python	PyScript
Offline browser application	Pyodide
Desktop-like web app	PyScript + Bootstrap

Since you've been building Bootstrap 5 applications with MariaDB and PHP, a practical architecture is:

Frontend: Bootstrap 5 + JavaScript
Client-side Python (optional): PyScript or Pyodide for calculations, data processing, or AI features in the browser
Backend: Python (FastAPI or Flask), or PHP if you prefer
Database: MariaDB

Comments

No comments yet.

Title *

Slug

Excerpt

Content *

HTML is supported.

SEO Meta Data

Meta Title

Meta Description