Ever wished you could use Python instead of JavaScript in your HTML pages? You’re not alone. Python just feels friendlier, and JavaScript—well, it has a way of annoying even seasoned devs. But here’s the quick answer: HTML pages expect JavaScript, not Python. Your browser only understands JavaScript natively, because it’s built in. No built-in Python interpreter, sadly.
That’s not the end of the dream. People have tried pretty clever hacks to get Python running in the browser. Newer projects like Brython and PyScript are making serious noise, letting you write code in Python that acts a lot like JavaScript on web pages. It’s not perfect, but for simple scripts and demos, it actually works. If you want full control or fast, complex apps, though, you’ll still run into roadblocks.
So, while you can’t just swap all your <script> tags to Python and expect magic, you do have options. Stick around, and I’ll break down where Python shines, where it stumbles, and how to blend the best of both worlds for your next web project.
It’s no accident that JavaScript is the top dog in web browsers. When you open a web page, your browser is already loaded and ready to run JavaScript. It’s built right into every browser—Chrome, Firefox, Safari, Edge. This built-in support means your code just works, almost instantly, no plugins, no weird setup.
The original reason? Back in the 1990s, browsers needed a way for users to interact with pages—think clicking buttons, filling forms, animations. Netscape (the big browser at the time) rolled out JavaScript, and it stuck. Fast forward to now, every modern browser still needs it running constantly to support everything from simple pop-up messages to complex web apps like Google Docs and YouTube.
Browsers have language engines, and JavaScript’s engine is native. That means when you include <script> tags in your HTML, the browser instantly runs them. If you try to pop in Python, nothing happens—the browser just doesn’t know what to do. There’s no built-in engine for Python.
This is why even giant companies like Facebook and Netflix stick with JavaScript for all their browser-facing code. Switching to anything else (like Python) means fighting against the way browsers are designed. That’s a massive headache for any developer.
If you’re hoping to blend Python with your HTML, you’ve probably run into a wall pretty quickly. Browsers only run client-side scripts in JavaScript out of the box, not Python. Still, Python has ways to get in on the Python and HTML party—just not always the way you might expect.
Most web projects use Python on the server side. Popular frameworks like Django and Flask take Python scripts and turn them into full web apps. You write your logic in Python, which then generates HTML pages on the server. The browser just gets HTML, CSS, and JavaScript, like usual. This is super common for dashboards, blogs, and e-commerce sites.
If you want to do something in real-time on the web page—updating the screen when a button is clicked, for example—Python can’t do this out-of-the-box in the browser. That’s JavaScript’s job. But there are a few creative approaches to bring Python a bit closer to the action:
For some context, here’s what devs are mostly doing with Python and HTML:
| Approach | Works in Browser? | Main Use Case |
|---|---|---|
| Django/Flask (Server-side rendering) | No (runs on server) | Generating dynamic HTML |
| Brython/PyScript (Python-in-the-browser) | Yes (with limits) | Educational demos, simple scripts |
| REST API (Backend in Python) | Yes (via JS frontend) | SPA, AJAX apps |
If you’re looking for a seamless way to drop Python code straight into your HTML and manipulate the DOM (the way JavaScript does), it’s just not natively possible—yet. But the new tools and workarounds are pushing those limits, letting you try out Python inside the browser, even if there are some quirks and rough edges.
Want to run Python in the browser like you run JavaScript? That’s where Brython and PyScript come in. These two projects basically try to do what browsers don’t—let regular folks write web code in Python.
Brython (short for Browser Python) has been around for over a decade. It converts Python code into JavaScript behind the scenes so your browser can actually run it. Drop the Brython script in your HTML, pop your Python code inside a <script type="text/python"> tag, and watch it go. You can mess with webpage elements, handle button clicks, even do simple animations—all in Python syntax. However, if you want bleeding-edge performance or complex app features (think video games in the browser), it’s probably not a complete replacement for JavaScript yet.
Then there’s PyScript—newer, very buzzy, and baked by Anaconda (yep, the folks who make the Python data science toolkit). PyScript goes a little further by plugging into WebAssembly, which means it actually runs Python itself (not just JavaScript pretending to be Python). It’s still early days, but PyScript supports pretty wild stuff like plotting graphs with libraries such as Matplotlib, loading data with Pandas, and even using machine learning right on the page (without needing a server!).
Here’s a nuts-and-bolts comparison to make it clear:
| Feature | Brython | PyScript |
|---|---|---|
| Setup | Simple script include | Script include + Pyodide/WebAssembly |
| Speed | Decent for small tasks | Slower to load, faster at heavy processing |
| Library Support | Basic Python, limited external libraries | Supports many core Python libraries (numpy, pandas) |
| Interact with HTML/DOM | Yes (fairly easy) | Yes, but APIs still growing |
| Best Use | Light scripting, education, simple UIs | Data visualization, notebooks, ML demos |
Heads up: Neither Brython nor PyScript can use Python packages that rely on C extensions or heavy system resources—your browser just can’t do everything your laptop can. Both options also make your pages a bit heavier to load than plain JavaScript. But hey, if you love Python and hate switching brain-modes, these tools are genuinely cool for prototypes, learning, or sharing Python-powered web projects without a server.
Jumping straight in, the main snag with using Python in HTML is that web browsers just aren’t built for it. Browsers like Chrome, Firefox, and Safari all have a built-in JavaScript engine, not a Python one. That means Python code won’t run natively—if you try, nothing happens, or you get an error.
Now, with tools like Brython, PyScript, or Transcrypt, Python gets shoehorned into the browser using a layer that basically translates it into JavaScript on the fly. Sounds cool, but it comes with speed bumps:
Here’s a quick look at how things stack up with a few popular tools:
| Toolkit | Runs Natively? | Extra Download Size | Speed Vs JS |
|---|---|---|---|
| Brython | No | 1-2 MB | Slower |
| PyScript | No | Up to 10 MB | Much Slower |
| Transcrypt | No (Compiles to JS) | Minimal | Nearly the Same |
One more thing—none of these tools let you access every single library you’d use in regular Python. Lots of core Python packages just aren’t built for browser life because they expect server-level features you don’t get in a web page.
The bottom line? If you’re building complex, interactive web apps, you’re going to run into brick walls trying to use Python everywhere. For a fun project, demo, or teaching tool, sure, go wild. But when you need speed, full browser power, or a lean site, JavaScript still rules the front-end.
Just because Python isn’t king of the browser doesn’t mean you can’t use it with your HTML projects. Most web apps actually combine both languages, each doing what it does best. Python handles the server-side logic—things like managing the database, logging people in, or running some AI code. JavaScript deals with the stuff happening in your browser: handling button clicks, showing alerts, and all the real-time feel.
This is basically how popular frameworks like Django (Python) and Flask work. You write the backend in Python, then send data to the browser. The frontend gets powered by JavaScript. Together, they’re a solid team. If your site ever asks for new data without reloading the page, that’s JavaScript (using AJAX or fetch) talking to a Python backend via something like a JSON API.
Here’s a quick look at a typical back-and-forth between the two languages:
| Step | What Happens | Language |
|---|---|---|
| 1 | User clicks a button | JavaScript |
| 2 | JavaScript sends request to server (AJAX) | JavaScript |
| 3 | Server handles logic and preps response | Python |
| 4 | Python returns data (usually JSON) | Python |
| 5 | JavaScript updates the page with new info | JavaScript |
If you want your app to feel modern (instant updates, live search, etc), learning how to pass info between Python and JavaScript is key. Usually, you’ll:
Don’t ignore JavaScript—the browser expects it. But using Python for the brains behind your app is honestly the norm. Most pros do this every day. It’s way more flexible than trying to force Python where it doesn’t fit.
If you’re serious about blending Python with HTML or even sneaking a bit of Python into your browser game, a few practical strategies save time and headache. First up: know your tools. Brython and PyScript aren’t just hobbies—they’re getting some real-world traction, especially with educators and people prototyping quick web demos. For most commercial projects, though, plain JavaScript still rules when you care about speed and browser support.
Here are some tested tips if you’re set on stretching Python into web pages:
Want some numbers? Here’s how Python-in-the-browser stacks up (as of mid-2024):
| Tool | First Release | GitHub Stars | Best for | Browser Support |
|---|---|---|---|---|
| Brython | 2012 | 7,000+ | Teaching, Small widgets | Modern browsers |
| PyScript | 2022 | 18,000+ | Demos, Prototypes | Modern browsers |
For a concrete example, here’s how you’d add two numbers together using PyScript in your HTML:
<py-script>
a = 5
b = 3
result = a + b
display(result)
</py-script>
Try stuff out, but know the trade-offs. If you really want to push web development in Python, keep up with Brython and PyScript releases—they’re evolving fast. And yeah, even my dog Archer would agree: don’t try to replace JavaScript totally. Just use Python smartly where it shines.
Written by Caden Whitmore
View all posts by: Caden Whitmore