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April 2026

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Online Python Environment 'TigerPython'
by Tobias Kohn May 1, 2026

May 1, 2026

Hi everyone, I would like to briefly bring our open-source Python project to your attention: a freely available browser-based Python environment for education. I imagine it might be useful for a number of teachers and educators. Before going on, please let me place an important disclaimer: this is a project we do out of passion for teaching Python programming. We do not profit in any way by people using it. There is no premium version, no subscription or anything else. Just an open-source Python environment based on Pyodide and our conviction that good teaching materials should not come with a price tag. In this sense, I hope you will excuse our blatant `advertisement'. The resources ------------- The running IDE/environment is available here: https://webtigerpython.ethz.ch/ If you want to jump right to the source code: https://gitlab.inf.ethz.ch/public-dkomm/webtp/webtp-core There is also a (somewhat older) online tutorial that is available in English, French and German: https://programmierkonzepte.ch/engl/ Should you want to learn more about our overall project, you can find the website here: https://tigerjython.ch/en Brief background ---------------- The project `TigerPython' (originally `TigerJython') started in 2012 when I created a Python IDE for my teaching at high school. Based on Jython, I added improved error messages and worked with some friends on a number of additional libraries such as graphics and support for robotics. To my surprise it spread rather quickly in high schools, mostly in Switzerland and Germany, we founded a small group of volunteers (the `TJ-group') and started to write accompanying tutorials, giving workshops, etc. Having a Python-environment based on Java caused a number of issues, though. In particular, many students and schools are using iPads, say, which do not run Java at all. We therefore decided to relocate to the web and create a browser-based version that would run on essentially any device. To keep it as simple as possible, we left out features like an interactive concole and focused more on a paradigm where you just enter the code and hit `play'. While the surface looks (deceptively) simple, we are working on a lot of power behind the scenes. For instance, WebTigerPython provides support for PyGame directly in the browser. There is also a visual debugger (it needs to be turned on in the settings on the very top right, though), enhanced error messages in a number of different languages and support for the Micro:bit. Support for multiple files is in beta-testing and will come soon, too, but we really want to make sure we keep the simplicity of the IDE, without cluttering. If you notice a tiny arrow on the lower left, you can open a small built-in documentation of some modules (we are still working on expanding that). Finally, if you wrote some code that you want to share (with students, day), you can do just that through the `share`-button on the top right: your entire program code will be encoded in the URL, which means that you do not depend on any server storing your program, but it also puts some practical limitations on the length of a shared program. The team behind TigerPython is for the most part working at the universities `ETH Zurich' in Switzerland and `KIT' in Germany. We understand this project as our mission to advance programming education; and, of course, we love the occasional engineering challenge to improve it further. It is only a small contribution to the huge Python ecosystem, but perhaps one that is found to be of some value. Full disclosure: the only thing that we do potentially get out of more users is some anonymised usage data—if you consent, that is. For instance, one of our primary endeavours is to get really good and helpful error messages and figure out what the major issues and hurdles are for students who learn to program in Python. On top of that: if you run into some issue, have a special request or some motivational words for our young team, please report a bug (directly inside the IDE) or get in touch. Differences to Python --------------------- There are a few small differences between TigerPython and the usual vanilla Python that I should probably mention, too: 1. We added a new loop with the keyword `repeat`. It is quite simple, really: `repeat 5:` lets you repeat something five times and is internally translated to `for _ in range(5):`. This addition is based on empirical research suggesting that `repeat` is much more intuitive than `for` and it lets us avoid the hassle with variables while introducing some basic concepts like loops. 2. Coming from Python 2, I slightly changed the semantics of `input()`. Python 2 would try to evaluate the input as a Python expression. This is quite neat for entering numbers, say. However, when entering a string (without quotes), Python would spit at you and raise a good old NameError. I changed that to something IMHO more `sensical' where `input()` tries to convert your input into an int, a float or return it as a string otherwise. Fast forward a couple of years, Python 3 has changed the semantics of `input()` quite a bit, whereas we have a number of tutorials and textbooks relying on that adapted semantics, opening a bit of gap here. 3. The error messages in TigerPython are sometimes a bit more `aggressive' than in plain Python. If you enter a simple name, say, like `foo`, TigerPython will tell you that this is not really doing anything. The reason behind this is that many of my students forgot to put the parentheses for function calls (i.e. `foo()`) and be puzzled that the program would not do anything. Others wrote `x + 2` instead of `x += 2`, etc. You can, however, turn those enhanced error messages off in the settings. We are currently discussing ways to make this more configurable. However, as a pedagogical environment, we must do this in a way where students do not accidentally turn a feature off and be stumped by their programs no longer working correctly without any visible difference. Academic publications --------------------- We have also published a small number of academic publications in case you are interested to see what we do in terms of research with this: C. Bachmann et al.: WebTigerPython -- A Low-Floor High-Ceiling Python IDE for the Browser https://arxiv.org/abs/2410.07001 T. Kohn & B. Manaris: Tell Me What's Wrong: A Python IDE with Error Messages https://dl.acm.org/doi/abs/10.1145/3328778.3366920 T. Kohn: The Error Behind The Message: Finding the Cause of Error Messages in Python https://dl.acm.org/doi/abs/10.1145/3287324.3287381 Closing ------- There are already a number of great Python environments for educational use. TigerPython might add to that list the possibility to run your programs inside your browser without any download or setup required and from virtually any device. However, our main focus is on improving the `more hidden parts' like error messages. It really is entirely free to use, without any kind of account, subscription or premium plan. Clearly, it will, and cannot, serve all needs and use cases, but if it helps someone out there learn or teach students how to program in Python, we are happy! :-D Kind regards Tobias – on behalf of the TigerPython core development team: Tobias Kohn, Clemens Bachmann & Dennis Komm Prof Dr Tobias Kohn Professor of Computer Science and Education Karlsruhe Institute of Technology (KIT), Germany tobias.kohn(a)kit.edu

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