How to embed a Python interpreter on a website

Question

I am attempting to build an educational coding site, similar to Codecademy, but I am frankly at a loss as to what steps should be taken. Could I be pointed in the right direction in including even a simple python interpreter in a webapp?

Answer 1

One option might be to use PyPy to create a sandboxed python. It would limit the external operations someone could do.

Once you have that set up, your website would take the code source, send it over ajax to your webserver, and the server would run the code in a subprocess of a sandboxed python instance. You would also be able to kill the process if it took longer than say 5 seconds. Then you return the output back as a response to the client.

See these links for help on a PyPy sandbox:
http://doc.pypy.org/en/latest/sandbox.html
http://readevalprint.com/blog/python-sandbox-with-pypy.html

To create a fully interactive REPL would be even more involved. You would need to keep an interpreter alive to each client on your server. Then accept ajax "lines" of input and run them through the interp by communicating with the running process, and return the output.

Overall, not trivial. You would need some strong dev skills to do this comfortably. You may find this task a bit daunting if you are just learning.

Answer 2

There's more to do here than you think.

The major problem is that you cannot let people run arbitrary Python code on your webserver. For example, what happens if they do

import os
os.system("rm -rf *.*")

So clearly you have to run this Python code securely. But then you have the problem of securing Python, which is basically impossible because of how dynamic it is. And so you'll probably have to run the Python shell in a virtual machine, which comes with its own headaches.

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Have you seen e.g. http://code.google.com/p/google-app-engine-samples/downloads/detail?name=shell_20091112.tar.gz&can=2&q=?