correction-helper 2026.3

Some helpers to help writing correction bots, use by hackinscience.org.

Correction Helper

Project

This is just a set of tools to help writing correction bots in Python for Python.

It is used for hackinscience, but could be used elsewhere.

Security considerations

Running student code is probably really unsafe, unless you trust your students not to drop you a backdoor.

This projet does not help with security in any ways, maybe take a look at firejail if you have trust issues (Yes you can use correction-helper inside firejail).

Usage

To install it, run: pip install correction-helper.

In your checking code, you can use it like this:

The student_code decorator

This decorator is aimed to catch most problems that could happen in student code, use it simply as:

with student_code():
    their_function()

Find a more complete example in the examples/ directory.

Allowed parameters for student_code, and their default values

print_prefix="Your code printed:"

Message to display before the student prints (in case print_allowed is False or None).

It's allowed to give a list of strings, in which case they'll be separated by "\n\n", useful to render markdown paragraphs.

too_slow_message="Your program looks too slow, looks like an infinite loop."

Message to display in case the code runs slower than the given timeout (defaults to 1s).

It's allowed to give a list of strings, in which case they'll be separated by "\n\n", useful to render markdown paragraphs.

prefix=()

A prefix for print_prefix, exception_prefix, and too_slow_message=, usefull to deduplicate strings, like:

with student_code(
    prefix="While calling blahblah('bar')",
    print_prefix="it printed:",
    exception_prefix="it raised:",
    too_slow_message="it took more than 1s, had to kill it.",
):
    blahblah('bar')

friendly=False

To use, or not friendly-traceback instead of bare Python exceptions.

print_allowed=True

To allow or deny the student to print to stdout and stderr.

• True: Prints are allowed (and displayed).
• None: Prints are allowed (but not displayed).
• False: Prints are disallowed (and displayed).

In all cases you can read what they printed using the value of the context manager:

with student_code(print_allowed=None) as run:
    their_function()
assert run.err == ""
assert run.out == "42"

Good practices

Write the student checking code a you would write unit test for your own code.