# Correction Helper
## Project
This is just a set of tools to help writing correction bots in Python for Python.
It is used for [hackinscience](https://hackinscience.org), 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](https://github.com/netblue30/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:
```python
with student_code():
their_function()
```
Find a more complete example in the `examples/` directory.
## Allowed parameters for `student_code`, and their default values
### `exception_prefix="I got an exception:"`
Printed right before the exception, if any.
It's allowed to give a list of strings, in which case they'll be
separated by `"\n\n"`, useful to render markdown paragraphs.
### `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:
```python
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](https://github.com/aroberge/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:
```python
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.
