Exams and private assignments¶
Every student notebook is public by default: it carries no solutions, and a course book republishes it anyway. An exam is different, because the questions themselves are the secret. Setting an assignment's visibility to enrolled keeps it away from anyone outside the class, and three dates decide when the class can reach it.
The window¶
| Setting | What it controls |
|---|---|
visibility: enrolled |
Left out of assignments.json; its notebook goes only to signed-in members of the offering. To anyone else it does not exist. |
release_at |
From this moment students can see the assignment, download the notebook, open it in molab, and read storage.assignment("<slug>"). A private assignment without a release_at stays closed and unlisted for students however long you work on it — set the date when it is ready. |
due_at |
The submission deadline. After it, late_policy decides: accepted and marked late (the default), or reject. |
close_at |
The hard end: no notebook download, no data, no submissions. It may be later than the deadline, so students can still re-run their work after submitting. Leave it blank on a private assignment and the form closes it at the deadline. |
Staff are never held to the window, so you can open, run and submit your own exam before students see it; those attempts are marked as tests and stay out of the gradebook.
The window also limits storage credentials. A student's credential covering an assignment with a close_at expires at the close instead of an hour later, and in the final minute the assignment is no longer granted at all. Data a student already downloaded stays on their machine — the window controls when they can start, and the deadline is enforced when they submit.
Trying it as a student¶
Being exempt from the window also means staff never see what students see. Preview as a student (on your Student view page) switches your own account in this offering to the student experience until you leave it: the student assignment list and portal, the window's closing date and deadline, storage credentials scoped like a student's, and no staff pages. One thing differs on purpose: release dates do not apply, so an assignment can be tried end to end before it opens. What you submit in preview is still a test attempt and never reaches the gradebook. A banner on every page says you are previewing, with Exit preview. It applies to notebooks too: a molab session signed in as you gets student credentials while preview is on.
Reading the whole notebook¶
Whole-notebook submission adds one question, notebook, that is not tied to a cell: the student submits the entire notebook and you read it in the grading queue. Give it points to grade it by hand, or leave it at 0 for a receipt that is stored and rendered but never asks for a score. To score it part by part, give it a rubric; the notebook is then worth what the rubric adds up to. With it on, the instructor notebook needs no _marks cell.
Turn autograde off when nothing should be run against checks. Submissions are still rendered: the grader re-runs the notebook and stores the HTML you read. Raise render_timeout (30–3600 s) when that re-run is a real analysis.
Turn re-run (render) off when the notebook is too heavy for the grader — an analysis over a few gigabytes of data will not fit on a small worker, and the time it takes grows with the data. The grading view then shows the submitted code and a Saved files panel: everything the student wrote under storage.private()/<slug>/ (figures, CSVs, statistical maps), with download links. Ask students to save their results there:
out = storage.private()
out.put("final-exam/figures/result.png", fig) # a figure, as .png/.jpg/.svg/.pdf
out.put("final-exam/group_map.nii.gz", group_map) # a nibabel image or BrainData
out.put("final-exam/answers.csv", answers_df) # typed by extension
out.sync("qc_report", "final-exam/qc_report") # a whole folder
A student's private storage stays writable after the deadline, so each file shows when it last changed, and one modified after due_at is flagged.
Who sees what¶
A submission, its notebook, render and saved files are visible to the student who made it and to the course staff: instructors, and TAs (a TA assigned to sections sees only those sections). Another student gets the same 404 as for a submission that does not exist. In storage, each student's credential names only their own users/<offering>/<id>/ prefix, so one student's notebook cannot read a classmate's files either.
One thing the grader cannot control: a notebook opened in molab lives at a molab URL that anyone holding the link can view. Students should not share their molab link during the exam.
Publishing one¶
grader publish exam.py --server https://grader.dartbrains.org \
--offering neuroimaging/2026-fall --slug final-exam --title "Final exam" \
--private --release 2026-11-20T09:00-05:00 --due 2026-11-22T23:59-05:00 \
--close 2026-11-23T23:59-05:00 --late-policy reject \
--no-autograde --notebook-points 100
Settings you leave out keep their current values, and every one of them can be changed later with Settings on its row of Assignments, or on its own page. Put the exam's data under storage.assignment("final-exam") from an instructor session; students read it once the window opens.
What students see¶
Link to the assignment from the course page with its launch URL rather than the notebook itself:
It sends a signed-out reader through Dartmouth sign-in and lands on their portal, where the exam row offers Open in molab and Download .py, or says when it opens or that it has closed. Do not add a private assignment to a course book's assignment: key: the book fetches and republishes what that key names.