Fragment: Revealing Otherwise Hidden Answers In Jupyter Notebooks

Some notes culled from an internal feedback forum regarding how to provide answers to questions set in Jupyter notebooks. To keep things simple, this does not extend to providing any automated testing (eg software code tests, computer marked assessments etc); just the provision of worked answers to questions. The sort of thing that might appear in the back of a text book referenced from a question set in the body of the book.

The issue at hand is: how do you provide friction that stops the student just looking at the answer without trying to answer the question themselves? And how much friction should you provide?

In our notebook using data management and analysis course, some of the original notebooks took a naive approach of presenting answers to questions in a separate notebook. This add lots of friction and a quite unpleasant and irritiating interaction, involving opening the answer notebook in a new tab, waiting for the kernel start, and then potentially managing screen real estate and multiple windows to compare the original question and student’s own answer with the answer. Other technical issues include state managament, if for answer the desired answer was not in and of itself reproducible, but instead required some “boilerplate” setting up of the kernel state to get it into a situation where the answer code could be meaningfully run.

One of the advantages of having answer code in a separate notebook is that a ‘Run All’ action in the parent notebook wonlt run the answer code.

Another approach taken in the original notebooks was to use an exercise extension that provided a button that could be clicked to reveal a hidden anwser in the original notebook. This required an extension to be enabled in the environment in which the original notebook was authored, so that the question and answer cells could be selected and then marked up with exercise cell metadata via a toolbar button, and on the student machine, so that the exercise button could be actively be rendered and the answer cell initially hidden by the notebook UI when the notebook was loaded in the browser. (I’m not sure if it would also be possible to explicitly code a button using HTML in a markdown cell that could hide/reveal another classed or id‘d HTML element; I suspect any javascript would be sanitised out of the markdown?)

Most recently, all the notebooks containing exercises in ourr databases course now use a model where we use a collapsible heading to hide the answer. Clicking the collapsed header indicator in the notebook sidebar reveals the answer, which is typically copmposed of several cells, both markdown and code cells. The answer is typically provided in a narrative form, often in the style of a “tutor at your side”, providing not just an explained walkthrough of the answer but also identifying likely possible incorrect answers and misunderstandings, why they might at first appear to have been “reasonable” answers, and why they are ultimately incorrect.

This answer reveal mechanic is very low friction, and degrades badly: if the collapse headings extension is note enabled, the answer is rendered as just any other notebook cell.

When using these approaches, care needs to be taken when considering what the Run All action might do when the answer code cells are reached: does the answer code run? Does it create an error? Is the code ignored and code execution continued in cells after the hidden answer cell.

In production workflows where a notebook may be executed to generated a particular output document, such as a PDF with all cells run, how are answer cells to be treated? Should they be displayed? SHould they be displayed and answer cells run? This might depend on audience: for example, a PDF output for a tutor may contain answers and answer outputs, a student PDF may actually be two or three documents: one containing the unanswered text, one containing the answer code but not executed, one cotnaining the answer code and executed code outputs.

Plagiarising myself from a forthcoming post, as well as adding friction, I think wonder if what we’re actually trying to achieve by the way the answer is accessed or aotherwise revealed might include various other psychological and motivational factors that affect learning. For example, setting up the anticipation that pays-off as a positive reward for a student who gets the answer right, or a slightly negative payoff that makes a student chastise themselves for clicking right to the answer. At the same time, we also need to accommodate students who may have struggled with a question and is reluctantly appealing to the answer as a request for help. There are also factors relating to the teaching, insofar as what we expect the student to do before they reveal the answer, what expectation students may have (or that we may set up) regarding what the “answer” might provide, how we expect the student to engage with the answer, and what we mght expect them to do after reading the answer.

So what other approaches might be possible?

If the answer can be contained in just the contents of a sinlge code cell, the answer can be placed in an external file, for example,, in the same directory or an inconvenient to access solutions directory such as ../../solutions. This effectively hides the solution but allows a student to reder it by running the following in a code cell:

%load ../../solutions/

The content of the file will be loaded into the code cell.

One advantage of this approach is that a student has to take a positive action to render the answer code into the cell. You can make this easier or harder depending on how much friction you want to add. Eg low friction: just comment out the magic in the code cell, so all a student has to do is uncomment and run it. Higher friction: make them work out what the file name is and write it themselves, then run the code cell.

I’m not sure I’m convinced having things strewn across multiple files is the best way of adding the right amount and right sort of friction to the answer lookup problem though. It also causes maintenance issues, unless you are generating separate student activity notebook and student hint or answer notebooks from a single master notebook that contains activities and hints/answers in the same document.

Other approaches I’ve seen to hiding and revealing answers include creating a package that contains the answers, and then running a call onto that package to display the answer. For example, something like:

from course_activities import answers

An alternative to rendering answers from a python package would be to take more of a “macro” approach and define a magic which maybe has a slightly different feeling to it. For example:

%hint week2_section1_activity3

In this approach, you could explore different sorts of psychological friction, using nudges:

%oh_go_on_then_give_me_a_hint_for week2_section1_activity3


%ffs_why_is_this_so_hard week2_section1_activity3

If the magic incantation is memorable, and students know the pattern for creating phrases like week2_section1_activity3 eg from the notebook URL pattern, then they can invoke the hint themself by saying it. You could even have aliases for revealing the hint, which the student could use in different situations to remind themselves of their state of mind when they were doing the activity.

%I_did_it_but_what_did_you_suggest_for week2_section1_activity3

With a little bit of thought, we could perhaps come up with a recipe that combines approaches to provide an experience that does degrade gracefully and that perhaps also allows us to play with different sorts of friction.

For example, suppose we extend the Collapsible Heading notebook extension so that if we tag a cell as an answer-header cell and a code cell below put a #%load line. In an unextended notebook, the student has to uncomment the load magic and run the cell to reveal the answer; in an extended notebook, the extension colour codes the answer cell and collapses the answer; when the student clicks to expand the answer, the extension looks for #%load lines in the collapsed area, uncomments and executes them to load in the answer, expands the answer cells automatically.

We could go further and provide an extension that lets an author write an answer in eg a markdown cell and then “answerify” it by posting it as metadata in preceding Answer reveal cell. In an unextended student notebook, the answer would be hidden in metadata. To reveal it, a student could inspect the cell metadata. Clunky for them and answer wouldn’t be rendered, but doable. In extended notebook clicking reveal would cause the extension to extract the answer from metadata and then render it in the notebook.

In terms of adding friction, we could perhaps add a delay between clicking a reveal answer button and displaying an answer, although if the delay is too long, a student may pre-emptively come to click the answer button before they actually want to tanswer the button so they don’t have to wait. The use of audible signal might also provide psychological nudges that subconsciously influence the student’s decision about when to reveal an answer.

There are lots of things to explore I think but they all come with a different set of opportunity costs and use case implications. But a better understanding of what we’re actually trying to achieve would be a start… And that’s presumably been covered in the interactive learning design literature? And if it hasn’t, then why not? (Am I overthinking all this again?!)

PS It’s also worth noting something I haven’t covered: notebooks that include interactive self-test questions, or self-test questions where code cells are somehow cross-referenced with code tests. (The nteract testbook recipe looks like it could be interesting in this respcect, eg where a user might be able to run tests from one notebook against another notebook. The otter-grader might also be worth looking at in this regard.

Author: Tony Hirst

I'm a Senior Lecturer at The Open University, with an interest in #opendata policy and practice, as well as general web tinkering...

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