Student Usage

Otter provides an IPython API and a command line tool that allow students to run checks and export notebooks within the assignment environment.

The Notebook API

Otter supports in-notebook checks so that students can check their progress when working through assignments via the otter.Notebook class. The Notebook takes one optional parameter that corresponds to the path from the current working directory to the directory of tests; the default for this path is ./tests.

import otter
grader = otter.Notebook()

If my tests were in ./hw00-tests, then I would instantiate with

grader = otter.Notebook("hw00-tests")

Students can run tests in the test directory using Notebook.check which takes in a question identifier (the file name without the .py extension). For example,

grader.check("q1")

will run the test q1.py in the tests directory. If a test passes, then the cell displays “All tests passed!” If the test fails, then the details of the first failing test are printed out, including the test code, expected output, and actual output:

Students can also run all tests in the tests directory at once using Notebook.check_all:

grader.check_all()

This will rerun all tests against the current global environment and display the results for each tests concatenated into a single HTML output. It is recommended that this cell is put at the end of a notebook for students to run before they submit so that students can ensure that there are no variable name collisions, propagating errors, or other things that would cause the autograder to fail a test they should be passing.

Exporting Submissions

Students can also use the Notebook class to generate their own PDFs for manual grading using the method Notebook.export. This function takes an optional argument of the path to the notebook; if unspecified, it will infer the path by trying to read the config file (if present), using the path of the only notebook in the working directory if there is only one, or it will raise an error telling you to provide the path. This method creates a submission zip file that includes the notebook file, the log, and, optionally, a PDF of the notebook (set pdf=False to disable this last).

As an example, if I wanted to export hw01.ipynb with cell filtering, my call would be

grader.export("hw01.ipynb")

as filtering is by defult on. If I instead wanted no filtering, I would use

grader.export("hw01.ipynb", filtering=False)

To generate just a PDF of the notebook, use Notebook.to_pdf.

Command Line Script Checker

Otter also features a command line tool that allows students to run checks on Python files from the command line. otter check takes one required argument, the path to the file that is being checked, and three optional flags:

  • -t is the path to the directory of tests. If left unspecified, it is assumed to be ./tests

  • -q is the identifier of a specific question to check (the file name without the .py extension). If left unspecified, all tests in the tests directory are run.

  • --seed is an optional random seed for execution seeding

The recommended file structure for using the checker is something like the one below:

hw00
├── hw00.py
└── tests
    ├── q1.py
    └── q2.py  # etc.

After a cd into hw00, if I wanted to run the test q2.py, I would run

$ otter check hw00.py -q q2
All tests passed!

In the example above, I passed all of the tests. If I had failed any of them, I would get an output like that below:

$ otter check hw00.py -q q2
1 of 2 tests passed

Tests passed:
    possible


Tests failed:
*********************************************************************
Line 2, in tests/q2.py 0
Failed example:
    1 == 1
Expected:
    False
Got:
    True

To run all tests at once, I would run

$ otter check hw00.py
Tests passed:
    q1  q3  q4  q5


Tests failed:
*********************************************************************
Line 2, in tests/q2.py 0
Failed example:
    1 == 1
Expected:
    False
Got:
    True

As you can see, I passed for of the five tests above, and filed q2.py.

If I instead had the directory structure below (note the new tests directory name)

hw00
├── hw00.py
└── hw00-tests
    ├── q1.py
    └── q2.py  # etc.

then all of my commands would be changed by adding -t hw00-tests to each call. As an example, let’s rerun all of the tests again:

$ otter check hw00.py -t hw00-tests
Tests passed:
    q1  q3  q4  q5


Tests failed:
*********************************************************************
Line 2, in hw00-tests/q2.py 0
Failed example:
    1 == 1
Expected:
    False
Got:
    True

otter.Notebook Reference

class otter.check.notebook.Notebook(*args, **kwargs)

Notebook class for in-notebook autograding

Parameters
  • nb_path (str, optional) – path to the notebook being run

  • tests_dir (str, optional) – path to tests directory

  • colab (bool, optional) – whether this notebook is being run on Google Colab; if None, this information is automatically parsed from IPython on creation

check(*args, **kwargs)

Runs a method, catching any errors and logging the call. Returns the return value of the function, unless EventType.CHECK is used, in which case the return value is assumed to be a 3-tuple and the second value in the tuple is returned.

check_all(*args, **kwargs)

Runs a method, catching any errors and logging the call. Returns the return value of the function, unless EventType.CHECK is used, in which case the return value is assumed to be a 3-tuple and the second value in the tuple is returned.