The philosophy and the approach

The nbgrader project evolved from my experiences as an instructor and a student. This excerpt from David Marr’s book, Vision, is one of the core readings of the class that inspired the creation of nbgrader. Dr. Marr was an originator of the field of computational neuroscience and has been extremely influential in the field of computational cognitive science as well. On behalf of the many individuals who contribute to nbgrader, I hope you find this project enhances your teaching and learning experiences.

Jess Hamrick, UC Berkeley

How to structure course files

For instructor ease of use and developer maintenance, nbgrader makes a few assumptions about how your assignment files are organized. By default, nbgrader assumes that your assignments will be organized with the following directory structure:

{course_directory}/{nbgrader_step}/{student_id}/{assignment_id}/{notebook_id}.ipynb

where:

  • course_directory variable is the root directory where you run the nbgrader commands. This means that you can place your class files directory wherever you want. However, this location can also be customized (see the configuration options) so that you can run the nbgrader commands from anywhere on your system, but still have them operate on the same directory.
  • nbgrader_step - Each subcommand of nbgrader (e.g. assign, autograde, etc.) has different input and output folders associated with it. These correspond to the nbgrader_step variable – for example, the default input step directory for nbgrader autograde is “submitted”, while the default output step directory is “autograded”.
  • student_id corresponds to the unique ID of a student.
  • assignment_id corresponds to the unique name of an assignment.
  • notebook_id corresponds to the name of a notebook within an assignment (excluding the .ipynb extension).

Example

Taking the autograde step as an example, when we run the command nbgrader autograde "Problem Set 1", nbgrader will look for all notebooks that match the following path:

submitted/*/Problem Set 1/*.ipynb

For each notebook that it finds, it will extract the student_id, assignment_id, and notebook_id according to the directory structure described above. It will then autograde the notebook, and save the autograded version to:

autograded/{student_id}/Problem Set 1/{notebook_id}.ipynb

where student_id and notebook_id were parsed from the input file path.

Here is how a sample directory structure for the course named course101 might look, where the users bitdiddle and hacker have submitted solutions to the assignment ps1:

course101/
├── gradebook.db
├── nbgrader_config.py
├── source
│   ├── header.ipynb
│   └── ps1
│       ├── jupyter.png
│       ├── problem1.ipynb
│       └── problem2.ipynb
├── release
│   └── ps1
│       ├── jupyter.png
│       ├── problem1.ipynb
│       └── problem2.ipynb
├── submitted
│   ├── bitdiddle
│   │   └── ps1
│   │       ├── jupyter.png
│   │       ├── problem1.ipynb
│   │       ├── problem2.ipynb
│   │       └── timestamp.txt
│   └── hacker
│       └── ps1
│           ├── jupyter.png
│           ├── problem1.ipynb
│           ├── problem2.ipynb
│           └── timestamp.txt
├── autograded/
└── feedback/

Database of assignments

Additionally, nbgrader needs access to a database to store information about the assignments. This database is, by default, a sqlite database that lives at {course_directory}/gradebook.db, but you can also configure this to be any location of your choosing. You do not need to manually create this database yourself, as nbgrader will create it for you, but you probably want to prepopulate it with some information about assignment due dates and students (see Managing the database).

Additionally, nbgrader uses SQLAlchemy, so you should be able to also use MySQL or PostgreSQL backends as well (though in these cases, you will need to create the database ahead of time, as this is just how MySQL and PostgreSQL work).

Configuration files

To customize nbgrader’s behavior, you can set configuration options in the nbgrader_config.py file. In particular, if you are using nbgrader with JupyterHub, you must set the course id in the nbgrader configuration file. A basic nbgrader config file would live at {course_directory}/nbgrader_config.py and might look like:

c = get_config()
c.Exchange.course_id = "course101"

There are many additional options you can configure. See Configuration options for a full list.