My recent attempt to migrate users' grades for assignments from a pre-Canvas course to Canvas starts by adding the users to a Canvas course, then adding the assignments, and then finally adding each student's grade for each assignment.
Of course such a program requires testing. This testing creates lots of enrollments for users. In order to run the program again it is very convenient to remove these users. Similarly there is a need to remove the created assignments. Hence I wrote two scripts: (1) to remove users (except for myself) and (2) to remove all assignments.
You can find the code for them at Removing other users and assignments: Chip sandbox .
One of the small gotchas that I found is that to remove a user from enrollment in a course you need to use the user's enrollment_id and not their canvas_id.