Status update week 6 GSoC

Finishing up tutorial material

We have been busy adding the final touches to the upcoming tutorial. (you can read about the tutorial in ealier blog posts).

I thought I would share a technique for doing exercises in Jupyter notebooks.

The %exercise magic

There are quite a few ways to provide exercises in jupyter notebooks (eventually I think there will be a de facto standard, either as a separate package or included with the notebook itself). But I essentially wanted a special version of %load which would load a file into a cell but replace some parts of the expressions with gaps for the tutorial attendee to fill in.

Thanks to IPython being a popular project there was already a solution posted on StackOverflow which did nearly exactly this.

After some tweaking I came up with this

import IPython.core.magic as ipym

@ipym.magics_class
class ExerciseMagic(ipym.Magics):

    @ipym.line_magic
    def exercise(self, line, cell=None):
        token = '  # EXERCISE: '
        out_lst = []
        for ln in open(line).readlines():
            if token in ln:
                pre, post = ln.split(token)
                out_lst.append(pre.replace(post.rstrip('\n'), '???') + '\n')
            else:
                out_lst.append(ln)
        out_str = '# %exercise {0}\n{1}'.format(line, ''.join(out_lst))
        self.shell.set_next_input(out_str, replace=True)

def load_ipython_extension(ipython):
    ipython.register_magics(ExerciseMagic)

def unload_ipython_extension(ipython):
    pass

The downside of using this magic is that reloading the cell requires the user to uncomment the # %exercise ... line, delete the rest of the cell and rerun it. This will only feel natural if you've already worked with the %load magic before (which in my humble opinion is suboptimal since you often want bi-directional editing whenever you pull out that magic).