Allow for nested Jupyter code cells

It would be very useful to be able to nest Jupyter code calls based on indentation. This would make it possible to run for example just a part of a loop. For example:

# %% < -- top-level cell
j = 0
for i in range(10):
    # %% < -- sub cell 1
    print(i)
    # %% < -- sub cell 2
    for k in range(10):
        # %% < -- sub sub cell 1
        print(i * i)
    # %% < -- sub cell 3
    j += i
# %%  < -- another top-level cell
print(j)

in this scenario triggering the outer cell would run the entire loop, while the inner cell would only run the code inside the loop. This would be especially useful during data cleaning, where the processing step needs to be fine-tuned before being run on the whole dataset. If it makes the implementation more convenient, the inner cells could also be designated by adding additional percent characters for each nesting level, i.e.: # %% - top-level cell, # %%% - subcell, # %%%% - subsubcell etc.

[PALuczak]

While there is some slight overlap with #1471, the approach proposed here is significantly more flexible as it would allow for more incremental splits. Oftentimes, either the first or the last step in the loop is costly (i.e. getting/saving data) so being able to split it from the other steps would be quite useful.

Additionally, as mentioned in my previous comment, being able to specify blocks manually would be very useful in education as it would allow for creating step-by-step tutorials for students.

[amunger]

thanks for the suggestion, unfortunately I don’t think there is enough interest for us to prioritize this feature