Executing code before/after each cell

[nobodyinperson]

Hi,

I was wondering if it is possible to make it so that before (or after) each cell a certain function is run?

For example, I always use %matplotlib notebook for interactive plots, but when I want to do a new plot in a new cell, I must either again execute %matplotlib notebook or close all plots by running plt.close("all"), otherwise the plots gets shown in the previous interactive window. It would be very convenient to have Jupyter run plt.close("all") before (or after) each cell in this case.

I'm surely not the only one annoyed by this %matplotlib notebook behaviour (see #1151) and in this case it might just be a long-running bug with that, but and in general there certainly are other uses for some kind of before/after cell hooks.

What do you think?