I have a rule that helps with hidden state and out-of-order execution. Once in a while I do a "restart kernel and run all cells." If doing that breaks anything,

I have a rule that helps with hidden state and out-of-order execution. Once in a while I do a "restart kernel and run all cells." If doing that breaks anything, then I have to fix it. But it also ensures that a notebook is reproducible later on. Of course I don't have things that take hours to run. It would be nice if there were something that would make out-of-order problems light up, the way that code editors can highlight errors while you're editing. A limitation of "browser as editor" is that it misses out on some of the powerful things that code editors do today. Another thing is to put things in functions, so temporary variables are disposed of. That's a halfway step to putting things in .py files. A benefit if .py files is not always that jupyter is bad, but that variable scoping is good hygiene.