On matplotlib master, executing a cell that displays a plot steals focus from the jupyter notebook with the %matplotlib notebook magic enabled. By 'steals focus' I mean that the only key combination that will interact with the notebook is shift+enter, which @tacaswell tells me is because matplotlib special cases that one. I'm conflicted by this behavior, as, I can see compelling arguments for both stealing keyboard focus and NOT stealing keyboard focus. I personally like using the notebook keyboard shortcuts (up arrow to move up, down arrow to move down, 00 to restart the kernel, etc...), so this is very disruptive behaviour to my work flow. I would be happy with a new keyboard shortcut in the matplotlib notebook front-end that returns focus to the notebook.