## Why Most Data Science Notebooks Die After Day One: How to Build Ones That Survive Six habits that keep a notebook runnable after you close the laptop. A notebook dies the moment "Restart Kernel and Run All" stops working. Nobody notices for a week. The analysis was finished, the chart went into a deck, the file got pushed. Then someone asks where a number came from; you open the notebook, run it from the top, and cell 12 throws a KeyError on a column you renamed in cell 31 and deleted in cell 44. The output cells still show the old numbers, so the notebook looks fine while being…