Colin Brown Understanding and Visualizing Dependencies between Notebook Cells | JupyterCon 2023

In Jupyter IPython notebooks, variable declarations are global, so a variable defined in one cell can be referenced, mutated, or redefined in any other cell. Each reference or mutation leads to a cell dependency where one cell should be executed before the other because these dependencies can span the entire notebook and understanding which cells need to be re-executed after a change can be challenging. “Run all” strategies rely on top-down ordering that can be broken by modifying or inserting cells and may also cause needless execution of cells that do not require updates. A reactive kernel can automatically update the necessary cells when cell dependencies are captured and non-circular (e.g., in dataflow notebooks). However, there may still be cases (e.g., long-running computations) where that solution is problematic. In this talk, we present two interactive visualization techniques, the minimap, and cell dependency graph, that let users examine and navigate cell dependencies and show how this helps them understand, organize, and execute notebook cells. Minimap One approach is to create a map of cells in the notebook linked according to their dependencies; a “minimap” reduces each cell to a point labeled by a truncated line of code and mirrors the top-down cell ordering in the notebook. Edges connect these points to show dependencies between cells, but most edges are hidden until a cell is selected. When a cell is selected, cells that are upstream or downstream of it shift left or right, respectively, to show dependencies, and immediate dependencies are connected with lines. These interactions allow users to easily understand the impact of changing cells and resolve misunderstandings about dependencies. For example, when given a notebook with a cell that loads in data, we can quickly know all the cells that this data depends on in our notebook and which cells must be re-run as a result of our changes. Observable, a Javascript notebook environment, introduced this