Record the plotly-in-Python rule for 3D figures

chapters/slides-posters-figures.qmd

@@ -216,6 +216,21 @@ Show both when the shape of the surface matters.
   but PDF and Word output show no interactive plot,
   so also provide a static view at a fixed angle
   (see [Make figures accessible](teaching.qmd#make-figures-accessible)).
+- In a Python tab, draw the interactive 3D plot with [plotly](https://plotly.com/python/3d-charts/) too,
+  so the R and Python tabs of a figure look alike.
+  Keep the `matplotlib` version for the PDF and Word output,
+  where it is the static view at a fixed angle,
+  and run it only in those outputs, the way the R tab runs its plotly code only in HTML output.
+  In a `knitr` chunk, print the figure as one raw HTML block under `results: asis`,
+  because `fig.show()` needs `ipython` and several `print` calls split the chunk's output:
+
+  ````python
+  print("```{=html}\n" + fig.to_html(full_html=False, include_plotlyjs="cdn") + "\n```")
+  ````
+
+  End each call that returns the figure, such as `add_trace` and `update_layout`, with `;`
+  so that reticulate does not print the figure after every call,
+  and add `plotly` to the page's `reticulate::py_require` list.
 - Give a 3D plot alt text that states what the surface looks like, such as "a bowl with its lowest point at ...".
 
 ::: {.callout-note collapse="true" title="Source"}