I wanted to use template strings for a long time in Python side of Bokeh. I already use them quite extensively in BokehJS. As an example, I would like to replace this (see examples/models/widgets.py):

select.title = HTML("Selected value: <b>", ValueOf(select, "value"), "</b>")

with

select.title = HTML(t"Selected value: <b>{ValueOf(select, "value")}</b>")

Maybe even HTML() could be dropped from this variant.

The release pipeline automation has a custom log class with a scrubber to prevent leaking credentials in the output, I can imagine re-implementing that to take advantage of template strings and a custom formatter with the standard logger in the future. There might be opportunities to use them in other logging contexts as well.

Another case could be CustomJS, where we could infer args from code.