bpo-37903: IDLE: Shell sidebar with prompts (take #2) by taleinat · Pull Request #22682 · python/cpython

Prompts are now marked in the text by adding the "console" tag to
the newline character ('\n') before the beginning of the line.  This
works around issues with the prompt itself usually no longer being
written in the text widget.

With another small fix to the PyShell.recall() method, input lines
can now be recognized consistently by checking for the "stdin" tag.

This is much better than attempting to separately track the prompt
and input lines, since those are difficult to keep up to date after
undo/redo actions and squeezing/unsqueezing of previous output.