Today I learned how to debug the new Python REPL with _pyrepl.trace and the environment variable PYREPL_TRACE.
_pyrepl.trace
PYREPL_TRACE
Today I learned how to fix an issue with Ctrl+left and Ctrl+right not working in the new Python REPL on MacOS.
If there is a 50% chance something will go wrong, then 9 times out of 10 it will.