Comment by rtpg

Python is not Lisp, but jumping into a Python REPL in a halfway-run program and poking at the internals easily is _very_ useful as a debugging tool, quickly getting you answers on some messier programs.

It's a shame that other scripting languages that theoretically have the capabilities to do this don't do this (looking at you, node! Chrome dev tools are fine but way too futzy compared to `import pdb; pdb.set_trace()` and "just" using stdin)

I do also use Emacs, and with Emacs Lisp `trace-function` means you can very quickly get call traces in your running instance without having to pull out a debugger and the like. Not like you can't trace functions with `gdb` of course. But the lowered barrier to entry and the ability to do in-process debugging dynamically means you just have access to richer debugging tools from the outset.