I've been doing exactly this for a while now using Emacs built-in python mode and I think it's its quite nice. With just a few keystrokes I can send any part of the code I'm working on into a running python process and see the results in a separate repl buffer. The built-in python-mode already has a good selection of possible selections to send and I've written two extra ones working with indent levels dependent on where the cursor currently is. [1] It's nice to be able to, for example, run the if statement you're currently writing without running the while loop that if statement is in.

One important thing to keep in mind though is that it is not as dynamic as Lisp, so things like re-evaluating a class definition does not update existing objects. I end up restarting the python process and evaluating the buffers I'm working on often enough that I've bound it to its own key.

[1] https://pastebin.com/ctz5erD4