pyrepl

This is pyrepl, a readline-a-like in pure Python.

It requires python 3.8 (or newer) and features:

sane multi-line editing
history, with incremental search
completion, including displaying of available options
a fairly large subset of the readline emacs-mode keybindings (adding more is mostly just a matter of typing)
a liberal, Python-style, license
a new python top-level
no global variables, so you can run two or more independent readers without having their histories interfering.
no hogging of control -- it should be easy to integrate pyrepl into YOUR application's event loop.
generally speaking, a much more interactive experience than readline (it's a bit like a cross between readline and emacs's mini-buffer)

There are probably still a few little bugs & misfeatures, but I like it, and use it as my python top-level most of the time.

To get a feel for it, just execute:

python pyrepl/pythoni.py

(One point that may confuse: because the arrow keys are used to move up and down in the command currently being edited, you need to use ^P and ^N to move through the history)