You might be interested in Elvish, which aims to be a pleasant glue language (with support for arrays, hashmaps, closures, and passing JSON streams from one command to another) as well as a pleasant interactive environment.
The last I heard about Oil Shell, they’d given up on writing a whole new shell language and decided to let scripts “opt in” to more sensible behaviour for the traditional Bourne-like syntax. It’s probably the right move, overall. Also, while Oil was originally written in Python, they’ve forked the interpreter heavily customised it, and they’re investigating ways to automatically convert it to C/C++ — so it’s not really “implemented in Python” in the same way that most things are.
Oops! Can you guess which project’s README I copied and edited when I set up this project? kakoune-state-save is a plugin to automatically restore the cursor position when you re-open a file, and to help restore previous sessions’ command history and search history when you start a new session. It has its own thread, too.