Placidity can be thought as a Python wrapper that sits on top of your existing shell. This means it allows you to evaluate simple Python expressions, stash the results and perform usual actions you do on a shell. It is fairly easy to extend thanks to its architecture.
Note that output coloring depends on colorama! It works without it, though.
If you are on mac, you might want to install readline package as this enables tab completion for commands.
Placidity is available under MIT license. See LICENSE for more details.