Why on earth would anyone choose Python as an improvement over bash when there are several mature dynamic languages which are much better suited to shell scripting? Ruby, Perl and Lua come to mind.

    Python is a concise more expressive language

No it is not, and that's why I'd put it last on the list. Kreist, Python doesn't even have baked-in regex support. And forget one-liners - Python just doesn't cut it. Nearly everything in Python has to be fully qualified which works against conciseness. Sure, you can import a function but it isn't idiomatic Python.

    It has a massive built-in library

So does Ruby which also has so many more methods built into the kernel that you don't end-up having to fully qualify everything, eg. random.random().