A few previous shells based on Python:
Apparently, Tako is a fork of Xonsh, but apart from that each has a different approach to embed Python in a shell. In pysh, commands become functions; in Marcel, Python is in parentheses, and in Xonsh, everything that is not valid python is interpreted as a command.
IMHO, I think that shells and Python have too different syntax, that it would be better to define a single syntax model and stick to it for everything instead of mixing. A shell is too powerful and crude: if you want to improve a shell, you should make it safer, not more ambiguous.
(Not that any of these don't have any good ideas, because they do.)
For an example of horror, see this Xonsh:
>>> ls = 44
>>> l = 2
>>> ls -l
42
>>> del ls
>>> ls -l
total 0