I think you could twist Python into getting something similarly concise one way or other ;) It might not be the Python way, though. I agree it often is painful to map. I think in particular the issue for me is visualizing the effects once you're working with a multi-dimensional set of arrays. E.g. I know what outer/product does logically, but I have to think through the effects in a way I don't need to do with a straightforward linear map(). I think I'd have been more likely to have ended up with something like this if I started from scratch even if it's not as elegant.
p textb.bytes.map{|b| (0...8).map{|i| (b>>i) & 1} }.flatten
EDIT: This is kind of embarrassing, but we can of course do just this:
textb.bytes.flat_map{_1.digits(2)}
But I think the general discussion still applies, and it's quite interesting how many twists and turns it took to arrive at that
