My two favourite things are named arguments and pattern-matching with guards, along with the |> operator (though the latter could easily be implemented in Haskell).
All in all, it's a combination of features (and a lesser enthusiasm for ASCII-heavy combinators-based DSLs) which makes for code that is potentially as readable as Python.
A potential synonym for 'potentially as readable as' is
'in practice, never as readable as'. Especially when we're talking about heavy use of user-defined syntax to hide whatever's actually going to have to be maintained about this code. It's the dark side of "DSLs"
I use "potentially" because people will find a way to write unreadable Python the same way they'll write unreadable anything else. And what I was saying about OCaml is that you find less user-defined syntax than Haskell, though you do find it (eg, the LWT syntax extension, which in my experience helps rather hinders readability).
