I don't know if what I miss most is the samething the OP is asking for -
but the idea of re-using a value retrieved in an expression in the
same expression - without the need
to assign to a temporary variable.
Like in:
value = expensive_function(b) if expensive_function(b) else default_value
(of course this is a trivial example - but nonetheless it would require an
extra "if" statement to avoid the double call)