Regarding out of order execution: how is pep 3150 any worse than "x = y if z else w"? Apart from the fact than this sort of statement is usually quite short, the middle part still gets executed before the start. Either way, out of order execution hurts readability. There's a reason that
even mathematicians usually define terms before using them.
On the other hand, I have read countless scientific papers which define functions along the lines of "this phenomenon can be represented by the equation x=2sin(yz), where x is the natural frequency, y is the height of the giraffe and z is the number of penguins". Just saying... Changing the subject slightly, I haven't studied the details of the proposed grammar, but if given can be used in simple statements, this implies that the following would be possible: def function_with_annotations() -> x given: x = 4: function_body() I assume I'm not alone in thinking that this is a really bad idea (if the current grammar does actually allow it). However, "given" in def statements would be a great way of dealing with the recently discussed question of how to define function variables at definition time: def function() given (len=len): ... David