I wonder why most people defend this feature. The problem is not the annotation, you can do that in ML, too:

  Poly/ML 5.6 Release
  > 5 : int;
  val it = 5: int

But you cannot just use 42 where a type is expected:

  > 5 : 42;
  poly: : error: <identifier> expected but 42 was found
  Static Errors
  

It's pretty silly that Python did not develop an actual type system if annotations like that are supported.