On page <https://docs.python.org/3.6/_sources/library/stdtypes.txt>, the following program is listed.

It raises a syntactic error.

An empty line is missing after "...     n += val" to close the loop body. 

   >>> # iteration
   >>> n = 0
   >>> for val in values:
   ...     n += val
   >>> print(n)
   504

This is the standard way that we write examples.  Sprinkling in extra blank lines everywhere would make the examples less readable.  One you've learned how the command interpreter works, the examples are clear, so you each beginner only has to learn this once (and I believe it is explained in the tutorial, though I haven't checked).