[Python-ideas] decorator vs. 'with' analogy [was: Syntax for loop invariants]

Andrew Barnert via Python-ideas writes:

[A] context manager seems perfect. It allows you to hint any statement, including a loop statement, by adding whatever code you want that gets run before and after the statement.

I wonder: The analogy "decorator : function :: with : suite" seems useful here. Is it useful in general? Steve