Maybe it's a crazy idea, but what if we could decorate a single line of code? For example:
@Timer a = time_consuming_function()
This will be equivalent to using Steven's context manager, but the decorator is more simple to comment and uncomment.
Maybe it could be possible to comment also code blocks:
@parallel for x in y: do_something(x) now_something_completely_different(x)
This could be a shortcut for multiprocessing.