My answer here works only on the interactive Python prompt, which writes output to the screen if not stored in a variable or
None. Is such an answer valid?
In my opinion, such answers should be valid unless the OP states otherwise.
These answers often reflect a different slant to the problem, and we all like variety, don't we? I don't think we should remove this dimension of creativity by default, but if the OP doesn't want such answers, they can of course say so.
From the perspective of a code golfer, I like to avoid the overhead of output that come with some languages. Some languages (such as GolfScript) produce output automatically, so I think it's fair to use a REPL interpreter to do the same thing.