It is not pythonic because the syntax should be:
stdout.append("Hello World")
or
stdout += "hello world"
Disclaimer: I like Python really.
On a serious note ...
I think that Python's object model and 'Implement it yourself' approach to things like attribute visibility is great. I think that this 'everything is an object' approach to OOP, and even the objects defined as a collection of objects structure is very clear-minded.
What I fear Python will do is become a language that doesn't present it's intentions in a clear way ... and I would hate to see the beauty of the principles get bogged down in over-thinking the already unconventional syntax presentation. Sort of like Lisp, beautiful in it's structure, grim, imho in it's syntax.