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In Python, expressions return values.  Statements don't. 
That's fundamental to the language.

In any case, such a proposal is too broad to discuss here. 
If you'd like to proceed, please write a PEP.  See
http://www.python.org/peps/pep-0001.html for the procedure.

Better yet, please discuss it on comp.lang.python
(python-list@python.org) first.