the idea is to make an variable assignment at the same time that the existence of that variable -- which is being returned by a function -- is made. suppose we are returning a variable from the method 'get' from the 'request' object and them making some stuff with it, but that stuff we will only do if it exists, if not, we'll just pass, instead of writing: variable = self.request.get('variable') if variable: print variable we could write if self.request.get('variable') as variable: print variable seems stupid (or not?), but with lots of variables to process, this pre-assignment could be very unpleasant -- especially if, as the in the example case, very little use will be made of the tested variable. also, the "as" expression already exists and is very pythonic.