How do I put a SQLAlchemy label on the result of an arithmetic expression?

Question

How do I translate something like this into SQLAlchemy?

select x - y as difference...

I know how to do:

x.label('foo')

...but I'm not sure where to put the ".label()" method call below:

select ([table.c.x - table.c.y], ...

Answer 1

The ColumnElement method is just a helper; canonical usage is along the lines of the following:

select([sql.expression.label('foo', table.c.x - table.c.y), ...])

See the documentation.