how to pass in bind variables with cursor.copy_expert?

I need to extract some rows from a table as a CSV file, based on a
query sort of like:

    copy (
        select *
        from blah
        where x = %(x)s
    )

but I don't see how to pass in a dictionary with values for the query!

Is this not allowed?

What am I missing?

Thanks in advance.

Matt

--
W. Matthew Wilson
matt@tplus1.com
http://tplus1.com