psycopg problem

Hello,

I'm trying to use psycopg2 to create tables in a database using:

run = "S90040"
curs.execute("create table %s (date text, tset text)",(run,))

but it fails with

Traceback (most recent call last):
  File "write_xy_to_pg_psyco.py", line 44, in ?
    curs.execute("create table %s (date text, tset text)",(run,))
psycopg2.ProgrammingError: syntax error at or near "'S90040'" at
  character 14

If I run

curs.execute("create table S90040 (date text, tset text)",(run,))

it works perfectly, so I assume the quoting is messed up.

Could someone please tell me what I'm doing wrong?

Thanks,

Roger Mason