how to vacuum thru psycopg

I am using psycopg 2.0.8 and want to vacuum my postgresql database as I
fill it. I found out that some of what I am seeing performance wise is
the database needing to optimize for my queries and insertions. So, I
was told to vacuum it occasionally. So, I tried to do it in my program
as it grew. The error says it all:

  File
"/home/niessner/Projects/PictureLibrary/Source/PictureLibrary/Model/DB/PostgresqlWithPsycopg/actions.py", line 247, in transactionClose
    if len (ids) == 10**int(log10 (len (ids))): self.__execute("vacuum
full", close=False, query=False)
  File
"/home/niessner/Projects/PictureLibrary/Source/PictureLibrary/Model/DB/PostgresqlWithPsycopg/actions.py", line 92, in __execute
    self.__cursor.execute (command)
psycopg2.InternalError: VACUUM cannot run inside a transaction block


So, if I cannot do it with a cursor, then how do I do it? I have 20000
large, complex items to add and time is growing linearly and will take
years to complete at its growth rate. However, if I can vacuum once in a
while, then I can keep the time down to finish in a week or two.

As always, thanks in advance for any and all help.

-- 
Al Niessner

I have never found the companion that was so companionable as solitude.
- From Walden by Henry David Thoreau

The universe is indifferent, and life is brutal; however, it is man's
choice of behavior that makes them malevolent rather than benevolent.

Some will fall in love with life and drink it from a fountain
That is pouring like an avalanche coming down the mountain.
- From the song Pepper by the Butthole Surfers