Използвайте ISOLATION_LEVEL_AUTOCOMMIT, разширение psycopg2:
Не се стартира транзакция при издаване на команда и не се изисква commit() или rollback().
import psycopg2
from psycopg2 import sql
from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT # <-- ADD THIS LINE
con = psycopg2.connect(dbname='postgres',
user=self.user_name, host='',
password=self.password)
con.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT) # <-- ADD THIS LINE
cur = con.cursor()
# Use the psycopg2.sql module instead of string concatenation
# in order to avoid sql injection attacs.
cur.execute(sql.SQL("CREATE DATABASE {}").format(
sql.Identifier(self.db_name))
)