python操作postgreSQL数据库

#!/usr/bin/python
import psycopg2
from datetime import datetime

db_host = "xxxxxx-esb-xx.xxxxx.xx-xxxx.rds.xxxxx.com"
db_port = 5432
db_name = "xxx"
db_user = "xxx"
db_pass = "xxxx"
db_table = "xxxxx"
biller_code = "111111"
biller_short_name = "test_short"
biller_long_name = "test_long"

def make_conn():
    conn = None
    try:
        conn = psycopg2.connect("dbname=‘%s‘ user=‘%s‘ host=‘%s‘ password=‘%s‘" % (db_name, db_user, db_host, db_pass))
        print "connected to postgres db successfully"
    except:
        print "I am unable to connect to the database"
    return conn


try:
    connection = make_conn()
    cursor = connection.cursor()
    cursor.execute("SELECT * FROM billers where biller_code = ‘%s‘;" % biller_code)
    numOfRows = cursor.rowcount
    print("%s rows found for the biller code: %s" % (numOfRows, biller_code))
    if(numOfRows<=0):
        dt = datetime.now()
        cursor.execute("insert into billers (biller_code, biller_short_name, biller_long_name, active, min_length, max_length, reg_exp, check_digit_algo, created_at, updated_at) values (%s, %s, %s, true, 0, 100, ‘NONE‘, ‘NONE‘, %s, %s)", (biller_code, biller_short_name, biller_long_name, dt, dt))
        connection.commit()
        print("inserted %s rows successfully" % cursor.rowcount)
except (Exception, psycopg2.Error) as error :
    print ("Error caught", error)
finally:
    #closing database connection.
        if(connection):
            cursor.close()
            connection.close()
            print("PostgreSQL connection is closed")