Psycopg接口是一套提供给用户的API方法，本节将对部分常用接口做具体描述。
psycopg2.connect()
connection.cursor()
cursor.execute(query,vars_list)
curosr.executemany(query,vars_list)
connection.commit()
connection.rollback()
cursor.fetchone()
cursor.fetchall()
cursor.close()
connection.close()