conn.execute('''CREATE TABLE IF NOT EXISTS ADDRESSDB(MacAddress CHAR(50),NewAddress  CHAR(50) );''')
    cursor = conn.cursor()
    c=cursor.execute('''SELECT * FROM ADDRESSDB''')
    r=c.fetchall()
    print(len(r))
    rr=len（r）
    此行可以使用return rr 返回
    cursor.close()