BUG

rating=driver.find_element(By.CLASS_NAME,'ll rating_num').text

DEBUG

Message: Compound class names are not allowed.
类名不允许带空格。
即便浏览器里看到的类名是"ll rating_num"，实际类名是"rating_num"。
修改代码为：

rating=driver.find_element(By.CLASS_NAME,'rating_num').text