1.包含单个class
//div[contains(@class, 'my-class')]
//div[@class="my-class"]
2.包含某多个class
//div[contains(@class, 'my-class') and [contains(@class, 'my-class1')]
3.不包含某class
//div[not(contains(@class, 'example-class'))]
4.不包含某多个class
//div[not(contains(@class, "list_th_date" ) or contains(@class, "list_th_title"))]
5.text()取内容 //div/a/text()
text()后面可以跟下标，如//div/a/text()[2]，表示取text()内容的第二部分
