浏览器界面元素定位常用方法

定位方法	对应python webdriver方法
id	find_element_by_id()
name	find_element_by_name()
class name	find_element_by_class_name()
tag name	find_element_by_tag_name()
link text	find_element_by_link_text()
partial link text	find_element_by_partial_link_text()
xpath	find_element_by_xpath()
css selector	find_element_by_css_selector()