谈谈selenium4.0中的相对定位

技术分享 2年前 (2023-10-21) 0 999+

相对定位历史

2021-10-13 发布的 selenium 4.0 开始引入，selenium 3.X是没有的

implement relative locator for find_element (#9902)

4.10维护了下

Improve near relative locator behavior (#11290)

其他都是文档、异常信息方面的处理

实例演示

D:seleniumdemorelative.html

<!DOCTYPE html> <html lang="en"> <head>     <meta charset="UTF-8">     <title>relative</title> </head> <body>     DATE:<input id="date" type="text">     USER:<input id="username" type="text"><br>     CODE:<input id="code" type="text">     PASS:<input id="password" type="text"> </body> </html>

如下界面

实例代码

from selenium.webdriver.common.by import By from selenium.webdriver.support.relative_locator import locate_with   from selenium import webdriver from time import sleep driver = webdriver.Chrome() driver.get(r'D:seleniumdemorelative.html') ele_date = driver.find_element('id','date') ele_code = driver.find_element('id','code') ele_user = driver.find_element('id','username') ele_password = driver.find_element('id','password')  driver.find_element(locate_with(By.CSS_SELECTOR, "input").above(ele_code)).send_keys('code aboe') driver.find_element(locate_with(By.CSS_SELECTOR, "input").below(ele_user)).send_keys('user below') driver.find_element(locate_with(By.CSS_SELECTOR, "input").to_left_of(ele_password)).send_keys('pass left') driver.find_element(locate_with(By.CSS_SELECTOR, "input").to_right_of(ele_date)).send_keys('date right') driver.find_element(locate_with(By.CSS_SELECTOR, "input").near(ele_code)).send_keys('code near')

执行效果

相关源码说明

find_element

在find_element的源码中有这么一段

    def find_element(self, by=By.ID, value=None) -> WebElement:         if isinstance(by, RelativeBy):             elements = self.find_elements(by=by, value=value)             if not elements:                 raise NoSuchElementException(f"Cannot locate relative element with: {by.root}")             return elements[0]

也就是说你传入的by不仅仅可以是下面这8个，还可以是RelativeBy对象

class By:     """     Set of supported locator strategies.     """      ID = "id"     XPATH = "xpath"     LINK_TEXT = "link text"     PARTIAL_LINK_TEXT = "partial link text"     NAME = "name"     TAG_NAME = "tag name"     CLASS_NAME = "class name"     CSS_SELECTOR = "css selector"

那如果是RelativeBy对象的话，会去调用find_elements，self.find_elements(by=by, value=value)

    def find_elements(self, by=By.ID, value=None) -> List[WebElement]:     	if isinstance(by, RelativeBy):             _pkg = '.'.join(__name__.split('.')[:-1])             raw_function = pkgutil.get_data(_pkg, 'findElements.js').decode('utf8')             find_element_js = f"return ({raw_function}).apply(null, arguments);"             return self.execute_script(find_element_js, by.to_dict())

if语句下的2行代码就是在加载findElements.js

最后两句就是构造一个js然后去执行它，细节就不追究了

RelativeBy

这个class位于seleniumwebdriversupportrelative_locator.py

class RelativeBy:     def __init__(self, root: Dict[By, str] = None, filters: List = None):         self.root = root         self.filters = filters or []              def above(self, element_or_locator: Union[WebElement, Dict] = None) -> "RelativeBy":         if not element_or_locator:             raise WebDriverException("Element or locator must be given when calling above method")          self.filters.append({"kind": "above", "args": [element_or_locator]})         return self

这个类提供了5个用于定位的实例方法：above below to_left_of to_right_of near

可以看到RelativeBy对象的实例化需要2个参数，一个是root：dict类型，一个是filters ：列表类型

可以看到above这样的方法其实没做啥，关键是对self.filters的一个处理，增加一个对应kind(与方法同名)和args，这个args操作你要去参考的元素的定位器或WebElement

locate_with

在实例代码中，我们用到了locate_with这个函数，这个函数跟RelativeBy在同一个文件中

代码如下

def locate_with(by: By, using: str) -> "RelativeBy":     assert by is not None, "Please pass in a by argument"     assert using is not None, "Please pass in a using argument"     return RelativeBy({by: using})

可以看到它确实是返回了一个RelativeBy的实例对象

而它的用法跟我们的find_element就一致了，唯一的不同就是参数名，这边是using，find_element是value

为何用它的另一方面原因是在RelativeBy的doc中这样的一段描述

        Example:             lowest = driver.find_element(By.ID, "below")              elements = driver.find_elements(locate_with(By.CSS_SELECTOR, "p").above(lowest))