如何在 XPath 表达式中使用 Python 变量? [英] How to use Python variable in an XPath expression?

问题描述

我试图从这个网站 https://www.quora.com/profile/Karan-Bansal-3/followers

I am trying to get all the followers name from this website https://www.quora.com/profile/Karan-Bansal-3/followers

由于不是一次加载整个页面，我每次都在循环中使用它:

Since the whole page is not loaded at once, I am using this everytime in a loop :

driver.execute_script("window.scrollTo(0, document.body.scrollHeight);")

现在由于我无法一次选择所有元素，我尝试使用索引来查找循环中的元素.

Now since I can't select all the element at once, I am trying to use indexing to find the element in the loop.

people = driver.find_element_by_xpath("//div[@class='pagedlist_item'][i]/*/div[@class='ObjectCard-header']/a[@class='user']")

这里如您所见，我正在尝试使用 [i] 提供索引，这显然不起作用并代替它，如果我提供 [1] 或任何有效的数字好.那么如何才能一一选择元素.

Here as you can see, I am trying to give the indexing using [i] which clearly doesn't work and in place of it, if I give [1] or any number it works well. So how can I select the element one by one.

代码片段:

i=1
target = open(filename,'w')
driver.get('https://www.quora.com/profile/Karan-Bansal-3/followers')
while True:
driver.execute_script("window.scrollTo(0, document.body.scrollHeight);")
people = driver.find_element_by_xpath("//div[@class='pagedlist_item'][i]/*/div[@class='ObjectCard-header']/a[@class='user']")
target.write(people.text)
target.write("\n")
i = i+1

推荐答案

在宿主语言中使用字符串连接，以便在构造 XPath 之前评估 i.否则，[i] 是对 i 元素存在的谓词测试.您没有说明您的托管语言是什么，但假设字符串连接是 "string" + "string":

Use string concatenation in the hosting language so that i is evaluated before constructing the XPath. Otherwise, [i] is a predicate testing for the presence of an i element. You didn't state what your hosting language is, but assuming string concatenation is "string" + "string":

 "//div[@class='pagedlist_item'][" + i + "]/*/div[@class='ObjectCard-header']/a[@class='user']"

另见:如何将可变参数传递到 XPath 表达式中?

更新:好的，所以您在 Python 中托管 XPath.

Update: Ok, so you're hosting XPath in Python.

如果您首先通过 str(i) 将 i 转换为字符串，则可以使用 + 进行连接，

You can use + to concatenate above if you first cast i to a string via str(i),

 "//div[@class='pagedlist_item'][" + str(i) + "]/*/div[@class='ObjectCard-header']/a[@class='user']"

或者您可以使用我提供的链接中使用的 format() :

or you can use format() as is used in the link I provided:

 "//div[@class='pagedlist_item'][{}]/*/div[@class='ObjectCard-header']/a[@class='user']".format(i)

无论哪种方式，将上述构造的 XPath 表达式放入您对 find_element_by_xpath() 的调用中，您的问题就应该得到解决.

either way, place the above constructed XPath expressions into your call to find_element_by_xpath() and your problem should be solved.

警告:不要将这种方法用于 i 的不可信值，否则您可以打开代码到 XPath 注入攻击.

Caution: Do not use this approach with untrusted values for i or you could open your code to XPath injection attacks.

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