报错

Traceback (most recent call last):
  File "F:\python3.7.0\lib\code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
  File "G:\Projects\pycharmeProject-C21\PyCharm Community Edition 213.5605.23\plugins\python-ce\helpers\pydev\_pydev_bundle\pydev_umd.py", line 198, in runfile
    pydev_imports.execfile(filename, global_vars, local_vars)  # execute the script
  File "G:\Projects\pycharmeProject-C21\PyCharm Community Edition 213.5605.23\plugins\python-ce\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "G:/Projects/pycharmeProject-C21-3-1/Scrapy/python爬虫_第5章/Chapter_5_xpath_special.py", line 21, in <module>
    content = selector.xpath('//div[start-with(@id,"test")]/text()')
  File "src\lxml\etree.pyx", line 1597, in lxml.etree._Element.xpath
  File "src\lxml\xpath.pxi", line 305, in lxml.etree.XPathElementEvaluator.__call__
  File "src\lxml\xpath.pxi", line 225, in lxml.etree._XPathEvaluatorBase._handle_result
lxml.etree.XPathEvalError: Unregistered function

在写xpath解析html的时候报了如上错误，源码如下

源码

```python
import lxml.html

html1 = '''
<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
    <div id="test-1-k">需要的内容1</div>
    <div id="test-2-k">需要的内容2</div>
    <div id="testfault-k">需要的内容3</div>
    <div id="uselessk">这是我不需要的内容</div>
</body>
</html>
'''

selector = lxml.html.fromstring(html1)
content = selector.xpath('//div[start-with(@id,"test")]/text()')
for each in content:
    print(each)

分析

这里我是想要获取 div 的id含test的文本内容，于是写了//div[start-with(@id,"test")]/text() 的xpath语句，运行时报了上面的错误，找了半天，没有发现，网上找了一堆也都没有。后来发现他的匹配规则中的方法与大部分编程的字符串方法类似，再仔细一看 start-with 漏掉了s，加上去就行了。

在这里插入图片描述