python鐨剎path(【Python】Xpath 解析报错 ：lxml.etree.XPathEvalError: Unregistered function)

Traceback (most recent call last):
  File "F:python3.7.0libcode.py", line 90, in runcode
    exec(code, self.locals)
  File "", line 1, in 
  File "G:ProjectspycharmeProject-C21PyCharm Community Edition 213.5605.23pluginspython-cehelperspydev_pydev_bundlepydev_umd.py", line 198, in runfile
    pydev_imports.execfile(filename, global_vars, local_vars)  # execute the script
  File "G:ProjectspycharmeProject-C21PyCharm Community Edition 213.5605.23pluginspython-cehelperspydev_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 
    content = selector.xpath('//div[start-with(@id,"test")]/text()')
  File "srclxmletree.pyx", line 1597, in lxml.etree._Element.xpath
  File "srclxmlxpath.pxi", line 305, in lxml.etree.XPathElementevaluator.__call__
  File "srclxmlxpath.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

```python
import lxml.html

html1 = '''



    
    


    需要的内容1
    需要的内容2
    需要的内容3
    这是我不需要的内容


'''

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

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。