在Linux服務器上安裝lxml

最近新接的活，第一個任務是處理一堆xml格式的專利文件，把裏面的有效信息提取出來

由於公司的相關規定不容許把文件down到本地處理，只能在對方提供的遠程服務器上寫代碼

因爲xml裏面的元素是XXX:YYYY這種帶前綴的格式，用xml.etree的ElementTree死活解析不出來，最後從OverStack上找到了解釋

ElementTree is not too smart about namespaces. You need to give the .find(), findall() and iterfind() methods an explicit namespace dictionary. This is not documented very well:

namespaces = {'owl': 'http://www.w3.org/2002/07/owl#'} # add more as needed root.findall('owl:Class', namespaces)

Prefixes are only looked up in the namespaces parameter you pass in. This means you can use any namespace prefix you like; the API splits off the owl: part, looks up the corresponding namespace URL in the namespaces dictionary, then changes the search to look for the XPath expression {http://www.w3.org/2002/07/owl}Class instead.

If you can switch to the lxml library things are better; that library supports the same ElementTree API, but collects namespaces for you in a .nsmap attribute on elements.

因而果斷去裝lxml

服務器上已經裝了python2.7，然而除此以外的東西全都沒有，所以又手動裝了pip

執行pip install lxml 報了一大堆錯，注意到：

Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?

查到lxml還須要先安裝依賴庫libxml2和libxslt的開發版

yum install libxml2-devel

yum install libxslt-devel

安裝好依賴庫後pip仍是報錯

此次又認真讀了一遍錯誤信息發現前面竟然還有一行：

unable to execute gcc: No such file or directory

好吧，連gcc都沒有安裝，難怪沒法編譯

yum install gcc

安裝好之後pip install，竟然，仍是報錯！

src/lxml/lxml.etree.c:84:20: 致命錯誤：Python.h：沒有那個文件或目錄

再查資料，原來還須要安裝一個python-devel，這是Python的頭文件和靜態庫包

yum install python-devel

安裝完以後再次pip install lxml

終於見到了喜聞樂見的

Successfully installed lxml

至此，linux下的lxml安裝完成