从 lxml 中选择属性值

问题描述

我想使用 xpath 表达式来获取属性的值.

I want to use an xpath expression to get the value of an attribute.

我希望以下工作

from lxml import etree

for customer in etree.parse('file.xml').getroot().findall('BOB'):
    print customer.find('./@NAME')

但这给出了一个错误:

Traceback (most recent call last):
  File "bob.py", line 22, in <module>
    print customer.find('./@ID')
  File "lxml.etree.pyx", line 1409, in lxml.etree._Element.find (src/lxml/lxml.etree.c:39972)
  File "/usr/local/lib/python2.7/dist-packages/lxml/_elementpath.py", line 272, in find
    it = iterfind(elem, path, namespaces)
  File "/usr/local/lib/python2.7/dist-packages/lxml/_elementpath.py", line 262, in iterfind
    selector = _build_path_iterator(path, namespaces)
  File "/usr/local/lib/python2.7/dist-packages/lxml/_elementpath.py", line 246, in _build_path_iterator
    selector.append(ops[token[0]](_next, token))
KeyError: '@'

我期望这会起作用吗?

推荐答案

find 和 findall 只实现 XPath 的一个子集.它们的存在是为了提供与其他 ElementTree 实现(如 ElementTree 和 cElementTree)的兼容性.

find and findall only implement a subset of XPath. Their presence is meant to provide compatibility with other ElementTree implementations (like ElementTree and cElementTree).

相比之下，xpath 方法提供对 XPath 1.0 的完全访问:

The xpath method, in contrast, provides full access to XPath 1.0:

print customer.xpath('./@NAME')[0]

但是，您可以改为使用 get:

However, you could instead use get:

print customer.get('NAME')

或属性:

print customer.attrib['NAME']