python中的lxml xpath,如何处理丢失的标签? [英] lxml xpath in python, how to handle missing tags?
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问题描述
假设我要使用以下XML解析一个lxml xpath表达式
suppose I want to parse with an lxml xpath expression the folowing xml
<pack xmlns="http://ns.qubic.tv/2010/item">
<packitem>
<duration>520</duration>
<max_count>14</max_count>
</packitem>
<packitem>
<duration>12</duration>
</packitem>
</pack>
是 http://python-thoughts.blogspot.fr/2012/01/default-value-for-text-function-using.html
如何实现对不同元素的解析,这些元素一旦被压缩(在zip或izip python函数意义上)就会给我
How can I achieve a parsing of the different elements that would give me once zipped (in the zip or izip python function sense)
[(520,14),(12,None)]
[(520,14),(12,None)]
?
第二个packitem中缺少的max_count
标记使我无法获得所需的东西.
The missing max_count
tag in the second packitem holds me back from getting what i want.
推荐答案
def lxml_empty_str(context, nodes):
for node in nodes:
node.text = node.text or ""
return nodes
ns = etree.FunctionNamespace('http://ns.qubic.tv/lxmlfunctions')
ns['lxml_empty_str'] = lxml_empty_str
namespaces = {'i':"http://ns.qubic.tv/2010/item",
'f': "http://ns.qubic.tv/lxmlfunctions"}
packitems_duration = root.xpath('f:lxml_empty_str('//b:pack/i:packitem/i:duration)/text()',
namespaces={'b':billing_ns, 'f' : 'http://ns.qubic.tv/lxmlfunctions'})
packitems_max_count = root.xpath('f:lxml_empty_str('//b:pack/i:packitem/i:max_count) /text()',
namespaces={'b':billing_ns, 'f' : 'http://ns.qubic.tv/lxmlfunctions'})
packitems = zip(packitems_duration, packitems_max_count)
>>> packitems
[('520','14'), ('','23')]
http://python- Thoughts.blogspot.fr/2012/01/default-value-for-text-function-using.html
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