xmlns命名空间破坏lxml

时间:2013-08-05 21:12:25

标签: python namespaces lxml xml-namespaces

我正在尝试打开xml文件,并从某些标记中获取值。我做了很多,但这个特殊的xml给了我一些问题。以下是xml文件的一部分:

<?xml version='1.0' encoding='UTF-8'?>
<package xmlns="http://apple.com/itunes/importer" version="film4.7">
  <provider>filmgroup</provider>
  <language>en-GB</language>
  <actor name="John Smith" display="Doe John"</actor>
</package>

以下是我的python代码示例:

metadata = '/Users/mylaptop/Desktop/Python/metadata.xml'
from lxml import etree
parser = etree.XMLParser(remove_blank_text=True)
open(metadata)
tree = etree.parse(metadata, parser)
root = tree.getroot()
for element in root.iter(tag='provider'):
    providerValue = tree.find('//provider')
    providerValue = providerValue.text
    print providerValue
tree.write('/Users/mylaptop/Desktop/Python/metadataDone.xml', pretty_print = True, xml_declaration = True, encoding = 'UTF-8')

当我运行它时,找不到提供者标签或其值。如果我删除xmlns="http://apple.com/itunes/importer",那么所有工作都按预期进行。 我的问题是如何删除这个命名空间,因为我对此并不感兴趣,所以我可以使用lxml获取我需要的标记值?

2 个答案:

答案 0 :(得分:10)

provider标记位于http://apple.com/itunes/importer命名空间中,因此您需要使用完全限定名称

{http://apple.com/itunes/importer}provider

或使用其中一个the namespaces parameter的lxml方法,例如root.xpath。然后,您可以使用命名空间前缀(例如ns:provider)指定它:

from lxml import etree
parser = etree.XMLParser(remove_blank_text=True)
tree = etree.parse(metadata, parser)
root = tree.getroot()
namespaces = {'ns':'http://apple.com/itunes/importer'}
items = iter(root.xpath('//ns:provider/text()|//ns:actor/@name',
                       namespaces=namespaces))
for provider, actor in zip(*[items]*2):
    print(provider, actor)

产量

('filmgroup', 'John Smith')

请注意,上面使用的XPath假定<provider><actor>元素始终显示为交替显示。如果不是这样,那么当然有办法处理它,但代码变得更加冗长:

for package in root.xpath('//ns:package', namespaces=namespaces):
    for provider in package.xpath('ns:provider', namespaces=namespaces):
        providerValue = provider.text
        print providerValue
    for actor in package.xpath('ns:actor', namespaces=namespaces):
        print actor.attrib['name']

答案 1 :(得分:1)

我的建议是不要忽略命名空间,而是要考虑它。我为django-quickbooks库上的工作编写了一些相关的函数(经过轻微修改后复制)。有了这些功能,您应该可以这样做:

providers = getels(root, 'provider', ns='http://apple.com/itunes/importer')

以下是这些功能:

def get_tag_with_ns(tag_name, ns):
    return '{%s}%s' % (ns, tag_name)

def getel(elt, tag_name, ns=None):
    """ Gets the first tag that matches the specified tag_name taking into
    account the QB namespace.

    :param ns: The namespace to use if not using the default one for
    django-quickbooks.
    :type  ns: string
    """

    res = elt.find(get_tag_with_ns(tag_name, ns=ns))
    if res is None:
        raise TagNotFound('Could not find tag by name "%s"' % tag_name)
    return res

def getels(elt, *path, **kwargs):
    """ Gets the first set of elements found at the specified path.

    Example:
        >>> xml = (
        "<root>" +
            "<item>" +
                "<id>1</id>" +
            "</item>" +
            "<item>" +
                "<id>2</id>"* +
            "</item>" +
        "</root>")
        >>> el = etree.fromstring(xml)
        >>> getels(el, 'root', 'item', ns='correct/namespace')
        [<Element item>, <Element item>]
    """

    ns = kwargs['ns']

    i=-1
    for i in range(len(path)-1):
        elt = getel(elt, path[i], ns=ns)
    tag_name = path[i+1]
    return elt.findall(get_tag_with_ns(tag_name, ns=ns))