xml.find（）

Question

对于命名空间映射，关键字似乎不能是""。使用iterparse和start-ns动态获取命名空间似乎无法很好地发挥作用。这是一个例子：

from xml.etree.ElementTree import fromstring, iterparse
import io
s = '''<?xml version="1.0"?>
<actors xmlns:fictional="http://characters.example.com"
        xmlns="http://people.example.com">
    <actor>
        <name>John Cleese</name>
        <fictional:character>Lancelot</fictional:character>
        <fictional:character>Archie Leach</fictional:character>
    </actor>
    <actor>
        <name>Eric Idle</name>
        <fictional:character>Sir Robin</fictional:character>
        <fictional:character>Gunther</fictional:character>
        <fictional:character>Commander Clement</fictional:character>
    </actor>
</actors>'''
# root = fromstring(s)
f = io.StringIO(s)
# get namespace dynamically
ns_map = {}
for event, elem in iterparse(f, ['start-ns']):
    ns, url = elem
    ns_map[ns] = url

f = io.StringIO(s)
root = parse(f)
ns_map
#{'': 'http://uniprot.org/uniprot',
# 'xsi': 'http://www.w3.org/2001/XMLSchema-instance'}

root.find(':actor', ns_map)

会出现以下错误：

    262     try:
--> 263         selector = _cache[cache_key]
    264     except KeyError:

KeyError: (':actor', (('', 'http://people.example.com'), ('fictional', 'http://characters.example.com')))

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
<ipython-input-32-b6e4ecf5f7e9> in <module>()
----> 1 x.find(':actor', ns_map)

/Users/zech/anaconda/envs/py35/lib/python3.5/xml/etree/ElementTree.py in find(self, path, namespaces)
    647                 FutureWarning, stacklevel=2
    648                 )
--> 649         return self._root.find(path, namespaces)
    650
    651     def findtext(self, path, default=None, namespaces=None):

/Users/zech/anaconda/envs/py35/lib/python3.5/xml/etree/ElementPath.py in find(elem, path, namespaces)
    296
    297 def find(elem, path, namespaces=None):
--> 298     return next(iterfind(elem, path, namespaces), None)
    299
    300 ##

/Users/zech/anaconda/envs/py35/lib/python3.5/xml/etree/ElementPath.py in iterfind(elem, path, namespaces)
    275         while 1:
    276             try:
--> 277                 selector.append(ops[token[0]](next, token))
    278             except StopIteration:
    279                 raise SyntaxError("invalid path")

KeyError: ':'

这是一个错误吗？什么是最好的解决方案？

Answer 1

您必须为空名称空间提供非空的“别名”：

ns_map["empty"] = ns_map[""]
print(root.find('empty:actor', ns_map))

如果您的情况适用，也可以remove the namespaces out of the parsed document。