在解析之前,如何检查XML中属性和标记的存在? [英] How can I check the existence of attributes and tags in XML before parsing?
问题描述
我正在通过python中的Element Tree解析XML文件,并将内容写入cpp文件.
I'm parsing an XML file via Element Tree in python and and writing the content to a cpp file.
子标签的内容将因不同标签而异.例如,第一个事件标签将party标签作为子标签,而第二个事件标签则没有.
The content of children tags will be variant for different tags. For example first event tag has party tag as child but second event tag doesn't have.
->如何在解析之前检查标签是否存在?
-->How can I check whether a tag exists or not before parsing?
->儿童在第一个事件标记中具有值属性,但在第二个事件标记中没有.在获取值之前,如何检查属性是否存在.
-->Children has value attribute in 1st event tag but not in second. How can I check whether an attribute exists or not before taking it's value.
->目前,我的代码为不存在的party标签引发了错误,并为第二个child标签设置了"None"属性值.
--> Currently my code throws an error for non existing party tag and sets a "None" attribute value for the second children tag.
<main>
<event>
<party>Big</party>
<children type="me" value="3"/>
</event>
<event>
<children type="me"/>
</event>
</main>
代码:
import xml.etree.ElementTree as ET
tree = ET.parse('party.xml')
root = tree.getroot()
for event in root.findall('event'):
parties = event.find('party').text
children = event.get('value')
我想检查标签,然后取它们的值.
I want to check the tags and then take their values.
推荐答案
如果标签不存在,则.find()
确实返回None
.只需测试该值即可:
If a tag doesn't exist, .find()
indeed returns None
. Simply test for that value:
for event in root.findall('event'):
party = event.find('party')
if party is None:
continue
parties = party.text
children = event.get('value')
您已经在事件中使用.get()
来测试value
属性;如果该属性不存在,它也会返回None
.
You already use .get()
on event to test for the value
the attribute; it returns None
as well if the attribute does not exist.
属性存储在.attrib
词典中,因此您也可以使用标准的Python技术来显式测试该属性:
Attributes are stored in the .attrib
dictionary, so you can use standard Python techniques to test for the attribute explicitly too:
if 'value' in event.attrib:
# value attribute is present.
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