Python 操作并保存 XML，更改一个属性

Question

我有这个 xml：

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <SOAP-ENV:Body>
        <m:request xmlns:m="http://www.datapower.com/schemas/management" domain="XXXXX">
            <m:do-action>
                <FlushDocumentCache>
                    <XMLManager class="XMLManager">default</XMLManager>
                </FlushDocumentCache>
                <FlushStylesheetCache>
                    <XMLManager class="XMLManager">default</XMLManager>
                </FlushStylesheetCache>
            </m:do-action>
        </m:request>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

我只想更改域属性的值 XXXXX。

我做了这样的事情：

import xml.etree.ElementTree as etree
tree = etree.parse('input.xml')
# HOW TO FIND THE VALUE XXXXX AND CHANGE IT WITH A NEW VALUE ???
tree.write('output.xml')

谢谢。

Answer 1

几句话：

• 您将看到解析 xml 字符串（来自文件）然后将其写入另一个文件，不会产生相同的结果，因为解析器会更改它。您可以通过简单地运行您发布的代码来测试它（显然是第 3 行）：

  import xml.etree.ElementTree as etree
  tree = etree.parse('input.xml')
  tree.write('output.xml')
  

• 所有 SOAP-ENV:* 节点已转换为 ns0*，m* 节点已转换为 ns1*。为此，我必须将它们从 xml 文件复制到代码中（soap_env_ns_name 和 m_ns_name 变量），如下所述：Saving XML using ETree in Python. It's not retaining namespaces, and adding ns0, ns1 and removing xmlns tags。

• SOAP-ENC 和默认命名空间（xsi 和 xsd）已被删除，因为它们在xml。此外，m 已从 request 节点移动到 Envelope（根）节点；我不确定它是否是标准的一部分，但在大多数 XML 中，我看到命名空间是在根节点中声明的。反正这里也无能为力 Python的解析器不是很聪明。

• 底线是您不会得到完全相同的输出（除非您想编写自己的解析器，如下所述：Python: Update XML-file using ElementTree while conserving layout as much as possible）。

因此，代码对 XML 结构非常严格（丑陋但不是最丑陋的），如果结构发生变化，代码也需要更新（这里我不是在谈论命名空间的变通方法):

@EDIT1：添加了for 循环来注册命名空间，之前的版本就像我在第二个项目符号中描述的那样。但是在运行它时，它确实将 X s 替换为 Y s。

@EDIT2：注释掉了domain属性值测试，所以现在值无论如何都会改变。

import xml.etree.ElementTree as ET

env_node_name = "Envelope"
body_node_name = "Body"
request_node_name = "request"
domain_attr_name = "domain"
domain_attr_val = "XXXXX"
domain_attr_new_val = "YYYYY"

#Gainarie: those are the namespaces from the xml file
soap_env_ns_name = "SOAP-ENV"
m_ns_name = "m"
#soap_enc_ns_name = "SOAP-ENC"
#xsi_ns_name = "xsi"
#xsd_ns_name = "xsd"

namespaces_dict = {
    soap_env_ns_name: "http://schemas.xmlsoap.org/soap/envelope/",
    m_ns_name: "http://www.datapower.com/schemas/management",

    # Those are simply ignored by the parser as they're not referenced in our xml.
    #"SOAP-ENC": "http://schemas.xmlsoap.org/soap/encoding/",
    #"xsi": "http://www.w3.org/2001/XMLSchema-instance",
    #"xsd": "http://www.w3.org/2001/XMLSchema",
}


def tag(ns, name):
    return "{" + ns + "}" + name


for key in namespaces_dict.keys():
    ET.register_namespace(key, namespaces_dict[key])

tree = ET.parse("input.xml")
root = tree.getroot()
env_gen = root.iter(tag(namespaces_dict[soap_env_ns_name], env_node_name))
try:
    for env in env_gen:
        body_gen = env.iter(tag(namespaces_dict[soap_env_ns_name], body_node_name))
        try:
            for body in body_gen:
                request_gen = body.iter(tag(namespaces_dict[m_ns_name], request_node_name))
                try:
                    for request in request_gen:
                        if domain_attr_name in request.keys():
                            # Now, I didn't fully understand the question:
                            # you want to change the value of the 'domain' attribute (in your xml example: "XXXXX") to - let's say - "YYYYY"  (as my code does) on one of the 2 below cases:
                            # 1: change it only if current value is "XXXXX"
                            # 2: change it regardless of the current value
                            # if it's 1, then that's OK, but if it's 2, you'll have to comment the very below 'if domain_attr_val ...' line (prepend it by a # - just like the current one)
                            #if domain_attr_val == request.get(domain_attr_name):
                            request.set(domain_attr_name, domain_attr_new_val)
                except StopIteration:
                    print "Done iterating on '%s' node" % request_node_name
        except StopIteration:
            print "Done iterating on '%s' node" % body_node_name
except StopIteration:
    print "Done iterating on '%s' node" % env_node_name

tree.write("output.xml")