为什么xml包在Python3中修改我的xml文件? [英] Why does xml package modify my xml file in Python3?
问题描述
我使用Python3.5 中的xml 库读取 和写入 xml 文件.我不修改文件.只需打开并写入.但是库会修改文件.
I use the xml library in Python3.5 for reading and writing an xml-file. I don't modify the file. Just open and write. But the library modifes the file.
- 为什么要修改?
- 如何防止这种情况发生?例如我只是想在一个相当复杂的 xml 文件中替换特定标签或它的值，而不会丢失任何其他信息.
这是示例文件
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<movie>
<title>Der Eisbär</title>
<ids>
<entry>
<key>tmdb</key>
<value xsi:type="xs:int" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">9321</value>
</entry>
<entry>
<key>imdb</key>
<value xsi:type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">tt0167132</value>
</entry>
</ids>
</movie>
这是代码
import xml.etree.ElementTree as ET
tree = ET.parse('x.nfo')
tree.write('y.nfo', encoding='utf-8')
xml文件变成了这个
<movie xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<title>Der Eisbär</title>
<ids>
<entry>
<key>tmdb</key>
<value xsi:type="xs:int">9321</value>
</entry>
<entry>
<key>imdb</key>
<value xsi:type="xs:string">tt0167132</value>
</entry>
</ids>
</movie>
- 第 1 行不见了.
- 第 2 行中的
<movie>-标签现在有了属性. - 第 7 行和第 11 行中的
<value>-标签现在具有更少的属性. - Line 1 is gone.
- The
<movie>-tag in line 2 has attributes now. - The
<value>-tag in line 7 and 11 now has less attributes.
推荐答案
请注意，xml 包"和xml 库"是不明确的.标准库中有几个与 XML 相关的模块:https://docs.python.org/3/library/xml.html.
Note that "xml package" and "the xml library" are ambiguous. There are several XML-related modules in the standard library: https://docs.python.org/3/library/xml.html.
为什么要修改?
ElementTree 将命名空间声明移动到根元素，并删除文档中实际未使用的命名空间.
ElementTree moves namespace declarations to the root element, and namespaces that aren't actually used in the document are removed.
为什么 ElementTree 会这样做?我不知道，但也许这是一种使实现更简单的方法.
Why does ElementTree do this? I don't know, but perhaps it is a way to make the implementation simpler.
如何防止这种情况发生?例如我只想在一个相当复杂的 xml 文件中替换特定的标签或它的值，而不会丢失任何其他信息.
How can I prevent this? e.g. I just want to replace specific tag or it's value in a quite complex xml-file without loosing any other informations.
我认为没有办法防止这种情况发生.这个问题之前已经提过了.以下是两个非常相似但没有答案的问题:
I don't think there is a way to prevent this. The issue has been brought up before. Here are two very similar questions with no answers:
我的建议是使用 lxml 而不是 ElementTree.使用 lxml，命名空间声明将保留在它们在原始文件中出现的位置.
My suggestion is to use lxml instead of ElementTree. With lxml, the namespace declarations will remain where they occur in the original file.
第 1 行不见了.
那一行是 XML 声明.建议但不是必须拥有一个.
That line is the XML declaration. It is recommended but not mandatory to have one.
如果您总是需要 XML 声明，请在 write() 方法调用中使用 xml_declaration=True.
If you always want an XML declaration, use xml_declaration=True in the write() method call.
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