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元素树分析

elementtree xml python

Xeberdee · 技术社区 · 7 年前

我对元素树一无所知,我一直在尝试更改xml文件中的一些文本。我一直在阅读一些示例,但似乎找不到与我试图编辑的示例具有相同类型的xml结构的示例。

我试图访问的特定元素是许多AvClass元素之一,如下所示。。

<AvClass id="MMpr">
  <AvProp id="ASET" name="name" type="string">Untitled</AvProp>
  <AvProp id="ASET" name="kind" type="string">Interplay Folder</AvProp>
  <AvProp id="ASET" name="attributes" type="int16">17</AvProp>
  <AvProp id="ASET" name="type" type="int16">32</AvProp>
  <AvProp id="ASET" name="attrList" type="reference">
    <AvClass id="ATTR">
      <AvProp id="ATTR" name="__OMFI:ATTR:NumItems" type="int32">3</AvProp>
      <List id="OMFI:ATTR:AttrRefs">
        <ListElem>
          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">2</AvProp>
          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_PROJECT_DIRECTORY_NAME</AvProp>
          <AvProp id="ATTR" name="OMFI:ATTB:StringAttribute" type="string">Projects//Post//Grading</AvProp>
        </ListElem>
        <ListElem>
          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>
          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_APPEND_PROJECT</AvProp>
          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">1</AvProp>
        </ListElem>
        <ListElem>
          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>
          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_VERIFY_DIRECTORY</AvProp>
          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">0</AvProp>
        </ListElem>
        <ListElem/>
      </List>
    </AvClass>
  </AvProp>
</AvClass>

编辑:抱歉,我忘了发布代码示例:

tree = ET.parse(this_file) # create tree from file
root = tree.getroot() # set the root     
for x in root.iter('AvClass'): # iterates thru ALL classes    
        for prop in x: # get 1st level properties of class

            # Interplay Paths
            for chi1 in prop: # child of prop
                for chi2 in chi1: # child of child
                    if 'ATS_MM_PROJECT_DIRECTORY_NAME' in str(chi2.text):
                        print(chi2.text)
                        #chi2.text = 'Projects//NEW//STRING//ETC'

我想更改列表中的下一个AvProp元素文本值(可能为空)

1 回复 | 直到 7 年前

Bill Bell 7 年前

Ye olde xpath。

AvProp 使用它的元素。在这段代码中,我验证是否可以看到文本,然后将新文本分配给元素。最后,我展示了xml的完整新版本。

>>> from lxml import etree
>>> tree = etree.parse('this_file.xml')
>>> avprop = tree.xpath('.//AvProp[text()="ATS_MM_PROJECT_DIRECTORY_NAME"]')[0]
>>> avprop.text
'ATS_MM_PROJECT_DIRECTORY_NAME'
>>> avprop.text = 'SOMETHING REALLY NOTICEABLE'
>>> etree.tostring(tree)
b'<AvClass id="MMpr">\n  <AvProp id="ASET" name="name" type="string">Untitled</AvProp>\n  <AvProp id="ASET" name="kind" type="string">Interplay Folder</AvProp>\n  <AvProp id="ASET" name="attributes" type="int16">17</AvProp>\n  <AvProp id="ASET" name="type" type="int16">32</AvProp>\n  <AvProp id="ASET" name="attrList" type="reference">\n    <AvClass id="ATTR">\n      <AvProp id="ATTR" name="__OMFI:ATTR:NumItems" type="int32">3</AvProp>\n      <List id="OMFI:ATTR:AttrRefs">\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">2</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">SOMETHING REALLY NOTICEABLE</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:StringAttribute" type="string">Projects//Post//Grading</AvProp>\n        </ListElem>\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_APPEND_PROJECT</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">1</AvProp>\n        </ListElem>\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_VERIFY_DIRECTORY</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">0</AvProp>\n        </ListElem>\n        <ListElem/>\n      </List>\n    </AvClass>\n  </AvProp>\n</AvClass>'

编辑:虽然输入文件显示同级在特定的顺序中彼此跟随,但在处理xml时不能假定顺序。换句话说,同级可以按任何顺序传递给程序。

这一次,在识别了已知元素后,我得到了它的父元素,然后在它的子元素中寻找一个具有所需元素的元素 name 属性如果没有一个孩子符合这一要求,那么 elements

>>> from lxml import etree
>>> tree = etree.parse('this_file.xml')
>>> elements = tree.xpath('.//AvProp[text()="ATS_MM_PROJECT_DIRECTORY_NAME"]/../*[@name="OMFI:ATTB:StringAttribute"]')
>>> elements[0].text
'Projects//Post//Grading'
>>> if elements:
...     elements[0].text = '*** SOMETING I CAN SEE EASILY ***'
...     
>>> etree.tostring(tree)
b'<AvClass id="MMpr">\n  <AvProp id="ASET" name="name" type="string">Untitled</AvProp>\n  <AvProp id="ASET" name="kind" type="string">Interplay Folder</AvProp>\n  <AvProp id="ASET" name="attributes" type="int16">17</AvProp>\n  <AvProp id="ASET" name="type" type="int16">32</AvProp>\n  <AvProp id="ASET" name="attrList" type="reference">\n    <AvClass id="ATTR">\n      <AvProp id="ATTR" name="__OMFI:ATTR:NumItems" type="int32">3</AvProp>\n      <List id="OMFI:ATTR:AttrRefs">\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">2</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_PROJECT_DIRECTORY_NAME</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:StringAttribute" type="string">*** SOMETING I CAN SEE EASILY ***</AvProp>\n        </ListElem>\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_APPEND_PROJECT</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">1</AvProp>\n        </ListElem>\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_VERIFY_DIRECTORY</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">0</AvProp>\n        </ListElem>\n        <ListElem/>\n      </List>\n    </AvClass>\n  </AvProp>\n</AvClass>'

然后,为了验证代码是否能够处理缺少该元素的xml文件,我“注释”了该元素并重新执行了代码。这次尝试执行 elements[0].text (在生产代码中不会执行的操作)如预期的那样失败,xml保持不变。

>>> tree = etree.parse('this_file.xml')
>>> elements = tree.xpath('.//AvProp[text()="ATS_MM_PROJECT_DIRECTORY_NAME"]/../*[@name="OMFI:ATTB:StringAttribute"]')
>>> elements[0].text
Traceback (most recent call last):
  File "<interactive input>", line 1, in <module>
IndexError: list index out of range
>>> if elements:
...     elements[0].text = '*** SOMETING I CAN SEE EASILY ***'
... 
>>> etree.tostring(tree)
b'<AvClass id="MMpr">\n  <AvProp id="ASET" name="name" type="string">Untitled</AvProp>\n  <AvProp id="ASET" name="kind" type="string">Interplay Folder</AvProp>\n  <AvProp id="ASET" name="attributes" type="int16">17</AvProp>\n  <AvProp id="ASET" name="type" type="int16">32</AvProp>\n  <AvProp id="ASET" name="attrList" type="reference">\n    <AvClass id="ATTR">\n      <AvProp id="ATTR" name="__OMFI:ATTR:NumItems" type="int32">3</AvProp>\n      <List id="OMFI:ATTR:AttrRefs">\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">2</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_PROJECT_DIRECTORY_NAME</AvProp>\n          <!-- AvProp id="ATTR" name="OMFI:ATTB:StringAttribute" type="string">Projects//Post//Grading</AvProp -->\n        </ListElem>\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_APPEND_PROJECT</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">1</AvProp>\n        </ListElem>\n        <ListElem>\n          <AvProp id="ATTR" name="OMFI:ATTB:Kind" type="int32">1</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:Name" type="string">ATS_MM_VERIFY_DIRECTORY</AvProp>\n          <AvProp id="ATTR" name="OMFI:ATTB:IntAttribute" type="int32">0</AvProp>\n        </ListElem>\n        <ListElem/>\n      </List>\n    </AvClass>\n  </AvProp>\n</AvClass>'