使用xml.dom.minidom更新元素值

Question

我有一个XML结构，长得像这样：

<Store>
   <foo>
      <book>
        <isbn>123456</isbn>
      </book>
      <title>XYZ</title>
      <checkout>no</checkout>
   </foo>

   <bar>
      <book>
        <isbn>7890</isbn>
      </book>
      <title>XYZ2</title>
      <checkout>yes</checkout>
   </bar>
</Store>

我想仅使用xml.dom.minidom（有一些限制）来做以下几件事：

1) 遍历整个XML文件

2) 根据某个元素的父级，查找或获取特定的元素

举个例子：获取作者1的checkout元素，获取作者2的isbn元素

3) 修改或设置那个元素的值

4) 将新的XML结构写入一个文件

有没有人能帮忙呢？

谢谢！

更新：

这是我到目前为止所做的事情

import xml.dom.minidom
checkout = "yes"

def getLoneChild(node, tagname):

  assert ((node is not None) and (tagname is not None))
  elem = node.getElementsByTagName(tagname)
  if ((elem is None) or (len(elem) != 1)):
    return None
  return elem

def getLoneLeaf(node, tagname):

  assert ((node is not None) and (tagname is not None))
  elem = node.getElementsByTagName(tagname)
  if ((elem is None) or (len(elem) != 1)):
    return None
  leaf = elem[0].firstChild
  if (leaf is None):
    return None
  return leaf.data


def setcheckout(node, tagname):

  assert ((node is not None) and (tagname is not None))
  child = getLoneChild(node, 'foo')
  Check = getLoneLeaf(child[0],'checkout')
  Check = tagname
  return Check

doc = xml.dom.minidom.parse('test.xml') 
root = doc.getElementsByTagName('Store')[0]
output = setcheckout(root, checkout)

tmp_config = '/tmp/tmp_config.xml' 
fw = open(tmp_config, 'w')
fw.write(doc.toxml())
fw.close()

Answer 1

我不太明白你说的“checkout”是什么意思。这个脚本会找到某个元素并改变它的值。也许你可以根据自己的需求来调整它。

import xml.dom.minidom as DOM

# find the author as a child of the "Store"
def getAuthor(parent, author):
  # by looking at the children
  for child in [child for child  in parent.childNodes 
                if child.nodeType != DOM.Element.TEXT_NODE]:
    if child.tagName == author:
      return child
  return None

def alterElement(parent, attribute, newValue):
  found = False;
  # look through the child elements, skipping Text_Nodes 
  #(in your example these hold the "values"
  for child in [child for child  in parent.childNodes 
                if child.nodeType != DOM.Element.TEXT_NODE]:

    # if the child element tagName matches target element name
    if child.tagName == attribute:
      # alter the data, i.e. the Text_Node value, 
      # which is the firstChild of the "isbn" element
      child.firstChild.data = newValue
      return True

    else:
      # otherwise look at all the children of this node.
      found = alterElement(child, attribute, newValue)

    if found:
      break 

  # return found status
  return found

doc = DOM.parse("test.xml")
# This assumes that there is only one "Store" in the file
root = doc.getElementsByTagName("Store")[0]

# find the author
# this assumes that there are no duplicate author names in the file
author = getAuthor(root, "foo")
if not author:
  print "Author not found!"
else:
  # alter an element
  if not alterElement(author, "isbn", "987654321"):
    print "isbn not found"
  else:
    # output the xml
    tmp_config = '/tmp/tmp_config.xml'
    f = open(tmp_config, 'w')
    doc.writexml( f )
    f.close()

大致的思路是，你要把作者的名字和“Store”元素下的子元素的标签名进行匹配，然后再深入到作者的子元素中，寻找与目标元素的标签名匹配的内容。这个解决方案中有很多假设，但它可能会帮助你入门。处理像XML这样的层级结构时，不用递归会很麻烦。

---

回想起来，“alterElement”这个函数里有个错误。我已经修复了这个问题（注意“found”这个变量）。