【python】lxml中多个xml采用相同节点时出现的问题

今天突然发现了一个lxml的坑。

假设我们有一个节点

<id>123</id>

有两个父节点都要用上述节点，则必须把上面的节点写两遍！用同一个会出错！

出错例子：

#!/usr/bin/env python
#encoding:utf8

from lxml import etree

if __name__ == "__main__":
    
    root1 = etree.Element("root1")  #根节点1
    root2 = etree.Element("root2")  #根节点2
    ver_node = etree.Element("id")  #子节点
    ver_node.text = "123"
    
    root1.append(ver_node)  #都加入了同一个子节点
    root2.append(ver_node)
    
    print etree.tostring(root1, pretty_print=True, xml_declaration=True, encoding='UTF-8')
    print etree.tostring(root2, pretty_print=True, xml_declaration=True, encoding='UTF-8')

结果：

<?xml version='1.0' encoding='UTF-8'?>
<root1/>

<?xml version='1.0' encoding='UTF-8'?>
<root2>
  <id>123</id>
</root2>

只有后面一个有子节点，前面一个没有！

正确写法：

#!/usr/bin/env python
#encoding:utf8
from lxml import etreeimport copy

if __name__ == "__main__":
    root1 = etree.Element("root1")
    root2 = etree.Element("root2")
    ver_node1 = etree.Element("id")
    ver_node1.text = "123"
    ver_node2 = copy.deepcopy(ver_node1) #深拷贝！
    
    root1.append(ver_node1)
    root2.append(ver_node2)
    
    print etree.tostring(root1, pretty_print=True, xml_declaration=True, encoding='UTF-8')
    print etree.tostring(root2, pretty_print=True, xml_declaration=True, encoding='UTF-8')

结果：

<?xml version='1.0' encoding='UTF-8'?>
<root1>
  <id>123</id>
</root1>

<?xml version='1.0' encoding='UTF-8'?>
<root2>
  <id>123</id>
</root2>