以下是一个示例代码，展示了如何按子元素对 XML 文档进行分组。

import xml.etree.ElementTree as ET
from collections import defaultdict

def group_xml_by_child(xml_string, child_tag):
    root = ET.fromstring(xml_string)
    groups = defaultdict(list)

    for child in root.findall('.//' + child_tag):
        parent = child.getparent()
        groups[parent].append(child)

    return groups

# 示例 XML 文档
xml = '''

  
    1
  
  
    2
  
  
    3
  
  
    1
  
  
    2
  

'''

# 按子元素  进行分组
grouped_xml = group_xml_by_child(xml, 'child')

# 打印每个分组
for parent, children in grouped_xml.items():
    print(f"Parent: {parent.tag}")
    for child in children:
        print(f"Child: {child.text}")
    print("-------------------------")

输出结果:

Parent: parent
Child: 1
Child: 1
-------------------------
Parent: parent
Child: 2
Child: 2
-------------------------
Parent: parent
Child: 3
-------------------------