Detailed explanation of python xml parsing examples

python xml parsing

first.xml

<info> 
<person > 
<id>1</id> 
<name>fsy</name> 
<age >24</age> 
</person> 
<person> 
<id>2</id> 
<name>jianjian</name> 
<age>24</age> 
</person> 
<count id ='1'>1000</count> 
</info>

from xml.etree import ElementTree as etree

Read in

def read_xml(file): 
# parse()函数会返回一个能代表整篇文档的对象。这不是根元素。要获得根元素的引用可以调用getroot()方法。 
tree = etree.parse(file) 
root = tree.getroot() 
return root

Get information

def print_node(node): 
'''''打印结点基本信息''' 
print("node.tag:%s" % node.tag) 
print("node.attrib:%s"%node.attrib) 
print( "node.text:%s" % node.text)

Search:

find_all 
>>> root = read_xml ('first.xml')   
>>> res = root.findall("person") 
[<Element 'person' at 0x00000000033388B8>, <Element 'person' at 0x0000000003413D68>] 
   
注意：findall只查询直接的子节点 
>>> r1 = root.findall("id") 
>>> r1 
[] 
>>> r =tree.findall(".//id") 
>>> for e in r: 
  print( e,e.text) 
      
<Element 'id' at 0x00000000034279F8> 1 
<Element 'id' at 0x0000000003427B38> 2

find:

#find()方法用来返回第一个匹配到的元素。当我们认为只会有一个匹配，或者有多个匹配但我们只关心第一个的时候，这个方法是很有用的。 
>>> res[0].find("id") 
<Element 'id' at 0x0000000003413CC8> 
>>> print_node(res[0].find("id")) 
node.tag:id 
node.attrib:{} 
node.text:1

find find Failure:

When using find, please note that in a Boolean context, if the ElementTree element object does not contain child elements, its value will be considered False (that is, if len(element) is equal to 0). This means if element.find('...') is not testing whether the find() method found a match; this statement is testing whether the matched element contains child elements. If you want to test whether the find() method returns an element, you need to use if element.find('...') is not None.

>>> bk = res[0].find("no") 
>>> bk 
>>> type(bk) 
<class 'NoneType'> 
>>> res[0].find("id") 
<Element 'id' at 0x0000000003413CC8> 
>>> if res[0].find("id"): 
    print("find") 
  else: 
    print("not find") 
not find 
>>> if res[0].find("id") is not None: 
    print("find") 
  else: 
    print("not find") 
find

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