AttributeError when assigning value to function for XML data extraction

Question

I'm coding a script to extract information from several XML files with the same structure but with missing sections when there is no information related to a tag. The easiest way to achieve this was using try/except so instead of getting a "AtributeError: 'NoneType' object has no atrribute 'find'" I assign an empty string('') to the object in the exeption. Something like this:

try:
   string1=root.find('value1').find('value2').find('value3').text
except:
   string1=''

The issue is that I want to shrink my code by using a function:

def extract(string):
    tempstr=''
    try:
        tempstr=string.replace("\n", "")
    except:
        if tempstr is None:
            tempstr=""
    return string

And then I try to called it like this:

string1=extract(root.find('value1').find('value2').find('value3').text)

and value2 or value3 does not exist for the xml that is being processed, I get and AttributeError even if I don't use the variable in the function making the function useless.

Is there a way to make a function work, maybe there is a way to make it run without checking if the value entered is invalid?

Solution:

I'm using a mix of both answers:

def extract(root, xpath):
    tempstr=''
    try:
        tempstr=root.findall(xpath)[0].text.replace("\n", "")
    except:
        tempstr=''#To avoid getting a Nonetype object
    return tempstr

Jefferson Houp · Accepted Answer · 2019-12-02 10:14:04Z

1

You can try something like that:

def extract(root, children_keys: list):
    target_object = root
    result_text = ''
    try:
        for child_key in children_keys:
            target_object = target_object.find(child_key)
        result_text = target_object.text
    except:
        pass

    return result_text

You will go deeper at XML structure with for loop (children_keys - is predefined by you list of nested keys of XML - xml-path to your object). And if error will throw inside that code - you will get '' as result.

Example XML (source):

<?xml version="1.0" encoding="UTF-8"?>
<note>
  <to>Tove</to>
  <from>Jani</from>
  <heading>Reminder</heading>
  <body>
    <y>Don't forget me this weekend!</y>
  </body>
</note>

Example:

import xml.etree.ElementTree as ET
tree = ET.parse('note.xml')
root = tree.getroot()
children_keys = ['body', 'y']
result_string = extract(root, children_keys)
print(result_string)

Output:

"Don't forget me this weekend!"

answered Dec 2, 2019 at 10:14

Jefferson Houp

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1 Comment

Walben Over a year ago

Thanks this is a great solution sadly I'm working with hundres of thousands of xml's so I'm avoiding iterations as much as possible. I think that the other solution while incomplete is the best approach. I gave you the right answer because is well presented and easy to understand for beginners like me. At the end I will use the solution on the update of my question.

balderman · Accepted Answer · 2019-12-02 10:16:47Z

1

Use XPATH expression

import xml.etree.ElementTree as ET

xml1 = '''<r><v1><v2><v3>a string</v3></v2></v1></r>'''
root = ET.fromstring(xml1)
v3 = root.findall('./v1/v2/v3')
if v3:
  print(v3[0].text)
else:
  print('v3 not found')


xml2 = '''<r><v1><v3>a string</v3></v1></r>'''
root = ET.fromstring(xml2)
v3 = root.findall('./v1/v2/v3')
if v3:
  print(v3[0].text)
else:
  print('v3 not found')

output

a string
v3 not found

answered Dec 2, 2019 at 10:16

balderman

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