How do i get the text from a xml.dom.minidom Dom Element?

Question

How do I get the text value of the title element? Is this even possible with a Dom Element? Will I have to parse out the text by hand?

#-*-coding:utf8;-*-
#qpy:3
#qpy:console

import re
import urllib.request
from xml.dom import minidom

def download(url):
    with urllib.request.urlopen(url) as res:
        return res.read().decode('latin-1')

class RSSFeed(object):
    def __init__(self, url):
        self.url = url
        self.raw_xml = download(url)
        self.dom = minidom.parseString(self.raw_xml)
        self.links = self.dom.getElementsByTagName('link')

    def entries(self):
        ret = {}
        for element in self.dom.getElementsByTagName('entry'):
            title = element.getElementsByTagName('title')[0]
            print(title.toprettyxml())


    def __str__(self):
        return self.dom.toprettyxml()

feed_url = 'https://rickys-python-notes.blogspot.com/atom.xml?redirect=false&start-index=1&max-results=500'
feed = RSSFeed(feed_url)
dom = feed.dom
print(feedHow totries())

Answer 1

#-*-coding:utf8;-*-
#qpy:3
#qpy:console

import urllib.request
from xml.dom import minidom


def parse_feed(url):
    with urllib.request.urlopen(url) as res:
        dom = minidom.parseString(res.read().decode('latin-1'))
    for element in dom.getElementsByTagName('entry'):
        title = element.getElementsByTagName('title')[0].firstChild.nodeValue
        link = element.getElementsByTagName('link')[0].getAttribute('href')
        author = element.getElementsByTagName('name')[0].firstChild.nodeValue
        article = element.getElementsByTagName('content')[0].firstChild.nodeValue
        yield type('Entry', (object,), dict(title=title, link=link, author=author, article=article))


feed_url = 'https://rickys-python-notes.blogspot.com/atom.xml?redirect=false&start-index=1&max-results=500'

for entry in parse_feed(feed_url):
    print(entry.title, entry.link)

Answer 2

The canonical way to determine the node value (i.e. text content) of any XML element is to

• get the node value of all the text nodes it contains, including the nested ones
• trim them
• join them with a space

Minidom inexplicably does not implement this procedure, so if you must use minidom, you need to do it yourself.

So we need a few helper functions.

• One to get all the descendant nodes that fulfill a certain condition, like being a text node.
• One to get their values and join them
• One that gets the first element of a certain name from a node, for convenience.

Let's collect them in a module.

# minidom_helpers.py

def get_descendant_nodes(context_node, predicate):
    if not context_node:
        yield None
    for child in context_node.childNodes:
        if predicate(child):
            yield child
        yield from get_descendant_nodes(child, predicate)

def get_text_value(context_node, default=None):
    texts_nodes = get_descendant_nodes(context_node, lambda n: n.nodeType == n.TEXT_NODE)
    text_value = ' '.join([str.strip(t.nodeValue) for t in texts_nodes])
    return text_value if text_value else default

def get_first_child(context_node, element_name):
    elems = context_node.getElementsByTagName(element_name)
    return elems[0] if elems else None

Now we can do

import re
import urllib.request
from xml.dom import minidom
from minidom_helpers import *

class RSSFeed(object):
    def __init__(self, url):
        self.url = url
        self.dom = minidom.parse(urllib.request.urlopen(url))
        self.links = self.dom.getElementsByTagName('link')

    def entries(self):
        for entry in self.dom.getElementsByTagName('entry'):
            yield {
                "title":  get_text_value(get_first_child(entry, 'title'))
            }

    def __str__(self):
        return self.dom.toprettyxml()

feed_url = 'https://rickys-python-notes.blogspot.com/atom.xml?redirect=false&start-index=1&max-results=500'
feed = RSSFeed(feed_url)

for entry in feed.entries():
    print(entry)

---

A general note on parsing XML. Try to get into the habit of thinking of XML as binary data, instead of text.

XML parsers implement a complex mechanism of figuring out the file encoding automatically. It's not necessary and not smart to circumvent that mechanism by trying to decode the file or HTTP response into a string yourself ahead of time:

# BAD CODE, DO NOT USE
def download(url):
    with urllib.request.urlopen(url) as res:
        return res.read().decode('latin-1')

raw_xml = download(url)
dom = minidom.parseString(self.raw_xml)

The above makes hard-coded (and in your case: wrong) assumptions about the file encoding and will break when the server decides to start sending the file in UTF-16 for some reason.

If you think of XML as binary data instead of text, it gets both a lot easier and a lot more robust.

dom = minidom.parse(urllib.request.urlopen(url))

The XML parser will sniff the bytes and decide what encoding they are in.

This is also true for reading XML from files. Instead of

# BAD CODE, DO NOT USE
with open(path, 'r', encoding='latin-1') as fp:
    dom = minidom.parseString(fp.read())

Use

with open(path, 'rb') as fp:
    dom = minidom.parse(fp)

or simply

dom = minidom.parse(path)

Answer 3

def entries(self):
        for element in self.dom.getElementsByTagName('entry'):
            title = element.getElementsByTagName('title')[0].firstChild.nodeValue
            link = element.getElementsByTagName('link')[0].getAttribute('href')
            author = element.getElementsByTagName('name')[0].firstChild.nodeValue
            article = element.getElementsByTagName('content')[0].firstChild
            yield type('Entry', (object,), dict(title=title, link=link, author=author, article=article))