XML: How to get Elements by Attribute Value - Python 2.7 and minidom

Question

I want to get a list of XML Elements based first on TagName and second on Attribute Value. I´m using the xml.dom library and python 2.7.

While it´s easy to get the first step done:

from xml.dom import minidom
xmldoc = minidom.parse(r"C:\File.xml")
PFD = xmldoc.getElementsByTagName("PFD")
PNT = PFD.getElementsByTagName("PNT")

I´ve been looking around but cannot find a solution for the second step. Is there something like a .getElementsByAttributeValue that would give me a list to work with?

If the XML looks like this

<PFD>
     <PNT A="1" B=.../>
     <PNT A="1" B=.../>
     <PNT A="2" B=.../>
</PFD>

In need all PNTs where A="1" in a list.

Solution 1

If you don't find a built-in method, why not iterate over the items?

from xml.dom import minidom
xmldoc = minidom.parse(r"C:\File.xml")
PFD = xmldoc.getElementsByTagName("PFD")
PNT = xmldoc.getElementsByTagName("PNT")
for element in PNT:
    if element.getAttribute('A') == "1":
        print "element found"

Adding the items to a list should be easy now.

Solution 2

If you aren't limited to using xml.dom.minidom, lxml has better search functionality. Note that lxml is not builtin, and will require installing the lxml package and non-Python dependencies.

Eg:

>>> from lxml import etree
>>> root = etree.parse(r"C:\File.xml")
>>> for e in root.findall('PNT[@A="1"]'):
...     print etree.tostring(e)
<PNT A="1" B="c"/>
<PNT A="1" B="b"/>

Lxml also supports all of XPath via element.xpath('query'). Other convenience functions include element.findtext which finds the appropriate element and returns the text of it, element.find and element.findall which returns the first/list of all elements matching a query using a subset of XPath covering common queries.

Solution 3

Try this:

from xml.dom import minidom

xmldoc = minidom.parse(r"C:\File.xml")
PNT = xmldoc.getElementsByTagName("PNT")

for element in PNT:
    print element.attributes.keys()
    for elem in element.attributes.values():
        print elem.firstChild.data