Find element with attribute with minidom

Question

Given

Answer 1

I don't think you can.

From the parent element, you need to

for subelement in element.GetElementsByTagName("field"):
    if subelement.hasAttribute("frame.len"):
        do_something()

Reacting to your comment from March 11, if the structure of your documents is stable and free of nasty surprises (like angle brackets inside attributes), you might want to try the unthinkable and use a regular expression. This is not recommended practice but could work and be much easier than actually parsing the file. I admit that I've done that sometimes myself. Haven't gone blind yet.

So in your case you could (assuming that a <field> tag doesn't span multiple lines):

xmlfile = open("myfile.xml")
for line in xmlfile:
    match = re.search(r'<field\s+name="frame.len"\s+([^>]+)/>', line):
    if match:
        result = match.group(1)
        do_something(result)

If a <field> tag can span multiple lines, you could try loading the entire file as plain text into memory and then scan it for matches:

filedump = open("myfile.xml").read()
for match in re.finditer(r'<field\s+name="frame.len"\s+([^>]+)/>', filedump):
    result = match.group(1)
    do_something(result)

In both cases, result will contain the attributes other than frame.len. The regex assumes that frame.len is always the first attribute inside the tag.

Answer 2

Wow, that regex is horrible! As of 2016, there is a .getAttribute() method for each DOMElement that makes things a bit easier, but you still have to iterate through the elements.

l = []
for e in elements:
    if e.hasAttribute('name') and e.getAttribute('name') == 'field.len':
        l.append(e)

Answer 3

You don't -- the DOM API, somewhat poorly designed (by w3c, not by Python!-) doesn't have such a search function to do the iteration for you. Either accept the need to loop (not through every tag in general, but through all with a given tag name), or upgrade to a richer interface, such as BeautifulSoup or lxml.