使用来自 xml.dom.minidom 的 getElementsByTagName

Question

I'm going through Asheesh Laroia's "Scrape the Web" presentation from PyCon 2010 and I have a question about a particular line of code which is this line:

title_element = parsed.getElementsByTagName('title')[0]

from the function:

def main(filename):
    #Parse the file
    parsed = xml.dom.minidom.parse(open(filename))
    # Get title element
    title_element = parsed.getElementsByTagName('title')[0]
    # Print just the text underneath it
    print title_element.firstChild.wholeText

I don't know what role '[0]' is performing at the end of that line. Does 'xml.dom.minidom.parse' parse the input into a list?

Answer 1

parse() does not return a list; getElementsByTagName() does. You're asking for all elements with a tag of <title> . Most tags can appear multiple times in a document, so when you ask for those elements, you'll get more than one. The obvious way to return them is as a list or tuple.

In this case you expect only one <title> tag in the document, so you just take the first element in the list.

Answer 2

This method's ( getElementsByTagName ) documentation says:

Search for all descendants (direct children, children's children, etc.) with a particular element type name.

Since it mentions " all descendants", then yes, in all likeness it returns a list that this code just indexes to see the first element.

Looking at the code of this method (in Lib/xml/dom/minidom.py ) - it indeed returns a list.