Python - How can I return a list for each xml node I am iterating through using xml.etree.ElementTree?

Question

I am using the xml.etree.ElementTree module to parse an XML file, returning the attributes into lists, and then entering those lists in a MySQL database (this last step I am not worried about so there is no need to cover it here). Simple enough, and I am currently able to do so but only for one child node at a time. The goal is to do so with multiple child nodes, regardless of how many there are. Here is a sample file:

<?xml version="1.0"?>
    <catalog>
       <book id="bk101" type="hardcover">
          <info author="Gambardella, Matthew" title="XML Developer's Guide" genre="Computer" price="44.95" publish_date="2000-10-01" description="An in-depth look at creating applications 
          with XML." />
       </book>
       <book id="bk102" type="softcover">
          <info author="Ralls, Kim" title="Midnight Rain" genre="Fantasy" price="5.95" publish_date="2000-10-01" description="A former architect battles corporate zombies, 
          an evil sorceress, and her own childhood to become queen 
          of the world." />
       </book>
       <book id="bk101" type="softcover">
          <info author="Corets, Eva" title="Maeve Ascendant" genre="Fantasy" price="5.95" publish_date="2000-11-17" description="After the collapse of a nanotechnology 
          society in England, the young survivors lay the 
          foundation for a new society." />
       </book>
    </catalog>

I am able to parse the correct attributes for the first book node where id="bk101" or the last book node where id="bk103" by returning a list with the correct attributes. However, I am only returning one list per file when I need to return multiple lists (one for each book node and info node, so in this case 6 total lists).

Here is my code:

import xml.etree.ElementTree

book_attribute = ['id', 'type']
info_attribute = ['author', 'title', 'genre', 'price', 'publish_date', 'description']


class ApplicationClass(object):  # define the only class in this file
    def __init__(self):
        self.ET = xml.etree.ElementTree.parse('file.xml').getroot()
        self.bookNodes = self.ET.findall('book')
        self.book_values_list = []
        self.info_values_list = []

    def get_book(self):
        for bookNode in self.bookNodes:
            self.book_values_list = [bookNode.get(i) for i in book_attribute]
        return self.book_values_list

    def get_info(self):
        for bookNode in self.bookNodes:
            for infoNode in bookNode.findall('info'):
                self.info_values_list = [infoNode.get(i) for i in info_attribute]
        return self.info_values_list

a = ApplicationClass()
a.get_book()
print(a.book_values_list)
a.get_info()
print(a.info_values_list)

So I know my problem is that I am only returning one list per function because I am returning the list at the end of the function and then calling the function at the end of my script. I just can't find the proper way to achieve my desired outcome. If I don't run my functions at the end of the script, then how can I return the multiple lists that I am looking for?

ArtOfWarfare · Accepted Answer · 2015-11-19 18:36:51Z

3

This line is your problem:

self.book_values_list = [bookNode.get(i) for i in book_attribute]

That line will replace your existing list with a new list. But you have this line inside a loop, which means on each pass through the loop, you lose what was previously processed.

I think you want this instead:

self.book_values_list.append([bookNode.get(i) for i in book_attribute])

Using .append() instead of = will make it so that your variable will have more stuff inserted into it. Ultimately you'll end up with a list of lists, like this:

[['bk101', 'hardcover'], ['bk102', 'softcover'], ['bk101', 'softcover']]

Your other method/loop has the same problem in it - you assign a new list to the variable instead of inserting a new list into the existing list.

answered Nov 19, 2015 at 18:36

ArtOfWarfare

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