Adding row to xml using lxml

Question

I have a method which saves from reservations, but overwrites the output file every time when I create a new instance of XmlReportGenerator

from lxml import etree
from Flights.FlightTravelReservation import FlightTravelReservation

class XmlReportGenerator:
    root = None
    doc = None

    def __init__(self):
        self.root = etree.Element('results')
        self.doc = etree.ElementTree(self.root)

    def add_flight_row(self, flight_travel_reservation):
        page_element = etree.SubElement(self.root, 'FlightTravel')
        etree.SubElement(page_element, 'QuantityOfPassengers').text = 
             str(len(flight_travel_reservation.paxes))
        etree.SubElement(page_element,'Id').text = 
             flight_travel_reservation.reservation_id

    def Save(self, path = 'Flights.xml'):
        outFile = open(path, 'wb')
        self.doc.write(outFile)

Where sample output is:

<results>
  <FlightTravel>
    <Paxes>4</Paxes>
    <Id>259183</Id>
  </FlightTravel>
</results>

How do I modify add_flight_row method to add new rows? For example, I want something like:

<results>
  <FlightTravel>
    <Paxes>4</Paxes>
    <Id>259183</Id>
  </FlightTravel>
  <FlightTravel>
    <Paxes>9</Paxes>
    <Id>123456</Id>
  </FlightTravel>
</results>

I added test method:

def test_test(self,a,b):

    page_element = etree.SubElement(self.root,'FlightTravel')

    etree.SubElement(page_element,'QuantityOfPassengers').text = a
    etree.SubElement(page_element,'Id').text = b

    return page_element

And this is how I use it:

x=XmlReportGenerator()
x.test_test("a","b")
x.Save("test.xml")

x=XmlReportGenerator()
x.test_test("c","d")
x.Save("test.xml")

and in result I have:

<results>
  <FlightTravel>
    <Flights/>
    <QuantityOfPassengers>c</QuantityOfPassengers>
    <Id>d</Id>
  </FlightTravel>
</results>

instead of

<results>
  <FlightTravel>
    <Flights/>
    <QuantityOfPassengers>a</QuantityOfPassengers>
    <Id>b</Id>
  </FlightTravel>
  <FlightTravel>
    <Flights/>
    <QuantityOfPassengers>c</QuantityOfPassengers>
    <Id>d</Id>
  </FlightTravel>
</results>

No, I can open it using IE so it's ok. There is a node flighs, but don't look at it. Now it is not important :) — user278618
– user278618, Commented May 30, 2011 at 10:11
Since you don't show code that calls add_flight_row I guess that you are Saveing every results tree for each element of flight_travel_reservation or are not looping at all. The code doesn't match the output, either, so please paste the actual code and output. — msw
– msw, Commented May 30, 2011 at 11:07
+1 thanks for clarifying the question. Every XML document has one and only one root. Therefore, if Save must generate a well-formed document it cannot simply concatenate today's <results></results> onto yesterday's. Thus phihag's answer. — msw
– msw, Commented May 31, 2011 at 11:51

phihag · Accepted Answer · 2011-05-30 16:41:59Z

2

You'll need to define a Load function for XmlReportGenerator to load the old results.

class XmlReportGenerator(object):
    def __init__(self):
    # __init__, add_flight_row, and Save

    def load(self, path='Flights.xml'):
        try:
            self.doc = etree.ElementTree()
            self.root = self.doc.parse(path)
        except IOError:
            pass

and use it like this:

# day 1
x=XmlReportGenerator()
x.load('test.xml') # Silently catches the error if the file does not exit yet
x.test_test("a","b")
x.Save('test.xml')

# day2
x=XmlReportGenerator()
x.load('test.xml')
x.test_test("c","d")
x.Save("test.xml")

edited May 30, 2011 at 16:41

answered May 30, 2011 at 12:11

phihag

289k75 gold badges475 silver badges489 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user278618 Over a year ago

So I can't? I will be running this code everyday, so there is no chance to use the same instance of XmlReportGenerator

phihag Over a year ago

@user278618 I'm sorry, I didn't realize you wanted to append cd to the ab file, not just create the file with abcd.

Jan Hudec · Accepted Answer · 2011-05-30 12:09:48Z

0

Just call add_flight_row (or test_test) repeatedly on the same instance for each row you want to add:

x = XmlReportGenerator()
x.test_test("a", "b")
x.test_test("c", "d")
x.Save("test.xml")

answered May 30, 2011 at 12:09

Jan Hudec

76.8k13 gold badges138 silver badges190 bronze badges

1 Comment

user278618 Over a year ago

So I can't? I will be running this code everyday, so there is no chance to use the same instance of XmlReportGenerator

Collectives™ on Stack Overflow

Adding row to xml using lxml

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related