How do I create a new Node using pulldom?

[susan_ali]

I'm using xml.dom.pulldom to parse through an XML file. I use
expandNode() to scrutinize certain blocks of it that I'm interested
in.


Once I find a block of XML in the input file that I'm interested in, I
need to add my own block <MyTag>.....</MyTag> to the pulldom tree I'm
building in memory.

The documentation on PullDom is worse than atrocious. It is simply non-
existant. I can't even find a simple explanation of what the functions
are named and what arguments they take. Sheesh.


When I have a node N of the tree, I think that I can use
N.appendChild() to do what I want (just guessing from the function
name which I can see).

appendChild takes 1 argument -- a new node.

But I don't know how to create such a node.
Can someone out there please post a code fragment showing how to
create a pulldom node? The simpler and more commented it is the
better.

THANKS!!!
- Saqib

 

[Paul Boddie]

I'm using xml.dom.pulldom to parse through an XML file. I use
expandNode() to scrutinize certain blocks of it that I'm interested
in.

Right. This is the thing which differentiates pulldom from traditional
DOM implementations, which I'll discuss below.

Once I find a block of XML in the input file that I'm interested in, I
need to add my own block <MyTag>.....</MyTag> to the pulldom tree I'm
building in memory.
Understood.

The documentation on PullDom is worse than atrocious. It is simply non-
existant. I can't even find a simple explanation of what the functions
are named and what arguments they take. Sheesh.

Sheesh, indeed. I think the authors assumed a familiarity with the DOM
APIs, but they're regarded as being somewhat "old school" by many
these days, so it's possible that you aren't too familiar with the
PyXML/DOM style of the API employed.

When I have a node N of the tree, I think that I can use
N.appendChild() to do what I want (just guessing from the function
name which I can see).

appendChild takes 1 argument -- a new node.

Correct. I think that you also need to have expanded the part of the
document where the node will be placed. For example:

stream = xml.dom.pulldom.parseString(s)
for event, node in stream:

But I don't know how to create such a node.

This is a traditional DOM activity, but it's easy to be disoriented if
you don't already have a document object (which has the necessary
methods). However, such an object is readily available:

doc = node.ownerDocument

You can then create a node using the usual create* methods. For
example:

element = doc.createElement("new")

And then you can use appendChild on the original node:

node.appendChild(element)

Note that since the document under node has been expanded, subsequent
nodes pulled from the stream will start with an END_ELEMENT event
involving the node concerned.

Can someone out there please post a code fragment showing how to
create a pulldom node? The simpler and more commented it is the
better.

Try this:

import xml.dom.pulldom
s = "<test><node>xxx</node></test>"

# Start parsing.
stream = xml.dom.pulldom.parseString(s)

# Process each event.
for event, node in stream:

# Do the addition of an element within "node".
if event == xml.dom.pulldom.START_ELEMENT and \
node.localName == "node":

# Have to expand first.
stream.expandNode(node)

# Get the document and create the element.
doc = node.ownerDocument
element = doc.createElement("new")

# Add the element; see what we've produced.
node.appendChild(element)
print node.toxml()

Hope this helps!

Paul