minidom appendChild confusion

[Marco]

Hello!

Can anyone explain why the following code does not work?
(I'm using python2.4.)


Cheers, Marco

--

# the following code does _not_ work.
# intended: put child-nodes as children to another node

from xml.dom.minidom import Document
doc = Document()
node1 = doc.createEleme nt('one')
el1 = doc.createEleme nt('e1')
el2 = doc.createEleme nt('e1')
node1.appendChi ld(el1)
node1.appendChi ld(el2)
assert 2 == len(node1.child Nodes) # ok

doc2 = Document()
node2 = doc2.createElem ent('two')

for el in node1.childNode s:
node2.appendChi ld(el)

assert 2 == len(node2.child Nodes), "node2 has an unexpected number of
children"

[Peter Otten]

Re: minidom appendChild confusion

Marco wrote:
[color=blue]
> Can anyone explain why the following code does not work?
> (I'm using python2.4.)[/color]
[color=blue]
> # the following code does _not_ work.
> # intended: put child-nodes as children to another node
>
> from xml.dom.minidom import Document
> doc = Document()
> node1 = doc.createEleme nt('one')
> el1 = doc.createEleme nt('e1')
> el2 = doc.createEleme nt('e1')
> node1.appendChi ld(el1)
> node1.appendChi ld(el2)
> assert 2 == len(node1.child Nodes) # ok
>
> doc2 = Document()
> node2 = doc2.createElem ent('two')
>
> for el in node1.childNode s:
> node2.appendChi ld(el)[/color]

A node added to node2's children is implicitly removed from node1's
children. So you are iterating over the node1.childNode s list while
altering it, which typically results in skipping every other item:
[color=blue][color=green][color=darkred]
>>> a = list("abcde")
>>> for i in a:[/color][/color][/color]
.... a.remove(i)
....[color=blue][color=green][color=darkred]
>>> a[/color][/color][/color]
['b', 'd']

You can avoid that by making a copy of node1.childNode s:

for el in list(node1.chil dNodes):
node2.appendChi ld(el)

[color=blue]
> assert 2 == len(node2.child Nodes), "node2 has an unexpected number of
> children"[/color]

Peter

[Marco]

Re: minidom appendChild confusion

That's it. Thank you very much!

Marco