is it bug or feature in xml.dom.minidom?

Paul Boddie paul at boddie.org.uk
Fri Mar 2 21:28:13 CET 2007


Maksim Kasimov wrote:
> Hi, i'm faced with such a problem when i use xml.dom.minidom:
>
> to append all child nodes from "doc" in "_requ" to "doc" in "_resp", i do the following:
>
> _requ = minidom.parseString("<resp><doc><one>One</one><two>Two</two></doc></resp>")
> _resp = minidom.parseString("<resp><doc/></resp>")

Note that these are different documents - this is important later on.

> iSourseTag = _requ.getElementsByTagName('doc')[0]
> iTargetTag = _resp.getElementsByTagName('doc')[0]
>
>
> # it prints me that there are two child nodes
> for iChild in iSourseTag.childNodes:
>  print iChild.toxml()

Seems alright.

> # when i walk elements, only first iteration was made
> # and iSourseTag.childNodes now have only one element instead of two
> for iChild in iSourseTag.childNodes:
>  iTargetTag.appendChild(iChild)

But since you're taking a node from one document to add it to another,
you should instead use importNode to make that node importable into
the target document:

for iChild in iSourseTag.childNodes:
    # 1 or True should cause a deep copy
    iNewChild = _resp.importNode(iChild, 1)
    iTargetTag.appendChild(iNewChild)

> # it prints me that there is only one child node
> for iChild in iSourseTag.childNodes:
>  print iChild.toxml()

That's probably because you've "stolen" the node from its document in
order to add it to the target document - something which is possibly
an artifact of the minidom implementation.

> i'm not sure, whether i append child nodes in properly way, but IMHO it looks like a bug.

That minidom does not refuse to let you "move" nodes in this way could
be debated as being a bug or not, but the correct way of copying nodes
is to use importNode.

> My question is how to avoid the "iSourseTag" changes while iterate its nodes?
>
> And, of course, how to append all child nodes to "iTargetTag"?

These questions are hopefully answered above.

Paul




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