[lxml-dev] c14n, pretty printing and diffing

[Olivier Collioud]

For those interested by the iterparse method, the following is much
better:

            sourceTree = ElementTree.iterparse(open(inputDir+'/'+file,
'r'), events=("start", "end"))
            for event, elem in sourceTree:
                    
                if event == "start":
                    i = "\n" + depth*"  "
                    depth += 1
                    outputFile.write('%s<%s' % (i,elem.tag))
                    if len(elem.items()):
                        attrs = elem.items()
                        attrs.sort()
                        outputFile.write(' ')
                        outputFile.write(' '.join(['%s="%s"' %
(a[0],a[1]) for a in attrs if a[0] != 'size']))
                    outputFile.write('>')
                    if elem.text and elem.text.strip():
                       
outputFile.write(elem.text.strip('\n').encode('utf-8'))
                    
                if event == "end":
                    outputFile.write('%s</%s>' % (i,elem.tag))
                    if elem.tail and elem.tail.strip():
                       
outputFile.write(elem.tail.strip('\n').encode('utf-8'))
                    depth -= 1
                    elem.clear()

because when event == 'start' then len(elem) is always 0,
and I don't how to guess if the element will have some content in order
to produce en empty tag (or not).
Therefore,the above code always produce an element end tag even when
there is no content.

>>> "Olivier Collioud" <Olivier.Collioud at wipo.int> 12/02/08 7:26 am
>>>
Thanks Stephan.

I prefer visual diffing : the ones provided by Eclipse, TkDiff or
WinMerge.

I did not fin any doc or usage example of lxml.usedoctest,
could you please give some pointer ?

Let me share my simple (because I do not use any namespace, PI,
comment...)
solution based on iterparse:

    depth = 0
    sourceTree = ElementTree.iterparse(open(inputFile, 'r'),
events=("start", "end"))
    for event, elem in sourceTree:
            
        if event == "start":
            i = "\n" + depth*"  "
            depth += 1
            outputFile.write('%s<%s' % (i,elem.tag))
            if len(elem.items()):
                attrs = elem.items()
                attrs.sort()
                outputFile.write(' ')
                outputFile.write(' '.join(['%s="%s"' % (a[0],a[1]) for
a in attrs if a[0] != 'size']))
            if elem.text and elem.text.strip():
                outputFile.write('>%s' %
elem.text.strip('\n').encode('utf-8'))
            elif len(elem):
                outputFile.write('>')
            
        if event == "end":
            if (elem.text and elem.text.strip()) or len(elem):
                outputFile.write('%s</%s>' % (i,elem.tag))
            else:
                outputFile.write('/>')
            if elem.tail and elem.tail.strip():
               
outputFile.write(elem.tail.strip('\n').encode('utf-8'))
            depth -= 1
            elem.clear()

Olivier.

>>> Stefan Behnel <stefan_ml at behnel.de> 11/02/08 7:56 pm >>>
Hi,

Olivier Collioud wrote:
> I would like to use my favourite text diffing tool to compare XML
> files.

Which is not lxml.html.diff, I assume? (I'm not sure how HTML specific
that
is, BTW). Also, for doctests, there is lxml.usedoctest that you can
import
(the lxml web pages use it for doctests).


> Is their a way to produce a pretty printed canonical version of my
XML
> files using lxml ?

Not using the c14n interface (libxml2 doesn't support it). Serialising
by hand
is not too hard, though. You can look at ElementTree._write() for an
example:

http://svn.effbot.org/public/elementtree/elementtree/ElementTree.py 

Stefan

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