Mailman 3 September 2005 - lxml - The Python XML Toolkit

[lxml-dev] Pyrex officially supports gcc4
by Olivier Grisel 03 Nov '05

03 Nov '05

http://comments.gmane.org/gmane.comp.python.announce/5559 That will make it easier to build lxml on recent linux and MacOSX platforms. -- Olivier

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[lxml-dev] a patch for setup.py when libxml2 and libxslt are built to separate dir
by Trent Mick 03 Nov '05

03 Nov '05

Hello, I'm just starting to play with lxml and am quite pleased with it so far. Thank you for creating it. I have a small patch for setup.py that, if people think is reasonable, I'd like to see applied to lxml repo. Although probably not typical, one can build libxml2 and libxslt to separate directories. Say something like this: ~/opt/libxml2-2.6.22/... ~/opt/libxslt-1.1.15/... In that situation libxml2's "xml2-config" does not know how to return the proper compilation and link flags for both libxml2 and libxslt. However, libxslt (which depends on libxml2, of course) knows how: $ xml2-config --cflags -I/Users/trentm/opt/libxml2-2.6.22/include/libxml2 $ xslt-config --cflags -I/Users/trentm/opt/libxslt-1.1.15/include -I/Users/trentm/opt/libxml2-2.6.22/include/libxml2 My patch (see attached) changes guess_dirs() to use xslt-config. What do you think? Trent -- Trent Mick trentm(a)gmail.com

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[lxml-dev] Python interpreter segfault setting element tail
by Kieran Holland 03 Nov '05

03 Nov '05

Thanks for lxml - very nice. Unfortunately the following fragment causes my python interpreter to crash and burn: ---------------- from lxml import etree root = etree.fromstring('<html><p></p>x</html>') for elem in root: elem.tail = '' ----------------- System: gentoo linux 2004.3 on x86 python 2.4.1 lxml 0.7 (and 0.6) libxml 2.6.19 Kieran

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[lxml-dev] Crash report
by Steve Howe 27 Sep '05

27 Sep '05

Hello all, While I know this is incorrect, I think lxml *should* be handling this nicer: >> etree.SubElement(None, 'a') zsh: segmentation fault (core dumped) ipython Could this please be fixed ? I'm using SVN trunk revision 17870. -- Best regards, Steve mailto:howe@carcass.dhs.org

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[lxml-dev] Any estimates for next lxml release?
by dharana 24 Sep '05

24 Sep '05

Hello guys, Are you planning to release a new version soon? Several segfaults fixed in the dev version are really useful for me and I would feel better if I used an official release (I'm using lxml 0.7 in production) than an snapshot. Thank you, -- dharana

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[lxml-dev] Useful snippet: namespace objects
by Robert Kern 18 Sep '05

18 Sep '05

I've attached a piece of code that I wrote to make dealing with namespaces a bit easier in lxml and ElementTree. You create a namespace object with the short prefix and the URI of the namespace. You generate fully qualified tag names through __getattr__ hackery (or __getitem__ hackery if the tag isn't a valid Python identifier). rdf = XMLNS('rdf', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#') xsl = XMLNS('xsl', 'http://www.w3.org/1999/XSL/Transform') dc = XMLNS('dc', 'http://purl.org/dc/elements/1.1/') rdf.RDF == '{http://www.w3.org/1999/02/22-rdf-syntax-ns#}RDF' xsl['value-of'] == '{http://www.w3.org/1999/XSL/Transform}value-of' Also, there's a convenience function nsmap(*args) which will create the appropriate dictionary for passing to the nsmap keyword argument of etree.Element(). E.g. etree.Element(rdf.RDF, nsmap=nsmap(rdf, dc)) I've found this to be quite handy. -- Robert Kern rkern(a)ucsd.edu "In the fields of hell where the grass grows high Are the graves of dreams allowed to die." -- Richard Harter #***************************************************************************** # Copyright (C) 2005 Robert Kern. All rights reserved. # # Distributed under the terms of the BSD License. The full license is in # the file COPYING, distributed as part of this software. #***************************************************************************** class XMLNS(object): """Convenience object for handling namespaced tag names in ElementTree-like APIs. ElementTree-like APIs use an inconvenient syntax for representing tags within namespaces. E.g. rdf:RDF -> {http://www.w3.org/1999/02/22-rdf-syntax-ns#}RDF dc:creator -> {http://purl.org/dc/elements/1.1/}creator Instances of XMLNS use __getattr__ magic to generate tags with this syntax. You can also use __getitem__ for those tags which are not valid Python identifiers. rdf = XMLNS('rdf', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#') xsl = XMLNS('xsl', 'http://www.w3.org/1999/XSL/Transform') rdf.RDF == '{http://www.w3.org/1999/02/22-rdf-syntax-ns#}RDF' xsl['value-of'] == '{http://www.w3.org/1999/XSL/Transform}value-of' Constructor: XMLNS(prefix, url) """ def __init__(self, prefix, url): self._url = url self._qname_prefix = u'{%s}'%url self._prefix = prefix def __getitem__(self, tag): return self._qname_prefix + tag __getattr__ = __getitem__ def nsmap(*args): """Create a dictionary mapping prefixes to namespace URLs from XMLNS instances. """ d = {} for ns in args: d[ns._prefix] = ns._url return d rdf = XMLNS('rdf', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#') dc = XMLNS('dc', 'http://purl.org/dc/elements/1.1/') xsl = XMLNS('xsl', 'http://www.w3.org/1999/XSL/Transform')

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Re: [lxml-dev] Full XPath support ?
by Martijn Faassen 13 Sep '05

13 Sep '05

David Levy wrote: > Thanks ! I did test it successfully too yet. However iterpase is not > supported :( So i can not parse large file (>100Mo) ...?! > I am trying to mix celementtree and lxml right now !! lxml right now is not optimal for parsing such large files. Support for iterparse would be nice though likely a lot of work, and full xpath support in that context might be extremely hard to accomplish. libxml2 does seem to have something called 'streaming xpath' that might be useful in this area though (but this is not yet exposed to lxml either). Regards, Martijn

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[lxml-dev] Repeating RelaxNG validation
by Robert Kern 12 Sep '05

12 Sep '05

Hi there, I'm in the process of testing hooks for reporting libxml2's so-called "structured errors" in lxml. Among other things, I want to get a more diagnostic message when a document fails to validate against a RelaxNG schema. I ran across a problem where an invalid document will fail the validation the first time but succeed when the validation is repeated. I haven't been able to isolate a small test case, unfortunately; my attempts at simplification give the expected results. I am on OS X 10.4 using lxml pristine from SVN, libxml2 2.6.20 and libxslt 1.1.14 (note: these are *not* the ones that come with the OS but the problem exists there, too). Attached are the RelaxNG schema, the invalid document, and a failing unit test. I hope they're not too large for the list. I apologize in advance if they are. FYI: the invalid element is /notebook/sheet/ipython-block/para on line 18. Thank you, in advance! -- Robert Kern rkern(a)ucsd.edu "In the fields of hell where the grass grows high Are the graves of dreams allowed to die." -- Richard Harter <notebook> <head> <meta content="/usr/local/bin/ipython" name="cmdline"> </meta> </head> <sheet> <title>Scipy Tutorial</title> <para>There are two (interchangeable) ways to deal with 1-d polynomials in Scipy. The first is to use the <emphasis role="bold">poly1d</emphasis> class in <emphasis role="bold">scipy_base</emphasis>. This class accepts coefficients or polynomial roots to initialize a polynomial. The polynomial object can then be manipulated in algebraic expressions, integrated, differentiated, and evaluated. It even prints like a polynomial: </para> <ipython-block logid="default-log"> <para>This shouldn't be here.</para> <ipython-cell type="input" number="3"> </ipython-cell> <ipython-cell type="input" number="4"> </ipython-cell> <ipython-cell type="input" number="5"> </ipython-cell> <ipython-cell type="stdout" number="5"> </ipython-cell> <ipython-cell type="input" number="6"> </ipython-cell> <ipython-cell type="stdout" number="6"> </ipython-cell> <ipython-cell type="input" number="7"> </ipython-cell> <ipython-cell type="stdout" number="7"> </ipython-cell> <ipython-cell type="input" number="8"> </ipython-cell> <ipython-cell type="output" number="8"> </ipython-cell> <ipython-cell type="input" number="9"> </ipython-cell> <ipython-cell type="output" number="9"> </ipython-cell> </ipython-block> <para>The other way to handle polynomials is an array of coefficients with the first element of the array giving the coefficient of the highest power. There are explicit functions to add, subtract, multiply, divide, integrate, differentiate, and evalute polynomials represented as sequences of coefficients. </para> </sheet> <ipython-log id="default-log"><cell number="3"><input> from scipy import * </input></cell> <cell number="4"><input> p = poly1d([3,4,5]) </input></cell> <cell number="5"><input> print p </input><stdout> 2 3 x + 4 x + 5 </stdout></cell> <cell number="6"><input> print p*p </input><stdout> 4 3 2 9 x + 24 x + 46 x + 40 x + 25 </stdout></cell> <cell number="7"><input> print p.integ(k=6) </input><stdout> 3 2 x + 2 x + 5 x + 6 </stdout></cell> <cell number="8"><input> p.deriv() </input><output>poly1d([6, 4]) </output></cell> <cell number="9"><input> p([4,5]) </input><output>array([ 69, 100]) </output></cell> </ipython-log> </notebook> import unittest from lxml import etree class DuplicateRelaxNGTestCase(unittest.TestCase): def test_once(self): rng = etree.RelaxNG(file='nbk.rng') baddoc = etree.parse('tut-2.3.5-bad.nbk') self.assert_(not rng.validate(baddoc)) # try again self.assert_(not rng.validate(baddoc)) def test_suite(): suite = unittest.TestSuite() suite.addTests([unittest.makeSuite(DuplicateRelaxNGTestCase)]) return suite if __name__ == '__main__': unittest.main()

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[lxml-dev] Full XPath support ?
by David Levy 12 Sep '05

12 Sep '05

Hi I can not find the detail about full XPath support in lxml (I know cElementTree does not)/ I guess it could be easy as it is build on top of libxslt. So can you tell me if xpath expression filtering on attributes and element positions are supported for instance ? Thanks in advance David LEVY

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[lxml-dev] Another crash report
by Steve Howe 10 Sep '05

10 Sep '05

Hello all, I have this sample program is crashing on Windows XP and giving lots of error messages and even core dumping sometimes on FreeBSD. The messages: [...] python in free(): warning: page is already free python in free(): warning: page is already free python in free(): warning: chunk is already free [...] These (debug?) messages won't appear on XP, just a crash screen. If you have enough files on the dir, it will crash your Python interpreter even on FreeBSD. The program itself is available here: http://carcass.dhs.org/crash2.py I suspect it's related to the other bug (or perhaps the same) I reported days ago. Any clues ? Thanks. -- Best regards, Steve mailto:howe@carcass.dhs.org

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