Mailman 3 April 2012 - lxml - The Python XML Toolkit

How to deal with XMLSchema IOError?
by Piotr Oh 27 Apr '12

27 Apr '12

Hi How to check for errors when loading XMLSchema file? schema=etree.XMLSchema(file=polonSchemaFile) and the polonSchemaFile does not exist. lxml reports: schema=etree.XMLSchema(file=polonSchemaFile) File "xmlschema.pxi", line 105, in lxml.etree.XMLSchema.__init__ (src/lxml\lxml.etree.c:132720) lxml.etree.XMLSchemaParseError: failed to load external entity "polon-v2/XSD.2.0/plikImp.xsd" Exception handling does not help here I suppose? P.

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compiling a static lxml with Python3 on x86_64 linux
by Greg Fischer 26 Apr '12

26 Apr '12

Hello, I'm in a bit of a peculiar situation. I'm attempting to compile lxml with Python3 using statically-linked libraries on x86_64 linux (SLES 10, to be exact). I also do not have root access to the machine in question, so I must compile all the dependencies from source and install them to a location within my home directory. I've tried to use the staticlxml recipe ( http://pypi.python.org/pypi/z3c.recipe.staticlxml), but it appears to not work with buildout 2.0.0a1/Python3. Using "python3 setup.py build --static-deps" fails because when the dependencies are built, it does not automatically include "-fPIC" in the CFLAGS, as is apparently required on x86_64 linux platforms. I believe I have successfully compiled all of the dependencies manually (with -fPIC) and installed them to a location in my home directory. If I re-execute the "build --static-deps" command, the script will attempt to re-download the source executables for the dependencies, which wipes out my "-fPIC" change. How do I use the "setup.py" script to statically link against the libraries in my home directory? Thanks, Greg

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Re: [lxml] cssselect
by Laurence Rowe 20 Apr '12

20 Apr '12

On 11 April 2012 12:55, Simon Sapin <simon.sapin(a)kozea.fr> wrote: > I started something here but it is very much in progress: > > https://github.com/SimonSapin/cssselect Many thanks for doing this Simon! I always think it's helpful to have multiple maintainers for a package where possible. Would it make sense to move the repository into the lxml organisation on github and add Stefan as an owner on PyPI as it will presumably become a dependency of lxml in due course. Laurence

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Allocating xml/xslt in shared memory
by Evgeny Turnaev 19 Apr '12

19 Apr '12

Hello Stefan, Do You think it is possible to allocate xml/xsl in shared memory? My wsgi application uses lxml to parse config files (xml) and xls stylesheets. Both configs and xsl parsed at application start and do not modified till application exists. Rss for 1 process just after xml/xsl parsing grows 15Mb (production - 15 modules) and 35 Mb (debug - 25 modules). The modules numbler will only grow in time. Currently we have 50 workers - so 15Mb * 50 = 750Mb for xml/xsl that never changes. I suppose it is not shared across forks because of python incref/decref nature but i may be wrong? Do you think it will be possible to use xmlMemSetup ( http://xmlsoft.org/html/libxml-xmlmemory.html#xmlMemSetup ) to setup xmllib to use custom malloc that will be using mmap? How lxml will behave if i do so? Do any xslt object internal structures changed while i call xslt(xml_doc) from python? -- -------------------------------------------- Турнаев Евгений Викторович +7 906 875 09 43 --------------------------------------------

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cssselect tokenizer and parser
by Simon Sapin 18 Apr '12

18 Apr '12

Hi, I’ve been reviewing the parser in cssselect and fixing a lot of bugs, as you can see in recent commits[1]. I’m about to make more significant changes to the tokenizer and the parser to fix the underlying problem behind lxml bug #19 [2] and many related bugs. In short, the tokenizer omits most whitespace, including some that represent a descendant combinator. To compensate, the parser just assumes a descendant combinator (sometimes incorrectly) whenever it can not find something else that it expected. So I’m going to touch most of this code, but I’m still a bit uneasy with it. There are many corner cases where it does not matches the grammar in the spec[3]. In particular, the behavior in arguments for functional pseudo-classes it a bit strange, if not plain wrong. I would like to write a tokenizer+parser more closely based on the grammar. Now, I just happen to have in tinycss[4] a CSS tokenizer that already handles all the gory details of backslash-escaping, parsing numbers, etc. I actually have two implementations of it: one in pure Python for compatibility, and one in Cython for speed. (The tokenizer performance is critical when parsing whole stylesheets; perhaps less so for comparatively small selectors.) However, tinycss currently only supports Python 2.6+. So, what do you think of this whole situation? Should we re-use the tinycss tokenizer? Duplicate its code? Try and fix the buggy one? [1] https://github.com/SimonSapin/cssselect/commits/master [2] https://github.com/lxml/lxml/pull/19/files [3] http://www.w3.org/TR/selectors/#w3cselgrammar [4] http://packages.python.org/tinycss/ Regards, -- Simon Sapin

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How to report validation errors in user friendly way
by Piotr Oh 11 Apr '12

11 Apr '12

Hi Using schema.validate(tree) shows errors in english. To my users it is not very friendly way of problem reporting. What is the clever way to talk to user in his native language from validation routines? Or maybe I ask in other way: how to parse xml file after its validation, where validator told me where the errors are and I'd like to say to the user that the person xx has bad yy child (for example date). Assuming such xml structure: <persons> <person> <name>John</name> <date>2012-03-</date> - error </person> .... </persons> For me just printing the schema.error_log is ok, but not for the end user. Now I'm using validate() method but maybe assertValid() is the way to go? I'm not a programmer, the task I have done so far is take csv file translate it to xml file, write it and then validate it. And it is working fine. But doing user friendly program is tough task. So some guidelines are welcome. Thanx and regards Piotr

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Suggestions for cssselect
by Simon Sapin 11 Apr '12

11 Apr '12

Hi, I would like to make some changes in cssselect (and provide patches): 1. Change :link, :visited, :target, :hover, :active and :focus to never match (silently, or maybe with a warning?) instead of raising. They could translate to XPath [false] 2. Make :checked HTML-specific. (The implementation already is.) This would involve having a document_language parameter which would default to HTML in HTMLElement.cssselect and plain XML otherwise. :checked would raise on non-HTML documents. Having this parameter could eventually allow a language-specific (as in HTML vs. XML) implementation of :lang(). 3. Implement :enabled and :disabled similarly to :checked. Assuming 2, they would also be HTML-specific. (The docs mention :unchecked and :indeterminate but there is no such thing in the code or the selectors3 spec.) What do you think? Regards, -- Simon Sapin

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