Mailman 3 March 2017 - lxml - The Python XML Toolkit

[lxml-dev] lxml has its page on launchpad
by Stefan Behnel 10 Apr '23

10 Apr '23

Hi all, I added the lxml project to launchpad, the Ubuntu Bug-Tracker. It also has a FAQ engine and a couple of other goodies. https://launchpad.net/lxml It's easy to sign up for launchpad, BTW, no 90%-footnotes-contract. Have fun, Stefan

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[lxml-dev] Checking whether a node is a comment/element
by Geoffrey Sneddon 09 Apr '23

09 Apr '23

Hi, What's the best way to check whether a given node is a comment or an element? For the former, I'm currently using isinstance(node, etree._Comment), which is rather obviously sub-optimal. -- Geoffrey Sneddon <http://gsnedders.com/>

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[lxml-dev] Reparenting a node
by Lawrence Oluyede 30 Jan '23

30 Jan '23

I have a doc A and a doc B, I'd like to put a node extracted from A in the document B but I always get a ValueError: ValueError: Element is not a child of this node. I didn't find any "setparent" in the API. How can I do this? -- Lawrence, oluyede.org - neropercaso.it "It is difficult to get a man to understand something when his salary depends on not understanding it" - Upton Sinclair

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[lxml-dev] lxml 2.0.5 released
by Stefan Behnel 11 Jan '23

11 Jan '23

Hi all, lxml 2.0.5 is on PyPI. This is a bug-fix-only release of the stable 2.0 series. Have fun, Stefan 2.0.5 (2008-05-01) Bugs fixed * Resolving to a filename in custom resolvers didn't work. * lxml did not honour libxslt's second error state "STOPPED", which let some XSLT errors pass silently. * Memory leak in Schematron with libxml2 >= 2.6.31.

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[lxml-dev] Building LXML Trunk
by Sidnei da Silva 30 Aug '22

30 Aug '22

Hi, I've tried to build lxml from trunk today, on Win32. Got the following error: src\lxml\etree.c(880) : error C2059: syntax error : ')' src\lxml\etree.c(881) : error C2059: syntax error : ')' src\lxml\etree.c(882) : error C2059: syntax error : ')' src\lxml\etree.c(883) : error C2059: syntax error : ')' Any clue? Smells like a Pyrex issue? -- Sidnei da Silva Enfold Systems http://enfoldsystems.com Fax +1 832 201 8856 Office +1 713 942 2377 Ext 214

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thread-specific data for xslt callbacks
by Bob Kline 13 Oct '17

13 Oct '17

I need to make some thread-specific data available to my xslt function callbacks. I think I've sort of reverse-engineered a way to do it, by creating my own parser class, stuffing the data I need into an instance of that class, using the parser instance to parse the XSL/T filter, and then in the extension function following the context argument's context_node to its root tree, which in turn gets me back to my own parser object (and my thread-specific data). Is there a more elegant way to do it that I just haven't yet stumbled across in reading through the API docs? Thanks! -- Bob Kline http://www.rksystems.com mailto:bkline@rksystems.com

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Problem with XML Schema validation
by Frank Millman 26 Mar '17

26 Mar '17

Hi all There seems to be 2 ways of validating an xml document with XML Schema. One way is to create a XMLParser object and pass it an XMLSchema object as an argument. If you use this parser object with etree.parse() or etree.fromstring(), it validates the document against the schema. The other way is to parse the document first, and then validate it using XMLSchema.validate() or XMLSchema.assertValid(). I have always used the first method – I was unaware of the second one. However, I have just found a particular error that is detected by the second method, but not by the first one. The error is the use of duplicate “id” attributes, if it is specified in the schema as being of type “xs:ID”. I have a document with duplicate ids. Validating with the first method passes. Validating the same document, with the same schema, using the second method, gives the following - lxml.etree.DocumentInvalid: Element '{http://www.omg.org/spec/BPMN/20100524/MODEL}dataOutput', attribute 'id': 'user_row_id' is not a valid value of the atomic type 'xs:ID'., line 38 Is this a bug? Should I always use the second method? I am using lxml version 3.6.4. Thanks Frank Millman

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Xpath extension functions and return values
by Frank Millman 24 Mar '17

24 Mar '17

Hi all I am starting to use Xpath Extension Functions. They work, and they are great, but the results are not quite what I was expecting. If the return value is a string, it returns a <class 'lxml.etree._ElementUnicodeResult'>, which I assume is a smart string. I am happy with this, and I do realise that I can disable this and get back a normal string if desired. If the return value is an integer, it returns a float. Not great, but I can live with that. If the return value is None, it returns an empty list, which seems odd. Just curious if there is an underlying reason for the last two. What follows is the code I used to produce these results. Thanks for any insight. Frank Millman P.S. I just experimented with wrapping the return value with json.dumps(), and unwrapping it with json.loads() on return. It works, and I get the results I expect, provided I disable smart strings. So this is an option if I felt strongly about it – not sure yet. >>> from lxml import etree >>> >>> D = dict() >>> D['a'] = 'hallo' >>> D['b'] = 99 >>> D['c'] = None >>> >>> def get_val(context, key): ... return D[key] ... >>> ns = etree.FunctionNamespace(None) >>> ns['get_val'] = get_val >>> >>> xml = etree.fromstring('<w><x>a</x><y>b</y><z>c</z></w>') >>> >>> ans = xml.xpath('get_val(string(x))') >>> print(ans) hallo >>> print(type(ans)) <class 'lxml.etree._ElementUnicodeResult'> >>> >>> ans = xml.xpath('get_val(string(y))') >>> print(ans) 99.0 >>> print(type(ans)) <class 'float'> >>> >>> ans = xml.xpath('get_val(string(z))') >>> print(ans) [] >>> print(type(ans)) <class 'list'> >>>

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puzzled by xml declaration ps.
by Martin Mueller 20 Mar '17

20 Mar '17

Ater posting this query it occurred to me that I could do the following: declaration = '<?xml version="1.0" encoding="utf-8"?>' print(declaration, '\n', etree.tostring(tree, encoding='unicode', pretty_print=True)) That works.Is there a more elegant or formal way of doing it? ===== I usually serialize lxml trees (lxml 3.7, python 3.6) with the command print(etree.tostring(tree, encoding=”unicode”, pretty_print=True) That command strips the xml declaration from the first line. This happens to matter at some level to the eXist, the database I use. I posed a question on this list a couple of weeks ago about how to keep the declaration. Holger Jouki helpfully suggested that I need to add an explicit xml_declaration. There are of postings on Stack Overflow, mainly from a few years ago, that say the same thing. However, if I add the “xml_declaration=True” to the above command, I get the error message File "/Users/martin/Dropbox/PycharmProjects/earlyprint/transform/try12.py", line 62, in <module> print(etree.tostring(tree, xml_declaration =True, encoding="unicode" , pretty_print=True),file=fileout) File "src/lxml/lxml.etree.pyx", line 3320, in lxml.etree.tostring (src/lxml/lxml.etree.c:80187) ValueError: Serialisation to unicode must not request an XML declaration If I formulate the command (as recommended by Stack Overflow) as Print(etree.tostring(tree, encoding=”utf-8”, xml_declaration=True, pretty_print=True) I do indeed get the xml declaration, but the file is processed in “b’” format, with line breaks given as ‘\n;’, which is not what I want. I assume that “encoding=”unicode” is or should be the common garden variety form of serializing in the world of Python 3.x. But how can I assure that serialization will keep rather than drop the xml declaration? There are ways of adding afterwards but that’s rather kludgy, and it’s also easy to forget it. Grateful for any help MM

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puzzled by xml declaration
by Martin Mueller 18 Mar '17

18 Mar '17

I usually serialize lxml trees (lxml 3.7, python 3.6) with the command print(etree.tostring(tree, encoding=”unicode”, pretty_print=True) That command strips the xml declaration from the first line. This happens to matter at some level to the eXist, the database I use. I posed a question on this list a couple of weeks ago about how to keep the declaration. Holger Jouki helpfully suggested that I need to add an explicit xml_declaration. There are of postings on Stack Overflow, mainly from a few years ago, that say the same thing. However, if I add the “xml_declaration=True” to the above command, I get the error message File "/Users/martin/Dropbox/PycharmProjects/earlyprint/transform/try12.py", line 62, in <module> print(etree.tostring(tree, xml_declaration =True, encoding="unicode" , pretty_print=True),file=fileout) File "src/lxml/lxml.etree.pyx", line 3320, in lxml.etree.tostring (src/lxml/lxml.etree.c:80187) ValueError: Serialisation to unicode must not request an XML declaration If I formulate the command (as recommended by Stack Overflow) as Print(etree.tostring(tree, encoding=”utf-8”, xml_declaration=True, pretty_print=True) I do indeed get the xml declaration, but the file is processed in “b’” format, with line breaks given as ‘\n;’, which is not what I want. I assume that “encoding=”unicode” is or should be the common garden variety form of serializing in the world of Python 3.x. But how can I assure that serialization will keep rather than drop the xml declaration? There are ways of adding afterwards but that’s rather kludgy, and it’s also easy to forget it. Grateful for any help MM

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