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Powerful and Pythonic XML processing library combining libxml2/libxslt with the ElementTree API.

Project description

lxml is a Pythonic, mature binding for the libxml2 and libxslt libraries. It provides safe and convenient access to these libraries using the ElementTree API.

It extends the ElementTree API significantly to offer support for XPath, RelaxNG, XML Schema, XSLT, C14N and much more.

To contact the project, go to the project home page or see our bug tracker at

In case you want to use the current in-development version of lxml, you can get it from the github repository at . Note that this requires Cython to build the sources, see the build instructions on the project home page. To the same end, running easy_install lxml==dev will install lxml from if you have an appropriate version of Cython installed.

After an official release of a new stable series, bug fixes may become available at . Running easy_install lxml==3.0bugfix will install the unreleased branch state from as soon as a maintenance branch has been established. Note that this requires Cython to be installed at an appropriate version for the build.

3.0 (2012-10-08)

Features added

  • Python level access to (optional) libxml2 memory debugging features to simplify debugging of memory leaks etc.

  • The .iter() method of elements now accepts tag arguments like "{*}name" to search for elements with a given local name in any namespace. With this addition, all combinations of wildcards now work as expected: "{ns}name", "{}name", "{*}name", "{ns}*", "{}*" and "{*}*". Note that "name" is equivalent to "{}name", but "*" is "{*}*". The same change applies to the .getiterator(), .itersiblings(), .iterancestors(), .iterdescendants(), .iterchildren() and .itertext() methods;the strip_attributes(), strip_elements() and strip_tags() functions as well as the iterparse() class.

  • C14N allows specifying the inclusive prefixes to be promoted to top-level during exclusive serialisation.

  • Initial support for building in PyPy (through cpyext).

  • DTD objects gained an API that allows read access to their declarations.

  • gained support for parsing line-by-line (e.g. from grep output) and for surrounding the output with a new root tag.

  • E-factory in lxml.builder accepts subtypes of known data types (such as string subtypes) when building elements around them.

  • Tree iteration and iterparse() with a selective tag argument supports passing a set of tags. Tree nodes will be returned by the iterators if they match any of the tags.

Bugs fixed

  • End-of-file handling was incorrect in iterparse() when reading from a low-level C file stream and failed in libxml2 2.9.0 due to its improved consistency checks.

  • Passing long Unicode strings into the feed() parser interface failed to read the entire string.

  • The .find*() methods in lxml.objectify no longer use XPath internally, which makes them faster in many cases (especially when short circuiting after a single or couple of elements) and fixes some behavioural differences compared to lxml.etree. Note that this means that they no longer support arbitrary XPath expressions but only the subset that the ElementPath language supports. The previous implementation was also redundant with the normal XPath support, which can be used as a replacement.

  • el.find('*') could accidentally return a comment or processing instruction that happened to be in the wrong spot. (Same for the other .find*() methods.)

  • The error logging is less intrusive and avoids a global setup where possible.

  • Fixed undefined names in html5lib parser.

  • did not work in Python 3.

  • Element.attrib.update() did not accept an attrib of another Element as parameter.

  • For subtypes of ElementBase that make the .text or .tail properties immutable (as in objectify, for example), inserting text when creating Elements through the E-Factory feature of the class constructor would fail with an exception, stating that the text cannot be modified.

Other changes

  • The build no longer uses Cython by default unless the generated C files are missing. To use Cython, pass the option “–with-cython”. To ignore the fatal build error when Cython is required but not available (e.g. to run special commands that do not actually run a build), pass “–without-cython”.

  • The code was adapted to work with the upcoming libxml2 2.9.0 release.

  • The code base was overhauled to properly use ‘const’ where the API of libxml2 and libxslt requests it. This also has an impact on the public C-API of lxml itself, as defined in etreepublic.pxd, as well as the provided declarations in the lxml/includes/ directory. Code that uses these declarations may have to be adapted. On the plus side, this fixes several C compiler warnings, also for user code, thus making it easier to spot real problems again.

  • The functionality of “lxml.cssselect” was moved into a separate PyPI package called “cssselect”. To continue using it, you must install that package separately. The “lxml.cssselect” module is still available and provides the same interface, provided the “cssselect” package can be imported at runtime.

  • Element attributes passed in as an attrib dict or as keyword arguments are now sorted by (namespaced) name before being created to make their order predictable for serialisation and iteration. Note that adding or deleting attributes afterwards does not take that order into account, i.e. setting a new attribute appends it after the existing ones.

  • Several classes that are for internal use only were removed from the lxml.etree module dict: _InputDocument, _ResolverRegistry, _ResolverContext, _BaseContext, _ExsltRegExp, _IterparseContext, _TempStore, _ExceptionContext, __ContentOnlyElement, _AttribIterator, _NamespaceRegistry, _ClassNamespaceRegistry, _FunctionNamespaceRegistry, _XPathFunctionNamespaceRegistry, _ParserDictionaryContext, _FileReaderContext, _ParserContext, _PythonSaxParserTarget, _TargetParserContext, _ReadOnlyProxy, _ReadOnlyPIProxy, _ReadOnlyEntityProxy, _ReadOnlyElementProxy, _OpaqueNodeWrapper, _OpaqueDocumentWrapper, _ModifyContentOnlyProxy, _ModifyContentOnlyPIProxy, _ModifyContentOnlyEntityProxy, _AppendOnlyElementProxy, _SaxParserContext, _FilelikeWriter, _ParserSchemaValidationContext, _XPathContext, _XSLTResolverContext, _XSLTContext, _XSLTQuotedStringParam

  • Several internal classes can no longer be inherited from: _InputDocument, _ResolverRegistry, _ExsltRegExp, _ElementUnicodeResult, _IterparseContext, _TempStore, _AttribIterator, _ClassNamespaceRegistry, _XPathFunctionNamespaceRegistry, _ParserDictionaryContext, _FileReaderContext, _PythonSaxParserTarget, _TargetParserContext, _ReadOnlyPIProxy, _ReadOnlyEntityProxy, _OpaqueDocumentWrapper, _ModifyContentOnlyPIProxy, _ModifyContentOnlyEntityProxy, _AppendOnlyElementProxy, _FilelikeWriter, _ParserSchemaValidationContext, _XPathContext, _XSLTResolverContext, _XSLTContext, _XSLTQuotedStringParam, _XSLTResultTree, _XSLTProcessingInstruction

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