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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==4.0bugfix 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.

4.0.0 (2017-09-17)

Features added

  • The ElementPath implementation is now compiled using Cython, which speeds up the .find*() methods quite significantly.

  • The modules lxml.builder, lxml.html.diff and lxml.html.clean are also compiled using Cython in order to speed them up.

  • xmlfile() supports async coroutines using async with and await.

  • iterwalk() has a new method skip_subtree() that prevents walking into the descendants of the current element.

  • RelaxNG.from_rnc_string() accepts a base_url argument to allow relative resource lookups.

  • The XSLT result object has a new method .write_output(file) that serialises output data into a file according to the <xsl:output> configuration.

Bugs fixed

  • GH#251: HTML comments were handled incorrectly by the soupparser. Patch by mozbugbox.

  • LP#1654544: The html5parser no longer passes the useChardet option if the input is a Unicode string, unless explicitly requested. When parsing files, the default is to enable it when a URL or file path is passed (because the file is then opened in binary mode), and to disable it when reading from a file(-like) object.

    Note: This is a backwards incompatible change of the default configuration. If your code parses byte strings/streams and depends on character detection, please pass the option guess_charset=True explicitly, which already worked in older lxml versions.

  • LP#1703810: etree.fromstring() failed to parse UTF-32 data with BOM.

  • LP#1526522: Some RelaxNG errors were not reported in the error log.

  • LP#1567526: Empty and plain text input raised a TypeError in soupparser.

  • LP#1710429: Uninitialised variable usage in HTML diff.

  • LP#1415643: The closing tags context manager in xmlfile() could continue to output end tags even after writing failed with an exception.

  • LP#1465357: xmlfile.write() now accepts and ignores None as input argument.

  • Compilation under Py3.7-pre failed due to a modified function signature.

Other changes

  • The main module source files were renamed from lxml.*.pyx to plain *.pyx (e.g. etree.pyx) to simplify their handling in the build process. Care was taken to keep the old header files as fallbacks for code that compiles against the public C-API of lxml, but it might still be worth validating that third-party code does not notice this change.

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