Installing lxml

For special installation instructions regarding MS Windows and MacOS-X, see the specific sections below.

Contents

Requirements

You need Python 2.6 or later.

Unless you are using a static binary distribution (e.g. from a Windows binary installer), you need to install libxml2 and libxslt, in particular:

Newer versions generally contain fewer bugs and are therefore recommended. XML Schema support is also still worked on in libxml2, so newer versions will give you better compliance with the W3C spec.

To install the required development packages of these dependencies on Linux systems, use your distribution specific installation tool, e.g. apt-get on Debian/Ubuntu:

sudo apt-get install libxml2-dev libxslt-dev python-dev

Installation

The best way to install lxml is to get the pip package management tool and run the following as super-user (or administrator):

pip install lxml

To install a specific version, either download the distribution manually and let pip install that, or pass the desired version to pip:

pip install lxml==3.1.2

To speed up the build in test environments, e.g. on a continuous integration server, disable the C compiler optimisations by setting the CFLAGS environment variable:

CFLAGS="-O0"  pip install lxml

Building lxml from sources

If you want to build lxml from the GitHub repository, you should read how to build lxml from source (or the file doc/build.txt in the source tree). Building from developer sources or from modified distribution sources requires Cython to translate the lxml sources into C code. The source distribution ships with pre-generated C source files, so you do not need Cython installed to build from release sources.

If you have read these instructions and still cannot manage to install lxml, you can check the archives of the mailing list to see if your problem is known or otherwise send a mail to the list.

Using lxml with python-libxml2

If you want to use lxml together with the official libxml2 Python bindings (maybe because one of your dependencies uses it), you must build lxml statically. Otherwise, the two packages will interfere in places where the libxml2 library requires global configuration, which can have any kind of effect from disappearing functionality to crashes in either of the two.

To get a static build, either pass the --static-deps option to the setup.py script, or run pip with the STATIC_DEPS or STATICBUILD environment variable set to true, i.e.

STATIC_DEPS=true pip install lxml

The STATICBUILD environment variable is handled equivalently to the STATIC_DEPS variable, but is used by some other extension packages, too.

MS Windows

Most MS Windows systems lack the necessarily tools to build software, starting with a C compiler already. Microsoft leaves it to users to install and configure them, which is usually not trivial and means that distributors cannot rely on these dependencies being available on a given system. In a way, you get what you've paid for and make others pay for it.

Due to the additional lack of package management of this platform, it is best to link the library dependencies statically if you decide to build from sources, rather than using a binary installer. For that, lxml can use the binary distribution of libxml2 and libxslt, which it downloads automatically during the static build. It needs both libxml2 and libxslt, as well as iconv and zlib, which are available from the same download site. Further build instructions are in the source build documentation.

MacOS-X

A macport of lxml is available. Try something like port install py25-lxml.

If you want to use a more recent lxml release, you may have to build it yourself. While the pre-installed system libraries of libxml2 and libxslt are less outdated in recent MacOS-X versions than they used to be, so lxml should work them them out of the box, it is still recommended to use a static build with the most recent versions.

Luckily, lxml's setup.py script has built-in support for building and integrating these libraries statically during the build. Please read the MacOS-X build instructions.