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Chameleon Template Compiler

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Chameleon is an HTML/XML template language compiler.

The distribution comes with a complete template engine: Chameleon Page Templates [1].

There are no external library dependencies [2]. You can install it using setuptools or the newer distribute (recommended):

$ easy_install Chameleon

Formatted documentation is available.


This library has been successfully tested on the following platforms:

  • Python 2.5, 2.6, 2.7
  • Python 3.1, 3.2
  • PyPy

What's New in 2.x

The 2.x series is a complete rewrite of the library and supports both Python 2.5+ and Python 3.1+ with a single source code.

For most users it should be an easy upgrade, however note that at present, there is no engine for the Genshi language.

New parser

This series features a new parser, implemented in pure Python. It parses both HTML and XML inputs (the previous parser relied on the expat system library and was more strict about its input).

Language changes

The 2.x engine matches the output of the reference implementation more closely (usually exactly). There are less differences altogether; for instance, the method of escaping TALES expression (usually a semicolon) has been changed to match that of the reference implementation.

This series also introduces a number of new language features:

1) Support for the tal:on-error from the reference specification has been added.

2) Inspired by the Genshi language, a pair of new attributes has been added: tal:switch and tal:case, allowing flexible conditions.

Expression engine

The expression engine has been redesigned to make it easier to understand and extend.

The engine is built on the ast module (available since Python 2.6; backports included for Python 2.5).


The compiler output has been optimized for complex templates. For most applications, the engine should perform similarly to the 1.x series.

Very simple templates with tight loops (such as that of the "big table" benchmark) will see a decrease in performance. The compiler is optimized for dynamic variable scope and this lowers performance for templates that require only a static scope.

License and Copyright

This software is made available as-is under a BSD-like license [3] (see included copyright notice).


[1] The template language specifications and API for the Page Templates engine are based on Zope Page Templates (see in particular zope.pagetemplate). However, the Chameleon compiler and Page Templates engine is an entirely new codebase, packaged as a standalone distribution. It does require a Zope software environment.
[2] The string translation interface is based on the gettext library. Chameleon comes with built-in support for the zope.i18n package which includes a translation framework (internationalization). If this package is installed, it will be used as the default translation framework. It is trivial to provide a custom translation function, however.
[3] This software is licensed under the Repoze license.
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