Fast HTML/XML Template Compiler.
Project description
Overview
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.
Platform
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).
Performance
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).
Notes
Changes
2.0-rc7 (2011-03-29)
Bugfixes:
Fixed issue with Python 2.5 compatibility AST. This affected at least PyPy 1.4.
Features:
The auto_reload setting now defaults to the class value; the base template class gives a default value of chameleon.config.AUTO_RELOAD. This change allows a subclass to provide a custom default value (such as an application-specific debug mode setting).
2.0-rc6 (2011-03-19)
Features:
Added support for target_language keyword argument to render method. If provided, the argument will be curried onto the translation function.
Bugfixes:
The HTML entities ‘lt’, ‘gt’ and ‘quot’ appearing inside content subtition expressions are now translated into their native character values. This fixes an issue where you could not dynamically create elements using the structure (which is possible in ZPT). The need to create such structure stems from the lack of an expression interpolation operator in ZPT.
Fixed duplicate file pointer issue with test suite (affected Windows platforms only). This fixes issue #9. [oliora]
Use already open file using os.fdopen when trying to write out the module source. This fixes LP #731803.
2.0-rc5 (2011-03-07)
Bugfixes:
Fixed a number of issues concerning the escaping of attribute values:
Static attribute values are now included as they appear in the source.
This means that invalid attribute values such as "true && false" are now left alone. It’s not the job of the template engine to correct such markup, at least not in the default mode of operation.
The string expression compiler no longer unescapes values. Instead, this is left to each expression compiler. Currently only the Python expression compiler unescapes its input.
The dynamic escape code sequence now correctly only replaces ampersands that are part of an HTML escape format.
Imports:
The page template classes and the loader class can now be imported directly from the chameleon module.
Features:
If a custom template loader is not provided, relative paths are now resolved using os.abspath (i.e. to the current working directory).
Absolute paths are normalized using os.path.normpath and os.path.expanduser. This ensures that all paths are kept in their “canonical” form.
2.0-rc4 (2011-03-03)
Bugfixes:
Fixed an issue where the output of an end-to-end string expression would raise an exception if the expression evaluated to None (it should simply output nothing).
The convert function (which is configurable on the template class level) now defaults to the translate function (at run-time).
This fixes an issue where message objects were not translated (and thus converted to a string) using the a provided translate function.
Fixed string interpolation issue where an expression immediately succeeded by a right curly bracket would not parse.
This fixes issue #5.
Fixed error where tal:condition would be evaluated after tal:repeat.
Features:
Python expression is now a TALES expression. That means that the pipe operator can be used to chain two or more expressions in a try-except sequence.
This behavior was ported from the 1.x series. Note that while it’s still possible to use the pipe character (“|”) in an expression, it must now be escaped.
The template cache can now be shared by multiple processes.
2.0-rc3 (2011-03-02)
Bugfixes:
Fixed atexit handler.
This fixes issue #3.
If a cache directory is specified, it will now be used even when not in debug mode.
Allow “comment” attribute in the TAL namespace.
This fixes an issue in the sense that the reference engine allows any attribute within the TAL namespace. However, only “comment” is in common use.
The template constructor now accepts a flag debug which puts the template instance into debug-mode regardless of the global setting.
This fixes issue #1.
Features:
Added exception handler for exceptions raised while evaluating an expression.
This handler raises (or attempts to) a new exception of the type RenderError, with an additional base class of the original exception class. The string value of the exception is a formatted error message which includes the expression that caused the exception.
If we are unable to create the exception class, the original exception is re-raised.
2.0-rc2 (2011-02-28)
Fixed upload issue.
2.0-rc1 (2011-02-28)
Initial public release. See documentation for what’s new in this series.
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