<!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <meta name="generator" content="Docutils 0.8.1: http://docutils.sourceforge.net/"> <title>Genshi: Genshi Text Template Language</title> <link rel="stylesheet" href="common/style/edgewall.css" type="text/css"> </head> <body> <div class="document" id="genshi-text-template-language"> <div id="navigation"> <span class="projinfo">Genshi 0.7</span> <a href="index.html">Documentation Index</a> </div> <h1 class="title">Genshi Text Template Language</h1> <p>In addition to the XML-based template language, Genshi provides a simple text-based template language, intended for basic plain text generation needs. The language is similar to the <a class="reference external" href="http://www.djangoproject.com/">Django</a> template language.</p> <p>This document describes the template language and will be most useful as reference to those developing Genshi text templates. Templates are text files of some kind that include processing <a class="reference internal" href="#directives">directives</a> that affect how the template is rendered, and template expressions that are dynamically substituted by variable data.</p> <p>See <a class="reference external" href="templates.html">Genshi Templating Basics</a> for general information on embedding Python code in templates.</p> <div class="note"> <p class="first admonition-title">Note</p> <p class="last">Actually, Genshi currently has two different syntaxes for text templates languages: One implemented by the class <tt class="docutils literal">OldTextTemplate</tt> and another implemented by <tt class="docutils literal">NewTextTemplate</tt>. This documentation concentrates on the latter, which is planned to completely replace the older syntax. The older syntax is briefly described under <a class="reference internal" href="#legacy">legacy</a>.</p> </div> <div class="contents topic" id="contents"> <p class="topic-title first">Contents</p> <ul class="auto-toc simple"> <li><a class="reference internal" href="#template-directives" id="id8">1 Template Directives</a><ul class="auto-toc"> <li><a class="reference internal" href="#conditional-sections" id="id9">1.1 Conditional Sections</a><ul class="auto-toc"> <li><a class="reference internal" href="#id1" id="id10">1.1.1 <tt class="docutils literal">{% if %}</tt></a></li> <li><a class="reference internal" href="#id2" id="id11">1.1.2 <tt class="docutils literal">{% choose %}</tt></a></li> </ul> </li> <li><a class="reference internal" href="#looping" id="id12">1.2 Looping</a><ul class="auto-toc"> <li><a class="reference internal" href="#id3" id="id13">1.2.1 <tt class="docutils literal">{% for %}</tt></a></li> </ul> </li> <li><a class="reference internal" href="#snippet-reuse" id="id14">1.3 Snippet Reuse</a><ul class="auto-toc"> <li><a class="reference internal" href="#id4" id="id15">1.3.1 <tt class="docutils literal">{% def %}</tt></a></li> <li><a class="reference internal" href="#id5" id="id16">1.3.2 <tt class="docutils literal">{% include %}</tt></a></li> </ul> </li> <li><a class="reference internal" href="#variable-binding" id="id17">1.4 Variable Binding</a><ul class="auto-toc"> <li><a class="reference internal" href="#id6" id="id18">1.4.1 <tt class="docutils literal">{% with %}</tt></a></li> </ul> </li> </ul> </li> <li><a class="reference internal" href="#white-space-and-line-breaks" id="id19">2 White-space and Line Breaks</a></li> <li><a class="reference internal" href="#id7" id="id20">3 Comments</a></li> <li><a class="reference internal" href="#legacy-text-template-syntax" id="id21">4 Legacy Text Template Syntax</a></li> </ul> </div> <div class="section" id="template-directives"> <span id="directives"></span><h1>1 Template Directives</h1> <p>Directives are template commands enclosed by <tt class="docutils literal">{% ... %}</tt> characters. They can affect how the template is rendered in a number of ways: Genshi provides directives for conditionals and looping, among others.</p> <p>Each directive must be terminated using an <tt class="docutils literal">{% end %}</tt> marker. You can add a string inside the <tt class="docutils literal">{% end %}</tt> marker, for example to document which directive is being closed, or even the expression associated with that directive. Any text after <tt class="docutils literal">end</tt> inside the delimiters is ignored, and effectively treated as a comment.</p> <p>If you want to include a literal delimiter in the output, you need to escape it by prepending a backslash character (<tt class="docutils literal">\</tt>).</p> <div class="section" id="conditional-sections"> <h2>1.1 Conditional Sections</h2> <div class="section" id="id1"> <span id="if"></span><h3>1.1.1 <tt class="docutils literal">{% if %}</tt></h3> <p>The content is only rendered if the expression evaluates to a truth value:</p> <div class="highlight"><pre><span class="x">{% if foo %}</span> <span class="x"> </span><span class="cp">${</span><span class="n">bar</span><span class="cp">}</span><span class="x"></span> <span class="x">{% end %}</span> </pre></div> <p>Given the data <tt class="docutils literal">foo=True</tt> and <tt class="docutils literal"><span class="pre">bar='Hello'</span></tt> in the template context, this would produce:</p> <pre class="literal-block"> Hello </pre> </div> <div class="section" id="id2"> <span id="otherwise"></span><span id="when"></span><span id="choose"></span><h3>1.1.2 <tt class="docutils literal">{% choose %}</tt></h3> <p>The <tt class="docutils literal">choose</tt> directive, in combination with the directives <tt class="docutils literal">when</tt> and <tt class="docutils literal">otherwise</tt>, provides advanced contional processing for rendering one of several alternatives. The first matching <tt class="docutils literal">when</tt> branch is rendered, or, if no <tt class="docutils literal">when</tt> branch matches, the <tt class="docutils literal">otherwise</tt> branch is be rendered.</p> <p>If the <tt class="docutils literal">choose</tt> directive has no argument the nested <tt class="docutils literal">when</tt> directives will be tested for truth:</p> <div class="highlight"><pre><span class="x">The answer is:</span> <span class="x">{% choose %}</span> <span class="x"> {% when 0 == 1 %}0{% end %}</span> <span class="x"> {% when 1 == 1 %}1{% end %}</span> <span class="x"> {% otherwise %}2{% end %}</span> <span class="x">{% end %}</span> </pre></div> <p>This would produce the following output:</p> <pre class="literal-block"> The answer is: 1 </pre> <p>If the <tt class="docutils literal">choose</tt> does have an argument, the nested <tt class="docutils literal">when</tt> directives will be tested for equality to the parent <tt class="docutils literal">choose</tt> value:</p> <div class="highlight"><pre><span class="x">The answer is:</span> <span class="x">{% choose 1 %}\</span> <span class="x"> {% when 0 %}0{% end %}\</span> <span class="x"> {% when 1 %}1{% end %}\</span> <span class="x"> {% otherwise %}2{% end %}\</span> <span class="x">{% end %}</span> </pre></div> <p>This would produce the following output:</p> <pre class="literal-block"> The answer is: 1 </pre> </div> </div> <div class="section" id="looping"> <h2>1.2 Looping</h2> <div class="section" id="id3"> <span id="for"></span><h3>1.2.1 <tt class="docutils literal">{% for %}</tt></h3> <p>The content is repeated for every item in an iterable:</p> <div class="highlight"><pre><span class="x">Your items:</span> <span class="x">{% for item in items %}\</span> <span class="x"> * </span><span class="cp">${</span><span class="n">item</span><span class="cp">}</span><span class="x"></span> <span class="x">{% end %}</span> </pre></div> <p>Given <tt class="docutils literal"><span class="pre">items=[1,</span> 2, 3]</tt> in the context data, this would produce:</p> <pre class="literal-block"> Your items * 1 * 2 * 3 </pre> </div> </div> <div class="section" id="snippet-reuse"> <h2>1.3 Snippet Reuse</h2> <div class="section" id="id4"> <span id="macros"></span><span id="def"></span><h3>1.3.1 <tt class="docutils literal">{% def %}</tt></h3> <p>The <tt class="docutils literal">def</tt> directive can be used to create macros, i.e. snippets of template text that have a name and optionally some parameters, and that can be inserted in other places:</p> <div class="highlight"><pre><span class="x">{% def greeting(name) %}</span> <span class="x"> Hello, </span><span class="cp">${</span><span class="n">name</span><span class="cp">}</span><span class="x">!</span> <span class="x">{% end %}</span> <span class="cp">${</span><span class="n">greeting</span><span class="p">(</span><span class="s">'world'</span><span class="p">)</span><span class="cp">}</span><span class="x"></span> <span class="cp">${</span><span class="n">greeting</span><span class="p">(</span><span class="s">'everyone else'</span><span class="p">)</span><span class="cp">}</span><span class="x"></span> </pre></div> <p>The above would be rendered to:</p> <pre class="literal-block"> Hello, world! Hello, everyone else! </pre> <p>If a macro doesn't require parameters, it can be defined without the parenthesis. For example:</p> <div class="highlight"><pre><span class="x">{% def greeting %}</span> <span class="x"> Hello, world!</span> <span class="x">{% end %}</span> <span class="cp">${</span><span class="n">greeting</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> </pre></div> <p>The above would be rendered to:</p> <pre class="literal-block"> Hello, world! </pre> </div> <div class="section" id="id5"> <span id="include"></span><span id="includes"></span><h3>1.3.2 <tt class="docutils literal">{% include %}</tt></h3> <p>To reuse common parts of template text across template files, you can include other files using the <tt class="docutils literal">include</tt> directive:</p> <div class="highlight"><pre><span class="x">{% include base.txt %}</span> </pre></div> <p>Any content included this way is inserted into the generated output. The included template sees the context data as it exists at the point of the include. <a class="reference internal" href="#macros">Macros</a> in the included template are also available to the including template after the point it was included.</p> <p>Include paths are relative to the filename of the template currently being processed. So if the example above was in the file "<tt class="docutils literal">myapp/mail.txt</tt>" (relative to the template search path), the include directive would look for the included file at "<tt class="docutils literal">myapp/base.txt</tt>". You can also use Unix-style relative paths, for example "<tt class="docutils literal"><span class="pre">../base.txt</span></tt>" to look in the parent directory.</p> <p>Just like other directives, the argument to the <tt class="docutils literal">include</tt> directive accepts any Python expression, so the path to the included template can be determined dynamically:</p> <div class="highlight"><pre><span class="x">{% include </span><span class="cp">${</span><span class="s">'</span><span class="si">%s</span><span class="s">.txt'</span> <span class="o">%</span> <span class="n">filename</span><span class="cp">}</span><span class="x"> %}</span> </pre></div> <p>Note that a <tt class="docutils literal">TemplateNotFound</tt> exception is raised if an included file can't be found.</p> <div class="note"> <p class="first admonition-title">Note</p> <p class="last">The include directive for text templates was added in Genshi 0.5.</p> </div> </div> </div> <div class="section" id="variable-binding"> <h2>1.4 Variable Binding</h2> <div class="section" id="id6"> <span id="with"></span><h3>1.4.1 <tt class="docutils literal">{% with %}</tt></h3> <p>The <tt class="docutils literal">{% with %}</tt> directive lets you assign expressions to variables, which can be used to make expressions inside the directive less verbose and more efficient. For example, if you need use the expression <tt class="docutils literal">author.posts</tt> more than once, and that actually results in a database query, assigning the results to a variable using this directive would probably help.</p> <p>For example:</p> <div class="highlight"><pre><span class="x">Magic numbers!</span> <span class="x">{% with y=7; z=x+10 %}</span> <span class="x"> </span><span class="nv">$x</span><span class="x"> </span><span class="nv">$y</span><span class="x"> </span><span class="nv">$z</span><span class="x"></span> <span class="x">{% end %}</span> </pre></div> <p>Given <tt class="docutils literal">x=42</tt> in the context data, this would produce:</p> <pre class="literal-block"> Magic numbers! 42 7 52 </pre> <p>Note that if a variable of the same name already existed outside of the scope of the <tt class="docutils literal">with</tt> directive, it will <strong>not</strong> be overwritten. Instead, it will have the same value it had prior to the <tt class="docutils literal">with</tt> assignment. Effectively, this means that variables are immutable in Genshi.</p> </div> </div> </div> <div class="section" id="white-space-and-line-breaks"> <span id="whitespace"></span><h1>2 White-space and Line Breaks</h1> <p>Note that space or line breaks around directives is never automatically removed. Consider the following example:</p> <div class="highlight"><pre><span class="x">{% for item in items %}</span> <span class="x"> {% if item.visible %}</span> <span class="x"> </span><span class="cp">${</span><span class="n">item</span><span class="cp">}</span><span class="x"></span> <span class="x"> {% end %}</span> <span class="x">{% end %}</span> </pre></div> <p>This will result in two empty lines above and beneath every item, plus the spaces used for indentation. If you want to supress a line break, simply end the line with a backslash:</p> <div class="highlight"><pre><span class="x">{% for item in items %}\</span> <span class="x"> {% if item.visible %}\</span> <span class="x"> </span><span class="cp">${</span><span class="n">item</span><span class="cp">}</span><span class="x"></span> <span class="x"> {% end %}\</span> <span class="x">{% end %}\</span> </pre></div> <p>Now there would be no empty lines between the items in the output. But you still get the spaces used for indentation, and because the line breaks are removed, they actually continue and add up between lines. There are numerous ways to control white-space in the output while keeping the template readable, such as moving the indentation into the delimiters, or moving the end delimiter on the next line, and so on.</p> </div> <div class="section" id="id7"> <span id="comments"></span><h1>3 Comments</h1> <p>Parts in templates can be commented out using the delimiters <tt class="docutils literal">{# ... #}</tt>. Any content in comments are removed from the output.</p> <div class="highlight"><pre><span class="x">{# This won't end up in the output #}</span> <span class="x">This will.</span> </pre></div> <p>Just like directive delimiters, these can be escaped by prefixing with a backslash.</p> <div class="highlight"><pre><span class="x">\{# This *will* end up in the output, including delimiters #}</span> <span class="x">This too.</span> </pre></div> </div> <div class="section" id="legacy-text-template-syntax"> <span id="legacy"></span><h1>4 Legacy Text Template Syntax</h1> <p>The syntax for text templates was redesigned in version 0.5 of Genshi to make the language more flexible and powerful. The older syntax is based on line starting with dollar signs, similar to e.g. <a class="reference external" href="http://cheetahtemplate.org/">Cheetah</a> or <a class="reference external" href="http://jakarta.apache.org/velocity/">Velocity</a>.</p> <p>A simple template using the old syntax looked like this:</p> <div class="highlight"><pre><span class="x">Dear </span><span class="nv">$name</span><span class="x">,</span> <span class="x">We have the following items for you:</span> <span class="cp">#</span><span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">items</span><span class="x"></span> <span class="x"> * </span><span class="nv">$item</span><span class="x"></span> <span class="cp">#</span><span class="k">end</span><span class="x"></span> <span class="x">All the best,</span> <span class="x">Foobar</span> </pre></div> <p>Beyond the requirement of putting directives on separate lines prefixed with dollar signs, the language itself is very similar to the new one. Except that comments are lines that start with two <tt class="docutils literal">#</tt> characters, and a line-break at the end of a directive is removed automatically.</p> <div class="note"> <p class="first admonition-title">Note</p> <p class="last">If you're using this old syntax, it is strongly recommended to migrate to the new syntax. Simply replace any references to <tt class="docutils literal">TextTemplate</tt> by <tt class="docutils literal">NewTextTemplate</tt> (and also change the text templates, of course). On the other hand, if you want to stick with the old syntax for a while longer, replace references to <tt class="docutils literal">TextTemplate</tt> by <tt class="docutils literal">OldTextTemplate</tt>; while <tt class="docutils literal">TextTemplate</tt> is still an alias for the old language at this point, that will change in a future release. But also note that the old syntax may be dropped entirely in a future release.</p> </div> </div> <div id="footer"> Visit the Genshi open source project at <a href="http://genshi.edgewall.org/">http://genshi.edgewall.org/</a> </div> </div> </body> </html>