<!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 XML Template Language</title> <link rel="stylesheet" href="common/style/edgewall.css" type="text/css"> </head> <body> <div class="document" id="genshi-xml-template-language"> <div id="navigation"> <span class="projinfo">Genshi 0.7</span> <a href="index.html">Documentation Index</a> </div> <h1 class="title">Genshi XML Template Language</h1> <p>Genshi provides a XML-based template language that is heavily inspired by <a class="reference external" href="http://kid-templating.org/">Kid</a>, which in turn was inspired by a number of existing template languages, namely <a class="reference external" href="http://www.w3.org/TR/xslt">XSLT</a>, <a class="reference external" href="http://www.zope.org/Wikis/DevSite/Projects/ZPT/TAL">TAL</a>, and <a class="reference external" href="http://www.php.net/">PHP</a>.</p> <p>This document describes the template language and will be most useful as reference to those developing Genshi XML templates. Templates are XML files of some kind (such as XHTML) that include processing <a class="reference internal" href="#directives">directives</a> (elements or attributes identified by a separate namespace) 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="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="id12">1 Template Directives</a><ul class="auto-toc"> <li><a class="reference internal" href="#conditional-sections" id="id13">1.1 Conditional Sections</a><ul class="auto-toc"> <li><a class="reference internal" href="#id1" id="id14">1.1.1 <tt class="docutils literal">py:if</tt></a></li> <li><a class="reference internal" href="#id2" id="id15">1.1.2 <tt class="docutils literal">py:choose</tt></a></li> </ul> </li> <li><a class="reference internal" href="#looping" id="id16">1.2 Looping</a><ul class="auto-toc"> <li><a class="reference internal" href="#id3" id="id17">1.2.1 <tt class="docutils literal">py:for</tt></a></li> </ul> </li> <li><a class="reference internal" href="#snippet-reuse" id="id18">1.3 Snippet Reuse</a><ul class="auto-toc"> <li><a class="reference internal" href="#id4" id="id19">1.3.1 <tt class="docutils literal">py:def</tt></a></li> <li><a class="reference internal" href="#id5" id="id20">1.3.2 <tt class="docutils literal">py:match</tt></a></li> </ul> </li> <li><a class="reference internal" href="#variable-binding" id="id21">1.4 Variable Binding</a><ul class="auto-toc"> <li><a class="reference internal" href="#py-with" id="id22">1.4.1 <tt class="docutils literal">py:with</tt></a></li> </ul> </li> <li><a class="reference internal" href="#structure-manipulation" id="id23">1.5 Structure Manipulation</a><ul class="auto-toc"> <li><a class="reference internal" href="#id6" id="id24">1.5.1 <tt class="docutils literal">py:attrs</tt></a></li> <li><a class="reference internal" href="#id7" id="id25">1.5.2 <tt class="docutils literal">py:content</tt></a></li> <li><a class="reference internal" href="#id8" id="id26">1.5.3 <tt class="docutils literal">py:replace</tt></a></li> <li><a class="reference internal" href="#id9" id="id27">1.5.4 <tt class="docutils literal">py:strip</tt></a></li> </ul> </li> <li><a class="reference internal" href="#processing-order" id="id28">1.6 Processing Order</a></li> </ul> </li> <li><a class="reference internal" href="#id10" id="id29">2 Includes</a><ul class="auto-toc"> <li><a class="reference internal" href="#dynamic-includes" id="id30">2.1 Dynamic Includes</a></li> <li><a class="reference internal" href="#including-text-templates" id="id31">2.2 Including Text Templates</a></li> </ul> </li> <li><a class="reference internal" href="#id11" id="id32">3 Comments</a></li> </ul> </div> <div class="section" id="template-directives"> <span id="directives"></span><h1>1 Template Directives</h1> <p>Directives are elements and/or attributes in the template that are identified by the namespace <tt class="docutils literal"><span class="pre">http://genshi.edgewall.org/</span></tt>. They can affect how the template is rendered in a number of ways: Genshi provides directives for conditionals and looping, among others.</p> <p>To use directives in a template, the namespace must be declared, which is usually done on the root element:</p> <div class="highlight"><pre><span class="nt"><html</span> <span class="na">xmlns=</span><span class="s">"http://www.w3.org/1999/xhtml"</span> <span class="na">xmlns:py=</span><span class="s">"http://genshi.edgewall.org/"</span> <span class="na">lang=</span><span class="s">"en"</span><span class="nt">></span> ... <span class="nt"></html></span> </pre></div> <p>In this example, the default namespace is set to the XHTML namespace, and the namespace for Genshi directives is bound to the prefix “py”.</p> <p>All directives can be applied as attributes, and some can also be used as elements. The <tt class="docutils literal">if</tt> directives for conditionals, for example, can be used in both ways:</p> <div class="highlight"><pre><span class="nt"><html</span> <span class="na">xmlns=</span><span class="s">"http://www.w3.org/1999/xhtml"</span> <span class="na">xmlns:py=</span><span class="s">"http://genshi.edgewall.org/"</span> <span class="na">lang=</span><span class="s">"en"</span><span class="nt">></span> ... <span class="nt"><div</span> <span class="na">py:if=</span><span class="s">"</span><span class="n">foo</span><span class="s">"</span><span class="nt">></span> <span class="nt"><p></span>Bar<span class="nt"></p></span> <span class="nt"></div></span> ... <span class="nt"></html></span> </pre></div> <p>This is basically equivalent to the following:</p> <div class="highlight"><pre><span class="nt"><html</span> <span class="na">xmlns=</span><span class="s">"http://www.w3.org/1999/xhtml"</span> <span class="na">xmlns:py=</span><span class="s">"http://genshi.edgewall.org/"</span> <span class="na">lang=</span><span class="s">"en"</span><span class="nt">></span> ... <span class="nt"><py:if</span> <span class="na">test=</span><span class="s">"</span><span class="n">foo</span><span class="s">"</span><span class="nt">></span> <span class="nt"><div></span> <span class="nt"><p></span>Bar<span class="nt"></p></span> <span class="nt"></div></span> <span class="nt"></py:if></span> ... <span class="nt"></html></span> </pre></div> <p>The rationale behind the second form is that directives do not always map naturally to elements in the template. In such cases, the <tt class="docutils literal">py:strip</tt> directive can be used to strip off the unwanted element, or the directive can simply be used as an element.</p> <div class="section" id="conditional-sections"> <h2>1.1 Conditional Sections</h2> <div class="section" id="id1"> <span id="py-if"></span><h3>1.1.1 <tt class="docutils literal">py:if</tt></h3> <p>The element and its content is only rendered if the expression evaluates to a truth value:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><b</span> <span class="na">py:if=</span><span class="s">"</span><span class="n">foo</span><span class="s">"</span><span class="nt">></span><span class="cp">${</span><span class="n">bar</span><span class="cp">}</span><span class="nt"></b></span> <span class="nt"></div></span> </pre></div> <p>Given the data <tt class="docutils literal">foo=True</tt> and <tt class="docutils literal"><span class="pre">bar='Hello'</span></tt> in the template context, this would produce:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><b></span>Hello<span class="nt"></b></span> <span class="nt"></div></span> </pre></div> <p>But setting <tt class="docutils literal">foo=False</tt> would result in the following output:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"></div></span> </pre></div> <p>This directive can also be used as an element:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><py:if</span> <span class="na">test=</span><span class="s">"</span><span class="n">foo</span><span class="s">"</span><span class="nt">></span> <span class="nt"><b></span><span class="cp">${</span><span class="n">bar</span><span class="cp">}</span><span class="nt"></b></span> <span class="nt"></py:if></span> <span class="nt"></div></span> </pre></div> </div> <div class="section" id="id2"> <span id="py-otherwise"></span><span id="py-when"></span><span id="py-choose"></span><h3>1.1.2 <tt class="docutils literal">py:choose</tt></h3> <p>The <tt class="docutils literal">py:choose</tt> directive, in combination with the directives <tt class="docutils literal">py:when</tt> and <tt class="docutils literal">py:otherwise</tt> provides advanced conditional processing for rendering one of several alternatives. The first matching <tt class="docutils literal">py:when</tt> branch is rendered, or, if no <tt class="docutils literal">py:when</tt> branch matches, the <tt class="docutils literal">py:otherwise</tt> branch is rendered.</p> <p>If the <tt class="docutils literal">py:choose</tt> directive is empty the nested <tt class="docutils literal">py:when</tt> directives will be tested for truth:</p> <div class="highlight"><pre><span class="nt"><div</span> <span class="na">py:choose=</span><span class="s">""</span><span class="nt">></span> <span class="nt"><span</span> <span class="na">py:when=</span><span class="s">"</span><span class="mi">0</span> <span class="o">==</span> <span class="mi">1</span><span class="s">"</span><span class="nt">></span>0<span class="nt"></span></span> <span class="nt"><span</span> <span class="na">py:when=</span><span class="s">"</span><span class="mi">1</span> <span class="o">==</span> <span class="mi">1</span><span class="s">"</span><span class="nt">></span>1<span class="nt"></span></span> <span class="nt"><span</span> <span class="na">py:otherwise=</span><span class="s">""</span><span class="nt">></span>2<span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>This would produce the following output:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><span></span>1<span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>If the <tt class="docutils literal">py:choose</tt> directive contains an expression the nested <tt class="docutils literal">py:when</tt> directives will be tested for equality to the parent <tt class="docutils literal">py:choose</tt> value:</p> <div class="highlight"><pre><span class="nt"><div</span> <span class="na">py:choose=</span><span class="s">"</span><span class="mi">1</span><span class="s">"</span><span class="nt">></span> <span class="nt"><span</span> <span class="na">py:when=</span><span class="s">"</span><span class="mi">0</span><span class="s">"</span><span class="nt">></span>0<span class="nt"></span></span> <span class="nt"><span</span> <span class="na">py:when=</span><span class="s">"</span><span class="mi">1</span><span class="s">"</span><span class="nt">></span>1<span class="nt"></span></span> <span class="nt"><span</span> <span class="na">py:otherwise=</span><span class="s">""</span><span class="nt">></span>2<span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>This would produce the following output:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><span></span>1<span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>These directives can also be used as elements:</p> <div class="highlight"><pre><span class="nt"><py:choose</span> <span class="na">test=</span><span class="s">"</span><span class="mi">1</span><span class="s">"</span><span class="nt">></span> <span class="nt"><py:when</span> <span class="na">test=</span><span class="s">"</span><span class="mi">0</span><span class="s">"</span><span class="nt">></span>0<span class="nt"></py:when></span> <span class="nt"><py:when</span> <span class="na">test=</span><span class="s">"</span><span class="mi">1</span><span class="s">"</span><span class="nt">></span>1<span class="nt"></py:when></span> <span class="nt"><py:otherwise></span>2<span class="nt"></py:otherwise></span> <span class="nt"></py:choose></span> </pre></div> </div> </div> <div class="section" id="looping"> <h2>1.2 Looping</h2> <div class="section" id="id3"> <span id="py-for"></span><h3>1.2.1 <tt class="docutils literal">py:for</tt></h3> <p>The element is repeated for every item in an iterable:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><li</span> <span class="na">py:for=</span><span class="s">"</span><span class="n">item</span> <span class="ow">in</span> <span class="n">items</span><span class="s">"</span><span class="nt">></span><span class="cp">${</span><span class="n">item</span><span class="cp">}</span><span class="nt"></li></span> <span class="nt"></ul></span> </pre></div> <p>Given <tt class="docutils literal"><span class="pre">items=[1,</span> 2, 3]</tt> in the context data, this would produce:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><li></span>1<span class="nt"></li><li></span>2<span class="nt"></li><li></span>3<span class="nt"></li></span> <span class="nt"></ul></span> </pre></div> <p>This directive can also be used as an element:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><py:for</span> <span class="na">each=</span><span class="s">"</span><span class="n">item</span> <span class="ow">in</span> <span class="n">items</span><span class="s">"</span><span class="nt">></span> <span class="nt"><li></span><span class="cp">${</span><span class="n">item</span><span class="cp">}</span><span class="nt"></li></span> <span class="nt"></py:for></span> <span class="nt"></ul></span> </pre></div> </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="py-def"></span><h3>1.3.1 <tt class="docutils literal">py:def</tt></h3> <p>The <tt class="docutils literal">py:def</tt> directive can be used to create macros, i.e. snippets of template code that have a name and optionally some parameters, and that can be inserted in other places:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><p</span> <span class="na">py:def=</span><span class="s">"</span><span class="n">greeting</span><span class="p">(</span><span class="n">name</span><span class="p">)</span><span class="s">"</span> <span class="na">class=</span><span class="s">"greeting"</span><span class="nt">></span> Hello, <span class="cp">${</span><span class="n">name</span><span class="cp">}</span>! <span class="nt"></p></span> <span class="cp">${</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="cp">${</span><span class="n">greeting</span><span class="p">(</span><span class="s">'everyone else'</span><span class="p">)</span><span class="cp">}</span> <span class="nt"></div></span> </pre></div> <p>The above would be rendered to:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><p</span> <span class="na">class=</span><span class="s">"greeting"</span><span class="nt">></span> Hello, world! <span class="nt"></p></span> <span class="nt"><p</span> <span class="na">class=</span><span class="s">"greeting"</span><span class="nt">></span> Hello, everyone else! <span class="nt"></p></span> <span class="nt"></div></span> </pre></div> <p>If a macro doesn't require parameters, it can be defined without the parenthesis. For example:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><p</span> <span class="na">py:def=</span><span class="s">"</span><span class="n">greeting</span><span class="s">"</span> <span class="na">class=</span><span class="s">"greeting"</span><span class="nt">></span> Hello, world! <span class="nt"></p></span> <span class="cp">${</span><span class="n">greeting</span><span class="p">()</span><span class="cp">}</span> <span class="nt"></div></span> </pre></div> <p>The above would be rendered to:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><p</span> <span class="na">class=</span><span class="s">"greeting"</span><span class="nt">></span> Hello, world! <span class="nt"></p></span> <span class="nt"></div></span> </pre></div> <p>This directive can also be used as an element:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><py:def</span> <span class="na">function=</span><span class="s">"</span><span class="n">greeting</span><span class="p">(</span><span class="n">name</span><span class="p">)</span><span class="s">"</span><span class="nt">></span> <span class="nt"><p</span> <span class="na">class=</span><span class="s">"greeting"</span><span class="nt">></span>Hello, <span class="cp">${</span><span class="n">name</span><span class="cp">}</span>!<span class="nt"></p></span> <span class="nt"></py:def></span> <span class="nt"></div></span> </pre></div> </div> <div class="section" id="id5"> <span id="py-match"></span><span id="match-templates"></span><h3>1.3.2 <tt class="docutils literal">py:match</tt></h3> <p>This directive defines a <em>match template</em>: given an XPath expression, it replaces any element in the template that matches the expression with its own content.</p> <p>For example, the match template defined in the following template matches any element with the tag name “greeting”:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><span</span> <span class="na">py:match=</span><span class="s">"</span><span class="n">greeting</span><span class="s">"</span><span class="nt">></span> Hello <span class="cp">${</span><span class="n">select</span><span class="p">(</span><span class="s">'@name'</span><span class="p">)</span><span class="cp">}</span> <span class="nt"></span></span> <span class="nt"><greeting</span> <span class="na">name=</span><span class="s">"Dude"</span> <span class="nt">/></span> <span class="nt"></div></span> </pre></div> <p>This would result in the following output:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><span></span> Hello Dude <span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>Inside the body of a <tt class="docutils literal">py:match</tt> directive, the <tt class="docutils literal">select(path)</tt> function is made available so that parts or all of the original element can be incorporated in the output of the match template. See <a class="reference external" href="streams.html#using-xpath">Using XPath</a> for more information about this function.</p> <p>Match templates are applied both to the original markup as well to the generated markup. The order in which they are applied depends on the order they are declared in the template source: a match template defined after another match template is applied to the output generated by the first match template. The match templates basically form a pipeline.</p> <p>This directive can also be used as an element:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><py:match</span> <span class="na">path=</span><span class="s">"</span><span class="n">greeting</span><span class="s">"</span><span class="nt">></span> <span class="nt"><span></span>Hello <span class="cp">${</span><span class="n">select</span><span class="p">(</span><span class="s">'@name'</span><span class="p">)</span><span class="cp">}</span><span class="nt"></span></span> <span class="nt"></py:match></span> <span class="nt"><greeting</span> <span class="na">name=</span><span class="s">"Dude"</span> <span class="nt">/></span> <span class="nt"></div></span> </pre></div> <p>When used this way, the <tt class="docutils literal">py:match</tt> directive can also be annotated with a couple of optimization hints. For example, the following informs the matching engine that the match should only be applied once:</p> <div class="highlight"><pre><span class="nt"><py:match</span> <span class="na">path=</span><span class="s">"</span><span class="n">body</span><span class="s">"</span> <span class="na">once=</span><span class="s">"</span><span class="n">true</span><span class="s">"</span><span class="nt">></span> <span class="nt"><body</span> <span class="na">py:attrs=</span><span class="s">"</span><span class="n">select</span><span class="p">(</span><span class="s">'@*'</span><span class="p">)</span><span class="s">"</span><span class="nt">></span> <span class="nt"><div</span> <span class="na">id=</span><span class="s">"header"</span><span class="nt">></span>...<span class="nt"></div></span> <span class="cp">${</span><span class="n">select</span><span class="p">(</span><span class="s">"*|text()"</span><span class="p">)</span><span class="cp">}</span> <span class="nt"><div</span> <span class="na">id=</span><span class="s">"footer"</span><span class="nt">></span>...<span class="nt"></div></span> <span class="nt"></body></span> <span class="nt"></py:match></span> </pre></div> <p>The following optimization hints are recognized:</p> <table border="1" class="docutils"> <colgroup> <col width="21%"> <col width="15%"> <col width="64%"> </colgroup> <thead valign="bottom"> <tr><th class="head">Attribute</th> <th class="head">Default</th> <th class="head">Description</th> </tr> </thead> <tbody valign="top"> <tr><td><tt class="docutils literal">buffer</tt></td> <td><tt class="docutils literal">true</tt></td> <td>Whether the matched content should be buffered in memory. Buffering can improve performance a bit at the cost of needing more memory during rendering. Buffering is ''required'' for match templates that contain more than one invocation of the <tt class="docutils literal">select()</tt> function. If there is only one call, and the matched content can potentially be very long, consider disabling buffering to avoid excessive memory use.</td> </tr> <tr><td><tt class="docutils literal">once</tt></td> <td><tt class="docutils literal">false</tt></td> <td>Whether the engine should stop looking for more matching elements after the first match. Use this on match templates that match elements that can only occur once in the stream, such as the <tt class="docutils literal"><head></tt> or <tt class="docutils literal"><body></tt> elements in an HTML template, or elements with a specific ID.</td> </tr> <tr><td><tt class="docutils literal">recursive</tt></td> <td><tt class="docutils literal">true</tt></td> <td>Whether the match template should be applied to its own output. Note that <tt class="docutils literal">once</tt> implies non-recursive behavior, so this attribute only needs to be set for match templates that don't also have <tt class="docutils literal">once</tt> set.</td> </tr> </tbody> </table> <div class="note"> <p class="first admonition-title">Note</p> <p class="last">The <tt class="docutils literal">py:match</tt> optimization hints were added in the 0.5 release. In earlier versions, the attributes have no effect.</p> </div> </div> </div> <div class="section" id="variable-binding"> <h2>1.4 Variable Binding</h2> <div class="section" id="py-with"> <span id="with"></span><h3>1.4.1 <tt class="docutils literal">py:with</tt></h3> <p>The <tt class="docutils literal">py: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="nt"><div></span> <span class="nt"><span</span> <span class="na">py:with=</span><span class="s">"</span><span class="n">y</span><span class="o">=</span><span class="mi">7</span><span class="p">;</span> <span class="n">z</span><span class="o">=</span><span class="n">x</span><span class="o">+</span><span class="mi">10</span><span class="s">"</span><span class="nt">></span><span class="nv">$x</span> <span class="nv">$y</span> <span class="nv">$z</span><span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>Given <tt class="docutils literal">x=42</tt> in the context data, this would produce:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><span></span>42 7 52<span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>This directive can also be used as an element:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><py:with</span> <span class="na">vars=</span><span class="s">"</span><span class="n">y</span><span class="o">=</span><span class="mi">7</span><span class="p">;</span> <span class="n">z</span><span class="o">=</span><span class="n">x</span><span class="o">+</span><span class="mi">10</span><span class="s">"</span><span class="nt">></span><span class="nv">$x</span> <span class="nv">$y</span> <span class="nv">$z</span><span class="nt"></py:with></span> <span class="nt"></div></span> </pre></div> <p>Note that if a variable of the same name already existed outside of the scope of the <tt class="docutils literal">py: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">py:with</tt> assignment. Effectively, this means that variables are immutable in Genshi.</p> </div> </div> <div class="section" id="structure-manipulation"> <h2>1.5 Structure Manipulation</h2> <div class="section" id="id6"> <span id="py-attrs"></span><h3>1.5.1 <tt class="docutils literal">py:attrs</tt></h3> <p>This directive adds, modifies or removes attributes from the element:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><li</span> <span class="na">py:attrs=</span><span class="s">"</span><span class="n">foo</span><span class="s">"</span><span class="nt">></span>Bar<span class="nt"></li></span> <span class="nt"></ul></span> </pre></div> <p>Given <tt class="docutils literal"><span class="pre">foo={'class':</span> 'collapse'}</tt> in the template context, this would produce:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><li</span> <span class="na">class=</span><span class="s">"collapse"</span><span class="nt">></span>Bar<span class="nt"></li></span> <span class="nt"></ul></span> </pre></div> <p>Attributes with the value <tt class="docutils literal">None</tt> are omitted, so given <tt class="docutils literal"><span class="pre">foo={'class':</span> None}</tt> in the context for the same template this would produce:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><li></span>Bar<span class="nt"></li></span> <span class="nt"></ul></span> </pre></div> <p>This directive can only be used as an attribute.</p> </div> <div class="section" id="id7"> <span id="py-content"></span><h3>1.5.2 <tt class="docutils literal">py:content</tt></h3> <p>This directive replaces any nested content with the result of evaluating the expression:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><li</span> <span class="na">py:content=</span><span class="s">"</span><span class="n">bar</span><span class="s">"</span><span class="nt">></span>Hello<span class="nt"></li></span> <span class="nt"></ul></span> </pre></div> <p>Given <tt class="docutils literal"><span class="pre">bar='Bye'</span></tt> in the context data, this would produce:</p> <div class="highlight"><pre><span class="nt"><ul></span> <span class="nt"><li></span>Bye<span class="nt"></li></span> <span class="nt"></ul></span> </pre></div> <p>This directive can only be used as an attribute.</p> </div> <div class="section" id="id8"> <span id="py-replace"></span><h3>1.5.3 <tt class="docutils literal">py:replace</tt></h3> <p>This directive replaces the element itself with the result of evaluating the expression:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><span</span> <span class="na">py:replace=</span><span class="s">"</span><span class="n">bar</span><span class="s">"</span><span class="nt">></span>Hello<span class="nt"></span></span> <span class="nt"></div></span> </pre></div> <p>Given <tt class="docutils literal"><span class="pre">bar='Bye'</span></tt> in the context data, this would produce:</p> <div class="highlight"><pre><span class="nt"><div></span> Bye <span class="nt"></div></span> </pre></div> <p>This directive can also be used as an element (since version 0.5):</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><py:replace</span> <span class="na">value=</span><span class="s">"</span><span class="n">title</span><span class="s">"</span><span class="nt">></span>Placeholder<span class="nt"></py:replace></span> <span class="nt"></div></span> </pre></div> </div> <div class="section" id="id9"> <span id="py-strip"></span><h3>1.5.4 <tt class="docutils literal">py:strip</tt></h3> <p>This directive conditionally strips the top-level element from the output. When the value of the <tt class="docutils literal">py:strip</tt> attribute evaluates to <tt class="docutils literal">True</tt>, the element is stripped from the output:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><div</span> <span class="na">py:strip=</span><span class="s">"</span><span class="bp">True</span><span class="s">"</span><span class="nt">><b></span>foo<span class="nt"></b></div></span> <span class="nt"></div></span> </pre></div> <p>This would be rendered as:</p> <div class="highlight"><pre><span class="nt"><div></span> <span class="nt"><b></span>foo<span class="nt"></b></span> <span class="nt"></div></span> </pre></div> <p>As a shorthand, if the value of the <tt class="docutils literal">py:strip</tt> attribute is empty, that has the same effect as using a truth value (i.e. the element is stripped).</p> </div> </div> <div class="section" id="processing-order"> <span id="order"></span><h2>1.6 Processing Order</h2> <p>It is possible to attach multiple directives to a single element, although not all combinations make sense. When multiple directives are encountered, they are processed in the following order:</p> <ol class="arabic simple"> <li><a class="reference internal" href="#py-def">py:def</a></li> <li><a class="reference internal" href="#py-match">py:match</a></li> <li><a class="reference internal" href="#py-when">py:when</a></li> <li><a class="reference internal" href="#py-otherwise">py:otherwise</a></li> <li><a class="reference internal" href="#py-for">py:for</a></li> <li><a class="reference internal" href="#py-if">py:if</a></li> <li><a class="reference internal" href="#py-choose">py:choose</a></li> <li><a class="reference internal" href="#py-with">py:with</a></li> <li><a class="reference internal" href="#py-replace">py:replace</a></li> <li><a class="reference internal" href="#py-content">py:content</a></li> <li><a class="reference internal" href="#py-attrs">py:attrs</a></li> <li><a class="reference internal" href="#py-strip">py:strip</a></li> </ol> </div> </div> <div class="section" id="id10"> <span id="includes"></span><h1>2 Includes</h1> <p>To reuse common snippets of template code, you can include other files using <a class="reference external" href="http://www.w3.org/TR/xinclude/">XInclude</a>.</p> <p>For this, you need to declare the XInclude namespace (commonly bound to the prefix “xi”) and use the <tt class="docutils literal"><xi:include></tt> element where you want the external file to be pulled in:</p> <div class="highlight"><pre><span class="nt"><html</span> <span class="na">xmlns=</span><span class="s">"http://www.w3.org/1999/xhtml"</span> <span class="na">xmlns:py=</span><span class="s">"http://genshi.edgewall.org/"</span> <span class="na">xmlns:xi=</span><span class="s">"http://www.w3.org/2001/XInclude"</span><span class="nt">></span> <span class="nt"><xi:include</span> <span class="na">href=</span><span class="s">"base.html"</span> <span class="nt">/></span> ... <span class="nt"></html></span> </pre></div> <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/index.html</tt>" (relative to the template search path), the XInclude processor would look for the included file at "<tt class="docutils literal">myapp/base.html</tt>". You can also use Unix-style relative paths, for example "<tt class="docutils literal"><span class="pre">../base.html</span></tt>" to look in the parent directory.</p> <p>Any content included this way is inserted into the generated output instead of the <tt class="docutils literal"><xi:include></tt> element. The included template sees the same context data. <a class="reference internal" href="#match-templates">Match templates</a> and <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>By default, an error will be raised if an included file is not found. If that's not what you want, you can specify fallback content that should be used if the include fails. For example, to to make the include above fail silently, you'd write:</p> <div class="highlight"><pre><span class="nt"><xi:include</span> <span class="na">href=</span><span class="s">"base.html"</span><span class="nt">><xi:fallback</span> <span class="nt">/></xi:include></span> </pre></div> <p>See the <a class="reference external" href="http://www.w3.org/TR/xinclude/">XInclude specification</a> for more about fallback content. Note though that Genshi currently only supports a small subset of XInclude.</p> <div class="section" id="dynamic-includes"> <h2>2.1 Dynamic Includes</h2> <p>Incudes in Genshi are fully dynamic: Just like normal attributes, the <cite>href</cite> attribute accepts expressions, and <a class="reference internal" href="#directives">directives</a> can be used on the <tt class="docutils literal"><xi:include /></tt> element just as on any other element, meaning you can do things like conditional includes:</p> <div class="highlight"><pre><span class="nt"><xi:include</span> <span class="na">href=</span><span class="s">"</span><span class="cp">${</span><span class="n">name</span><span class="cp">}</span><span class="s">.html"</span> <span class="na">py:if=</span><span class="s">"</span><span class="ow">not</span> <span class="n">in_popup</span><span class="s">"</span> <span class="na">py:for=</span><span class="s">"</span><span class="n">name</span> <span class="ow">in</span> <span class="p">(</span><span class="s">'foo'</span><span class="p">,</span> <span class="s">'bar'</span><span class="p">,</span> <span class="s">'baz'</span><span class="p">)</span><span class="s">"</span> <span class="nt">/></span> </pre></div> </div> <div class="section" id="including-text-templates"> <h2>2.2 Including Text Templates</h2> <p>The <tt class="docutils literal">parse</tt> attribute of the <tt class="docutils literal"><xi:include></tt> element can be used to specify whether the included template is an XML template or a text template (using the new syntax added in Genshi 0.5):</p> <div class="highlight"><pre><span class="nt"><xi:include</span> <span class="na">href=</span><span class="s">"myscript.js"</span> <span class="na">parse=</span><span class="s">"text"</span> <span class="nt">/></span> </pre></div> <p>This example would load the <tt class="docutils literal">myscript.js</tt> file as a <tt class="docutils literal">NewTextTemplate</tt>. See <a class="reference external" href="text-templates.html">text templates</a> for details on the syntax of text templates.</p> </div> </div> <div class="section" id="id11"> <span id="comments"></span><h1>3 Comments</h1> <p>Normal XML/HTML comment syntax can be used in templates:</p> <div class="highlight"><pre><span class="c"><!-- this is a comment --></span> </pre></div> <p>However, such comments get passed through the processing pipeline and are by default included in the final output. If that's not desired, prefix the comment text with an exclamation mark:</p> <div class="highlight"><pre><span class="c"><!-- !this is a comment too, but one that will be stripped from the output --></span> </pre></div> <p>Note that it does not matter whether there's whitespace before or after the exclamation mark, so the above could also be written as follows:</p> <div class="highlight"><pre><span class="c"><!--! this is a comment too, but one that will be stripped from the output --></span> </pre></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>