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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title> Defs and Blocks — Mako 1.1.0 Documentation </title> <!-- begin iterate through site-imported + sphinx environment css_files --> <link rel="stylesheet" href="_static/pygments.css" type="text/css" /> <link rel="stylesheet" href="_static/changelog.css" type="text/css" /> <link rel="stylesheet" href="_static/sphinx_paramlinks.css" type="text/css" /> <link rel="stylesheet" href="_static/docs.css" type="text/css" /> <!-- end iterate through site-imported + sphinx environment css_files --> <!-- begin layout.mako headers --> <link rel="index" title="Index" href="genindex.html" /> <link rel="search" title="Search" href="search.html" /> <link rel="top" title="Mako 1.1.0 Documentation" href="index.html" /> <link rel="next" title="The Mako Runtime Environment" href="runtime.html" /> <link rel="prev" title="Syntax" href="syntax.html" /> <!-- end layout.mako headers --> </head> <body> <div id="docs-container"> <div id="docs-header"> <h1>Mako 1.1.0 Documentation</h1> <div id="docs-search"> Search: <form class="search" action="search.html" method="get"> <input type="text" name="q" size="18" /> <input type="submit" value="Search" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> <div id="docs-version-header"> Release: <span class="version-num">1.1.0</span> </div> </div> <div id="docs-top-navigation"> <div id="docs-top-page-control" class="docs-navigation-links"> <ul> <li>Prev: <a href="syntax.html" title="previous chapter">Syntax</a> </li> <li>Next: <a href="runtime.html" title="next chapter">The Mako Runtime Environment</a> </li> <li> <a href="index.html">Table of Contents</a> | <a href="genindex.html">Index</a> </li> </ul> </div> <div id="docs-navigation-banner"> <a href="index.html">Mako 1.1.0 Documentation</a> » Defs and Blocks <h2> Defs and Blocks </h2> </div> </div> <div id="docs-body-container"> <div id="docs-sidebar"> <div id="sidebar-banner"> </div> <h3><a href="index.html">Table of Contents</a></h3> <ul> <li><a class="reference internal" href="#">Defs and Blocks</a><ul> <li><a class="reference internal" href="#using-defs">Using Defs</a><ul> <li><a class="reference internal" href="#calling-defs-from-other-files">Calling Defs from Other Files</a></li> <li><a class="reference internal" href="#calling-defs-programmatically">Calling Defs Programmatically</a></li> <li><a class="reference internal" href="#defs-within-defs">Defs within Defs</a></li> <li><a class="reference internal" href="#calling-a-def-with-embedded-content-and-or-other-defs">Calling a Def with Embedded Content and/or Other Defs</a></li> </ul> </li> <li><a class="reference internal" href="#using-blocks">Using Blocks</a><ul> <li><a class="reference internal" href="#using-named-blocks">Using Named Blocks</a></li> <li><a class="reference internal" href="#using-page-arguments-in-named-blocks">Using Page Arguments in Named Blocks</a></li> </ul> </li> </ul> </li> </ul> <h4>Previous Topic</h4> <p> <a href="syntax.html" title="previous chapter">Syntax</a> </p> <h4>Next Topic</h4> <p> <a href="runtime.html" title="next chapter">The Mako Runtime Environment</a> </p> <h4>Quick Search</h4> <p> <form class="search" action="search.html" method="get"> <input type="text" name="q" size="18" /> <input type="submit" value="Search" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </p> </div> <div id="docs-body" class="withsidebar" > <div class="section" id="defs-and-blocks"> <span id="defs-toplevel"></span><h1>Defs and Blocks<a class="headerlink" href="#defs-and-blocks" title="Permalink to this headline">¶</a></h1> <p><code class="docutils literal notranslate"><span class="pre"><%def></span></code> and <code class="docutils literal notranslate"><span class="pre"><%block></span></code> are two tags that both demarcate any block of text and/or code. They both exist within generated Python as a callable function, i.e., a Python <code class="docutils literal notranslate"><span class="pre">def</span></code>. They differ in their scope and calling semantics. Whereas <code class="docutils literal notranslate"><span class="pre"><%def></span></code> provides a construct that is very much like a named Python <code class="docutils literal notranslate"><span class="pre">def</span></code>, the <code class="docutils literal notranslate"><span class="pre"><%block></span></code> is more layout oriented.</p> <div class="section" id="using-defs"> <h2>Using Defs<a class="headerlink" href="#using-defs" title="Permalink to this headline">¶</a></h2> <p>The <code class="docutils literal notranslate"><span class="pre"><%def></span></code> tag requires a <code class="docutils literal notranslate"><span class="pre">name</span></code> attribute, where the <code class="docutils literal notranslate"><span class="pre">name</span></code> references a Python function signature:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"hello()"</span><span class="cp">></span><span class="x"></span> <span class="x"> hello world</span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>To invoke the <code class="docutils literal notranslate"><span class="pre"><%def></span></code>, it is normally called as an expression:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="x">the def: </span><span class="cp">${</span><span class="n">hello</span><span class="p">()</span><span class="cp">}</span><span class="x"></span></pre></div> </div> <p>If the <code class="docutils literal notranslate"><span class="pre"><%def></span></code> is not nested inside of another <code class="docutils literal notranslate"><span class="pre"><%def></span></code>, it’s known as a <strong>top level def</strong> and can be accessed anywhere in the template, including above where it was defined.</p> <p>All defs, top level or not, have access to the current contextual namespace in exactly the same way their containing template does. Suppose the template below is executed with the variables <code class="docutils literal notranslate"><span class="pre">username</span></code> and <code class="docutils literal notranslate"><span class="pre">accountdata</span></code> inside the context:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="x">Hello there </span><span class="cp">${</span><span class="n">username</span><span class="cp">}</span><span class="x">, how are ya. Lets see what your account says:</span> <span class="cp">${</span><span class="n">account</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"account()"</span><span class="cp">></span><span class="x"></span> <span class="x"> Account for </span><span class="cp">${</span><span class="n">username</span><span class="cp">}</span><span class="x">:<br/></span> <span class="cp">%</span> <span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">accountdata</span><span class="p">:</span><span class="x"></span> <span class="x"> Value: </span><span class="cp">${</span><span class="n">row</span><span class="cp">}</span><span class="x"><br/></span> <span class="cp">%</span><span class="k"> endfor</span><span class="x"></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>The <code class="docutils literal notranslate"><span class="pre">username</span></code> and <code class="docutils literal notranslate"><span class="pre">accountdata</span></code> variables are present within the main template body as well as the body of the <code class="docutils literal notranslate"><span class="pre">account()</span></code> def.</p> <p>Since defs are just Python functions, you can define and pass arguments to them as well:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp">${</span><span class="n">account</span><span class="p">(</span><span class="n">accountname</span><span class="o">=</span><span class="s1">'john'</span><span class="p">)</span><span class="cp">}</span><span class="x"></span> <span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"account(accountname, type='regular')"</span><span class="cp">></span><span class="x"></span> <span class="x"> account name: </span><span class="cp">${</span><span class="n">accountname</span><span class="cp">}</span><span class="x">, type: </span><span class="cp">${</span><span class="nb">type</span><span class="cp">}</span><span class="x"></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>When you declare an argument signature for your def, they are required to follow normal Python conventions (i.e., all arguments are required except keyword arguments with a default value). This is in contrast to using context-level variables, which evaluate to <code class="docutils literal notranslate"><span class="pre">UNDEFINED</span></code> if you reference a name that does not exist.</p> <div class="section" id="calling-defs-from-other-files"> <h3>Calling Defs from Other Files<a class="headerlink" href="#calling-defs-from-other-files" title="Permalink to this headline">¶</a></h3> <p>Top level <code class="docutils literal notranslate"><span class="pre"><%def></span></code>s are <strong>exported</strong> by your template’s module, and can be called from the outside; including from other templates, as well as normal Python code. Calling a <code class="docutils literal notranslate"><span class="pre"><%def></span></code> from another template is something like using an <code class="docutils literal notranslate"><span class="pre"><%include></span></code> – except you are calling a specific function within the template, not the whole template.</p> <p>The remote <code class="docutils literal notranslate"><span class="pre"><%def></span></code> call is also a little bit like calling functions from other modules in Python. There is an “import” step to pull the names from another template into your own template; then the function or functions are available.</p> <p>To import another template, use the <code class="docutils literal notranslate"><span class="pre"><%namespace></span></code> tag:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">namespace</span> <span class="na">name=</span><span class="s">"mystuff"</span> <span class="na">file=</span><span class="s">"mystuff.html"</span><span class="cp">/></span><span class="x"></span></pre></div> </div> <p>The above tag adds a local variable <code class="docutils literal notranslate"><span class="pre">mystuff</span></code> to the current scope.</p> <p>Then, just call the defs off of <code class="docutils literal notranslate"><span class="pre">mystuff</span></code>:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp">${</span><span class="n">mystuff</span><span class="o">.</span><span class="n">somedef</span><span class="p">(</span><span class="n">x</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span><span class="n">y</span><span class="o">=</span><span class="mi">7</span><span class="p">)</span><span class="cp">}</span><span class="x"></span></pre></div> </div> <p>The <code class="docutils literal notranslate"><span class="pre"><%namespace></span></code> tag also supports some of the other semantics of Python’s <code class="docutils literal notranslate"><span class="pre">import</span></code> statement, including pulling names into the local variable space, or using <code class="docutils literal notranslate"><span class="pre">*</span></code> to represent all names, using the <code class="docutils literal notranslate"><span class="pre">import</span></code> attribute:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">namespace</span> <span class="na">file=</span><span class="s">"mystuff.html"</span> <span class="na">import=</span><span class="s">"foo, bar"</span><span class="cp">/></span><span class="x"></span></pre></div> </div> <p>This is just a quick intro to the concept of a <strong>namespace</strong>, which is a central Mako concept that has its own chapter in these docs. For more detail and examples, see <a class="reference internal" href="namespaces.html"><span class="std std-ref">Namespaces</span></a>.</p> </div> <div class="section" id="calling-defs-programmatically"> <h3>Calling Defs Programmatically<a class="headerlink" href="#calling-defs-programmatically" title="Permalink to this headline">¶</a></h3> <p>You can call defs programmatically from any <a class="reference internal" href="usage.html#mako.template.Template" title="mako.template.Template"><code class="xref py py-class docutils literal notranslate"><span class="pre">Template</span></code></a> object using the <a class="reference internal" href="usage.html#mako.template.Template.get_def" title="mako.template.Template.get_def"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_def()</span></code></a> method, which returns a <a class="reference internal" href="usage.html#mako.template.DefTemplate" title="mako.template.DefTemplate"><code class="xref py py-class docutils literal notranslate"><span class="pre">DefTemplate</span></code></a> object. This is a <a class="reference internal" href="usage.html#mako.template.Template" title="mako.template.Template"><code class="xref py py-class docutils literal notranslate"><span class="pre">Template</span></code></a> subclass which the parent <a class="reference internal" href="usage.html#mako.template.Template" title="mako.template.Template"><code class="xref py py-class docutils literal notranslate"><span class="pre">Template</span></code></a> creates, and is usable like any other template:</p> <div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">mako.template</span> <span class="kn">import</span> <span class="n">Template</span> <span class="n">template</span> <span class="o">=</span> <span class="n">Template</span><span class="p">(</span><span class="s2">"""</span> <span class="s2"> <</span><span class="si">%d</span><span class="s2">ef name="hi(name)"></span> <span class="s2"> hi ${name}!</span> <span class="s2"> </</span><span class="si">%d</span><span class="s2">ef></span> <span class="s2"> <</span><span class="si">%d</span><span class="s2">ef name="bye(name)"></span> <span class="s2"> bye ${name}!</span> <span class="s2"> </</span><span class="si">%d</span><span class="s2">ef></span> <span class="s2">"""</span><span class="p">)</span> <span class="k">print</span><span class="p">(</span><span class="n">template</span><span class="o">.</span><span class="n">get_def</span><span class="p">(</span><span class="s2">"hi"</span><span class="p">)</span><span class="o">.</span><span class="n">render</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s2">"ed"</span><span class="p">))</span> <span class="k">print</span><span class="p">(</span><span class="n">template</span><span class="o">.</span><span class="n">get_def</span><span class="p">(</span><span class="s2">"bye"</span><span class="p">)</span><span class="o">.</span><span class="n">render</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s2">"ed"</span><span class="p">))</span></pre></div> </div> </div> <div class="section" id="defs-within-defs"> <h3>Defs within Defs<a class="headerlink" href="#defs-within-defs" title="Permalink to this headline">¶</a></h3> <p>The def model follows regular Python rules for closures. Declaring <code class="docutils literal notranslate"><span class="pre"><%def></span></code> inside another <code class="docutils literal notranslate"><span class="pre"><%def></span></code> declares it within the parent’s <strong>enclosing scope</strong>:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"mydef()"</span><span class="cp">></span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"subdef()"</span><span class="cp">></span><span class="x"></span> <span class="x"> a sub def</span> <span class="x"> </span><span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="x"> i'm the def, and the subcomponent is </span><span class="cp">${</span><span class="n">subdef</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>Just like Python, names that exist outside the inner <code class="docutils literal notranslate"><span class="pre"><%def></span></code> exist inside it as well:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span> <span class="n">x</span> <span class="o">=</span> <span class="mi">12</span> <span class="cp">%></span><span class="x"></span> <span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"outer()"</span><span class="cp">></span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span> <span class="n">y</span> <span class="o">=</span> <span class="mi">15</span> <span class="cp">%></span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"inner()"</span><span class="cp">></span><span class="x"></span> <span class="x"> inner, x is </span><span class="cp">${</span><span class="n">x</span><span class="cp">}</span><span class="x">, y is </span><span class="cp">${</span><span class="n">y</span><span class="cp">}</span><span class="x"></span> <span class="x"> </span><span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="x"> outer, x is </span><span class="cp">${</span><span class="n">x</span><span class="cp">}</span><span class="x">, y is </span><span class="cp">${</span><span class="n">y</span><span class="cp">}</span><span class="x"></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>Assigning to a name inside of a def declares that name as local to the scope of that def (again, like Python itself). This means the following code will raise an error:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span> <span class="n">x</span> <span class="o">=</span> <span class="mi">10</span> <span class="cp">%></span><span class="x"></span> <span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"somedef()"</span><span class="cp">></span> <span class="cp">## error !</span><span class="x"></span> <span class="x"> somedef, x is </span><span class="cp">${</span><span class="n">x</span><span class="cp">}</span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span> <span class="n">x</span> <span class="o">=</span> <span class="mi">27</span> <span class="cp">%></span><span class="x"></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>…because the assignment to <code class="docutils literal notranslate"><span class="pre">x</span></code> declares <code class="docutils literal notranslate"><span class="pre">x</span></code> as local to the scope of <code class="docutils literal notranslate"><span class="pre">somedef</span></code>, rendering the “outer” version unreachable in the expression that tries to render it.</p> </div> <div class="section" id="calling-a-def-with-embedded-content-and-or-other-defs"> <span id="defs-with-content"></span><h3>Calling a Def with Embedded Content and/or Other Defs<a class="headerlink" href="#calling-a-def-with-embedded-content-and-or-other-defs" title="Permalink to this headline">¶</a></h3> <p>A flip-side to def within def is a def call with content. This is where you call a def, and at the same time declare a block of content (or multiple blocks) that can be used by the def being called. The main point of such a call is to create custom, nestable tags, just like any other template language’s custom-tag creation system – where the external tag controls the execution of the nested tags and can communicate state to them. Only with Mako, you don’t have to use any external Python modules, you can define arbitrarily nestable tags right in your templates.</p> <p>To achieve this, the target def is invoked using the form <code class="docutils literal notranslate"><span class="pre"><%namespacename:defname></span></code> instead of the normal <code class="docutils literal notranslate"><span class="pre">${}</span></code> syntax. This syntax, introduced in Mako 0.2.3, is functionally equivalent to another tag known as <code class="docutils literal notranslate"><span class="pre">%call</span></code>, which takes the form <code class="docutils literal notranslate"><span class="pre"><%call</span> <span class="pre">expr='namespacename.defname(args)'></span></code>. While <code class="docutils literal notranslate"><span class="pre">%call</span></code> is available in all versions of Mako, the newer style is probably more familiar looking. The <code class="docutils literal notranslate"><span class="pre">namespace</span></code> portion of the call is the name of the <strong>namespace</strong> in which the def is defined – in the most simple cases, this can be <code class="docutils literal notranslate"><span class="pre">local</span></code> or <code class="docutils literal notranslate"><span class="pre">self</span></code> to reference the current template’s namespace (the difference between <code class="docutils literal notranslate"><span class="pre">local</span></code> and <code class="docutils literal notranslate"><span class="pre">self</span></code> is one of inheritance – see <a class="reference internal" href="namespaces.html#namespaces-builtin"><span class="std std-ref">Built-in Namespaces</span></a> for details).</p> <p>When the target def is invoked, a variable <code class="docutils literal notranslate"><span class="pre">caller</span></code> is placed in its context which contains another namespace containing the body and other defs defined by the caller. The body itself is referenced by the method <code class="docutils literal notranslate"><span class="pre">body()</span></code>. Below, we build a <code class="docutils literal notranslate"><span class="pre">%def</span></code> that operates upon <code class="docutils literal notranslate"><span class="pre">caller.body()</span></code> to invoke the body of the custom tag:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"buildtable()"</span><span class="cp">></span><span class="x"></span> <span class="x"> <table></span> <span class="x"> <tr><td></span> <span class="x"> </span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="x"> </td></tr></span> <span class="x"> </table></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="cp"><%</span><span class="nb">self:buildtable</span><span class="cp">></span><span class="x"></span> <span class="x"> I am the table body.</span> <span class="cp"></%</span><span class="nb">self:buildtable</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>This produces the output (whitespace formatted):</p> <div class="highlight-html notranslate"><div class="highlight"><pre><span></span><span class="p"><</span><span class="nt">table</span><span class="p">></span> <span class="p"><</span><span class="nt">tr</span><span class="p">><</span><span class="nt">td</span><span class="p">></span> I am the table body. <span class="p"></</span><span class="nt">td</span><span class="p">></</span><span class="nt">tr</span><span class="p">></span> <span class="p"></</span><span class="nt">table</span><span class="p">></span></pre></div> </div> <p>Using the older <code class="docutils literal notranslate"><span class="pre">%call</span></code> syntax looks like:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"buildtable()"</span><span class="cp">></span><span class="x"></span> <span class="x"> <table></span> <span class="x"> <tr><td></span> <span class="x"> </span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="x"> </td></tr></span> <span class="x"> </table></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="cp"><%</span><span class="nb">call</span> <span class="na">expr=</span><span class="s">"buildtable()"</span><span class="cp">></span><span class="x"></span> <span class="x"> I am the table body.</span> <span class="cp"></%</span><span class="nb">call</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>The <code class="docutils literal notranslate"><span class="pre">body()</span></code> can be executed multiple times or not at all. This means you can use def-call-with-content to build iterators, conditionals, etc:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"lister(count)"</span><span class="cp">></span> <span class="cp">%</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">count</span><span class="p">):</span><span class="x"></span> <span class="x"> </span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span> <span class="cp">%</span><span class="k"> endfor</span><span class="x"></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="cp"><%</span><span class="nb">self:lister</span> <span class="na">count=</span><span class="s">"${3}"</span><span class="cp">></span><span class="x"></span> <span class="x"> hi</span> <span class="cp"></%</span><span class="nb">self:lister</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>Produces:</p> <div class="highlight-html notranslate"><div class="highlight"><pre><span></span>hi hi hi</pre></div> </div> <p>Notice above we pass <code class="docutils literal notranslate"><span class="pre">3</span></code> as a Python expression, so that it remains as an integer.</p> <p>A custom “conditional” tag:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"conditional(expression)"</span><span class="cp">></span> <span class="cp">%</span> <span class="k">if</span> <span class="n">expression</span><span class="p">:</span><span class="x"></span> <span class="x"> </span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span> <span class="cp">%</span><span class="k"> endif</span><span class="x"></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="cp"><%</span><span class="nb">self:conditional</span> <span class="na">expression=</span><span class="s">"${4==4}"</span><span class="cp">></span><span class="x"></span> <span class="x"> i'm the result</span> <span class="cp"></%</span><span class="nb">self:conditional</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>Produces:</p> <div class="highlight-html notranslate"><div class="highlight"><pre><span></span>i'm the result</pre></div> </div> <p>But that’s not all. The <code class="docutils literal notranslate"><span class="pre">body()</span></code> function also can handle arguments, which will augment the local namespace of the body callable. The caller must define the arguments which it expects to receive from its target def using the <code class="docutils literal notranslate"><span class="pre">args</span></code> attribute, which is a comma-separated list of argument names. Below, our <code class="docutils literal notranslate"><span class="pre"><%def></span></code> calls the <code class="docutils literal notranslate"><span class="pre">body()</span></code> of its caller, passing in an element of data from its argument:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"layoutdata(somedata)"</span><span class="cp">></span><span class="x"></span> <span class="x"> <table></span> <span class="cp">%</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">somedata</span><span class="p">:</span><span class="x"></span> <span class="x"> <tr></span> <span class="cp">%</span> <span class="k">for</span> <span class="n">col</span> <span class="ow">in</span> <span class="n">item</span><span class="p">:</span><span class="x"></span> <span class="x"> <td></span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">body</span><span class="p">(</span><span class="n">col</span><span class="o">=</span><span class="n">col</span><span class="p">)</span><span class="cp">}</span><span class="x"></td></span> <span class="cp">%</span><span class="k"> endfor</span><span class="x"></span> <span class="x"> </tr></span> <span class="cp">%</span><span class="k"> endfor</span><span class="x"></span> <span class="x"> </table></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="cp"><%</span><span class="nb">self:layoutdata</span> <span class="na">somedata=</span><span class="s">"${[[1,2,3],[4,5,6],[7,8,9]]}"</span> <span class="na">args=</span><span class="s">"col"</span><span class="cp">></span><span class="x">\</span> <span class="x">Body data: </span><span class="cp">${</span><span class="n">col</span><span class="cp">}</span><span class="x">\</span> <span class="cp"></%</span><span class="nb">self:layoutdata</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>Produces:</p> <div class="highlight-html notranslate"><div class="highlight"><pre><span></span><span class="p"><</span><span class="nt">table</span><span class="p">></span> <span class="p"><</span><span class="nt">tr</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 1<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 2<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 3<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"></</span><span class="nt">tr</span><span class="p">></span> <span class="p"><</span><span class="nt">tr</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 4<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 5<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 6<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"></</span><span class="nt">tr</span><span class="p">></span> <span class="p"><</span><span class="nt">tr</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 7<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 8<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"><</span><span class="nt">td</span><span class="p">></span>Body data: 9<span class="p"></</span><span class="nt">td</span><span class="p">></span> <span class="p"></</span><span class="nt">tr</span><span class="p">></span> <span class="p"></</span><span class="nt">table</span><span class="p">></span></pre></div> </div> <p>You don’t have to stick to calling just the <code class="docutils literal notranslate"><span class="pre">body()</span></code> function. The caller can define any number of callables, allowing the <code class="docutils literal notranslate"><span class="pre"><%call></span></code> tag to produce whole layouts:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"layout()"</span><span class="cp">></span> <span class="cp">## a layout def</span><span class="x"></span> <span class="x"> <div class="mainlayout"></span> <span class="x"> <div class="header"></span> <span class="x"> </span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">header</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="x"> </div></span> <span class="x"> <div class="sidebar"></span> <span class="x"> </span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">sidebar</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="x"> </div></span> <span class="x"> <div class="content"></span> <span class="x"> </span><span class="cp">${</span><span class="n">caller</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="x"> </div></span> <span class="x"> </div></span> <span class="cp"></%</span><span class="nb">def</span><span class="cp">></span> <span class="cp">## calls the layout def</span><span class="x"></span> <span class="cp"><%</span><span class="nb">self:layout</span><span class="cp">></span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"header()"</span><span class="cp">></span><span class="x"></span> <span class="x"> I am the header</span> <span class="x"> </span><span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"sidebar()"</span><span class="cp">></span><span class="x"></span> <span class="x"> <ul></span> <span class="x"> <li>sidebar 1</li></span> <span class="x"> <li>sidebar 2</li></span> <span class="x"> </ul></span> <span class="x"> </span><span class="cp"></%</span><span class="nb">def</span><span class="cp">></span><span class="x"></span> <span class="x"> this is the body</span> <span class="cp"></%</span><span class="nb">self:layout</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>The above layout would produce:</p> <div class="highlight-html notranslate"><div class="highlight"><pre><span></span><span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"mainlayout"</span><span class="p">></span> <span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"header"</span><span class="p">></span> I am the header <span class="p"></</span><span class="nt">div</span><span class="p">></span> <span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"sidebar"</span><span class="p">></span> <span class="p"><</span><span class="nt">ul</span><span class="p">></span> <span class="p"><</span><span class="nt">li</span><span class="p">></span>sidebar 1<span class="p"></</span><span class="nt">li</span><span class="p">></span> <span class="p"><</span><span class="nt">li</span><span class="p">></span>sidebar 2<span class="p"></</span><span class="nt">li</span><span class="p">></span> <span class="p"></</span><span class="nt">ul</span><span class="p">></span> <span class="p"></</span><span class="nt">div</span><span class="p">></span> <span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"content"</span><span class="p">></span> this is the body <span class="p"></</span><span class="nt">div</span><span class="p">></span> <span class="p"></</span><span class="nt">div</span><span class="p">></span></pre></div> </div> <p>The number of things you can do with <code class="docutils literal notranslate"><span class="pre"><%call></span></code> and/or the <code class="docutils literal notranslate"><span class="pre"><%namespacename:defname></span></code> calling syntax is enormous. You can create form widget libraries, such as an enclosing <code class="docutils literal notranslate"><span class="pre"><FORM></span></code> tag and nested HTML input elements, or portable wrapping schemes using <code class="docutils literal notranslate"><span class="pre"><div></span></code> or other elements. You can create tags that interpret rows of data, such as from a database, providing the individual columns of each row to a <code class="docutils literal notranslate"><span class="pre">body()</span></code> callable which lays out the row any way it wants. Basically anything you’d do with a “custom tag” or tag library in some other system, Mako provides via <code class="docutils literal notranslate"><span class="pre"><%def></span></code> tags and plain Python callables which are invoked via <code class="docutils literal notranslate"><span class="pre"><%namespacename:defname></span></code> or <code class="docutils literal notranslate"><span class="pre"><%call></span></code>.</p> </div> </div> <div class="section" id="using-blocks"> <span id="blocks"></span><h2>Using Blocks<a class="headerlink" href="#using-blocks" title="Permalink to this headline">¶</a></h2> <p>The <code class="docutils literal notranslate"><span class="pre"><%block></span></code> tag introduces some new twists on the <code class="docutils literal notranslate"><span class="pre"><%def></span></code> tag which make it more closely tailored towards layout.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 0.4.1.</span></p> </div> <p>An example of a block:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="x"><html></span> <span class="x"> <body></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"> this is a block.</span> <span class="x"> </span><span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"> </body></span> <span class="x"></html></span></pre></div> </div> <p>In the above example, we define a simple block. The block renders its content in the place that it’s defined. Since the block is called for us, it doesn’t need a name and the above is referred to as an <strong>anonymous block</strong>. So the output of the above template will be:</p> <div class="highlight-html notranslate"><div class="highlight"><pre><span></span><span class="p"><</span><span class="nt">html</span><span class="p">></span> <span class="p"><</span><span class="nt">body</span><span class="p">></span> this is a block. <span class="p"></</span><span class="nt">body</span><span class="p">></span> <span class="p"></</span><span class="nt">html</span><span class="p">></span></pre></div> </div> <p>So in fact the above block has absolutely no effect. Its usefulness comes when we start using modifiers. Such as, we can apply a filter to our block:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="x"><html></span> <span class="x"> <body></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span> <span class="na">filter=</span><span class="s">"h"</span><span class="cp">></span><span class="x"></span> <span class="x"> <html>this is some escaped html.</html></span> <span class="x"> </span><span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"> </body></span> <span class="x"></html></span></pre></div> </div> <p>or perhaps a caching directive:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="x"><html></span> <span class="x"> <body></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span> <span class="na">cached=</span><span class="s">"True"</span> <span class="na">cache_timeout=</span><span class="s">"60"</span><span class="cp">></span><span class="x"></span> <span class="x"> This content will be cached for 60 seconds.</span> <span class="x"> </span><span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"> </body></span> <span class="x"></html></span></pre></div> </div> <p>Blocks also work in iterations, conditionals, just like defs:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp">%</span> <span class="k">if</span> <span class="n">some_condition</span><span class="p">:</span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span><span class="cp">></span><span class="x">condition is met</span><span class="cp"></%</span><span class="nb">block</span><span class="cp">></span> <span class="cp">%</span><span class="k"> endif</span><span class="x"></span></pre></div> </div> <p>While the block renders at the point it is defined in the template, the underlying function is present in the generated Python code only once, so there’s no issue with placing a block inside of a loop or similar. Anonymous blocks are defined as closures in the local rendering body, so have access to local variable scope:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp">%</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">4</span><span class="p">):</span><span class="x"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span><span class="cp">></span><span class="x">i is </span><span class="cp">${</span><span class="n">i</span><span class="cp">}</%</span><span class="nb">block</span><span class="cp">></span> <span class="cp">%</span><span class="k"> endfor</span><span class="x"></span></pre></div> </div> <div class="section" id="using-named-blocks"> <h3>Using Named Blocks<a class="headerlink" href="#using-named-blocks" title="Permalink to this headline">¶</a></h3> <p>Possibly the more important area where blocks are useful is when we do actually give them names. Named blocks are tailored to behave somewhat closely to Jinja2’s block tag, in that they define an area of a layout which can be overridden by an inheriting template. In sharp contrast to the <code class="docutils literal notranslate"><span class="pre"><%def></span></code> tag, the name given to a block is global for the entire template regardless of how deeply it’s nested:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="x"><html></span> <span class="cp"><%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">"header"</span><span class="cp">></span><span class="x"></span> <span class="x"> <head></span> <span class="x"> <title></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">"title"</span><span class="cp">></span><span class="x">Title</span><span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"> </title></span> <span class="x"> </head></span> <span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"><body></span> <span class="x"> </span><span class="cp">${</span><span class="nb">next</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="x"></body></span> <span class="x"></html></span></pre></div> </div> <p>The above example has two named blocks “<code class="docutils literal notranslate"><span class="pre">header</span></code>” and “<code class="docutils literal notranslate"><span class="pre">title</span></code>”, both of which can be referred to by an inheriting template. A detailed walkthrough of this usage can be found at <a class="reference internal" href="inheritance.html"><span class="std std-ref">Inheritance</span></a>.</p> <p>Note above that named blocks don’t have any argument declaration the way defs do. They still implement themselves as Python functions, however, so they can be invoked additional times beyond their initial definition:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="x"><div name="page"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">"pagecontrol"</span><span class="cp">></span><span class="x"></span> <span class="x"> <a href="">previous page</a> |</span> <span class="x"> <a href="">next page</a></span> <span class="x"> </span><span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"> <table></span> <span class="x"> ## some content</span> <span class="x"> </table></span> <span class="x"> </span><span class="cp">${</span><span class="n">pagecontrol</span><span class="p">()</span><span class="cp">}</span><span class="x"></span> <span class="x"></div></span></pre></div> </div> <p>The content referenced by <code class="docutils literal notranslate"><span class="pre">pagecontrol</span></code> above will be rendered both above and below the <code class="docutils literal notranslate"><span class="pre"><table></span></code> tags.</p> <p>To keep things sane, named blocks have restrictions that defs do not:</p> <ul class="simple"> <li><p>The <code class="docutils literal notranslate"><span class="pre"><%block></span></code> declaration cannot have any argument signature.</p></li> <li><p>The name of a <code class="docutils literal notranslate"><span class="pre"><%block></span></code> can only be defined once in a template – an error is raised if two blocks of the same name occur anywhere in a single template, regardless of nesting. A similar error is raised if a top level def shares the same name as that of a block.</p></li> <li><p>A named <code class="docutils literal notranslate"><span class="pre"><%block></span></code> cannot be defined within a <code class="docutils literal notranslate"><span class="pre"><%def></span></code>, or inside the body of a “call”, i.e. <code class="docutils literal notranslate"><span class="pre"><%call></span></code> or <code class="docutils literal notranslate"><span class="pre"><%namespacename:defname></span></code> tag. Anonymous blocks can, however.</p></li> </ul> </div> <div class="section" id="using-page-arguments-in-named-blocks"> <h3>Using Page Arguments in Named Blocks<a class="headerlink" href="#using-page-arguments-in-named-blocks" title="Permalink to this headline">¶</a></h3> <p>A named block is very much like a top level def. It has a similar restriction to these types of defs in that arguments passed to the template via the <code class="docutils literal notranslate"><span class="pre"><%page></span></code> tag aren’t automatically available. Using arguments with the <code class="docutils literal notranslate"><span class="pre"><%page></span></code> tag is described in the section <a class="reference internal" href="namespaces.html#namespaces-body"><span class="std std-ref">The body() Method</span></a>, and refers to scenarios such as when the <code class="docutils literal notranslate"><span class="pre">body()</span></code> method of a template is called from an inherited template passing arguments, or the template is invoked from an <code class="docutils literal notranslate"><span class="pre"><%include></span></code> tag with arguments. To allow a named block to share the same arguments passed to the page, the <code class="docutils literal notranslate"><span class="pre">args</span></code> attribute can be used:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">page</span> <span class="na">args=</span><span class="s">"post"</span><span class="cp">/></span><span class="x"></span> <span class="x"><a name="</span><span class="cp">${</span><span class="n">post</span><span class="o">.</span><span class="n">title</span><span class="cp">}</span><span class="x">" /></span> <span class="x"><span class="post_prose"></span> <span class="x"> </span><span class="cp"><%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">"post_prose"</span> <span class="na">args=</span><span class="s">"post"</span><span class="cp">></span><span class="x"></span> <span class="x"> </span><span class="cp">${</span><span class="n">post</span><span class="o">.</span><span class="n">content</span><span class="cp">}</span><span class="x"></span> <span class="x"> </span><span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span> <span class="x"></span></span></pre></div> </div> <p>Where above, if the template is called via a directive like <code class="docutils literal notranslate"><span class="pre"><%include</span> <span class="pre">file="post.mako"</span> <span class="pre">args="post=post"</span> <span class="pre">/></span></code>, the <code class="docutils literal notranslate"><span class="pre">post</span></code> variable is available both in the main body as well as the <code class="docutils literal notranslate"><span class="pre">post_prose</span></code> block.</p> <p>Similarly, the <code class="docutils literal notranslate"><span class="pre">**pageargs</span></code> variable is present, in named blocks only, for those arguments not explicit in the <code class="docutils literal notranslate"><span class="pre"><%page></span></code> tag:</p> <div class="highlight-mako notranslate"><div class="highlight"><pre><span></span><span class="cp"><%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">"post_prose"</span><span class="cp">></span><span class="x"></span> <span class="x"> </span><span class="cp">${</span><span class="n">pageargs</span><span class="p">[</span><span class="s1">'post'</span><span class="p">]</span><span class="o">.</span><span class="n">content</span><span class="cp">}</span><span class="x"></span> <span class="cp"></%</span><span class="nb">block</span><span class="cp">></span><span class="x"></span></pre></div> </div> <p>The <code class="docutils literal notranslate"><span class="pre">args</span></code> attribute is only allowed with named blocks. With anonymous blocks, the Python function is always rendered in the same scope as the call itself, so anything available directly outside the anonymous block is available inside as well.</p> </div> </div> </div> </div> </div> <div id="docs-bottom-navigation" class="docs-navigation-links"> Previous: <a href="syntax.html" title="previous chapter">Syntax</a> Next: <a href="runtime.html" title="next chapter">The Mako Runtime Environment</a> <div id="docs-copyright"> © Copyright the Mako authors and contributors. 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