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<div class="section" id="switching-from-other-template-engines">
<h1>Switching from other Template Engines<a class="headerlink" href="#switching-from-other-template-engines" title="Permalink to this headline">¶</a></h1>
<p>If you have used a different template engine in the past and want to switch
to Jinja2 here is a small guide that shows the basic syntatic and semantic
changes between some common, similar text template engines for Python.</p>
<div class="section" id="jinja1">
<h2>Jinja1<a class="headerlink" href="#jinja1" title="Permalink to this headline">¶</a></h2>
<p>Jinja2 is mostly compatible with Jinja1 in terms of API usage and template
syntax. The differences between Jinja1 and 2 are explained in the following
list.</p>
<div class="section" id="api">
<h3>API<a class="headerlink" href="#api" title="Permalink to this headline">¶</a></h3>
<dl class="docutils">
<dt>Loaders</dt>
<dd>Jinja2 uses a different loader API. Because the internal representation
of templates changed there is no longer support for external caching
systems such as memcached. The memory consumed by templates is comparable
with regular Python modules now and external caching doesn’t give any
advantage. If you have used a custom loader in the past have a look at
the new <a class="reference internal" href="api.html#loaders"><em>loader API</em></a>.</dd>
<dt>Loading templates from strings</dt>
<dd>In the past it was possible to generate templates from a string with the
default environment configuration by using <cite>jinja.from_string</cite>. Jinja2
provides a <tt class="xref py py-class docutils literal"><span class="pre">Template</span></tt> class that can be used to do the same, but
with optional additional configuration.</dd>
<dt>Automatic unicode conversion</dt>
<dd>Jinja1 performed automatic conversion of bytestrings in a given encoding
into unicode objects. This conversion is no longer implemented as it
was inconsistent as most libraries are using the regular Python ASCII
bytestring to Unicode conversion. An application powered by Jinja2
<em>has to</em> use unicode internally everywhere or make sure that Jinja2 only
gets unicode strings passed.</dd>
<dt>i18n</dt>
<dd>Jinja1 used custom translators for internationalization. i18n is now
available as Jinja2 extension and uses a simpler, more gettext friendly
interface and has support for babel. For more details see
<a class="reference internal" href="extensions.html#i18n-extension"><em>i18n Extension</em></a>.</dd>
<dt>Internal methods</dt>
<dd>Jinja1 exposed a few internal methods on the environment object such
as <cite>call_function</cite>, <cite>get_attribute</cite> and others. While they were marked
as being an internal method it was possible to override them. Jinja2
doesn’t have equivalent methods.</dd>
<dt>Sandbox</dt>
<dd>Jinja1 was running sandbox mode by default. Few applications actually
used that feature so it became optional in Jinja2. For more details
about the sandboxed execution see <tt class="xref py py-class docutils literal"><span class="pre">SandboxedEnvironment</span></tt>.</dd>
<dt>Context</dt>
<dd>Jinja1 had a stacked context as storage for variables passed to the
environment. In Jinja2 a similar object exists but it doesn’t allow
modifications nor is it a singleton. As inheritance is dynamic now
multiple context objects may exist during template evaluation.</dd>
<dt>Filters and Tests</dt>
<dd>Filters and tests are regular functions now. It’s no longer necessary
and allowed to use factory functions.</dd>
</dl>
</div>
<div class="section" id="templates">
<h3>Templates<a class="headerlink" href="#templates" title="Permalink to this headline">¶</a></h3>
<p>Jinja2 has mostly the same syntax as Jinja1. What’s different is that
macros require parentheses around the argument list now.</p>
<p>Additionally Jinja2 allows dynamic inheritance now and dynamic includes.
The old helper function <cite>rendertemplate</cite> is gone now, <cite>include</cite> can be used
instead. Includes no longer import macros and variable assignments, for
that the new <cite>import</cite> tag is used. This concept is explained in the
<a class="reference internal" href="templates.html#import"><em>Import</em></a> documentation.</p>
<p>Another small change happened in the <cite>for</cite>-tag. The special loop variable
doesn’t have a <cite>parent</cite> attribute, instead you have to alias the loop
yourself. See <a class="reference internal" href="tricks.html#accessing-the-parent-loop"><em>Accessing the parent Loop</em></a> for more details.</p>
</div>
</div>
<div class="section" id="django">
<h2>Django<a class="headerlink" href="#django" title="Permalink to this headline">¶</a></h2>
<p>If you have previously worked with Django templates, you should find
Jinja2 very familiar. In fact, most of the syntax elements look and
work the same.</p>
<p>However, Jinja2 provides some more syntax elements covered in the
documentation and some work a bit different.</p>
<p>This section covers the template changes. As the API is fundamentally
different we won’t cover it here.</p>
<div class="section" id="method-calls">
<h3>Method Calls<a class="headerlink" href="#method-calls" title="Permalink to this headline">¶</a></h3>
<p>In Django method calls work implicitly. With Jinja2 you have to specify that
you want to call an object. Thus this Django code:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">for</span> <span class="nv">page</span> <span class="k">in</span> <span class="nv">user.get_created_pages</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
</pre></div>
</div>
<p>will look like this in Jinja:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">for</span> <span class="nv">page</span> <span class="k">in</span> <span class="nv">user.get_created_pages</span><span class="o">()</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
</pre></div>
</div>
<p>This allows you to pass variables to the function which is also used for macros
which is not possible in Django.</p>
</div>
<div class="section" id="conditions">
<h3>Conditions<a class="headerlink" href="#conditions" title="Permalink to this headline">¶</a></h3>
<p>In Django you can use the following constructs to check for equality:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">ifequal</span> <span class="nv">foo</span> <span class="s2">"bar"</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">else</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">endifequal</span> <span class="cp">%}</span>
</pre></div>
</div>
<p>In Jinja2 you can use the normal if statement in combination with operators:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">if</span> <span class="nv">foo</span> <span class="o">==</span> <span class="s1">'bar'</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">else</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">endif</span> <span class="cp">%}</span>
</pre></div>
</div>
<p>You can also have multiple elif branches in your template:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">if</span> <span class="nv">something</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">elif</span> <span class="nv">otherthing</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">elif</span> <span class="nv">foothing</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">else</span> <span class="cp">%}</span>
...
<span class="cp">{%</span> <span class="k">endif</span> <span class="cp">%}</span>
</pre></div>
</div>
</div>
<div class="section" id="filter-arguments">
<h3>Filter Arguments<a class="headerlink" href="#filter-arguments" title="Permalink to this headline">¶</a></h3>
<p>Jinja2 provides more than one argument for filters. Also the syntax for
argument passing is different. A template that looks like this in Django:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{{</span> <span class="nv">items</span><span class="o">|</span><span class="nf">join</span><span class="s2">:", "</span> <span class="cp">}}</span>
</pre></div>
</div>
<p>looks like this in Jinja2:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{{</span> <span class="nv">items</span><span class="o">|</span><span class="nf">join</span><span class="o">(</span><span class="s1">', '</span><span class="o">)</span> <span class="cp">}}</span>
</pre></div>
</div>
<p>In fact it’s a bit more verbose but it allows different types of arguments -
including variables - and more than one of them.</p>
</div>
<div class="section" id="tests">
<h3>Tests<a class="headerlink" href="#tests" title="Permalink to this headline">¶</a></h3>
<p>In addition to filters there also are tests you can perform using the is
operator. Here are some examples:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">if</span> <span class="nv">user.user_id</span> <span class="k">is</span> <span class="nf">odd</span> <span class="cp">%}</span>
<span class="cp">{{</span> <span class="nv">user.username</span><span class="o">|</span><span class="nf">e</span> <span class="cp">}}</span> is odd
<span class="cp">{%</span> <span class="k">else</span> <span class="cp">%}</span>
hmm. <span class="cp">{{</span> <span class="nv">user.username</span><span class="o">|</span><span class="nf">e</span> <span class="cp">}}</span> looks pretty normal
<span class="cp">{%</span> <span class="k">endif</span> <span class="cp">%}</span>
</pre></div>
</div>
</div>
<div class="section" id="loops">
<h3>Loops<a class="headerlink" href="#loops" title="Permalink to this headline">¶</a></h3>
<p>For loops work very similar to Django. Notably, in Jinja2 the special variable for
the loop context is called <cite>loop</cite> and not <cite>forloop</cite> like in Django.</p>
<p>In addition, the Django <cite>empty</cite> argument is called <cite>else</cite> in Jinja2. For example, the
Django template:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">for</span> <span class="nv">item</span> <span class="k">in</span> <span class="nv">items</span> <span class="cp">%}</span>
<span class="cp">{{</span> <span class="nv">item</span> <span class="cp">}}</span>
<span class="cp">{%</span> <span class="k">empty</span> <span class="cp">%}</span>
No items!
<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
</pre></div>
</div>
<p>would be handled in Jinja2 as:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">for</span> <span class="nv">item</span> <span class="k">in</span> <span class="nv">items</span> <span class="cp">%}</span>
<span class="cp">{{</span> <span class="nv">item</span> <span class="cp">}}</span>
<span class="cp">{%</span> <span class="k">else</span> <span class="cp">%}</span>
No items!
<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
</pre></div>
</div>
</div>
<div class="section" id="cycle">
<h3>Cycle<a class="headerlink" href="#cycle" title="Permalink to this headline">¶</a></h3>
<p>The <tt class="docutils literal"><span class="pre">{%</span> <span class="pre">cycle</span> <span class="pre">%}</span></tt> tag does not exist in Jinja because of it’s implicit
nature. However you can achieve mostly the same by using the <cite>cycle</cite>
method on a loop object.</p>
<p>The following Django template:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">for</span> <span class="nv">user</span> <span class="k">in</span> <span class="nv">users</span> <span class="cp">%}</span>
<span class="nt"><li</span> <span class="na">class=</span><span class="s">"</span><span class="cp">{%</span> <span class="k">cycle</span> <span class="s1">'odd'</span> <span class="s1">'even'</span> <span class="cp">%}</span><span class="s">"</span><span class="nt">></span><span class="cp">{{</span> <span class="nv">user</span> <span class="cp">}}</span><span class="nt"></li></span>
<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
</pre></div>
</div>
<p>Would look like this in Jinja:</p>
<div class="highlight-html+jinja"><div class="highlight"><pre><span class="cp">{%</span> <span class="k">for</span> <span class="nv">user</span> <span class="k">in</span> <span class="nv">users</span> <span class="cp">%}</span>
<span class="nt"><li</span> <span class="na">class=</span><span class="s">"</span><span class="cp">{{</span> <span class="nb">loop</span><span class="nv">.cycle</span><span class="o">(</span><span class="s1">'odd'</span><span class="o">,</span> <span class="s1">'even'</span><span class="o">)</span> <span class="cp">}}</span><span class="s">"</span><span class="nt">></span><span class="cp">{{</span> <span class="nv">user</span> <span class="cp">}}</span><span class="nt"></li></span>
<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
</pre></div>
</div>
<p>There is no equivalent of <tt class="docutils literal"><span class="pre">{%</span> <span class="pre">cycle</span> <span class="pre">...</span> <span class="pre">as</span> <span class="pre">variable</span> <span class="pre">%}</span></tt>.</p>
</div>
</div>
<div class="section" id="mako">
<h2>Mako<a class="headerlink" href="#mako" title="Permalink to this headline">¶</a></h2>
<p>If you have used Mako so far and want to switch to Jinja2 you can configure
Jinja2 to look more like Mako:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">env</span> <span class="o">=</span> <span class="n">Environment</span><span class="p">(</span><span class="s">'<%'</span><span class="p">,</span> <span class="s">'%>'</span><span class="p">,</span> <span class="s">'${'</span><span class="p">,</span> <span class="s">'}'</span><span class="p">,</span> <span class="s">'<</span><span class="si">%d</span><span class="s">oc>'</span><span class="p">,</span> <span class="s">'</</span><span class="si">%d</span><span class="s">oc>'</span><span class="p">,</span> <span class="s">'%'</span><span class="p">,</span> <span class="s">'##'</span><span class="p">)</span>
</pre></div>
</div>
<p>Once the environment is configured like that Jinja2 should be able to interpret
a small subset of Mako templates. Jinja2 does not support embedded Python code
so you would have to move that out of the template. The syntax for defs (in
Jinja2 defs are called macros) and template inheritance is different too. The
following Mako template:</p>
<div class="highlight-html+mako"><div class="highlight"><pre><span class="cp"><%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">"layout.html"</span> <span class="cp">/></span>
<span class="cp"><%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">"title()"</span><span class="cp">></span>Page Title<span class="cp"></%</span><span class="nb">def</span><span class="cp">></span>
<span class="nt"><ul></span>
<span class="cp">%</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="nb">list</span><span class="p">:</span>
<span class="nt"><li></span><span class="cp">${</span><span class="n">item</span><span class="cp">}</span><span class="nt"></li></span>
<span class="cp">%</span><span class="k"> endfor</span>
<span class="nt"></ul></span>
</pre></div>
</div>
<p>Looks like this in Jinja2 with the above configuration:</p>
<div class="highlight-html+mako"><div class="highlight"><pre><span class="cp"><%</span> <span class="n">extends</span> <span class="s">"layout.html"</span> <span class="cp">%></span>
<span class="cp"><%</span> <span class="n">block</span> <span class="n">title</span> <span class="cp">%></span>Page Title<span class="cp"><%</span> <span class="n">endblock</span> <span class="cp">%></span>
<span class="cp"><%</span> <span class="n">block</span> <span class="n">body</span> <span class="cp">%></span>
<span class="nt"><ul></span>
<span class="cp">%</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="nb">list</span><span class="p">:</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="cp">%</span><span class="k"> endfor</span>
<span class="nt"></ul></span>
<span class="cp"><%</span> <span class="n">endblock</span> <span class="cp">%></span>
</pre></div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Switching from other Template Engines</a><ul>
<li><a class="reference internal" href="#jinja1">Jinja1</a><ul>
<li><a class="reference internal" href="#api">API</a></li>
<li><a class="reference internal" href="#templates">Templates</a></li>
</ul>
</li>
<li><a class="reference internal" href="#django">Django</a><ul>
<li><a class="reference internal" href="#method-calls">Method Calls</a></li>
<li><a class="reference internal" href="#conditions">Conditions</a></li>
<li><a class="reference internal" href="#filter-arguments">Filter Arguments</a></li>
<li><a class="reference internal" href="#tests">Tests</a></li>
<li><a class="reference internal" href="#loops">Loops</a></li>
<li><a class="reference internal" href="#cycle">Cycle</a></li>
</ul>
</li>
<li><a class="reference internal" href="#mako">Mako</a></li>
</ul>
</li>
</ul>
<h3>Related Topics</h3>
<ul>
<li><a href="index.html">Documentation overview</a><ul>
<li>Previous: <a href="integration.html" title="previous chapter">Integration</a></li>
<li>Next: <a href="tricks.html" title="next chapter">Tips and Tricks</a></li>
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