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<div class="section" id="larger-applications">
<span id="id1"></span><h1>Larger Applications<a class="headerlink" href="#larger-applications" title="Permalink to this headline">¶</a></h1>
<p>For larger applications it’s a good idea to use a package instead of a
module. That is quite simple. Imagine a small application looks like
this:</p>
<div class="highlight-python"><pre>/yourapplication
/yourapplication.py
/static
/style.css
/templates
layout.html
index.html
login.html
...</pre>
</div>
<div class="section" id="simple-packages">
<h2>Simple Packages<a class="headerlink" href="#simple-packages" title="Permalink to this headline">¶</a></h2>
<p>To convert that into a larger one, just create a new folder
<cite>yourapplication</cite> inside the existing one and move everything below it.
Then rename <cite>yourapplication.py</cite> to <cite>__init__.py</cite>. (Make sure to delete
all <cite>.pyc</cite> files first, otherwise things would most likely break)</p>
<p>You should then end up with something like that:</p>
<div class="highlight-python"><pre>/yourapplication
/yourapplication
/__init__.py
/static
/style.css
/templates
layout.html
index.html
login.html
...</pre>
</div>
<p>But how do you run your application now? The naive <tt class="docutils literal"><span class="pre">python</span>
<span class="pre">yourapplication/__init__.py</span></tt> will not work. Let’s just say that Python
does not want modules in packages to be the startup file. But that is not
a big problem, just add a new file called <cite>runserver.py</cite> next to the inner
<cite>yourapplication</cite> folder with the following contents:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">yourapplication</span> <span class="kn">import</span> <span class="n">app</span>
<span class="n">app</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">debug</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
</pre></div>
</div>
<p>What did we gain from this? Now we can restructure the application a bit
into multiple modules. The only thing you have to remember is the
following quick checklist:</p>
<ol class="arabic simple">
<li>the <cite>Flask</cite> application object creation has to be in the
<cite>__init__.py</cite> file. That way each module can import it safely and the
<cite>__name__</cite> variable will resolve to the correct package.</li>
<li>all the view functions (the ones with a <a class="reference internal" href="../api.html#flask.Flask.route" title="flask.Flask.route"><tt class="xref py py-meth docutils literal"><span class="pre">route()</span></tt></a>
decorator on top) have to be imported when in the <cite>__init__.py</cite> file.
Not the object itself, but the module it is in. Import the view module
<strong>after the application object is created</strong>.</li>
</ol>
<p>Here’s an example <cite>__init__.py</cite>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">flask</span> <span class="kn">import</span> <span class="n">Flask</span>
<span class="n">app</span> <span class="o">=</span> <span class="n">Flask</span><span class="p">(</span><span class="n">__name__</span><span class="p">)</span>
<span class="kn">import</span> <span class="nn">yourapplication.views</span>
</pre></div>
</div>
<p>And this is what <cite>views.py</cite> would look like:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">yourapplication</span> <span class="kn">import</span> <span class="n">app</span>
<span class="nd">@app.route</span><span class="p">(</span><span class="s">'/'</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">index</span><span class="p">():</span>
<span class="k">return</span> <span class="s">'Hello World!'</span>
</pre></div>
</div>
<p>You should then end up with something like that:</p>
<div class="highlight-python"><pre>/yourapplication
/runserver.py
/yourapplication
/__init__.py
/views.py
/static
/style.css
/templates
layout.html
index.html
login.html
...</pre>
</div>
<div class="admonition-circular-imports admonition ">
<p class="first admonition-title">Circular Imports</p>
<p>Every Python programmer hates them, and yet we just added some:
circular imports (That’s when two modules depend on each other. In this
case <cite>views.py</cite> depends on <cite>__init__.py</cite>). Be advised that this is a
bad idea in general but here it is actually fine. The reason for this is
that we are not actually using the views in <cite>__init__.py</cite> and just
ensuring the module is imported and we are doing that at the bottom of
the file.</p>
<p class="last">There are still some problems with that approach but if you want to use
decorators there is no way around that. Check out the
<a class="reference internal" href="../becomingbig.html#becomingbig"><em>Becoming Big</em></a> section for some inspiration how to deal with that.</p>
</div>
</div>
<div class="section" id="working-with-blueprints">
<span id="working-with-modules"></span><h2>Working with Blueprints<a class="headerlink" href="#working-with-blueprints" title="Permalink to this headline">¶</a></h2>
<p>If you have larger applications it’s recommended to divide them into
smaller groups where each group is implemented with the help of a
blueprint. For a gentle introduction into this topic refer to the
<a class="reference internal" href="../blueprints.html#blueprints"><em>Modular Applications with Blueprints</em></a> chapter of the documentation.</p>
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<h3><a href="../index.html">Table Of Contents</a></h3>
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<li><a class="reference internal" href="#">Larger Applications</a><ul>
<li><a class="reference internal" href="#simple-packages">Simple Packages</a></li>
<li><a class="reference internal" href="#working-with-blueprints">Working with Blueprints</a></li>
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<li><a href="index.html">Patterns for Flask</a><ul>
<li>Previous: <a href="index.html" title="previous chapter">Patterns for Flask</a></li>
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