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Travis CI ac0a1f4c4f Site updated at 2017-02-23 10:14:06 UTC
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<h1 class="title indent">
Basic State Setting Example
</h1>
</header>
<hr class="divider">
<p>This is a simple tutorial/example on how to write a component for <a href="https://home-assistant.io/">Home Assistant</a>. We will work on a component called “hello_state” to begin with. The purpose of this component is to display a given text in the frontend.</p>
<p>The setup of a development environment is described in the <a href="/developers/#starting-development">Developers section</a> of the documentation.</p>
<h2><a class="title-link" name="component" href="#component"></a> Component</h2>
<p>To get started, create the file <code class="highlighter-rouge">&lt;config dir&gt;/custom_components/hello_state.py</code> and copy the below example code.</p>
<div class="language-python highlighter-rouge"><pre class="highlight"><code><span class="s">"""
Support for showing text in the frontend.
For more details about this component, please refer to the documentation at
https://home-assistant.io/components/hello_state/
"""</span>
<span class="kn">import</span> <span class="nn">logging</span>
<span class="n">_LOGGER</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="n">__name__</span><span class="p">)</span>
<span class="n">DOMAIN</span> <span class="o">=</span> <span class="s">'hello_state'</span>
<span class="n">DEPENDENCIES</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">def</span> <span class="nf">setup</span><span class="p">(</span><span class="n">hass</span><span class="p">,</span> <span class="n">config</span><span class="o">=</span><span class="bp">None</span><span class="p">):</span>
<span class="s">"""Setup the Hello State component. """</span>
<span class="n">_LOGGER</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s">"The 'hello state' component is ready!"</span><span class="p">)</span>
<span class="k">return</span> <span class="bp">True</span>
</code></pre>
</div>
<ol>
<li>In the file header we decided to add some details: A short description and the link to the documentation.</li>
<li>We want to do some logging. This means that we import the Python logging module and create an alias.</li>
<li>The component name is equal to the domain name.</li>
<li>At the moment this component has no dependencies. For detail check <a href="/developers/creating_components/#dependencies">dependencies</a> section.</li>
<li>
<p>The <code class="highlighter-rouge">setup</code> function will take care of the initialization of our component.
The component will only write a log message. Keep in mind for later that you have several options for the severity:</p>
<ul>
<li><code class="highlighter-rouge">_LOGGER.info(msg)</code></li>
<li><code class="highlighter-rouge">_LOGGER.warning(msg)</code></li>
<li><code class="highlighter-rouge">_LOGGER.error(msg)</code></li>
<li><code class="highlighter-rouge">_LOGGER.critical(msg)</code></li>
<li><code class="highlighter-rouge">_LOGGER.exception(msg)</code></li>
</ul>
</li>
<li>We return <code class="highlighter-rouge">True</code> if everything is ok.</li>
</ol>
<p>Add the component to your <code class="highlighter-rouge">configuration.yaml</code> file.</p>
<div class="language-yaml highlighter-rouge"><pre class="highlight"><code><span class="s">hello_state</span><span class="pi">:</span>
</code></pre>
</div>
<p>After a start or a restart of Home Assistant the component will create an entry in the log.</p>
<div class="language-bash highlighter-rouge"><pre class="highlight"><code>16-03-12 14:16:42 INFO <span class="o">(</span>MainThread<span class="o">)</span> <span class="o">[</span>custom_components.hello_state] The <span class="s1">'hello state'</span> component is ready!
</code></pre>
</div>
<p>The next step is the introduction of configuration options. Most configuration details are coming out of the <code class="highlighter-rouge">configuration.yaml</code> file. To do that we need to update the <code class="highlighter-rouge">def setup()</code> method to accept configuration information and access the configuration variable in the <code class="highlighter-rouge">setup</code> method.</p>
<p>More details about this topic can be found in the <a href="/developers/creating_components/#config-user-given-configuration">User given configuration</a> section.</p>
<div class="language-python highlighter-rouge"><pre class="highlight"><code><span class="kn">import</span> <span class="nn">logging</span>
<span class="n">_LOGGER</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="n">__name__</span><span class="p">)</span>
<span class="n">DOMAIN</span> <span class="o">=</span> <span class="s">'hello_state'</span>
<span class="n">DEPENDENCIES</span> <span class="o">=</span> <span class="p">[]</span>
<span class="n">CONF_TEXT</span> <span class="o">=</span> <span class="s">'text'</span>
<span class="n">DEFAULT_TEXT</span> <span class="o">=</span> <span class="s">'No text!'</span>
<span class="k">def</span> <span class="nf">setup</span><span class="p">(</span><span class="n">hass</span><span class="p">,</span> <span class="n">config</span><span class="p">):</span>
<span class="s">"""Setup the Hello State component. """</span>
<span class="c"># Get the text from the configuration. Use DEFAULT_TEXT if no name is provided.</span>
<span class="n">text</span> <span class="o">=</span> <span class="n">config</span><span class="p">[</span><span class="n">DOMAIN</span><span class="p">]</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">CONF_TEXT</span><span class="p">,</span> <span class="n">DEFAULT_TEXT</span><span class="p">)</span>
<span class="c"># States are in the format DOMAIN.OBJECT_ID</span>
<span class="n">hass</span><span class="o">.</span><span class="n">states</span><span class="o">.</span><span class="nb">set</span><span class="p">(</span><span class="s">'hello_state.Hello_State'</span><span class="p">,</span> <span class="n">text</span><span class="p">)</span>
<span class="k">return</span> <span class="bp">True</span>
</code></pre>
</div>
<p>To add the latest feature of our component, update the entry in your <code class="highlighter-rouge">configuration.yaml</code> file.</p>
<div class="language-yaml highlighter-rouge"><pre class="highlight"><code><span class="s">hello_state</span><span class="pi">:</span>
<span class="s">text</span><span class="pi">:</span> <span class="s1">'</span><span class="s">Hello,</span><span class="nv"> </span><span class="s">World!'</span>
</code></pre>
</div>
<p>Thanks to <code class="highlighter-rouge">DEFAULT_TEXT</code> variable the component will launch even if no <code class="highlighter-rouge">text:</code> field is used in the <code class="highlighter-rouge">configuration.yaml</code> file. Quite often there are variables which are required. It’s important to check if all mandatory configuration variables are provided. If not, the setup should fail. We will use <code class="highlighter-rouge">voluptuous</code> as a helper to achive this. The next listing shows the essential parts.</p>
<div class="language-python highlighter-rouge"><pre class="highlight"><code><span class="kn">import</span> <span class="nn">voluptuous</span> <span class="kn">as</span> <span class="nn">vol</span>
<span class="kn">import</span> <span class="nn">homeassistant.helpers.config_validation</span> <span class="kn">as</span> <span class="nn">cv</span>
<span class="p">[</span><span class="o">...</span><span class="p">]</span>
<span class="n">PLATFORM_SCHEMA</span> <span class="o">=</span> <span class="n">PLATFORM_SCHEMA</span><span class="o">.</span><span class="n">extend</span><span class="p">({</span>
<span class="n">vol</span><span class="o">.</span><span class="n">Required</span><span class="p">(</span><span class="n">CONF_TEXT</span><span class="p">):</span> <span class="n">cv</span><span class="o">.</span><span class="n">string</span><span class="p">,</span>
<span class="p">})</span>
</code></pre>
</div>
<p>If <code class="highlighter-rouge">text:</code> is missing, there will be a warning in the log file.</p>
<p>After a start or a restart of Home Assistant the component will be visible in the frontend if the <code class="highlighter-rouge">configuration.yaml</code> file is up-to-date.</p>
<p class="img">
<img src="/images/screenshots/create-component01.png" />
</p>
<p>To get your component included in the Home Assistant releases, follow the steps described in the <a href="https://home-assistant.io/developers/#submitting-improvements">Submitting improvements</a> section. Basically you only need to move your component in the <code class="highlighter-rouge">homeassistant/component/</code> directory of your fork and create a Pull Request.</p>
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<h1 class="title delta">Custom Python Component Examples</h1>
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<li>
<a href='/cookbook/python_component_basic_service/'>Basic Service Example</a>
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Basic State Setting Example
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