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<section id="periodic-calls-py-periodic-event-generation">
<h1>01-periodic-calls.py - Periodic event generation.<a class="headerlink" href="#periodic-calls-py-periodic-event-generation" title="Permalink to this heading">¶</a></h1>
<p>When an audio thread is running, the user must take care of
not freezing the interpreter lock by using blocking function
like sleep(). It is better to use objects from the library
that are designed to call a function without blocking the
interpreter. Because these objects are aware of the server’s
timeline, they are well suited for generating rhythmic
sequences of functions calls.</p>
<p>Pyo offers three objects for calling function:</p>
<ul class="simple">
<li><p>Pattern: Periodically calls a Python function.</p></li>
<li><p>Score: Calls functions by incrementation of a preformatted name.</p></li>
<li><p>CallAfter: Calls a Python function after a given time.</p></li>
</ul>
<p>This example shows the usage of the Pattern object to create a
sequence of audio events.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <a class="sphinx-codeautolink-a" href="../../api/alphabetical.html#module-pyo" title="pyo"><span class="nn">pyo</span></a> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">import</span> <span class="nn">random</span>

<span class="n">s</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/server.html#pyo.Server" title="pyo.lib.server.Server"><span class="n">Server</span></a><span class="p">()</span><span class="o">.</span><span class="n">boot</span><span class="p">()</span>

<span class="c1"># A small instrument to play the events emitted by the function call.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Fader" title="pyo.lib.controls.Fader"><span class="n">amp</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Fader" title="pyo.lib.controls.Fader"><span class="n">Fader</span></a><span class="p">(</span><span class="n">fadein</span><span class="o">=</span><span class="mf">0.005</span><span class="p">,</span> <span class="n">fadeout</span><span class="o">=</span><span class="mf">0.05</span><span class="p">,</span> <span class="n">mul</span><span class="o">=</span><span class="mf">0.15</span><span class="p">)</span>
<span class="n">osc</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.RCOsc" title="pyo.lib.generators.RCOsc"><span class="n">RCOsc</span></a><span class="p">(</span><span class="n">freq</span><span class="o">=</span><span class="p">[</span><span class="mi">100</span><span class="p">,</span> <span class="mi">100</span><span class="p">],</span> <span class="n">mul</span><span class="o">=</span><a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Fader" title="pyo.lib.controls.Fader"><span class="n">amp</span></a><span class="p">)</span><span class="o">.</span><span class="n">out</span><span class="p">()</span>
<span class="n">dly</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/effects.html#pyo.Delay" title="pyo.lib.effects.Delay"><span class="n">Delay</span></a><span class="p">(</span><span class="n">osc</span><span class="p">,</span> <span class="n">delay</span><span class="o">=</span><span class="mf">1.0</span><span class="p">,</span> <span class="n">feedback</span><span class="o">=</span><span class="mf">0.5</span><span class="p">)</span><span class="o">.</span><span class="n">out</span><span class="p">()</span>


<span class="k">def</span> <span class="nf">new_event</span><span class="p">():</span>
    <span class="c1"># Choose a duration for this event.</span>
    <span class="n">dur</span> <span class="o">=</span> <span class="n">random</span><span class="o">.</span><span class="n">choice</span><span class="p">([</span><span class="mf">0.125</span><span class="p">,</span> <span class="mf">0.125</span><span class="p">,</span> <span class="mf">0.125</span><span class="p">,</span> <span class="mf">0.25</span><span class="p">,</span> <span class="mf">0.25</span><span class="p">,</span> <span class="mf">0.5</span><span class="p">,</span> <span class="mi">1</span><span class="p">])</span>

    <span class="c1"># Assigns the new duration to the envelope.</span>
    <span class="n">amp</span><span class="o">.</span><span class="n">dur</span> <span class="o">=</span> <span class="n">dur</span>
    <span class="c1"># Assigns the new duration to the caller, thus the next function call</span>
    <span class="c1"># will be only after the current event has finished.</span>
    <span class="n">pat</span><span class="o">.</span><span class="n">time</span> <span class="o">=</span> <span class="n">dur</span>

    <span class="c1"># Choose a new frequency.</span>
    <span class="n">freq</span> <span class="o">=</span> <span class="n">random</span><span class="o">.</span><span class="n">choice</span><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/functions/conv.html#pyo.midiToHz" title="pyo.midiToHz"><span class="n">midiToHz</span></a><span class="p">([</span><span class="mi">60</span><span class="p">,</span> <span class="mi">62</span><span class="p">,</span> <span class="mi">63</span><span class="p">,</span> <span class="mi">65</span><span class="p">,</span> <span class="mi">67</span><span class="p">,</span> <span class="mi">68</span><span class="p">,</span> <span class="mi">71</span><span class="p">,</span> <span class="mi">72</span><span class="p">]))</span>

    <span class="c1"># Replace oscillator's frequencies.</span>
    <span class="n">osc</span><span class="o">.</span><span class="n">freq</span> <span class="o">=</span> <span class="p">[</span><span class="n">freq</span><span class="p">,</span> <span class="n">freq</span> <span class="o">*</span> <span class="mf">1.003</span><span class="p">]</span>

    <span class="c1"># Start the envelope.</span>
    <span class="n">amp</span><span class="o">.</span><span class="n">play</span><span class="p">()</span>


<span class="c1"># A Pattern object periodically call the referred function given as</span>
<span class="c1"># argument. The "time" argument is the delay between successive calls.</span>
<span class="c1"># The play() method must be explicitly called for a Pattern object</span>
<span class="c1"># to start its processing loop.</span>
<span class="n">pat</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.Pattern" title="pyo.lib.pattern.Pattern"><span class="n">Pattern</span></a><span class="p">(</span><span class="n">function</span><span class="o">=</span><span class="n">new_event</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">0.25</span><span class="p">)</span><span class="o">.</span><span class="n">play</span><span class="p">()</span>

<span class="n">s</span><span class="o">.</span><span class="n">gui</span><span class="p">(</span><span class="nb">locals</span><span class="p">())</span>
</pre></div>
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