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<section id="delayed-calls-py-calling-a-function-once-after-a-given-delay">
<h1>03-delayed-calls.py - Calling a function once, after a given delay.<a class="headerlink" href="#delayed-calls-py-calling-a-function-once-after-a-given-delay" title="Permalink to this heading">¶</a></h1>
<p>If you want to setup a callback once in the future, the CallAfter
object is very easy to use. You just give it the function name, the
time to wait before making the call and an optional argument.</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="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 four-streams oscillator to produce a chord.</span>
<span class="n">amp</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">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">0.2</span><span class="p">)</span><span class="o">.</span><span class="n">play</span><span class="p">()</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.SineLoop" title="pyo.lib.generators.SineLoop"><span class="n">osc</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.SineLoop" title="pyo.lib.generators.SineLoop"><span class="n">SineLoop</span></a><span class="p">(</span><span class="n">freq</span><span class="o">=</span><span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">],</span> <span class="n">feedback</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="n">amp</span><span class="p">)</span>
<span class="n">rev</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/effects.html#pyo.WGVerb" title="pyo.lib.effects.WGVerb"><span class="n">WGVerb</span></a><span class="p">(</span><span class="n">osc</span><span class="o">.</span><span class="n">mix</span><span class="p">(</span><span class="mi">2</span><span class="p">),</span> <span class="n">feedback</span><span class="o">=</span><span class="mf">0.8</span><span class="p">,</span> <span class="n">cutoff</span><span class="o">=</span><span class="mi">4000</span><span class="p">,</span> <span class="n">bal</span><span class="o">=</span><span class="mf">0.2</span><span class="p">)</span><span class="o">.</span><span class="n">out</span><span class="p">()</span>

<span class="c1"># A function to change the oscillator's frequencies and start the envelope.</span>
<span class="k">def</span> <span class="nf">set_osc_freqs</span><span class="p">(</span><span class="n">notes</span><span class="p">):</span>
    <span class="nb">print</span><span class="p">(</span><span class="n">notes</span><span class="p">)</span>
    <span class="n">osc</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="n">attr</span><span class="o">=</span><span class="s2">"freq"</span><span class="p">,</span> <span class="n">value</span><span class="o">=</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="nb">list</span><span class="p">(</span><span class="n">notes</span><span class="p">)),</span> <span class="n">port</span><span class="o">=</span><span class="mf">0.005</span><span class="p">)</span>
    <span class="n">amp</span><span class="o">.</span><span class="n">play</span><span class="p">()</span>


<span class="c1"># Initial chord.</span>
<span class="n">set_osc_freqs</span><span class="p">([</span><span class="mi">60</span><span class="p">,</span> <span class="mi">64</span><span class="p">,</span> <span class="mi">67</span><span class="p">,</span> <span class="mi">72</span><span class="p">])</span>

<span class="c1"># We must be sure that our CallAfter object stays alive as long as</span>
<span class="c1"># it waits to call its function. If we don't keep a reference to it,</span>
<span class="c1"># it will be garbage-collected before doing its job.</span>
<span class="n">call</span> <span class="o">=</span> <span class="kc">None</span>


<span class="k">def</span> <span class="nf">new_notes</span><span class="p">(</span><span class="n">notes</span><span class="p">):</span>
    <span class="k">global</span> <span class="n">call</span>  <span class="c1"># Use a global variable.</span>
    <span class="n">amp</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>  <span class="c1"># Start the fadeout of the current notes...</span>
    <span class="c1"># ... then, 50 ms later, call the function that change the frequencies.</span>
    <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">call</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">CallAfter</span></a><span class="p">(</span><span class="n">set_osc_freqs</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">0.05</span><span class="p">,</span> <span class="n">arg</span><span class="o">=</span><span class="n">notes</span><span class="p">)</span>


<span class="c1"># The sequence of events. We use a tuple for the list of frequencies</span>
<span class="c1"># because PyoObjects spread lists as argument over all their internal</span>
<span class="c1"># streams. This means that with a list of frequencies, only the first</span>
<span class="c1"># frequency would be passed to the callback of the first (and single)</span>
<span class="c1"># stream (a list of functions at first argument would create a</span>
<span class="c1"># multi-stream object). A tuple is treated as a single argument.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">c1</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">CallAfter</span></a><span class="p">(</span><span class="n">new_notes</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">0.95</span><span class="p">,</span> <span class="n">arg</span><span class="o">=</span><span class="p">(</span><span class="mi">60</span><span class="p">,</span> <span class="mi">64</span><span class="p">,</span> <span class="mi">67</span><span class="p">,</span> <span class="mi">69</span><span class="p">))</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">c2</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">CallAfter</span></a><span class="p">(</span><span class="n">new_notes</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">1.95</span><span class="p">,</span> <span class="n">arg</span><span class="o">=</span><span class="p">(</span><span class="mi">60</span><span class="p">,</span> <span class="mi">65</span><span class="p">,</span> <span class="mi">69</span><span class="p">,</span> <span class="mi">76</span><span class="p">))</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">c3</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">CallAfter</span></a><span class="p">(</span><span class="n">new_notes</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">2.95</span><span class="p">,</span> <span class="n">arg</span><span class="o">=</span><span class="p">(</span><span class="mi">62</span><span class="p">,</span> <span class="mi">65</span><span class="p">,</span> <span class="mi">69</span><span class="p">,</span> <span class="mi">74</span><span class="p">))</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">c4</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">CallAfter</span></a><span class="p">(</span><span class="n">new_notes</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">3.45</span><span class="p">,</span> <span class="n">arg</span><span class="o">=</span><span class="p">(</span><span class="mi">59</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">74</span><span class="p">))</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">c5</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">CallAfter</span></a><span class="p">(</span><span class="n">new_notes</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">3.95</span><span class="p">,</span> <span class="n">arg</span><span class="o">=</span><span class="p">(</span><span class="mi">60</span><span class="p">,</span> <span class="mi">64</span><span class="p">,</span> <span class="mi">67</span><span class="p">,</span> <span class="mi">72</span><span class="p">))</span>
<span class="c1"># The last event activates the fadeout of the amplitude envelope.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">c6</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.CallAfter" title="pyo.lib.pattern.CallAfter"><span class="n">CallAfter</span></a><span class="p">(</span><span class="n">amp</span><span class="o">.</span><span class="n">stop</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">5.95</span><span class="p">,</span> <span class="n">arg</span><span class="o">=</span><span class="kc">None</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>
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