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<section id="controlling-user-variables-in-an-expression-from-python">
<h1>Controlling user variables in an expression from python<a class="headerlink" href="#controlling-user-variables-in-an-expression-from-python" title="Permalink to this heading">¶</a></h1>
<p><strong>06-var-function.py</strong></p>
<p>User variables are created with the keyword <cite>var</cite>:</p>
<div class="highlight-scheme notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="nf">var</span><span class="w"> </span><span class="o">#</span><span class="nv">var</span><span class="w"> </span><span class="p">(</span><span class="nf">init</span><span class="p">))</span><span class="w"></span>
</pre></div>
</div>
<p>The variable name must begin with a <cite>#</cite>.</p>
<p>They are computed only at initialization, but can be changed from the
python script with method calls (<cite>varname</cite> is a string and <cite>value</cite> is a
float):</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">obj</span><span class="o">.</span><span class="n">setVar</span><span class="p">(</span><span class="n">varname</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>
</pre></div>
</div>
<p>The following example illustrates a self-modulated oscillator of which
the frequency and the feedback are controlled from the python side with
method calls.</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="n">expression</span> <span class="o">=</span> <span class="s2">"""</span>
<span class="s2">(var #pitch 200)</span>
<span class="s2">(var #feed 0.5)</span>
<span class="s2">(define oscloop (</span>
<span class="s2"> (let #xsin</span>
<span class="s2"> (sin (+ (* twopi (~ $1)) (* #xsin $2))) // #xsin used before...</span>
<span class="s2"> ) // ... "let" statement finished = one-delay feedback loop!</span>
<span class="s2"> #xsin // oscloop function outputs #xsin variable</span>
<span class="s2"> )</span>
<span class="s2">)</span>
<span class="s2">(oscloop #pitch #feed)</span>
<span class="s2">"""</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">expr</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">Expr</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">Sig</span></a><span class="p">(</span><span class="mi">0</span><span class="p">),</span> <span class="n">expression</span><span class="p">,</span> <span class="n">mul</span><span class="o">=</span><span class="mf">0.5</span><span class="p">)</span>
<span class="n">expr</span><span class="o">.</span><span class="n">editor</span><span class="p">()</span>
<span class="c1"># Shows two sliders, one for the frequency and one for the feedback parameter.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">pit</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">Sig</span></a><span class="p">(</span><span class="mi">200</span><span class="p">)</span>
<span class="n">pit</span><span class="o">.</span><span class="n">ctrl</span><span class="p">([</span><a class="sphinx-codeautolink-a" href="../../api/classes/map.html#pyo.SLMap" title="pyo.lib._maps.SLMap"><span class="n">SLMap</span></a><span class="p">(</span><span class="mi">100</span><span class="p">,</span> <span class="mi">1000</span><span class="p">,</span> <span class="s2">"log"</span><span class="p">,</span> <span class="s2">"value"</span><span class="p">,</span> <span class="mi">200</span><span class="p">)],</span> <span class="n">title</span><span class="o">=</span><span class="s2">"Frequency"</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">feed</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">Sig</span></a><span class="p">(</span><span class="mf">0.5</span><span class="p">)</span>
<span class="n">feed</span><span class="o">.</span><span class="n">ctrl</span><span class="p">([</span><a class="sphinx-codeautolink-a" href="../../api/classes/map.html#pyo.SLMap" title="pyo.lib._maps.SLMap"><span class="n">SLMap</span></a><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="s2">"lin"</span><span class="p">,</span> <span class="s2">"value"</span><span class="p">,</span> <span class="mf">0.5</span><span class="p">)],</span> <span class="n">title</span><span class="o">=</span><span class="s2">"Feedback"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">change</span><span class="p">():</span>
<span class="s2">"Sends new values to user variables in the expression."</span>
<span class="n">expr</span><span class="o">.</span><span class="n">setVar</span><span class="p">([</span><span class="s2">"#pitch"</span><span class="p">,</span> <span class="s2">"#feed"</span><span class="p">],</span> <span class="p">[</span><span class="n">pit</span><span class="o">.</span><span class="n">get</span><span class="p">(),</span> <span class="n">feed</span><span class="o">.</span><span class="n">get</span><span class="p">()])</span>
<span class="c1"># Calls the change() function every 20 ms to update the user variables.</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">change</span><span class="p">,</span> <span class="mf">0.025</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/analysis.html#pyo.Scope" title="pyo.lib.analysis.Scope"><span class="n">sc</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/analysis.html#pyo.Scope" title="pyo.lib.analysis.Scope"><span class="n">Scope</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">expr</span></a><span class="p">)</span>
<span class="n">pan</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pan.html#pyo.Pan" title="pyo.lib.pan.Pan"><span class="n">Pan</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">expr</span></a><span class="p">)</span><span class="o">.</span><span class="n">out</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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