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<div class="section" id="variables">
<h1>Variablen<a class="headerlink" href="#variables" title="Link zu dieser Überschrift">¶</a></h1>
<div class="section" id="introduction">
<h2>Einführung<a class="headerlink" href="#introduction" title="Link zu dieser Überschrift">¶</a></h2>
<p>Puh. Wenn Du mit den Winkeln experimentierst, musst Du jedes Mal an drei verschiedenen Stellen den Code verändern. Jetzt stelle Dir vor Du möchtest mit allen Abmessungen des Quadrates experimentieren, oder sogar mit Rechtecken! Das muss besser gehen.</p>
<p>An dieser Stelle kommen <strong>Variablen</strong> ins Spiel: Du kannst ab nun Python befehlen, jedes Mal wenn Du eine bestimmte Variable verwendest, an dieser Stelle etwas anderes einzusetzen. Dieses Konzept ist ähnlich zur Algebra, wo Du schreiben könntest: <em>x sei 5</em>. Dann ist <em>x * 2</em> natürlich <em>10</em>.</p>
<p>In der Syntax von Python hat die gleiche Bedeutung:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">x</span> <span class="o">=</span> <span class="mi">5</span>
</pre></div>
</div>
<p>Falls Du nach diesem Befehl <code class="docutils literal"><span class="pre">print(x)</span></code> ausführst, wird der Wert von x ausgegeben — 5. Du kannst das gleiche auch mit turtle kombinieren.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">turtle</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
</pre></div>
</div>
<p>Variablen können alles mögliche speichern, nicht nur Zahlen. Etwas anderes typisches das oft in Variablen gespeichert wird sind <strong>Strings</strong> - Textzeilen. Strings werden durch <code class="docutils literal"><span class="pre">"</span></code> (doppelte Anführungszeichen) vor und nach dem Text gekennzeichnet. Du wirst später noch mehr über diese sogenannten Datentypen in Python und was Du mit ihnen tun kannst, lernen.</p>
<p>Du kannst sogar eine Variable verwenden um der Schildkröte einen Namen zu geben:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">timmy</span> <span class="o">=</span> <span class="n">turtle</span>
</pre></div>
</div>
<p>Jedes Mal wenn Du nun <code class="docutils literal"><span class="pre">timmy</span></code> schreibst, weiß Python, dass Du <code class="docutils literal"><span class="pre">turtle</span></code> meinst. Du kannst auch weiterhin <code class="docutils literal"><span class="pre">turtle</span></code> verwenden:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">timmy</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span>
<span class="n">timmy</span><span class="o">.</span><span class="n">left</span><span class="p">(</span><span class="mi">90</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="a-variable-called-angle">
<h2>Eine Variable genannt angle<a class="headerlink" href="#a-variable-called-angle" title="Link zu dieser Überschrift">¶</a></h2>
<div class="section" id="exercise">
<h3>Übung<a class="headerlink" href="#exercise" title="Link zu dieser Überschrift">¶</a></h3>
<p>Wenn wir eine Variable <code class="docutils literal"><span class="pre">angle</span></code> (Winkel) nennen, wie könnten wir sie verwenden um mit dem Programm mit den gekippten Quadraten zu experimentieren?</p>
</div>
<div class="solution section" id="solution">
<h3>Lösung<a class="headerlink" href="#solution" title="Link zu dieser Überschrift">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre><span class="n">angle</span> <span class="o">=</span> <span class="mi">20</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">left</span><span class="p">(</span><span class="n">angle</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">left</span><span class="p">(</span><span class="mi">90</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">left</span><span class="p">(</span><span class="mi">90</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">left</span><span class="p">(</span><span class="mi">90</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">forward</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">left</span><span class="p">(</span><span class="mi">90</span><span class="p">)</span>
<span class="n">turtle</span><span class="o">.</span><span class="n">left</span><span class="p">(</span><span class="n">angle</span><span class="p">)</span>
</pre></div>
</div>
<p>... und so weiter</p>
</div>
<div class="section" id="bonus">
<h3>Bonus<a class="headerlink" href="#bonus" title="Link zu dieser Überschrift">¶</a></h3>
<p>Kannst Du das gleiche Prinzip auch auf die Grösse der Quadrate anwenden?</p>
</div>
</div>
<div class="section" id="the-house-of-santa-claus">
<h2>Das Haus vom Nikolaus<a class="headerlink" href="#the-house-of-santa-claus" title="Link zu dieser Überschrift">¶</a></h2>
<div class="section" id="id1">
<h3>Übung<a class="headerlink" href="#id1" title="Link zu dieser Überschrift">¶</a></h3>
<p>Zeichne ein Haus.</p>
<img alt="_images/house.png" src="_images/house.png" />
<p>Du kannst die Länge der diagonalen Linie mit dem Satz des Pythagoras ausrechnen. Diese Zahl ist es wert in einer Variable gespeichert zu werden. Um die Quadratwurzel einer Zahl in Python zu berechnen, musst Du das <em>math</em> Modul importieren und die Funktion <code class="docutils literal"><span class="pre">math.sqrt()</span></code> aufrufen. Das Quadrat einer Zahl kannst Du mit dem Operator <code class="docutils literal"><span class="pre">**</span></code> ausrechnen:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">math</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">math</span><span class="o">.</span><span class="n">sqrt</span><span class="p">(</span><span class="n">a</span><span class="o">**</span><span class="mi">2</span> <span class="o">+</span> <span class="n">b</span><span class="o">**</span><span class="mi">2</span><span class="p">)</span>
</pre></div>
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