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Add __str__ example
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‎notebooks/beginner/classes.ipynb‎

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" "
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### `__str__()`\n",
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"`__str__()` is a special method which is called when an instance of the class is converted to string (e.g. when you want to print the instance). In other words, by defining `__str__` method for your class, you can decide what's the printable version of the instances of your class. The method should return a string."
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"class Person:\n",
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" def __init__(self, name, age):\n",
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" self.name = name\n",
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" self.age = age\n",
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" \n",
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" def __str__(self):\n",
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" return 'Person: {}'.format(self.name)\n",
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" \n",
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"jack = Person('Jack', 82)\n",
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"print('This is the string presentation of jack: {}'.format(jack))"
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]
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},
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‎notebooks/beginner/html/classes.html‎

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<pre>my_intance: &lt;__main__.MyFirstClass object at 0x106a164a8&gt;
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<pre>my_intance: &lt;__main__.MyFirstClass object at 0x106918550&gt;
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type: &lt;class &#39;__main__.MyFirstClass&#39;&gt;
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my_instance.name: John Doe
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</pre>
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<h2 id="Class-variables-vs-instance-variables">Class variables vs instance variables<a class="anchor-link" href="#Class-variables-vs-instance-variables">&#182;</a></h2><p>Class variables are shared between all the instances of that class whereas instance variables can hold different values between different instances of that class.</p>
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<h3 id="__str__()"><code>__str__()</code><a class="anchor-link" href="#__str__()">&#182;</a></h3><p><code>__str__()</code> is a special method which is called when an instance of the class is converted to string (e.g. when you want to print the instance). In other words, by defining <code>__str__</code> method for your class, you can decide what's the printable version of the instances of your class. The method should return a string.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">class</span> <span class="nc">Person</span><span class="p">:</span>
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<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">age</span><span class="p">):</span>
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<span class="bp">self</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="n">name</span>
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<span class="bp">self</span><span class="o">.</span><span class="n">age</span> <span class="o">=</span> <span class="n">age</span>
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<span class="k">def</span> <span class="nf">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
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<span class="k">return</span> <span class="s1">&#39;Person: </span><span class="si">{}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">)</span>
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<span class="n">jack</span> <span class="o">=</span> <span class="n">Person</span><span class="p">(</span><span class="s1">&#39;Jack&#39;</span><span class="p">,</span> <span class="mi">82</span><span class="p">)</span>
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<span class="nb">print</span><span class="p">(</span><span class="s1">&#39;This is the string presentation of jack: </span><span class="si">{}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">jack</span><span class="p">))</span>
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</pre></div>
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<pre>This is the string presentation of jack: Person: Jack
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</pre>
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<h2 id="Class-variables-vs-instance-variables">Class variables vs instance variables<a class="anchor-link" href="#Class-variables-vs-instance-variables">&#182;</a></h2><p>Class variables are shared between all the instances of that class whereas instance variables can hold different values between different instances of that class.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">class</span> <span class="nc">Example</span><span class="p">:</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">class</span> <span class="nc">Person</span><span class="p">:</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">class</span> <span class="nc">Person</span><span class="p">:</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">class</span> <span class="nc">Animal</span><span class="p">:</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">dog</span> <span class="o">=</span> <span class="n">Dog</span><span class="p">()</span>

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