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</style></head><body style="overflow: auto;"><div tabindex="2" class="cell text_cell border-box-sizing ui-widget-content ui-corner-all"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 3px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Object-Oriented Programming</h1>
<h2>Basic class operations ("glorified struct")</h2></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [1]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 100px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>class MyClass(object):</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">class</span><span class="cm-null"> </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-builtin">object</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">a</span><span class="cm-null"> = </span><span class="cm-number">5</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">b</span><span class="cm-null"> = </span><span class="cm-number">6</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">MyClass</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">MyClass.a</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre><class '__main__.MyClass'>
5</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [3]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>obj = MyClass()</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">obj</span><span class="cm-null"> = </span><span class="cm-variable">MyClass</span><span class="cm-null">()</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj.a</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj.b</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>5
6</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [4]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>obj.a = 'new value for a'</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">obj.a</span><span class="cm-null"> = </span><span class="cm-string">'new value for a'</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj.a</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>new value for a</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [5]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print MyClass.a</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">MyClass.a</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>5</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h1>Basic methods</h1></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [9]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 65px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> print 'MyClass says', something</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">class</span><span class="cm-null"> </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-builtin">object</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">say</span><span class="cm-null">(</span><span class="cm-variable">self</span><span class="cm-null">, </span><span class="cm-variable">something</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-string">'MyClass says'</span><span class="cm-null">, </span><span class="cm-variable">something</span></pre></div></div></div></div></div></div></div></div></div><div style="display: none;" class="output vbox"></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [11]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 47px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>myobj.say('Hello')</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-variable">myobj</span><span class="cm-null"> = </span><span class="cm-variable">MyClass</span><span class="cm-null">()</span></pre><pre><span class="cm-variable">myobj.say</span><span class="cm-null">(</span><span class="cm-string">'Hello'</span><span class="cm-null">)</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>MyClass says Hello</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [14]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 170px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>obj = MyClass('avalue', 'bvalue')</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-comment"># Classes can have a constructor</span></pre><pre> </pre><pre><span class="cm-keyword">class</span><span class="cm-null"> </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-builtin">object</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">__init__</span><span class="cm-null">(</span><span class="cm-variable">self</span><span class="cm-null">, </span><span class="cm-variable">a</span><span class="cm-null">, </span><span class="cm-variable">b</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">self.a</span><span class="cm-null"> = </span><span class="cm-variable">a</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">self.b</span><span class="cm-null"> = </span><span class="cm-variable">b</span></pre><pre><span class="cm-null"> </span></pre><pre><span class="cm-variable">obj</span><span class="cm-null"> = </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-string">'avalue'</span><span class="cm-null">, </span><span class="cm-string">'bvalue'</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj.a</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>avalue</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 4px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h2>Method access and visibility</h2>
<p>By convention, a single leading underscore indicates that a method or variable is
"protected" and should not be modified outside the class:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [16]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 188px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>obj = MyClass('avalue', 'bvalue')</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">class</span><span class="cm-null"> </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-builtin">object</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">__init__</span><span class="cm-null">(</span><span class="cm-variable">self</span><span class="cm-null">, </span><span class="cm-variable">a</span><span class="cm-null">, </span><span class="cm-variable">b</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">self._a</span><span class="cm-null"> = </span><span class="cm-variable">a</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">self._b</span><span class="cm-null"> = </span><span class="cm-variable">b</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">value</span><span class="cm-null">(</span><span class="cm-variable">self</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">return</span><span class="cm-null"> </span><span class="cm-variable">self._a</span><span class="cm-null">, </span><span class="cm-variable">self._b</span></pre><pre><span class="cm-null"> </span></pre><pre><span class="cm-variable">obj</span><span class="cm-null"> = </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-string">'avalue'</span><span class="cm-null">, </span><span class="cm-string">'bvalue'</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj.value</span><span class="cm-null">()</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj._a</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>('avalue', 'bvalue')
avalue</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 1px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><p>To "enforce" private methods / variables, we can use a <em>double</em> leading underscore:</p></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [17]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 170px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span> return self.__a, self.__b</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">class</span><span class="cm-null"> </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-builtin">object</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">__init__</span><span class="cm-null">(</span><span class="cm-variable">self</span><span class="cm-null">, </span><span class="cm-variable">a</span><span class="cm-null">, </span><span class="cm-variable">b</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">self.__a</span><span class="cm-null"> = </span><span class="cm-variable">a</span></pre><pre><span class="cm-null"> </span><span class="cm-variable">self.__b</span><span class="cm-null"> = </span><span class="cm-variable">b</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">def</span><span class="cm-null"> </span><span class="cm-variable">value</span><span class="cm-null">(</span><span class="cm-variable">self</span><span class="cm-null">):</span></pre><pre><span class="cm-null"> </span><span class="cm-keyword">return</span><span class="cm-null"> </span><span class="cm-variable">self.__a</span><span class="cm-null">, </span><span class="cm-variable">self.__b</span></pre><pre><span class="cm-null"> </span></pre><pre><span class="cm-variable">obj</span><span class="cm-null"> = </span><span class="cm-variable">MyClass</span><span class="cm-null">(</span><span class="cm-string">'avalue'</span><span class="cm-null">, </span><span class="cm-string">'bvalue'</span><span class="cm-null">)</span></pre><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj.value</span><span class="cm-null">()</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>('avalue', 'bvalue')</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [18]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print obj.__a</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj.__a</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text"><pre><span class="ansired">---------------------------------------------------------------------------</span>
<span class="ansired">AttributeError</span> Traceback (most recent call last)
<span class="ansigreen">/vagrant/<ipython-input-18-383b7dc3f3c4></span> in <span class="ansicyan"><module></span><span class="ansiblue">()</span>
<span class="ansigreen">----> 1</span><span class="ansired"> </span><span class="ansigreen">print</span> obj<span class="ansiblue">.</span>__a<span class="ansiblue"></span>
<span class="ansired">AttributeError</span>: 'MyClass' object has no attribute '__a'
</pre></div></div></div></div><div tabindex="2" class="cell border-box-sizing code_cell vbox"><div class="input hbox"><div class="prompt input_prompt">In [21]:</div><div class="input_area box-flex1"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px; top: 0px; left: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-ipython"><div style="position: relative; height: 30px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre><span>print obj._MyClass__a</span></pre></div><div style="position: relative; top: 0px;"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative;" draggable="true"><pre style="top: 0px; left: 0px;" class="CodeMirror-cursor"> </pre><div style=""><pre><span class="cm-keyword">print</span><span class="cm-null"> </span><span class="cm-variable">obj._MyClass__a</span></pre></div></div></div></div></div></div></div></div></div><div style="display: -moz-box;" class="output vbox"><div class="hbox output_area"><div class="prompt"></div><div class="box_flex1 output_subarea output_text output_stream output_stdout"><pre>avalue</pre></div></div></div></div><div tabindex="2" class="cell text_cell border-box-sizing"><div style="display: none;" class="text_cell_input"><div class="CodeMirror"><div style="overflow: hidden; position: relative; width: 1px; height: 0px;"><textarea style="position: absolute; width: 2px;" wrap="off" autocorrect="off" autocapitalize="off"></textarea></div><div class="CodeMirror-scroll cm-s-default"><div style="position: relative; height: 5px;"><div style="position: absolute; height: 0; width: 0; overflow: hidden;"><pre>x</pre></div><div style="position: relative"><div style="display: none;" class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div><div class="CodeMirror-lines"><div style="position: relative" draggable="true"><pre class="CodeMirror-cursor"> </pre><div></div></div></div></div></div></div></div></div><div tabindex="-1" class="text_cell_render rendered_html"><h3>Exercise</h3>
<p>Write a class to manage a telephone directory. The directory should be
stored in a dict as an instance variable. The class should have methods
<code>add_number(name, number)</code>, <code>remove_number(name)</code>, and <code>lookup_number(name)</code>.</p></div></div><div style="height: 30%;" class="end_space"></div></body></html>