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<div class="section" id="base-types">
<h1>Base types<a class="headerlink" href="#base-types" title="Permalink to this headline"></a></h1>
<ul class="simple">
<li><a class="reference external" href="https://realpython.com/python-data-types/">types</a></li>
</ul>
<div class="section" id="python-is-dynamically-typed">
<h2>Python is dynamically typed<a class="headerlink" href="#python-is-dynamically-typed" title="Permalink to this headline"></a></h2>
<p>it means</p>
<ul class="simple">
<li>variables don’t have fixed type, the types can change</li>
<li>the variable’s type is specified at runtime during the assignment</li>
</ul>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">a</span> <span class="o">=</span> <span class="mi">1</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go">&lt;class &#39;int&#39;&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">a</span> <span class="o">=</span> <span class="mf">2.</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">a</span>
<span class="go">2.0</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go">&lt;class &#39;float&#39;&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">b</span> <span class="o">=</span> <span class="s2">&quot;b&quot;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">type</span><span class="p">(</span><span class="n">b</span><span class="p">)</span>
<span class="go">&lt;class &#39;str&#39;&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">c</span> <span class="o">=</span> <span class="s2">&quot;3&quot;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">type</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>
<span class="go">&lt;class &#39;str&#39;&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">int</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>
<span class="go">3</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">c2</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">c2</span>
<span class="go">3</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">type</span><span class="p">(</span><span class="n">c2</span><span class="p">)</span>
<span class="go">&lt;class &#39;int&#39;&gt;</span>
<span class="go">&gt;&gt;&gt;</span>
</pre></div>
</div>
</div>
<div class="section" id="some-builtin-types">
<h2>Some builtin types<a class="headerlink" href="#some-builtin-types" title="Permalink to this headline"></a></h2>
<p>base types:</p>
<ul class="simple">
<li>integer,</li>
<li>float,</li>
<li>string,</li>
<li>boolean</li>
</ul>
<p>base container types:</p>
<ul class="simple">
<li>list,</li>
<li>dictionnary,</li>
<li>set</li>
</ul>
<p>list type sample:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">l</span> <span class="o">=</span> <span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">l</span>
<span class="go">range(0, 10)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="n">l</span><span class="p">:</span>
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>
<span class="gp">...</span>
<span class="go">0</span>
<span class="go">(...)</span>
<span class="go">9</span>
</pre></div>
</div>
<p>dictionary type sample:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">d</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">(</span><span class="n">a</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">b</span><span class="o">=</span><span class="mi">5</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">d</span>
<span class="go">{&#39;b&#39;: 5, &#39;a&#39;: 2}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">type</span><span class="p">(</span><span class="n">d</span><span class="p">)</span>
<span class="go">&lt;class &#39;dict&#39;&gt;</span>
</pre></div>
</div>
<p>a dict <strong>is not</strong> a ordered type. If you need an ordered dict, use a more
advanced collection type like an ordered dict</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">collections</span> <span class="k">import</span> <span class="n">OrderedDict</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">d</span> <span class="o">=</span> <span class="n">OrderedDict</span><span class="p">({</span><span class="s1">&#39;banana&#39;</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="s1">&#39;apple&#39;</span><span class="p">:</span> <span class="mi">4</span><span class="p">,</span> <span class="s1">&#39;pear&#39;</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">&#39;orange&#39;</span><span class="p">:</span> <span class="mi">2</span><span class="p">})</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">d</span>
<span class="go">OrderedDict([(&#39;orange&#39;, 2), (&#39;apple&#39;, 4), (&#39;banana&#39;, 3), (&#39;pear&#39;, 1)])</span>
<span class="go">&gt;&gt;&gt;</span>
</pre></div>
</div>
<p>set sample:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="nb">set</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">))</span>
<span class="go">{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}</span>
</pre></div>
</div>
<p>a set <strong>is not</strong> ordered</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="nb">set</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">))</span>
<span class="gp">&gt;&gt;&gt; </span><span class="mi">3</span> <span class="ow">in</span> <span class="n">s</span>
<span class="go">True</span>
</pre></div>
</div>
</div>
<div class="section" id="mutable-types-and-non-mutable-types">
<h2>Mutable types and non-mutable types<a class="headerlink" href="#mutable-types-and-non-mutable-types" title="Permalink to this headline"></a></h2>
<p>A set is immutable, whereas a list is mutable:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="nb">set</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">])</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">l</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">]</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">l</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">list</span><span class="p">(</span><span class="n">l</span><span class="p">)</span>
<span class="go">[1, 2, 3]</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">s</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
File <span class="nb">&quot;&lt;stdin&gt;&quot;</span>, line <span class="m">1</span>, in <span class="n">&lt;module&gt;</span>
<span class="gr">AttributeError</span>: <span class="n">&#39;set&#39; object has no attribute &#39;append&#39;</span>
<span class="go">&gt;&gt;&gt;</span>
</pre></div>
</div>
<p>A string is immutable. If you want to modify it, build another string:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="s2">&quot;hello&quot;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">s</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s1">&#39;ll&#39;</span><span class="p">,</span> <span class="s1">&#39;bb&#39;</span><span class="p">)</span>
<span class="go">&#39;hebbo&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">s</span><span class="o">+</span><span class="s2">&quot;you&quot;</span>
<span class="go">&#39;helloyou&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">s</span>
<span class="go">&#39;hello&#39;</span>
</pre></div>
</div>
<p>you can see that s hasn’t changed.</p>
</div>
<div class="section" id="even-base-types-are-objects">
<h2>Even base types are objects<a class="headerlink" href="#even-base-types-are-objects" title="Permalink to this headline"></a></h2>
<p>It means that in python, classes are types (let’s understand it like that at first glance)</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">a</span> <span class="o">=</span> <span class="mi">2</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">isinstance</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="nb">int</span><span class="p">)</span>
<span class="go">True</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="s2">&quot;a&quot;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">dir</span><span class="p">(</span><span class="n">s</span><span class="p">)</span>
<span class="go">[&#39;__add__&#39;, &#39;__class__&#39;, &#39;__contains__&#39;, &#39;__delattr__&#39;, &#39;__dir__&#39;, &#39;__doc__&#39;,</span>
<span class="go">&#39;__eq__&#39;, &#39;__format__&#39;, &#39;__ge__&#39;, &#39;__getattribute__&#39;, &#39;__getitem__&#39;,</span>
<span class="go">(...)</span>
<span class="go">&#39;__init__&#39;, &#39;__iter__&#39;, &#39;__le__&#39;, &#39;__len__&#39;, &#39;__lt__&#39;, ]</span>
</pre></div>
</div>
<p><cite>s</cite> has methods. It’s an objects. The type of s is the class <cite>int</cite>.</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">d</span> <span class="o">=</span> <span class="p">{</span><span class="s1">&#39;banana&#39;</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="s1">&#39;apple&#39;</span><span class="p">:</span> <span class="mi">4</span><span class="p">,</span> <span class="s1">&#39;pear&#39;</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">&#39;orange&#39;</span><span class="p">:</span> <span class="mi">2</span><span class="p">}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">isinstance</span><span class="p">(</span><span class="n">d</span><span class="p">,</span> <span class="nb">dict</span><span class="p">)</span>
<span class="go">True</span>
<span class="go">&gt;&gt;&gt;</span>
</pre></div>
</div>
<p>special methods: the iterator sample</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">l</span> <span class="o">=</span> <span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="n">l</span><span class="p">:</span>
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>
</pre></div>
</div>
<p>We can use the <cite>for</cite> statement only because the <cite>list</cite> type has a special <cite>__iter__</cite>
method:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">l</span><span class="o">.</span><span class="fm">__iter__</span><span class="p">()</span>
<span class="go">&lt;range_iterator object at 0x7f28b76e1e10&gt;</span>
<span class="go">&gt;&gt;&gt;</span>
</pre></div>
</div>
<p>we will see the special methods later.</p>
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