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  String Methods
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<h1 id="String-Methods">String Methods<a class="anchor-link" href="#String-Methods"> </a></h1><p>From an existing string, related strings can be constructed using string methods, which are functions that operate on strings. These methods are called by placing a dot after the string, then calling the function.</p>
<p>For example, the following method generates an uppercased version of a string.</p>

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<div class=" highlight hl-ipython3"><pre><span></span><span class="s2">&quot;loud&quot;</span><span class="o">.</span><span class="n">upper</span><span class="p">()</span>
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<pre>&#39;LOUD&#39;</pre>
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<p>Perhaps the most important method is <code>replace</code>, which replaces all instances of a substring within the string. The <code>replace</code> method takes two arguments, the text to be replaced and its replacement.</p>

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<div class=" highlight hl-ipython3"><pre><span></span><span class="s1">&#39;hitchhiker&#39;</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s1">&#39;hi&#39;</span><span class="p">,</span> <span class="s1">&#39;ma&#39;</span><span class="p">)</span>
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<pre>&#39;matchmaker&#39;</pre>
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<p>String methods can also be invoked using variable names, as long as those names are bound to strings. So, for instance, the following two-step process generates the word "degrade" starting from "train" by first creating "ingrain" and then applying a second replacement.</p>

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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">s</span> <span class="o">=</span> <span class="s2">&quot;train&quot;</span>
<span class="n">t</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s1">&#39;t&#39;</span><span class="p">,</span> <span class="s1">&#39;ing&#39;</span><span class="p">)</span>
<span class="n">u</span> <span class="o">=</span> <span class="n">t</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s1">&#39;in&#39;</span><span class="p">,</span> <span class="s1">&#39;de&#39;</span><span class="p">)</span>
<span class="n">u</span>
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<pre>&#39;degrade&#39;</pre>
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<p>Note that the line <code>t = s.replace('t', 'ing')</code> doesn't change the string <code>s</code>, which is still "train".  The method call <code>s.replace('t', 'ing')</code> just has a value, which is the string "ingrain".</p>

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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">s</span>
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<pre>&#39;train&#39;</pre>
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<p>This is the first time we've seen methods, but methods are not unique to strings.  As we will see shortly, other types of objects can have them.</p>

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