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Slides for "Comprehensions in Python the Jedi way"
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</head>
<body>
<div class="progress">
<div class="progress-bar"></div>
</div>
<div class="slide" id="slide-1">
<section class="slide-content"><h1 id="comprehensions-in-python-the-jedi-way">Comprehensions in Python the Jedi way</h1>
<h2 id="https-gist-github-com-bearfrieze-a746c6f12d8bada03589"><a href="https://gist.github.com/bearfrieze/a746c6f12d8bada03589">https://gist.github.com/bearfrieze/a746c6f12d8bada03589</a></h2>
</section>
</div>
<div class="slide hidden" id="slide-2">
<section class="slide-content"><h3 id="collections">Collections</h3>
<ul>
<li>Droids</li>
<li>Jedis</li>
<li>Planets</li>
<li>Lightsabers</li>
</ul>
</section>
</div>
<div class="slide hidden" id="slide-3">
<section class="slide-content"><h3 id="data-structures">Data structures</h3>
<ul>
<li>Lists: <code>[a, b, c]</code></li>
<li>Sets: <code>{a, b, c}</code></li>
<li>Dictionaries: <code>{&#39;a&#39;: 1, &#39;b&#39;: 2, &#39;c&#39;: 3}</code></li>
</ul>
</section>
</div>
<div class="slide hidden" id="slide-4">
<section class="slide-content"><p><img src="https://imgur.com/oKCXrwA.gif" alt=""></p>
</section>
</div>
<div class="slide hidden" id="slide-5">
<section class="slide-content"><h3 id="bleeps-and-bloops">Bleeps and bloops</h3>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>bbs = <span class="hljs-string">'01110011001000000110111001101111001000000010000001101001001000000111001101101110001000000110010100100000001000000110100000100000001000000110010100100000011100100010000000100000011100000110110100100000011011110010000001100011'</span></code></pre>
</section>
</div>
<div class="slide hidden" id="slide-6">
<section class="slide-content"><h3 id="ascii">ASCII</h3>
<ul>
<li>01000001 ↔ 65 ↔ A</li>
<li>01000010 ↔ 66 ↔ B</li>
<li>01000011 ↔ 67 ↔ C</li>
</ul>
</section>
</div>
<div class="slide hidden" id="slide-7">
<section class="slide-content"><h3 id="list-slicing">List slicing</h3>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>l = [<span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>l[<span class="hljs-number">1</span>:]
[<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>l[:<span class="hljs-number">4</span>]
[<span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>l[<span class="hljs-number">1</span>:<span class="hljs-number">4</span>]
[<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>l[<span class="hljs-number">1</span>:<span class="hljs-number">-1</span>]
[<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-8">
<section class="slide-content"><h3 id="imperative-approach">Imperative approach</h3>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>octets = []
<span class="hljs-meta">&gt;&gt;&gt; </span><span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, len(bbs), <span class="hljs-number">8</span>):
<span class="hljs-meta">... </span> octets.append(bbs[i:i+<span class="hljs-number">8</span>])
<span class="hljs-meta">&gt;&gt;&gt; </span>octets
[<span class="hljs-string">'01110011'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101001'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110011'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110010'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110000'</span>, <span class="hljs-string">'01101101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100011'</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-9">
<section class="slide-content"><h3 id="functional-approach">Functional approach</h3>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>list(map(<span class="hljs-keyword">lambda</span> i: bbs[i:i+<span class="hljs-number">8</span>], range(<span class="hljs-number">0</span>, len(bbs), <span class="hljs-number">8</span>)))
[<span class="hljs-string">'01110011'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101001'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110011'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110010'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110000'</span>, <span class="hljs-string">'01101101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100011'</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-10">
<section class="slide-content"><h3 id="the-jedi-way-comprehensions-">The Jedi way (comprehensions)</h3>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>[bbs[i:i+<span class="hljs-number">8</span>] <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, len(bbs), <span class="hljs-number">8</span>)]
[<span class="hljs-string">'01110011'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101001'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110011'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110010'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110000'</span>, <span class="hljs-string">'01101101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100011'</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-11">
<section class="slide-content"><p><img src="https://i.imgur.com/l1L9s0K.gif" alt=""></p>
</section>
</div>
<div class="slide hidden" id="slide-12">
<section class="slide-content"><h3 id="comprehensions">Comprehensions</h3>
<p>Structure:</p>
<pre><code class="lang-python">[&lt;expression&gt; <span class="hljs-keyword">for</span> &lt;element&gt; <span class="hljs-keyword">in</span> &lt;iterable&gt;]</code></pre>
<p>Examples:</p>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>[n <span class="hljs-keyword">for</span> n <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, <span class="hljs-number">5</span>)]
[<span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>[n**<span class="hljs-number">2</span> <span class="hljs-keyword">for</span> n <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, <span class="hljs-number">5</span>)]
[<span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">4</span>, <span class="hljs-number">9</span>, <span class="hljs-number">16</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>[bbs[i:i+<span class="hljs-number">8</span>] <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, len(bbs), <span class="hljs-number">8</span>)]
[<span class="hljs-string">'01110011'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101001'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110011'</span>, <span class="hljs-string">'01101110'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110010'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01110000'</span>, <span class="hljs-string">'01101101'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01101111'</span>, <span class="hljs-string">'00100000'</span>, <span class="hljs-string">'01100011'</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-13">
<section class="slide-content"><h3 id="decode">Decode</h3>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>octets = [bbs[i:i+<span class="hljs-number">8</span>] <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, len(bbs), <span class="hljs-number">8</span>)]
<span class="hljs-meta">&gt;&gt;&gt; </span>chrs = [chr(int(octet, <span class="hljs-number">2</span>)) <span class="hljs-keyword">for</span> octet <span class="hljs-keyword">in</span> octets]
<span class="hljs-meta">&gt;&gt;&gt; </span>chrs
[<span class="hljs-string">'s'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'i'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'s'</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'h'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'r'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'p'</span>, <span class="hljs-string">'m'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">' '</span>, <span class="hljs-string">'c'</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-14">
<section class="slide-content"><h3 id="filter">Filter</h3>
<p>Functional:</p>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>list(filter(<span class="hljs-keyword">lambda</span> c: c != <span class="hljs-string">' '</span>, chrs))
[<span class="hljs-string">'s'</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">'i'</span>, <span class="hljs-string">'s'</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">'h'</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">'r'</span>, <span class="hljs-string">'p'</span>, <span class="hljs-string">'m'</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">'c'</span>]</code></pre>
<p>Comprehensions:</p>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>[c <span class="hljs-keyword">for</span> c <span class="hljs-keyword">in</span> chrs <span class="hljs-keyword">if</span> c != <span class="hljs-string">' '</span>]
[<span class="hljs-string">'s'</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">'i'</span>, <span class="hljs-string">'s'</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">'h'</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">'r'</span>, <span class="hljs-string">'p'</span>, <span class="hljs-string">'m'</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">'c'</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-15">
<section class="slide-content"><h3 id="comprehensions">Comprehensions</h3>
<p>Structure:</p>
<pre><code class="lang-python">[&lt;expression&gt; <span class="hljs-keyword">for</span> &lt;element&gt; <span class="hljs-keyword">in</span> &lt;iterable&gt; <span class="hljs-keyword">if</span> &lt;expression&gt;]</code></pre>
<p>Examples:</p>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>[n <span class="hljs-keyword">for</span> n <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, <span class="hljs-number">5</span>) <span class="hljs-keyword">if</span> n % <span class="hljs-number">2</span> == <span class="hljs-number">0</span>]
[<span class="hljs-number">0</span>, <span class="hljs-number">2</span>, <span class="hljs-number">4</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>[n**<span class="hljs-number">2</span> <span class="hljs-keyword">for</span> n <span class="hljs-keyword">in</span> range(<span class="hljs-number">0</span>, <span class="hljs-number">5</span>) <span class="hljs-keyword">if</span> n % <span class="hljs-number">2</span> == <span class="hljs-number">0</span>]
[<span class="hljs-number">0</span>, <span class="hljs-number">4</span>, <span class="hljs-number">16</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span>[c <span class="hljs-keyword">for</span> c <span class="hljs-keyword">in</span> chrs <span class="hljs-keyword">if</span> c != <span class="hljs-string">' '</span>]
[<span class="hljs-string">'s'</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">'i'</span>, <span class="hljs-string">'s'</span>, <span class="hljs-string">'n'</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">'h'</span>, <span class="hljs-string">'e'</span>, <span class="hljs-string">'r'</span>, <span class="hljs-string">'p'</span>, <span class="hljs-string">'m'</span>, <span class="hljs-string">'o'</span>, <span class="hljs-string">'c'</span>]</code></pre>
</section>
</div>
<div class="slide hidden" id="slide-16">
<section class="slide-content"><h3 id="join-and-reverse">Join and reverse</h3>
<pre><code class="lang-python"><span class="hljs-meta">&gt;&gt;&gt; </span>chrs = [c <span class="hljs-keyword">for</span> c <span class="hljs-keyword">in</span> chrs <span class="hljs-keyword">if</span> c != <span class="hljs-string">' '</span>]
<span class="hljs-meta">&gt;&gt;&gt; </span><span class="hljs-string">''</span>.join(chrs)
<span class="hljs-string">'snoisneherpmoc'</span>
<span class="hljs-meta">&gt;&gt;&gt; </span><span class="hljs-string">''</span>.join(reversed(chrs))
<span class="hljs-string">'comprehensions'</span></code></pre>
</section>
</div>
<div class="slide hidden" id="slide-17">
<section class="slide-content"><p><img src="https://i.imgur.com/NLg1gzC.gif" alt=""></p>
<p>Link to article available on Slack and Facebook.</p>
</section>
</div>
<div class="slide hidden author-slide" id="slide-18">
<section class="slide-content"><div class="author">
<h1 class="name">Bjørn Friese</h1>
<h3 class="url">
<a href="https://frieze.dk">https://frieze.dk</a>
</h3>
<h3 class="email">
<a href="mailto:[email protected]">[email protected]</a>
</h3>
</div>
</section>
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slides.md

title: Comprehensions in Python the Jedi way author: name: Bjørn Friese email: [email protected] url: https://frieze.dk output: slides.html style: slides.css controls: false

--

Comprehensions in Python the Jedi way

https://gist.github.com/bearfrieze/a746c6f12d8bada03589

--

Collections

  • Droids
  • Jedis
  • Planets
  • Lightsabers

--

Data structures

  • Lists: [a, b, c]
  • Sets: {a, b, c}
  • Dictionaries: {'a': 1, 'b': 2, 'c': 3}

--

--

Bleeps and bloops

>>> bbs = '01110011001000000110111001101111001000000010000001101001001000000111001101101110001000000110010100100000001000000110100000100000001000000110010100100000011100100010000000100000011100000110110100100000011011110010000001100011'

--

ASCII

  • 01000001 ↔ 65 ↔ A
  • 01000010 ↔ 66 ↔ B
  • 01000011 ↔ 67 ↔ C

--

List slicing

>>> l = [0, 1, 2, 3, 4]

>>> l[1:]
[1, 2, 3, 4]

>>> l[:4]
[0, 1, 2, 3]

>>> l[1:4]
[1, 2, 3]

>>> l[1:-1]
[1, 2, 3]

--

Imperative approach

>>> octets = []
>>> for i in range(0, len(bbs), 8):
...   octets.append(bbs[i:i+8])

>>> octets
['01110011', '00100000', '01101110', '01101111', '00100000', '00100000', '01101001', '00100000', '01110011', '01101110', '00100000', '01100101', '00100000', '00100000', '01101000', '00100000', '00100000', '01100101', '00100000', '01110010', '00100000', '00100000', '01110000', '01101101', '00100000', '01101111', '00100000', '01100011']

--

Functional approach

>>> list(map(lambda i: bbs[i:i+8], range(0, len(bbs), 8)))
['01110011', '00100000', '01101110', '01101111', '00100000', '00100000', '01101001', '00100000', '01110011', '01101110', '00100000', '01100101', '00100000', '00100000', '01101000', '00100000', '00100000', '01100101', '00100000', '01110010', '00100000', '00100000', '01110000', '01101101', '00100000', '01101111', '00100000', '01100011']

--

The Jedi way (comprehensions)

>>> [bbs[i:i+8] for i in range(0, len(bbs), 8)]
['01110011', '00100000', '01101110', '01101111', '00100000', '00100000', '01101001', '00100000', '01110011', '01101110', '00100000', '01100101', '00100000', '00100000', '01101000', '00100000', '00100000', '01100101', '00100000', '01110010', '00100000', '00100000', '01110000', '01101101', '00100000', '01101111', '00100000', '01100011']

--

--

Comprehensions

Structure:

[<expression> for <element> in <iterable>]

Examples:

>>> [n for n in range(0, 5)]
[0, 1, 2, 3, 4]

>>> [n**2 for n in range(0, 5)]
[0, 1, 4, 9, 16]

>>> [bbs[i:i+8] for i in range(0, len(bbs), 8)]
['01110011', '00100000', '01101110', '01101111', '00100000', '00100000', '01101001', '00100000', '01110011', '01101110', '00100000', '01100101', '00100000', '00100000', '01101000', '00100000', '00100000', '01100101', '00100000', '01110010', '00100000', '00100000', '01110000', '01101101', '00100000', '01101111', '00100000', '01100011']

--

Decode

>>> octets = [bbs[i:i+8] for i in range(0, len(bbs), 8)]
>>> chrs = [chr(int(octet, 2)) for octet in octets]
>>> chrs
['s', ' ', 'n', 'o', ' ', ' ', 'i', ' ', 's', 'n', ' ', 'e', ' ', ' ', 'h', ' ', ' ', 'e', ' ', 'r', ' ', ' ', 'p', 'm', ' ', 'o', ' ', 'c']

--

Filter

Functional:

>>> list(filter(lambda c: c != ' ', chrs))
['s', 'n', 'o', 'i', 's', 'n', 'e', 'h', 'e', 'r', 'p', 'm', 'o', 'c']

Comprehensions:

>>> [c for c in chrs if c != ' ']
['s', 'n', 'o', 'i', 's', 'n', 'e', 'h', 'e', 'r', 'p', 'm', 'o', 'c']

--

Comprehensions

Structure:

[<expression> for <element> in <iterable> if <expression>]

Examples:

>>> [n for n in range(0, 5) if n % 2 == 0]
[0, 2, 4]

>>> [n**2 for n in range(0, 5) if n % 2 == 0]
[0, 4, 16]

>>> [c for c in chrs if c != ' ']
['s', 'n', 'o', 'i', 's', 'n', 'e', 'h', 'e', 'r', 'p', 'm', 'o', 'c']

--

Join and reverse

>>> chrs = [c for c in chrs if c != ' ']

>>> ''.join(chrs)
'snoisneherpmoc'

>>> ''.join(reversed(chrs))
'comprehensions'

--

Link to article available on Slack and Facebook.

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