<meta charset="utf-8" /><meta http-equiv="content-security-policy" content=""><meta name="hf:doc:metadata" content="{&quot;local&quot;:&quot;toknisation-iwordpiecei&quot;,&quot;sections&quot;:[{&quot;local&quot;:&quot;algorithme-dentranement&quot;,&quot;title&quot;:&quot;Algorithme d&#39;entraînement&quot;},{&quot;local&quot;:&quot;algorithme-de-tokenisation&quot;,&quot;title&quot;:&quot;Algorithme de tokenisation&quot;},{&quot;local&quot;:&quot;implmentation-de-iwordpiecei&quot;,&quot;title&quot;:&quot;Implémentation de &lt;i&gt;WordPiece&lt;/i&gt;&quot;}],&quot;title&quot;:&quot;Tokénisation &lt;i&gt;WordPiece&lt;/i&gt;&quot;}" data-svelte="svelte-1phssyn">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/assets/pages/__layout.svelte-hf-doc-builder.css">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/start-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/chunks/vendor-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/chunks/paths-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/pages/__layout.svelte-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/pages/chapter6/6.mdx-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/chunks/Tip-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/chunks/Youtube-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/chunks/IconCopyLink-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/chunks/CodeBlock-hf-doc-builder.js">
	<link rel="modulepreload" href="/docs/course/pr_212/fr/_app/chunks/DocNotebookDropdown-hf-doc-builder.js"> 





<h1 class="relative group"><a id="toknisation-iwordpiecei" class="header-link block pr-1.5 text-lg no-hover:hidden with-hover:absolute with-hover:p-1.5 with-hover:opacity-0 with-hover:group-hover:opacity-100 with-hover:right-full" href="#toknisation-iwordpiecei"><span><svg class="" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 256 256"><path d="M167.594 88.393a8.001 8.001 0 0 1 0 11.314l-67.882 67.882a8 8 0 1 1-11.314-11.315l67.882-67.881a8.003 8.003 0 0 1 11.314 0zm-28.287 84.86l-28.284 28.284a40 40 0 0 1-56.567-56.567l28.284-28.284a8 8 0 0 0-11.315-11.315l-28.284 28.284a56 56 0 0 0 79.196 79.197l28.285-28.285a8 8 0 1 0-11.315-11.314zM212.852 43.14a56.002 56.002 0 0 0-79.196 0l-28.284 28.284a8 8 0 1 0 11.314 11.314l28.284-28.284a40 40 0 0 1 56.568 56.567l-28.285 28.285a8 8 0 0 0 11.315 11.314l28.284-28.284a56.065 56.065 0 0 0 0-79.196z" fill="currentColor"></path></svg></span></a>
	<span>Tokénisation <i>WordPiece</i></span></h1>



<div class="flex space-x-1 absolute z-10 right-0 top-0"><a href="https://colab.research.google.com/github/huggingface/notebooks/blob/master/course/chapter6/section6.ipynb" target="_blank"><img alt="Open In Colab" class="!m-0" src="https://colab.research.google.com/assets/colab-badge.svg"></a>
	<a href="https://studiolab.sagemaker.aws/import/github/huggingface/notebooks/blob/master/course/chapter6/section6.ipynb" target="_blank"><img alt="Open In Studio Lab" class="!m-0" src="https://studiolab.sagemaker.aws/studiolab.svg"></a></div>
<p><em>WordPiece</em> est l’algorithme de tokénisation développé par Google pour prétraîner BERT. Il a depuis été réutilisé dans un grand nombre de modèles de <em>transformers</em> basés sur BERT tels que DistilBERT, MobileBERT, Funnel Transformers et MPNET. Il est très similaire au BPE en termes d’entraînement mais la tokenisation réelle est effectuée différemment.</p>
<iframe class="w-full xl:w-4/6 h-80" src="https://www.youtube-nocookie.com/embed/qpv6ms_t_1A" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>


<div class="course-tip  bg-gradient-to-br dark:bg-gradient-to-r before:border-green-500 dark:before:border-green-800 from-green-50 dark:from-gray-900 to-white dark:to-gray-950 border border-green-50 text-green-700 dark:text-gray-400"><p>💡 Cette section couvre le <i>WordPiece</i> en profondeur, allant jusqu’à montrer une implémentation complète. Vous pouvez passer directement à la fin si vous souhaitez simplement avoir un aperçu général de l’algorithme de tokénisation.</p></div>
<h2 class="relative group"><a id="algorithme-dentranement" class="header-link block pr-1.5 text-lg no-hover:hidden with-hover:absolute with-hover:p-1.5 with-hover:opacity-0 with-hover:group-hover:opacity-100 with-hover:right-full" href="#algorithme-dentranement"><span><svg class="" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 256 256"><path d="M167.594 88.393a8.001 8.001 0 0 1 0 11.314l-67.882 67.882a8 8 0 1 1-11.314-11.315l67.882-67.881a8.003 8.003 0 0 1 11.314 0zm-28.287 84.86l-28.284 28.284a40 40 0 0 1-56.567-56.567l28.284-28.284a8 8 0 0 0-11.315-11.315l-28.284 28.284a56 56 0 0 0 79.196 79.197l28.285-28.285a8 8 0 1 0-11.315-11.314zM212.852 43.14a56.002 56.002 0 0 0-79.196 0l-28.284 28.284a8 8 0 1 0 11.314 11.314l28.284-28.284a40 40 0 0 1 56.568 56.567l-28.285 28.285a8 8 0 0 0 11.315 11.314l28.284-28.284a56.065 56.065 0 0 0 0-79.196z" fill="currentColor"></path></svg></span></a>
	<span>Algorithme d&#39;entraînement
	</span></h2>



<div class="course-tip course-tip-orange bg-gradient-to-br dark:bg-gradient-to-r before:border-orange-500 dark:before:border-orange-800 from-orange-50 dark:from-gray-900 to-white dark:to-gray-950 border border-orange-50 text-orange-700 dark:text-gray-400"><p>⚠️ Google n’a jamais mis en ligne son implémentation de l’algorithme d’entraînement du <i>WordPiece</i>. Ce qui suit est donc notre meilleure estimation basée sur la littérature publiée. Il se peut qu’elle ne soit pas exacte à 100 %.</p></div>
<p>Comme le BPE, <em>WordPiece</em> part d’un petit vocabulaire comprenant les <em>tokens</em> spéciaux utilisés par le modèle et l’alphabet initial. Puisqu’il identifie les sous-mots en ajoutant un préfixe (comme <code>##</code> pour BERT), chaque mot est initialement découpé en ajoutant ce préfixe à tous les caractères du mot. Ainsi par exemple, <code>&quot;word&quot;</code> est divisé comme ceci :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->w ##o ##r ##d<!-- HTML_TAG_END --></pre></div>
<p>Ainsi, l’alphabet initial contient tous les caractères présents au début d’un mot et les caractères présents à l’intérieur d’un mot précédé du préfixe de <em>WordPiece</em>.</p>
<p>Ensuite, toujours comme le BPE, <em>WordPiece</em> apprend des règles de fusion. La principale différence réside dans la manière dont la paire à fusionner est sélectionnée. Au lieu de sélectionner la paire la plus fréquente, <em>WordPiece</em> calcule un score pour chaque paire en utilisant la formule suivante :
<!-- HTML_TAG_START --><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mrow><mi mathvariant="normal">s</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi></mrow><mo>=</mo><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">f</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">q</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">f</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">p</mi><mi mathvariant="normal">a</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">r</mi></mrow><mo stretchy="false">)</mo><mi mathvariant="normal">/</mi><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">f</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">q</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">f</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">f</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">m</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">t</mi></mrow><mo>×</mo><mrow><mi mathvariant="normal">f</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">q</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">f</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">d</mi><mi mathvariant="normal">_</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">m</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">t</mi></mrow><mo stretchy="false">)</mo></mrow><annotation encoding="application/x-tex">\mathrm{score} = (\mathrm{freq\_of\_pair}) / (\mathrm{freq\_of\_first\_element} \times \mathrm{freq\_of\_second\_element})</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.4306em;"></span><span class="mord"><span class="mord mathrm">score</span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1.06em;vertical-align:-0.31em;"></span><span class="mopen">(</span><span class="mord"><span class="mord mathrm">freq_of_pair</span></span><span class="mclose">)</span><span class="mord">/</span><span class="mopen">(</span><span class="mord"><span class="mord mathrm">freq_of_first_element</span></span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">×</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1.06em;vertical-align:-0.31em;"></span><span class="mord"><span class="mord mathrm">freq_of_second_element</span></span><span class="mclose">)</span></span></span></span></span><!-- HTML_TAG_END --></p>
<p>En divisant la fréquence de la paire par le produit des fréquences de chacune de ses parties, l’algorithme donne la priorité à la fusion des paires dont les parties individuelles sont moins fréquentes dans le vocabulaire. Par exemple, il ne fusionnera pas nécessairement <code>(&quot;un&quot;, &quot;##able&quot;)</code> même si cette paire apparaît très fréquemment dans le vocabulaire car les deux paires <code>&quot;un&quot;</code>” et <code>&quot;##able&quot;</code> apparaîtront probablement chacune dans un batch d’autres mots et auront une fréquence élevée. En revanche, une paire comme <code>(&quot;hu&quot;, &quot;##gging&quot;)</code> sera probablement fusionnée plus rapidement (en supposant que le mot <code>&quot;hugging&quot;</code> apparaisse souvent dans le vocabulaire) puisque <code>&quot;hu&quot;</code> et <code>&quot;##gging&quot;</code> sont probablement moins fréquents individuellement.</p>
<p>Examinons le même vocabulaire que celui utilisé dans l’exemple d’entraînement du BPE :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->(<span class="hljs-string">&quot;hug&quot;</span><span class="hljs-punctuation">,</span> <span class="hljs-number">10</span>)<span class="hljs-punctuation">,</span> (<span class="hljs-string">&quot;pug&quot;</span><span class="hljs-punctuation">,</span> <span class="hljs-number">5</span>)<span class="hljs-punctuation">,</span> (<span class="hljs-string">&quot;pun&quot;</span><span class="hljs-punctuation">,</span> <span class="hljs-number">12</span>)<span class="hljs-punctuation">,</span> (<span class="hljs-string">&quot;bun&quot;</span><span class="hljs-punctuation">,</span> <span class="hljs-number">4</span>)<span class="hljs-punctuation">,</span> (<span class="hljs-string">&quot;hugs&quot;</span><span class="hljs-punctuation">,</span> <span class="hljs-number">5</span>)<!-- HTML_TAG_END --></pre></div>
<p>Les divisions ici seront :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->(<span class="hljs-string">&quot;h&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-number">10</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-number">5</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">12</span>), (<span class="hljs-string">&quot;b&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">4</span>), (<span class="hljs-string">&quot;h&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#s</span>&quot;</span>, <span class="hljs-number">5</span>)<!-- HTML_TAG_END --></pre></div>
<p>Si on oublie les <em>tokens</em> spéciaux pour l’instant, le vocabulaire initial sera donc <code>[&quot;b&quot;, &quot;h&quot;, &quot;p&quot;, &quot;##g&quot;, &quot;##n&quot;, &quot;##s&quot;, &quot;##u&quot;]</code>. La paire la plus fréquente est <code>(&quot;##u&quot;, &quot;##g&quot;)</code> (présente 20 fois), mais la fréquence individuelle de <code>&quot;##u&quot;</code> est très élevée, donc son score n’est pas le plus élevé (il est de 1 / 36). Toutes les paires avec un <code>&quot;##u&quot;</code> ont en fait le même score (1 / 36). Ainsi le meilleur score va à la paire <code>(&quot;##g&quot;, &quot;##s&quot;)</code> qui est la seule sans un <code>&quot;##u&quot;</code> avec un score 1 / 20. Et la première fusion apprise est <code>(&quot;##g&quot;, &quot;##s&quot;) -&gt; (&quot;##gs&quot;)</code>.</p>
<p>Notez que lorsque nous fusionnons, nous enlevons le <code>##</code> entre les deux <em>tokens</em>, donc nous ajoutons <code>&quot;##gs&quot;</code> au vocabulaire et appliquons la fusion dans les mots du corpus :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->Vocabulary: [<span class="hljs-string">&quot;b&quot;</span>, <span class="hljs-string">&quot;h&quot;</span>, <span class="hljs-string">&quot;p&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#s</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#gs</span>&quot;</span>]
Corpus: (<span class="hljs-string">&quot;h&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-number">10</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-number">5</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">12</span>), (<span class="hljs-string">&quot;b&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">4</span>), (<span class="hljs-string">&quot;h&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#gs</span>&quot;</span>, <span class="hljs-number">5</span>)<!-- HTML_TAG_END --></pre></div>
<p>À ce stade, <code>&quot; ##u &quot;</code> est dans toutes les paires possibles, donc elles finissent toutes par avoir le même score. Disons que dans ce cas, la première paire est fusionnée, donc <code>(&quot;h&quot;, &quot;##u&quot;) -&gt; &quot;hu&quot;</code>. Cela nous amène à :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->Vocabulary: [<span class="hljs-string">&quot;b&quot;</span>, <span class="hljs-string">&quot;h&quot;</span>, <span class="hljs-string">&quot;p&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#s</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#gs</span>&quot;</span>, <span class="hljs-string">&quot;hu&quot;</span>]
Corpus: (<span class="hljs-string">&quot;hu&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-number">10</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-number">5</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">12</span>), (<span class="hljs-string">&quot;b&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">4</span>), (<span class="hljs-string">&quot;hu&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#gs</span>&quot;</span>, <span class="hljs-number">5</span>)<!-- HTML_TAG_END --></pre></div>
<p>Ensuite, le meilleur score suivant est partagé par <code>(&quot;hu&quot;, &quot;##g&quot;)</code> et <code>(&quot;hu&quot;, &quot;##gs&quot;)</code> (avec 1/15, comparé à 1/21 pour toutes les autres paires). Ainsi la première paire avec le plus grand score est fusionnée :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->Vocabulary: [<span class="hljs-string">&quot;b&quot;</span>, <span class="hljs-string">&quot;h&quot;</span>, <span class="hljs-string">&quot;p&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#s</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span>, <span class="hljs-string">&quot;#<span class="hljs-subst">#gs</span>&quot;</span>, <span class="hljs-string">&quot;hu&quot;</span>, <span class="hljs-string">&quot;hug&quot;</span>]
Corpus: (<span class="hljs-string">&quot;hug&quot;</span>, <span class="hljs-number">10</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#g</span>&quot;</span>, <span class="hljs-number">5</span>), (<span class="hljs-string">&quot;p&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">12</span>), (<span class="hljs-string">&quot;b&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#u</span>&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#n</span>&quot;</span>, <span class="hljs-number">4</span>), (<span class="hljs-string">&quot;hu&quot;</span> <span class="hljs-string">&quot;#<span class="hljs-subst">#gs</span>&quot;</span>, <span class="hljs-number">5</span>)<!-- HTML_TAG_END --></pre></div>
<p>et nous continuons ainsi jusqu’à ce que nous atteignions la taille de vocabulaire souhaitée.</p>


<div class="course-tip  bg-gradient-to-br dark:bg-gradient-to-r before:border-green-500 dark:before:border-green-800 from-green-50 dark:from-gray-900 to-white dark:to-gray-950 border border-green-50 text-green-700 dark:text-gray-400"><p>✏️ <strong>A votre tour !</strong> Quelle sera la prochaine règle de fusion ?</p></div>
<h2 class="relative group"><a id="algorithme-de-tokenisation" class="header-link block pr-1.5 text-lg no-hover:hidden with-hover:absolute with-hover:p-1.5 with-hover:opacity-0 with-hover:group-hover:opacity-100 with-hover:right-full" href="#algorithme-de-tokenisation"><span><svg class="" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 256 256"><path d="M167.594 88.393a8.001 8.001 0 0 1 0 11.314l-67.882 67.882a8 8 0 1 1-11.314-11.315l67.882-67.881a8.003 8.003 0 0 1 11.314 0zm-28.287 84.86l-28.284 28.284a40 40 0 0 1-56.567-56.567l28.284-28.284a8 8 0 0 0-11.315-11.315l-28.284 28.284a56 56 0 0 0 79.196 79.197l28.285-28.285a8 8 0 1 0-11.315-11.314zM212.852 43.14a56.002 56.002 0 0 0-79.196 0l-28.284 28.284a8 8 0 1 0 11.314 11.314l28.284-28.284a40 40 0 0 1 56.568 56.567l-28.285 28.285a8 8 0 0 0 11.315 11.314l28.284-28.284a56.065 56.065 0 0 0 0-79.196z" fill="currentColor"></path></svg></span></a>
	<span>Algorithme de tokenisation
	</span></h2>

<p>La tokénisation diffère dans <em>WordPiece</em> et BPE en ce que <em>WordPiece</em> ne sauvegarde que le vocabulaire final et non pas les règles de fusion apprises. En partant du mot à tokeniser, <em>WordPiece</em> trouve le sous-mot le plus long qui se trouve dans le vocabulaire, puis se sépare sur celui-ci. Par exemple, si nous utilisons le vocabulaire appris dans l’exemple ci-dessus, pour le mot <code>&quot;hugs&quot;</code> le plus long sous-mot en partant du début qui est dans le vocabulaire est <code>&quot;hug&quot;</code>. Donc nous le divisons et obtenons <code>[&quot;hug&quot;, &quot;##s&quot;]</code>. On continue avec <code>&quot;##s&quot;</code>, qui est dans le vocabulaire, donc la tokenisation de <code>&quot;hugs&quot;</code> est <code>[&quot;hug&quot;, &quot;##s&quot;]</code>.</p>
<p>Avec BPE, nous aurions appliqué les fusions apprises dans l’ordre et la tokénisation aurait été <code>[&quot;hu&quot;, &quot;##gs&quot;]</code>, l’encodage est donc différent.</p>
<p>Comme autre exemple, voyons comment le mot <code>&quot;bugs&quot;</code> serait tokenisé. <code>&quot;b&quot;</code> est le plus long sous-mot commençant au début du mot qui est dans le vocabulaire donc on le divise et on obtient <code>[&quot;b&quot;, &quot;##ugs&quot;]</code>. Ensuite, <code>&quot;##u&quot;</code> est le plus long sous-mot commençant au début de <code>&quot;##ugs&quot;</code> qui est dans le vocabulaire, donc on le sépare et on obtient <code>[&quot;b&quot;, &quot;##u, &quot;##gs&quot;]</code>. Enfin, <code>&quot;##gs&quot;</code> est dans le vocabulaire, donc cette dernière liste est la tokenization de <code>&quot;bugs&quot;</code>.</p>
<p>Lorsque la tokenisation arrive à un stade où il n’est pas possible de trouver un sous-mot dans le vocabulaire, le mot entier est tokenisé comme inconnu. Par exemple, <code>&quot;mug&quot;</code> serait tokenisé comme <code>[&quot;[UNK]&quot;]</code>, tout comme <code>&quot;bum&quot;</code> (même si on peut commencer par ” b ” et ” ##u ”, ” ##m ” ne fait pas partie du vocabulaire, et le <em>tokenizer</em> résultant sera simplement <code>[&quot;[UNK]&quot;]</code> ” et non <code>[&quot;b&quot;, &quot;##u&quot;, &quot;[UNK]&quot;]</code> ”). C’est une autre différence avec le BPE qui classerait seulement les caractères individuels qui ne sont pas dans le vocabulaire comme inconnus.</p>


<div class="course-tip  bg-gradient-to-br dark:bg-gradient-to-r before:border-green-500 dark:before:border-green-800 from-green-50 dark:from-gray-900 to-white dark:to-gray-950 border border-green-50 text-green-700 dark:text-gray-400"><p>✏️ <strong>A votre tour !</strong> Comment le mot <code>&quot;pugs&quot;</code> sera-t-il tokenisé ?</p></div>
<h2 class="relative group"><a id="implmentation-de-iwordpiecei" class="header-link block pr-1.5 text-lg no-hover:hidden with-hover:absolute with-hover:p-1.5 with-hover:opacity-0 with-hover:group-hover:opacity-100 with-hover:right-full" href="#implmentation-de-iwordpiecei"><span><svg class="" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 256 256"><path d="M167.594 88.393a8.001 8.001 0 0 1 0 11.314l-67.882 67.882a8 8 0 1 1-11.314-11.315l67.882-67.881a8.003 8.003 0 0 1 11.314 0zm-28.287 84.86l-28.284 28.284a40 40 0 0 1-56.567-56.567l28.284-28.284a8 8 0 0 0-11.315-11.315l-28.284 28.284a56 56 0 0 0 79.196 79.197l28.285-28.285a8 8 0 1 0-11.315-11.314zM212.852 43.14a56.002 56.002 0 0 0-79.196 0l-28.284 28.284a8 8 0 1 0 11.314 11.314l28.284-28.284a40 40 0 0 1 56.568 56.567l-28.285 28.285a8 8 0 0 0 11.315 11.314l28.284-28.284a56.065 56.065 0 0 0 0-79.196z" fill="currentColor"></path></svg></span></a>
	<span>Implémentation de <i>WordPiece</i></span></h2>

<p>Voyons maintenant une implémentation de l’algorithme <em>WordPiece</em>. Comme pour le BPE, il s’agit d’un exemple pédagogique et vous ne pourrez pas l’utiliser sur un grand corpus.</p>
<p>Nous utiliserons le même corpus que dans l’exemple BPE :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->corpus = [
    <span class="hljs-string">&quot;This is the Hugging Face Course.&quot;</span>,
    <span class="hljs-comment"># C&#x27;est le cours d&#x27;Hugging Face.</span>
    <span class="hljs-string">&quot;This chapter is about tokenization.&quot;</span>,
    <span class="hljs-comment"># This chapter is about tokenization</span>
    <span class="hljs-string">&quot;This section shows several tokenizer algorithms.&quot;</span>,
    <span class="hljs-comment"># Cette section présente plusieurs algorithmes de tokenizer.</span>
    <span class="hljs-string">&quot;Hopefully, you will be able to understand how they are trained and generate tokens.&quot;</span>,
    <span class="hljs-comment"># Avec un peu de chance, vous serez en mesure de comprendre comment ils sont entraînés et génèrent des tokens.</span>
]<!-- HTML_TAG_END --></pre></div>
<p>Tout d’abord, nous devons prétokéniser le corpus en mots. Puisque nous répliquons un <em>tokenizer WordPiece</em> (comme BERT), nous utiliserons le <em>tokenizer</em> <code>bert-base-cased</code> pour la prétokénisation :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-keyword">from</span> transformers <span class="hljs-keyword">import</span> AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained(<span class="hljs-string">&quot;bert-base-cased&quot;</span>)<!-- HTML_TAG_END --></pre></div>
<p>Ensuite, nous calculons les fréquences de chaque mot dans le corpus comme nous le faisons pour la prétokénisation :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-keyword">from</span> collections <span class="hljs-keyword">import</span> defaultdict

word_freqs = defaultdict(<span class="hljs-built_in">int</span>)
<span class="hljs-keyword">for</span> text <span class="hljs-keyword">in</span> corpus:
    words_with_offsets = tokenizer.backend_tokenizer.pre_tokenizer.pre_tokenize_str(text)
    new_words = [word <span class="hljs-keyword">for</span> word, offset <span class="hljs-keyword">in</span> words_with_offsets]
    <span class="hljs-keyword">for</span> word <span class="hljs-keyword">in</span> new_words:
        word_freqs[word] += <span class="hljs-number">1</span>

word_freqs<!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->defaultdict(
    <span class="hljs-built_in">int</span>, {<span class="hljs-string">&#x27;This&#x27;</span>: <span class="hljs-number">3</span>, <span class="hljs-string">&#x27;is&#x27;</span>: <span class="hljs-number">2</span>, <span class="hljs-string">&#x27;the&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;Hugging&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;Face&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;Course&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;.&#x27;</span>: <span class="hljs-number">4</span>, <span class="hljs-string">&#x27;chapter&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;about&#x27;</span>: <span class="hljs-number">1</span>,
    <span class="hljs-string">&#x27;tokenization&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;section&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;shows&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;several&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;tokenizer&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;algorithms&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;Hopefully&#x27;</span>: <span class="hljs-number">1</span>,
    <span class="hljs-string">&#x27;,&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;you&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;will&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;be&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;able&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;to&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;understand&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;how&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;they&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;are&#x27;</span>: <span class="hljs-number">1</span>,
    <span class="hljs-string">&#x27;trained&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;and&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;generate&#x27;</span>: <span class="hljs-number">1</span>, <span class="hljs-string">&#x27;tokens&#x27;</span>: <span class="hljs-number">1</span>})<!-- HTML_TAG_END --></pre></div>
<p>Comme nous l’avons vu précédemment, l’alphabet est l’unique ensemble composé de toutes les premières lettres des mots, et de toutes les autres lettres qui apparaissent dans les mots préfixés par <code>##</code> :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->alphabet = []
<span class="hljs-keyword">for</span> word <span class="hljs-keyword">in</span> word_freqs.keys():
    <span class="hljs-keyword">if</span> word[<span class="hljs-number">0</span>] <span class="hljs-keyword">not</span> <span class="hljs-keyword">in</span> alphabet:
        alphabet.append(word[<span class="hljs-number">0</span>])
    <span class="hljs-keyword">for</span> letter <span class="hljs-keyword">in</span> word[<span class="hljs-number">1</span>:]:
        <span class="hljs-keyword">if</span> <span class="hljs-string">f&quot;##<span class="hljs-subst">{letter}</span>&quot;</span> <span class="hljs-keyword">not</span> <span class="hljs-keyword">in</span> alphabet:
            alphabet.append(<span class="hljs-string">f&quot;##<span class="hljs-subst">{letter}</span>&quot;</span>)

alphabet.sort()
alphabet

<span class="hljs-built_in">print</span>(alphabet)<!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->[<span class="hljs-string">&#x27;##a&#x27;</span>, <span class="hljs-string">&#x27;##b&#x27;</span>, <span class="hljs-string">&#x27;##c&#x27;</span>, <span class="hljs-string">&#x27;##d&#x27;</span>, <span class="hljs-string">&#x27;##e&#x27;</span>, <span class="hljs-string">&#x27;##f&#x27;</span>, <span class="hljs-string">&#x27;##g&#x27;</span>, <span class="hljs-string">&#x27;##h&#x27;</span>, <span class="hljs-string">&#x27;##i&#x27;</span>, <span class="hljs-string">&#x27;##k&#x27;</span>, <span class="hljs-string">&#x27;##l&#x27;</span>, <span class="hljs-string">&#x27;##m&#x27;</span>, <span class="hljs-string">&#x27;##n&#x27;</span>, <span class="hljs-string">&#x27;##o&#x27;</span>, <span class="hljs-string">&#x27;##p&#x27;</span>, <span class="hljs-string">&#x27;##r&#x27;</span>, <span class="hljs-string">&#x27;##s&#x27;</span>,
 <span class="hljs-string">&#x27;##t&#x27;</span>, <span class="hljs-string">&#x27;##u&#x27;</span>, <span class="hljs-string">&#x27;##v&#x27;</span>, <span class="hljs-string">&#x27;##w&#x27;</span>, <span class="hljs-string">&#x27;##y&#x27;</span>, <span class="hljs-string">&#x27;##z&#x27;</span>, <span class="hljs-string">&#x27;,&#x27;</span>, <span class="hljs-string">&#x27;.&#x27;</span>, <span class="hljs-string">&#x27;C&#x27;</span>, <span class="hljs-string">&#x27;F&#x27;</span>, <span class="hljs-string">&#x27;H&#x27;</span>, <span class="hljs-string">&#x27;T&#x27;</span>, <span class="hljs-string">&#x27;a&#x27;</span>, <span class="hljs-string">&#x27;b&#x27;</span>, <span class="hljs-string">&#x27;c&#x27;</span>, <span class="hljs-string">&#x27;g&#x27;</span>, <span class="hljs-string">&#x27;h&#x27;</span>, <span class="hljs-string">&#x27;i&#x27;</span>, <span class="hljs-string">&#x27;s&#x27;</span>, <span class="hljs-string">&#x27;t&#x27;</span>, <span class="hljs-string">&#x27;u&#x27;</span>,
 <span class="hljs-string">&#x27;w&#x27;</span>, <span class="hljs-string">&#x27;y&#x27;</span>]<!-- HTML_TAG_END --></pre></div>
<p>Nous ajoutons également les <em>tokens</em> spéciaux utilisés par le modèle au début de ce vocabulaire. Dans le cas de BERT, il s’agit de la liste <code>[&quot;[PAD]&quot;, &quot;[UNK]&quot;, &quot;[CLS]&quot;, &quot;[SEP]&quot;, &quot;[MASK]&quot;]</code> :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->vocab = [<span class="hljs-string">&quot;[PAD]&quot;</span>, <span class="hljs-string">&quot;[UNK]&quot;</span>, <span class="hljs-string">&quot;[CLS]&quot;</span>, <span class="hljs-string">&quot;[SEP]&quot;</span>, <span class="hljs-string">&quot;[MASK]&quot;</span>] + alphabet.copy()<!-- HTML_TAG_END --></pre></div>
<p>Ensuite, nous devons diviser chaque mot, avec toutes les lettres qui ne sont pas les premières préfixées par <code>##</code> :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->splits = {
    word: [c <span class="hljs-keyword">if</span> i == <span class="hljs-number">0</span> <span class="hljs-keyword">else</span> <span class="hljs-string">f&quot;##<span class="hljs-subst">{c}</span>&quot;</span> <span class="hljs-keyword">for</span> i, c <span class="hljs-keyword">in</span> <span class="hljs-built_in">enumerate</span>(word)]
    <span class="hljs-keyword">for</span> word <span class="hljs-keyword">in</span> word_freqs.keys()
}<!-- HTML_TAG_END --></pre></div>
<p>Maintenant que nous sommes prêts pour l’entraînement, écrivons une fonction qui calcule le score de chaque paire. Nous devrons l’utiliser à chaque étape de l’entraînement :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-keyword">def</span> <span class="hljs-title function_">compute_pair_scores</span>(<span class="hljs-params">splits</span>):
    letter_freqs = defaultdict(<span class="hljs-built_in">int</span>)
    pair_freqs = defaultdict(<span class="hljs-built_in">int</span>)
    <span class="hljs-keyword">for</span> word, freq <span class="hljs-keyword">in</span> word_freqs.items():
        split = splits[word]
        <span class="hljs-keyword">if</span> <span class="hljs-built_in">len</span>(split) == <span class="hljs-number">1</span>:
            letter_freqs[split[<span class="hljs-number">0</span>]] += freq
            <span class="hljs-keyword">continue</span>
        <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> <span class="hljs-built_in">range</span>(<span class="hljs-built_in">len</span>(split) - <span class="hljs-number">1</span>):
            pair = (split[i], split[i + <span class="hljs-number">1</span>])
            letter_freqs[split[i]] += freq
            pair_freqs[pair] += freq
        letter_freqs[split[-<span class="hljs-number">1</span>]] += freq

    scores = {
        pair: freq / (letter_freqs[pair[<span class="hljs-number">0</span>]] * letter_freqs[pair[<span class="hljs-number">1</span>]])
        <span class="hljs-keyword">for</span> pair, freq <span class="hljs-keyword">in</span> pair_freqs.items()
    }
    <span class="hljs-keyword">return</span> scores<!-- HTML_TAG_END --></pre></div>
<p>Jetons un coup d’œil à une partie de ce dictionnaire après les premières divisions :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->pair_scores = compute_pair_scores(splits)
<span class="hljs-keyword">for</span> i, key <span class="hljs-keyword">in</span> <span class="hljs-built_in">enumerate</span>(pair_scores.keys()):
    <span class="hljs-built_in">print</span>(<span class="hljs-string">f&quot;<span class="hljs-subst">{key}</span>: <span class="hljs-subst">{pair_scores[key]}</span>&quot;</span>)
    <span class="hljs-keyword">if</span> i &gt;= <span class="hljs-number">5</span>:
        <span class="hljs-keyword">break</span><!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->(<span class="hljs-string">&#x27;T&#x27;</span>, <span class="hljs-string">&#x27;##h&#x27;</span>): <span class="hljs-number">0.125</span>
(<span class="hljs-string">&#x27;##h&#x27;</span>, <span class="hljs-string">&#x27;##i&#x27;</span>): <span class="hljs-number">0.03409090909090909</span>
(<span class="hljs-string">&#x27;##i&#x27;</span>, <span class="hljs-string">&#x27;##s&#x27;</span>): <span class="hljs-number">0.02727272727272727</span>
(<span class="hljs-string">&#x27;i&#x27;</span>, <span class="hljs-string">&#x27;##s&#x27;</span>): <span class="hljs-number">0.1</span>
(<span class="hljs-string">&#x27;t&#x27;</span>, <span class="hljs-string">&#x27;##h&#x27;</span>): <span class="hljs-number">0.03571428571428571</span>
(<span class="hljs-string">&#x27;##h&#x27;</span>, <span class="hljs-string">&#x27;##e&#x27;</span>): <span class="hljs-number">0.011904761904761904</span><!-- HTML_TAG_END --></pre></div>
<p>Maintenant, trouver la paire avec le meilleur score ne prend qu’une rapide boucle :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->best_pair = <span class="hljs-string">&quot;&quot;</span>
max_score = <span class="hljs-literal">None</span>
<span class="hljs-keyword">for</span> pair, score <span class="hljs-keyword">in</span> pair_scores.items():
    <span class="hljs-keyword">if</span> max_score <span class="hljs-keyword">is</span> <span class="hljs-literal">None</span> <span class="hljs-keyword">or</span> max_score &lt; score:
        best_pair = pair
        max_score = score

<span class="hljs-built_in">print</span>(best_pair, max_score)<!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->(<span class="hljs-string">&#x27;a&#x27;</span>, <span class="hljs-string">&#x27;##b&#x27;</span>) <span class="hljs-number">0.2</span><!-- HTML_TAG_END --></pre></div>
<p>Ainsi, la première fusion à apprendre est <code>(&#39;a&#39;, &#39;##b&#39;) -&gt; &#39;ab&#39;</code> et nous ajoutons <code>&#39;ab&#39;</code> au vocabulaire :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->vocab.append(<span class="hljs-string">&quot;ab&quot;</span>)<!-- HTML_TAG_END --></pre></div>
<p>Pour continuer, nous devons appliquer cette fusion dans notre dictionnaire <code>splits</code>. Écrivons une autre fonction pour cela :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-keyword">def</span> <span class="hljs-title function_">merge_pair</span>(<span class="hljs-params">a, b, splits</span>):
    <span class="hljs-keyword">for</span> word <span class="hljs-keyword">in</span> word_freqs:
        split = splits[word]
        <span class="hljs-keyword">if</span> <span class="hljs-built_in">len</span>(split) == <span class="hljs-number">1</span>:
            <span class="hljs-keyword">continue</span>
        i = <span class="hljs-number">0</span>
        <span class="hljs-keyword">while</span> i &lt; <span class="hljs-built_in">len</span>(split) - <span class="hljs-number">1</span>:
            <span class="hljs-keyword">if</span> split[i] == a <span class="hljs-keyword">and</span> split[i + <span class="hljs-number">1</span>] == b:
                merge = a + b[<span class="hljs-number">2</span>:] <span class="hljs-keyword">if</span> b.startswith(<span class="hljs-string">&quot;##&quot;</span>) <span class="hljs-keyword">else</span> a + b
                split = split[:i] + [merge] + split[i + <span class="hljs-number">2</span> :]
            <span class="hljs-keyword">else</span>:
                i += <span class="hljs-number">1</span>
        splits[word] = split
    <span class="hljs-keyword">return</span> splits<!-- HTML_TAG_END --></pre></div>
<p>Et nous pouvons regarder le résultat de la première fusion :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->splits = merge_pair(<span class="hljs-string">&quot;a&quot;</span>, <span class="hljs-string">&quot;##b&quot;</span>, splits)
splits[<span class="hljs-string">&quot;about&quot;</span>]<!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->[<span class="hljs-string">&#x27;ab&#x27;</span>, <span class="hljs-string">&#x27;##o&#x27;</span>, <span class="hljs-string">&#x27;##u&#x27;</span>, <span class="hljs-string">&#x27;##t&#x27;</span>]<!-- HTML_TAG_END --></pre></div>
<p>Nous avons maintenant tout ce dont nous avons besoin pour boucler jusqu’à ce que nous ayons appris toutes les fusions que nous voulons. Visons une taille de vocabulaire de 70 :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->vocab_size = <span class="hljs-number">70</span>
<span class="hljs-keyword">while</span> <span class="hljs-built_in">len</span>(vocab) &lt; vocab_size:
    scores = compute_pair_scores(splits)
    best_pair, max_score = <span class="hljs-string">&quot;&quot;</span>, <span class="hljs-literal">None</span>
    <span class="hljs-keyword">for</span> pair, score <span class="hljs-keyword">in</span> scores.items():
        <span class="hljs-keyword">if</span> max_score <span class="hljs-keyword">is</span> <span class="hljs-literal">None</span> <span class="hljs-keyword">or</span> max_score &lt; score:
            best_pair = pair
            max_score = score
    splits = merge_pair(*best_pair, splits)
    new_token = (
        best_pair[<span class="hljs-number">0</span>] + best_pair[<span class="hljs-number">1</span>][<span class="hljs-number">2</span>:]
        <span class="hljs-keyword">if</span> best_pair[<span class="hljs-number">1</span>].startswith(<span class="hljs-string">&quot;##&quot;</span>)
        <span class="hljs-keyword">else</span> best_pair[<span class="hljs-number">0</span>] + best_pair[<span class="hljs-number">1</span>]
    )
    vocab.append(new_token)<!-- HTML_TAG_END --></pre></div>
<p>Nous pouvons ensuite examiner le vocabulaire généré :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-built_in">print</span>(vocab)<!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->[<span class="hljs-string">&#x27;[PAD]&#x27;</span>, <span class="hljs-string">&#x27;[UNK]&#x27;</span>, <span class="hljs-string">&#x27;[CLS]&#x27;</span>, <span class="hljs-string">&#x27;[SEP]&#x27;</span>, <span class="hljs-string">&#x27;[MASK]&#x27;</span>, <span class="hljs-string">&#x27;##a&#x27;</span>, <span class="hljs-string">&#x27;##b&#x27;</span>, <span class="hljs-string">&#x27;##c&#x27;</span>, <span class="hljs-string">&#x27;##d&#x27;</span>, <span class="hljs-string">&#x27;##e&#x27;</span>, <span class="hljs-string">&#x27;##f&#x27;</span>, <span class="hljs-string">&#x27;##g&#x27;</span>, <span class="hljs-string">&#x27;##h&#x27;</span>, <span class="hljs-string">&#x27;##i&#x27;</span>, <span class="hljs-string">&#x27;##k&#x27;</span>,
 <span class="hljs-string">&#x27;##l&#x27;</span>, <span class="hljs-string">&#x27;##m&#x27;</span>, <span class="hljs-string">&#x27;##n&#x27;</span>, <span class="hljs-string">&#x27;##o&#x27;</span>, <span class="hljs-string">&#x27;##p&#x27;</span>, <span class="hljs-string">&#x27;##r&#x27;</span>, <span class="hljs-string">&#x27;##s&#x27;</span>, <span class="hljs-string">&#x27;##t&#x27;</span>, <span class="hljs-string">&#x27;##u&#x27;</span>, <span class="hljs-string">&#x27;##v&#x27;</span>, <span class="hljs-string">&#x27;##w&#x27;</span>, <span class="hljs-string">&#x27;##y&#x27;</span>, <span class="hljs-string">&#x27;##z&#x27;</span>, <span class="hljs-string">&#x27;,&#x27;</span>, <span class="hljs-string">&#x27;.&#x27;</span>, <span class="hljs-string">&#x27;C&#x27;</span>, <span class="hljs-string">&#x27;F&#x27;</span>, <span class="hljs-string">&#x27;H&#x27;</span>,
 <span class="hljs-string">&#x27;T&#x27;</span>, <span class="hljs-string">&#x27;a&#x27;</span>, <span class="hljs-string">&#x27;b&#x27;</span>, <span class="hljs-string">&#x27;c&#x27;</span>, <span class="hljs-string">&#x27;g&#x27;</span>, <span class="hljs-string">&#x27;h&#x27;</span>, <span class="hljs-string">&#x27;i&#x27;</span>, <span class="hljs-string">&#x27;s&#x27;</span>, <span class="hljs-string">&#x27;t&#x27;</span>, <span class="hljs-string">&#x27;u&#x27;</span>, <span class="hljs-string">&#x27;w&#x27;</span>, <span class="hljs-string">&#x27;y&#x27;</span>, <span class="hljs-string">&#x27;##fu&#x27;</span>, <span class="hljs-string">&#x27;Fa&#x27;</span>, <span class="hljs-string">&#x27;Fac&#x27;</span>, <span class="hljs-string">&#x27;##ct&#x27;</span>, <span class="hljs-string">&#x27;##ful&#x27;</span>, <span class="hljs-string">&#x27;##full&#x27;</span>, <span class="hljs-string">&#x27;##fully&#x27;</span>,
 <span class="hljs-string">&#x27;Th&#x27;</span>, <span class="hljs-string">&#x27;ch&#x27;</span>, <span class="hljs-string">&#x27;##hm&#x27;</span>, <span class="hljs-string">&#x27;cha&#x27;</span>, <span class="hljs-string">&#x27;chap&#x27;</span>, <span class="hljs-string">&#x27;chapt&#x27;</span>, <span class="hljs-string">&#x27;##thm&#x27;</span>, <span class="hljs-string">&#x27;Hu&#x27;</span>, <span class="hljs-string">&#x27;Hug&#x27;</span>, <span class="hljs-string">&#x27;Hugg&#x27;</span>, <span class="hljs-string">&#x27;sh&#x27;</span>, <span class="hljs-string">&#x27;th&#x27;</span>, <span class="hljs-string">&#x27;is&#x27;</span>, <span class="hljs-string">&#x27;##thms&#x27;</span>, <span class="hljs-string">&#x27;##za&#x27;</span>, <span class="hljs-string">&#x27;##zat&#x27;</span>,
 <span class="hljs-string">&#x27;##ut&#x27;</span>]<!-- HTML_TAG_END --></pre></div>
<p>Comme nous pouvons le voir, comparé à BPE, ce <em>tokenizer</em> apprend les parties de mots comme des <em>tokens</em> un peu plus rapidement.</p>


<div class="course-tip  bg-gradient-to-br dark:bg-gradient-to-r before:border-green-500 dark:before:border-green-800 from-green-50 dark:from-gray-900 to-white dark:to-gray-950 border border-green-50 text-green-700 dark:text-gray-400"><p>💡 Utiliser <code>train_new_from_iterator()</code> sur le même corpus ne donnera pas exactement le même vocabulaire. C’est parce que la bibliothèque 🤗 <em>Tokenizers</em> n’implémente pas <em>WordPiece</em> pour l’entraînement (puisque nous ne sommes pas complètement sûrs de son fonctionnement interne), mais utilise le BPE à la place.</p></div>
<p>Pour tokeniser un nouveau texte, on le prétokenise, on le divise, puis on applique l’algorithme de tokenisation sur chaque mot. En d’autres termes, nous recherchons le plus grand sous-mot commençant au début du premier mot et le divisons. Puis nous répétons le processus sur la deuxième partie et ainsi de suite pour le reste de ce mot et les mots suivants dans le texte :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-keyword">def</span> <span class="hljs-title function_">encode_word</span>(<span class="hljs-params">word</span>):
    tokens = []
    <span class="hljs-keyword">while</span> <span class="hljs-built_in">len</span>(word) &gt; <span class="hljs-number">0</span>:
        i = <span class="hljs-built_in">len</span>(word)
        <span class="hljs-keyword">while</span> i &gt; <span class="hljs-number">0</span> <span class="hljs-keyword">and</span> word[:i] <span class="hljs-keyword">not</span> <span class="hljs-keyword">in</span> vocab:
            i -= <span class="hljs-number">1</span>
        <span class="hljs-keyword">if</span> i == <span class="hljs-number">0</span>:
            <span class="hljs-keyword">return</span> [<span class="hljs-string">&quot;[UNK]&quot;</span>]
        tokens.append(word[:i])
        word = word[i:]
        <span class="hljs-keyword">if</span> <span class="hljs-built_in">len</span>(word) &gt; <span class="hljs-number">0</span>:
            word = <span class="hljs-string">f&quot;##<span class="hljs-subst">{word}</span>&quot;</span>
    <span class="hljs-keyword">return</span> tokens<!-- HTML_TAG_END --></pre></div>
<p>Testons-le sur un mot qui fait partie du vocabulaire, et un autre qui n’en fait pas partie :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-built_in">print</span>(encode_word(<span class="hljs-string">&quot;Hugging&quot;</span>))
<span class="hljs-built_in">print</span>(encode_word(<span class="hljs-string">&quot;HOgging&quot;</span>))<!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->[<span class="hljs-string">&#x27;Hugg&#x27;</span>, <span class="hljs-string">&#x27;##i&#x27;</span>, <span class="hljs-string">&#x27;##n&#x27;</span>, <span class="hljs-string">&#x27;##g&#x27;</span>]
[<span class="hljs-string">&#x27;[UNK]&#x27;</span>]<!-- HTML_TAG_END --></pre></div>
<p>Maintenant, écrivons une fonction qui permet de tokeniser un texte :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START --><span class="hljs-keyword">def</span> <span class="hljs-title function_">tokenize</span>(<span class="hljs-params">text</span>):
    pre_tokenize_result = tokenizer._tokenizer.pre_tokenizer.pre_tokenize_str(text)
    pre_tokenized_text = [word <span class="hljs-keyword">for</span> word, offset <span class="hljs-keyword">in</span> pre_tokenize_result]
    encoded_words = [encode_word(word) <span class="hljs-keyword">for</span> word <span class="hljs-keyword">in</span> pre_tokenized_text]
    <span class="hljs-keyword">return</span> <span class="hljs-built_in">sum</span>(encoded_words, [])<!-- HTML_TAG_END --></pre></div>
<p>On peut l’essayer sur n’importe quel texte :</p>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->tokenize(<span class="hljs-string">&quot;This is the Hugging Face Course!&quot;</span>)  <span class="hljs-comment"># C&#x27;est le cours d&#x27;Hugging Face</span><!-- HTML_TAG_END --></pre></div>

	<div class="code-block relative"><div class="absolute top-2.5 right-4"><button class="inline-flex items-center relative text-sm focus:text-green-500 cursor-pointer focus:outline-none transition duration-200 ease-in-out opacity-0 mx-0.5   text-gray-600 " title="code excerpt" type="button"><svg class="" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" fill="currentColor" focusable="false" role="img" width="1em" height="1em" preserveAspectRatio="xMidYMid meet" viewBox="0 0 32 32"><path d="M28,10V28H10V10H28m0-2H10a2,2,0,0,0-2,2V28a2,2,0,0,0,2,2H28a2,2,0,0,0,2-2V10a2,2,0,0,0-2-2Z" transform="translate(0)"></path><path d="M4,18H2V4A2,2,0,0,1,4,2H18V4H4Z" transform="translate(0)"></path><rect fill="none" width="32" height="32"></rect></svg>
	<div class="absolute pointer-events-none transition-opacity bg-black text-white py-1 px-2 leading-tight rounded font-normal shadow left-1/2 top-full transform -translate-x-1/2 translate-y-2 opacity-0"><div class="absolute bottom-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-black border-4 border-t-0" style="border-left-color: transparent; border-right-color: transparent; "></div>
	Copied</div></button></div>
	<pre><!-- HTML_TAG_START -->[<span class="hljs-string">&#x27;Th&#x27;</span>, <span class="hljs-string">&#x27;##i&#x27;</span>, <span class="hljs-string">&#x27;##s&#x27;</span>, <span class="hljs-string">&#x27;is&#x27;</span>, <span class="hljs-string">&#x27;th&#x27;</span>, <span class="hljs-string">&#x27;##e&#x27;</span>, <span class="hljs-string">&#x27;Hugg&#x27;</span>, <span class="hljs-string">&#x27;##i&#x27;</span>, <span class="hljs-string">&#x27;##n&#x27;</span>, <span class="hljs-string">&#x27;##g&#x27;</span>, <span class="hljs-string">&#x27;Fac&#x27;</span>, <span class="hljs-string">&#x27;##e&#x27;</span>, <span class="hljs-string">&#x27;c&#x27;</span>, <span class="hljs-string">&#x27;##o&#x27;</span>, <span class="hljs-string">&#x27;##u&#x27;</span>, <span class="hljs-string">&#x27;##r&#x27;</span>, <span class="hljs-string">&#x27;##s&#x27;</span>,
 <span class="hljs-string">&#x27;##e&#x27;</span>, <span class="hljs-string">&#x27;[UNK]&#x27;</span>]<!-- HTML_TAG_END --></pre></div>
<p>C’est tout pour l’algorithme <em>WordPiece</em> ! Maintenant, jetons un coup d’oeil à <em>Unigram</em>.</p>


		<script type="module" data-hydrate="1g7w7xb">
		import { start } from "/docs/course/pr_212/fr/_app/start-hf-doc-builder.js";
		start({
			target: document.querySelector('[data-hydrate="1g7w7xb"]').parentNode,
			paths: {"base":"/docs/course/pr_212/fr","assets":"/docs/course/pr_212/fr"},
			session: {},
			route: false,
			spa: false,
			trailing_slash: "never",
			hydrate: {
				status: 200,
				error: null,
				nodes: [
					import("/docs/course/pr_212/fr/_app/pages/__layout.svelte-hf-doc-builder.js"),
						import("/docs/course/pr_212/fr/_app/pages/chapter6/6.mdx-hf-doc-builder.js")
				],
				params: {}
			}
		});
	</script>
