mirror of
https://github.com/arthur-pbty/nsi.git
synced 2026-06-03 23:36:19 +02:00
Tutur33
172 lines
8.2 KiB
HTML
172 lines
8.2 KiB
HTML
|
||
|
||
<html>
|
||
|
||
<head>
|
||
<title>Immuable vs mutable</title>
|
||
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
|
||
<meta name="generator" content="HelpNDoc Personal Edition 6.3.0.298">
|
||
<meta name="description" content="" />
|
||
<meta name="keywords" content="">
|
||
|
||
|
||
|
||
<link type="text/css" rel="stylesheet" media="all" href="css/reset.css" />
|
||
<link type="text/css" rel="stylesheet" media="all" href="css/base.css" />
|
||
<link type="text/css" rel="stylesheet" media="all" href="css/hnd.css" />
|
||
<!--[if lte IE 8]>
|
||
<link type="text/css" rel="stylesheet" media="all" href="css/ielte8.css" />
|
||
<![endif]-->
|
||
<style type="text/css">
|
||
#topic_header
|
||
{
|
||
background-color: #EFEFEF;
|
||
}
|
||
</style>
|
||
<script type="text/javascript" src="js/jquery.min.js"></script>
|
||
<script type="text/javascript" src="js/hnd.js"></script>
|
||
<script type="text/javascript">
|
||
$(document).ready(function()
|
||
{
|
||
if (top.frames.length == 0)
|
||
{
|
||
var sTopicUrl = top.location.href.substring(top.location.href.lastIndexOf("/") + 1, top.location.href.length);
|
||
top.location.href = "Activite_decouverte_Python.hml.html?" + sTopicUrl;
|
||
}
|
||
else
|
||
{
|
||
var bTocSelected = false;
|
||
(function waitForTOC()
|
||
{
|
||
if (top && top.FrameTOC && top.FrameTOC.SelectTocItem)
|
||
{
|
||
top.FrameTOC.SelectTocItem("Immuablevsmutable");
|
||
bTocSelected = true;
|
||
}
|
||
if (!bTocSelected) setTimeout(function() { waitForTOC(); }, 300);
|
||
})();
|
||
}
|
||
});
|
||
</script>
|
||
|
||
|
||
</head>
|
||
|
||
<body>
|
||
|
||
|
||
|
||
|
||
<div id="topic_header">
|
||
<div id="topic_header_content">
|
||
<h1 id="topic_header_text">Immuable vs mutable</h1>
|
||
|
||
|
||
<div id="topic_breadcrumb">
|
||
<a href="Variablestypesetoperateurs.html">Variables, types et opérateurs</a> ››
|
||
</div>
|
||
|
||
</div>
|
||
|
||
<div id="topic_header_nav">
|
||
|
||
|
||
<a href="Variablestypesetoperateurs.html"><img src="img/arrow_up.png" alt="Parent"/></a>
|
||
|
||
|
||
|
||
<a href="Letypedictdictionnaire.html"><img src="img/arrow_left.png" alt="Previous"/></a>
|
||
|
||
|
||
|
||
<a href="Autrestypes.html"><img src="img/arrow_right.png" alt="Next"/></a>
|
||
|
||
|
||
</div>
|
||
|
||
<div class="clear"></div>
|
||
</div>
|
||
|
||
|
||
<div id="topic_content">
|
||
|
||
<p></p>
|
||
<ul style="text-indent: 0px; padding: 0; margin: 0 0 0 24px; list-style-position: outside; list-style-type: disc;">
|
||
<li class="rvps2"><span class="rvts67">Immuable ou mutable</span></li>
|
||
</ul>
|
||
<p class="rvps2"><span class="rvts25">Les </span><span class="rvts35">nombres </span><span class="rvts25">sont des </span><span class="rvts35">types immuables</span><span class="rvts25"> tout comme les </span><span class="rvts35">chaînes de caractères</span><span class="rvts25"> et les </span><span class="rvts35">tuples</span><span class="rvts25">. </span></p>
|
||
<p class="rvps2"><span class="rvts25">Une variable de type immuable ne peut être modifiée. Une opération sur une variable de ce type entraîne nécessairement la création d’une autre variable du même type.</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25">Pour mettre en évidence cette propriété, jouons avec la fonction </span><span class="rvts35">id()</span><span class="rvts25"> qui renvoie l'identificateur unique d'un objet, cela correspond à l'adresse mémoire dans laquelle il est stocké. </span></p>
|
||
<p class="rvps2"><span class="rvts25">Si l'identifiant est le même, c'est le même objet.</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts11">Vous allez vérifier cela dans la Console Python (interpréteur Python en mode interactif) </span></p>
|
||
<p class="rvps2"><span class="rvts67"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> a = 1</span><br/><span class="rvts66">>>> id(a)</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> a += 2</span><br/><span class="rvts66">>>> print(a)</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> id(a)</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> b = a</span><br/><span class="rvts66">>>> id(b)</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25">Donner plusieurs noms à un même objet s'appelle l'</span><span class="rvts35">aliasing, </span><span class="rvts25">les variables </span><span class="rvts35">a</span><span class="rvts25"> et </span><span class="rvts35">b</span><span class="rvts25"> sont des</span><span class="rvts35"> alias </span><span class="rvts25">l'une de l'autre. </span><span class="rvts35">a</span><span class="rvts25"> et </span><span class="rvts35">b</span><span class="rvts25"> pointent vers le même emplacement mémoire</span></p>
|
||
<p class="rvps2"><span class="rvts35"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> b = 5</span><br/><span class="rvts66">>>> a</span></p>
|
||
<p class="rvps2"><span class="rvts35"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> b</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> id(a)</span></p>
|
||
<p class="rvps2"><span class="rvts67"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> id(a)</span></p>
|
||
<p class="rvps2"><span class="rvts67"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25">Conclusion, l'aliasing se fait sans risque.</span></p>
|
||
<p class="rvps2"><span class="rvts67"><br/></span></p>
|
||
<ul style="text-indent: 0px; padding: 0; margin: 0 0 0 24px; list-style-position: outside; list-style-type: disc;">
|
||
<li class="rvps2"><span class="rvts67">Mutable</span></li>
|
||
</ul>
|
||
<p class="rvps2"><span class="rvts25">Un objet de type </span><span class="rvts35">mutable</span><span class="rvts25"> peut être modifié et modifié in situ. Aucune copie implicite n'est faite.</span></p>
|
||
<p class="rvps2"><span class="rvts25">Cette catégorie comprend: les </span><span class="rvts35">listes</span><span class="rvts25">, les </span><span class="rvts35">dictionnaires</span><span class="rvts25">, ...</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> liste1 = []</span><br/><span class="rvts66">>>> id(liste1)</span></p>
|
||
<p class="rvps2"><span class="rvts67"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> liste1.append('Nicolas')</span><br/><span class="rvts66">>>> liste1</span></p>
|
||
<p class="rvps2"><span class="rvts67"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> id(liste1)</span></p>
|
||
<p class="rvps2"><span class="rvts67"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25">La valeur de liste peut être modifié mais liste ne change pas d'id.</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25">Si un objet doit être souvent modifié, un type mutable est préférable qu'un type immuable d'un point de vue espace mémoire mais attention à l'aliasing par exemple:</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> liste2 = liste1</span><br/><span class="rvts66">>>> id(liste2)</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> liste2.append(3)</span><br/><span class="rvts66">>>> liste2</span></p>
|
||
<p class="rvps10"><span class="rvts66">>>> liste1</span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p class="rvps2"><span class="rvts25"><br/></span></p>
|
||
<p></p>
|
||
<p class="rvps4" style="clear: both;"><span class="rvts15">Créé avec HelpNDoc Personal Edition: </span><a class="rvts16" href="https://www.helpndoc.com/fr">Générateur de documentation complet</a></p>
|
||
|
||
</div>
|
||
|
||
|
||
<div id="topic_footer">
|
||
|
||
<div id="topic_footer_content">
|
||
|
||
</div>
|
||
</div>
|
||
|
||
|
||
|
||
|
||
</body>
|
||
|
||
</html>
|
||
|