{"id":4282,"date":"2022-08-09T01:24:25","date_gmt":"2022-08-09T01:24:25","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=4282"},"modified":"2022-08-09T01:34:35","modified_gmt":"2022-08-09T01:34:35","slug":"fancy-indexing","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-numpy\/fancy-indexing\/","title":{"rendered":"Fancy Indexing"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: in this tutorial, you&#8217;ll learn about the fancy indexing technique to select elements of a numpy array.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='introduction-to-fancy-indexing'>Introduction to fancy indexing <a href=\"#introduction-to-fancy-indexing\" class=\"anchor\" id=\"introduction-to-fancy-indexing\" title=\"Anchor for Introduction to fancy indexing\">#<\/a><\/h2>\n\n\n\n<p>In the previous tutorial, you learned how to select elements from a numpy array using <a href=\"https:\/\/www.pythontutorial.net\/python-numpy\/numpy-array-indexing\/\">indexing<\/a> and <a href=\"https:\/\/www.pythontutorial.net\/python-numpy\/numpy-array-slicing\/\">slicing<\/a> techniques.<\/p>\n\n\n\n<p>Besides using indexing &amp; slicing, NumPy provides you with a convenient way to index an array called <em>fancy indexing<\/em>.<\/p>\n\n\n\n<p>Fancy indexing allows you to index a numpy array using the following:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Another numpy array<\/li><li>A Python <a href=\"https:\/\/www.pythontutorial.net\/python-basics\/python-list\/\">list<\/a><\/li><li>A <a href=\"https:\/\/www.pythontutorial.net\/advanced-python\/python-sequences\/\">sequence<\/a> of integers<\/li><\/ul>\n\n\n\n<p>Let&#8217;s see the following example:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"PHP\" data-shcb-language-slug=\"php\"><span><code class=\"hljs language-php\">import numpy <span class=\"hljs-keyword\">as<\/span> np\r\n\r\na = np.arange(<span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">10<\/span>)\r\n<span class=\"hljs-keyword\">print<\/span>(a)\r\n\r\nindices = np.<span class=\"hljs-keyword\">array<\/span>(&#91;<span class=\"hljs-number\">2<\/span>, <span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>])\r\n<span class=\"hljs-keyword\">print<\/span>(a&#91;indices])<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PHP<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">php<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Output:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"JSON \/ JSON with Comments\" data-shcb-language-slug=\"json\"><span><code class=\"hljs language-json\">&#91;<span class=\"hljs-number\">1<\/span> <span class=\"hljs-number\">2<\/span> <span class=\"hljs-number\">3<\/span> <span class=\"hljs-number\">4<\/span> <span class=\"hljs-number\">5<\/span> <span class=\"hljs-number\">6<\/span> <span class=\"hljs-number\">7<\/span> <span class=\"hljs-number\">8<\/span> <span class=\"hljs-number\">9<\/span>]\r\n&#91;<span class=\"hljs-number\">3<\/span> <span class=\"hljs-number\">4<\/span> <span class=\"hljs-number\">5<\/span>]<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">JSON \/ JSON with Comments<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">json<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>How it works.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/www.pythontutorial.net\/wp-content\/uploads\/2022\/08\/numpy-fancy-indexing.svg\" alt=\"Numpy Fancy Indexing\" class=\"wp-image-4285\"\/><\/figure>\n\n\n\n<p>First, use the <a href=\"https:\/\/www.pythontutorial.net\/python-numpy\/numpy-arange\/\">arange()<\/a> function to create a numpy array that includes numbers from 1 to 9:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-3\" data-shcb-language-name=\"JSON \/ JSON with Comments\" data-shcb-language-slug=\"json\"><span><code class=\"hljs language-json\">&#91;<span class=\"hljs-number\">1<\/span> <span class=\"hljs-number\">2<\/span> <span class=\"hljs-number\">3<\/span> <span class=\"hljs-number\">4<\/span> <span class=\"hljs-number\">5<\/span> <span class=\"hljs-number\">6<\/span> <span class=\"hljs-number\">7<\/span> <span class=\"hljs-number\">8<\/span> <span class=\"hljs-number\">9<\/span>]<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">JSON \/ JSON with Comments<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">json<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Second, create a second numpy array for indexing:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-4\" data-shcb-language-name=\"PHP\" data-shcb-language-slug=\"php\"><span><code class=\"hljs language-php\">indices = np.<span class=\"hljs-keyword\">array<\/span>(&#91;<span class=\"hljs-number\">2<\/span>, <span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>])<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-4\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">PHP<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">php<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Third, use the <code>indices<\/code> array for indexing the <code>a<\/code> array:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-5\" data-shcb-language-name=\"CSS\" data-shcb-language-slug=\"css\"><span><code class=\"hljs language-css\"><span class=\"hljs-selector-tag\">print<\/span>(<span class=\"hljs-selector-tag\">a<\/span><span class=\"hljs-selector-attr\">&#91;indices]<\/span>)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-5\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">CSS<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">css<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<h2 class=\"wp-block-heading\" id='summary'>Summary <a href=\"#summary\" class=\"anchor\" id=\"summary\" title=\"Anchor for Summary\">#<\/a><\/h2>\n\n\n\n<ul class=\"wp-block-list\"><li>Fancy indexing allows you to index an array using another array, a list, or a sequence of integers.<\/li><\/ul>\n<div class=\"helpful-block-content\" data-title=\"\">\n\t<header>\n\t\t<div class=\"wth-question\">Was this tutorial helpful ?<\/div>\n\t\t<div class=\"wth-thumbs\">\n\t\t\t<button\n\t\t\t\tdata-post=\"4282\"\n\t\t\t\tdata-post-url=\"https:\/\/www.pythontutorial.net\/python-numpy\/fancy-indexing\/\"\n\t\t\t\tdata-post-title=\"Fancy Indexing\"\n\t\t\t\tdata-response=\"1\"\n\t\t\t\tclass=\"wth-btn-rounded wth-yes-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t\tclass=\"feather feather-thumbs-up block w-full h-full\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M14 9V5a3 3 0 0 0-3-3l-4 9v11h11.28a2 2 0 0 0 2-1.7l1.38-9a2 2 0 0 0-2-2.3zM7 22H4a2 2 0 0 1-2-2v-7a2 2 0 0 1 2-2h3\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t<button\n\t\t\t\tdata-response=\"0\"\n\t\t\t\tdata-post=\"4282\"\n\t\t\t\tdata-post-url=\"https:\/\/www.pythontutorial.net\/python-numpy\/fancy-indexing\/\"\n\t\t\t\tdata-post-title=\"Fancy Indexing\"\n\t\t\t\tclass=\"wth-btn-rounded wth-no-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M10 15v4a3 3 0 0 0 3 3l4-9V2H5.72a2 2 0 0 0-2 1.7l-1.38 9a2 2 0 0 0 2 2.3zm7-13h2.67A2.31 2.31 0 0 1 22 4v7a2.31 2.31 0 0 1-2.33 2H17\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t<div class=\"wth-form hidden\">\n\t\t<div class=\"wth-form-wrapper\">\n\t\t\t<div class=\"wth-title\"><\/div>\n\t\t\t<textarea class=\"wth-message\"><\/textarea>\n\t\t\t<input type=\"button\" name=\"wth-submit\" class=\"wth-btn wth-btn-submit\" id=\"wth-submit\" \/>\n\t\t\t<input type=\"button\" class=\"wth-btn wth-btn-cancel\" value=\"Cancel\" \/>\n\t\t<\/div>\n\t<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>In this tutorial, you&#8217;ll learn about the fancy indexing technique to select elements of a numpy array.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":3406,"menu_order":8,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-4282","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/pages\/4282","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/comments?post=4282"}],"version-history":[{"count":0,"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/pages\/4282\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/pages\/3406"}],"wp:attachment":[{"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/media?parent=4282"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}