{"id":4425,"date":"2022-08-11T00:44:00","date_gmt":"2022-08-11T00:44:00","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=4425"},"modified":"2022-08-11T00:44:50","modified_gmt":"2022-08-11T00:44:50","slug":"numpy-flatten","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-numpy\/numpy-flatten\/","title":{"rendered":"NumPy flatten()"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: in this tutorial, you&#8217;ll learn how to use the numpy <code>flatten()<\/code> method to return a copy of an array collapsed into one dimension.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='introduction-to-the-numpy-flatten-method'>Introduction to the NumPy flatten() method <a href=\"#introduction-to-the-numpy-flatten-method\" class=\"anchor\" id=\"introduction-to-the-numpy-flatten-method\" title=\"Anchor for Introduction to the NumPy flatten() method\">#<\/a><\/h2>\n\n\n\n<p>The <code><code>flatten()<\/code><\/code> is a method of the <code><a href=\"https:\/\/www.pythontutorial.net\/python-numpy\/create-numpy-array\/\">ndarray<\/a><\/code> class. The <code><code>flatten()<\/code><\/code> method returns a <a href=\"https:\/\/www.pythontutorial.net\/python-numpy\/numpy-copy\/\">copy of an array<\/a> collapsed into one dimension.<\/p>\n\n\n\n<p>The following shows the syntax of the <code>flatten()<\/code> method:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">ndarray.flatten(order=<span class=\"hljs-string\">'C'<\/span>)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>The order parameter specifies the order of elements of an array in the returned array. It accepts one of the following values:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>&#8216;C&#8217; means to flatten array elements into row-major order (C-style).<\/li><li>&#8216;F&#8217; means to flatten array elements into column-major order (Fortran-style).<\/li><li>&#8216;A&#8217; &#8211; means to flatten array elements in column-major order if a is Fortran contiguous in memory or row-major otherwise.<\/li><li>&#8216;K&#8217; means to flatten array elements in order of the elements laid out in memory.<\/li><\/ul>\n\n\n\n<p>By default, the order is &#8216;C&#8217; which flattens the array elements into row-major.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='numpy-flatten-method-examples'>NumPy flatten() method examples <a href=\"#numpy-flatten-method-examples\" class=\"anchor\" id=\"numpy-flatten-method-examples\" title=\"Anchor for NumPy flatten() method examples\">#<\/a><\/h2>\n\n\n\n<p>Let&#8217;s take some examples of using the NumPy <code>flatten()<\/code> method.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='1-using-flatten-method-example-with-a-multidimensional-array'>1) Using flatten() method example with a multidimensional array <a href=\"#1-using-flatten-method-example-with-a-multidimensional-array\" class=\"anchor\" id=\"1-using-flatten-method-example-with-a-multidimensional-array\" title=\"Anchor for 1) Using flatten() method example with a multidimensional array\">#<\/a><\/h3>\n\n\n\n<p>The following example uses the <code>flatten()<\/code> method to return a 1-D array from a 2-D array:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\"><span class=\"hljs-keyword\">import<\/span> numpy <span class=\"hljs-keyword\">as<\/span> np\n\na = np.array(&#91;&#91;<span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">2<\/span>], &#91;<span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>]])\nb = a.flatten()\nprint(b)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/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-3\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">&#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>]<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/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-flatten-row-major-order.svg\" alt=\"NumPy flatten\" class=\"wp-image-4427\"\/><\/figure>\n\n\n\n<p>First, create a 2-D array that has two rows and two columns:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-4\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">a = np.array(&#91;&#91;<span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">2<\/span>], &#91;<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\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Second, return a copy of the array with dimensions collapsed into one using the <code>flatten()<\/code> method:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-5\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">b = a.flatten()<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-5\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Third, display the result array:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-6\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">print(b)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-6\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Note that b is a copy, not a view of the array a. If you change elements in array b, the elements in array a are not changed. For example:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-7\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\"><span class=\"hljs-keyword\">import<\/span> numpy <span class=\"hljs-keyword\">as<\/span> np\n\na = np.array(&#91;&#91;<span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">2<\/span>], &#91;<span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>]])\nb = a.flatten()\n\n<span class=\"hljs-comment\"># change element at index 0<\/span>\nb&#91;<span class=\"hljs-number\">0<\/span>] = <span class=\"hljs-number\">0<\/span>\nprint(b)\n\n<span class=\"hljs-comment\"># display the array a<\/span>\nprint(a)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-7\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/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-8\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">&#91;<span class=\"hljs-number\">0<\/span> <span class=\"hljs-number\">2<\/span> <span class=\"hljs-number\">3<\/span> <span class=\"hljs-number\">4<\/span>]\n&#91;&#91;<span class=\"hljs-number\">1<\/span> <span class=\"hljs-number\">2<\/span>]\n &#91;<span class=\"hljs-number\">3<\/span> <span class=\"hljs-number\">4<\/span>]]<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-8\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>In this example:<\/p>\n\n\n\n<p>First, flatten the array a and assign the result array to b variable:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-9\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">b = a.flatten()<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-9\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Second, change the element at index 0 of b to zero and print out b:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-10\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">b&#91;<span class=\"hljs-number\">0<\/span>] = <span class=\"hljs-number\">0<\/span>\nprint(b)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-10\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Third, display the array a:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-11\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">print(a)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-11\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>The output shows that the element at index 0 of b changes but the element at index 0 of a doesn&#8217;t change.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='2-using-numpy-flatten-method-to-flatten-an-array-using-column-major-order'>2) Using numpy flatten() method to flatten an array using column-major order <a href=\"#2-using-numpy-flatten-method-to-flatten-an-array-using-column-major-order\" class=\"anchor\" id=\"2-using-numpy-flatten-method-to-flatten-an-array-using-column-major-order\" title=\"Anchor for 2) Using numpy flatten() method to flatten an array using column-major order\">#<\/a><\/h3>\n\n\n\n<p>The following example uses the numpy <code>flatten()<\/code> method to flatten an array using column-major order:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-12\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\"><span class=\"hljs-keyword\">import<\/span> numpy <span class=\"hljs-keyword\">as<\/span> np\n\na = np.array(&#91;&#91;<span class=\"hljs-number\">1<\/span>, <span class=\"hljs-number\">2<\/span>], &#91;<span class=\"hljs-number\">3<\/span>, <span class=\"hljs-number\">4<\/span>]])\nb = a.flatten(order=<span class=\"hljs-string\">'F'<\/span>)\n\nprint(b)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-12\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/www.pythontutorial.net\/wp-content\/uploads\/2022\/08\/numpy-flatten-column-major-order-F.svg\" alt=\"numpy flatten column-major order F\" class=\"wp-image-4430\"\/><\/figure>\n\n\n\n<p>Output:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-13\" data-shcb-language-name=\"Python\" data-shcb-language-slug=\"python\"><span><code class=\"hljs language-python\">&#91;<span class=\"hljs-number\">1<\/span> <span class=\"hljs-number\">3<\/span> <span class=\"hljs-number\">2<\/span> <span class=\"hljs-number\">4<\/span>]<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-13\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">Python<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">python<\/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>Use the numpy array <code>flatten()<\/code> method to return a copy of an array collapsed into one dimension.<\/li><\/ul>\n<div class=\"helpful-block-content\" data-title=\"\">\n\t<header>\n\t\t<div class=\"wth-question\">Was this 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Introduction to the NumPy flatten() method # The flatten() is a method of the ndarray class. The flatten() method returns a copy of an array collapsed into one dimension. The following [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":3406,"menu_order":23,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-4425","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/pages\/4425","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=4425"}],"version-history":[{"count":0,"href":"https:\/\/www.pythontutorial.net\/wp-json\/wp\/v2\/pages\/4425\/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=4425"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}