{"id":1889,"date":"2020-12-27T08:33:11","date_gmt":"2020-12-27T08:33:11","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=1889"},"modified":"2020-12-28T01:04:11","modified_gmt":"2020-12-28T01:04:11","slug":"python-string-index","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-string-methods\/python-string-index\/","title":{"rendered":"Python String index()"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: in this tutorial, you&#8217;ll learn how to use the Python string <code>index()<\/code> method to get the index of a substring in a string.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='introduction-to-python-string-index-method'>Introduction to Python String index() method <a href=\"#introduction-to-python-string-index-method\" class=\"anchor\" id=\"introduction-to-python-string-index-method\" title=\"Anchor for Introduction to Python String index() method\">#<\/a><\/h2>\n\n\n\n<p>The string <code>index()<\/code> method returns the lowest index of a substring in a <a href=\"https:\/\/www.pythontutorial.net\/python-basics\/python-string\/\">string<\/a>.<\/p>\n\n\n\n<p>The following shows the syntax of the <code>index()<\/code> method:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"CSS\" data-shcb-language-slug=\"css\"><span><code class=\"hljs language-css\"><span class=\"hljs-selector-tag\">str<\/span><span class=\"hljs-selector-class\">.index<\/span>(<span class=\"hljs-selector-tag\">sub<\/span><span class=\"hljs-selector-attr\">&#91;, start&#91;, end]<\/span>])<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><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<p>The <code>index()<\/code> method has three parameters:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><code>sub<\/code> is the substring to search for in the <code>str<\/code>.<\/li><li><code>start<\/code> and <code>end<\/code> parameters are interpreted as in the <a href=\"https:\/\/www.pythontutorial.net\/advanced-python\/python-slicing\/\">slice notation<\/a> <code>str[start:end]<\/code>. The slice specifies where to look for the substring <code>sub<\/code>. Both <code>start<\/code> and <code>end<\/code> parameters are optional.<\/li><\/ul>\n\n\n\n<p>If the <code>str<\/code> doesn&#8217;t contain the substring <code>sub<\/code> within the slice <code>str[start:end]<\/code>, the <code>index()<\/code> method will raise a <code>ValueError<\/code>.<\/p>\n\n\n\n<p>If you don&#8217;t want to receive the <code>ValueError<\/code> when the <code>sub<\/code> is not found, you can use the string <code>find()<\/code> method instead. The <code>find()<\/code> method returns <code>-1<\/code> instead of raising the <code>ValueError<\/code>.<\/p>\n\n\n\n<p>Note that if you just want to check if a substring is in a string, you can use the <code>in<\/code> operator.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='python-string-index-method-examples'>Python string index() method examples <a href=\"#python-string-index-method-examples\" class=\"anchor\" id=\"python-string-index-method-examples\" title=\"Anchor for Python string index() method examples\">#<\/a><\/h2>\n\n\n\n<p>Let&#8217;s take some examples of using the <code>index()<\/code> method.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='1-using-the-python-string-index-method-to-find-the-position-of-a-substring-in-a-string'>1) Using the Python string index() method to find the position of a substring in a string <a href=\"#1-using-the-python-string-index-method-to-find-the-position-of-a-substring-in-a-string\" class=\"anchor\" id=\"1-using-the-python-string-index-method-to-find-the-position-of-a-substring-in-a-string\" title=\"Anchor for 1) Using the Python string index() method to find the position of a substring in a string\">#<\/a><\/h3>\n\n\n\n<p>The following example shows how to use the <code>index()<\/code> method to find the substring <code>'Python'<\/code> in the string <code>'Python will, Python will rock you.'<\/code>:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"PHP\" data-shcb-language-slug=\"php\"><span><code class=\"hljs language-php\">s = <span class=\"hljs-string\">'Python will, Python will rock you.'<\/span>\nposition = s.index(<span class=\"hljs-string\">'Python'<\/span>)\n\n<span class=\"hljs-keyword\">print<\/span>(position)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><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\"><span><code class=\"hljs\">0<\/code><\/span><\/pre>\n\n\n<p>Since the string has two substrings <code>'Python'<\/code>, the <code>index()<\/code> method returns the lowest index where the substring found in the string.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='2-using-the-python-string-index-method-to-find-the-position-of-a-substring-in-a-string-within-a-slice'>2) Using the Python string index() method to find the position of a substring in a string within a slice <a href=\"#2-using-the-python-string-index-method-to-find-the-position-of-a-substring-in-a-string-within-a-slice\" class=\"anchor\" id=\"2-using-the-python-string-index-method-to-find-the-position-of-a-substring-in-a-string-within-a-slice\" title=\"Anchor for 2) Using the Python string index() method to find the position of a substring in a string within a slice\">#<\/a><\/h3>\n\n\n\n<p>The following example uses the <code>index()<\/code> method to find the substring <code>'Python'<\/code> in the string <code>'Python will, Python will rock you.'<\/code> within the slice <code>str[1:]<\/code>:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-3\" data-shcb-language-name=\"PHP\" data-shcb-language-slug=\"php\"><span><code class=\"hljs language-php\">s = <span class=\"hljs-string\">'Python will, Python will rock you.'<\/span>\nposition = s.index(<span class=\"hljs-string\">'Python'<\/span>, <span class=\"hljs-number\">1<\/span>)\n\n<span class=\"hljs-keyword\">print<\/span>(position)<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><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\"><span><code class=\"hljs\">13<\/code><\/span><\/pre>\n\n\n<p>In this example, the <code>index()<\/code> method returns the position of the second occurrence of the substring in the string.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id='3-the-substring-doesnt-exist-in-the-string-example'>3) The substring doesn&#8217;t exist in the string example <a href=\"#3-the-substring-doesnt-exist-in-the-string-example\" class=\"anchor\" id=\"3-the-substring-doesnt-exist-in-the-string-example\" title=\"Anchor for 3) The substring doesn&#039;t exist in the string example\">#<\/a><\/h3>\n\n\n\n<p>The following example raises a <code>ValueError<\/code> because the substring <code>'Java'<\/code> doesn&#8217;t exist in the string <code>'Python will, Python will rock you.'<\/code>:<\/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\">s = <span class=\"hljs-string\">'Python will, Python will rock you.'<\/span>\nposition = s.index(<span class=\"hljs-string\">'Java'<\/span>)\n\n<span class=\"hljs-keyword\">print<\/span>(position)<\/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>Output:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-5\" data-shcb-language-name=\"HTTP\" data-shcb-language-slug=\"http\"><span><code class=\"hljs language-http\"><span class=\"hljs-attribute\">ValueError<\/span>: substring not found<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-5\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">HTTP<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">http<\/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 <code>index()<\/code> to get the lowest index of a substring within a string.<\/li><li>The <code>index()<\/code> method raises a <code>ValueError<\/code> if the string doesn&#8217;t contain the substring.<\/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=\"1889\"\n\t\t\t\tdata-post-url=\"https:\/\/www.pythontutorial.net\/python-string-methods\/python-string-index\/\"\n\t\t\t\tdata-post-title=\"Python String 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