{"id":6942,"date":"2022-09-06T01:13:27","date_gmt":"2022-09-05T19:43:27","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-list-of-even-numbers-at-even-number-indexes-using-list-comprehension-closed\/"},"modified":"2022-09-06T01:13:27","modified_gmt":"2022-09-05T19:43:27","slug":"solved-list-of-even-numbers-at-even-number-indexes-using-list-comprehension-closed","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-list-of-even-numbers-at-even-number-indexes-using-list-comprehension-closed\/","title":{"rendered":"[Solved] List of even numbers at even number indexes using list comprehension [closed]"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-29349373\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"29349373\" data-parentid=\"29349259\" data-score=\"1\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>I wasn&#8217;t able to figure out exactly what you were looking for from your post, but here&#8217;s what I think you want:<\/p>\n<p>Given a list, get all the numbers at even indices. If any of these numbers are even, put them in a new list and return it:<\/p>\n<pre><code>In [10]: L = [3,1,54,5,2,3,4,5,6,5,2,5,3,2,5,2,2,5,2,5,2]\n\nIn [11]: [num for i,num in enumerate(L) if not num%2 and not i%2]\nOut[11]: [54, 2, 4, 6, 2, 2, 2, 2]\n<\/code><\/pre>\n<p>If you want to add <code>0<\/code>s in between, then you can do a little <code>itertools<\/code> magic:<\/p>\n<pre><code>In [12]: list(itertools.chain.from_iterable(zip((num for i,num in enumerate(L) if not num%2 and not i%2), itertools.cycle([0]))))[:-1]\nOut[12]: [54, 0, 2, 0, 4, 0, 6, 0, 2, 0, 2, 0, 2, 0, 2]\n<\/code><\/pre>\n<p>Ok, that was a lot of brackets and parentheses, so let&#8217;s take a closer look at it:<\/p>\n<ol>\n<li>\n<p><code>list(...)[:-1]<\/code> converts <code>...<\/code> into a <code>list<\/code> and gets all but the last element of that list. This is similar to what you were trying to do when you added <code>0<\/code>s and removed the last one<\/p>\n<\/li>\n<li>\n<p><code>(num for i,num in enumerate(L) if not num%2 and not i%2)<\/code> is the same as what it was before the edit, except that it uses parentheses (<code>()<\/code>) instead of brackets (<code>[]<\/code>). This turns it into a generator-comprehension, as opposed to a list comprehension &#8211; it only matters in that it performs a little bit of optimization &#8211; the values are not computed until they are needed (until <code>zip<\/code> asks for the next value)<\/p>\n<\/li>\n<li>\n<p><code>itertools.cycle([0])<\/code> gives an endless list of <code>0<\/code>s<\/p>\n<\/li>\n<li>\n<p><code>zip(A, B)<\/code> returns a list of tuples, in which the <code>i<\/code>th tuple has two elements &#8211; the <code>i<\/code>th element of <code>A<\/code>, and the <code>i<\/code>th element of <code>B<\/code><\/p>\n<\/li>\n<li>\n<p><code>itertools.chain.from_iterable(zip(A, B))<\/code> returns the elements of <code>A<\/code> and <code>B<\/code> interleaved, as a generator. In essence, it&#8217;s like doing this:<\/p>\n<\/li>\n<\/ol>\n<pre>\n\ndef someFunc(A, B):\n    for i in range(len(A)):\n        yield A[i]\n        yield B[i]\n\n<\/pre>\n<p>Thus, all of these put together give you exactly what you want<\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">2<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved List of even numbers at even number indexes using list comprehension [closed] <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] I wasn&#8217;t able to figure out exactly what you were looking for from your post, but here&#8217;s what I think you want: Given a list, get all the numbers at even indices. If any of these numbers are even, put them in a new list and return it: In [10]: L = [3,1,54,5,2,3,4,5,6,5,2,5,3,2,5,2,2,5,2,5,2] In &#8230; <a title=\"[Solved] List of even numbers at even number indexes using list comprehension [closed]\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-list-of-even-numbers-at-even-number-indexes-using-list-comprehension-closed\/\" aria-label=\"More on [Solved] List of even numbers at even number indexes using list comprehension [closed]\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[1941,349],"class_list":["post-6942","post","type-post","status-publish","format-standard","hentry","category-solved","tag-list-comprehension","tag-python"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] List of even numbers at even number indexes using list comprehension [closed] - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-list-of-even-numbers-at-even-number-indexes-using-list-comprehension-closed\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] List of even numbers at even number indexes using list comprehension [closed] - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] I wasn&#8217;t able to figure out exactly what you were looking for from your post, but here&#8217;s what I think you want: Given a list, get all the numbers at even indices. If any of these numbers are even, put them in a new list and return it: In [10]: L = [3,1,54,5,2,3,4,5,6,5,2,5,3,2,5,2,2,5,2,5,2] In ... 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If any of these numbers are even, put them in a new list and return it: In [10]: L = [3,1,54,5,2,3,4,5,6,5,2,5,3,2,5,2,2,5,2,5,2] In ... 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