[{"data":1,"prerenderedAt":1918},["ShallowReactive",2],{"doc-\u002Fexamples\u002Fpython-list-processing-example":3},{"id":4,"title":5,"body":6,"description":1911,"extension":1912,"meta":1913,"navigation":111,"path":1914,"seo":1915,"stem":1916,"__hash__":1917},"content\u002Fexamples\u002Fpython-list-processing-example.md","Python List Processing Example",{"type":7,"value":8,"toc":1893},"minimark",[9,13,17,20,44,47,52,348,351,355,358,375,383,387,390,423,426,453,464,468,474,534,537,567,570,588,595,602,671,675,678,681,783,785,803,806,829,832,846,853,857,860,865,955,957,991,996,999,1003,1006,1009,1033,1036,1167,1169,1214,1217,1235,1239,1242,1451,1453,1539,1542,1556,1560,1563,1592,1595,1621,1624,1651,1657,1672,1674,1693,1696,1713,1725,1728,1795,1798,1812,1816,1821,1824,1828,1831,1835,1838,1842,1849,1853,1881,1889],[10,11,5],"h1",{"id":12},"python-list-processing-example",[14,15,16],"p",{},"This beginner-friendly example shows how to process a Python list step by step.",[14,18,19],{},"You will learn how to:",[21,22,23,27,30,33],"ul",{},[24,25,26],"li",{},"loop through a list",[24,28,29],{},"filter items based on a condition",[24,31,32],{},"create a new list with changed values",[24,34,35,36,40,41],{},"summarize list data with functions like ",[37,38,39],"code",{},"sum()"," and ",[37,42,43],{},"len()",[14,45,46],{},"The goal is to practice real list processing in one small script, without getting distracted by too much theory.",[48,49,51],"h2",{"id":50},"quick-example","Quick example",[53,54,59],"pre",{"className":55,"code":56,"language":57,"meta":58,"style":58},"language-python shiki shiki-themes material-theme-lighter github-light github-dark","numbers = [3, 7, 2, 8, 5]\n\n# keep only even numbers\nevens = []\nfor n in numbers:\n    if n % 2 == 0:\n        evens.append(n)\n\n# make a new list with doubled values\ndoubled = []\nfor n in numbers:\n    doubled.append(n * 2)\n\nprint(\"original:\", numbers)\nprint(\"evens:\", evens)\nprint(\"doubled:\", doubled)\nprint(\"sum:\", sum(numbers))\n","python","",[37,60,61,106,113,120,131,150,171,193,198,204,214,227,249,254,279,300,321],{"__ignoreMap":58},[62,63,66,70,74,78,82,85,88,90,93,95,98,100,103],"span",{"class":64,"line":65},"line",1,[62,67,69],{"class":68},"su5hD","numbers ",[62,71,73],{"class":72},"smGrS","=",[62,75,77],{"class":76},"sP7_E"," [",[62,79,81],{"class":80},"srdBf","3",[62,83,84],{"class":76},",",[62,86,87],{"class":80}," 7",[62,89,84],{"class":76},[62,91,92],{"class":80}," 2",[62,94,84],{"class":76},[62,96,97],{"class":80}," 8",[62,99,84],{"class":76},[62,101,102],{"class":80}," 5",[62,104,105],{"class":76},"]\n",[62,107,109],{"class":64,"line":108},2,[62,110,112],{"emptyLinePlaceholder":111},true,"\n",[62,114,116],{"class":64,"line":115},3,[62,117,119],{"class":118},"sutJx","# keep only even numbers\n",[62,121,123,126,128],{"class":64,"line":122},4,[62,124,125],{"class":68},"evens ",[62,127,73],{"class":72},[62,129,130],{"class":76}," []\n",[62,132,134,138,141,144,147],{"class":64,"line":133},5,[62,135,137],{"class":136},"sVHd0","for",[62,139,140],{"class":68}," n ",[62,142,143],{"class":136},"in",[62,145,146],{"class":68}," numbers",[62,148,149],{"class":76},":\n",[62,151,153,156,158,161,163,166,169],{"class":64,"line":152},6,[62,154,155],{"class":136},"    if",[62,157,140],{"class":68},[62,159,160],{"class":72},"%",[62,162,92],{"class":80},[62,164,165],{"class":72}," ==",[62,167,168],{"class":80}," 0",[62,170,149],{"class":76},[62,172,174,177,180,184,187,190],{"class":64,"line":173},7,[62,175,176],{"class":68},"        evens",[62,178,179],{"class":76},".",[62,181,183],{"class":182},"slqww","append",[62,185,186],{"class":76},"(",[62,188,189],{"class":182},"n",[62,191,192],{"class":76},")\n",[62,194,196],{"class":64,"line":195},8,[62,197,112],{"emptyLinePlaceholder":111},[62,199,201],{"class":64,"line":200},9,[62,202,203],{"class":118},"# make a new list with doubled values\n",[62,205,207,210,212],{"class":64,"line":206},10,[62,208,209],{"class":68},"doubled ",[62,211,73],{"class":72},[62,213,130],{"class":76},[62,215,217,219,221,223,225],{"class":64,"line":216},11,[62,218,137],{"class":136},[62,220,140],{"class":68},[62,222,143],{"class":136},[62,224,146],{"class":68},[62,226,149],{"class":76},[62,228,230,233,235,237,239,242,245,247],{"class":64,"line":229},12,[62,231,232],{"class":68},"    doubled",[62,234,179],{"class":76},[62,236,183],{"class":182},[62,238,186],{"class":76},[62,240,241],{"class":182},"n ",[62,243,244],{"class":72},"*",[62,246,92],{"class":80},[62,248,192],{"class":76},[62,250,252],{"class":64,"line":251},13,[62,253,112],{"emptyLinePlaceholder":111},[62,255,257,261,263,267,271,273,275,277],{"class":64,"line":256},14,[62,258,260],{"class":259},"sptTA","print",[62,262,186],{"class":76},[62,264,266],{"class":265},"sjJ54","\"",[62,268,270],{"class":269},"s_sjI","original:",[62,272,266],{"class":265},[62,274,84],{"class":76},[62,276,146],{"class":182},[62,278,192],{"class":76},[62,280,282,284,286,288,291,293,295,298],{"class":64,"line":281},15,[62,283,260],{"class":259},[62,285,186],{"class":76},[62,287,266],{"class":265},[62,289,290],{"class":269},"evens:",[62,292,266],{"class":265},[62,294,84],{"class":76},[62,296,297],{"class":182}," evens",[62,299,192],{"class":76},[62,301,303,305,307,309,312,314,316,319],{"class":64,"line":302},16,[62,304,260],{"class":259},[62,306,186],{"class":76},[62,308,266],{"class":265},[62,310,311],{"class":269},"doubled:",[62,313,266],{"class":265},[62,315,84],{"class":76},[62,317,318],{"class":182}," doubled",[62,320,192],{"class":76},[62,322,324,326,328,330,333,335,337,340,342,345],{"class":64,"line":323},17,[62,325,260],{"class":259},[62,327,186],{"class":76},[62,329,266],{"class":265},[62,331,332],{"class":269},"sum:",[62,334,266],{"class":265},[62,336,84],{"class":76},[62,338,339],{"class":259}," sum",[62,341,186],{"class":76},[62,343,344],{"class":182},"numbers",[62,346,347],{"class":76},"))\n",[14,349,350],{},"Use this as a simple list processing pattern: loop through the list, check each item, and build a new result list when needed.",[48,352,354],{"id":353},"what-this-example-teaches","What this example teaches",[14,356,357],{},"This example focuses on practical list work:",[21,359,360,363,366,369,372],{},[24,361,362],{},"It shows how to work through a list one item at a time.",[24,364,365],{},"It demonstrates filtering values based on a condition.",[24,367,368],{},"It demonstrates creating a new list from existing values.",[24,370,371],{},"It shows simple summary operations like total and count.",[24,373,374],{},"It keeps the focus on practical list processing, not list theory.",[14,376,377,378,179],{},"If you are new to lists, see ",[379,380,382],"a",{"href":381},"\u002Flearn\u002Fpython-lists-explained-beginner-guide","Python lists explained for beginners",[48,384,386],{"id":385},"the-example-input-list","The example input list",[14,388,389],{},"We will use a small list of numbers so the result is easy to follow:",[53,391,393],{"className":55,"code":392,"language":57,"meta":58,"style":58},"numbers = [3, 7, 2, 8, 5]\n",[37,394,395],{"__ignoreMap":58},[62,396,397,399,401,403,405,407,409,411,413,415,417,419,421],{"class":64,"line":65},[62,398,69],{"class":68},[62,400,73],{"class":72},[62,402,77],{"class":76},[62,404,81],{"class":80},[62,406,84],{"class":76},[62,408,87],{"class":80},[62,410,84],{"class":76},[62,412,92],{"class":80},[62,414,84],{"class":76},[62,416,97],{"class":80},[62,418,84],{"class":76},[62,420,102],{"class":80},[62,422,105],{"class":76},[14,424,425],{},"This list contains five items. Python will process them in order:",[427,428,429,433,438,443,448],"ol",{},[24,430,431],{},[37,432,81],{},[24,434,435],{},[37,436,437],{},"7",[24,439,440],{},[37,441,442],{},"2",[24,444,445],{},[37,446,447],{},"8",[24,449,450],{},[37,451,452],{},"5",[14,454,455,456,460,461,463],{},"A useful beginner idea: the original list does ",[457,458,459],"strong",{},"not"," change unless you modify it directly. In this example, we read from ",[37,462,344],{}," and build new lists instead.",[48,465,467],{"id":466},"looping-through-the-list","Looping through the list",[14,469,470,471,473],{},"A ",[37,472,137],{}," loop lets you read one item at a time:",[53,475,477],{"className":55,"code":476,"language":57,"meta":58,"style":58},"numbers = [3, 7, 2, 8, 5]\n\nfor n in numbers:\n    print(n)\n",[37,478,479,507,511,523],{"__ignoreMap":58},[62,480,481,483,485,487,489,491,493,495,497,499,501,503,505],{"class":64,"line":65},[62,482,69],{"class":68},[62,484,73],{"class":72},[62,486,77],{"class":76},[62,488,81],{"class":80},[62,490,84],{"class":76},[62,492,87],{"class":80},[62,494,84],{"class":76},[62,496,92],{"class":80},[62,498,84],{"class":76},[62,500,97],{"class":80},[62,502,84],{"class":76},[62,504,102],{"class":80},[62,506,105],{"class":76},[62,508,509],{"class":64,"line":108},[62,510,112],{"emptyLinePlaceholder":111},[62,512,513,515,517,519,521],{"class":64,"line":115},[62,514,137],{"class":136},[62,516,140],{"class":68},[62,518,143],{"class":136},[62,520,146],{"class":68},[62,522,149],{"class":76},[62,524,525,528,530,532],{"class":64,"line":122},[62,526,527],{"class":259},"    print",[62,529,186],{"class":76},[62,531,189],{"class":182},[62,533,192],{"class":76},[14,535,536],{},"Expected output:",[53,538,540],{"className":55,"code":539,"language":57,"meta":58,"style":58},"3\n7\n2\n8\n5\n",[37,541,542,547,552,557,562],{"__ignoreMap":58},[62,543,544],{"class":64,"line":65},[62,545,546],{"class":80},"3\n",[62,548,549],{"class":64,"line":108},[62,550,551],{"class":80},"7\n",[62,553,554],{"class":64,"line":115},[62,555,556],{"class":80},"2\n",[62,558,559],{"class":64,"line":122},[62,560,561],{"class":80},"8\n",[62,563,564],{"class":64,"line":133},[62,565,566],{"class":80},"5\n",[14,568,569],{},"Here:",[21,571,572,577,582],{},[24,573,574,576],{},[37,575,344],{}," is the list",[24,578,579,581],{},[37,580,189],{}," is the loop variable",[24,583,584,585,587],{},"on each loop, ",[37,586,189],{}," holds one value from the list",[14,589,590,591,179],{},"If you want more practice with this step, read ",[379,592,594],{"href":593},"\u002Fhow-to\u002Fhow-to-loop-through-a-list-in-python","how to loop through a list in Python",[14,596,597,598,601],{},"For beginners, it can help to trace the loop with ",[37,599,600],{},"print()",":",[53,603,605],{"className":55,"code":604,"language":57,"meta":58,"style":58},"numbers = [3, 7, 2, 8, 5]\n\nfor n in numbers:\n    print(\"current number:\", n)\n",[37,606,607,635,639,651],{"__ignoreMap":58},[62,608,609,611,613,615,617,619,621,623,625,627,629,631,633],{"class":64,"line":65},[62,610,69],{"class":68},[62,612,73],{"class":72},[62,614,77],{"class":76},[62,616,81],{"class":80},[62,618,84],{"class":76},[62,620,87],{"class":80},[62,622,84],{"class":76},[62,624,92],{"class":80},[62,626,84],{"class":76},[62,628,97],{"class":80},[62,630,84],{"class":76},[62,632,102],{"class":80},[62,634,105],{"class":76},[62,636,637],{"class":64,"line":108},[62,638,112],{"emptyLinePlaceholder":111},[62,640,641,643,645,647,649],{"class":64,"line":115},[62,642,137],{"class":136},[62,644,140],{"class":68},[62,646,143],{"class":136},[62,648,146],{"class":68},[62,650,149],{"class":76},[62,652,653,655,657,659,662,664,666,669],{"class":64,"line":122},[62,654,527],{"class":259},[62,656,186],{"class":76},[62,658,266],{"class":265},[62,660,661],{"class":269},"current number:",[62,663,266],{"class":265},[62,665,84],{"class":76},[62,667,668],{"class":182}," n",[62,670,192],{"class":76},[48,672,674],{"id":673},"filtering-items","Filtering items",[14,676,677],{},"Filtering means keeping only the items that match a rule.",[14,679,680],{},"In this example, the rule is: keep only even numbers.",[53,682,684],{"className":55,"code":683,"language":57,"meta":58,"style":58},"numbers = [3, 7, 2, 8, 5]\nevens = []\n\nfor n in numbers:\n    if n % 2 == 0:\n        evens.append(n)\n\nprint(evens)\n",[37,685,686,714,722,726,738,754,768,772],{"__ignoreMap":58},[62,687,688,690,692,694,696,698,700,702,704,706,708,710,712],{"class":64,"line":65},[62,689,69],{"class":68},[62,691,73],{"class":72},[62,693,77],{"class":76},[62,695,81],{"class":80},[62,697,84],{"class":76},[62,699,87],{"class":80},[62,701,84],{"class":76},[62,703,92],{"class":80},[62,705,84],{"class":76},[62,707,97],{"class":80},[62,709,84],{"class":76},[62,711,102],{"class":80},[62,713,105],{"class":76},[62,715,716,718,720],{"class":64,"line":108},[62,717,125],{"class":68},[62,719,73],{"class":72},[62,721,130],{"class":76},[62,723,724],{"class":64,"line":115},[62,725,112],{"emptyLinePlaceholder":111},[62,727,728,730,732,734,736],{"class":64,"line":122},[62,729,137],{"class":136},[62,731,140],{"class":68},[62,733,143],{"class":136},[62,735,146],{"class":68},[62,737,149],{"class":76},[62,739,740,742,744,746,748,750,752],{"class":64,"line":133},[62,741,155],{"class":136},[62,743,140],{"class":68},[62,745,160],{"class":72},[62,747,92],{"class":80},[62,749,165],{"class":72},[62,751,168],{"class":80},[62,753,149],{"class":76},[62,755,756,758,760,762,764,766],{"class":64,"line":152},[62,757,176],{"class":68},[62,759,179],{"class":76},[62,761,183],{"class":182},[62,763,186],{"class":76},[62,765,189],{"class":182},[62,767,192],{"class":76},[62,769,770],{"class":64,"line":173},[62,771,112],{"emptyLinePlaceholder":111},[62,773,774,776,778,781],{"class":64,"line":195},[62,775,260],{"class":259},[62,777,186],{"class":76},[62,779,780],{"class":182},"evens",[62,782,192],{"class":76},[14,784,536],{},[53,786,788],{"className":55,"code":787,"language":57,"meta":58,"style":58},"[2, 8]\n",[37,789,790],{"__ignoreMap":58},[62,791,792,795,797,799,801],{"class":64,"line":65},[62,793,794],{"class":76},"[",[62,796,442],{"class":80},[62,798,84],{"class":76},[62,800,97],{"class":80},[62,802,105],{"class":76},[14,804,805],{},"How it works:",[21,807,808,814,817,823],{},[24,809,810,813],{},[37,811,812],{},"evens = []"," creates an empty list",[24,815,816],{},"the loop reads each number",[24,818,819,822],{},[37,820,821],{},"if n % 2 == 0"," checks whether the number is even",[24,824,825,828],{},[37,826,827],{},"evens.append(n)"," adds matching values to the new list",[14,830,831],{},"This is a clear beginner pattern:",[427,833,834,837,840,843],{},[24,835,836],{},"start with an empty list",[24,838,839],{},"loop through the original list",[24,841,842],{},"check a condition",[24,844,845],{},"append matching items",[14,847,848,849,179],{},"For more filtering examples, see ",[379,850,852],{"href":851},"\u002Fhow-to\u002Fhow-to-filter-a-list-in-python","how to filter a list in Python",[48,854,856],{"id":855},"transforming-items","Transforming items",[14,858,859],{},"Transforming means creating a new list where each item is changed in some way.",[14,861,862,863,601],{},"Here, we will multiply each number by ",[37,864,442],{},[53,866,868],{"className":55,"code":867,"language":57,"meta":58,"style":58},"numbers = [3, 7, 2, 8, 5]\ndoubled = []\n\nfor n in numbers:\n    doubled.append(n * 2)\n\nprint(doubled)\n",[37,869,870,898,906,910,922,940,944],{"__ignoreMap":58},[62,871,872,874,876,878,880,882,884,886,888,890,892,894,896],{"class":64,"line":65},[62,873,69],{"class":68},[62,875,73],{"class":72},[62,877,77],{"class":76},[62,879,81],{"class":80},[62,881,84],{"class":76},[62,883,87],{"class":80},[62,885,84],{"class":76},[62,887,92],{"class":80},[62,889,84],{"class":76},[62,891,97],{"class":80},[62,893,84],{"class":76},[62,895,102],{"class":80},[62,897,105],{"class":76},[62,899,900,902,904],{"class":64,"line":108},[62,901,209],{"class":68},[62,903,73],{"class":72},[62,905,130],{"class":76},[62,907,908],{"class":64,"line":115},[62,909,112],{"emptyLinePlaceholder":111},[62,911,912,914,916,918,920],{"class":64,"line":122},[62,913,137],{"class":136},[62,915,140],{"class":68},[62,917,143],{"class":136},[62,919,146],{"class":68},[62,921,149],{"class":76},[62,923,924,926,928,930,932,934,936,938],{"class":64,"line":133},[62,925,232],{"class":68},[62,927,179],{"class":76},[62,929,183],{"class":182},[62,931,186],{"class":76},[62,933,241],{"class":182},[62,935,244],{"class":72},[62,937,92],{"class":80},[62,939,192],{"class":76},[62,941,942],{"class":64,"line":152},[62,943,112],{"emptyLinePlaceholder":111},[62,945,946,948,950,953],{"class":64,"line":173},[62,947,260],{"class":259},[62,949,186],{"class":76},[62,951,952],{"class":182},"doubled",[62,954,192],{"class":76},[14,956,536],{},[53,958,960],{"className":55,"code":959,"language":57,"meta":58,"style":58},"[6, 14, 4, 16, 10]\n",[37,961,962],{"__ignoreMap":58},[62,963,964,966,969,971,974,976,979,981,984,986,989],{"class":64,"line":65},[62,965,794],{"class":76},[62,967,968],{"class":80},"6",[62,970,84],{"class":76},[62,972,973],{"class":80}," 14",[62,975,84],{"class":76},[62,977,978],{"class":80}," 4",[62,980,84],{"class":76},[62,982,983],{"class":80}," 16",[62,985,84],{"class":76},[62,987,988],{"class":80}," 10",[62,990,105],{"class":76},[14,992,993,994,179],{},"This does not change the original list. It creates a new list called ",[37,995,952],{},[14,997,998],{},"For beginners, building a new list is often easier to understand than changing the original list in place. It also makes debugging easier because you can compare the old list and the new list.",[48,1000,1002],{"id":1001},"summarizing-list-data","Summarizing list data",[14,1004,1005],{},"After processing a list, you often want a summary.",[14,1007,1008],{},"For numeric lists, common summary tools are:",[21,1010,1011,1016,1021,1027],{},[24,1012,1013,1015],{},[37,1014,39],{}," for the total",[24,1017,1018,1020],{},[37,1019,43],{}," for the number of items",[24,1022,1023,1026],{},[37,1024,1025],{},"min()"," for the smallest value",[24,1028,1029,1032],{},[37,1030,1031],{},"max()"," for the largest value",[14,1034,1035],{},"Example:",[53,1037,1039],{"className":55,"code":1038,"language":57,"meta":58,"style":58},"numbers = [3, 7, 2, 8, 5]\n\nprint(\"sum:\", sum(numbers))\nprint(\"count:\", len(numbers))\nprint(\"smallest:\", min(numbers))\nprint(\"largest:\", max(numbers))\n",[37,1040,1041,1069,1073,1095,1119,1143],{"__ignoreMap":58},[62,1042,1043,1045,1047,1049,1051,1053,1055,1057,1059,1061,1063,1065,1067],{"class":64,"line":65},[62,1044,69],{"class":68},[62,1046,73],{"class":72},[62,1048,77],{"class":76},[62,1050,81],{"class":80},[62,1052,84],{"class":76},[62,1054,87],{"class":80},[62,1056,84],{"class":76},[62,1058,92],{"class":80},[62,1060,84],{"class":76},[62,1062,97],{"class":80},[62,1064,84],{"class":76},[62,1066,102],{"class":80},[62,1068,105],{"class":76},[62,1070,1071],{"class":64,"line":108},[62,1072,112],{"emptyLinePlaceholder":111},[62,1074,1075,1077,1079,1081,1083,1085,1087,1089,1091,1093],{"class":64,"line":115},[62,1076,260],{"class":259},[62,1078,186],{"class":76},[62,1080,266],{"class":265},[62,1082,332],{"class":269},[62,1084,266],{"class":265},[62,1086,84],{"class":76},[62,1088,339],{"class":259},[62,1090,186],{"class":76},[62,1092,344],{"class":182},[62,1094,347],{"class":76},[62,1096,1097,1099,1101,1103,1106,1108,1110,1113,1115,1117],{"class":64,"line":122},[62,1098,260],{"class":259},[62,1100,186],{"class":76},[62,1102,266],{"class":265},[62,1104,1105],{"class":269},"count:",[62,1107,266],{"class":265},[62,1109,84],{"class":76},[62,1111,1112],{"class":259}," len",[62,1114,186],{"class":76},[62,1116,344],{"class":182},[62,1118,347],{"class":76},[62,1120,1121,1123,1125,1127,1130,1132,1134,1137,1139,1141],{"class":64,"line":133},[62,1122,260],{"class":259},[62,1124,186],{"class":76},[62,1126,266],{"class":265},[62,1128,1129],{"class":269},"smallest:",[62,1131,266],{"class":265},[62,1133,84],{"class":76},[62,1135,1136],{"class":259}," min",[62,1138,186],{"class":76},[62,1140,344],{"class":182},[62,1142,347],{"class":76},[62,1144,1145,1147,1149,1151,1154,1156,1158,1161,1163,1165],{"class":64,"line":152},[62,1146,260],{"class":259},[62,1148,186],{"class":76},[62,1150,266],{"class":265},[62,1152,1153],{"class":269},"largest:",[62,1155,266],{"class":265},[62,1157,84],{"class":76},[62,1159,1160],{"class":259}," max",[62,1162,186],{"class":76},[62,1164,344],{"class":182},[62,1166,347],{"class":76},[14,1168,536],{},[53,1170,1172],{"className":55,"code":1171,"language":57,"meta":58,"style":58},"sum: 25\ncount: 5\nsmallest: 2\nlargest: 8\n",[37,1173,1174,1184,1194,1204],{"__ignoreMap":58},[62,1175,1176,1179,1181],{"class":64,"line":65},[62,1177,1178],{"class":259},"sum",[62,1180,601],{"class":76},[62,1182,1183],{"class":80}," 25\n",[62,1185,1186,1189,1191],{"class":64,"line":108},[62,1187,1188],{"class":68},"count",[62,1190,601],{"class":76},[62,1192,1193],{"class":80}," 5\n",[62,1195,1196,1199,1201],{"class":64,"line":115},[62,1197,1198],{"class":68},"smallest",[62,1200,601],{"class":76},[62,1202,1203],{"class":80}," 2\n",[62,1205,1206,1209,1211],{"class":64,"line":122},[62,1207,1208],{"class":68},"largest",[62,1210,601],{"class":76},[62,1212,1213],{"class":80}," 8\n",[14,1215,1216],{},"If you want to understand these functions better, see:",[21,1218,1219,1228],{},[24,1220,1221],{},[379,1222,1224,1225,1227],{"href":1223},"\u002Freference\u002Fpython-sum-function-explained","Python ",[37,1226,39],{}," function explained",[24,1229,1230],{},[379,1231,1224,1233,1227],{"href":1232},"\u002Freference\u002Fpython-len-function-explained",[37,1234,43],{},[48,1236,1238],{"id":1237},"expected-output","Expected output",[14,1240,1241],{},"Here is the full example again:",[53,1243,1245],{"className":55,"code":1244,"language":57,"meta":58,"style":58},"numbers = [3, 7, 2, 8, 5]\n\nevens = []\nfor n in numbers:\n    if n % 2 == 0:\n        evens.append(n)\n\ndoubled = []\nfor n in numbers:\n    doubled.append(n * 2)\n\nprint(\"original:\", numbers)\nprint(\"evens:\", evens)\nprint(\"doubled:\", doubled)\nprint(\"sum:\", sum(numbers))\n",[37,1246,1247,1275,1279,1287,1299,1315,1329,1333,1341,1353,1371,1375,1393,1411,1429],{"__ignoreMap":58},[62,1248,1249,1251,1253,1255,1257,1259,1261,1263,1265,1267,1269,1271,1273],{"class":64,"line":65},[62,1250,69],{"class":68},[62,1252,73],{"class":72},[62,1254,77],{"class":76},[62,1256,81],{"class":80},[62,1258,84],{"class":76},[62,1260,87],{"class":80},[62,1262,84],{"class":76},[62,1264,92],{"class":80},[62,1266,84],{"class":76},[62,1268,97],{"class":80},[62,1270,84],{"class":76},[62,1272,102],{"class":80},[62,1274,105],{"class":76},[62,1276,1277],{"class":64,"line":108},[62,1278,112],{"emptyLinePlaceholder":111},[62,1280,1281,1283,1285],{"class":64,"line":115},[62,1282,125],{"class":68},[62,1284,73],{"class":72},[62,1286,130],{"class":76},[62,1288,1289,1291,1293,1295,1297],{"class":64,"line":122},[62,1290,137],{"class":136},[62,1292,140],{"class":68},[62,1294,143],{"class":136},[62,1296,146],{"class":68},[62,1298,149],{"class":76},[62,1300,1301,1303,1305,1307,1309,1311,1313],{"class":64,"line":133},[62,1302,155],{"class":136},[62,1304,140],{"class":68},[62,1306,160],{"class":72},[62,1308,92],{"class":80},[62,1310,165],{"class":72},[62,1312,168],{"class":80},[62,1314,149],{"class":76},[62,1316,1317,1319,1321,1323,1325,1327],{"class":64,"line":152},[62,1318,176],{"class":68},[62,1320,179],{"class":76},[62,1322,183],{"class":182},[62,1324,186],{"class":76},[62,1326,189],{"class":182},[62,1328,192],{"class":76},[62,1330,1331],{"class":64,"line":173},[62,1332,112],{"emptyLinePlaceholder":111},[62,1334,1335,1337,1339],{"class":64,"line":195},[62,1336,209],{"class":68},[62,1338,73],{"class":72},[62,1340,130],{"class":76},[62,1342,1343,1345,1347,1349,1351],{"class":64,"line":200},[62,1344,137],{"class":136},[62,1346,140],{"class":68},[62,1348,143],{"class":136},[62,1350,146],{"class":68},[62,1352,149],{"class":76},[62,1354,1355,1357,1359,1361,1363,1365,1367,1369],{"class":64,"line":206},[62,1356,232],{"class":68},[62,1358,179],{"class":76},[62,1360,183],{"class":182},[62,1362,186],{"class":76},[62,1364,241],{"class":182},[62,1366,244],{"class":72},[62,1368,92],{"class":80},[62,1370,192],{"class":76},[62,1372,1373],{"class":64,"line":216},[62,1374,112],{"emptyLinePlaceholder":111},[62,1376,1377,1379,1381,1383,1385,1387,1389,1391],{"class":64,"line":229},[62,1378,260],{"class":259},[62,1380,186],{"class":76},[62,1382,266],{"class":265},[62,1384,270],{"class":269},[62,1386,266],{"class":265},[62,1388,84],{"class":76},[62,1390,146],{"class":182},[62,1392,192],{"class":76},[62,1394,1395,1397,1399,1401,1403,1405,1407,1409],{"class":64,"line":251},[62,1396,260],{"class":259},[62,1398,186],{"class":76},[62,1400,266],{"class":265},[62,1402,290],{"class":269},[62,1404,266],{"class":265},[62,1406,84],{"class":76},[62,1408,297],{"class":182},[62,1410,192],{"class":76},[62,1412,1413,1415,1417,1419,1421,1423,1425,1427],{"class":64,"line":256},[62,1414,260],{"class":259},[62,1416,186],{"class":76},[62,1418,266],{"class":265},[62,1420,311],{"class":269},[62,1422,266],{"class":265},[62,1424,84],{"class":76},[62,1426,318],{"class":182},[62,1428,192],{"class":76},[62,1430,1431,1433,1435,1437,1439,1441,1443,1445,1447,1449],{"class":64,"line":281},[62,1432,260],{"class":259},[62,1434,186],{"class":76},[62,1436,266],{"class":265},[62,1438,332],{"class":269},[62,1440,266],{"class":265},[62,1442,84],{"class":76},[62,1444,339],{"class":259},[62,1446,186],{"class":76},[62,1448,344],{"class":182},[62,1450,347],{"class":76},[14,1452,536],{},[53,1454,1456],{"className":55,"code":1455,"language":57,"meta":58,"style":58},"original: [3, 7, 2, 8, 5]\nevens: [2, 8]\ndoubled: [6, 14, 4, 16, 10]\nsum: 25\n",[37,1457,1458,1487,1503,1531],{"__ignoreMap":58},[62,1459,1460,1463,1465,1467,1469,1471,1473,1475,1477,1479,1481,1483,1485],{"class":64,"line":65},[62,1461,1462],{"class":68},"original",[62,1464,601],{"class":76},[62,1466,77],{"class":76},[62,1468,81],{"class":80},[62,1470,84],{"class":76},[62,1472,87],{"class":80},[62,1474,84],{"class":76},[62,1476,92],{"class":80},[62,1478,84],{"class":76},[62,1480,97],{"class":80},[62,1482,84],{"class":76},[62,1484,102],{"class":80},[62,1486,105],{"class":76},[62,1488,1489,1491,1493,1495,1497,1499,1501],{"class":64,"line":108},[62,1490,780],{"class":68},[62,1492,601],{"class":76},[62,1494,77],{"class":76},[62,1496,442],{"class":80},[62,1498,84],{"class":76},[62,1500,97],{"class":80},[62,1502,105],{"class":76},[62,1504,1505,1507,1509,1511,1513,1515,1517,1519,1521,1523,1525,1527,1529],{"class":64,"line":115},[62,1506,952],{"class":68},[62,1508,601],{"class":76},[62,1510,77],{"class":76},[62,1512,968],{"class":80},[62,1514,84],{"class":76},[62,1516,973],{"class":80},[62,1518,84],{"class":76},[62,1520,978],{"class":80},[62,1522,84],{"class":76},[62,1524,983],{"class":80},[62,1526,84],{"class":76},[62,1528,988],{"class":80},[62,1530,105],{"class":76},[62,1532,1533,1535,1537],{"class":64,"line":122},[62,1534,1178],{"class":259},[62,1536,601],{"class":76},[62,1538,1183],{"class":80},[14,1540,1541],{},"This output shows:",[21,1543,1544,1547,1550,1553],{},[24,1545,1546],{},"the original list",[24,1548,1549],{},"the filtered list of even numbers",[24,1551,1552],{},"the transformed list with doubled values",[24,1554,1555],{},"the total of the original numbers",[48,1557,1559],{"id":1558},"beginner-mistakes-to-watch-for","Beginner mistakes to watch for",[14,1561,1562],{},"These are common problems when processing lists:",[21,1564,1565,1577,1583,1586],{},[24,1566,1567,1568,1570,1571,1573,1574],{},"Forgetting the colon ",[37,1569,601],{}," after ",[37,1572,137],{}," or ",[37,1575,1576],{},"if",[24,1578,1579,1580,1582],{},"Using ",[37,1581,183],{}," without parentheses",[24,1584,1585],{},"Changing the original list by accident",[24,1587,1588,1589,1591],{},"Trying to use ",[37,1590,39],{}," on a list that contains non-numbers",[14,1593,1594],{},"Example of a missing colon:",[53,1596,1598],{"className":55,"code":1597,"language":57,"meta":58,"style":58},"for n in numbers\n    print(n)\n",[37,1599,1600,1611],{"__ignoreMap":58},[62,1601,1602,1604,1606,1608],{"class":64,"line":65},[62,1603,137],{"class":136},[62,1605,140],{"class":68},[62,1607,143],{"class":136},[62,1609,1610],{"class":68}," numbers\n",[62,1612,1613,1615,1617,1619],{"class":64,"line":108},[62,1614,527],{"class":259},[62,1616,186],{"class":76},[62,1618,189],{"class":182},[62,1620,192],{"class":76},[14,1622,1623],{},"Correct version:",[53,1625,1627],{"className":55,"code":1626,"language":57,"meta":58,"style":58},"for n in numbers:\n    print(n)\n",[37,1628,1629,1641],{"__ignoreMap":58},[62,1630,1631,1633,1635,1637,1639],{"class":64,"line":65},[62,1632,137],{"class":136},[62,1634,140],{"class":68},[62,1636,143],{"class":136},[62,1638,146],{"class":68},[62,1640,149],{"class":76},[62,1642,1643,1645,1647,1649],{"class":64,"line":108},[62,1644,527],{"class":259},[62,1646,186],{"class":76},[62,1648,189],{"class":182},[62,1650,192],{"class":76},[14,1652,1653,1654,1656],{},"Example of incorrect ",[37,1655,183],{}," use:",[53,1658,1660],{"className":55,"code":1659,"language":57,"meta":58,"style":58},"evens.append\n",[37,1661,1662],{"__ignoreMap":58},[62,1663,1664,1666,1668],{"class":64,"line":65},[62,1665,780],{"class":68},[62,1667,179],{"class":76},[62,1669,1671],{"class":1670},"skxfh","append\n",[14,1673,1623],{},[53,1675,1677],{"className":55,"code":1676,"language":57,"meta":58,"style":58},"evens.append(n)\n",[37,1678,1679],{"__ignoreMap":58},[62,1680,1681,1683,1685,1687,1689,1691],{"class":64,"line":65},[62,1682,780],{"class":68},[62,1684,179],{"class":76},[62,1686,183],{"class":182},[62,1688,186],{"class":76},[62,1690,189],{"class":182},[62,1692,192],{"class":76},[14,1694,1695],{},"Other common causes of errors include:",[21,1697,1698,1701,1704,1707,1710],{},[24,1699,1700],{},"confusing filtering with modifying the original list",[24,1702,1703],{},"using the wrong indentation inside the loop",[24,1705,1706],{},"appending the wrong value to the result list",[24,1708,1709],{},"trying to use string methods on list items that are numbers",[24,1711,1712],{},"mixing strings and integers in summary operations",[14,1714,1715,1716,1720,1721,179],{},"If you get an index problem while testing lists, see ",[379,1717,1719],{"href":1718},"\u002Ferrors\u002Findexerror-list-index-out-of-range-fix-explained","IndexError: list index out of range",". If you get a type-related loop problem, see ",[379,1722,1724],{"href":1723},"\u002Ferrors\u002Ftypeerror-int-object-is-not-iterable-fix","TypeError: int object is not iterable",[14,1726,1727],{},"Useful debug prints:",[53,1729,1731],{"className":55,"code":1730,"language":57,"meta":58,"style":58},"print(numbers)\nprint(n)\nprint(evens)\nprint(doubled)\nprint(type(numbers[0]))\n",[37,1732,1733,1743,1753,1763,1773],{"__ignoreMap":58},[62,1734,1735,1737,1739,1741],{"class":64,"line":65},[62,1736,260],{"class":259},[62,1738,186],{"class":76},[62,1740,344],{"class":182},[62,1742,192],{"class":76},[62,1744,1745,1747,1749,1751],{"class":64,"line":108},[62,1746,260],{"class":259},[62,1748,186],{"class":76},[62,1750,189],{"class":182},[62,1752,192],{"class":76},[62,1754,1755,1757,1759,1761],{"class":64,"line":115},[62,1756,260],{"class":259},[62,1758,186],{"class":76},[62,1760,780],{"class":182},[62,1762,192],{"class":76},[62,1764,1765,1767,1769,1771],{"class":64,"line":122},[62,1766,260],{"class":259},[62,1768,186],{"class":76},[62,1770,952],{"class":182},[62,1772,192],{"class":76},[62,1774,1775,1777,1779,1783,1785,1787,1789,1792],{"class":64,"line":133},[62,1776,260],{"class":259},[62,1778,186],{"class":76},[62,1780,1782],{"class":1781},"sZMiF","type",[62,1784,186],{"class":76},[62,1786,344],{"class":182},[62,1788,794],{"class":76},[62,1790,1791],{"class":80},"0",[62,1793,1794],{"class":76},"]))\n",[14,1796,1797],{},"These can help you check:",[21,1799,1800,1803,1806,1809],{},[24,1801,1802],{},"what is inside the list",[24,1804,1805],{},"what the current loop value is",[24,1807,1808],{},"what has been added to your new lists",[24,1810,1811],{},"what data type you are working with",[48,1813,1815],{"id":1814},"faq","FAQ",[1817,1818,1820],"h3",{"id":1819},"what-does-list-processing-mean-in-python","What does list processing mean in Python?",[14,1822,1823],{},"It means reading items from a list and doing something with them, such as filtering, changing, or summarizing them.",[1817,1825,1827],{"id":1826},"should-i-change-the-original-list-or-create-a-new-one","Should I change the original list or create a new one?",[14,1829,1830],{},"For beginners, creating a new list is often easier to understand and safer.",[1817,1832,1834],{"id":1833},"can-i-do-this-with-strings-instead-of-numbers","Can I do this with strings instead of numbers?",[14,1836,1837],{},"Yes. You can loop through a list of strings and filter or change each item in the same way.",[1817,1839,1841],{"id":1840},"is-this-the-same-as-a-list-comprehension","Is this the same as a list comprehension?",[14,1843,1844,1845,179],{},"Not exactly. A list comprehension is a shorter way to build a list, but the loop-based version is usually clearer when you are learning. After you understand this pattern, you can move on to ",[379,1846,1848],{"href":1847},"\u002Fhow-to\u002Fhow-to-use-list-comprehensions-in-python","how to use list comprehensions in Python",[48,1850,1852],{"id":1851},"see-also","See also",[21,1854,1855,1859,1864,1869,1875],{},[24,1856,1857],{},[379,1858,382],{"href":381},[24,1860,1861],{},[379,1862,1863],{"href":593},"How to loop through a list in Python",[24,1865,1866],{},[379,1867,1868],{"href":851},"How to filter a list in Python",[24,1870,1871],{},[379,1872,1224,1873,1227],{"href":1223},[37,1874,39],{},[24,1876,1877],{},[379,1878,1224,1879,1227],{"href":1232},[37,1880,43],{},[14,1882,1883,1884,40,1886,1888],{},"Try the same pattern with a list of names or prices next. 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