{ "componentChunkName": "component---src-templates-course-content-template-js", "path": "/osa-3/1-loopar-med-villkor", "result": {"data":{"page":{"htmlAst":{"type":"element","tagName":"div","properties":{},"children":[{"type":"element","tagName":"text-box","properties":{"variant":"learningObjectives","name":"Lärandemål"},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Efter den här delen"}]},{"type":"element","tagName":"ul","properties":{},"children":[{"type":"text","value":"\n"},{"type":"element","tagName":"li","properties":{},"children":[{"type":"text","value":"kan du skapa en loop med ett villkor"}]},{"type":"text","value":"\n"},{"type":"element","tagName":"li","properties":{},"children":[{"type":"text","value":"vet du vad vilka roller initiering, villkoret och uppdatering av variabler har i en loop"}]},{"type":"text","value":"\n"},{"type":"element","tagName":"li","properties":{},"children":[{"type":"text","value":"kan du skapa loopar med olika typer av villkor."}]},{"type":"text","value":"\n"}]}]},{"type":"comment","value":"vastaava teksti löytyy osioista 3-1, 5-1 ja 6-1, tsekkaa kaikki jos muokkaat tätä"},{"type":"element","tagName":"text-box","properties":{"variant":"hint","name":"Om uppgifterna i den här kursen"},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Att bli en skicklig programmerare kräver mycket övning. Man måste utveckla en problemlösningsförmåga och ha en förmåga att intuition komma fram till korrekta lösningar. Därför finns det massor av övningar av olika typer i den här kursen. Vissa övningar är enklare och baserar sig mera eller mindre direkt på materialet medan andra uppgifter är svårare och kräver tillämpande av kunskaper som man lärt sig under kursen."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"En del uppgifter kan kännas svåra, men det är inte något att oroa sig över. Ingen av uppgifterna är obligatorisk och du behöver bara 25 % av poängen från varje modul för att klara den här kursen. Du kan läsa mera på kursens bedömningssida."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Uppgifterna är inte i svårighetsordning. Varje del introducerar vanligtvis några nya saker inom programmering och i samband finns relaterade uppgifter – både enklare och svårare. Om du stöter på en uppgift som känns oöverkomlig ska du fortsätta till nästa uppgift. Du kan alltid senare återkomma till tidigare uppgifter."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"En uppgift som känns för svår just nu kommer sannolikt att vara ganska enkel om en månad."}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"I den förra delen bekantade vi oss med "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"while True"}]},{"type":"text","value":" -loopen som ett sätt för att upprepa delar av kod. Så som loopen är uppbyggd är villkoret alltid "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"True"}]},{"type":"text","value":", alltså sant. Vi måste då avsluta loopen manuellt med "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"break"}]},{"type":"text","value":" i något skede för att undvika en oändlig loop. Exempelvis:"}]},{"type":"element","tagName":"div","properties":{"className":["gatsby-highlight"],"dataLanguage":"python"},"children":[{"type":"element","tagName":"pre","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"code","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"span","properties":{"className":["token","comment"]},"children":[{"type":"text","value":"# skriv ut tal tills värdet på variabeln a är 5"}]},{"type":"text","value":"\na "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"1"}]},{"type":"text","value":"\n"},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"while"}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","boolean"]},"children":[{"type":"text","value":"True"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":":"}]},{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"print"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"("}]},{"type":"text","value":"a"},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":")"}]},{"type":"text","value":"\n a "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"+="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"1"}]},{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"if"}]},{"type":"text","value":" a "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"=="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"5"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":":"}]},{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"break"}]}]}]}]},{"type":"element","tagName":"sample-output","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"1\n2\n3\n4"}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Men förstås behöver villkoret inte alltid vara True, utan det kan vara vilket som helst Boolean-uttryck. while-satsens struktur ser ut så här:"}]},{"type":"element","tagName":"div","properties":{"className":["gatsby-highlight"],"dataLanguage":"python"},"children":[{"type":"element","tagName":"pre","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"code","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"while"}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"<"}]},{"type":"text","value":"villkor"},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":">"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":":"}]},{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"<"}]},{"type":"text","value":"block"},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":">"}]}]}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Idén är att koden körs om och om igen så länge som villkoret är sant. Villkorets värde kollas inför varje ny iteratione och när det är "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"False"}]},{"type":"text","value":" kommer programmet inte att fortsätta köra loopen, utan i stället fortsätta med koden som kommer efter while-blocket."}]},{"type":"element","tagName":"span","properties":{"className":["gatsby-resp-image-wrapper"],"style":"position: relative; display: block; margin-left: auto; margin-right: auto; max-width: 417px; margin-bottom: 1rem;"},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"a","properties":{"className":["gatsby-resp-image-link"],"href":"/static/f04729f75a5887689930a906bc04ff72/f27fb/3_1_1.png","style":"display: block","target":"_blank","rel":["noopener"]},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["gatsby-resp-image-background-image"],"style":"padding-bottom: 103.04347826086956%; position: relative; bottom: 0; left: 0; background-image: url('data:image/png;base64,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'); background-size: cover; display: block;"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"picture","properties":{},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"source","properties":{"srcSet":["/static/f04729f75a5887689930a906bc04ff72/a0b58/3_1_1.webp 230w","/static/f04729f75a5887689930a906bc04ff72/b6b2f/3_1_1.webp 417w"],"sizes":"(max-width: 417px) 100vw, 417px","type":"image/webp"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"source","properties":{"srcSet":["/static/f04729f75a5887689930a906bc04ff72/81c8e/3_1_1.png 230w","/static/f04729f75a5887689930a906bc04ff72/f27fb/3_1_1.png 417w"],"sizes":"(max-width: 417px) 100vw, 417px","type":"image/png"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"img","properties":{"className":["gatsby-resp-image-image"],"src":"/static/f04729f75a5887689930a906bc04ff72/f27fb/3_1_1.png","alt":"3 1 1","title":"3 1 1","loading":"lazy","decoding":"async","style":"width:100%;height:100%;margin:0;vertical-align:middle;position:absolute;top:0;left:0;"},"children":[]},{"type":"text","value":"\n "}]},{"type":"text","value":"\n "}]},{"type":"text","value":"\n "}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"I den följande loopen har vi villkoret "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"tal < 10"}]},{"type":"text","value":". Blocket inom loopen kommer bara att köras då variabeln tal är mindre än tio."}]},{"type":"element","tagName":"div","properties":{"className":["gatsby-highlight"],"dataLanguage":"python"},"children":[{"type":"element","tagName":"pre","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"code","properties":{"className":["language-python"]},"children":[{"type":"text","value":"tal "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","builtin"]},"children":[{"type":"text","value":"int"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"("}]},{"type":"element","tagName":"span","properties":{"className":["token","builtin"]},"children":[{"type":"text","value":"input"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"("}]},{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":"\"Ge ett tal: \""}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":")"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":")"}]},{"type":"text","value":"\n\n"},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"while"}]},{"type":"text","value":" tal "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"<"}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"10"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":":"}]},{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"print"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"("}]},{"type":"text","value":"tal"},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":")"}]},{"type":"text","value":"\n tal "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"+="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"1"}]},{"type":"text","value":"\n\n"},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"print"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"("}]},{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":"\"Programmet är klart.\""}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":")"}]}]}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Utskriften skulle kunna se ut så här:"}]},{"type":"element","tagName":"sample-output","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Ge ett tal: "},{"type":"element","tagName":"strong","properties":{},"children":[{"type":"text","value":"4"}]},{"type":"text","value":"\n4\n5\n6\n7\n8\n9\nProgrammet är klart."}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Med den här strukturen kommer villkoret att kollas före blocket inom loopen körs. Det är möjligt att här blocket inte kommer att köras en enda gång. Till exempel så här:"}]},{"type":"element","tagName":"sample-output","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Ge ett tal: "},{"type":"element","tagName":"strong","properties":{},"children":[{"type":"text","value":"12"}]},{"type":"text","value":"\nProgrammet är klart."}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Tolv är inte mindre än tio, så programmet skriver inte ut något tal alls."}]},{"type":"element","tagName":"h2","properties":{"id":"initialisering-villkor-och-uppdatering","style":"position:relative;"},"children":[{"type":"text","value":"Initialisering, villkor och uppdatering"},{"type":"element","tagName":"a","properties":{"href":"#initialisering-villkor-och-uppdatering","ariaLabel":"initialisering villkor och uppdatering permalink","className":["anchor","after"]},"children":[{"type":"element","tagName":"svg","properties":{"ariaHidden":"true","focusable":"false","height":"16","version":"1.1","viewBox":"0 0 16 16","width":"16"},"children":[{"type":"element","tagName":"path","properties":{"fillRule":"evenodd","d":"M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"},"children":[]}]}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"När vi jobbar med while-loopar behöver vi komma ihåg tre steg: initialisering, ett villkor och uppdatering av variabler."}]},{"type":"element","tagName":"ul","properties":{},"children":[{"type":"text","value":"\n"},{"type":"element","tagName":"li","properties":{},"children":[{"type":"text","value":"Initialisering innebär att vi tilldelar startvärden till de variabler som används i loopens villkor. Det här behöver man göra före loopen i koden."}]},{"type":"text","value":"\n"},{"type":"element","tagName":"li","properties":{},"children":[{"type":"text","value":"Villkoret bestämmer hur länge loopen körs och anges direkt efter while."}]},{"type":"text","value":"\n"},{"type":"element","tagName":"li","properties":{},"children":[{"type":"text","value":"För att undvika oändliga loopar, måste vi se till att värdet på någon variabel i villkoret uppdateras, så att loopen steg för steg närmar sig sitt slut."}]},{"type":"text","value":"\n"}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Här presenterar vi stegen i ett exempel:"}]},{"type":"element","tagName":"span","properties":{"className":["gatsby-resp-image-wrapper"],"style":"position: relative; display: block; margin-left: auto; margin-right: auto; max-width: 701px; margin-bottom: 1rem;"},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"a","properties":{"className":["gatsby-resp-image-link"],"href":"/static/a9e9068a5a4abf5977e87c6b64318418/49217/3_1_2.png","style":"display: block","target":"_blank","rel":["noopener"]},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["gatsby-resp-image-background-image"],"style":"padding-bottom: 40.43478260869565%; position: relative; bottom: 0; left: 0; background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAICAYAAAD5nd/tAAAACXBIWXMAAAsTAAALEwEAmpwYAAABaUlEQVQoz1WRy3KbMABF2cfGBiT0RggBxnEn7Uw3/f8fOx3JidMuzkIj6c59NDruTOsPTDxw6wdue2DXD0I+CNuOzzdcynTKMSjHRTpaYWmF4aoCvZnpdKQ3iV5HmjEk3LLTl0ufGJcVMd9xc2TaZuwccWlCaI80nsvouUhbRTs1MRQhk5B+Q9hMY+xGCHd8fhC3n2iXcWFB+judzgx2o1OJwa1If2OwS/1c3BW3xd11DJw6yalXNM5mvFkwU8bEFaE8xk50KnCtbhyX8Rn1X74cCpdr7FJBoTkNilYHxHRjDBmbDoTPdHqujwtjuNWY50FxHvSLUz/y1gneOsm5f941ba9Q887x+w/LfrC9/2J/PJA6cC1OpKeVtgp+83TY67nG/+qvCl5UQPpEXFd0iJg411VNiCgfkG56jfDi81y6K3GLcFm4Cop5Z1x2bHSkY2F9z3VVFQLTllC+dKb/i/qNqkOcPykd/gWh5s8zQ4VpAgAAAABJRU5ErkJggg=='); background-size: cover; display: block;"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"picture","properties":{},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"source","properties":{"srcSet":["/static/a9e9068a5a4abf5977e87c6b64318418/a0b58/3_1_2.webp 230w","/static/a9e9068a5a4abf5977e87c6b64318418/bc10c/3_1_2.webp 460w","/static/a9e9068a5a4abf5977e87c6b64318418/e2a71/3_1_2.webp 701w"],"sizes":"(max-width: 701px) 100vw, 701px","type":"image/webp"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"source","properties":{"srcSet":["/static/a9e9068a5a4abf5977e87c6b64318418/81c8e/3_1_2.png 230w","/static/a9e9068a5a4abf5977e87c6b64318418/08a84/3_1_2.png 460w","/static/a9e9068a5a4abf5977e87c6b64318418/49217/3_1_2.png 701w"],"sizes":"(max-width: 701px) 100vw, 701px","type":"image/png"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"img","properties":{"className":["gatsby-resp-image-image"],"src":"/static/a9e9068a5a4abf5977e87c6b64318418/49217/3_1_2.png","alt":"3 1 2","title":"3 1 2","loading":"lazy","decoding":"async","style":"width:100%;height:100%;margin:0;vertical-align:middle;position:absolute;top:0;left:0;"},"children":[]},{"type":"text","value":"\n "}]},{"type":"text","value":"\n "}]},{"type":"text","value":"\n "}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Om någon av de här tre komponenterna fattas kommer loopen antagligen inte att fungera korrekt. 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Om testet berättar att något är fel med till exempel värdet 42 så kan värdet tillfälligt hårdkodas i programmet medan du letar efter buggen:"}]},{"type":"element","tagName":"div","properties":{"className":["gatsby-highlight"],"dataLanguage":"python"},"children":[{"type":"element","tagName":"pre","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"code","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"span","properties":{"className":["token","comment"]},"children":[{"type":"text","value":"# testet meddelade att koden inte fungerade korrekt då indatat är 42"}]},{"type":"text","value":"\nstanna "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"42"}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","comment"]},"children":[{"type":"text","value":"# int(input(\"Fram till talet\"))"}]},{"type":"text","value":"\ntal "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"1"}]},{"type":"text","value":"\n"},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"while"}]},{"type":"text","value":" tal "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"=="}]},{"type":"text","value":" stanna"},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":":"}]},{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["token","comment"]},"children":[{"type":"text","value":"# kod"}]}]}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Debuggning med hjälp av "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"print"}]},{"type":"text","value":"-satsen nämndes några gånger under den förra kursmodulen. De program som du skapar kommer att bli mer invecklade i och med att vi kommer längre i kursen. Då kommer mängden debuggning som du behöver göra också antagligen att öka i samma proportion. Vanliga orsaker till buggar finns ofta i de villkor som ska avsluta loopar – de fungerar eventuellt korrekt för vissa värden, medan andra värden orsakar problem. Det är inte alltid heller lätt att lägga märke till de här felen."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Därför är det nu dags att använda dig av "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"print"}]},{"type":"text","value":"-satser för att debugga – om du inte redan har gjort det. Du hittar instruktioner i den första och fjärde delen av modul 2."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Vid sidan om "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"print"}]},{"type":"text","value":"-satser finns även andra verktyg som kan använda för debuggning. Ett av dem är "},{"type":"element","tagName":"a","properties":{"href":"https://pythontutor.com/visualize.html","target":"_blank","rel":["noopener","noreferrer"]},"children":[{"type":"text","value":"visualiseringsverktyget"}]},{"type":"text","value":" på "},{"type":"element","tagName":"a","properties":{"href":"https://pythontutor.com/","target":"_blank","rel":["noopener","noreferrer"]},"children":[{"type":"text","value":"Python Tutor"}]},{"type":"text","value":" -webbsidan. Verktyget låter dig köra din kod rad för rad och visar också de värden som är lagrade i variabler vid varje steg."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Koden – med några problem – från den förra delen visualiseras med Python Tutor i följande bild:"}]},{"type":"element","tagName":"span","properties":{"className":["gatsby-resp-image-wrapper"],"style":"position: relative; display: block; margin-left: auto; margin-right: auto; max-width: 920px; margin-bottom: 1rem;"},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"a","properties":{"className":["gatsby-resp-image-link"],"href":"/static/d0cc22babf6824495497d96f07b56664/95fa1/3_1_0.png","style":"display: block","target":"_blank","rel":["noopener"]},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"span","properties":{"className":["gatsby-resp-image-background-image"],"style":"padding-bottom: 69.1304347826087%; position: relative; bottom: 0; left: 0; background-image: url('data:image/png;base64,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'); background-size: cover; display: block;"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"picture","properties":{},"children":[{"type":"text","value":"\n "},{"type":"element","tagName":"source","properties":{"srcSet":["/static/d0cc22babf6824495497d96f07b56664/a0b58/3_1_0.webp 230w","/static/d0cc22babf6824495497d96f07b56664/bc10c/3_1_0.webp 460w","/static/d0cc22babf6824495497d96f07b56664/966d8/3_1_0.webp 920w","/static/d0cc22babf6824495497d96f07b56664/445df/3_1_0.webp 1380w","/static/d0cc22babf6824495497d96f07b56664/a8768/3_1_0.webp 1816w"],"sizes":"(max-width: 920px) 100vw, 920px","type":"image/webp"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"source","properties":{"srcSet":["/static/d0cc22babf6824495497d96f07b56664/81c8e/3_1_0.png 230w","/static/d0cc22babf6824495497d96f07b56664/08a84/3_1_0.png 460w","/static/d0cc22babf6824495497d96f07b56664/c0255/3_1_0.png 920w","/static/d0cc22babf6824495497d96f07b56664/b1001/3_1_0.png 1380w","/static/d0cc22babf6824495497d96f07b56664/95fa1/3_1_0.png 1816w"],"sizes":"(max-width: 920px) 100vw, 920px","type":"image/png"},"children":[]},{"type":"text","value":"\n "},{"type":"element","tagName":"img","properties":{"className":["gatsby-resp-image-image"],"src":"/static/d0cc22babf6824495497d96f07b56664/c0255/3_1_0.png","alt":"3 1 0","title":"3 1 0","loading":"lazy","decoding":"async","style":"width:100%;height:100%;margin:0;vertical-align:middle;position:absolute;top:0;left:0;"},"children":[]},{"type":"text","value":"\n "}]},{"type":"text","value":"\n "}]},{"type":"text","value":"\n "}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Den röda pilen visar var programmet körs för tillfället. 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Det är osannolikt att man får ett program att fungera av en slump. Det är nödvändigt att man som programmerare förstår vilka värden ens programkod skapar vid ett visst skede medan programmet körs. Om de värden som lagras i variabler inte är sådana som man förväntar sig, finns det högst sannolikt en bugg i programmet."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Visualiseringsverktyget och "},{"type":"element","tagName":"code","properties":{"className":["language-text"]},"children":[{"type":"text","value":"print"}]},{"type":"text","value":"-satser är båda bra sätt för en programmerare att med egna ögon se att programmet gör exakt det som det ska göra."}]},{"type":"element","tagName":"in-browser-programming-exercise","properties":{"name":"Potenser av två","tmcname":"osa03-03_potenser_av_tva"},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Skapa ett program som först skriver ut 1 och därefter alltid det föregående talet multiplicerat med två."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Programmet avslutas då man skrivit ut det tal som är högst lika stort som det värde användaren angett. 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Till exempel kan vi skriva så här:"}]},{"type":"element","tagName":"div","properties":{"className":["gatsby-highlight"],"dataLanguage":"python"},"children":[{"type":"element","tagName":"pre","properties":{"className":["language-python"]},"children":[{"type":"element","tagName":"code","properties":{"className":["language-python"]},"children":[{"type":"text","value":"kurs "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":"\"Introkurs i programmering\""}]},{"type":"text","value":"\nvitsord "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","number"]},"children":[{"type":"text","value":"4"}]},{"type":"text","value":"\n\ntext "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":"\"Du fick \""}]},{"type":"text","value":"\ntext "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"+="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","string-interpolation"]},"children":[{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":"f\"vitsordet "}]},{"type":"element","tagName":"span","properties":{"className":["token","interpolation"]},"children":[{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"{"}]},{"type":"text","value":"vitsord"},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"}"}]}]},{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":" \""}]}]},{"type":"text","value":"\ntext "},{"type":"element","tagName":"span","properties":{"className":["token","operator"]},"children":[{"type":"text","value":"+="}]},{"type":"text","value":" "},{"type":"element","tagName":"span","properties":{"className":["token","string-interpolation"]},"children":[{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":"f\"i kursen "}]},{"type":"element","tagName":"span","properties":{"className":["token","interpolation"]},"children":[{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"{"}]},{"type":"text","value":"kurs"},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"}"}]}]},{"type":"element","tagName":"span","properties":{"className":["token","string"]},"children":[{"type":"text","value":"\""}]}]},{"type":"text","value":"\n\n"},{"type":"element","tagName":"span","properties":{"className":["token","keyword"]},"children":[{"type":"text","value":"print"}]},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":"("}]},{"type":"text","value":"text"},{"type":"element","tagName":"span","properties":{"className":["token","punctuation"]},"children":[{"type":"text","value":")"}]}]}]}]},{"type":"element","tagName":"sample-output","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Du fick vitsordet 4 i kursen Introkurs i programmering"}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"I det förra exemplet beräknade du summan av på varandra följande tal genom att alltid öka värdet inne i loopen."}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Samma fungerar också för strängar – du kan lägga till nya delar i en sträng inom en loop. Den här tekniken kan vara till nytta i följande uppgift."}]},{"type":"element","tagName":"in-browser-programming-exercise","properties":{"name":"Summa av varandra följande tal, version 2","tmcname":"osa03-05_varandra_foljandes_summa_2"},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Skapa en mer avancerad version av det föregående programmet. Nu ska programmet visa hur man kom till det resultat som man kommit fram till:"}]},{"type":"element","tagName":"sample-output","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Fram till talet: "},{"type":"element","tagName":"strong","properties":{},"children":[{"type":"text","value":"2"}]},{"type":"text","value":"\nRäknade 1 + 2 = 3"}]}]},{"type":"element","tagName":"sample-output","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Fram till talet: "},{"type":"element","tagName":"strong","properties":{},"children":[{"type":"text","value":"10"}]},{"type":"text","value":"\nRäknade 1 + 2 + 3 + 4 = 10"}]}]},{"type":"element","tagName":"sample-output","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Fram till talet: "},{"type":"element","tagName":"strong","properties":{},"children":[{"type":"text","value":"18"}]},{"type":"text","value":"\nRäknade 1 + 2 + 3 + 4 + 5 + 6 = 21"}]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Du kan anta att det tal användaren matar in är två eller större."}]}]},{"type":"element","tagName":"div","properties":{},"children":[{"type":"element","tagName":"quiz","properties":{"id":"f4bbb3b4-5e00-503a-a5c3-bb0253afc1ca"},"children":[]}]}]},"html":"

Efter den här delen

Att bli en skicklig programmerare kräver mycket övning. Man måste utveckla en problemlösningsförmåga och ha en förmåga att intuition komma fram till korrekta lösningar. Därför finns det massor av övningar av olika typer i den här kursen. Vissa övningar är enklare och baserar sig mera eller mindre direkt på materialet medan andra uppgifter är svårare och kräver tillämpande av kunskaper som man lärt sig under kursen.

En del uppgifter kan kännas svåra, men det är inte något att oroa sig över. Ingen av uppgifterna är obligatorisk och du behöver bara 25 % av poängen från varje modul för att klara den här kursen. Du kan läsa mera på kursens bedömningssida.

Uppgifterna är inte i svårighetsordning. Varje del introducerar vanligtvis några nya saker inom programmering och i samband finns relaterade uppgifter – både enklare och svårare. Om du stöter på en uppgift som känns oöverkomlig ska du fortsätta till nästa uppgift. Du kan alltid senare återkomma till tidigare uppgifter.

En uppgift som känns för svår just nu kommer sannolikt att vara ganska enkel om en månad.

I den förra delen bekantade vi oss med while True -loopen som ett sätt för att upprepa delar av kod. Så som loopen är uppbyggd är villkoret alltid True, alltså sant. Vi måste då avsluta loopen manuellt med break i något skede för att undvika en oändlig loop. Exempelvis:

# skriv ut tal tills värdet på variabeln a är 5\na = 1\nwhile True:\n    print(a)\n    a += 1\n    if a == 5:\n        break

1\n2\n3\n4

Men förstås behöver villkoret inte alltid vara True, utan det kan vara vilket som helst Boolean-uttryck. while-satsens struktur ser ut så här:

while <villkor>:\n    <block>

Idén är att koden körs om och om igen så länge som villkoret är sant. Villkorets värde kollas inför varje ny iteratione och när det är False kommer programmet inte att fortsätta köra loopen, utan i stället fortsätta med koden som kommer efter while-blocket.

\n \n \n \n \n \n \"3\n \n \n

Om någon av de här tre komponenterna fattas kommer loopen antagligen inte att fungera korrekt. Ett vanligt misstag är att låta bli att uppdatera variabler:

tal = 1\n\nwhile tal < 10:\n    print(tal)\n\nprint(\"Programmet är klart.\")

Här kommer värdet på variabeln tal aldrig att ändras. Programmet är fast i en oändlig loop. Samma kod upprepas tills användaren avslutar programmet, till exempel med tangentkombinationen Control + C:

1\n1\n1\n1\n1\n(det här fortsätter i all oändlighet...)

Skapa ett program som i en loop skriver ut vartannat tal från två till trettio. Varje tal skrivs ut på en ny rad.

Så här ska utskriften se ut:

\n2\n4\n6\n8\no.s.v. ...\n

Korrigera uppgiftens program...

print(\"Klara?\")\nnummer = int(input(\"Ge ett tal: \"))\nwhile nummer = 0:\nprint(nummer)\nprint(\"Gå!\")

...så att det fungerar på följande sätt:

Klara?\nGe ett tal: 5\n5\n4\n3\n2\n1\nGå!

Använd inte en while True -loop!

Skriva villkor

Alla Boolean-uttryck och kombinationer av dem kan användas som villkor i en while-loop. Till exempel skriver följande program ut vart tredje tal förutsatt att det är mindre än 100 och inte delbart med fem:

tal = int(input(\"Ge ett tal: \"))\n\nwhile tal < 100 and tal % 5 != 0:\n    print(tal)\n    tal += 3

Här följer två exempel på utskriften från programmet:

Ge ett tal: 28\n28\n31\n34\n37

Ge ett tal: 96\n96\n99

När man ger programmet värdet 28 kommer loopen att avslutas med 37, eftersom nästa tal är 40 – och är dividerbart med fem. När man ger värdet 96 kommer loopen att avsluta med 99 eftersom nästa tal är 102 – som inte är mindre än 100.

När du skriver en loop är det viktigt att se till att loopen alltid kommer att avslutas vid något skede. Det här programmet avslutas – eller inte – beroende på det värde som ges:

nummer = int(input(\"Ge ett tal: \"))\n\nwhile nummer != 10:\n    print(nummer)\n    nummer += 2

Om man ger ett jämnt tal som är lika med tio eller mindre, kommer loopen att avslutas:

Ge ett tal: 4\n4\n6\n8

I övriga fall kommer loopen att fortsätta oändligt eftersom det inte då finns något sätt för variabeln att bli lika med tio. Till exempel skulle 3 och 12 leda till en oändlig loop.

Skapa ett program som skriver ut alla tal som är lägre än det tal som användaren matat in. Börja från ett.

Fram till talet: 5\n1\n2\n3\n4

Använd inte True som villkor i while-loopen!

Tips för debuggning

Föreställ dig att du håller på att skapa ett aningen mer komplicerat program, som det i den följande uppgiften – Potenser av två. Du kunde till exempel börja så här:

stanna = int(input(\"Fram till talet\"))\ntal = 1\nwhile tal == stanna:\n   # kod

Programmet börjar med att läsa in det tal som användaren matar in och fortsätter till en while-loop med ett villkor.

Det är sannolikt att koden inte kommer att fungera på önskat sätt från början. Den kan behöva testas tio- eller till och med hundratals gånger före den fungerar korrekt.

Den här kodsnutten ber alltid om indata av användaren, vilket gör testandet långsamt och arbetsdrygt. Varje gång programmet testas måste ett värde anges.

Ett sätt att bli av med problemet är att hårdkoda ett värde i koden medan den testas:

# vi hårdkodar värdet här tills vidare\nstanna = 8 # int(input(\"Fram till talet\"))\ntal = 1\nwhile tal == stanna:\n   # kod

När programmet fungerar med det hårdkodade värdet, kan man enkelt testa med andra hårdkodade värden. När allt fungerar korrekt kan man gå tillbaka till att testa programmet så att användaren anger värdet.

Det här tricket fungerar väl med flera av de tester som används i betygsättningen av den här kursens uppgifter. Om testet berättar att något är fel med till exempel värdet 42 så kan värdet tillfälligt hårdkodas i programmet medan du letar efter buggen:

# testet meddelade att koden inte fungerade korrekt då indatat är 42\nstanna = 42 # int(input(\"Fram till talet\"))\ntal = 1\nwhile tal == stanna:\n   # kod

Debuggning med hjälp av print-satsen nämndes några gånger under den förra kursmodulen. De program som du skapar kommer att bli mer invecklade i och med att vi kommer längre i kursen. Då kommer mängden debuggning som du behöver göra också antagligen att öka i samma proportion. Vanliga orsaker till buggar finns ofta i de villkor som ska avsluta loopar – de fungerar eventuellt korrekt för vissa värden, medan andra värden orsakar problem. Det är inte alltid heller lätt att lägga märke till de här felen.

Därför är det nu dags att använda dig av print-satser för att debugga – om du inte redan har gjort det. Du hittar instruktioner i den första och fjärde delen av modul 2.

Vid sidan om print-satser finns även andra verktyg som kan använda för debuggning. Ett av dem är visualiseringsverktyget på Python Tutor -webbsidan. Verktyget låter dig köra din kod rad för rad och visar också de värden som är lagrade i variabler vid varje steg.

Koden – med några problem – från den förra delen visualiseras med Python Tutor i följande bild:

\n \n