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Programming Environments •
Thereareseveralwaysofcrea/ngacomputerprogram
• UsinganIntegratedDevelopmentEnvironment(IDE)•
Usingatexteditor
• Youshouldusethemethodyouaremostcomfortablewith.•
I’llPyCharmforallmyin-classexamples
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IDE components • Thesourcecodeeditorcanhelpprogrammingby:
• Lis/nglinenumbersofcode• Colorlinesofcode(comments,text…)•
Auto-indentsourcecode
• Outputwindow
• Debugger
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The PyCharm IDE
Output
Editor
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Files
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Your first program • Tradi/onal‘HelloWorld’programinPython
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• Wewillexaminethisprograminthenextsec/on•
TypingtheprogramintoyourIDEwouldbegoodprac/ce!•
Becarefulofspellinge.g.,‘print’vs.‘primt’•
PyTHoniSCaSeSeNsI/Ve.
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Text editor programming •
Youcanalsouseasimpletexteditortowriteyoursourcecode•
OncesavedasHello.py,youcanuseaconsolewindowto:
• Compiletheprogram• Runtheprogram
Compile/executeOutput
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Organize your work • Your‘sourcecode’isstoredin.pyfiles•
Createafolderforthiscourse
• Createonefolderperprograminsidethecoursefolder•
Aprogramcanconsistofseveral.pyfiles
• BesureyouknowwhereyourIDEstoresyourfiles•
Youneedtobeabletofindyoufiles
• Backupyourfiles:• ToaUSBflashdrive• Toanetworkdrive
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Python interactive mode •
Likeotherlanguagesyoucanwrite/saveacompletePythonprograminafileandlettheinterpreterexecutetheinstruc/onsallatonce.
•
Alterna/velyyoucanruninstruc/onsoneata/meusinginterac/vemode.•
Itallowsquick‘testprograms’tobewriben.•
Interac/vemodeallowsyoutowritepythonstatementsdirectlyintheconsolewindow
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Source Code to a Running Program •
Thecompilerreadsyourprogramandgeneratesbytecodeinstruc/ons(simpleinstruc/onsforthePythonVirtualmachine)•
ThePythonVirtualmachineisaprogramthatissimilartotheCPUofyourcomputer
•
Anynecessarylibraries(e.g.fordrawinggraphics)areautoma/callylocatedandincludedbythevirtualmachine
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Let’s Get Started! • OpenthePyCharmonyoulabcomputer•
Wearegoingtostartsimple,andaswelearnmoreaboutPython,we’lluseaddi/onalfeaturesinPyCharm
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“Hello World” • TypethefollowingintotheEditor:# My first Python
program
print(“Hello World!”)
• Saveyourfileas“hello.py”
• Thisis“StepTwoWriteasimpleprogram”frompage7inyourtext.•
Remember–Pythoniscasesensi(ve
•
Youhavetoentertheupperandlowercaselebersexactlyasthisappearabove
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Analyzing Your First Program •
APythonprogramcontainsoneormorelinesofinstruc/ons(statements)thatwillbetranslatedandexecutedbytheinterpreter#
My first Python program
print(“Hello World!”)
•
Thefirstlineisacomment(astatementthatprovidesdescrip/veinforma/onabouttheprogramtoprogrammers).
•
Thesecondlinecontainsastatementthatprintsalineoftextonscreen“Hello,World!”
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Basic Python Syntax: Print •
UsingthePython‘print()’func/on.
•
Afunc/onisacollec/onofprogramminginstruc/onsthatcarryoutapar/culartask(inthiscasetoprintavalueonscreen).
• It’scodethatsomebodyelsewroteforyou!
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Syntax for Python Functions •
Touse,orcall,afunc/oninPythonyouneedtospecify:
•
Thenameofthefunc/onthatyouwanttouse(inthepreviousexamplethenamewasprint)
•
Anyvalues(arguments)neededbythefunc/ontocarryoutitstask(inthiscase,“HelloWorld!”).
•
Argumentsareenclosedinparenthesesandmul/pleargumentsareseparatedwithcommas.
•
Asequenceofcharactersenclosedinquota/onsmarksarecalledastring
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More Examples of the print Function •
Prin/ngnumericalvalues
• print(3+4)• Evaluatestheexpression3+4anddisplays7
• Passingmul/plevaluestothefunc/on• print(“theansweris”,6*7)•
DisplaysTheansweris42•
Eachvaluepassedtothefunc/onisdisplayed,oneajeranother,withablank
spaceajereachvalue
•
Bydefaulttheprintfunc/onstartsanewlineajeritsargumentsareprinted•
print(“Hello”)• print(“World!”)• Printstwolinesoftext• Hello•
World!
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Our Second Program (Page 12, printtest.py) ## # Sample Program
that demonstrates the print function # # Prints 7 print(3 + 4) #
Print Hello World! on two lines print(“Hello”) print(“World!”) #
Print multiple values with a single print function call print(“My
favorite number are”, 3 + 4, “and” 3 + 10) # Print Hello World! on
two lines print(“Goodbye”) print() print(“Hope to see you
again”)
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Errors • TherearetwoCategoriesofErrors:
• Compile-/meErrors• akaSyntaxErrors
• Spelling,capitaliza/on,punctua/on•
Orderingofstatements,matchingofparenthesis,quotes…
• Noexecutableprogramiscreatedbythecompiler•
Correctfirsterrorlisted,thencompileagain.
• Repeatun/lallerrorsarefixed• Run-/meErrors
• akaLogicErrors•
Theprogramruns,butproducesunintendedresults•
Theprogrammay‘crash’
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Syntax Errors • Syntaxerrorarecaughtbythecompiler•
Whathappensifyou
• Miss-capitalizeaword: Print("HelloWorld!")• Leaveoutquotes
print(HelloWorld!)• Mismatchquotes print("HelloWorld!')•
Don’tmatchbrackets print('Hello'
• TypeeachexampleaboveintheWingPythonShellwindow•
Whaterrormessagesaregenerated?
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Logic Errors • Whathappensifyou
• Dividebyzero print(1/0)• Misspelloutput
print("Hello,Word!")• Forgettooutput Removeline2
• Programswillcompileandrun• Theoutputmaynotbeasexpected
• TypeeachexampleaboveinthePyCharmPythonShellwindow•
Whaterrormessagesaregenerated?
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Summary: Computer Basics •
Computersrapidlyexecuteverysimpleinstruc/ons•
AProgramisasequenceofinstruc/onsanddecisions
•
Programmingistheart(andscience)ofdesigning,implemen/ng,andtes/ngcomputerprograms
•
TheCentralProcessingUnit(CPU)performsprogramcontrolanddataprocessing
•
Storagedevicesincludememoryandsecondarystorage(e.g.,aUSBFlashDrive)
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Summary: Python •
PythonwasdesignedinawaythatmakesiteasiertolearnthanotherprogramminglanguagessuchasJava,CandC++.
• ThedesignersgoalwastogivePythonsimplerandcleanersyntax.•
Setasidesome/metobecomefamiliarwiththeprogrammingenvironmentthatyouwilluseforyourclasswork.•
Itisimportanttoprac/cewiththetoolsoyoucanfocusonlearningPython
•
Aneditorisaprogramforenteringandmodifyingtext,suchasaPythonprogram.
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Summary: Python • Pythoniscasesensi/ve.
•
Youmustbecarefulaboutdis/nguishingbetweenupperandlowercaselebers.
•
ThePythoncompilertranslatessourcecodeintobytecodeinstruc/onsthatareexecutedbytheVirtualmachine.
•
Afunc/oniscalledbyspecifyingthefunc/on’snameanditsparameters.
• Astringisasequenceofcharactersenclosedinquota/onmarks.
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Summary: Errors and pseudo code •
Acompile-/meerrorisaviola/onoftheprogramminglanguagerulesthatisdetectedbythecompiler.
•
Arun-/meerrorcausesaprogramtotakeanac/onthattheprogrammerdidnotintend.
•
Pseudocodeisaninformaldescrip/onofasequenceofstepsforsolvingaproblem.
•
Analgorithmforsolvingaproblemisasequenceofstepsthatisunambiguous,executable,andtermina/ng.
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Poll Everywhere • PollEv.com/donpaberson223
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