《Python語言程序設(shè)計》課件-第四章 （中英文課件）

Python語言程序設(shè)計【函數(shù)的定義和調(diào)用】PythonLanguageProgramming[Definitionandinvocationoffunctions]def

function_name(arg1,arg2[,...]): statement [returnvalue]知識點【函數(shù)的定義和調(diào)用】函數(shù)定義示例函數(shù)的調(diào)用def函數(shù)名(參數(shù)列表):

函數(shù)體defsumOf(a,b):

returna+ba=1

b

=2

c=sumOf(a,b)

print(str(c))1.函數(shù)通過def定義注意：該行結(jié)尾一定要加上冒號!!def

function_name(arg1,arg2[,...]): statement [returnvalue]KnowledgePoints[Definitionandinvocationoffunctions]functiondefinitionExamplefunctioniscalledDeffunctionname(parameterlist):

functionbodydefsumOf(a,b):

returna+ba=1

b

=2

c=sumOf(a,b)

print(str(c))1.FunctionsaredefinedbydefNote:Makesuretoputacolonattheendofthatline!!!!def

function_name(arg1,arg2[,...]): statement [returnvalue]知識點【函數(shù)的定義和調(diào)用】2.函數(shù)名的要求（1）函數(shù)名必須以下劃線或字母開頭，可以包含任意字母、數(shù)字或下劃線的組合。不能使用任何的標(biāo)點符號，空格也不可以；（2）函數(shù)名是區(qū)分大小寫的；（3）函數(shù)名不能用保留字。3.函數(shù)形參和實參函數(shù)中的參數(shù)名稱為‘形參’，調(diào)用函數(shù)時傳遞的值為‘實參’。def

function_name(arg1,arg2[,...]): statement [returnvalue]2.Requirementsforfunctionnames(1)functionnamemuststartwithanunderscoreorletter,cancontainanycombinationofletters,numbersorunderscores.Cannotuseanypunctuation,spacesarenotallowed;(2)Functionnamesarecase-sensitive;(3)Functionnamescannotusereservedwords.3.functionformandrealparametersThenameoftheparameterinthefunctionis'formalparameter',Thevaluepassedwhenthefunctioniscalledisa'realparameter'.KnowledgePoints[Definitionandinvocationoffunctions]知識點【函數(shù)的定義和調(diào)用】3.函數(shù)形參和實參函數(shù)定義時的參數(shù)名稱為‘形參’，調(diào)用函數(shù)時傳遞的值為‘實參’。觀察2：調(diào)用函數(shù)fun（）前后k的值的變化觀察1：形參和實參形參：a實參：k沒有任何變化?。?！3.functionformandrealparametersThenameoftheparameterwhendefiningthefunctionis'formalparameter',andthevaluepassedwhencallingthefunctionis'realparameter'.Observe2:Changeofkvaluebeforeandaftercallingfunctionfun()Observation1:FormalandrealparametersFormalparameter:aActualparameter:kNothinghaschanged!!!!KnowledgePoints[Definitionandinvocationoffunctions]提問【函數(shù)的定義和調(diào)用】問題1:

關(guān)于函數(shù)名，下列說法正確的是（）A.函數(shù)名必須以下劃線和數(shù)字開頭B.函數(shù)名可以包含任意字母、數(shù)字或下劃線的組合C.函數(shù)名能使用任何的標(biāo)點符號D.函數(shù)名不區(qū)分大小寫問題2:

說出函數(shù)形參和實參的區(qū)別。Askaquestion[Definitionandinvocationoffunctions]Question1:Regardingfunctionnames,thefollowingstatementsarecorrect()A.FunctionnamesmuststartwithanunderscoreandanumberB.Thefunctionnamecancontainanycombinationofletters,numbers,orunderscoresC.FunctionnamescanuseanypunctuationD.FunctionnamesarenotcasesensitiveQuestion2:Namethedifferencebetweenformalandrealparametersofafunction.Python語言程序設(shè)計【函數(shù)參數(shù)】PythonLanguageProgramming[FunctionParameters]知識點【函數(shù)參數(shù)】函數(shù)的參數(shù)分類：1.必需參數(shù)2．默認(rèn)參數(shù)3．關(guān)鍵字參數(shù)4.不定長參數(shù)5.匿名函數(shù)中的參數(shù)KnowledgePoints[FunctionArguments]Classificationofargumentstofunctions：1.Requiredparameters2.Defaultparameters3.Keywordparameters4.Indefinitelengthparameters5.Parametersinanonymousfunctions知識點【函數(shù)參數(shù)】1.必需參數(shù)指的是函數(shù)要求傳入的參數(shù)，調(diào)用時必須以正確的順序傳入，并且調(diào)用時的數(shù)量必須和聲明時一致，否則會出現(xiàn)語法錯誤?！纠繋П匦鑵?shù)的函數(shù)sayHello1234567defsayHello(name):

print("Hello!"+name)

return

#調(diào)用sayHello函數(shù)

sayHello("DerisWeng")

sayHello()調(diào)用sayHello(“DerisWeng”)Hello!DerisWeng調(diào)用sayHello()報錯!!![FunctionArguments]1.Requiredparametersreferstothefunctionrequiredtopassparameters,thecallmustbepassedinthecorrectorder,andthenumberofcallsmustbeconsistentwiththedeclaration,otherwisetherewillbesyntaxerrors.[Example]SayHellofunctionwithrequiredparameters1234567defsayHello(name):

print("Hello!"+name)

return

#CallthesayHellofunction

sayHello("DerisWeng")

sayHello()CallsayHello("DerisWeng")Hello!DerisWengCallsayHello()ErrorReporting!!!!KnowledgePoints知識點【函數(shù)參數(shù)】2.默認(rèn)參數(shù)指的是當(dāng)函數(shù)中的參數(shù)設(shè)置了默認(rèn)值，在調(diào)用函數(shù)時，如果沒有給該參數(shù)傳遞任何值，則函數(shù)將會使用默認(rèn)值?！纠繋J(rèn)參數(shù)的函數(shù)sayHello1234567defsayHello(name,times=1):

print(("Hello!"+name)*times)

return

#調(diào)用sayHello函數(shù)

sayHello("DerisWeng")

sayHello("DerisWeng",3)調(diào)用sayHello(“DerisWeng”)Hello!DerisWeng調(diào)用sayHello(“DerisWeng”,3)Hello!DerisWengHello!DerisWengHello!DerisWeng[FunctionArguments]2.thedefaultparametersmeansthatwhenadefaultvalueissetforaparameterinafunction,thefunctionwillusethedefaultvalueifnovalueispassedtotheparameterwhenthefunctioniscalled.[Example]ThefunctionsayHellowithdefaultparameters1234567defsayHello(name,times=1):

print(("Hello!"+name)*times)

return

#CallthesayHellofunction

sayHello("DerisWeng")

sayHello("DerisWeng",3)CallsayHello("DerisWeng")Hello!DerisWengCallsayHello("DerisWeng",3)Hello!DerisWengHello!DerisWengHello!DerisWengKnowledgePoints知識點【函數(shù)參數(shù)】2.默認(rèn)參數(shù)在聲明函數(shù)形參時，先聲明沒有默認(rèn)值的形參，然后再聲明有默認(rèn)值的形參。即默認(rèn)值必須在非默認(rèn)參數(shù)之后。上面這么定義是不允許的。123defsayHello(times=1,name):

print(("Hello!"+name)*times)

return是否正確？[FunctionArguments]Whendeclaringafunction'sformalparameter,firstdeclaretheformalparameterwithoutadefaultvalue,andthendeclaretheformalparameterwithadefaultvalue.Thatis,thedefaultvaluemustcomeafterthenon-defaultparameter.Theabovedefinitionisnotallowed.123defsayHello(times=1,name):

print(("Hello!"+name)*times)

returnIsthatcorrect?KnowledgePoints2.thedefaultparameters知識點【函數(shù)參數(shù)】3.關(guān)鍵字參數(shù)指的是如果某個函數(shù)有很多參數(shù)，在調(diào)用的時候通過參數(shù)名來對參數(shù)進行賦值。【例】使用關(guān)鍵字參數(shù)調(diào)用函數(shù)1234567defsayHello(name,times=1):

print(("Hello!"+name)*times)

return

#調(diào)用sayHello函數(shù)

sayHello(name="DerisWeng")

sayHello(times=3,name="DerisWeng")調(diào)用sayHello(name=“DerisWeng”)Hello!DerisWeng調(diào)用sayHello(times=3,name=“DerisWeng”)Hello!DerisWengHello!DerisWengHello!DerisWengKnowledgePoints[FunctionArguments]3.KeywordparametersThisreferstothefactthatifafunctionhasalotofparameters,theparameternamesareusedtoassignvaluestotheparameterswhenthefunctioniscalled.[Example]Callingafunctionwithakeywordargument1234567defsayHello(name,times=1):

print(("Hello!"+name)*times)

return

#CallthesayHellofunction

sayHello(name="DerisWeng")

sayHello(times=3,name="DerisWeng")CallsayHello(name="DerisWeng")Hello!DerisWengCallsayHello(times=3,name="DerisWeng")Hello!DerisWengHello!DerisWengHello!DerisWeng知識點【函數(shù)參數(shù)】4.不定長參數(shù)指的是函數(shù)的參數(shù)可以根據(jù)需要變化個數(shù)?！纠繋в胁欢ㄩL參數(shù)的函數(shù)sayHello123456789defsayHello(name,*vars):

print("你好:")

print(name)

forvarinvars:

print(var)

return

#調(diào)用sayHello函數(shù)

sayHello("DerisWeng")

sayHello("DerisWeng","好好學(xué)習(xí)","天天向上")調(diào)用sayHello(“DerisWeng”)你好:DerisWeng調(diào)用sayHello(“DerisWeng”,“好好學(xué)習(xí)”,“天天向上”)你好:DerisWeng好好學(xué)習(xí)天天向上KnowledgePoints[FunctionArguments]4.IndefinitelengthparametersThisreferstothefactthatthenumberofargumentstoafunctioncanbevariedasneeded.[Example]SayHellofunctionwithvariablelengthparameter123456789defsayHello(name,*vars):

Print("Hello:")

print(name)

forvarinvars:

print(var)

return

#CallthesayHellofunction

sayHello("DerisWeng")

SayHello("DerisWeng","Studyhard","Makeprogresseveryday")CallsayHello("DerisWeng")HelloDerisWengCallsayHello("DerisWeng","goodgoodstudy","daydayup")Hello.DerisWenggoodgoodstudyDaybyday知識點【函數(shù)參數(shù)】5.匿名函數(shù)中的參數(shù)匿名函數(shù)指的是不用def關(guān)鍵字對函數(shù)進行定義，直接使用lambda來創(chuàng)建函數(shù)。?！纠坷胠ambda創(chuàng)建sum函數(shù)1234sum=lambdaa,b:a+b

#調(diào)用sum函數(shù)

print(sum(5,10))調(diào)用print(sum(5,10))15KnowledgePoints[FunctionArguments]5.parametersinanonymousfunctionsAnonymousfunctionreferstotheuseoflambdatocreateafunctionwithoutdefiningthefunctionwiththedefkeyword[Example]Uselambdatocreatesumfunction1234sum=lambdaa,b:a+b

#Callthesumfunction

print(sum(5,10))Callprint(sum(5,10))15知識點【函數(shù)參數(shù)】5.匿名函數(shù)中的參數(shù)匿名函數(shù)指的是不用def關(guān)鍵字對函數(shù)進行定義，直接使用lambda來創(chuàng)建函數(shù)?！纠坷胠ambda創(chuàng)建sayHello函數(shù)1234sayHello=lambdaname,times:print((“Hello!"+name)*times)

#調(diào)用sum函數(shù)sayHello("Derisweng",2)Hello!DeriswengHello!Derisweng[FunctionArguments]5.parametersinanonymousfunctionsAnonymousfunctionsrefertotheuseoflambdatocreatefunctionswithoutusingthedefkeywordtodefinethem.[Example]CreatesayHellofunctionwithlambda1234sayHello=lambdaname,times:print((“Hello!"+name)*times)

#CallthesumfunctionsayHello("Derisweng",2)Hello!DeriswengHello!DeriswengKnowledgePoints提問【函數(shù)參數(shù)】問題:

以下程序輸出結(jié)果為？

deffun(x,y):

x=x+y

y=x-y

x=x-y

print(x,y)

x=2

y=3

fun(x,y)

print(x,y)Askaquestion[FunctionArguments]Question:Theoutputofthefollowingprogramis?deffun(x,y):

x=x+y

y=x-y

x=x-y

print(x,y)

x=2

y=3

fun(x,y)

print(x,y)Python語言程序設(shè)計【return語句】PythonLanguageProgramming[returnstatement]知識點【return語句】return語句用來返回函數(shù)的結(jié)果或者退出函數(shù)。【例】return不為None的情況123456defsum(a,b):

returna+b

#調(diào)用sum函數(shù)

total=sum(5,10)

print(total)不帶參數(shù)值的return語句返回None，帶參數(shù)值的return語句返回的就是參數(shù)的值。15輸出結(jié)果：KnowledgePoints[returnstatement]returnstatementUsedtoreturntheresultofafunctionortoexitafunction.[Example]IfreturnisnotNone123456defsum(a,b):

returna+b

#Callthesumfunction

total=sum(5,10)

print(total)ThereturnstatementwithoutparametervaluereturnsNone,andthereturnstatementwithparametervaluereturnstheparametervalue.15Outputresult：知識點【return語句】return語句用來返回函數(shù)的結(jié)果或者退出函數(shù)。【例】return為None的情況123defsayHello(name):

print("Hello!"+name)

return#此處return可以不用寫函數(shù)并非一定要包含return語句。如果函數(shù)沒有包含return語句，Python將認(rèn)為該函數(shù)返回的是None，即returnNone。None表示沒有任何東西的特殊類型。KnowledgePoints[returnstatement][Example]WhenreturnisNone123defsayHello(name):

print("Hello!"+name)

Return#NoneedtowritereturnhereThefunctiondoesnothavetocontainareturnstatement.Ifthefunctiondoesnotcontainareturnstatement,PythonwillassumethatthefunctionreturnsNone,thatis,returnNone.Noneindicatesaspecialtypewithoutanything.returnstatementUsedtoreturntheresultofafunctionortoexitafunction.提問【return語句】問題:

如何讓函數(shù)向調(diào)用者返回一個值？AskaquestionQuestion:HowcanImakeafunctionreturnavaluetothecaller?[returnstatement]Python語言程序設(shè)計【全局變量與局部變量】PythonLanguageProgramming[GlobalandLocalVariables]知識點【全局變量與局部變量】局部變量指在函數(shù)定義內(nèi)聲明的變量?！纠亢瘮?shù)內(nèi)為局部變量1234567defsum(a,b):

total=a+b#total在這里是局部變量.

print("函數(shù)內(nèi)是局部變量:",total)

returntotal

#調(diào)用sum函數(shù)

sum(5,10)它們與函數(shù)外（即便是具有相同的名稱）的其他變量沒有任何關(guān)系。即變量的作用域只在函數(shù)的內(nèi)部。函數(shù)內(nèi)是局部變量:15輸出結(jié)果：KnowledgePoints[GlobalandLocalVariables]localvariablesReferstoavariabledeclaredwithinafunctiondefinition.[Example]Alocalvariableinsideafunction1234567defsum(a,b):

Total=a+b#totalisalocalvariablehere

Print("Localvariableinfunction:",total)

returntotal

#Callthesumfunction

sum(5,10)Theyhavenothingtodowithothervariablesoutsidethefunction(eveniftheyhavethesamename).Thatis,thevariablesarescopedonlyinsidethefunction.Functionsarelocalizedwithinfunctions:15Outputresult:知識點【全局變量與局部變量】全局變量在函數(shù)外部聲明的變量稱為全局變量，程序中的任何地方都可以讀取它?！纠坷胓lobal實現(xiàn)函數(shù)內(nèi)訪問全局變量12345678defshowName():

globalname

print("你的姓名："+name)

name="Weng"

#調(diào)用showName函數(shù)

name="Deris"

showName()

print(("你現(xiàn)在的姓名："+name))如果需要在函數(shù)內(nèi)部訪問全局變量，一般要用到global關(guān)鍵字。你的姓名：Deris你現(xiàn)在的姓名：Weng輸出結(jié)果：globalvariablesAvariabledeclaredoutsideafunctioniscalledaglobalvariableandcanbereadanywhereintheprogram.[Example]Usingglobaltoaccessglobalvariableswithinafunction12345678defshowName():

globalname

Print("Yourname:"+name)

name="Weng"

#CalltheshowNamefunction

name="Deris"

showName()

Print(("Yourcurrentname:"+name))Ifyouneedtoaccessglobalvariableswithinafunction,yougenerallyneedtousetheglobalkeyword.Yourname:DerisYourcurrentname:WengKnowledgePoints[GlobalandLocalVariables]Outputresult:知識點【全局變量與局部變量】全局變量【例】沒有用global的情況下，無法在函數(shù)內(nèi)部修改全局變量。123456789name="Deris"

defsayHello():

print("hello"+name+"!")

defchangeName(newName):

name=newName

#調(diào)用函數(shù)

sayHello()

changeName("Weng")

sayHello()helloDeris!helloDeris!輸出結(jié)果：globalvariables[Example]Whenglobalisnotused,globalvariablescannotbemodifiedinsidethefunction.123456789name="Deris"

defsayHello():

print("hello"+name+"!")

defchangeName(newName):

name=newName

#Callingfunctions

sayHello()

changeName("Weng")

sayHello()helloDeris!helloDeris!KnowledgePoints[GlobalandLocalVariables]Outputresult:知識點【全局變量與局部變量】全局變量【例】用global在函數(shù)內(nèi)部修改全局變量。12345678910name="Deris"

defsayHello():

print("hello"+name+"!")

defchangeName(newName):

globalname

name=newName

#調(diào)用函數(shù)

sayHello()

changeName("Weng")

sayHello()helloDeris!helloWeng!輸出結(jié)果：globalvariables[Example]Useglobaltomodifyglobalvariableswithinafunction.12345678910name="Deris"

defsayHello():

print("hello"+name+"!")

defchangeName(newName):

globalname

name=newName

#Callingfunctions

sayHello()

changeName("Weng")

sayHello()helloDeris!helloWeng!KnowledgePoints[GlobalandLocalVariables]Outputresult:提問【全局變量與局部變量】問題:全局變量與局部變量有什么區(qū)別？Askaquestion[GlobalandLocalVariables]Question:Whatisthedifferencebetweenaglobalvariableandalocalvariable?Python語言程序設(shè)計【函數(shù)作用域+模塊+縮進格式】PythonLanguageProgramming[DocumentString+FormattedOutput+Built-inFunctions]知識點【函數(shù)作用域】變量的作用域指的是變量在程序中的哪些地方可以訪問或者可見。1.每個模塊都有自已的全局作用域。2.函數(shù)定義的對象屬局部作用域，只在函數(shù)內(nèi)有效，不會影響全局作用域中的對象。3.賦值對象屬局部作用域，除非使用global關(guān)鍵字進行聲明。12345678910name="Deris"

defsayHello():

print("hello"+name+"!")

defchangeName(newName):

globalname

name=newName

#調(diào)用函數(shù)

sayHello()

changeName("Weng")

sayHello()KnowledgePoints[FunctionScope]thescopeofthevariablereferstowhereintheprogramthevariableisaccessibleorvisible.1.eachmodulehasitsownglobalscope.2.functiondefinitionoftheobjectisalocalscope,onlyinthefunctionisvalid,willnotaffecttheglobalscopeoftheobject.3.Theassignmentobjectislocallyscopedunlessdeclaredwiththeglobalkeyword.12345678910name="Deris"

defsayHello():

print("hello"+name+"!")

defchangeName(newName):

globalname

name=newName

#Callingfunctions

sayHello()

changeName("Weng")

sayHello()課后練習(xí)【函數(shù)作用域】問題:課后請查閱一下什么是LEGB規(guī)則？After-schoolexercises[FunctionScope]Question:WhatareLEGBrulesafterclass?知識點【模塊】模塊一個包含所有定義的函數(shù)和變量的文件，模塊必須以.py為后綴名。pythonhello.py這是“hello.py”模塊hello12345678#hello.py

defsayHello():

str="hello"

print(str)

if__name__=="__main__":

print("這是hello.py模塊")

sayHello()模塊可以從其他程序中引入(import)，引入后就可以用模塊中的函數(shù)和功能，從而達到代碼復(fù)用的作用。>>>importhello>>>hello.__name__'hello'KnowledgePoints[Module]ModuleAfilecontainingalldefinedfunctionsandvariables.Themodulemusthavethesuffix.py.pythonhello.pyThisisthe"hello.py"modulehello12345678#hello.py

defsayHello():

str="hello"

print(str)

if__name__=="__main__":

Print("Thisisthehello.pymodule")

sayHello()Modulescanbeimportedfromotherprograms,andthenthefunctionsandfunctionsinthemodulecanbeusedtoachievecodereuse.>>>importhello>>>hello.__name__'hello'課后練習(xí)【模塊】問題:模塊的__name__的作用和用法？After-schoolexercises[Module]Question:Whatisthefunctionandusageofthe__name__ofthemodule?知識點【編程縮進格式】縮進指在代碼行開始部分的空格。123456defsum(a,b):

returna+b

#調(diào)用sum函數(shù)

total=sum(5,10)

print(total)代碼行開頭的前導(dǎo)空白用于確定語句的分組，同樣的縮進級別的語句屬于同一語句塊。（四個空格）或Tab（不建議使用）KnowledgePoints[ProgrammingIndentFormat]Indentreferstoaspaceatthebeginningofalineofcode.123456defsum(a,b):

returna+b

#Callthesumfunction

total=sum(5,10)

print(total)Leadingwhitespaceatthebeginningofalineofcodeisusedtodeterminethegroupingofstatementswiththesamelevelofindentationintothesamestatementblock.(fourspaces)orTab(notrecommended)知識點【編程縮進格式】縮進的錯誤用法！運行這段程序的結(jié)果如下：File"例1-3.py",line2print('IamPython');^ndentationError:unexpectedindent12print('Hello,')

print('IamPython')#注意此處特地在前面留了一個空格KnowledgePoints[ProgrammingIndentFormat]Wronguseofindentation!Theresultofrunningthisprogramisasfollows.File"Example1-3.py",line2print('IamPython');^ndentationError:unexpectedindent12print('Hello,')

Print('IamPython')#Notethataspaceisspeciallyleftinfront課后練習(xí)【編程縮進格式】問題:平級的語句行（代碼塊）的縮進可以不同嗎？After-schoolexercises[ProgrammingIndentFormat]Question:Cantheindentationofleveledstatementlines(codeblocks)bedifferent?Python語言程序設(shè)計【文檔字符串+格式化輸出+內(nèi)置函數(shù)】PythonLanguageProgramming[DocumentString+FormattedOutput+Built-inFunctions]知識點【文檔字符串】文檔字符串Python用三個引號標(biāo)識文檔字符串的開始和結(jié)尾。123456importmath

defarea(radius):

"""

returntheareaofcircle

"""

returnmath.pi*