Python 学习笔记Word格式文档下载.docx
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Python 学习笔记Word格式文档下载.docx
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Moduloreturnstheremainderfromadivision.So,ifyoutype
3%2,itwillreturn
1,because2goesinto3evenlyonce,with1leftover.
Instructions
Usemodulotoset
spam
equalto
1.Youcanuseanytwonumbersthatwillleavearemainderof
1
todothis.
BringingItAllTogether
Nicework!
Sofar,you'
velearnedabout:
∙Variables,whichstorevaluesforlateruse
∙Datatypes,suchasnumbersandbooleans
∙Whitespace,whichseparatesstatements
∙Comments,whichmakeyourcodeeasiertoread
∙Arithmeticoperations,including+,
-,
*,
/,
**,and
%
Let'
sputourknowledgetowork.
1.Writeasingle-linecommenton
line1.Itcanbeanything!
(Makesureitstartswith
#)
2.Setthevariable
monty
equaltoTrue.
3.Setanothervariable
python
1.234.
4.Setathirdvariable
monty_pythonequalto
squared.
Strings说白了就是加双引号
Anotherusefuldatatypeisthe
string.A
string
cancontainletters,numbers,andsymbols.
name="
Ryan"
age="
19"
food="
cheese"
1.Intheaboveexample,wecreateavariable
name
andsetittothestringvalue
"
.
2.Wealsoset
age
to
and
foodto
Stringsneedtobewithinquotes.
Createanewvariable
brian
andassignitthestring
Hello
life!
Escapingcharacters用\
Therearesomecharactersthatcauseproblems.Forexample:
'
There'
sasnakeinmyboot!
ThiscodebreaksbecausePythonthinkstheapostrophein
s'
endsthestring.Wecanusethebackslashtofixtheproblem,likethis:
There\'
Fixthestringintheeditor!
AccessbyIndexn指的是第几个字母,从0开始
Greatwork!
Eachcharacterinastringisassignedanumber.Thisnumberiscalledtheindex.Checkoutthediagramintheeditor.
c="
cats"
[0]
n="
[3]
1.Intheaboveexample,wecreateanewvariablecalled
c
andsetitto"
c"
thecharacteratindexzeroofthestring
2.Next,wecreateanewvariablecalled
n
n"
thecharacteratindexthreeofthestring"
InPython,westartcountingtheindexfromzeroinsteadofone.
On
line13,assignthevariablefifth_letter
equaltothefifthletterofthestring"
MONTY"
Rememberthatthefifthletterisnotatindex5.Startcountingyourindicesfromzero.
Thestring"
PYTHON"
hassixcharacters,
numbered0to5,asshownbelow:
+---+---+---+---+---+---+
|P|Y|T|H|O|N|
012345
Soifyouwanted"
Y"
youcouldjusttype
[1](alwaysstartcountingfrom0!
)
Stringmethods
Nowthatweknowhowtostorestrings,let'
sseehowwecanchangethemusing
stringmethods.
Stringmethods
letyouperformspecifictasksforstrings.
We'
llfocusonfourstringmethods:
1.len()
2.lower()
3.upper()
4.str()
sstartwithlen(),whichgetsthelength(thenumberofcharacters)ofastring!
1.On
line1,createavariablenamedparrot
andsetittothestring"
NorwegianBlue"
.On
line2,typelen(parrot)
aftertheword
print,likeso:
len(parrot).Theoutputwillbethenumberoflettersin
!
3.Welldone!
4.Youcanusethe
lower()
methodtogetridofallthecapitalizationinyourstrings.Youcall
likeso:
5."
.lower()
6.whichwillreturn
ryan"
7.Instructions
8.Call
on
parrot
(after
print)on
line3
intheeditor.
答案:
parrot="
printparrot.lower()
upper()
Nowyourstringis100%lowercase!
Asimilarmethodexiststomakeastringcompletelyuppercase.
Call
upper()
printon
line3)inordertocapitalizeallthecharactersinthestring!
str()
slookat
str(),whichisalittlelessstraightforward.The
str()methodturnsnon-stringsintostrings!
Forexample:
str
(2)
wouldturn
2
into
2"
1.Createavariable
pi
andsetitto3.14
line4.
2.Call
str(pi)
line5,after
print.
DotNotation
stakeacloserlookatwhyyouuselen(string)
str(object),butdotnotation(suchas
String"
.upper())fortherest.
lion="
roar"
len(lion)
lion.upper()
Methodsthatusedotnotationonlyworkwithstrings.
Ontheotherhand,
len()
str()canworkonotherdatatypes.
line3,callthe
functionwiththeargument
ministry.
2.On
line4,invokethe
ministry'
s.upper()
function.
3.PrintingStrings
4.Theareawherewe'
vebeenwritingourcodeiscalledthe
editor.
5.The
console
(thewindowintheupperright)iswheretheresultsofyourcodeisshown.
6.print
simplydisplaysyourcodeintheconsole.
8.Print"
MontyPython"
totheconsole.
PrintingVariables反是定义了的,print后不需要””
Nowthatwe'
veprintedstrings,let'
sprintvariables
1.Declareavariablecalledthe_machine_goes
andassignitthestringvalue
Ping!
line5.
2.Goaheadandprintthe_machine_goes
in
line6.
Hint
Makesureyou'
resettingyourvariablelikethis:
Assignthestring"
to
thevariablethe_machine_goeson
line5,thenprintitoutonline6!
the_machine_goes="
printthe_machine_goes
StringConcatenation
Youknowaboutstrings,andyouknowaboutarithmeticoperators.Nowlet'
scombinethetwo!
print"
Life"
+"
of"
Brian"
Thiswillprintoutthephrase
LifeofBrian.
+
operatorbetweenstringswill'
add'
themtogether,oneaftertheother.Noticethattherearespacesinsidethequotationmarksafter
Lifeand
of
sothatwecanmakethecombinedstringlooklike3words.
Combiningstringstogetherlikethisiscalled
concatenation.Let'
stryconcatenatingafewstringstogethernow!
sgiveitatry.Printtheconcatenatedstrings
Spam
"
eggs"
line3,justliketheexampleabove.
Makesureyouincludethespacesafter
and"
ExplicitStringConversion
Sometimesyouneedtocombineastringwithsomethingthatisn'
tastring.Inordertodothat,youhavetoconvertthenon-stringintoastring.
Ihave"
+str
(2)+"
coconuts!
Thiswillprint
Ihave2coconuts!
str()
methodconvertsnon-stringsintostrings.Intheaboveexample,youconvertthenumber
2intoastringandthenyouconcatenatethestringstogetherjustlikeinthepreviousexercise.
Nowtryityourself!
1.Runthecodeas-is.Yougetanerror!
2.Use
toturn
3.14
intoastring.Thenrunthecodeagain.
3.StringFormattingwith%,Part1
4.Whenyouwanttoprintavariablewithastring,thereisabettermethodthanconcatenatingstringstogether.
5.name="
Mike"
6.print"
Hello%s"
%(name)
7.The
%
operatorafterastringisusedtocombineastringwithvariables.The%
operatorwillreplacea
%s
inthestringwiththestringvariablethatcomesafterit.
8.Instructions
9.Takealookatthecodeintheeditor.Whatdoyouthinkit'
lldo?
ClickSave&
Submitwhenyouthinkyouknow.
StringFormattingwith%,Part2
Remember,weusedthe
operatortoreplacethe
placeholderswiththevariablesinparentheses.
Youneedthesamenumberof
%stermsinastringasthenumberofvariablesinparentheses:
The%swho%s%s!
%("
Knights"
"
say"
Ni"
#Thiswillprint"
TheKnightswhosayNi!
Nowit'
syourturn!
Wehave
___
inthecodetoshowyouwhatyouneedtochange!
1.Insidethestring,replacethethree___
with
%s.
2.Afterthestringbutbeforethethreevariables,replacethefinal
___witha
%.
3.Hit
Save&
SubmitCode.
4.Answerthequestionsintheconsoleastheypopup!
TypeinyouranswerandhitEnter.
AndNow,ForSomethingCompletelyFamiliar
Greatjob!
You'
velearnedalotinthisunit,including:
Threewaystocreatestrings
Alpha'
Bravo"
str(3)
len("
Charlie"
Delta"
.upper()
Echo"
Printingastring
Foxtrot"
Advancedprintingtechniques
g="
Golf"
h="
Hotel"
%s,%s"
%(g,h)
swrapitallup!
line3,createthevariablemy_string
andsetittoanystringyou'
dlike.
line4,
thelengthofmy_string.
3.On
line5,
the
.upper()
caseversionof
my_string.
ThedatetimeLibrary
Alotoftimesyouwanttokeeptrackofwhensomethinghappened.WecandosoinPythonusing
datetime.
Herewe'
lluse
datetime
toprintthedateandtimeinaniceformat.
GettingtheCurrentDateandTime
Wecanuseafunctioncalleddatetime.now()
toretrievethecurrentdateandtime.
fromdatetimeimportdatetime
printdatetime.now()
Thefirstlineimportsthe
datetimelibrarysothatwecanuseit.
Thesecondlinewillprintoutthecurrentdateandtime.
1.Createavariablecalled
now
andstoretheresultof
datetime.now()
init.
2.Then,
thevalueof
now.
fromdatetimeimportdatetime
now=datetime.now()
printnow
Extra
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