58 CHAPTER4. COMPUTINGWITHSTRINGS
(d)msg = ""
for s in string.split("secret","e"):
msg = msg + s
print msg
(e)msg = ""
for ch in "secret":
msg = msg + chr(ord(ch)+1)
print msg
- Show thestringthatwouldresultfromeachofthefollowingstringformattingoperations.If theoper-
ationis notlegal,explainwhy.
(a)"Looks like %s and%s for breakfast" % ("spam", "eggs")
(b)"There is %d %s %d %s" % (1,"spam", 4, "you")
(c)"Hello %s" % ("Suzie","Programmer")
(d)"%0.2f %0.2f" % (2.3,2.3468)
(e)"%7.5f %7.5f" % (2.3,2.3468)
(f)"Time left %02d:%05.2f"% (1, 37.374)
(g)"%3d" % ("14")
- Explainwhypublickey encryptionis moreusefulforsecuringcommunicationsontheInternetthan
private(shared)key encryption.
- A certainCSprofessorgives5-pointquizzesthataregradedonthescale5-A,4-B,3-C,2-D,1-F, 0-F.
Writea programthatacceptsa quizscoreasaninputandprintsoutthecorrespondinggrade.
- AcertainCSprofessorgives100-pointexamsthataregradedonthescale90–100:A,80–89:B,70–
79:C,60–69:D, 60:F. Writea programthatacceptsanexamscoreasinputandprintsoutthecorre-
spondinggrade.
- Anacronymis a wordformedbytakingthefirstlettersofthewordsina phraseandmakinga word
fromthem. Forexample,RAMis anacronymfor“randomaccessmemory.” Writea programthat
allowstheusertotypeina phraseandoutputstheacronymforthatphrase.Note:theacronymshould
bealluppercase,evenif thewordsinthephrasearenotcapitalized.
- Numerologistsclaimtobeabletodeterminea person’s charactertraitsbasedonthe“numericvalue”
ofa name.Thevalueofa nameis determinedbysummingupthevaluesofthelettersofthename
where’a’is 1,’b’is 2,’c’is 3 etc.,upto’z’being26.Forexample,thename“Zelle”wouldhave the
value 26 5 12 12 5 60 (whichhappenstobea veryauspiciousnumber, bytheway).Writea
programthatcalculatesthenumericvalueofa singlenameprovidedasinput.
- Expandyoursolutionto thepreviousproblemto allow thecalculationofa completenamesuchas“John
MarvinZelle”or“JohnJacobJingleheimerSmith.” Thetotalvalueis justthesumofthenumericvalue
foreachname.
- A Caesarcipheris a simplesubstitutioncipherbasedontheideaofshiftingeachletteroftheplaintext
messagea fixednumber(calledthekey)ofpositionsinthealphabet.Forexample,if thekey valueis
2,theword“Sourpuss”wouldbeencodedas“Uqwtrwuu.” Theoriginalmessagecanberecoveredby
“reencoding”it usingthenegative ofthekey.
Writea programthatcanencodeanddecodeCaesarciphers.Theinputtotheprogramwillbea string
ofplaintextandthevalueofthekey. Theoutputwillbeanencodedmessagewhereeachcharacterin
theoriginalmessageis replacedbyshiftingit key charactersintheASCIIcharacterset.Forexample,
ifchis a characterinthestringandkeyis theamounttoshift,thenthecharacterthatreplaceschcan
becalculatedas:chr(ord(ch)+ key).
