python programming by example
TRANSCRIPT
Copyright
PythonProgrammingbyExample
AgusKurniawan
1stEdition,2015
Copyright©2015AgusKurniawan
*CoverphotoiscredittoFajarRamadhany,Bataviasoft,http://bataviasoft.com/.
TableofContents
CopyrightPreface1.DevelopmentEnvironment1.1Installation1.2DevelopmentTools1.3PythonShell1.4RunningPythonApplicationfromFiles2.PythonProgrammingLanguage2.1CommonRule2.2Variables2.3Comment2.4ArithmeticOperations2.5MathematicalFunctions2.6IncrementandDecrement2.7GettingInputfromKeyboard2.8PythonOperators2.8.1ComparisonOperators2.8.2LogicalOperators2.8.3BitwiseOpeators2.8.4TestingAll2.9DecisionControl2.10Iteration-forandwhile2.11break,continueandpass2.12Date&Time
3.Lists,TuplesandDictionary3.1Lists3.2Tuples3.3Dictionary4.Functions4.1CreatingASimpleFunction4.2FunctionwithParametersandReturningValue4.3FunctionwithMultipleReturningValues4.4RecursionFunction4.5Testing5.PythonObjectOriented5.1CreatingClasses5.2ClassAttributes5.3Built-InClassAttributes5.4DestroyingClassObject5.5WritethemAll5.6Inheritance5.7OverridingMethods5.8OverloadingOperators6.PythonModulesandPackages6.1PythonModules6.2importStatement6.3from...import*Statement6.4InstallingExternalPythonPackage7.StringOperations7.1GettingStarted7.2ConcatenatingStrings
7.3StringToNumeric7.4NumerictoString7.5StringParser7.6CheckStringDataLength7.7CopyData7.8UpperandLowerCaseCharacters7.9TestingAProgram8.FileOperations8.1GettingStarted8.2WritingDataIntoAFile8.2.1CreatingaFile8.2.2WritingData8.2.3ClosingaFile8.2.4Demo8.3ReadingDataFromAFile9.ErrorHandling9.1ErrorHandling9.2CatchingAllErrors9.3RaisingExceptions9.4CustomException10.BuildingOwnPythonModule10.1CreatingSimpleModule10.2BuildingOwnPythonPackage11.Concurrency11.1GettingStarted11.2Threading11.3SynchronizingThreads
11.3.1MutexLocks11.3.2Event11.4Queue11.5Multiprocessing11.5.1Process11.5.2SynchronizingProcesses11.6ParallelTasks11.6.1ThreadPoolExecutor11.6.2ProcessPoolExecutor12.Encoding12.1GettingStarted12.2EncodingBase6412.3Hexadecimal12.4JSON12.5XML12.6CSV13.HashingandCryptography13.1GettingStarted13.2Hashing13.2.1HashingwithMD513.2.2HashingwithSHA1andSHA25613.2.3HashingwithKeyUsingHMAC13.2.4WritethemAll13.3Cryptography13.3.1SymmetricCryptography13.3.2AsymmetricCryptography14.DatabaseProgramming
14.1DatabaseforPython14.2MySQLDriverforPython14.3TestingConnection14.4CRUD(Create,Read,UpdateandDelete)Operations14.4.1CreateData14.4.2ReadData14.4.3UpdateData14.4.4DeleteData14.4.5WritethemAll15.SocketProgramming15.1SocketModule15.2HelloWorld15.3Client/ServerSocket15.3.1ServerSocket15.3.2ClientSocket15.3.3Testing16.PythonRegularExpressions16.1GettingStarted16.2Demo17.PythonGUIProgramming17.1GettingStarted17.2HelloPythonGUI17.3WorkingwithInputForm17.4WorkingwithCommonDialogs18.PythonUnitTesting18.1GettingStarted
18.2DemoSourceCodeContact
Preface
ThisbookisabriefreferencetothePythonprogramminglanguage.Itdescribesalltheelementsofthelanguageandillustratestheirusewithcodeexamples.
AgusKurniawan
Depok,November2015
1.DevelopmentEnvironment
1.1Installation
Pythonisawidelyusedgeneral-purpose,high-levelprogramminglanguage.InstallationofPythonapplicationiseasy.ForWindows,LinuxandMacPlatform,youdownloadsetupfilefromPythonwebsite,https://www.python.org/downloads/.Downloadandrunit.Followinstallationcommands.
Ifyou'reworkingonWindowsplatform,youcanrunsetupfileandfollowinstruction.
1.2DevelopmentTools
Basically,youcanuseanytexteditortowritePythoncode.Thefollowingisalistoftexteditor:
vimnanoPyCharm,https://www.jetbrains.com/pycharm/IntellijIDEA,https://www.jetbrains.com/idea/Sublimetext,http://www.sublimetext.com/VisualStudio,https://www.visualstudio.com
Inthisbook,IusePyCharmfordevelopmenttool.JetbrainsprovidescommunityandEducationlicensesforPyCharm.
1.3PythonShell
AfterinstalledPython,youobtainPythonshellonyourplatform.YoucantypethiscommandonTerminalorCommandPromptforWindowsPlatform.
python
ThisisPython2.x.Then,yougetPythonshell,showninFigurebelow.
IfyouinstalledPython3.x,youcanPythonshellbytypingthiscommand.
python3
ThisisPython3.x.Then,yougetPythonshell,showninFigurebelow.
OutputprogramonWindowsplatform.
AfteryoucallPythonshell,youobtaintheshell.Itshows>>>onTerminal.
Trytodothefollowingcommand.
>>>a=3
>>>b=5
>>>printa
>>>c=a*b
>>>printc
InPython3.x,printaisreplacedbyprint(a).
Thefollowingisasampleoutputofprogram.
AsampleoutputforWindowsplatform.
1.4RunningPythonApplicationfromFiles
Youcanrunyourprogrambywritingthemonafile.Forinstance,youcreateafile,calledch01_01.py,andwritethisscript.
print('helloworldfrompython')
Toruntheprogram,youcantypethiscommandonTerminal.
pythonch01_01.py
IfyouwanttoruntheprogramunderPython3.x,typethiscommandonTerminal.
python3ch01_01.py
Programoutput:
2.PythonProgrammingLanguage
ThischapterexplainsthebasicofPythonprogramminglanguage.
2.1CommonRule
Pythonlanguagedoesn'twrite";"attheendofsyntaxlikeyoudoitonC/C++languages.HereisthesyntaxruleofPython:
syntax_code1
syntax_code2
syntax_code3
2.2Variables
Inthissection,weexplorehowtodefineavariableandassignitsvalue.Bydefault,wedefinevariablesonPythonwithassigningvalue.
#declarevariables
num=2
area=58.7
city='Berlin'
country="Germany"
z=10+5j#complexnumber
Ifyouwanttodeclarevariableswithoutassigningvalues,youcansetitusingNone.
#declarevariablewithoutinitializingvalue
counter=None
index=None
Writethesecodesfortesting.
#declarevariables
num=2
area=58.7
city='Berlin'
country="Germany"
z=10+5j#complexnumber
#declarevariablewithoutinitializingvalue
counter=None
index=None
globalvar_global
var_global=10
print(num)
print(area)
print(city)
print(country)
print(z)
print(z.real)
print(z.imag)
print(var_global)
Savethesescriptsintoafile,calledch02_01.py.
NowyoucantypethisfileusingPython3.x.
$python3ch02_01.py
AsampleofprogramoutputcanseeninFigurebelow.
2.3Comment
Youmayexplainhowtoworkonyourcodewithwritingcomments.Todoit,youcanuse#and"""syntax.Hereissamplecode:
#thisacomment
"""
Thesearelongcomments
Thesearelongcomments
Thesearelongcomments
"""
2.4ArithmeticOperations
Pythonsupportsthesamefourbasicarithmeticoperationssuchasaddition,subtraction,multiplication,anddivision.Fortesting,createafile,calledch02_02.py.
Thefollowingisthecodeillustrationforbasicarithmeticinch02_02.py:
a=2.3
b=8
c=a+b
print(c)
c=a-b
print(c)
c=a*b
print(c)
c=a/b
print(c)
Saveandrunthisprogram.
python3ch02_02.py
Asampleofprogramoutput:
2.5MathematicalFunctions
Pythonprovidesmathlibrary.Ifyou’reworkingwithPython2.x,youcanreadthislibraryonhttps://docs.python.org/2/library/math.html.ForPython3.x,youcanreadmathlibraryonhttps://docs.python.org/3/library/math.html.
Createafile,calledch02_03.py.Writethefollowingcode.
frommathimport*
a=1.8
b=2.5
c=pow(a,b)
print(c)
c=sqrt(b)
print(c)
c=sin(a)
print(c)
print(pi)
Saveandruntheprogram.
python3ch02_03.py
Asampleofprogramoutput:
2.6IncrementandDecrement
Pythondoesn'thasspecialsyntaxforincrementanddecrement.Wecandefineincrementanddecrementasfollows.
++syntaxforincrement.a++canbedefinedasa=a+1--syntaxfordecrement.a--canbedefinedasa=a-1
Fortesting,createafile,calledch02_04.py.Writethefollowingscript.
a=4
print(a)
#increment
a=a+1
print(a)
a+=10
print(a)
#decrement
a=a-2
print(a)
a-=7
print(a)
Then,saveandruntheprogram.
python3ch02_04.py
Asampleofprogramoutput:
2.7GettingInputfromKeyboard
Togetinputfromkeyboard,wecanuseinput()forPython3.xandraw_input()forPython2.x.
Fortesting,createafile,calledch02_05.py,andwritethisscript.
#gettinginputfromkeyboardusinginput()
name=input('Whatisyourname?')
print('Hello,'+name+'!!')
user_id=input('WhatisyourID?')
print('Idis'+str(user_id))
#gettinginputfromkeyboardusingraw_input()
product=raw_input('Productname?')
print('Product='+product)
product_id=raw_input('ProductID?')
print('Productid='+str(product_id))
Saveandruntheprogram.
python3ch02_05.py
Asampleofprogramoutput:
2.8PythonOperators
Inthissection,welearnseveralPythonoperatorssuchascomparison,logicalandbitwiseoperators.
2.8.1ComparisonOperators
Youmaydetermineequalityordifferenceamongvariablesorvalues.Hereisthelistofcomparisonoperators:
==isequalto
!=isnotequal
>isgreaterthan
<islessthan
>=isgreaterthanorequalto
<=islessthanorequalto
2.8.2LogicalOperators
Theseoperatorscanbeusedtodeterminethelogicbetweenvariablesorvalues.
&&and
||or
!not
2.8.3BitwiseOpeators
BitwiseoperatorsinPythoncanbedefinedasfollows
&AND
|OR
^ExclusiveOR
>>Shiftright
<<Shiftleft
~Not(Inversion)
2.8.4TestingAll
Nowwetesthowtousecomparison,logicalandbitwiseoperatorsincode.Createafile,calledch02_06.py,andwritethesescripts.
#comparisonoperators
a=3
b=8
print(a==b)
print(a!=b)
print(a>b)
print(a>=b)
print(a<b)
print(a<=b)
#logicaloperators
print((a==b)and(a!=b))
print((a<=b)or(a>b))
print(not(a>=b))
#bitwiseoperators
#declarebinaryvariables
m=0b01010011
n=0b11111001
print(m)
print(n)
print(bin(m&n))
print(bin(m|n))
print(bin(m^n))
print(bin(~m))
print(bin(b<<3))
print(bin(b>>2))
Savethisfileandruntheprogram.
pythonch02_06.py
Asampleofprogramoutput:
2.9DecisionControl
Syntaxmodelforif..elsecanbeformulatedasbelow:
if(conditional):
#dosomething
else:
#dosomething
#########
if(conditional):
#dosomething
elif(conditional):
#dosomething
else:
#dosomething
Fortesting,createafile,calledch02_07.pyandwritethesescripts.
#if-else
a=10
b=30
print('demoif-elif-else')
if(a>10)or(b>10):
#dosomething
print('(a>10)or(b>10)')
elif(a!=5)and(b<=7):
#dosomething
print('(a!=5)and(b<=7)')
else:
#dosomething
print('else')
#nestedif
if(a==0)or(b>20):
ifb<50:
print('nested-if')
else:
print('else-nested-if')
else:
print('if-else')
Saveandruntheprogram.
python3ch02_07.py
Asampleofprogramoutput:
2.10Iteration-forandwhile
Iterationoperationisusefulwhenwedorepetitiveactivities.Thefollowingisforsyntax.
for(iteration):
#dosomething
while(conditional):
#dosomething
Fortesting,createafile,calledch02_08.pyandwritethesescripts.
#iteration-for
print('demo-iterationfor')
foriinrange(1,5):
print(i)
#nested-for
print('demo-nestedfor')
foriinrange(1,3):
forjinrange(5,10):
print(str(i)+'-'+str(j))
#iteration-while
print('demo-iterationwhile')
i=0
whilei<10:
print(i)
i+=1
Saveandruntheprogram
python3ch02_08.py
Asampleofprogramoutput:
2.11break,continueandpass
breakcanbeusedtostoponthecodepoint.Otherwise,continuecanbeusedtoskipsomescripts.Forillustration,wehavealooping.Theloopingwillbestoppedusingbreakifvalue=7.Anothersample,wecanskiptheiterationwithvalue=4usingcontinuesyntax.
Writethesescripts.
print('demo-break,continueandpass')
foriinrange(1,10):
ifi==4:
continue
ifi==7:
break
print(i)
pass#donothing
print('Thisistheendofprogram')
Savethesescriptsintoafile,calledch02_09.py.
Runtheprogram.
python3ch02_09.py
Asampleofprogramoutput:
2.12Date&Time
WecanworkwithDataandtimeinPythonusingtimelibrary.Wemustimportthislibrary.
Fortesting,writethesescripts.
importtime
#getcurrenttime
now=time.time()#utc
print(now)
#displayreadablecurrenttime
print(time.strftime("%b%d%Y%H:%M:%S",time.gmtime(now)))
print(time.timezone)
Savetheprogramintoafile,calledch02_10.py.
Runtheprogram.
python3ch02_10.py
Asampleofprogramoutput:
3.Lists,TuplesandDictionary
ThischapterexplainshowtoworkwithPythoncollection.
3.1Lists
Pythonprovidesalistforcollectionmanipulation.Wedefinealistas[].
Forillustration,weshowyouhowtousealistinPythonprogram.Theprogramimplements
declaringprintinggettingalistlengthaddinggettingaspecificitemfromalistsortingremoving
Writethesescripts.
#declarelists
print('----declarelists')
numbers=[]
a=[2,7,10,8]
cities=['Berlin','Seattle','Tokyo','Moscow']
b=[10,3,'Apple',6,'Strawberry']
c=range(1,10,2)
#print(lists
print('----print(lists')
print(a)
forcityincities:
print(city)
print(b)
print(c)
#getlengthoflists
print('----getlengthoflists')
print(len(a))
print(len(cities))
#additemintolist
print('----additem')
numbers.append(10)
numbers.append(5)
cities.append('London')
foriinnumbers:
print(i)
forcityincities:
print(city)
#getspecificitem
print('----getitem')
print(cities[2])
print(a[3])
#sorting
print(a.sort())
#edititem
print('----edititem')
cities[2]='newcity'
forcityincities:
print(city)
#removeitem
print('----removeitem')
a.remove(8)#byvalue
delcities[2]#byindex
forcityincities:
print(city)
Savethsesscriptsintoafile,calledch03_01.py.
Runtheprogram.
python3ch03_01.py
Asampleofprogramoutput:
3.2Tuples
Wecandefineatupleusing()inPython.Atuplecanbeappendanewitem.
Fortesting,webuildaprogramintoafile,calledch03_02.py.Writethesescripts.
#declaretuples
a=()
b=(3,5,7)
c=('Ford','BMW','Toyota')
d=(3,(5,'London'),12)
print(a)
print(b)
print(c)
print(d)
#getlengthoftuples
print(len(a))
print(len(b))
print(len(c))
print(len(d))
#getitem
print(b[2])
print(c[1])
#getindex
print(b.index(7))
print(c.index('Toyota'))
Saveandruntheprogram.
python3ch03_02.py
Asampleofprogramoutput:
Asampleofprogramoutput:
3.3Dictionary
Wecancreateanarraywithkey-valueordictionary.Pythonuses{}toimplementkey-valuearray.
Forillustration,wecreateaprogram,ch03_03.py.Writethesescripts.
#declare
a={}
b={2:'Sea',3:'River',8:'Mountain'}
c={2:{4:'abcd',5:'hjkl'},3:'vbnm'}
d=dict(name='elena',age=30,roles=('manager',
'consultant'))
print(a)
print(b)
print(c)
print(d)
#keysvalues
print(b.keys())
print(b.values())
print(b.items())
#additem
a.setdefault(2,'car')
a.setdefault(5,'train')
a.setdefault(7,'plane')
print(a)
#checkkey
print(3inb)
print(5inb)
Savethesescriptsandruntheprogram.
python3ch03_03.py
Asampleofprogramoutput:
4.Functions
ThischapterexplainshowtocreatefunctionusingPython.
4.1CreatingASimpleFunction
DeclaringfunctioninPythonhasformatasfollows.
deffoo():
print('foo()')
Youcancallthisfunctionfoo()onyourprogram.
4.2FunctionwithParametersandReturningValue
Sometimesyouwanttocreateafunctionwithaparameter.Youcanimplementitasfollows.
defcalculate(val_a,val_b):
val=val_a*val_b
returnval
4.3FunctionwithMultipleReturningValues
AfunctioncanreturnmultiplereturningvaluesinPython.Forinstance,wereturnthreevaluesinPythonfunction.Asamplecodecanbewrittenasbelow.
defperform(num):
d=num*5
returnd,d+5,d-2
4.4RecursionFunction
Recursionfunctionisafunctionwherethesolutiontoaproblemdependsonsolutionstosmallerinstancesofthesameproblem(asopposedtoiteration).Forillustration,wecanimplementFibonacciproblemusingPython.
ThefollowingisasamplecodeforFibonaccisolutioninPython.
deffibonacci(n):
ifn==0:
return0
elifn==1:
return1
else:
returnfibonacci(n-1)+fibonacci(n-2)
4.5Testing
Wecanwritecodeagainfromsection4.1to4.4andusetheminonch04_01.pyfile.
deffoo():
print('foo()')
defcalculate(val_a,val_b):
val=val_a*val_b
returnval
defperform(num):
d=num*5
returnd,d+5,d-2
deffibonacci(n):
ifn==0:
return0
elifn==1:
return1
else:
returnfibonacci(n-1)+fibonacci(n-2)
foo()
m=calculate(10,5)
print(m)
a,b,c=perform(5)
print(a)
print(b)
print(c)
res=fibonacci(10)
print(res)
Saveandruntheprogram.
python3ch04_01.py
Asampleofprogramoutput:
5.PythonObjectOriented
ThischapterweexplorehowtoworkwithObject-OrientedprogramminginPython.
5.1CreatingClasses
Object-orientedprogramming(OOP)isaprogramminglanguagemodelorganizedaroundobjects.Inthischapter,Idon’texplainindetailaboutOOP.IrecommendyoutoreadtextbooksrelatedtoOOP.
InOOP,aclassisatemplatedefinitionofthemethodsandvariablesinaparticularkindofobject.YoucandeclareaclassinPythonasfollows.
frommathimport*
classCity:
#classdata
city_count=0
city_id=0
###dosomething
Note:YoucanworkwithOOPusingPython3.x.
Afterdeclaredaclass,wecanuseit.
a=City()
b=City()
5.2ClassAttributes
Wecandeclareclassattributestostorethedataortocommunicatetootherobject.
Forinstance,wedeclarecity_countandcity_id.Wealsodefinemethods:move_to()anddistance().
classCity:
#classdata
city_count=0
city_id=0
#classattributes
defmove_to(self,x=0,y=0):
self.x+=x
self.y+=y
defdistance(self,other_city):
xi=pow(other_city.x-self.x,2)
yi=pow(other_city.y-self.y,2)
returnsqrt(xi+yi)
5.3Built-InClassAttributes
Basically,Pythonhasbuilt-inclassattributes,suchas__init__()isusedasclasscontructorand__str__()togenerateinformationabouttheclass.
classCity:
#classdata
city_count=0
city_id=0
#constructor
def__init__(self,name='',x=0,y=0):
self.name=name
self.x=x
self.y=y
City.city_count+=1#accessallCityclasses
self.city_id=City.city_count
def__str__(self):
return'City:'+self.name+',id='+
str(self.city_id)+',x='+str(self.x)+',y='+str(self.y)
5.4DestroyingClassObject
Inaclass,wecandefinedestructortoclearallusageresouces.Wecanuse__del__()inPythontodothat.
classCity:
def__del__(self):
#getclassname
class_name=self.__class__.__name__
print('class',class_name,'destroyed')
5.5WritethemAll
Let'strytowritethecodeinimplementation.Createafile,calledch05_01.py,andwritethesescripts.
frommathimport*
classCity:
#classdata
city_count=0
city_id=0
#constructor
def__init__(self,name='',x=0,y=0):
self.name=name
self.x=x
self.y=y
City.city_count+=1#accessallCityclasses
self.city_id=City.city_count
def__str__(self):
return'City:'+self.name+',id='+
str(self.city_id)+',x='+str(self.x)+',y='+str(self.y)
#classattributes
defmove_to(self,x=0,y=0):
self.x+=x
self.y+=y
defdistance(self,other_city):
xi=pow(other_city.x-self.x,2)
yi=pow(other_city.y-self.y,2)
returnsqrt(xi+yi)
def__del__(self):
#getclassname
class_name=self.__class__.__name__
print('class',class_name,'destroyed')
a=City('Hamburg',10,5)
b=City('Berlin',3,10)
print(a)
print(b)
print(City.city_count)
a.move_to(4,3)
b.move_to(7,12)
print(a)
print(b)
distance=a.distance(b)
print(distance)
Nowyoucanruntheprogram.
$python3ch05_01.py
Asampleofprogramoutput:
5.6Inheritance
Inheritance,encapsulation,abstraction,andpolymorphismarefourfundamentalconceptsofobject-orientedprogramming.Inthissection,weimplementinheritanceinPython.
Inheritanceenablesnewobjectstotakeonthepropertiesofexistingobjects.Aclassthatisusedasthebasisforinheritanceiscalledasuperclassorbaseclass.InPython,wecandeclareinheritanceasfollows.
importmath
classshape:
def__init__(self):
print('call__init__fromshapeclass')
deffoo(self):
print('callingfoo()fromshapeclass')
classcircle(shape):
def__init__(self,r):
print('call__init__fromcircleclass')
self.r=r
defcalculate_area_circle(self):
returnmath.pi*self.r*self.r
classrectangle(shape):
def__init__(self,l,w):
print('call__init__fromrectangleclass')
self.l=l
self.w=w
defcalculate_area_rectangle(self):
returnself.l*self.w
a=shape()
a.foo()
b=circle(5)
b.foo()
area=b.calculate_area_circle()
print('area:',area)
c=rectangle(2,3)
c.foo()
area=c.calculate_area_rectangle()
print('area:',area)
Savethesescriptsintoafile,calledch05_02.py.
Nowrunthisfile.
$python3ch05_02.py
Programoutput:
5.7OverridingMethods
WecanoverrideclassmethodsinOOP.Forinstance,wehaveaclass,shape,whichhascalculate_area().Weoverridethismethodfromderivedclassbyourownimplementation.
Writethesescriptsforsample.
importmath
classshape:
def__init__(self):
print('call__init__fromshapeclass')
defcalculate_area(self):
print('callingcalculate_area()fromshapeclass')
return0
classcircle(shape):
def__init__(self,r):
print('call__init__fromcircleclass')
self.r=r
defcalculate_area(self):
print('callingcalculate_area()fromcircleclass')
returnmath.pi*self.r*self.r
classrectangle(shape):
def__init__(self,l,w):
print('call__init__fromrectangleclass')
self.l=l
self.w=w
defcalculate_area(self):
print('callingcalculate_area()fromrectangle
class')
returnself.l*self.w
a=shape()
area=a.calculate_area()
print('area:',area)
b=circle(5)
area=b.calculate_area()
print('area:',area)
c=rectangle(2,3)
area=c.calculate_area()
print('area:',area)
Saveandruntheprogram.
$python3ch05_03.py
Asampleofprogramoutput:
5.8OverloadingOperators
WecandefineouroverloadingoperatorsinPythonusing__add__()forinstance.
Forcompleted,writethesescripts.
classPoint:
def__init__(self,x,y):
self.x=x
self.y=y
def__add__(self,other):
returnPoint(self.x+other.x,self.y+other.y)
def__sub__(self,other):
returnPoint(self.x-other.x,self.y-other.y)
def__mul__(self,other):
returnPoint(self.x*other.x,self.y*other.y)
def__str__(self):
return'x'+str(self.x)+',y:'+str(self.y)
a=Point(10,3)
b=Point(2,7)
c=Point(8,1)
print(a)
print(a+b)
print(c-b)
print(a*c)
Savethesescriptsintoafile,calledch05_04.py.
$python3ch05_04.py
Aprogramoutput:
6.PythonModulesandPackages
ThischapterexplainshowtoworkPythonmodulesandpackages.
6.1PythonModules
Inthischapter,welearnhowtoaccessPythonmodules.AlistofPythonpackagecanbefoundthiswebsite,https://pypi.python.org/pypi?%3Aaction=index.
6.2importStatement
YoucanaccessPythonmoduleusingimport.Trytowritethesescripts.
importmath
a=math.sin(0.3)
print(a)
b=math.sqrt(math.sin(0.5)*math.pow(5,3))
print(b)
Saveintoafile,calledch06_01.py.Runtheprogram.
$python3ch06_01.py
Programoutput:
6.3from...import*Statement
Onprevioussection,weuseimporttousePythonmodule.Touseit,youshouldmodulename.Youcanignoreitusingfrom...importstatement.
Writethesescripts.
frommathimport*
a=sin(0.3)
print(a)
b=sqrt(sin(0.5)*pow(5,3))
print(b)
Youcanseewedon'tneedtocallmath.sin().Wejustcallsin().
Saveandryntheprogram.
$python3ch06_02.py
Programoutput:
6.4InstallingExternalPythonPackage
IfyouwanttouseexternalPythonPackage,forinstance,Colorama,https://pypi.python.org/pypi/colorama.Wecaninstallituviapip.
TypethiscommandonTerminal.
pipinstallcolorama
IfyouwanttoinstallitforPython3.x,youshouldpip3.
pip3installcolorama
Nowlet'swritethedemo.
importcolorama
fromcoloramaimportFore,Back,Style
colorama.init()
message="helloworldfrompython"
print(message)
print(Fore.RED+message)
print(Fore.GREEN+message)
print(Fore.BLUE+message)
print(Fore.RED+Back.YELLOW+message+Style.RESET_ALL)
Saveintoafile,calledch06_03.py.
$python3ch06_03.py
Programoutput:
Programoutput:
7.StringOperations
ThischapterexplainshowtoworkwithStringoperationinPython.
7.1GettingStarted
Wealreadyusestringasdatatype,https://docs.python.org/3/library/string.html.Inthissection,weexploresomeoperationsinstring.
Thenextstepistoexplorehowtoworkwithstring.
7.2ConcatenatingStrings
Ifyouhavealistofstring,youcanconcatenateintoonestring.Youcanuse+operatorandformat()function.Hereisasamplecode
#Concatenating
print(str1+""+str2)
print(str1,str2)
print("%s%s"%(str1,str2))
print("{}{}".format(str1,str2))
7.3StringToNumeric
Sometimeyouwanttodomathoperationsbutinputdatahasstringtype.Toconvertstringtypeintonumeric,youcanuseint()forStringtoIntegerandfloat()forstringtoFloat.
Thefollowingisasamplecodetoimplementstringtonumericconversion.
#stringtonumeric
a="2"
b="6.8"
num1=int(a)
num2=float(b)
print(num1)
print(num2)
7.4NumerictoString
ItiseasytoconvertnumerictoStringtype,youcanusestr().Youcangetstringtypeautomatically.
#numerictostring
a=6
b=8.56
str1=str(a)
str2=str(b)
print(str1)
print(str2)
7.5StringParser
ThesimplesolutiontoparsingStringusessplit()withdelimiterparameter.Forexample,youhaveStringdatawith;delimiterandwanttoparseit.Hereissamplecode
#parsing
msg='Berlin;Amsterdam;London;Tokyo'
cities=msg.split(';')
forcityincities:
print(city)
7.6CheckStringDataLength
Youcanuselen()togetthelengthofdata.
msg='Helloworld,Python!'
#getalengthofstring
length=len(msg)
print(length)
7.7CopyData
YoumaycopysomecharactersfromStringdata.Todoit,youcanuse[start:end]syntax.Hereissyntaxformat:
msg='Helloworld,Python!'
#copy
print(msg[5:])
print(msg[:5])
print(msg[-3:])
print(msg[:-3])
print(msg[2:6])
print(msg[5:8])
7.8UpperandLowerCaseCharacters
Insomesituation,youwanttogetallstringdatainupperorlowercasecharacters.ThisfeatureisbuiltinStringobject.upper()functionisusedtomakewholestringinuppercaseandlower()isusedtomakewholestringinlowercase.
Thefollowingisasamplecodetogetupperandlowercasecharacters.
msg='Helloworld,Python!'
#upper&lower
print(msg.upper())
print(msg.lower())
7.9TestingAProgram
Wecanwriteourcodeinch17_01.pycompletelyasfollows.
str1="helloworld"
str2="python"
#Concatenating
print(str1+""+str2)
print(str1,str2)
print("%s%s"%(str1,str2))
print("{}{}".format(str1,str2))
#stringtonumeric
a="2"
b="6.8"
num1=int(a)
num2=float(b)
print(num1)
print(num2)
#numerictostring
a=6
b=8.56
str1=str(a)
str2=str(b)
print(str1)
print(str2)
#parsing
msg='Berlin;Amsterdam;London;Tokyo'
cities=msg.split(';')
forcityincities:
print(city)
#stringoperations
msg='Helloworld,Python!'
#upper&lower
print(msg.upper())
print(msg.lower())
#copy
print(msg[5:])
print(msg[:5])
print(msg[-3:])
print(msg[:-3])
print(msg[2:6])
print(msg[5:8])
#getalengthofstring
length=len(msg)
print(length)
Savethescriptandruntheprogram.
$python3ch07_01.py
Programoutput:
8.FileOperations
ThischapterexplainshowtoworkwithfileoperationsusingPython.
8.1GettingStarted
WecanworkwithI/Ofileusingiopackage,https://docs.python.org/3/library/io.html.
ThenextstepistobuildPythonapplicationtowriteandreadafile.
8.2WritingDataIntoAFile
Towriteandreadafile,wecanuseiopackage.Inthissection,wetrytowritedataintoafile.
8.2.1CreatingaFile
Wecancreateafileusingopen()functionwithparameter"w".Iffileisexist,itwillrecreateafile.
Ifyouwanttousetheexistingfile,youcanpass"a".Parameter"b"isusedforbinaryfile.
#createafile.
#Iffileisexisting,iterasesandcreatesanewone
f1=open('mydoc1','w')
#createafile.
#Iffileisexisting,itappends.Otherwise,itcreates
f2=open('mydoc2','a')
#binaryfiles
bf1=open('mydoc3','wb')
bf2=open('mydoc4','ab')
8.2.2WritingData
Writedataintoafile,wecanusewrite()function.
forindexinrange(1,12):
data=''
name='user'+str(index-1)
email='user'+str(index-1)+'@email.com'
ifindex==1:
data='{0:3s}{1:10s}{2:15s}\n'.format('No',
'Name','Email')
else:
data='{0:3s}{1:10s}{2:15s}\n'.format(str(index-
1),name,email)
f1.write(data)
f2.write(data)
bf1.write(data)
bf2.write(data)
8.2.3ClosingaFile
Iffileoperationsdone,youshouldcallclose()toclosefile.
f1.close()
f2.close()
bf1.close()
bf2.close()
8.2.4Demo
Let'swritethesescriptsfordemo.
#####################################
print('creatingfiles...')
#createafile.
#Iffileisexisting,iterasesandcreatesanewone
f1=open('mydoc1','w')
#createafile.
#Iffileisexisting,itappends.Otherwise,itcreates
f2=open('mydoc2','a')
#binaryfiles
bf1=open('mydoc3','wb')
bf2=open('mydoc4','ab')
#####################################
#writingdata
print('writingdataintofiles...')
forindexinrange(1,12):
data=''
name='user'+str(index-1)
email='user'+str(index-1)+'@email.com'
ifindex==1:
data='{0:3s}{1:10s}{2:15s}\n'.format('No',
'Name','Email')
else:
data='{0:3s}{1:10s}{2:15s}\n'.format(str(index-
1),name,email)
f1.write(data)
f2.write(data)
bf1.write(data)
bf2.write(data)
#####################################
#closeall
print('closefiles...')
f1.close()
f2.close()
bf1.close()
bf2.close()
Saveintoafile,calledch08_01.py.Then,runtheprogram.
$python3ch08_01.py
Programoutput:
Ifsuccess,youcanopenallfilestoseethecontent.
Asampleofcontentfrommydoc1filecanbeseeninFigurebelow.
Asampleofcontentfrommydoc3filecanbeseeninFigurebelow.
8.3ReadingDataFromAFile
Toreaddataperlinefromafile,weusereadline()function.
Writethesescriptsfordemo.
importsys
#####################################
print('openingfiles...')
f1=open('mydoc1','r')
f2=open('mydoc2','r')
bf1=open('mydoc3','rb')
bf2=open('mydoc4','rb')
#####################################
#readingdata
defreading_data(f):
whileTrue:
data=f.readline()
if(data=='')or(data==None):
break
sys.stdout.write(data)
print('formydoc1>>>>>')
reading_data(f1)
print('>>>>>>>>>>>>>>>')
print('formydoc2>>>>>')
reading_data(f2)
print('>>>>>>>>>>>>>>>')
print('formydoc3>>>>>')
reading_data(bf1)
print('>>>>>>>>>>>>>>>')
print('formydoc4>>>>>')
reading_data(bf1)
print('>>>>>>>>>>>>>>>')
#####################################
#closeall
print('closefiles...')
f1.close()
f2.close()
bf1.close()
bf2.close()
Saveintoafile,calledch08_02.py.Then,runtheprogram.
$python3ch08_02.py
Programoutput:
9.ErrorHandling
ThischapterexplainshowtohandleerrorsandexceptionsthatoccurinPythonapplication.
9.1ErrorHandling
Basicallywhenwewriteaprogramandoccurerroronrunning,Pythonwillcatchprogramerror.
Trytowritethesescriptsandrunthisprogram.
a=18
b=0
c=a/b
$python3ch09_01.py
Youshouldgeterror,showninFigurebelow.
Nowwecancatcherrorusingtry..except.Youcanreadhowtouseitonhttps://docs.python.org/3/tutorial/errors.html.
Writethesescripts.
Writethesescripts.
try:
a=18
b=0
c=a/b
print('result:',str(c))
exceptZeroDivisionErrorase:
print('Error:divisionbyzero')
print(e)
finally:
print('Done')
print('exitfromprogram')
Saveintoafile,ch09_02.py.Then,runthefile.
$python3ch09_02.py
Youcanseetheprogramcanhandletheerror.
9.2CatchingAllErrors
Onprevioussection,wecatcherrorfor"divisionbyerror".WecancatchallerrorsusingExceptionobject.Writethesescriptsfordemo.
try:
a=18
b=0
c=a/b
print('result:',str(c))
exceptExceptionase:
print(e)
finally:
print('Done')
print('exitfromprogram')
Saveintoafile,calledch09_03.py.Runtheprogram.
$python3ch09_03.py
Programoutput:
9.3RaisingExceptions
Wecanraiseerrorfromourprogramusingraise.
Fordemo,writethesescripts.
try:
a=18
b=0
c=a/b
print('result:',str(c))
exceptExceptionase:
raise
finally:
print('Done')
#thiscodeisnevercalled
print('exitfromprogram')
Saveintoafile,calledch09_04.py.Then,runtheprogram.
$python3ch09_04.py
Youshouldtheprogramraisetheerrorsowedon'twords"exitfromprogram".
9.4CustomException
WecanbuildownerrorwithimplementinginheritanceException.
Forinstance,wecreateaclass,MySimpleError,withinheritancefromException.
classMySimpleError(Exception):
def__init__(self,code,message):
self.code=code
self.message=message
def__str__(self):
returnrepr(str(self.code)+":"+self.message)
defsave_to_database(self):
print('savethiserrorintodatabase..')
#howtousecustomerror
try:
print('democustomerror')
print('raiseerrornow')
raiseMySimpleError(100,'Thisiscustomerror')
exceptMySimpleErrorase:
print(e)
e.save_to_database()
Savetheprogramintoafile,calledch09_05.py.
Runthisprogram.
$python3ch09_05.py
Programoutput:
10.BuildingOwnPythonModule
ThischapterexplainshowtobuildownPythonmodule.
10.1CreatingSimpleModule
Inthissection,wecreateasimplemodule.Wewillcallfunctionsfromexternalfile(*.py)inthesamepackage,mainpackage.
Firstly,createafile,simplemodule.py,andwritethesescripts.
defperform(a,b):
returna*2.5+b
defcalculate(a,b):
returna+b*5
YoualsocancreateaclassonPythonfile,forinstancesimpleadvmodule.pyandwritethesescripts.
frommathimport*
classCity:
#classdata
city_count=0
city_id=0
#constructor
def__init__(self,name='',x=0,y=0):
self.name=name
self.x=x
self.y=y
City.city_count+=1#accessallCityclasses
self.city_id=City.city_count
def__str__(self):
return'City:'+self.name+',id='+
str(self.city_id)+',x='+str(self.x)+',y='+str(self.y)
#classattributes
defmove_to(self,x=0,y=0):
self.x+=x
self.y+=y
defdistance(self,other_city):
xi=pow(other_city.x-self.x,2)
yi=pow(other_city.y-self.y,2)
returnsqrt(xi+yi)
def__del__(self):
#getclassname
class_name=self.__class__.__name__
print('class',class_name,'destroyed')
Nowyouaccessfunctionsfromsimplemodule.pyandsimpleadvmodule.pyfilesusingimportstatement.
Writethesescripts.
#accessourmodules
importsimplemodule
importsimpleadvmodule
#usesimplemodule
num1=simplemodule.perform(10,5)
print(num1)
num1=simplemodule.calculate(4,3)
print(num1)
#usesimpleadvmodule
city_a=simpleadvmodule.City('Hamburg',8,12)
city_b=simpleadvmodule.City('Berlin',5,7)
print(city_a)
print(city_b)
city_a.move_to(4,3)
city_b.move_to(7,12)
print(city_a)
print(city_b)
Saveintoafile,calledch10_01.py.Runtheprogram.
Saveintoafile,calledch10_01.py.Runtheprogram.
$python3ch10_01.py
Programoutput:
10.2BuildingOwnPythonPackage
Inpreviousprogram,wecreateamoduleinPythonpackage.Wecreateapackageandthenuseitinourprogram.
Youcancreateapackage,calledLearning,bycreatingfolder.InsideLearningfolder,youcreatefolders:AlgebraandArithmetic.
Thefollowingisourpackagestructure.
Nowweaddseveralfilesineachfolder
Learningfolder:__init__.py,common.py,Computer.pyandfoo.pyLearning/Algebrafolder:__init__.pyandadd.pyLearning/Arithmeticfolder:__init__.pyandcalculate.py
Thefollowingisscriptimplementationforeachfile.
common.py
defdo_something():
print('calldo_something()')
Computer.py
classComputer:
#constructor
def__init__(self,name=''):
self.name=name
def__str__(self):
return'Computer:'+self.name
defsay_hello(self):
print("I'mcomputer,called",
self.name)
foo.py
deffoo():
print('callfoo()')
__init__.pyfromLearningfolder.
fromcommonimportdo_something
fromComputerimportComputer
fromfooimportfoo
add.py
defadd(a,b):
returna+b
__init__.pyfromLearning/Algebrafolder.
fromLearning.Algebra.addimportadd
calculate.py
defcalculate(a,b):
returna+b*2.8
__init__.pyfromLearning/Arithmeticfolder.
fromLearning.Arithmetic.calculateimportcalculate
Nowwecanaccessourpackage.Createafile,calledch10_02.py,andwritethesescripts.
importsys
sys.path.append('./Learning')
importLearning
Learning.foo()
Learning.do_something()
a=Learning.Computer('myPC')
a.say_hello()
importLearning.Algebraasalgebra
b=algebra.add(10,5)
print(b)
importLearning.Arithmeticasarith
c=arith.calculate(5,8)
print(c)
Saveandruntheprogram.
$python3ch10_02.py
Programoutput:
11.Concurrency
ThischapterexplainshowtocreateconcurrencyinPython
11.1GettingStarted
WecanrunaprogramorafunctioninbackgroundusingPython.Inthischapter,weexploreseveralscenariostobuildconcurrencyapplication.InPython,youcanreadconcurrencyonthiswebsite,https://docs.python.org/3/library/concurrency.html.
11.2Threading
Basically,wecanimplementthreadingusingThreadwithpassingthefunction.Youcancallstart()torunathread.
importtime
importthreading
globalrunning
defperform():
globalrunning
counter=0
running=True
whilerunning:
print('counter:',str(counter))
time.sleep(2)
counter+=1
my_thread=threading.Thread(target=perform)
my_thread.setDaemon(True)
my_thread.start()
#python3
input("PressEntertostop...")
#python2
#raw_input("PressEntertostop...")
running=False
my_thread.join(2)
Toexitfromathread,wecancalljoin()withtimeoutvalue.
Saveintoafile,calledch11_01.py.
Runtheprogram.
$python3ch11_01.py
WhenThread.start()iscalled,itexecutesperform()function.
AsampleofprogramoutputcanbeseeninFigurebelow.
Threadobjectcanbeimplementedbyaderivedclassfromthreading.Thread.Forinstance,wecreateaclass,MyThread.Ithasinheritancefromthreading.Threadandimplementrun()function.
Writethesescripts.
importtime
importthreading
classMyThread(threading.Thread):
def__init__(self):
threading.Thread.__init__(self)
self.running=False
defrun(self):
counter=0
self.running=True
whileself.running:
print('counter:',str(counter))
time.sleep(2)
counter+=1
defstop(self):
print('stoppingthread...')
self.running=False
self.join(2)
my_thread=MyThread()
my_thread.setDaemon(True)
my_thread.start()
#python3
input("PressEntertostop...")
#python2
#raw_input("PressEntertostop...")
my_thread.stop()
Savethesescriptsintoafile,calledch11_02.py.Youcanseeourobject,my_thread,callstart()then,itcallrun().Wecallstop()functiontostopourthread.Basically,MyThreadwillcalljoin()whilecalledstop()function.
Nowyoucanruntheprogram.
$python3ch11_02.py
Asampleofprogramoutput:
11.3SynchronizingThreads
WecansynchronizeamongbackgroundcodesinPython.Inthissection,weusemutexlockandeventforthreadsynchronization.
Let'sstart.
11.3.1MutexLocks
Theideaisasimple.Whenweaccessaresource,wecallacquire().Ifdone,youcallrelease()fromLockobject.
Fortesting,wedefineasharedresource,suchasavariablecalledvalue.Thisvariablewillbeaccessbytwothreads.Onlyonethreadcanaccessthisvariable.
Ok,writethesescripts.
importtime
importthreading
classMyThread(threading.Thread):
def__init__(self,name,o_lock):
threading.Thread.__init__(self)
self.name=name
self.running=False
self.value_lock=o_lock
defrun(self):
globalvalue
self.running=True
whileself.running:
self.value_lock.acquire()
value+=1
print('value:',str(value),'from',self.name)
self.value_lock.release()
time.sleep(2)
defstop(self):
print('stopping',self.name)
self.running=False
self.join(2)
globalvalue
value=0
value_lock=threading.Lock()
my_thread1=MyThread('Thread1',value_lock)
my_thread1.setDaemon(True)
my_thread2=MyThread('Thread2',value_lock)
my_thread2.setDaemon(True)
my_thread1.start()
my_thread2.start()
#python3
input("PressEntertostop...")
#python2
#raw_input("PressEntertostop...")
my_thread1.stop()
my_thread2.stop()
Saveintoafile,calledch11_03.py.
Nowyoucanruntheprogram.
$python3ch11_03.py
Programoutput:
11.3.2Event
Anotheroptiontosynchthreading,wecanuseEventobject.Callwait()toblockoperation.Itmeanstheprogramcan'texecutecodesafterwait().Then,callset()toreleasetheblockingprocess.
Forillustration,wecreatethreeworkerthreads.Thesethreadswillperformsomethingaftercallingset()fromevent.Thisisusefulforinitializationstateprocess.
Writethesescripts.
importtime
importthreading
classWorker(threading.Thread):
def__init__(self,name,signal):
threading.Thread.__init__(self)
self.name=name
self.signal=signal
defrun(self):
print('waitingfrom',self.name)
self.signal.wait()
print('processingfrom',self.name)
time.sleep(2)
print('donefrom',self.name)
signal_event=threading.Event()
my_thread1=Worker('Thread1',signal_event)
my_thread1.setDaemon(True)
my_thread2=Worker('Thread2',signal_event)
my_thread2.setDaemon(True)
my_thread3=Worker('Thread3',signal_event)
my_thread3.setDaemon(True)
my_thread1.start()
my_thread2.start()
my_thread3.start()
#waitingfor10seconds
time.sleep(10)
#startprocess
print('Sendasignaltostartprocessing')
signal_event.set()
#python3
input("PressEntertostop...")
#python2
#raw_input("PressEntertostop...")
print('Doneall')
Saveintoafile,calledch11_04.py.Then,runtheprogram.
$python3ch11_04.py
Programoutput:
11.4Queue
Inthissection,welearnaboutQueueobjectfromPython,https://docs.python.org/3/library/queue.html.
Fortesting,weaddsomejobsintoQueue.Then,someworkerthreadswillpeakthejobandrunit.
Let'swritethesescripts.
importtime
importthreading
importqueue
classWorker(threading.Thread):
def__init__(self,name,q):
threading.Thread.__init__(self)
self.name=name
self.q=q
defrun(self):
whileTrue:
ifself.q.empty():
print('threadstopped')
break
job=self.q.get()
print('runjob',str(job),'from',self.name)
time.sleep(1)
self.q.task_done()
q=queue.Queue()
#generatejobs
print('populatejobs')
foriinrange(15):
q.put(i)
my_thread1=Worker('Thread1',q)
my_thread1.setDaemon(True)
my_thread2=Worker('Thread2',q)
my_thread2.setDaemon(True)
my_thread3=Worker('Thread3',q)
my_thread3.setDaemon(True)
my_thread1.start()
my_thread2.start()
my_thread3.start()
my_thread1.join()
my_thread2.join()
my_thread3.join()
#python3
input("PressEntertostop...")
#python2
#raw_input("PressEntertostop...")
print('Doneall')
Saveintoafile,calledch11_05.py.
Nowyoucanruntheprogram.
$python3ch11_05.py
Programoutput:
11.5Multiprocessing
WecanimplementconcurrencyinPythonusingmultiprocessing.Youcanreadtheinformationaboutthisonthissite,https://docs.python.org/3/library/multiprocessing.html.
11.5.1Process
WecanuseProcessobjecttoimplementmultiprocessinginPython.Forinstance,webuildacounterfromaprocess.
Writethesescripts.
importtime
importmultiprocessing
classMyProcess(multiprocessing.Process):
def__init__(self):
multiprocessing.Process.__init__(self)
self.running=False
defrun(self):
counter=0
self.running=True
whileself.running:
print('counter:',str(counter))
time.sleep(2)
counter+=1
defstop(self):
print('stoppingprocess...')
self.running=False
self.join(1)
my_process=MyProcess()
my_process.daemon=True
my_process.start()
#python3
input("PressEntertostop...")
#python2
#raw_input("PressEntertostop...")
my_process.stop()
Saveintoafile,calledch11_06.py,andrunit.
$python3ch11_06.py
Programoutput:
11.5.2SynchronizingProcesses
Wecansynchamongprocessesusingmultiprocessing.Value.Thisobjectimplementsynchronizingprocess.
Fortesting,wedefineasharedresourceviamultiprocessing.Value.Writethese
Fortesting,wedefineasharedresourceviamultiprocessing.Value.Writethesescripts.
importtime
importmultiprocessing
classMyProcess(multiprocessing.Process):
def__init__(self,name,shared_dt):
multiprocessing.Process.__init__(self)
self.name=name
self.running=False
self.shared_data=shared_dt
defrun(self):
self.running=True
whileself.running:
time.sleep(1)
withself.shared_data.get_lock():
self.shared_data.value+=1
print('value:',str(self.shared_data.value),
'from',self.name)
defstop(self):
print('stopping',self.name)
self.running=False
self.join(1)
shared_data=multiprocessing.Value('i',0,lock=True)
my_process1=MyProcess('Process1',shared_data)
my_process1.daemon=True
my_process2=MyProcess('Process2',shared_data)
my_process2.daemon=True
my_process1.start()
my_process2.start()
#python3
input("PressEntertostop...")
#python2
#raw_input("PressEntertostop...")
my_process1.stop()
my_process2.stop()
Savetheprogramintoafile,calledch11_07.py.
Nowyoucanruntheprogram.
$python3ch11_07.py
Programoutput:
11.6ParallelTasks
Thelastsectionistoimplementparalleltasksusingconcurrent.futures.Therearetwooptionstoimplementthis:ThreadPoolExecutorandProcessPoolExecutor.
11.6.1ThreadPoolExecutor
ThreadPoolExecutorusesthreadtodoparalleltasks.
Asampleofscriptforparalleltaskscanbewrittenthefollowingscript.
importqueue
importconcurrent.futures
importrandom
importtime
importdatetime
defperform(q,a,b,c):
rand_val=random.uniform(0,2)
res=a*b*10-c*2
time.sleep(rand_val)
q.put(res)
t1=datetime.datetime.now()
q=queue.Queue()
withconcurrent.futures.ThreadPoolExecutor(max_workers=3)as
executor:
foriinrange(1,15):
val_a=random.randint(1,10)
val_b=random.randint(1,10)
val_c=random.randint(1,10)
executor.submit(perform,q,val_a,val_b,val_c)
print('Printresults')
t2=datetime.datetime.now()
whilenotq.empty():
print(q.get())
t=t2-t1
print('totaltime:',str(t.total_seconds()),'seconds')
Saveintoafile,calledch11_08.py.
$python3ch11_08.py
Programoutput:
11.6.2ProcessPoolExecutor
ProcessPoolExecutorusesprocesstodoparalleltasks.
ProcessPoolExecutorusesprocesstodoparalleltasks.
Weimplementthesamescenariofromprevioussection.
importmultiprocessing
importconcurrent.futures
importrandom
importtime
importdatetime
defperform(q,a,b,c):
rand_val=random.uniform(0,2)
res=a*b*10-c*2
time.sleep(rand_val)
q.put(res)
t1=datetime.datetime.now()
m=multiprocessing.Manager()
q=m.Queue()
withconcurrent.futures.ProcessPoolExecutor(max_workers=3)as
executor:
foriinrange(1,15):
val_a=random.randint(1,10)
val_b=random.randint(1,10)
val_c=random.randint(1,10)
executor.submit(perform,q,val_a,val_b,val_c)
print('Printresults')
t2=datetime.datetime.now()
whilenotq.empty():
print(q.get())
t=t2-t1
print('totaltime:',str(t.total_seconds()),'seconds')
Savethesescriptsintoafile,calledch11_09.py.
$python3ch11_09.py
Programoutput:
12.Encoding
ThischapterexplainshowtoworkwithencodinginPython.
12.1GettingStarted
Inthischapter,weexploreencodingpackagefromPython.Thefollowingisalistofourdemotoillustratehowtouseencodingpackage:
Base64HexadecimalJSONXMLCSV
Let'sstarttoimplementtheseencoding.
12.2EncodingBase64
Thefirstdemoistoworkwithbase64encoding.Wecanusebase64package,https://docs.python.org/3/library/base64.html.Toencodestringtobase64string,wecanuseb64encode().Otherwise,wecandecodeitusingb64decode()function.
Fortesting,weencodeastringmessagetobase64.Then,wedecodebase64messagetooriginalmessage.Writethesescripts.
importbase64
plaintext='HelloworldfromPython'
s_bytes=plaintext.encode()
enc1=base64.b64encode(s_bytes)
dec1=base64.b64decode(enc1)
s_dec1=dec1.decode()
print('Plaintext:',plaintext)
print('Base64:',enc1)
print('Decoded:',s_dec1)
Saveintoafile,calledch12_01.py.
Nowyoucantesttobuildandruntheprogram.
$python3ch12_01.py
AsampleoutputcanbeseeninFigurebelow.
12.3Hexadecimal
TheseconddemoistoencodeanddecodestringtoHexadecimal.WecanuseencodeanddecodefromPython3.x,toimplementourdemo.
Createafile,calledch12_02.py.Thefollowingisimplementationofencoding/decodingHexadecimal.
fromcodecsimportencode,decode
#declarehexdata
num=0x64
print(num,'-->',chr(num))
num_s="\x64"
print(num_s)
#displayhexfromstringdata
s='HelloworldfromPython'
s_bytes=s.encode()
s_hex=encode(s_bytes,'hex')
s_decoded=decode(s_hex,'hex')
s_plaintext=s_decoded.decode()
print('plaintext:',s)
print('hex:',s_hex)
print('decoded:',s_plaintext)
#samplesfordisplayinghexdata
print('displayhexformat')
forcins:
print(c,'-->',encode(c.encode(),'hex'))
hex2=":".join("{:02x}".format(c)forcins_bytes)
print(hex2)
Savethiscode.Nowyoucanbuildandrunthisprogram.
$python3ch12_02.py
AsampleoutputcanbeseeninFigurebelow.
12.4JSON
ThethirddemoistoconstructandparseJSONdata.InPython,wecanusejsonpackage,https://docs.python.org/3/library/json.html.
Fordemo,createafile,calledch12_02.pyandwritethiscode.
importjson
importtime
#constructjson
data={
'name':'anna',
'sex':'woman',
'age':20,
'country':'germany'
}
blog={
'title':'myblog',
'created':time.time(),
'comments':[
{'name':'user1','comment':'thisiscomment1'},
{'name':'user2','comment':'thisiscomment2'},
{'name':'user3','comment':'thisiscomment3'}
]
}
#jsonobjecttojsonstring
json_data=json.dumps(data)
json_data2=json.dumps(blog)
print(json_data)
print(json_data2)
#decodejsonstringtojsonobject
#youdefinejsonstringorloadjsonstringfromfile
json_o1=json.loads(json_data)
json_o2=json.loads(json_data2)
#iterationjsonvalues
print('----json_o1---')
print(json_o1['name'])
print(json_o1['sex'])
print(json_o1['age'])
print(json_o1['country'])
print('----json_o2---')
print(json_o2['title'])
created_s=time.strftime("%b%d%Y%H:%M:%S",
time.gmtime(json_o2['created']))
print(created_s)
print('comments:')
forcommentinjson_o2['comments']:
print('---',comment['name'],':',comment['comment'])
Savethiscode.Nowyoucanbuildandrunthisprogram.
$python3ch12_03.py
AsampleoutputcanbeseeninFigurebelow.
12.5XML
ThefourthdemoistoreadandwriteXMLdata.Wecanusexmlpackage,https://docs.python.org/3/library/xml.html.Inthisdemo,weusexml.etree.ElementTreetoprocessXMLdata.Inthisdemo,wereadxmlfileandcreateanewxmlfile.
Firstly,wecreatexmlfilefortesting,calledproducts.xmlandwritethisdata.
<?xmlversion="1.0"?>
<products>
<productname="product1">
<code>1001</code>
<year>2015</year>
<modelcolor="red"category="food">12E</model>
</product>
<productname="product2">
<code>1002</code>
<year>2015</year>
<modelcolor="green"category="beverage">15C</model>
</product>
<productname="product3">
<code>1003</code>
<year>2015</year>
<modelcolor="blue"
category="electronics">19A</model>
</product>
</products>
NowwereadxmlfileanddisplayitintoTerminal.
importxml.etree.ElementTreeasEt
#loadxmlfileanditerate
xml_tree=Et.parse('products.xml')
products=xml_tree.getroot()
print(products.tag)
forproductinproducts:
print('',product.tag,'name=',product.get('name'))
forproduct_iteminproduct:
print('',product_item.tag,'=',product_item.text)
#findingspecificdata
print('----------')
forcodeinproducts.iter('code'):
print(code.text)
#constructxmlandsaveintoafile
print('constructxmlfile')
users=Et.Element('users')
foriinrange(1,5):
user=Et.SubElement(users,'user')
user.set('name',"User"+str(i))
user_item=Et.SubElement(user,'age')
user_item.text=str(i*3)
user_item2=Et.SubElement(user,'id')
user_item2.text="1203"+str(i)
print('writeintoxmlfile')
tree=Et.ElementTree(users)
tree.write("users.xml")
Savethiscodeintoafiile,calledch12_04.py.Nowyoucanrunthisprogram.
$python3ch12_04.py
Ifsuccess,youseeusers.xmlfileandyoushouldseethecontentasfollows.
<users>
<username="User1"><age>3</age><id>12031</id></user>
<username="User2"><age>6</age><id>12032</id></user>
<username="User3"><age>9</age><id>12033</id></user>
<username="User4"><age>12</age><id>12034</id></user>
</users>
AsampleofprogramoutputcanbeseeninFigurebelow.
12.6CSV
ThelastdemoistoreadandwritedataCSVwhichisacollectionofcomma-separateddata.WecanaccessCSVfileusingcsvpackage,https://docs.python.org/3/library/csv.html.Nowwebuildaprogramtoreadcsvfileandwritedataintocsvfile.
Fortesting,wecreateaCSVfile,customers.csv,withthefollowingcontent.
id,full_name,age,country
12,JamesButt,23,US
13,JosephineDarakjy,40,UK
14,ArtVenere,35,US
15,LennaPaprocki,34,DE
16,DonetteFoller,27,NL
Thefollowingisimplementationofreading/writingCSVfile.
importcsv
#readingcsvfile
withopen('customers.csv',newline='')ascsv_file:
customers=csv.reader(csv_file,delimiter=',')
forrowincustomers:
print(','.join(row))
csv_file.close()
print('------------')
#readingcsvfilewithhandlingheader
withopen('customers.csv')ascsv_file:
reader=csv.DictReader(csv_file)
forrowinreader:
print(row['id'],row['full_name'],row['age'],
row['country'])
csv_file.close()
#writingcsvfile
print('----------------')
print('writingcsvfile')
withopen('cities.csv','w')ascsv_file:
fieldnames=['id','name','country']
writer=csv.DictWriter(csv_file,fieldnames=fieldnames,
delimiter=';')
writer.writeheader()
foriinrange(1,10):
writer.writerow({'id':i,'name':"city"+str(i),
'country':"country"+str(i)})
csv_file.close()
print('done')
Note:YoucanchangeCSVfilepath.
Savethiscodeintoafile,calledch12_05.py.Nowyoucanrunthisprogram.
$python3ch12_05.py
AsampleoutputcanbeseeninFigurebelow.
Theprogramalsogeneratecities.csvfile.
Ifyouopencities.csv,yougetacontentofcitiesdatalikeacontentofcustomers.csvfile.
13.HashingandCryptography
ThischapterexplainshowtoworkwithhashingandcryptographyinPython.
13.1GettingStarted
Hashingisgeneratingavalueorvaluesfromastringoftextusingamathematicalfunction.Cryptographyisthepracticeandstudyoftechniquesforsecurecommunicationinthepresenceofthirdparties(calledadversaries),http://en.wikipedia.org/wiki/Cryptography.Inthischapter,Idon'texplainmathematicalhashingandCryptography.Youcanreadthosematerialsontextbooks.
Inthischapter,weexplorehowtoworkwithhashingimplementationusingPython.Thefollowingishashingalgorithmswhichweuseinthisbook:
MD5SHA1andSHA256HashingwithKey(HMAC)
ThenexttopicistoimplementCryptographyusingPython.WeexploresymmetricandasymmetricCryptography.
13.2Hashing
Basically,youcanexplorehowtoimplementhashingorhashfunctionusingPythonviahttps://docs.python.org/3/library/hashlib.html.Wealsouseopensourcelibrary,calledpycrypto,https://pypi.python.org/pypi/pycrypto.Weimplementbothinourcase.
Inthissection,weexploreseveralhashingalgorithms,forinstance,MD5,SHA1,SHA256andHMAC.
13.2.1HashingwithMD5
WecanuseMD5usingmd5package,https://docs.python.org/3/library/hashlib.html.Tocalculateahashvaluefromatext,wecancalldigest()function.
Forillustration,wedohashingaplaintext.
importhashlib
importbinascii
plaintext='helloworldfrompython'
#md5
md5=hashlib.md5()
md5.update(plaintext.encode())
hash_md5=md5.digest()
hex_hash_md5=md5.hexdigest()
print('hashmd5:',hash_md5)
print('hexhashmd5:',hex_hash_md5)
digest()isusedtocalculateahashvalue.hexdigest()istocalculatehexhash.
13.2.2HashingwithSHA1andSHA256
Theseconddemoistoimplementhashfunctionusingsha1andsha256.
Forillustration,writethesescriptforhashingSHA1andSHA256.
importhashlib
importbinascii
plaintext='helloworldfrompython'
#sha1
sha1=hashlib.sha1()
sha1.update(plaintext.encode())
hash_sha1=sha1.digest()
hex_hash_sha1=sha1.hexdigest()
print('hashsha1:',hash_sha1)
print('hexhashsha1:',hex_hash_sha1)
#sha256
sha256=hashlib.sha256()
sha256.update(plaintext.encode())
hash_sha256=sha256.digest()
hex_hash_sha256=sha256.hexdigest()
print('hashsha256:',hash_sha256)
print('hexhashsha256:',hex_hash_sha256)
13.2.3HashingwithKeyUsingHMAC
Akeyed-hashmessageauthenticationcode(HMAC)isaspecificconstructionforcalculatingamessageauthenticationcode(MAC)involvingacryptographichashfunctionincombinationwithasecretcryptographickey,http://en.wikipedia.org/wiki/Hash-based_message_authentication_code.InPython,weusepbkdf2_hmac()object.
Forillustration,wedohashingaplaintextwithkey.
importhashlib
importbinascii
plaintext='helloworldfrompython'
#hashwithkey
#hmac
key='p4ssw0rd'
hmac=hashlib.pbkdf2_hmac('sha256',key.encode(),
plaintext.encode(),100000)
hex_hash_hmac=binascii.hexlify(hmac)
print('hexhashhmac:',hex_hash_hmac)
13.2.4WritethemAll
Saveallcodeforourdemoonthissection.Writethiscodeandsaveintoafile,calledch13_01.py.
importhashlib
importbinascii
plaintext='helloworldfrompython'
#md5
md5=hashlib.md5()
md5.update(plaintext.encode())
hash_md5=md5.digest()
hex_hash_md5=md5.hexdigest()
print('hashmd5:',hash_md5)
print('hexhashmd5:',hex_hash_md5)
#sha1
sha1=hashlib.sha1()
sha1.update(plaintext.encode())
hash_sha1=sha1.digest()
hex_hash_sha1=sha1.hexdigest()
print('hashsha1:',hash_sha1)
print('hexhashsha1:',hex_hash_sha1)
#sha256
sha256=hashlib.sha256()
sha256.update(plaintext.encode())
hash_sha256=sha256.digest()
hex_hash_sha256=sha256.hexdigest()
print('hashsha256:',hash_sha256)
print('hexhashsha256:',hex_hash_sha256)
#hashwithkey
#hmac
key='p4ssw0rd'
hmac=hashlib.pbkdf2_hmac('sha256',key.encode(),
plaintext.encode(),100000)
hex_hash_hmac=binascii.hexlify(hmac)
print('hexhashhmac:',hex_hash_hmac)
Saveall.
Nowyoucantesttobuildandruntheprogram.
$python3ch13_01.py
AsampleoutputcanbeseeninFigurebelow.
13.3Cryptography
Inthissection,wefocusSymmetricandAsymmetricCryptography.InSymmetricCryptography,weusethesamekeytoencryptanddecrypt.Otherwise,AsymmetricCryptographyusesdifferentkeytoencryptanddecrypt.
Weusepycrypto,https://github.com/dlitz/pycrypto.Youcaninstallitviapip.AsampleofcommandtoinstallpycryptoforPython3.x.
$pip3installpycrypto
Forillustration,wehashaplaintextusingSHA256.Writethesescriptsandsaveintoafile,calledch13_02.py.
fromCrypto.HashimportSHA256
plaintext='helloworldfrompython'
sha256=SHA256.new()
sha256.update(plaintext.encode())
hash_sha256=sha256.digest()
hex_hash_sha256=sha256.hexdigest()
print('hashsha256:',hash_sha256)
print('hexhashsha256:',hex_hash_sha256)
Saveandruntheprogram.
$python3ch13_02.py
Programoutput:
13.3.1SymmetricCryptography
TherearemanyalgorithmstoimplementSymmetricCryptography.Inthissection,weuseAESalgorithm.TheAdvancedEncryptionStandard(AES)isaspecificationfortheencryptionofelectronicdataestablishedbytheU.S.NationalInstituteofStandardsandTechnology(NIST)in2001,http://en.wikipedia.org/wiki/Advanced_Encryption_Standard.
WecandosymmetricCryptographyusingpycryptobywritingthesescriptsintoafile,calledch13_03.py
fromCryptoimportRandom
fromCrypto.CipherimportAES
message='helloworldfrompython'
#AESkeymustbeeither16,24,or32bytes
long
key='p4ssw0rdp4ssw0rd'
print('message:',message)
#encrypt
iv_aes=Random.new().read(AES.block_size)
cipher_aes=AES.new(key.encode(),
AES.MODE_CFB,iv_aes)
encrypted_aes=
cipher_aes.encrypt(message.encode())
print('encryptedAES:',encrypted_aes)
#decrypted
dec_iv_aes=Random.new().read(AES.block_size)
dec_cipher_aes=AES.new(key.encode(),
AES.MODE_CFB,iv_aes)
decrypted_aes=
dec_cipher_aes.decrypt(encrypted_aes)
print('decryptedAES:',decrypted_aes)
Explanation:Thefollowingisthestepsforencryption
Defineakey.Itshouldbe16,24,or32keylength
CalculateIVvalueforAESusingRandom.read()withAES.block_sizeparameterInstantiateAESusingAES.new()withpassingkeyandIVvalueEncryptmessagebycallingencrypt()Theresultisarrayofbyte
Thefollowingisthestepsforencryption
Defineakey.Itshouldbe16,24,or32keylengthCalculateIVvalueforAESusingRandom.read()withAES.block_sizeparameterInstantiateAESusingAES.new()withpassingkeyandIVvalueDecryptcipherbycallingdecrypt()Theresultisbestringinarrayofbyte
Saveandruntheprogram.
$python3ch13_03.py
Programoutput:
13.3.2AsymmetricCryptography
ThecommonalgorithmtoimplementAsymmetricCryptographyisRSAwhichiswidelyusedforsecuredatatransmission.YoureadabriefdescriptioninWikipedia,http://en.wikipedia.org/wiki/RSA_(cryptosystem).
pycryptolibraryhaslibraryforRSAimplementation.Inthissection,wetrytoimplementRSAusingpycrypto.Thefollowingisourscenario:
GenerateRSAkeys(publicandprivatekeys)Savethesekeystotwofiles(publicandprivatekeyfiles)Forencryption,weusepublickeyfileFordecryption,weuseprivatekeyfile
WestorepublicandprivatekeysintoafileinPEMdataencoding.
TogeneratepublicandprivatekeysforRSA,weuseRSA.generate().Weextractprivateandpublickeyvalues.Then,savethemintofile.encrypt()anddecrypt()fromRSAKeyareusedtoencryptanddecrypt.
ThefollowingisimplementationforourRSAscenario.
fromCrypto.PublicKeyimportRSA
fromCryptoimportRandom
#generateprivateandpublickeys
#Then,savethemintofiles
print('generatingprivateandpublickeys...')
key=RSA.generate(2048)
f=open('my_rsa_private_key.pem','wb')
f.write(key.exportKey('PEM'))
f.close()
f=open('my_rsa_public_key.pem','wb')
f.write(key.publickey().exportKey('PEM'))
f.close()
print('done')
message='helloworldfrompython'
print('plaintext:',message)
#encryptdatausingpublickey
f=open('my_rsa_public_key.pem','r')
RSAkey=RSA.importKey(f.read())
f.close()
k=Random.new().read(8)
encrypted_msg=RSAkey.encrypt(message.encode(),k)
ciphertext=encrypted_msg[0]
print('encrypted:',ciphertext)
#decryptdatausingprivatekey
f=open('my_rsa_private_key.pem','r')
RSAkey=RSA.importKey(f.read())
f.close()
decrypted_msg=RSAkey.decrypt(ciphertext)
print('decrypted:',decrypted_msg.decode("utf-8"))
Savethesescriptsintoafile,calledch13_04.py.
Nowyoucanbuildandrunit.AsampleoutputcanbeseeninFigurebelow.
$python3ch13_04.py
Programoutput:
14.DatabaseProgramming
ThischapterexplainshowtobuilddatabaseapplicationusingPython.
14.1DatabaseforPython
Pythoncancommunicatewithdatabaseserverthroughdatabasedriver.WecanuseMySQLdriverfroPython.Inthischapter,IonlyfocusonMySQLscenario.
14.2MySQLDriverforPython
WeuseMySQLdriverforPython.Furtherinformationaboutthisdriver,pleasevisitonhttps://dev.mysql.com/downloads/connector/python/2.1.htmltodownloadandinstall.
YoualsocaninstallMySQLdriverforPythonviapip3(Python3.x).
$sudopip3install--allow-externalmysql-connector-python
mysql-connector-python
14.3TestingConnection
Inthissection,wetrytoconnectMySQLdatabase.Wecanuseconnect()frommysql.connectorobject.
importmysql.connector
print('connectingtomysqlserver...')
cnx=mysql.connector.connect(user='pyuser',
password='password123',
host='127.0.0.1',
database='pydb')
print('connected')
Youshouldpassusername,password,databaseserveranddatabasename.
14.4CRUD(Create,Read,UpdateandDelete)Operations
Inthissection,wetrytocreate,read,updateanddeletedataonMySQL.Firstly,wecreatedatabaseanditstable.
ThefollowingisourtableschemeonMySQL.
CREATEDATABASE`pydb`;
CREATETABLE`pydb`.`product`(
`idproduct`INTNOTNULLAUTO_INCREMENT,
`name`VARCHAR(30)NOTNULL,
`code`VARCHAR(10)NOTNULL,
`price`DECIMALNOTNULL,
`quantity`INTNULL,
`created`DATETIMENULL,
PRIMARYKEY(`idproduct`));
File:pydb.sqlRuntheseSQLscriptsintoyourMySQL.
14.4.1CreateData
Tocreatedata,weuseSQLstatement,INSERTINTO,whichpasstoexecute()function.
defcreate_data(conn):
cursor=conn.cursor()
print('insertingdata...')
foriinrange(1,5):
insert_product=("INSERTINTOproduct"
"(name,code,price,quantity,created)"
"VALUES(%s,%s,%s,%s,%s)")
data_product=("product"+str(i),"F029"+str(i),
i*0.21,i,datetime.now())
cursor.execute(insert_product,data_product)
product_id=cursor.lastrowid
print('insertedwithid=',product_id)
conn.commit()
cursor.close()
print('done')
Toobtainthelastinsertedid,wecanuselastrowidfromcursorobject.
14.4.2ReadData
Toreaddata,youcanuseSELECT...FROMqueryonyourPythonscripts.
defread_data(conn):
print('readingdata....')
selected_id=0
cursor=conn.cursor()
query="SELECTidproduct,name,code,price,quantity,
createdFROMproduct"
cursor.execute(query)
for(id,name,code,price,quantity,created)incursor:
print("{},{},{},{},{},{:%d%b%Y
%H:%M:%S}".format(
id,name,code,price,quantity,created))
ifselected_id<=0:
selected_id=id
cursor.close()
print('done')
returnselected_id
14.4.3UpdateData
Toupdatedata,youcanuseUPDATE....SETqueryonyourPythonscripts.
Toupdatedata,youcanuseUPDATE....SETqueryonyourPythonscripts.
defupdate_data(conn,id):
print('updatingdatawithidproduct=',id,'...')
cursor=conn.cursor()
query="UPDATEproductSETname=%s,code=%s,price=%s,
quantity=%s,created=%swhereidproduct=%s"
name='updated-name'
code='F9999'
price=0.99
quantity=10
created=datetime.now()
cursor.execute(query,(name,code,price,quantity,
created,id))
conn.commit()
cursor.close()
print('done')
Don'tforgettocallcommit()afterchangedthedata.
14.4.4DeleteData
Toupdatedata,youcanuseDELETEFROMqueryonyourPythonscripts.
defdelete_data(conn,id):
print('deletingdataonidproduct=',id,'...')
cursor=conn.cursor()
query="DELETEFROMproductwhereidproduct=%s"
cursor.execute(query,(id,))
conn.commit()
cursor.close()
print('done')
defdelete_all(conn):
print('deletingalldata....')
cursor=conn.cursor()
query="DELETEFROMproduct"
cursor.execute(query)
conn.commit()
cursor.close()
print('done')
Don'tforgettocallcommit()afterchangedthedata.
14.4.5WritethemAll
NowwecanwriteourscriptsaboutCRUD.
Writethesescripts.
importmysql.connector
fromdatetimeimportdatetime
defcreate_data(conn):
cursor=conn.cursor()
print('insertingdata...')
foriinrange(1,5):
insert_product=("INSERTINTOproduct"
"(name,code,price,quantity,created)"
"VALUES(%s,%s,%s,%s,%s)")
data_product=("product"+str(i),"F029"+str(i),
i*0.21,i,datetime.now())
cursor.execute(insert_product,data_product)
product_id=cursor.lastrowid
print('insertedwithid=',product_id)
conn.commit()
cursor.close()
print('done')
defread_data(conn):
print('readingdata....')
selected_id=0
cursor=conn.cursor()
query="SELECTidproduct,name,code,price,quantity,
createdFROMproduct"
cursor.execute(query)
for(id,name,code,price,quantity,created)incursor:
print("{},{},{},{},{},{:%d%b%Y
%H:%M:%S}".format(
id,name,code,price,quantity,created))
ifselected_id<=0:
selected_id=id
cursor.close()
print('done')
returnselected_id
defupdate_data(conn,id):
print('updatingdatawithidproduct=',id,'...')
cursor=conn.cursor()
query="UPDATEproductSETname=%s,code=%s,price=%s,
quantity=%s,created=%swhereidproduct=%s"
name='updated-name'
code='F9999'
price=0.99
quantity=10
created=datetime.now()
cursor.execute(query,(name,code,price,quantity,
created,id))
conn.commit()
cursor.close()
print('done')
defdelete_data(conn,id):
print('deletingdataonidproduct=',id,'...')
cursor=conn.cursor()
query="DELETEFROMproductwhereidproduct=%s"
cursor.execute(query,(id,))
conn.commit()
cursor.close()
print('done')
defdelete_all(conn):
print('deletingalldata....')
cursor=conn.cursor()
query="DELETEFROMproduct"
cursor.execute(query)
conn.commit()
cursor.close()
print('done')
print('connectingtomysqlserver...')
cnx=mysql.connector.connect(user='pyuser',
password='password123',
host='127.0.0.1',
database='pydb')
print('connected')
create_data(cnx)
selected_id=read_data(cnx)
update_data(cnx,selected_id)
read_data(cnx)
delete_data(cnx,selected_id)
read_data(cnx)
delete_all(cnx)
cnx.close()
print('closedconnection')
Savethisprogram.Then,youcanrunit.
$python3ch14_01.py
Programoutput:
15.SocketProgramming
ThischapterexplainshowtocreatesocketapplicationusingPython.
15.1SocketModule
Wecancreateapplicationbasedonsocketstackusingnetpackage.Youcanfinditforfurtherinformationonhttps://docs.python.org/3/library/socket.html.Irecommendyoutoreadsomebooksorwebsitesabouttheconceptofsocket.
15.2HelloWorld
Togetstarted,wecreateasimpleapplicationtogetalistofIPAddressinlocalcomputer.Wecanusegethostname()andgethostbyname()fromsocketobject.
Inthissection,wetrytogetlocalIPAddress.Firstly,wecancreateanewfile,calledch15_01.py.
importsocket
hostname=socket.gethostname()
ip=socket.gethostbyname(hostname)
print('hostname:',hostname)
print('ipaddress:',ip)
Savethiscode.Trytobuildandrunit.
$python3ch15_01.py
YoushouldseeyourlocalIPaddressfromyourcomputer.
15.3Client/ServerSocket
Nowwecreateaclient/serversocketusingPython.Wewillusesocketpackagetobuildclient/serverapplication.Forillustration,wecreateserverandclient.
15.3.1ServerSocket
Howtocreateserversocket?Itiseasy.Thefollowingisasimplealgorithmhowtobuildserversocket
createserversocketlistenincomingclientonthespecificportifclientconnected,serversendsdataandthendisconnectfromclient
Inthissection,webuildserverapp.Firstly,wecancreateanewfile,calledch15_02.py.Then,writethesescripts.
importsocket
#createtcp/ipsocket
server=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
host=socket.gethostname()
port=8091
#bindtotheport
server.bind((host,port))
#queueupto10clients
server.listen(10)
counter=0
print('waitingconnectionfromclients...')
whileTrue:
#establishaconnection
client,address=server.accept()
counter+=1
print('anewconnectionfrom',str(address))
message="welcome,yourid="+str(counter)+"\r\n"
client.send(message.encode('ascii'))
client.close()
Itusesport8091.Youcanchangeit.
15.3.2ClientSocket
Clientsocketisclientapplicationthatconnectstoserverandthensends/receivesdatafrom/toserver.WeshouldknowaboutIPaddressandportfromtargetserver.Wecancallconnect()toconnecttoserverandcallrecv()toreceiveincomingdata.
Inthissection,webuildclientapp.Firstly,wecancreateanewfile,calledch15_03.py.Then,writethesescripts.
importsocket
#createasocketobject
client=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
#ip/hostnameofserver
#changethisipaddress
host='192.168.0.10'
port=8091
print('connectingtoserver...')
client.connect((host,port))
print('connected')
recv=client.recv(1024)
print('received:',recv.decode('ascii'))
client.close()
print('closed')
YoushouldchangehostforIPaddressofserver.
15.3.3Testing
Nowwecantestourclient/serverapplication.Firstly,werunserverapplicationandthenexecuteclientapplication.
$python3ch15_02.py
Then,runclientapp.
$python3ch15_03.py
Hereissampleofprogramoutputforserverapplication:
Hereissampleofprogramoutputforclientapplication:
Thisisprogramoutputforthesecondclient.
16.PythonRegularExpressions
ThischapterexplainshowtoworkwithregularexpressionsinPython.
16.1GettingStarted
Regularexpressionsareapowerfullanguageformatchingtextpatterns.ThePython"re"moduleprovidesregularexpressionsupport.Thislibrarycanbereadonhttps://docs.python.org/3/library/re.html.
Youalsoobtainregularexpressionpatternsfromthissite,http://www.regxlib.com.
16.2Demo
Inthisdemo,wecreatethreescenario:
ValidatenumberdataSearchdataSearchandreplacedata
Wecanusematch()fromreobjecttovalidatethematchingofdefinedpattern.Tosearch,youcanusesearch()functionandusepub()toreplacedata.
Let'screateafile,calledch16_01.py,andwritethesescripts.
importre
#patternfornumbers
p=re.compile('^[0-9]+$')
print(p.match('19023'))
print(p.match('0000'))
print(p.match('12.789'))
print(p.match('12b23'))
#search
message='AnnaWilliam<[email protected]>'
match=re.search(r'[\w.-]+@[\w.-]+',message)
ifmatch:
print(match.group())
#searchandreplase
message='aaa:asasasw::sasas:::'
p=re.compile('(:|::|:::)')
resutl=p.sub('<>',message)
print(resutl)
Saveandruntheprogram.
$python3ch16_01.py
Programoutput:
17.PythonGUIProgramming
ThischapterexplainshowtoworkwithGUIinPython.
17.1GettingStarted
TherearemanymodulestoimplementGUIinPython.Inthischapter,welearntkintertobuildPythonGUI.Thislibrarycanbereadonthissite,https://docs.python.org/3/library/tk.html.ThislibraryhasinstalledonPython3.x.
Let'sstarttobuildPythonappwithtkinterlibrary.
17.2HelloPythonGUI
ThefirstdemoistobuildPythonGUIHelloWorld.WeuseTkobjecttobuildaform.
Writethesescripts.
importtkinterastk
dialog=tk.Tk()
dialog.title('SimpleForm')
dialog.mainloop()
Savethesescriptsintoafile,calledch17_01.py.Then,runtheprogram.
$python3ch17_01.py
Youshouldseeaformdialogwithtitle"SimpleForm".
17.3WorkingwithInputForm
NowwecanextendourTkobjectintoaninputform.Inthisscenario,weputtwoTextboxandabutton.Ifweclickabutton,wereadTextboxvalues.
Let'swritethesescriptsfordemo.
importtkinterastk
classInputForm(object):
def__init__(self):
self.root=tk.Tk()
self.root.title('InputForm')
self.num_a=''
self.num_b=''
self.frame=tk.Frame(self.root)
self.frame2=tk.Frame(self.root)
self.frame.pack()
self.frame2.pack()
self.initialization()
definitialization(self):
r=self.frame
k_a=tk.Label(r,text='NumberA')
k_a.grid(row=0,column=0)
self.e_a=tk.Entry(r,text='NumA')
self.e_a.grid(row=0,column=1)
self.e_a.focus_set()
k_b=tk.Label(r,text='NumberB')
k_b.grid(row=1,column=0)
self.e_b=tk.Entry(r,text='NumB')
self.e_b.grid(row=1,column=1)
self.e_b.focus_set()
r2=self.frame2
b=tk.Button(r2,text='Save',command=self.get_inputs)
b.pack(side='left')
defget_inputs(self):
self.num_a=self.e_a.get()
self.num_b=self.e_b.get()
self.root.destroy()
defget_values(self):
returnself.num_a,self.num_b
defwait_for_input(self):
self.root.mainloop()
dialog=InputForm()
dialog.wait_for_input()
num_a,num_b=dialog.get_values()
print('numa:',num_a)
print('numb:',num_b)
Savetheprogramintoafile,calledch17_02.py.
Runtheprogram.
$python3ch17_02.py
Youshouldseetheinputformdialog.
FillvaluesonTextbox.Then,clickSavebutton.
Afterclicked,theprogramwillreadinputvaluesandshowsthemonTerminal.
17.4WorkingwithCommonDialogs
tkinterlibraryalsoprovidescommondialogssuchMessagebox,filedialogandcolorchooser.
Forillustration,writethesescripts.
importtkinterastk
fromtkinterimportmessagebox,filedialog
fromtkinter.colorchooserimport*
#messagebox
print('demomessagebox')
messagebox.showinfo('Information','Thisismessage')
messagebox.showerror('Error','Thisiserrormessage')
messagebox.showwarning('Warning','Thisiswarningmessage')
#filedialog
dir=filedialog.askdirectory()
print('selecteddirectory:',dir)
file=filedialog.askopenfile(mode="r")
print('selectedfile:',file.name)
new_file_name=filedialog.asksaveasfilename()
print('saveasfile:',new_file_name)
#colorchooser
defget_color():
color=askcolor()
print('selectedcolor:',color)
dialog=tk.Tk()
tk.Button(dialog,text='SelectColor',
command=get_color).pack()
dialog.title('SimpleForm')
dialog.mainloop()
Savetheprogramintoafile,calledch17_03.py.Then,runtheprogram.
$python3ch17_03.py
Thefollowingisoutputformsforinformation,errorandwarning.
Outputformforselectingadirectory.
Outputformforselectingafile.
Outputformforsavingafile.
Outputformforselectingacolor.ClickSelectColorbuttontoshowColorsdialog.
ThefollowingisprogramoutputinTerminal.
18.PythonUnitTesting
ThischapterexplainshowtobuildunittestinginPython.
18.1GettingStarted
Unittestingisasoftwaredevelopmentprocessinwhichthesmallesttestablepartsofanapplication,calledunits,areindividuallyandindependentlyscrutinizedforproperoperation.Unittestingcanbeusedtominimizebugsontheapplication.
InPython,wecanuseunittestframework,https://docs.python.org/3/library/unittest.html.Pleasereadittoobtainmoreinformation.
18.2Demo
Fortesting,wecreateaclassanddounittestingforthisclass.
Writeafile,calledmathu.pyandwritethesescripts.
classMathu:
def__init__(self):
print('call__init__fromMathuclass')
defadd(self,num_a,num_b):
returnnum_a+num_b
defdiv(self,num_a,num_b):
try:
result=num_a/num_b
exceptZeroDivisionErrorase:
raisee
returnresult
defcheck_even(self,number):
returnnumber%2==0
Nowwewanttotestthisclassbythefollowingscenario:
testingadd()testindiv()testingcheck_even()testingforexceptionerror
Youcanwritethesescripts.
importunittest
importmathu
classTestMathu(unittest.TestCase):
deftest_add(self):
res=mathu.Mathu().add(5,8)
self.assertEqual(res,13)
deftest_div(self):
res=mathu.Mathu().div(10,8)
self.assertGreater(res,1)
deftest_check_even(self):
res=mathu.Mathu().check_even(4)
self.assertTrue(res)
deftest_error(self):
self.assertRaises(ZeroDivisionError,
lambda:mathu.Mathu().div(5,0))
if__name__=='__main__':
unittest.main()
Saveintoafile,calledch18_01.py.
Nowyoucanruntheprogram.
$python3ch18_01.py
Programoutput:
SourceCode
Youcandownloadsourcecodeonhttp://www.aguskurniawan.net/book/python2120151.zip.
