complete guide for python programming · complete guide for python programming quick & easy...

CompleteGuideForPythonProgramming

Quick&EasyGuideToLearnPython

By:JamesP.Long

ACKNOWLEDGMENTS

Formy students and friends,who all selflessly helpedme inwriting this book.Specialthanks to those who asked, insisted and assisted me in turning the seminars in [email protected]

TableofContentsIntroduction………………………………………10

PythonVersions…………………………………13

SomeCommonlyusedOperationsinPython………………………………………………15

PrintfFormatStrings…………………………20

Python Interactive - Using Python As A Calculator

………………………………………….22

PythonImplementations……………………26

PythonCompilers&NumericalAccelerators………………………………………31

LogicalAndPhysicalLineinPython……34

PythonIndentation……………………………37

PythonStandardLibrary……………………39

CreatingClasses&Objects…………………43

DocumentingYourCode……………………46

Python-ObjectOrientedProgramming49

PythonDatabase………………………………..55

Classes………………………………………………65

Methods……………………………………………71

Instances…………………………………………..75

PythonDatabaseAccess…………………….82

PythonNetworking………………………….108

SendingMailinPython…………………….117

Pythonmultithreading…………………….127

Pythonxmlprocessing…………………….148

PythonPrograms…………………………….166

PythonProgramtoAddTwoMatrices166

Python Program to Add Two Numbers………………………………………………………..168

Python Program to Calculate the Area of a Triangle…………………………………………..169

Python Program to Check Armstrong Number…………………………………………..171

Python Program to Check if a Number is Odd or Even…………………………………….173

PythonProgramtoCheckifaNumberisPositive,NegativeorZero…………………174

PythonProgramtoCheckifaStringisPalindromeorNot……………………………177

PythonProgramtoCheckLeapYear…179

Python Program to Check Prime Number………………………………………………………..181

Python Program toConvert Celsius To Fahrenheit………………………………………

183

PythonProgramtoConvertDecimalintoBinary,OctalandHexadecimal…………184

PythonProgramtoConvertDecimaltoBinaryUsingRecursion……………………186

Python Program to Convert Kilometers to Miles……………………………………………….187

Python Program to Count the Number of Each Vowel………………………………………189

PythonProgramtoDisplayCalendar..190

PythonProgramtoDisplayFibonacciSequenceUsingRecursion……………….192

PythonProgramToDisplayPowersof2UsingAnonymousFunction……………..194

PythonProgramtoDisplaythemultiplicationTable…………………………196

PythonProgramtoFindArmstrongNumberinanInterval………………………198

Python Program to Find ASCII Value of Character………………………………………..200

PythonProgramtoFindFactorialofNumberUsingRecursion…………………201

PythonProgramtoFindFactorsofNumber…………………………………………..203

PythonProgramtoFindHashofFile…205

PythonProgramtoFindHCForGCD…207

PythonProgramtoFindLCM……………209

PythonProgramtoFindNumbersDivisiblebyAnotherNumber……………211

PythonProgramtoFindSumofNaturalNumbersUsingRecursion………………..212

Python Program to Find the Factorial of a Number…………………………………………..214

PythonProgramtoFindtheLargestAmongThreeNumbers…………………….216

PythonProgramtoFindtheSize(Resolution)ofImage………………………218

Python Program to Find the Square Root………………………………………………………..220

PythonProgramtoFindtheSumofNaturalNumbers……………………………..221

Python Program to Generate a Random Number…………………………………………..222

Python Program to Illustrate Different Set Operations………………………………………223

PythonProgramtoMakeaSimpleCalculator………………………………………225

Python Program to Multiply Two Matrices………………………………………………………..229

PythonProgramtoPrintallPrimeNumbersinanInterval…………………….231

PythonProgramtoPrintHi,GoodMorning!…………………………………………234

Pythonprogram toPrint theFibonacci sequence…………………………………………235

Python Program to Remove Punctuations form a String……………………………………237

Python Program to Shuffle Deck of Cards………………………………………………………..239

PythonProgramtoSolveQuadraticEquation………………………………………….241

PythonProgramtoSortWordsinAlphabeticOrder……………………………..243

Python Program to Swap Two Variables………………………………………………………..245

Python Program to Transpose a Matrix………………………………………………………..246

Note………………………………………………..248

MoreFromAuthor…………………………..249

INTRODUCTION

Python is a wide used general, high-level programming language. Its style philosophyemphasizescodereadability,anditssyntaxallowsprogrammerstopreciseideasinfewerlinesofcodethatmightbepossibleinlanguageslikeC++orJava.Thelanguageprovidesconstructssupposedtomodifyclearprogramsonbothsmallandlargescales.

Python is a simple to learn, powerful programming language. Its economical high-levelinformation structures and an easy, but effective approach to object-orientedprogramming. Python’s elegant syntax and dynamic typing, in conjunction with itsinterpreted nature, make it a perfect language for scripting and speedy applicationdevelopmentinseveralareasonmostplatforms.Pythonisoneinallthoserarelanguageswhich might claim to both easy and powerful. You may end up pleasantly stunned toexaminehoweasy it’s to thinkabout theanswer to thematter insteadof thesyntaxandstructureofthelanguageyouareprogrammingin.

Inmyfirstbook“PythonProgrammingforBeginners”,Ihavediscussedallaboutwhatpythonprogramming language is?How to installpython toyour system?Differentdatatypes, function, parameters, class, objects used in python. I also have discussed aboutbasicpythonoperatorsandmodules.Notonlythese,youcanalsogetknowledgeonhowto call a function, exception handling function, python variables etc. That is all basicthingsthataremustknowwhenyoustartlearninganyprogramminglanguage.

NowinthisbookIamgoingtosharewithyouadvancedpythonprogrammingfunctionsandprogramstocreateinpython?Iassureyouthatifyougothroughthisbookseriously,theninfewdaysyouwillbecomeanexpertpythonprogrammer.Sowhatareyouwaitingfor?Startgoingthroughthebookandstartcreatingyourfirstprogramtoday.

PYTHONVERSIONS

Python has many versions but most commonly used are Python 2.0 and Python 3.0.Python2.0wasreleasedon16October2000,withmanymajornewfeaturesincludingafullgarbagecollectorandsupportforUnicode.Withthisreleasethedevelopmentprocesswas changed and becamemore transparent and community-backed. while Python 3.0 ,whichisalsoknownasPython3000orpy3k,isamajor,backwards-incompatiblerelease,andwasreleasedon3December2008.Manyofitsmajorfeatureshavebeenbackportedtothebackwards-compatiblePython2.6and2.7.Python2.xis legacy,Python3.xis thepresentandfutureofthelanguage.

http://www.amazon.com/dp/B00QR1KFVK/

Python3.0wasreleasedin2008.Thefinal2.xversion2.7releasecameoutinmid-2010,withastatementofextendedsupportforthisend-of-liferelease.The2.xbranchwillseeno newmajor releases after that. 3.x is under active development and has already seenover five years of stable releases, including version 3.3 in 2012 and 3.4 in 2014. Thismeans that all recent standard library improvements, for example, areonlyavailablebydefaultinPython3.x.

For those interested in using Python via aUSB thumb drive, youmay be interested inPortablePython.Thisisaself-containedPythonenvironmentthatyoucaneitherrunfromthethumbdriveorinstalltoyourcomputer.Thisisusefulforpeoplewhocan’tordon’twanttoinstallPythonbutwouldstillliketouseit.

SOMECOMMONLYUSEDOPERATIONSINPYTHON

UsingBlankLines:

A line containingonlywhitespace, possiblywith a comment, is called a blank line andPython ignores it completely. In an interactive interpreter session, you must enter anemptyphysicallinetoterminateamultilinestatement.

WaitingfortheUser:

The following line of the programdisplays the prompt, Press the enter key to exit andwaitsfortheusertopresstheEnterkey:

#!/usr/bin/pythonraw_input(“\n\nPresstheenterkeytoexit.”)

Here,“\n\n”arebeingusedtocreatetwonewlinesbeforedisplayingtheactualline.Oncetheuserpressesthekey,theprogramends.Thisisanicetricktokeepaconsolewindowopenuntiltheuserisdonewithanapplication.

MultipleStatementsonaSingleLine:

The semicolon (;) allows multiple statements on the single line given that neitherstatementstartsanewcodeblock.Hereisasamplesnipusingthesemicolon:

importsys;a=‘abc’;sys.stdout.write(a+‘\n’)

MultipleStatementGroupsasSuites:

In Python, a group of statements, which make a single code block are called suites.Compound or complex statements, such as if, while, def, and class, are those whichrequireaheaderlineandasuite.Headerlinesbeginthestatementandterminateswithacolon(:)andarefollowedbyoneormorelines,whichmakeupthesuite.Forexample:

ifexpression:suite

elifexpression:suite

else:suite

AccessingCommand-LineArguments:

Python provides a getopt module that helps you parse command-line options andarguments.

$pythontest.pyarg1arg2arg3

ThePythonsysmoduleprovidesaccesstoanycommand-lineargumentsviathesys.argv.Thisservestwopurpose:

•sys.argvisthelistofcommand-linearguments.

•len(sys.argv)isthenumberofcommand-linearguments.

ParsingCommand-‐LineArguments:Python provides a getopt module that helps you parse command-line options andarguments.Thismoduleprovidestwofunctionsandanexceptiontoenablecommand-lineargumentparsing.

getopt.getoptmethod:

Thismethodparsescommand-lineoptionsandparameterlist.Followingissimplesyntaxforthismethod:

getopt.getopt(args,options[,long_options])

Hereisthedetailoftheparameters:

•args:Thisistheargumentlisttobeparsed.

•options:Thisisthestringofoptionlettersthatthescriptwantstorecognize,withoptionsthatrequireanargumentshouldbefollowedbyacolon(:).

•long_options:Thisisoptionalparameterandifspecified,mustbealistofstringswiththenamesofthelongoptions,whichshouldbesupported.Longoptions,whichrequireanargumentshouldbefollowedbyanequalsign(‘=’).Toacceptonlylongoptions,optionsshouldbeanemptystring.

PRINTFFORMATSTRINGS

%d:integer

%5d:integerinafieldofwidth5chars

%-5d:integerinafieldofwidth5chars,butadjustedtotheleft

%05d:integerinafieldofwidth5chars,paddedwithzeroesfromtheleft

%g:floatvariablein%for%gnotation

%e:floatvariableinscientificnotation

%11.3e:floatvariableinscientificnotation,with3decimals,fieldofwidth11chars

%5.1f:floatvariableinfixeddecimalnotation,withonedecimal,fieldofwidth5chars

%.3f:floatvariableinfixeddecimalform,withthreedecimals,fieldofmin.width

%s:string

%-20s:stringinafieldofwidth20chars,andadjustedtotheleft

PYTHONINTERACTIVE-USINGPYTHONASACALCULATOR

Youcanusepythonasacalculator,asyoucanadd,subtract,multiplyanddividenumbersinpythonlanguage.

StartPython(orIDLE,thePythonIDE).

Apromptisshowingup:

>>>

Displayversion:

>>>help()

WelcometoPython2.7!Thisistheonlinehelputility.

…

help>

Helpcommands:

modules:availablemodules

keywords:listofreservedPythonkeywords

quit:leavehelp

Togethelponakeyword,justenteritsnameinhelp.

CommonOperatorsinPython

ExampleForSimpleCalculationsinPython

>>>3.14*5

15.700000000000001

TakecareinPython2.xifyoudividetwonumbers:

Isn’tthisstrange:

>>>35/6

5

Obviouslytheresultiswrong!

But:

>>>35.0/6

5.833333333333333

>>>35/6.0

5.833333333333333

In the first example, 35 and 6 are interpreted as integer numbers, so integer division isusedandtheresultisaninteger.

This uncanny behavior has been abolished in Python 3, where 35/6 gives5.833333333333333.

In Python 2.x, use floating point numbers (like 3.14, 3.0 etc….) to force floating pointdivision!

PYTHONIMPLEMENTATIONS

An“implementation”ofPythonprovidessupportfortheexecutionofprogramswhicharewritten in the Python Programming language, is represented by the CPython referenceimplementation.Thereseveralimplementationtorunpythonprograms.Let’shavealookatthem:

CPythonVariants

These are implementations which are based on the CPython runtime core, but withextendedbehaviororfeaturesinsomeaspects.

CrossTwineLinker-AcombinationofCPythonandanadd-onlibraryofferingimprovedperformance.

Stackless Python - CPython with an emphasis on concurrency using tasklets andchannels.

Unladen-Swallow-anoptimizationbranchofCPython,intendedtobefullycompatibleandsignificantlyfaster.

WPython-are-implementationofCPythonusing“wordcode”insteadofbytecode.

OtherImplementationsThesearere-implementationsofthePythonlanguagethatdonotdependontheCPythonruntime core. Many of them reuse the standard library implementation. The onlyimplementationsthatareknowntobecompatiblewithagivenversionofthelanguageareIronPython,JythonandPyPy.

The following implementations are comprehensive or even complete, that you can runtypicalprogramswiththemalready:

Brython-AwaytorunPythoninthebrowserthroughtranslationtoJavaScript.

CLPython-PythoninCommonLisp.

HotPy -Avirtualmachine forPython supportingbytecodeoptimizationand translationusingtypeinformationgatheredatrun-time.

IronPython - Python in C# for the Common Language Runtime (CLR/.NET) and theFePyproject’sIronPythonCommunityEdition(IPCE).

Jython-PythoninJavafortheJavaplatform.

Pyjs-APythontoJavaScriptcompilerplusWeb/GUIframework.

PyMite-Pythonforembeddeddevices.

PyPy-PythoninPython,targetingseveralenvironments.

Pyvm - A Python-related virtual machine and software suite providing a nearly self-contained“userspace”system.

RapydScript-APython-likelanguagethatcompilestoJavaScript.

SNAPpy-AsubsetofthePythonlanguagethathasbeenoptimizedforuseinlow-powerembeddeddevices.

Tinypy-AminimalistimplementationofPythonin64Kofcode.

TentativeImplementationsThefollowing implementationsareapparentworks inprogress; theymaynotbeable toruntypicalprograms:

Berp-animplementationofPython3inHaskell,providinganinteractiveenvironmentaswellasacompiler.

Phpython-aPythoninterpreterwritteninPHP.

Pyjaco-aPythontoJavaScriptcompilersimilartoPyjsbutlighterweight.

Pystacho-is,likeSkulpt,PythoninJavaScript.

Pyvm2.py-aCPythonbytecodeinterpreterwritteninPython.

Skulpt-PythoninJavaScript.

Typhon-aRubinius-basedimplementationofPython.

PythonCompilers&NumericalAccelerators

Compilers

ThesecompilersusuallyimplementsomethingclosetoPython,havealookatthem:

2c-python-astaticPython-to-Ccompiler,apparentlytranslatingCPythonbytecodetoC.

Compyler-anattemptto“transliteratethebytecodeintox86assemblies”.

Cython - a widely used optimizing Python-to-C compiler, CPython extension modulegenerator, and wrapper language for binding external libraries. Interacts with CPythonruntimeandsupportsembeddingCPythoninstand-alonebinaries.

GCCPythonFront-End-anin-progressefforttocompilePythoncodewithintheGCCinfrastructure.

Nuitka - a Python-to-C++ compiler using libpython at run-time, attempting somecompile-timeandrun-timeoptimizations.InteractswithCPythonruntime.

Pyc - performs static analysis in order to compile Python programs, uses similartechniquestoShedSkin.

ShedSkin-aPython-to-C++compiler,restrictedtoanimplicitlystaticallytypedsubsetofthelanguageforwhichitcanautomaticallyinferefficienttypesthroughwholeprogramanalysis.

UnPython-aPythontoCcompilerusingtypeannotations.

NumericalAccelerators

Copperhead - purely functional data-parallel Python compiles to multi-core and GPUbackends.

Numba-NumPy-awareoptimizingruntimecompilerforPython.

Parakeet-runtimecompilerforanumericalsubsetofPython.

LogicalAndPhysicalLineinPython

Aphysical lineiswhatyouseewhenyouwritetheprograminpython.Alogical lineiswhatPythonseesasasinglestatement.Pythonimplicitlyassumesthateachphysicallinecorrespondstoalogicalline.Forexample,youwanttowrite-‘helloworld’-ifthiswasonalinebyitself,thenthisalsocorrespondstoaphysicalline.

Ifyouwanttospecifymorethanonelogicallineonasinglephysicalline,thenyouhaveto explicitly specify this using a semicolon (;) which indicates the end of a logicalline/statement.

Forexample:

i=12

printi

iseffectivelysameas

i=12;

printi;

whichisalsosameas

i=12;printi;

andsameas

i=12;printi

Ifyouhavealonglineofcode,youcanbreakitintomultiplephysicallinesbyusingthebackslash.Thisisreferredtoasexplicitlinejoining:

s=‘Thisisapythonbook.\

Thiscontinuesthebook.’

prints

Output:

Thisisapythonbook.Thiscontinuesthebook.

Similarly,

print\

i

isthesameas

printi

Sometimes,thereisanimplicitassumptionwhereyoudon’tneedtouseabackslash.Thisis the casewhere the logical line has starting parentheses, starting square brackets or astartingcurlybracesbutnotanendingone.Thisiscalledimplicitlinejoining.Youcanseethisinactionwhenwewriteprogramsusinglistsinlaterchapters.

PYTHONINDENTATION

Whitespace is very important inPython.Thewhitespace at the beginning of the line iscalled indentation. Leading whitespace at the beginning of the logical line is used todeterminetheindentationlevelofthelogicalline,whichinturnisusedtodeterminethegroupingofstatements.Eachsetofstatementsiscalledablock.

Forexample:

i=5

#Errorbelow!Noticeasinglespaceatthestartoftheline

print‘Valueis‘,i

print‘Irepeat,thevalueis‘,i

Whenyourunthis,yougeterror:

File“whitespace.py”,line5

print‘Valueis‘,i

^

IndentationError:unexpectedindent

Noticethatthereisasinglespaceatthebeginningofthesecondline.Theerrorindicatedby Python tells us that the syntax of the program is invalid i.e. the program was notproperly written. Use four spaces for indentation. This is the official Python language

recommendation.Good editorswill automaticallydo this for you.Make sureyouuse aconsistent number of spaces for indentation; otherwise your programwill show errors.Pythonalwaysuseindentationforblocksandwillneverusebraces.

PYTHONSTANDARDLIBRARY

ThePython StandardLibrary contains a huge number of usefulmodules and is part ofeverystandardPythoninstallation.wewillexploresomeofthecommonlyusedmodulesinthislibrary.YoucanfindcompletedetailsforallofthemodulesinthePythonStandardLibrary in the ‘Library Reference’ section of the documentation that comes with yourPythoninstallation.

sysmodule

The sys module contains system-specific functionality. We have already seen that thesys.argv listcontains thecommand-linearguments.Forexample,youwant tocheck theversionofthePythonsoftwarebeingused;thesysmodulegivesusthatinformation.

$python

>>>importsys

>>>sys.version_info

sys.version_info(major=2,minor=7,micro=6,releaselevel=‘final’,serial=0)

>>>sys.version_info.major==2

True

loggingmodule

Whatifyouwantedtohavesomedebuggingmessagesorimportantmessagestobestoredsomewheresothatyoucancheckwhetheryourprogramhasbeenrunningasyouwouldexpectit?Howdoyou“storesomewhere”thesemessages?Thiscanbeachievedusingtheloggingmodule.

Saveasstdlib_logging.py:

importos,platform,logging

ifplatform.platform().startswith(‘Windows’):

logging_file=os.path.join(os.getenv(‘HOMEDRIVE’),

os.getenv(‘HOMEPATH’),

‘test.log’)

else:

logging_file=os.path.join(os.getenv(‘HOME’),‘test.log’)

print“Loggingto”,logging_file

logging.basicConfig(

level=logging.DEBUG,

format=’%(asctime)s:%(levelname)s:%(message)s’,

filename=logging_file,

filemode=‘w’,

)

logging.debug(“Startoftheprogram”)

logging.info(“Doingsomething”)

logging.warning(“Dyingnow”)

Output:

$pythonstdlib_logging.py

Loggingto/Users/swa/test.log

$cat/Users/swa/test.log

2014-03-2909:27:36,660:DEBUG:Startoftheprogram

2014-03-2909:27:36,660:INFO:Doingsomething

2014-03-2909:27:36,660:WARNING:Dyingnow

CREATINGCLASSES&OBJECTS

Pythonisanobject-orientedlanguageandbecauseofthiscreatingandusingclassesandobjectsarequiteeasy.

OverviewofOOPTerminologyClass: A user-defined prototype for an object that defines a set of attributes thatcharacterize any object of the class. The attributes are data members and methods,accessedviadotnotation.

Classvariable:Avariable that is sharedbyall instancesof a class.Classvariablesaredefinedwithinaclassbutoutsideanyoftheclass’smethods.Classvariablesaren’tusedasfrequentlyasinstancevariablesare.

Datamember:Aclassvariableorinstancevariablethatholdsdataassociatedwithaclass

anditsobjects.

Function overloading: The assignment of more than one behavior to a particularfunction.Theoperationperformedvariesbythetypesofobjectsinvolved.

Instance variable: A variable that is defined inside amethod and belongs only to thecurrentinstanceofaclass.

Inheritance:Thetransferofthecharacteristicsofaclasstootherclassesthatarederivedfromit.

Instance:Anindividualobjectofacertainclass.Anobject‘obj’ thatbelongs toaclassCircle,forexample,isaninstanceoftheclassCircle.

Instantiation:Thecreationofaninstanceofaclass.

Method:Aspecialkindoffunctionthatisdefinedinaclassdefinition.

Object: A unique instance of a data structure that’s defined by its class. An objectcomprisesbothdatamembersandmethods.

Operator overloading: The assignment of more than one function to a particularoperator.

DOCUMENTINGYOURCODE

To document a Python object, docstring is used. A docstring is simply a triple-quotedsentence which gives a brief summary of the object. The object can be anything afunction,amethod,aclass,etc.

Anythingwritten in the triplequotes is the function’sdocstring,whichdocumentswhatthefunctiondoes.Adocstring,isthefirstthingthatisdefinedinafunction.Docstringisavailable at runtime as an attribute of the function.The docstring of a script should beusableasits‘usage’message,printedwhenthescriptisinvokedwithincorrectormissingarguments.Thedocstringisaphraseendinginaperiod.Itdescribesthefunction’seffectasacommand.

In docstring for a module classes, exceptions and functions that are exported by themodule are listed. The docstring for a function or method summarize its behavior anddocumentitsarguments,returnvalue(s),sideeffectsandexceptionsraised.Thedocstringfor a class summarize its behavior and list the public methods and instance variables.Individualmethodsshouldbedocumentedbytheirowndocstring.

You can add a docstring to a function, class, ormodule by adding a string as the firstindentedstatement.

Forexample:

#!/usr/bin/envpython

#docstringexample.py

“““Exampleofusingdocumentationstrings.”””

classKnight:

”””

Anexampleclass.

Callspamtogetbacon.

”””

defspam(eggs=“bacon”):

“““Printstheargumentgiven.”””

print(eggs)

PYTHON-OBJECTORIENTEDPROGRAMMING

LearningPythonClassesInOOP (object-oriented programming), the class is themost basic component.OOP isverypowerful toolandmanyPython librariesandAPIsusesclasses,andsoyoushouldknowwhatclassesare?Howtheywork?Andhowtocreatethem?OnethingtorememberaboutPythonandOOPisthatit’snotmandatorytouseobjectsinyourcode.

NowthequestionishowareClassesBetter?Let’s take an example, suppose you want to calculate the velocity of a car in a two-dimensionalplaneusingfunctions.Andyounowwanttomakeanewprogramtocalculatethevelocityofanairplaneinthreedimensions,andthenyou’llhavetorewritethemanyofthefunctionstomakethemworkfortheverticaldimension,especiallytomaptheobjectina3-Dspace. In thatcaseclassesareused.Classes letyoudefineanobjectonce,andthenyoucanreuseitmultipletimes.Youneedtogiveitabasefunction,andthenbuilduponthatmethodtoredefineitasnecessary.

ImprovingYourClassStandingSomeconceptsofclassesaregivenbelow.Havealookatthem:

-Classeshaveadefinitenamespace,justlikemodules.Tryingtocallaclassmethodfromadifferentclasswillgiveyouanerrorunlessyouqualifyit,e.g.spamClass.eggMethod().

- Classes supportmultiple copies. Classes have two different objects: class objects andinstanceobjects.Classobjectsareusedtogivethedefaultbehaviorandareusedtocreateinstance objects. Instance objects are the objects that actually do the work in yourprogram.Youcanhaveasmanyinstanceobjectsofthesameclassobjectasyouneed.

-Eachinstanceobjecthasitsownnamespacebutalsoinheritsfromthebaseclassobject.Thismeanseachinstancehasthesamedefaultnamespacecomponentsastheclassobject,butadditionallyeachinstancecanmakenewnamespaceobjectsjustforitself.

-Classescandefineobjectsthatrespondtothesameoperationsasbuilt-intypes.So,classobjects can be sliced, indexed, con- catenated, etc. just like strings, lists, and otherstandardPythontypes.ThisisbecauseeverythinginPythonisactuallyaclassobject;wearen’tactuallydoinganythingnewwithclasses,we’rejustlearninghowtobetterusetheinherentnatureofthePythonlanguage.

SoWhatDoesaClassLookLike?Seehereyouclasslooklikeinpython:

Definingaclass

>>>classItem:#defineaclassobject

…defsetName(self,value):#defineclassmethods

…self.name=value#selfidentifiesaparticularinstance

…defdisplay(self):

…printself.name#printthedataforaparticularinstance

Creatingclassinstances>>>x=Item()

>>>y=Item()

>>>z=Item()

Addingdatatoinstances>>>x.setName(“Hello,ThisisPythonbook.”)

>>>y.setName(“Iamaquicklearner.”)

>>>z.setName(“Itisworthbuyingthisbook.”)

Displayinginstancedata>>>x.display()

Hello,ThisisPythonbook.

>>>y.display()

Iamaquicklearner.

>>>z.display()

Itisworthbuyingthisbook.

PYTHONDATABASES

Inpythonwhenyouusewebapplicationsorcustomer-orientedprograms,Databasesareveryimportant.Normalfiles,suchastextfiles,areeasytocreateanduse;Pythonhasthe

toolsbuilt-inand itdoesn’t takemuch toworkwith files.Databasesareusedwhenyouworkon discrete “structures”, such as customer list that has phone numbers, addresses,pastorders,etc.databaseisusedtostorealumpofdataanditallowstheuserordevelopertopullthenecessaryinformation,withoutregardtohowthedataisstored.Also,databasescanbeusedtoretrievedatarandomly,ratherthansequentially.

HowtoUseaDatabase

Adatabaseisacollectionofdata,whichisplacedintoanarbitrarystructuredformat.Mostcommonlyuseddatabaseisarelationaldatabase.Indatabasetablesareusedtostorethedata and relationships can be defined between different tables. SQL (Structured QueryLanguage)isthelanguagewhichisusedtoworkwithmostDatabases.SQLprovidesthecommands to query a database and retrieve ormanipulate the information. SQL is alsousedtoinputinformationintoadatabase.

WorkingWithADatabase

Database consists of one or more tables, just like a spreadsheet. The vertical columnscompriseofdifferentfieldsorcategories;theyareanalogoustothefieldsyoufilloutinaform.Thehorizontalrowsareindividualrecords;eachrowisonecompleterecordentry.Hereisanexamplerepresentingacustomer’slist.

USINGSQLTOQUERYADATABASE

Here,Indexfieldistheonethatprovidesauniquevaluetoeveryrecord;it’softencalledtheprimarykeyfield.Theprimarykeyisaspecialobjectfordatabases;simplyidentifyingwhichfield is theprimarykeywillautomatically increment that fieldasnewentriesaremade, therebyensuringauniquedataobject foreasy identification.Theother fieldsaresimplycreatedbasedontheinformationthatyouwanttoincludeinthedatabase.

Nowifyouwanttomakeorderentrydatabase,andwanttolinkthattotheabovecustomerlist,soitshouldbelike:

Thistableiscalled“Orders_table”.Thistableshowsvariousordersmadebyeachpersoninthecustomer table.EachentryhasauniquekeyandisrelatedtoCustomers_tablebytheCustomer_IDfield,whichistheIndexvalueforeachcustomer.

PythonandSQLite

PythonhasaSQLite,alight-weightSQLlibrary.SQLiteisbasicallywritteninC,soitisveryquickandeasytounderstand.Itcreatesthedatabaseinasinglefile,soimplementingadatabasebecomes fairlysimple;youdon’tneed toworryabout the issuesofhavingadatabase spread across a server.SQLite is good for prototypingyour applicationbeforeyouthrowinafull-blowndatabase.Bythisyoucaneasilyknowhowyourprogramworksand any problems aremost likelywith the database implementation. It’s also good forsmallprogramsthatdon’tneedacompletedatabasepackagewithitsassociatedoverhead.

CreatinganSQLitedatabase

SQLite isbuilt intoPython, so it caneasilybe imported toanyother library.Onceyouimportit,youhavetomakeaconnectiontoit;soastocreatethedatabasefile.CursorinSQLiteperformsmostofthefunctions;youwillbedoingwiththedatabase.

importsqlite3#SQLitev3istheversioncurrentlyincludedwithPython

connection=sqlite3.connect(“Hand_tools.database”)#The.databaseextensionisoptional

cursor=connection.cursor()

#Alternativedatabasecreatedonlyinmemory

#mem_conn=sqlite3.connect(“:memory:”)

#cursor=mem_conn.cursor()

cursor.execute(“““CREATETABLETools(idINTEGERPRIMARYKEY,nameTEXT,sizeTEXT,priceINTEGER)”””)

foritemin((None,“Book”,“Small”,15),#Theendcommaisrequiredtoseparate

tuple items (None,“Purse”,“Medium”,35),(None,“Pen”,“Large”,55),(None,”Hat”,“Small”,25),(None,“Handbag”,“Small”,25),(None,“Socks”,“Small”,10),(None,“Comb”,“Large”,60),):cursor.execute (“INSERT INTO Tools VALUES(?,?,?,?)”,item)

connection.commit()#Writedatatodatabase

cursor.close()#Closedatabase

Inthisexamplequestionmarks(?)areusedtoinsertitemsintothetable.Theyareusedtoprevent a SQL injection attack, where a SQL command is passed to the database as alegitimatevalue.Thequestionmarksactasasubstitutionvalue.

RetrievingdatafromSQLite

ToretrievethedatafromaSQLitedatabase,youjustusetheSQLcommandsthattellthedatabasewhatinformationyouwantandhowyouwantitformatted.

Example:

cursor.execute(“SELECTname,size,priceFROMTools”)

toolsTuple=cursor.fetchall()

fortupleintoolsTuple:name,size,price=tuple#unpackthetuples

item=(“%s,%s,%d”%(name,size,price))

printitem

Output:

Book,Small,15

Purse,Medium,35

Pen,Large,55

Hat,Small,25

Handbag,Small,25

Socks,Small,10

Comb,Large,60

Book,Small,15

Purse,Medium,35

Pen,Large,55

Hat,Small,25

Handbag,Small,25

Socks,Small,10

Comb,Large,60

Dealingwithexistingdatabases

SQLite will try to recreate the database file every time you run the program. If thedatabasefilealreadyexists,youwillgetan“OperationalError”exceptionstatingthatthefilealreadyexists.Theeasiestwaytodealwiththisistosimplycatchtheexceptionandignoreit.

cursor.execute(“CREATETABLEFoo(idINTEGERPRIMARYKEY,nameTEXT)”)

exceptsqlite3.OperationalError:pass

Thiswillallowyoutorunyourdatabaseprogrammultipletimeswithouthavingtodeletethedatabasefileaftereveryrun.

CLASSES

Classisadatastructurethatisusedinpythontodefineobjects,whichholdsdatavaluesand behavioral characteristics. Classes are the entities, which are the programs of anabstraction for aproblem,and instancesare realizationsof suchobjects.The termmostlikely originates from using classes to identify and categorize biological families ofspecies to which specific creatures belong and can be derived into similar yet distinctsubclasses.Manyofthesefeaturesapplytotheconceptofclassesinprogramming.

InPython, classdeclarations are similar to the functiondeclarations, a header linewithappropriatekeywordfollowedbyasuiteasitsdefinition,asindicatedbelow:

deffunctionName(args):

‘functiondocumentationstring’

function_suite

class

ClassName:

‘classdocumentationstring’

class_suite

Classinpythonholdsmultipledataitems,anditcanalsosupportitsownsetoffunctions,which are calledmethods.Youmaybe askingwhat other advantages classeshaveoverstandardcontainertypessuchaslistsanddictionaries.

CreatingClassesPython classes are created using the class keyword. In the simple form of classdeclarations,thenameoftheclassimmediatelyfollowsthekeyword:

classClassName:

‘classdocumentationstring’

class_suite

class_suite consists of all the component statements, defining class members, dataattributes,andfunctions.Classesaregenerallydefinedatthetop-levelofamodulesothatinstancesofaclasscanbecreatedanywhereinapieceofsourcecodewheretheclassisdefined.

ClassDeclarationvs.DefinitionIn python there is no difference in declaring and defining classes because they occursimultaneously.Thedefinitionfollowsthedeclarationandthedocumentationstring.

ClassAttributesAclassattributeisafunctionalelement,whichbelongstoanotherobjectandisaccessedviadotted-attributenotation.InPython,complexnumbershavedataattributeswhilelistsanddictionarieshavefunctionalattributes.Whenyouaccessattribute,youcanalsoaccessanobjectthatmayhaveattributesofitsown.

Forexample:

-sys.stdout.write(‘abc’)

-printmyModule.myClass.__doc__

-myList.extend(map(upper,open(‘x’).readlines()))

Classattributesarelinkedtotheclassesinwhichtheyaredefined,andinstanceobjectsarethemost commonly used objects in OOP. Instance data attributes are the primary dataattributes thatareused.Classdataattributesareusefulonlywhena“static”data typeisrequired,whichdoesnotrequireanyinstances.

ClassDataAttributesDataattributesarethevariablesoftheclasswhicharedefinedbytheprogrammer.Theycan be used like any other variable when the class is created and can be updated bymethodswithin theclass.These typesof attributes arebetterknown toprogrammersasstaticmembers,classvariables,orstaticdata.Theyrepresentdatathatistiedtotheclassobjecttheybelongtoandareindependentofanyclassinstances.

Exampleofusingclassdataattributes(abc):

>>>classC:

…abc=100

>>>printC.abc

0

>>>C.abc=C.abc+1

>>>printC.abc

Output:

101

METHODS

In the example given below,MyFirstMethodmethod of theMyTeam class is simply afunctionwhichisdefinedaspartofaclassdefinition.ThismeansthatMyMethodappliesonlytoobjectsorinstancesofMyTeamtype.

ForExample:

>>>classMyTeam:

defMyFirstMethod(self):

pass

>>>myInstance=MyTeam()

>>>myInstance.MyFirstMethod()

AnycalltoMyFirstMethodbyitselfasafunctionfails:

>>>MyFirstMethod()

Traceback(innermostlast):

File“<stdin>”,line1,in?

MyFirstMethod()

NameError:MyFirstMethod

Here in the above example, NameError exception is raised because there is no suchfunction in the global namespace. Here MyFirstMethod is a method, meaning that itbelongs to the class and is not a name in theglobal namespace. IfMyFirstMethodwasdefinedasafunctionatthetop-level,thenourcallwouldhavesucceeded.Weshowyoubelowthatevencallingthemethodwiththeclassobjectfails.

>>>MyTeam.MyFirstMethod()

Traceback(innermostlast):

File“<stdin>”,line1,in?

MyTeam.MyFirstMethod()

TypeError:unboundmethodmustbecalledwithclassinstance1stargument

ThisTypeErrorexceptionmayseemperplexingatfirstbecauseyouknowthatthemethodisanattributeoftheclassandsoarewonderingwhythereisafailure.

StaticMethodsPythondoesnot support staticmethods, and functionswhichareassociatedonlywithaclassandnotwithanyparticularinstances.Theyareeitherfunction,whichhelpmanagestaticclassdataorareglobalfunctionswhichhavesomesortoffunctionalityrelatedtotheclass, inwhich they are defined.Because python does not support staticmethods, so astandardglobalfunctionisrequired.

INSTANCES

Classisadatastructuredefinitiontype,whileaninstanceisadeclarationofavariableofthattype.Oryoucansaythatinstancesareclasseswhicharebroughttolife.Instancesarethe objects which are used primarily during execution, and all instances are of type“instance.”

CreatingInstancesbyInvokingClassObjectMost languages provide a new keyword to create an instance of a class. The python’sapproachismuchsimpler.Onceaclasshasbeendefinedinpython,creatinganinstanceisnomoredifficult.Usinginstantiationofthefunctionoperator.

ForExample:

>>>classMyTeam:#defineclass

…pass

>>>myInstance=MyTeam()#instantiateclass

>>>type(MyTeam)#classisofclasstype

<type‘class’>

>>>type(myInstance)#instanceisofinstancetype

<type‘instance’>

Usingtheterm“type”inPythonisdifferentfromtheinstancebeingofthetypeofclassitwascreatedfrom.Anobject’stypedictatesthebehavioralpropertiesofsuchobjectsinthePython system, and these types are a subset of all types,whichPython supports.User-defined “types” such as classes are categorized in the samemanner. Classes share thesametype,buthavedifferentIDsandvalues.Allclassesaredefinedwiththesamesyntax,so they can be instantiated, and all have the same core properties. Classes are uniqueobjects,whicharedifferonlyindefinition,hencetheyareallthesame“type”inPython.

InstanceAttributesInstanceshaveonlydataattributesandthesearesimplythedatavalueswhichyouwanttobeassociatedwithaparticularinstanceofanyclass.Theyareaccessibleviathefamiliardotted-attributenotation.Thesevaluesareindependentofanyotherinstanceortheclassitwas instantiated from. If any instance is deallocated, then its attributes are alsodeallocated.

“Instantiating”InstanceAttributesInstanceattributescanbesetanytimeafteraninstancehasbeencreated,inanypieceofcodethathasaccesstotheinstance.However,oneofthekeyplaceswheresuchattributesaresetisintheconstructor,__init__().

ConstructorFirstPlacetoSetInstanceAttributesTheconstructoristheearliestplacethatinstanceattributescanbesetbecause__init__()is the first method called after instance objects have been created. There is no earlieropportunitytosetinstanceattributes.Once__init__()hasfinishedexecution,theinstanceobjectisreturned,completingtheinstantiationprocess.

DefaultArgumentsProvideDefaultInstanceSetupOnecanalsouse__init__()alongwithdefaultargumentstoprovideaneffectivewayinpreparinganinstanceforuse.Inmostofthecases,thedefaultvaluesrepresentthemostcommoncasesforsettingupinstanceattributes,andsuchuseofdefaultvaluesprecludesthemfromhavingtobegivenexplicitlytotheconstructor.

Built-inTypeAttributesBuilt-in types also have attributes, and although they are technically not class instanceattributes,theyaresufficientlysimilartogetabriefmentionhere.Typeattributesdonothaveanattributedictionarylikeclassesandinstances(__dict__),sohowdowefigureoutwhatattributesbuilt-intypeshave?Theconventionforbuilt-intypesistousetwospecialattributes,__methods__and__members__,tooutlineanymethodsand/ordataattributes.

InstanceAttributesvs.ClassAttributesClassattributesaresimplydatavalueswhichareassociatedwithaclassandwithnotany

particular instances. Such values are also referred to as static members because theirvaluesremainconstant,evenifaclassisinvokedduetoinstantiationmultipletimes.Nomatter what, static members maintain their values independent of instances unlessexplicitly changed. Comparing instance attributes to class attributes is just similar tocomparingautomaticandstaticvariables.Theirmainaspectisthatyoucanaccessaclassattributewitheithertheclassoraninstance,whiletheinstancedoesnothaveanattributewiththesamename.

PythonDatabaseAccess

ThestandarddatabaseusedforPythonisDB-API.MostPythondatabaseinterfacesadheretothisstandard.Youcanchoosetherightdatabaseforyourapplication.PythonDatabaseAPI supports a wide range of database servers such as, GadFly, mSQL, MySQL,PostgreSQL,MicrosoftSQLServer11000,Informix,Interbase,Oracle,Sybase.Youmustdownload a separate DB API module for each database that you need to access. Forexample,ifyouneedtoaccessanOracledatabaseaswellasaMySQLdatabase,thenyouneedtodownloadboththeOracleandtheMySQLdatabasemodules.

The DB API provides a minimal standard for working with databases using Pythonstructuresandsyntaxwhereverpossible.

TheAPIincludes:

•ImportingtheAPImodule.

•Acquiringaconnectionwiththedatabase.

•IssuingSQLstatementsandstoredprocedures.

•Closingtheconnection

WewouldlearnalltheconceptsusingMySQL,solet’stalkaboutMySQLdbmoduleonly.

WhatisMySQLdb?MySQLdb is an interface for connecting to aMySQL database server from Python. ItimplementsthePythonDatabaseAPIv2.0andisbuiltontopoftheMySQLCAPI.

HowtoinstallMySQLdb?Beforeproceeding,youmakesureyouhaveMySQLdb installedonyourTomhine. JusttypethefollowinginyourPythonscriptandexecuteit:

#!/usr/bin/python

importMySQLdb

Ifitproducesthefollowingresult,thenitmeansMySQLdbmoduleisnotinstalled:

Traceback(mostrecentcalllast):

File“test.py”,line3,in<module>

importMySQLdb

ImportError:NomodulenamedMySQLdb

ToinstallMySQLdbmodule,downloaditfromMySQLdbDownloadpageandproceedasfollows:

$gunzipMySQL-python-1.2.2.tar.gz

$tar-xvfMySQL-python-1.2.2.tar

$cdMySQL-python-1.2.2

$pythonsetup.pybuild

$pythonsetup.pyinstall

DatabaseConnection:BeforeconnectingtoaMySQLdatabase,youneedtomakesureofthefollowingspointsgivenbelow:

•YouhavecreatedadatabaseTESTDB.

•YouhavecreatedatableSTAFFinTESTDB.

•ThistableishavingfieldsFIRST_NAME,LAST_NAME,AGE,SEXandINCOME.

•UserID“abctest”andpassword“python121”aresettoaccessTESTDB.

•PythonmoduleMySQLdbisinstalledproperlyonyourTomhine.

•YouhavegonethroughMySQLtutorialtounderstandMySQLBasics.

ForExample:

ConnectingwithMySQLdatabase“TESTDB”:

#!/usr/bin/python

importMySQLdb

#Opendatabaseconnection

db=MySQLdb.connect(“localhost”,“abctest”,“python121”,“TESTDB”)

#prepareacursorobjectusingcursor()method

cursor=db.cursor()

#executeSQLqueryusingexecute()method.

cursor.execute(“SELECTVERSION()”)

#Fetchasinglerowusingfetchone()method.

data=cursor.fetchone()

print“Databaseversion:%s”%data

#disconnectfromserver

db.close()

Output:

Databaseversion:5.0.45

CreatingDatabaseTable:

Onceadatabaseconnectionisestablished,youcaneasilycreatetablesorrecordsintothedatabaseusingexecutemethod.

ExampleforcreatingDatabasetableSTAFF:

#!/usr/bin/python

importMySQLdb




cursor=db.cursor()

#Droptableifitalreadyexistusingexecute()method.

cursor.execute(“DROPTABLEIFEXISTSSTAFF”)

# Create table as per requirement sql = “““CREATE TABLE STAFF (FIRST_NAMECHAR(20) NOT NULL,LAST_NAME CHAR(20),AGE INT,SEX CHAR(1),INCOMEFLOAT)”””

cursor.execute(sql)


db.close()

INSERTOperation:INSERToperationisrequiredwhenyouwanttocreateyourrecordsintoadatabasetable.

ExampletocreatearecordintoSTAFFtable:

#!/usr/bin/python

importMySQLdb




cursor=db.cursor()

#PrepareSQLquerytoINSERTarecordintothedatabase.

sql=“““INSERTINTOSTAFF(FIRST_NAME,LAST_NAME,AGE,SEX,INCOME)

VALUES(‘Tom’,‘David’,20,‘M’,11000)”””

try:

#ExecutetheSQLcommand

cursor.execute(sql)

#Commityourchangesinthedatabase

db.commit()

except:

#Rollbackincasethereisanyerror

db.rollback()


db.close()

AboveexamplecanbewrittenasfollowstocreateSQLqueriesdynamically:

#!/usr/bin/python

importMySQLdb




cursor=db.cursor()


sql=“INSERTINTOSTAFF(FIRST_NAME,\LAST_NAME,AGE,SEX,INCOME)\

VALUES(‘%s’,‘%s’,‘%d’,‘%c’,‘%d’)”%\(‘Tom’,‘David’,20,‘M’,11000)

try:


cursor.execute(sql)


db.commit()

except:


db.rollback()


db.close()

READOperation:READOperationondatabasemeanstofetchsomeusefulinformationfromthedatabase.Once our database connection is established, we are ready to make a query into thisdatabase.Wecanuseeitherfetchone()methodtofetchsinglerecordorfetchall()methodtofetechmultiplevaluesfromadatabasetable.

• fetchone(): Thismethod fetches the next row of a query result set.A result set is anobjectthatisreturnedwhenacursorobjectisusedtoqueryatable.

• fetchall():Thismethod fetchesall the rows ina result set. If somerowshavealready

beenextractedfromtheresultset,thefetchall()methodretrievestheremainingrowsfromtheresultset.

• rowcount: This is a read-only attribute and returns the number of rows that wereaffectedbyanexecute()method.

ExampletoqueryalltherecordsfromSTAFFtablehavingsalarymorethan5000:

#!/usr/bin/python

importMySQLdb




cursor=db.cursor()


sql=“SELECT*FROMSTAFF\

WHEREINCOME>‘%d’”%(1000)

try:


cursor.execute(sql)

#Fetchalltherowsinalistoflists.

results=cursor.fetchall()

forrowinresults:

fname=row[0]

lname=row[1]

age=row[2]

sex=row[3]

income=row[4]

#Nowprintfetchedresult

print“fname=%s,lname=%s,age=%d,sex=%s,income=%d”%\

(fname,lname,age,sex,income)

except:

print“Error:unabletofecthdata”


db.close()

Output:

fname=Tom,lname=David,age=20,sex=M,income=11000

UpdateOperation:UPDATEOperation on any database means to update one or more records, which arealready available in the database. Following is the procedure to update all the recordshavingSEXas‘M’.Here,wewillincreaseAGEofallthemalesbyoneyear.

ForExample:

#!/usr/bin/python

importMySQLdb




cursor=db.cursor()

#PrepareSQLquerytoUPDATErequiredrecords

sql=“UPDATESTAFFSETAGE=AGE+1

WHERESEX=‘%c’”%(‘M’)

try:


cursor.execute(sql)


db.commit()

except:


db.rollback()


db.close()

DELETEOperation:

DELETEoperationisrequiredwhenyouwanttodeletesomerecordsfromyourdatabase.FollowingistheproceduretodeletealltherecordsfromSTAFFwhereAGEismorethan20:

ForExample:

#!/usr/bin/python

importMySQLdb




cursor=db.cursor()

#PrepareSQLquerytoDELETErequiredrecords

sql=“DELETEFROMSTAFFWHEREAGE>‘%d’”%(20)

try:


cursor.execute(sql)


db.commit()

except:


db.rollback()


db.close()

PerformingTransactions:Transactionsareamechanismthatensuresconsistencyofdata.Transactionsshouldhavethefollowingproperties:

•Atomicity:Eitheratransactioncompletesornothinghappensatall.

•Consistency: A transactionmust start in a consistent state and leave the system in aconsistentstate.

• Isolation: Intermediate results of a transaction are not visible outside the currenttransaction.

•Durability:Once a transactionwas committed, the effects are persistent, even after a

systemfailure.

ThePythonDBAPI2.0providestwomethodstoeithercommitorrollbackatransaction.

ForExample:

#PrepareSQLquerytoDELETErequiredrecords

sql=“DELETEFROMSTAFFWHEREAGE>‘%d’”%(20)

try:


cursor.execute(sql)


db.commit()

except:


db.rollback()

COMMITOperation:Commit is theoperation,whichgivesagreensignal todatabase tofinalize thechanges,andafterthisoperation,nochangecanberevertedback.

ForExample:

db.commit()

ROLLBACKOperation:Ifyouarenotsatisfiedwithoneormoreofthechangesandyouwanttorevertbackthosechangescompletely,thenuserollback()method.

ForExample:

db.rollback()

DisconnectingDatabase:TodisconnectDatabaseconnection,useclose()method.

ForExample:

db.close()

If the connection to a database is closed by the user with the close() method, anyoutstandingtransactionsarerolledbackbytheDB.However,insteadofdependingonanyofDB lower level implementation details, your applicationwould be better off callingcommitorrollbackexplicitly.

HandlingErrors:Therearemanysourcesoferrors.AfewexamplesareasyntaxerrorinanexecutedSQLstatement, a connection failure, or calling the fetchmethod for an already canceled orfinishedstatementhandle.TheDBAPIdefinesanumberoferrorsthatmustexistineachdatabasemodule.Thefollowingtableliststheseexceptions.

ExceptionDescription

WarningUsedfornon-fatalissues.MustsubclassStandardError.

ErrorBaseclassforerrors.MustsubclassStandardError.

InterfaceError

Usedforerrorsinthedatabasemodule,notthedatabaseitself.MustsubclassError.

DatabaseError

Usedforerrorsinthedatabase.MustsubclassError.DataErrorSubclassofDatabaseErrorthatreferstoerrorsinthedata.

OperationalError

Subclass of DatabaseError that refers to errors such as the loss of a connection to thedatabase.TheseerrorsaregenerallyoutsideofthecontrolofthePythonscripter.

IntegrityError

SubclassofDatabaseErrorforsituationsthatwoulddamagetherelationalintegrity,suchasuniquenessconstraintsorforeignkeys.

InternalError

SubclassofDatabaseErrorthatreferstoerrorsinternaltothedatabasemodule,suchasacursornolongerbeingactive.

ProgrammingError

SubclassofDatabaseErrorthatreferstoerrorssuchasabadtablenameandotherthingsthatcansafelybeblamedonyou.

NotSupportedError

SubclassofDatabaseErrorthatreferstotryingtocallunsupportedfunctionality.

Your Python scripts should handle these errors, but before using any of the aboveexceptions,makesureyourMySQLdbhassupportfor thatexception.YoucangetmoreinformationaboutthembyreadingtheDBAPI2.0specification.

PYTHONNETWORKING

Pythonprovidestwolevelsofaccesstonetworkservices.Atalowlevel,youcanaccessthe basic socket support in the underlying operating system which allows you toimplementclientsandserversforbothconnectionorientedandconnectionlessprotocols.Python also has libraries that provide higher-level access to specific application-levelnetworkprotocols,suchasFTP,HTTP,andsoon.

WhatareSockets?Sockets are the endpoints of a bidirectional communications channel. Sockets maycommunicate within a process, between processes on the same machine, or betweenprocessesondifferentcontinents.Socketsmaybeimplementedoveranumberofdifferentchanneltypes:UNIXdomainsockets,TCP,UDP,andsoon.Thesocketlibraryprovidesspecific classes for handling the common transports as well as a generic interface forhandlingtherest.

Socketshavetheirownvocabulary:

ThesocketModule:Tocreateasocket,youmustusethesocket.socket()functionavailableinsocketmodule.Syntax:

s=socket.socket(socket_family,socket_type,protocol=0)

Descriptionofparameters:

•socket_family:ThisiseitherAF_UNIXorAF_INET,asexplainedearlier.

•socket_type:ThisiseitherSOCK_STREAMorSOCK_DGRAM.

•protocol:Thisisusuallyleftout,defaultingto0.

Socketobjectsareuserequiredfunctionstocreateyourclientorserverprogram.HereIamgoingtosharewithyouthelistoffunctionsrequired:

ServerSocketMethods:

ClientSocketMethods:

GeneralSocketMethods:

ASimpleServer:TowriteInternetservers,weusethesocketfunctionavailableinsocketmoduletocreateasocketobject.Asocketobjectisthenusedtocallotherfunctionstosetupasocketserver.Now,callbind (hostname,port) function tospecifyaport foryourserviceon thegivenhost.

Next, call the accept method of the returned object. This method waits until a clientconnectstotheportyouspecifiedandthenreturnsaconnectionobjectthatrepresentstheconnectiontothatclient.

Example:

#!/usr/bin/python#Thisisserver.pyfile

importsocket#Importsocketmodule

s=socket.socket()#Createasocketobject

host=socket.gethostname()#Getlocalmachinename

port=102#Reserveaportforyourservice.

s.bind((host,port))#Bindtotheport

s.listen(5)#Nowwaitforclientconnection.

whileTrue:

c,addr=s.accept()#Establishconnectionwithclient.

print‘Gotconnectionfrom’,addr

c.send(‘Thanksforconnecting’)

c.close()#Closetheconnection

ASimpleClient:Now,wewillwriteaverysimpleclientprogram,whichwillopenaconnectiontoagivenport102andgivenhost.ThisisverysimpletocreateasocketclientusingPython’ssocketmodulefunction.Thesocket.connect(hosname,port)opensaTCPconnectiontohostnameontheport.Onceyouhaveasocketopen,youcanreadfromitlikeanyIOobject.When

done,remembertocloseit,asyouwouldcloseafile.Thefollowingcodeisaverysimpleclientthatconnectstoagivenhostandport,readsanyavailabledatafromthesocket,andthenexits:

Example:

#!/usr/bin/python#Thisisclient.pyfile

importsocket#Importsocketmodule

s=socket.socket()#Createasocketobject

host=socket.gethostname()#Getlocalmachinename

port=102#Reserveaportforyourservice.

s.connect((host,port))

prints.recv(1024)

s.close#Closethesocketwhendone

Now,runthisserver.pyinbackgroundandthenrunaboveclient.pytoseetheresult.

#Followingwouldstartaserverinbackground.

$pythonserver.py&

#Onceserverisstartedrunclientasfollows:

$pythonclient.py

Output:

Gotconnectionfrom(‘127.0.0.1’,48437)

Thanksforconnecting

PythonInternetmodulesHere below is a list of some important modules, which are used in PythonNetwork/Internetprogramming.

SENDINGMAILINPYTHON

Simple Mail Transfer Protocol (SMTP) is a protocol that is used to send e-mails androuting e-mails between the mail servers. In Python there is ‘smtplib’ module, whichdefinesanSMTPclientsessionobject.SMTPclientsessionobjectisusedtosendmailtoanyInternetmachinewithanSMTPorESMTPlistenerdaemon.

SYNTAX:

importsmtplib

smtpObj=smtplib.SMTP([host[,port[,local_hostname]]])

Detailofparametersused:

•host:ThisisthehostrunningyourSMTPserver.YoucanspecifyIPaddressofthehostoradomainname.Thisisoptionalargument.

•port:Ifyouareprovidinghostargument,thenyouneedtospecifyaport,whereSMTPserverislistening.Usuallythisportwouldbe25.

•local_hostname: IfyourSMTPserver is runningonyour localmachine, thenyoucanspecify justlocalhost as of this option. An SMTP object has an instancemethod calledsendmail,whichwilltypicallybeusedtodotheworkofmailingamessage.Ittakesthreeparameters:

•Thesender-Astringwiththeaddressofthesender.

•Thereceivers-Alistofstrings,oneforeachrecipient.

•Themessage-AmessageasastringformattedasspecifiedinthevariousRFCs.

Example:

Tosendane-mailusingPythonscript.

#!/usr/bin/python

importsmtplib

sender=‘[email protected]’

receivers=[‘[email protected]’]

message=“““From:FromPerson<[email protected]>

To:ToPerson<[email protected]>

Subject:SMTPe-mailtest

Thisisateste-mailmessage.

”””

try:

smtpObj=smtplib.SMTP(‘localhost’)

smtpObj.sendmail(sender,receivers,message)

print“Mailsentsuccessfully”

exceptSMTPException:

print“Errorinsendingmail”

Incase,ifyouarenotrunninganSMTPserveronyourlocalmachine,thenyoucanuse‘smtplib’ client to communicate with a remote SMTP server. Unless you’re using awebmailservice,youre-mailproviderwillhaveprovidedyouwithoutgoingmailserverdetailsthatyoucanprovidethem,asfollows:

smtplib.SMTP(‘mail.your-domain.com’,25)

SendinganHTMLE-mailsUsingPython:WhenyousendatextmessageusingPython,thenallthecontentwillbetreatedassimpletext.EvenifyouwillincludeHTMLtagsinatextmessage,itwillbedisplayedassimpletext and HTML tags will not be formatted according to HTML syntax. But PythonprovidesoptiontosendanHTMLmessageasactualHTMLmessage.Whilesendingane-mailmessage,youcanspecifyaMimeversion,contenttypeandcharactersettosendanHTMLe-mail.

ExampletosendHTMLcontentasane-mail:

#!/usr/bin/python

importsmtplib

message=“““From:FromPerson<[email protected]>


MIME-Version:1.0

Content-type:text/html

Subject:SMTPHTMLe-mailtest

Thisisane-mailmessagetobesentinHTMLformat

<b>HereisHTMLtextforyou.</b>

<h1>HereisHeadlineforyou.</h1>

”””

try:


smtpObj.sendmail(sender,receivers,message)


exceptSMTPException:

print“Errorinsendingmail”

SendingAttachmentsasane-mail:To send an e-mail with mixed content requires setting Content-type header tomultipart/mixed.Then,textandattachmentsectionscanbespecifiedwithinboundaries.Aboundaryisstartedwithtwohyphensfollowedbyauniquenumber,whichcannotappearin themessage part of the e-mail. A final boundary denoting the e-mail’s final sectionmust also endwith two hyphens.Attached files should be encodedwith the pack(“m”)functiontohavebase64encodingbeforetransmission.

Exampletosendafile/tmp/test.txtasanattachment:

#!/usr/bin/python

importsmtplib

importbase64

filename=“/tmp/test.txt”

#Readafileandencodeitintobase64format

fo=open(filename,“rb”)

filecontent=fo.read()

encodedcontent=base64.b64encode(filecontent)#base64

sender=‘[email protected]’

reciever=‘[email protected]’

marker=“TESTMARKER”

body=”””

Thisisatestemailtosendanattachement.

”””

#Definethemainheaders.

part1=“““From:FromPerson<[email protected]>


Subject:SendingAttachement

MIME-Version:1.0

Content-Type:multipart/mixed;boundary=%s

—%s

”””%(marker,marker)

#Definethemessageaction

part2=“““Content-Type:text/plain

Content-Transfer-Encoding:8bit

%s

—%s

”””%(body,marker)

#Definetheattachmentsection

part3=“““Content-Type:multipart/mixed;name="%s"

Content-Transfer-Encoding:base64

Content-Disposition:attachment;filename=%s

%s

—%s—

”””%(filename,filename,encodedcontent,marker)

message=part1+part2+part3

try:


smtpObj.sendmail(sender,reciever,message)


exceptException:

print“Errorinsendingemail”

PYTHONMULTITHREADING

Inpythonyoucanrunmultiple threadsata time.Runningmultiple threads issimilar torunningseveraldifferentprogramswithfollowingbenefits:

•Multiplethreadswithinaprocesssharethesamedataspacewiththemainthreadandcanshareinformationorcommunicatewitheachothermoreeasilyascomparedtowhentheywereseparateprocesses.

•Threadssometimescalledlight-weightprocessesandtheydon’trequiremuchmemoryoverhead.A threadhasabeginning, anexecution sequence, andaconclusion. Ithasaninstructionpointerthatkeepstrackofwherewithinitscontextitiscurrentlyrunning.

•Itcanbepre-empted.

•Itcantemporarilybeputonholdwhileotherthreadsarerunning,thismethodiscalledyielding.

StartingaNewThread:Tostartanewthread,youneedtocallfollowingmethodavailableinthreadmodule:

thread.start_new_thread(function,args[,kwargs])

ThismethodisusedtoenableafastandefficientwaytocreatenewthreadsinbothLinuxandWindows.Themethodcall returns immediatelyand thechild threadstartsandcallsfunctionwiththepassedlistof‘agrs’.Whenfunctionreturns,thenthethreadterminates.Here, ‘args’ is a tuple of arguments; that uses an empty tuple to call function withoutpassinganyarguments.‘kwargs’isanoptionaldictionaryofkeywordarguments.

ForExample:

#!/usr/bin/python

importthread

importtime

#Defineafunctionforthethread

defprint_time(threadName,delay):

count=0

whilecount<5:

time.sleep(delay)

count+=1

print“%s:%s”%(threadName,time.ctime(time.time()))

#Createtwothreadsasfollows

try:

thread.start_new_thread(print_time,(“MyThread-1”,2,))

thread.start_new_thread(print_time,(“MyThread-2”,4,))

except:

print“Errorinstartingathread”

while1:

pass

Output:

MyThread-1:WedJan01:4501:45:172015










Althoughitisveryeffectiveforlow-levelthreading,butthethreadmoduleisverylimitedcomparedtothenewerthreadingmodule.

TheThreadingModule:

NewthreadingmoduleinPython2.4providesmuchmorepowerful,high-levelsupportforthreads.Thethreadingmoduleexposesallthemethodsofthethreadmoduleandprovidessomeadditionalmethods:

•threading.activeCount():Returnsthenumberofthreadobjectsthatareactive.

• threading.currentThread(): Returns the number of thread objects in the caller’s threadcontrol.

•threading.enumerate():Returnsalistofallthreadobjectsthatarecurrentlyactive.

In addition to themethods, the threadingmodule has the Thread class that implementsthreading.ThemethodsprovidedbytheThreadclassaregivenbelow:

•run():Therun()methodistheentrypointforathread.

•start():Thestart()methodstartsathreadbycallingtherunmethod.

•join([time]):Thejoin()waitsforthreadstoterminate.

•isAlive():TheisAlive()methodcheckswhetherathreadisstillexecuting.

•getName():ThegetName()methodreturnsthenameofathread.

•setName():ThesetName()methodsetsthenameofathread.

CreatingThreadusingThreadingModule:Toimplementanewthreadusingthethreadingmodule,youmustfollowthepointsgivenbelow:

•DefineanewsubclassoftheThreadclass.

•Overridethe__init__(self[,args])methodtoaddadditionalarguments.

•Then,overridetherun(self[,args])methodtoimplementwhatthethreadshoulddowhenstarted.

OnceyouhavecreatedthenewThreadsubclass,youcancreateaninstanceofitandthenstartanewthreadbyinvokingthestart(),whichwillinturncallrun()method.

ForExample:

#!/usr/bin/python

importthreading

importtime

exitFlag=0

classmyBook(threading.Thread):

def__init__(self,threadID,name,counter):

threading.Thread.__init__(self)

self.threadID=threadID

self.name=name

self.counter=counter

defrun(self):

print“Starting”+self.name

print_time(self.name,self.counter,5)

print“Exiting”+self.name

defprint_time(threadName,delay,counter):

whilecounter:

ifexitFlag:

thread.exit()

time.sleep(delay)


counter-=1

#Createnewthreads

thread1=myBook(1,“MyThread-1”,1)


#StartnewThreads

thread1.start()

thread2.start()

print“ExitFromMainThread”

Output:

StartingMyThread-1

StartingMyThread-2

ExitFromMainThread

MyThread-1:MonJul2701:45:10:032015







ExitingMyThread-1




ExitingMyThread-2

SynchronizingThreads:In python threading module includes a simple-to-implement locking mechanism whichwill allow you to synchronize the threads.A new lock is created by calling theLock()method, which returns the new lock. to force threads to run, The acquire(blocking)method of the new lock object is used. If blocking is set to 0, the thread will returnimmediatelywitha0value if the lockcannotbeacquiredandwitha1 if the lockwasacquired.Ifblockingissetto1,thethreadwillblockandwaitforthelocktobereleased.Therelease()methodofthethenewlockobjectwouldbeusedtoreleasethelockwhenitisnolongerrequired.

ForExample:

#!/usr/bin/python

importthreading

importtime


def__init__(self,threadID,name,counter):



self.name=name

self.counter=counter

defrun(self):


#Getlocktosynchronizethreads

threadLock.acquire()

print_time(self.name,self.counter,3)

#Freelocktoreleasenextthread

threadLock.release()

defprint_time(threadName,delay,counter):

whilecounter:

time.sleep(delay)


counter-=1

threadLock=threading.Lock()

threads=[]

#Createnewthreads



#StartnewThreads

thread1.start()

thread2.start()

#Addthreadstothreadlist

threads.append(thread1)

threads.append(thread2)

#Waitforallthreadstocomplete

fortinthreads:

t.join()

print“ExitingfromMainThread”

Output:

StartingMyThread-2







ExitingfromMainThread

MultithreadedPriorityQueue:TheQueuemoduleinpythonallowsyoutocreateanewqueueobject,whichcanholdaspecificnumberofitems.MethodsthatareusedtocontroltheQueuearegivenbelow:

•get():Theget()removesandreturnsanitemfromthequeue.

•put():Theputaddsitemtoaqueue.

•qsize():Theqsize()returnsthenumberofitemsthatarecurrentlyinthequeue.

•empty():Theempty()returnsTrueifqueueisempty;otherwise,False.

•full():thefull()returnsTrueifqueueisfull;otherwise,False.

ForExample:

#!/usr/bin/python

importQueue

importthreading

importtime

exitFlag=0


def__init__(self,threadID,name,q):



self.name=name

self.q=q

defrun(self):


process_data(self.name,self.q)

print“Exiting”+self.name

defprocess_data(threadName,q):

whilenotexitFlag:

queueLock.acquire()

ifnotworkQueue.empty():

data=q.get()

queueLock.release()

print“%sprocessing%s”%(threadName,data)

else:

queueLock.release()

time.sleep(1)

threadList=[“MyThread-1”,“MyThread-2”,“Thread-3”]

nameList=[“A”,“B”,“C”,“D”,“E”]

queueLock=threading.Lock()

workQueue=Queue.Queue(10)

threads=[]

threadID=1

#Createnewthreads

fortNameinthreadList:

thread=myThread(threadID,tName,workQueue)

thread.start()

threads.append(thread)

threadID+=1

#Fillthequeue

queueLock.acquire()

forwordinnameList:

workQueue.put(word)

queueLock.release()

#Waitforqueuetoempty

whilenotworkQueue.empty():

pass

#Notifythreadsit’stimetoexit

exitFlag=1

#Waitforallthreadstocomplete

fortinthreads:

t.join()

print“ExitingMainThread”

Output:

StartingThread-1

StartingThread-2

StartingThread-3

Thread-1processingA

Thread-2processingB

Thread-3processingC

Thread-1processingD

Thread-2processingE

ExitingThread-3

ExitingThread-1

ExitingThread-2

ExitingMainThread

PYTHONXMLPROCESSING

WhatisXML?XML is,ExtensibleMarkupLanguage (XML)and its likeHTMLorSGML.XML is aportable,opensourcelanguagethatallowstheprogrammerstodevelopapplicationsthatcan be read by other applications, regardless of operating system and/or developmentallanguage.XMLisextremelyusefulforkeepingtrackofsmalltomediumamountsofdata.

XMLParserArchitecturesandAPIs:ThePythonstandardlibraryprovidesasetofinterfacestoworkwithXML.ThetwomostbasicandbroadlyusedAPIstoXMLdataaretheSAXandDOMinterfaces.

•SimpleAPI forXML (SAX):Here, you register callbacks for events of interest andthenlettheparserproceedthroughthedocument.Thisisusefulwhenyourdocumentsarelargeor youhavememory limitations, it parses the file as it reads it fromdisk and theentirefileisneverstoredinmemory.

• Document Object Model (DOM) API: This is a World Wide Web Consortiumrecommendationwhereintheentirefile isreadintomemoryandstoredinahierarchical(tree-based)formtorepresentallthefeaturesofanXMLdocument.

ThethingisthatSAXcan’tprocessinformationasfastasDOM,whenworkingwithlargefiles.Ontheotherhand,usingDOMcankillyourresources,especiallyifusedonalotofsmallfiles.SAXisread-only,whileDOMallowschangestotheXMLfile.AsthesetwoAPIs complement eachother, there is no reasonwhyyoucan’t use themboth for largeprojects.Let’sseeasimpleexampleforXMLfilemovies.xml:

<collectionshelf=“NewArrivals”>

<movietitle=“EnemyBehind”>

<type>War,Thriller</type>

<format>DVD</format>

<year>2003</year>

<rating>PG</rating>

<stars>10</stars>

<description>TalkaboutaUS-Japanwar</description>

</movie>

<movietitle=“Transformers”>

<type>Anime,ScienceFiction</type>


<year>1989</year>

<rating>R</rating>

<stars>8</stars>

<description>Aschientificfiction</description>

</movie>

<movietitle=“Trigun”>

<type>Anime,Action</type>


<episodes>4</episodes>

<rating>PG</rating>

<stars>10</stars>

<description>VashtheStampede!</description>

</movie>

<movietitle=“Ishtar”>

<type>Comedy</type>

<format>VHS</format>

<rating>PG</rating>

<stars>2</stars>

<description>Viewableboredom</description>

</movie>

</collection>

ParsingXMLwithSAXAPIs:SAXisastandardinterfaceforevent-drivenXMLparsing.ForParsingXMLwithSAX,you need to create your own ContentHandler by subclassing xml.sax.ContentHandler.YourContentHandlerhandlestheparticulartagsandattributesofyourflavorofXML.AContentHandler object provides methods to handle various parsing events. Its owningparser calls ContentHandler methods as it passes the XML file. The methodsstartDocumentandendDocumentarecalledatthestartandtheendoftheXMLfile.TheContentHandleriscalledatthestartandendofeachelement.Herearesomemethodstounderstandbeforeproceeding:

Themake_parserMethod:Thismethodcreatesanewparserobjectandreturnsit.Theparserobjectcreatedwillbeofthefirstparsertypethesystemfinds.

xml.sax.make_parser([parser_list])

Hereparameter‘parser_list’,istheoptionalargumentconsistingofalistofparserstousewhichmustallimplementthemake_parsermethod.

TheparseMethod:ThismethodcreatesaSAXparserandusesittoparseadocument.

xml.sax.parse(xmlfile,contenthandler[,errorhandler])

Here parameters ‘xmlfile’, is the name of theXML file to read from. ‘contenthandler’,mustbeaContentHandlerobject.and‘errorhandler’,mustbeaSAXErrorHandlerobject.

TheparseStringMethod:ThereisonemoremethodtocreateaSAXparserandtoparsethespecifiedXMLstring.

xml.sax.parseString(xmlstring,contenthandler[,errorhandler])

Here parameters ‘xmlstring’, is the name of the XML string to read from.‘contenthandler’, must be a ContentHandler object. ‘errorhandler’, must be a SAXErrorHandlerobject.

ForExample:

#!/usr/bin/python

importxml.sax

classMovieHandler(xml.sax.ContentHandler):

def__init__(self):

self.CurrentData=””

self.type=””

self.format=””

self.year=””

self.rating=””

self.stars=””

self.description=””

#Callwhenanelementstarts

defstartElement(self,tag,attributes):

self.CurrentData=tag

iftag==“movie”:

print“*****Movie*****”

title=attributes[“title”]

print“Title:”,title

#Callwhenanelementsends

defendElement(self,tag):

ifself.CurrentData==“type”:

print“Type:”,self.type

elifself.CurrentData==“format”:

print“Format:”,self.format

elifself.CurrentData==“year”:

print“Year:”,self.year

elifself.CurrentData==“rating”:

print“Rating:”,self.rating

elifself.CurrentData==“stars”:

print“Stars:”,self.stars

elifself.CurrentData==“description”:

print“Description:”,self.description

self.CurrentData=””

#Callwhenacharacterisread

defcharacters(self,content):

ifself.CurrentData==“type”:

self.type=content

elifself.CurrentData==“format”:

self.format=content

elifself.CurrentData==“year”:

self.year=content

elifself.CurrentData==“rating”:

self.rating=content

elifself.CurrentData==“stars”:

self.stars=content

elifself.CurrentData==“description”:

self.description=content

if(__name__==“__main__”):

#createanXMLReader

parser=xml.sax.make_parser()

#turnoffnamepsaces

parser.setFeature(xml.sax.handler.feature_namespaces,0)

#overridethedefaultContextHandler

Handler=MovieHandler()

parser.setContentHandler(Handler)

parser.parse(“movies.xml”)

Output:

*****Movie*****

Title:EnemyBehind

Type:War,Thriller

Format:DVD

Year:2003

Rating:PG

Stars:10

Description:TalkaboutaUS-Japanwar

*****Movie*****

Title:Transformers

Type:Anime,ScienceFiction

Format:DVD

Year:1989

Rating:R

Stars:8

Description:Aschientificfiction

*****Movie*****

Title:Trigun

Type:Anime,Action

Format:DVD

Rating:PG

Stars:10

Description:VashtheStampede!

*****Movie*****

Title:Ishtar

Type:Comedy

Format:VHS

Rating:PG

Stars:2

Description:Viewableboredom

ParsingXMLwithDOMAPIs:The Document Object Model or “DOM,” is a cross-language API which is used foraccessingandmodifyingtheXMLdocuments.TheDOMisextremelyusefulforrandom-accessapplications.SAXallowstouseonedocumentatatime.IfyouarelookingatoneSAXelement,youhavenoaccesstoanotherone.theeasiestwaytoquicklyloadanXMLdocumentandtocreateaminidomobjectisbyusingthexml.dommodule.TheminidomobjectprovidesasimpleparsermethodthatwillquicklycreateaDOMtreefromtheXMLfile.

ForExample:

#!/usr/bin/python

fromxml.dom.minidomimportparse

importxml.dom.minidom

#OpenXMLdocumentusingminidomparser

DOMTree=xml.dom.minidom.parse(“movies.xml”)

collection=DOMTree.documentElement

ifcollection.hasAttribute(“shelf”):

print“Rootelement:%s”%collection.getAttribute(“shelf”)

#Getallthemoviesinthecollection

movies=collection.getElementsByTagName(“movie”)

#Printdetailofeachmovie.

formovieinmovies:

print“*****Movie*****”

ifmovie.hasAttribute(“title”):

print“Title:%s”%movie.getAttribute(“title”)

type=movie.getElementsByTagName(‘type’)[0]

print“Type:%s”%type.childNodes[0].data

format=movie.getElementsByTagName(‘format’)[0]

print“Format:%s”%format.childNodes[0].data

rating=movie.getElementsByTagName(‘rating’)[0]

print“Rating:%s”%rating.childNodes[0].data

description=movie.getElementsByTagName(‘description’)[0]

print“Description:%s”%description.childNodes[0].data

Output:

Rootelement:NewArrivals

*****Movie*****

Title:EnemyBehind

Type:War,Thriller

Format:DVD

Rating:PG

Description:TalkaboutaUS-Japanwar

*****Movie*****

Title:Transformers

Type:Anime,ScienceFiction

Format:DVD

Rating:R

Description:Aschientificfiction

*****Movie*****

Title:Trigun

Type:Anime,Action

Format:DVD

Rating:PG

Description:VashtheStampede!

*****Movie*****

Title:Ishtar

Type:Comedy

Format:VHS

Rating:PG

Description:Viewableboredom

PYTHONPROGRAMS

PythonProgramtoAddTwoMatrices

#Programtoaddtwomatrices

#usingnestedloop

X=[[12,7,3],

[4,5,6],

[7,8,9]]

Y=[[5,8,1],

[6,7,3],

[4,5,9]]

result=[[0,0,0],

[0,0,0],

[0,0,0]]

#iteratethroughrows

foriinrange(len(X)):

#iteratethroughcolumns

forjinrange(len(X[0])):

result[i][j]=X[i][j]+Y[i][j]

forrinresult:

print(r)

Output:

[17,15,4]

[10,12,9]

[11,13,18]

PythonProgramtoAddTwoNumbers

#Thisprogramaddstwonumbers

#Numbersareprovidedbytheuser

#Storeinputnumbers

num1=input(‘Enterfirstnumber:‘)

num2=input(‘Entersecondnumber:‘)

#Addtwonumbers

sum=float(num1)+float(num2)

#Displaythesum

print(‘Thesumof{0}and{1}is{2}’.format(num1,num2,sum))

Output:

Enterfirstnumber:5.3

Entersecondnumber:3.3

Thesumof5.3and3.3is8.6

PythonProgramtoCalculatetheAreaofaTriangle

#PythonProgramtofindtheareaoftriangle

#Threesidesofthetriangle

#a,b,careprovidedbytheuser

a=float(input(‘Enterfirstside:‘))

b=float(input(‘Entersecondside:‘))

c=float(input(‘Enterthirdside:‘))

#calculatethesemi-perimeter

s=(a+b+c)/2

#calculatethearea

area=(s*(s-a)*(s-b)*(s-c))**0.5

print(‘Theareaofthetriangleis%0.2f’%area)

Output:

Enterfirstside:5

Entersecondside:6

Enterthirdside:7

Theareaofthetriangleis14.70

PythonProgramtoCheckArmstrongNumber

#Pythonprogramtoifthe

#numberprovidedbythe

#userisanArmstrongnumber

#ornot

#takeinputfromtheuser

num=int(input(“Enteranumber:“))

#initialisesum

sum=0

#findthesumofthecubeofeachdigit

temp=num

whiletemp>0:

digit=temp%10

sum+=digit**3

temp//=10

#displaytheresult

ifnum==sum:

print(num,“isanArmstrongnumber”)

else:

print(num,“isnotanArmstrongnumber”)

Output1

Enteranumber:663

663isnotanArmstrongnumber

Output2

Enteranumber:371

407isanArmstrongnumber

PythonProgramtoCheckifaNumberisOddorEven

#Pythonprogramtocheckif

#theinputnumberisoddoreven.

#Anumberisevenifdivision

#by2givearemainderof0.

#Ifremainderis1,itisodd.


if(num%2)==0:

print(“{0}isEven”.format(num))

else:

print(“{0}isOdd”.format(num))

Output1

Enteranumber:73

73isOdd

Output2

Enteranumber:24

24isEven

PythonProgramtoCheckifaNumberisPositive,NegativeorZero

#Inthispythonprogram,weinputanumber

#checkifthenumberispositiveor

#negativeorzeroanddisplay

#anappropriatemessage

num=float(input(“Enteranumber:“))

ifnum>0:

print(“Positivenumber”)

elifnum==0:

print(“Zero”)

else:

print(“Negativenumber”)

#Inthisprogram,weinputanumber

#checkifthenumberispositiveor

#negativeorzeroanddisplay

#anappropriatemessage

#Thistimeweusenestedif

num=float(input(“Enteranumber:“))

ifnum>=0:

ifnum==0:

print(“Zero”)

else:

print(“Positivenumber”)

else:

print(“Negativenumber”)

Output1

Enteranumber:5

Positivenumber

Output2

Enteranumber:0

Zero

Output3

Enteranumber:-4

Negativenumber

PythonProgramtoCheckifaStringisPalindromeorNot

#Programtocheckifastring

#ispalindromeornot


my_str=input(“Enterastring:“)

#makeitsuitableforcaselesscomparison

my_str=my_str.casefold()

#reversethestring

rev_str=reversed(my_str)

#checkifthestringisequaltoitsreverse

iflist(my_str)==list(rev_str):

print(“Itispalindrome”)

else:

print(“Itisnotpalindrome”)

Output1

Enterastring:aIbohPhoBiA

Itispalindrome

Output2

Enterastring:13344331

Itispalindrome

Output3

Enterastring:palindrome

Itisnotpalindrome

PythonProgramtoCheckLeapYear


#theinputyearis

#aleapyearornot

year=int(input(“Enterayear:“))

if(year%4)==0:

if(year%100)==0:

if(year%400)==0:

print(“{0}isaleapyear”.format(year))

else:

print(“{0}isnotaleapyear”.format(year))

else:

print(“{0}isaleapyear”.format(year))

else:

print(“{0}isnotaleapyear”.format(year))

Output1

Enterayear:2012

2012isaleapyear

Output2

Enterayear:2015

2015isnotaleapyear

PythonProgramtoCheckPrimeNumber


#theinputnumberis

#primeornot



#primenumbersaregreaterthan1

ifnum>1:

#checkforfactors

foriinrange(2,num):

if(num%i)==0:

print(num,“isnotaprimenumber”)

print(i,“times”,num//i,“is”,num)

break

else:

print(num,“isaprimenumber”)

#ifinputnumberislessthan

#orequalto1,itisnotprime

else:

print(num,“isnotaprimenumber”)

Output1

Enteranumber:407

407isnotaprimenumber

11times37is407

Output2

Enteranumber:853

853isaprimenumber

PythonProgramtoConvertCelsiusToFahrenheit

#PythonProgramtoconverttemperaturein

#celsiustofahrenheitwhere,inputis

#providedbytheuserin

#degreecelsius


celsius=float(input(‘EnterdegreeCelsius:‘))

#calculatefahrenheit

fahrenheit=(celsius*1.8)+32

print(‘%0.1fdegreeCelsiusisequalto%0.1fdegreeFahrenheit’%(celsius,fahrenheit))

Output

EnterdegreeCelsius:43.7

43.7degreeCelsiusisequalto110.66degreeFahrenheit

PythonProgramtoConvertDecimalintoBinary,OctalandHexadecimal

#Pythonprogramtoconvertdecimal

#numberintobinary,octaland

#hexadecimalnumbersystem

#Takedecimalnumberfromuser

dec=int(input(“Enteraninteger:“))

print(“Thedecimalvalueof”,dec,“is:”)

print(bin(dec),“inbinary.”)

print(oct(dec),“inoctal.”)

print(hex(dec),“inhexadecimal.”)

Output

Enteraninteger:133

Thedecimalvalueof133is:

0b10000101inbinary.

0o205inoctal.

0x85inhexadecimal.

PythonProgramtoConvertDecimaltoBinaryUsingRecursion

#Pythonprogramtoconvertdecimal

#numberintobinarynumber

#usingrecursivefunction

defbinary(n):

“““Functiontoprintbinarynumber

fortheinputdecimalusingrecursion”””

ifn>1:

binary(n//2)

print(n%2,end=”)

#Takedecimalnumberfromuser

dec=int(input(“Enteraninteger:“))

binary(dec)

Output

Enteraninteger:76

1001100

PythonProgramtoConvertKilometerstoMiles

#Programtoconvertkilometers

#intomileswhere,inputis

#providedbytheuserin

#kilometers


kilometers=float(input(‘Howmanykilometers?:‘))

#conversionfactor

conv_fac=0.621371

#calculatemiles

miles=kilometers*conv_fac

print(‘%0.3fkilometersisequalto%0.3fmiles’%(kilometers,miles))

Output

Howmanykilometers?:3.7

5.500kilometersisequalto2.300miles

PythonProgramtoCounttheNumberofEachVowel

#Programtocountthenumberof

#eachvowelinastring

#stringofvowels

vowels=‘aeiou’


ip_str=input(“Enterastring:“)

#makeitsuitableforcaselesscomparisions

ip_str=ip_str.casefold()

#makeadictionarywitheachvowelakeyandvalue0

count={}.fromkeys(vowels,0)

#countthevowels

forcharinip_str:

ifcharincount:

count[char]+=1

print(count)

Output

Enterastring:Iwelcomeyoualltoreadmybookandlearnpythoneasily.

{‘e’:4,‘u’:1,‘o’:6,‘a’:5,‘i’:1}

PythonProgramtoDisplayCalendar

#Pythonprogramtodisplaycalendar

#ofgivenmonthoftheyear

#importmodule

importcalendar

#askofmonthandyear

yy=int(input(“Enteryear:“))

mm=int(input(“Entermonth:“))

#displaythecalendar

print(calendar.month(yy,mm))

Output

Enteryear:2015

Entermonth:09

September2015

Mo

Tu

We

Th

Fr

Sa

Su

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

PythonProgramtoDisplayFibonacciSequenceUsingRecursion

#PythonprogramtodisplaytheFibonacci

#sequenceupton-thtermusing

#recursivefunctions

defrecur_fibo(n):

“““Recursivefunctionto

printFibonaccisequence”””

ifn<=1:

returnn

else:

return(recur_fibo(n-1)+recur_fibo(n-2))


nterms=int(input(“Howmanyterms?“))

#checkifthenumberoftermsisvalid

ifnterms<=0:

print(“Pleseenterapositiveinteger”)

else:

print(“Fibonaccisequence:”)

foriinrange(nterms):

print(recur_fibo(i))

Output

Howmanyterms?8

Fibonaccisequence:

0

1

1

2

3

5

8

13

PythonProgramToDisplayPowersof2UsingAnonymousFunction

#PythonProgramtodisplay

#thepowersof2using

#anonymousfunction

#Takenumberoftermsfromuser

terms=int(input(“Howmanyterms?“))

#useanonymousfunction

result=list(map(lambdax:2**x,range(terms)))

#displaytheresult

foriinrange(terms):

print(“2raisedtopower”,i,“is”,result[i])

Output

Howmanyterms?6

2raisedtopower0is1

2raisedtopower1is2

2raisedtopower2is4

2raisedtopower3is8

2raisedtopower4is16

2raisedtopower5is32

PythonProgramtoDisplaythemultiplicationTable

#Pythonprogramtofindthemultiplication

#table(from1to10)c

#ofanumberinputbytheuser


num=int(input(“Displaymultiplicationtableof?“))

#useforlooptoiterate10times

foriinrange(1,11):

print(num,‘x’,i,’=’,num*i)

Output

Displaymultiplicationtableof?7

7x1=7

7x2=14

7x3=21

7x4=28

7x5=35

7x6=42

7x7=49

7x8=56

7x9=63

7x10=70

PythonProgramtoFindArmstrongNumberinanInterval

#Programtoasktheuser

#forarangeanddisplay

#allArmstrongnumbersin

#thatinterval


lower=int(input(“Enterlowerrange:“))

upper=int(input(“Enterupperrange:“))

fornuminrange(lower,upper+1):

#initializesum

sum=0

#findthesumofthecubeofeachdigit

temp=num

whiletemp>0:

digit=temp%10

sum+=digit**3

temp//=10

ifnum==sum:

print(num)

Output

Enterlowerrange:0

Enterupperrange:999

0

1

153

370

371

407

PythonProgramtoFindASCIIValueofCharacter

#Programtofindthe

#ASCIIvalueofthe

#givencharacter

#Takecharacterfromuser

c=input(“Enteracharacter:“)

print(“TheASCIIvalueof’”+c+”’is”,ord(c))

Output1

Enteracharacter:k

TheASCIIvalueof‘k’is107

Output2

Enteracharacter:=

TheASCIIvalueof‘=’is61

PythonProgramtoFindFactorialofNumberUsingRecursion

#Pythonprogramtofindthe

#factorialofanumber

#usingrecursion

defrecur_factorial(n):

“““Functiontoreturnthefactorial

ofanumberusingrecursion”””

ifn==1:

returnn

else:

returnn*recur_factorial(n-1)



#checkisthenumberisnegative

ifnum<0:

print(“Sorry,factorialdoesnotexistfornegativenumbers”)

elifnum==0:

print(“Thefactorialof0is1”)

else:

print(“Thefactorialof”,num,“is”,recur_factorial(num))

Output1

Enteranumber:-5

Sorry,factorialdoesnotexistfornegativenumbers

Output2

Enteranumber:5

Thefactorialof5is120

PythonProgramtoFindFactorsofNumber

#PythonProgramtofindthe

#factorsofanumber

#defineafunction

defprint_factors(x):

“““Thisfunctiontakesa

numberandprintsthefactors”””

print(“Thefactorsof”,x,“are:”)

foriinrange(1,x+1):

ifx%i==0:

print(i)



print_factors(num)

Output

Enteranumber:120

Thefactorsof120are:

1

2

3

4

5

6

8

10

12

15

20

24

30

40

60

120

PythonProgramtoFindHashofFile

#PythonrogramtofindtheSHA-1

#messagedigestofafile

#importhashlibmodule

importhashlib

defhash_file(filename):

””““ThisfunctionreturnstheSHA-1hash

ofthefilepassedintoit”””

#makeahashobject

h=hashlib.sha1()

#openfileforreadinginbinarymode

withopen(filename,‘rb’)asfile:

#looptilltheendofthefile

chunk=0

whilechunk!=b”:

#readonly1024bytesatatime

chunk=file.read(1024)

h.update(chunk)

#returnthehexrepresentationofdigest

returnh.hexdigest()

message=hash_file(“track1.mp3”)

print(message)

Output

633d7356947eec543c50b76a1852f92427f4dca9

PythonProgramtoFindHCForGCD


#H.C.Foftwoinputnumber

#defineafunction

defhcf(x,y):

“““Thisfunctiontakestwo

integersandreturnstheH.C.F”””

#choosethesmallernumber

ifx>y:

smaller=y

else:

smaller=x

foriinrange(1,smaller+1):

if((x%i==0)and(y%i==0)):

hcf=i

return


num1=int(input(“Enterfirstnumber:“))

num2=int(input(“Entersecondnumber:“))

print(“TheH.C.F.of”,num1,“and”,num2,“is”,hcf(num1,num2))

Output

Enterfirstnumber:40

Entersecondnumber:48

TheH.C.F.of40and48is8

PythonProgramtoFindLCM

#PythonProgramtofindthe

#L.C.M.oftwoinputnumber

#defineafunction

deflcm(x,y):

“““Thisfunctiontakestwo

integersandreturnstheL.C.M.”””

#choosethegreaternumber

ifx>y:

greater=x

else:

greater=y

while(True):

if((greater%x==0)and(greater%y==0)):

lcm=greater

break

greater+=1

returnlcm




print(“TheL.C.M.of”,num1,“and”,num2,“is”,lcm(num1,num2))

Output

Enterfirstnumber:3

Entersecondnumber:4

TheL.C.M.of3and4is12

PythonProgramtoFindNumbersDivisiblebyAnotherNumber

#PythonProgramtofindnumbers

#divisiblebythirteen

#fromalistusinganonymousfunction

#Takealistofnumbers

my_list=[12,65,54,39,102,339,221,]

#useanonymousfunctiontofilter

result=list(filter(lambdax:(x%13==0),my_list))

#displaytheresult

print(“Numbersdivisibleby13are”,result)

Output

Numbersdivisibleby13are[65,39,221]

PythonProgramtoFindSumofNaturalNumbersUsingRecursion

#Pythonprogramtofindthesumof

#naturalnumbersupton

#usingrecursivefunction

defrecur_sum(n):

“““Functiontoreturnthesum

ofnaturalnumbersusingrecursion”””

ifn<=1:

returnn

else:

returnn+recur_sum(n-1)



ifnum<0:

print(“Enterapositivenumber”)

else:

print(“Thesumis”,recur_sum(num))

Output

Enteranumber:10

Thesumis55

PythonProgramtoFindtheFactorialofaNumber


#factorialofanumber

#providedbytheuser



factorial=1

#checkifthenumberisnegative,positiveorzero

ifnum<0:

print(“Sorry,factorialdoesnotexistfornegativenumbers”)

elifnum==0:

print(“Thefactorialof0is1”)

else:

foriinrange(1,num+1):

factorial=factorial*i

print(“Thefactorialof”,num,“is”,factorial)

Output1

Enteranumber:-18

Sorry,factorialdoesnotexistfornegativenumbers

Output2

Enteranumber:9

Thefactorialof9is362,880

PythonProgramtoFindtheLargestAmongThreeNumbers

#Pythonprogramtofindthelargest

#numberamongthethree

#inputnumbers

#takethreenumbersfromuser

num1=float(input(“Enterfirstnumber:“))

num2=float(input(“Entersecondnumber:“))

num3=float(input(“Enterthirdnumber:“))

if(num1>num2)and(num1>num3):

largest=num1

elif(num2>num1)and(num2>num3):

largest=num2

else:

largest=num3

print(“Thelargestnumberis”,largest)

Output1

Enterfirstnumber:8


Enterthirdnumber:4

Thelargestnumberis16.0

Output2

Enterfirstnumber:-6

Entersecondnumber:-15

Enterthirdnumber:0

Thelargestnumberis0.0

PythonProgramtoFindtheSize(Resolution)ofImage

#PythonProgramtofindtheresolution

#ofajpegimagewithoutusing

#anyexternallibraries

defjpeg_res(filename):

””““Thisfunctionprintstheresolution

ofthejpegimagefilepassedintoit”””

#openimageforreadinginbinarymode

withopen(filename,‘rb’)asimg_file:

#heightofimage(in2bytes)isat164thposition

img_file.seek(163)

#readthe2bytes

a=img_file.read(2)

#calculateheight

height=(a[0]<<8)+a[1]

#next2bytesiswidth

a=img_file.read(2)

#calculatewidth

width=(a[0]<<8)+a[1]

print(“Theresolutionoftheimageis”,width,“x”,height)

jpeg_res(“image.jpg”)

Output

Theresolutionoftheimageis180x200

PythonProgramtoFindtheSquareRoot

#PythonProgramtocalculatethesquareroot

num=float(input(‘Enteranumber:‘))

num_sqrt=num**0.5

print(‘Thesquarerootof%0.3fis%0.3f’%(num,num_sqrt))

Output

Enteranumber:11

Thesquarerootof11.000is3.316

PythonProgramtoFindtheSumofNaturalNumbers

#Pythonprogramtofindthesumof

#naturalnumbersupton

#wherenisprovidedbyuser



ifnum<0:

print(“Enterapositivenumber”)

else:

sum=0

#usewhilelooptoiterateuntillzero

while(num>0):

sum+=num

num-=1

print(“Thesumis”,sum)

Output

Enteranumber:10

Thesumis55

PythonProgramtoGenerateaRandomNumber

#Programtogeneratearandomnumber

#between0and9

#importtherandommodule

importrandom

print(random.randint(0,9))

Output

5

PythonProgramtoIllustrateDifferentSetOperations

#Programtoperformdifferent

#setoperationslikeinmathematics

#definethreesets

E={0,2,4,6,8};

N={1,2,3,4,5};

#setunion

print(“UnionofEandNis”,E|N)

#setintersection

print(“IntersectionofEandNis”,E&N)

#setdifference

print(“DifferenceofEandNis”,E-N)

#setsymmetricdifference

print(“SymmetricdifferenceofEandNis”,E^N)

Output

UnionofEandNis{0,1,2,3,4,5,6,8}

IntersectionofEandNis{2,4}

DifferenceofEandNis{8,0,6}

SymmetricdifferenceofEandNis{0,1,3,5,6,8}

PythonProgramtoMakeaSimpleCalculator

#Programmakeasimplecalculator

#thatcanadd,subtract,multiply

#anddivideusingfunctions

#definefunctions

defadd(x,y):

“““Thisfunctionaddstwonumbers”””

returnx+y

defsubtract(x,y):

“““Thisfunctionsubtractstwonumbers”””

returnx-y

defmultiply(x,y):

“““Thisfunctionmultipliestwonumbers”””

returnx*y

defdivide(x,y):

“““Thisfunctiondividestwonumbers”””

returnx/y


print(“Selectoperation.”)

print(“1.Add”)

print(“2.Subtract”)

print(“3.Multiply”)

print(“4.Divide”)

choice=input(“Enterchoice(1/2/3/4):”)



ifchoice==‘1’:

print(num1,”+”,num2,”=”,add(num1,num2))

elifchoice==‘2’:

print(num1,”-“,num2,”=”,subtract(num1,num2))


print(num1,”*”,num2,”=”,multiply(num1,num2))


print(num1,”/”,num2,”=”,divide(num1,num2))

else:

print(“Invalidinput”)

Output

Selectoperation.

1.Add

2.Subtract

3.Multiply

4.Divide

Enterchoice(1/2/3/4):2

Enterfirstnumber:20


20-11=9

PythonProgramtoMultiplyTwoMatrices

#Programtomultiplytwomatrices

#usingnestedloops

#3x3matrix

X=[[12,7,3],

[4,5,6],

[7,8,9]]

#3x4matrix

Y=[[5,8,1,2],

[6,7,3,0],

[4,5,9,1]]

#resultis3x4

result=[[0,0,0,0],

[0,0,0,0],

[0,0,0,0]]

#iteratethroughrowsofX


#iteratethroughcolumnsofY

forjinrange(len(Y[0])):

#iteratethroughrowsofY

forkinrange(len(Y)):

result[i][j]+=X[i][k]*Y[k][j]

forrinresult:

print(r)

Output

[114,160,60,27]

[74,97,73,14]

[119,157,112,23]

PythonProgramtoPrintallPrimeNumbersinanInterval

#Pythonprogramtoasktheuser

#forarangeanddisplay

#alltheprimenumbersin

#thatinterval


lower=int(input(“Enterlowerrange:“))

upper=int(input(“Enterupperrange:“))

fornuminrange(lower,upper+1):

#primenumbersaregreaterthan1

ifnum>1:

foriinrange(2,num):

if(num%i)==0:

break

else:

print(num)

Output

Enterlowerrange:100

Enterupperrange:200

101

103

107

109

113

127

131

137

139

149

151

157

163

167

173

179

181

191

193

197

199

PythonProgramtoPrintHiGoodMorning!

#ThisprogramprintsHi,GoodMorning!

print(‘Hi,GoodMorning!’)

Output

Hi,GoodMorning!

PythonprogramtoPrinttheFibonaccisequence

#Programtodisplaythefibonacci

#sequenceupton-thternwhere

#nisprovidedbytheuser


nterms=int(input(“Howmanyterms?“))

#firsttwoterms

n1=0

n2=1

count=2

#checkifthenumberoftermsisvalid

ifnterms<=0:

print(“Pleseenterapositiveinteger”)

elifnterms==1:


print(n1)

else:


print(n1,”,”,n2,end=’,‘)

whilecount<nterms:

nth=n1+n2

print(nth,end=’,‘)

#updatevalues

n1=n2

n2=nth

count+=1

Output

Howmanyterms?12

Fibonaccisequence:

0,1,1,2,3,5,8,13,21,34,55,89

PythonProgramtoRemovePunctuationsformaString

#Programtoallpunctuationsfromthe

#stringprovidedbytheuser

#definepunctuations

punctuations=”’!()-[]{};:’”\,<>./?@#$%^&*_~”’



#removepunctuationsfromthestring

no_punct=””

forcharinmy_str:

ifcharnotinpunctuations:

no_punct=no_punct+char

#displaytheunpunctuatedstring

print(no_punct)

Output

Enterastring:“Hello!!!”,GoodMorning–Haveagoodday.

HelloGoodMorningHaveagoodday

PythonProgramtoShuffleDeckofCards

#Pythonprogramtoshufflea

#deckofcardusingthe

#modulerandomanddraw5cards

#importmodules

importitertools,random

#makeadeckofcards

deck=list(itertools.product(range(1,14),[‘Spade’,‘Heart’,‘Diamond’,‘Club’]))

#shufflethecards

random.shuffle(deck)

#drawfivecards

print(“Yougot:”)

foriinrange(5):

print(deck[i][0],“of”,deck[i][1])

Output1

Yougot:

5ofHeart

1ofHeart

8ofSpade

12ofSpade

4ofSpade

Output2

Yougot:

10ofClub

1ofHeart

3ofDiamond

2ofClub

3ofClub

PythonProgramtoSolveQuadraticEquation

#Solvethequadraticequation

#ax**2+bx+c=0

#a,b,careproviedbytheuser

#importcomplexmathmodule

importcmath

a=float(input(‘Entera:‘))

b=float(input(‘Enterb:‘))

c=float(input(‘Enterc:‘))

#calculatethediscriminant

d=(b**2)-(4*a*c)

#findtwosolutions

sol1=(-b-cmath.sqrt(d))/(2*a)

sol2=(-b+cmath.sqrt(d))/(2*a)

print(‘Thesolutionare{0}and{1}’.format(sol1,sol2))

Output

Entera:1

Enterb:5

Enterc:6

Thesolutionsare(-3+0j)and(-2+0j)

PythonProgramtoSortWordsinAlphabeticOrder

#Programtosortalphabeticallythewords

#formastringprovidedbytheuser



#breakdownthestringintoalistofwords

words=my_str.split()

#sortthelist

words.sort()

#displaythesortedwords

forwordinwords:

print(word)

Output

Enterastring:thisismysecondpythonbooktoread

book

is

my

python

read

second

this

to

PythonProgramtoSwapTwoVariables

#Pythonprogramtoswaptwovariables

#providedbytheuser

x=input(‘Entervalueofx:‘)

y=input(‘Entervalueofy:‘)

#createatemporaryvariable

#andswapthevalues

temp=x

x=y

y=temp

print(‘Thevalueofxafterswapping:{}’.format(x))

print(‘Thevalueofyafterswapping:{}’.format(y))

Output

Entervalueofx:8

Entervalueofy:15

Thevalueofxafterswapping:15

Thevalueofyafterswapping:8

PythonProgramtoTransposeaMatrix

#Programtotransposeamatrix

#usingnestedloop

X=[[12,7],

[4,5],

[3,8]]

result=[[0,0,0],

[0,0,0]]

#iteratethroughrows


#iteratethroughcolumns

forjinrange(len(X[0])):

result[j][i]=X[i][j]

forrinresult:

print(r)

Output

[12,4,3]

[7,5,8]

NOTE

This isallaboutPythonProgramming.These thingsaremust tounderstandifyouareabeginnerinlearningPythonProgramLanguage.IHopeyoulikedthebookandlearnedalotfromit.Ihavealsosharedbasicpythonprogramsinthisbook,sowhatareyouwaitingfor??TurnonyoursystemandstartcreatingyourPythonPrograms.

MOREFROMAUTHOR

PythonProgrammingForBeginners:QuickAndEasyGuideForPythonProgrammers

©Copyright2014–JamesP.Long

Allrightsreserved.Withoutlimitingtherightsundercopyrightreservedabove,nopartofthis publication maybe reproduced, stored in or introduced into a retrieval system, ortransmitted in any form, or by any means (electronic, mechanical, photocopying,recordingorotherwise)withoutthepriorwrittenpermissionofboththecopyrightownerandthepublisherofthisbook.

Theauthorandpublishersofthisbookdonotdispensemedicaladvicenorprescribetotheuseofany techniqueor treatmentforhealthdisordersandanysortofmedicalproblemswithouttheadviceofamedicalprofessional,eitherdirectlyorindirectly.Itistheintentionofthisbooktoonlyofferinformationofageneralnature.Anyspecificproblemsshouldbereferredtoyourdoctor.Ifyouchoosetousethisinformationforyourselfthentheauthorandpublisherassumenoresponsibilitywhatsoever.

http://www.amazon.com/dp/B00QR1KFVK/

complete guide for python programming · complete guide for python programming quick & easy...

Documents