UsingJythontoPrototypeandExtendJava‐basedSystems

DaleParson,DylanSchwesinger

andTheaSteele,KutztownUniversityPACISE2011

PythonandJython

•  JythonisanopensourceimplementaEonofaninterpreterforPython.Python:

– hasclasses,inheritanceandpolymorphism,makingitagoodcandidateforspecifyingandprototypingobject‐orientedJavasystemsandcomponents.

– hassource‐levelgenericcontainertypes(sequences,setsandmaps),funcEonalprogrammingconstructs(first‐classfuncEons,closures,generators,higherorderfuncEons),andrun‐EmeinterpretaEon,makingitagoodcandidateforrapidprototyping.

JythonandJava

•  JythoniswriOeninJavatocompilePythonsourcetobytecodefortheJavaVirtualMachine(JVM).

•  JythoncanimportanycompiledJavaclassanduseitsobjectsasPythonobjects.

•  Jythoncanusethesubstan<alJavalibrarycodebasewithoutanyneedtowritewrappercode.

•  JythonalsocomeswithasubstanEalnaEvePythonlibrarysimilartoC‐basedPython.

•  AJavaapplicaEoncanuseaJythoninterpreterasaJavaobject,requiringveryliOlewrappercode.

ThreeExtensionLanguageExtensionMechanisms

Extension Language Script (1)

Extension Language Interpreter

Dynamically loaded application primitives (2)

Built-in language primitives

Primitive-to-extension callbacks (3)

Arrows show direction of subroutine invocations.

ThreeJythonExtensionMechanisms

Jython script (1)

Jython interpreter, byte code compiler

Dynamically imported Java classes (2)

Built-in language primitives

Java-to-Jython callbacks (3), e.g., Jython listeners for Java-generated events.

Jython‐Javaextensionmechanisms

•  JythoncanimportanduseJavaclasses,includingreflecEonandmulEthreading.

•  JythoncanimplementJavainterfaces,includingeventlistenerinterfaces.

•  Interfaceinheritanceandpolymorphism.

•  JythoncanextendJavaclasses.•  ImplementaEoninheritanceanddelegaEon.

•  JythoninterpretercanworkasaJavaobject.

AJavagraphicalgame,allinJython

Buildingthegame

•  Jythoninterpreterallowedustobuildandplayincrementally–itisworkingpseudocode.

•  Physicalprototypewasnotnecessary.• WeavoidedmanydetailedissuesofJavaimplementaEonwhileexploringthegamedesignspace.

•  Codebaseiscompactandreadable.

•  WecouldusethefullJavaSwinglibrary.•  OtherslibrariessuchasSWTareequallyaccessible.

•  GUIcodeismoreconcisethanJavacode.

Game‐buildingpi\alls.

•  DynamictypingdeferstypeerrordetecEonunElrunEme.

•  ExhausEvetesEngisessenEaltocatchtypeerrors.•  TranslaEonofJavatypestoPythontypesoccurswhenthereisaPythoncounterpart.

•  Forexample,aJavaStringobjectbecomesaPythonstring,requiringPythonstringfuncEons,notjava.lang.Stringmethods.ThistranslaEondoesnothappenforJavaclasseswithnoPythoncounterparts.

•  Interpretedperformancenoprobleminthisproject.

Jython‐JavaMusicalKeyboard

JustIntonaEonKeyboard

•  OnerowperMIDI(MusicalInstrumentDigitalInterface)channel(voice),upto16.

•  javax.sound.midisoundlibraryusedbyJython.•  Hookstoexternalso`ware&hardwaresynthsaswell.

•  BuOonsforkeys,spinnersforoctaveandotherparameters,check&comboboxesfromSwing.

•  ConstrucEonoftranslaEontablesfornon‐standardscalesusesPythonfuncEonalprogramming.

LiveCoding!

•  LivecodingistheacceptedpracEceofcoding‐as‐performancebylaptopmusicians.

•  JythonsupportsuseofastylizedformofPythonprogrammingtoimprovisesynthesizedmusic.

•  Pythonsupportforextensibleclasses,reflecEon,andsourcecodeinterpretaEon(eval,execandcompile)allowusingPythonasadomain‐specificlanguage.

•  EachgraphicalcontrolbecomesasymbolavailableformanipulaEonasanrvalueoranlvalueinaPythonexpression.SwingEmersusedfortempo&meter.

JythonConstructsforLiveCoding

•  AJythonsubclassforeachJavaGUIcontrolclassaddsacommongeOer/seOermethodpairtoeach.Gedng/sedngbecomesorthogonaltothetypeofcontrol.

•  APythonpropertyallowseachorthogonalgeOertobemanipulatedasanrvalue,andeachseOerasanlvalue,inalivecodePythonexpression.

•  PythonsupportsaddiEonoffieldsandmethodstoclassesandindividualobjectsa`erconstrucEon.IncrementalconstrucEonoflivecodingfields,methodsandproperEesoccursintandemwithassociated,incrementalGUIconstrucEon.

•  Python’sexecfuncEonallowslivecodetobecompiled.

Workavoidedinlivecoding

•  AlanguagesuchasJavawouldrequiredesigningaspecialpurposelanguage,

•  andusingtoolssuchasscannerandparsergeneratorstocompilelivecodetoanintermediateform(VMcode),

•  andprovidingrunEmesupportforthelivecodeVM.•  Jythoneliminatestheneedfordesigningacustomlanguageanditssupporttools.Thedomain‐specificlanguageisanincrementalextensionofPython.

Jython,JavaandC++performance

•  JythonisconsiderableslowthanJava,andperformancecanactuallydegradeinmulEthreadedJythononamassivemulEprocessor,but

•  JavacanrunasfastorfasterthanopEmizedC++onmodernprocessorsandmulEprocessors.

•  Seebenchmarksreportedinthepaper.

•  ConclusionistheJavaisnowfastenoughtohandlemanyEme‐constrainedtasks(e.g.,audiodataflow),makingJythonaOracEveinatwo‐Eeredso`warearchitecture.

Two‐EeredArchitecture

JythonuserinterfaceandconfiguraEonwithsynchronizedinteracEonwithJavasignalprocessingthreads

Java signal processing thread(s) audio inputs

audio outputs

query audio meta-data

configure audio signal thread(s)

Conclusions

•  Python’sobject‐orientedfeaturesmakeitagoodfitforobject‐orientedmodeling,anditsfuncEonallanguagefeaturesandrun‐EmecompilaEonmakeitgoodforcompactprototyping.

•  Jython’sseamlessintegraEonintoJavamakeitidealforincrementalprototypingandextensionofJavasystemswhileleveragingJava&Pythonlibraries.

•  PythonextensionmechanismsmakeitidealforincrementalconstrucEonofdomainlanguages.