ref.pdf

PythonReferenceManual

Release2.5

GuidovanRossum

FredL.Drake,Jr.,editor

19thSeptember,2006

PythonSoftwareFoundation

Email: docs@python.org

Copyrightc 2001-2006PythonSoftwareFoundation.Allrightsreserved.

Copyrightc 1995-2000CorporationforNationalResearchInitiatives.Allrightsreserved.

Seetheendofthisdocumentforcompletelicenseandpermissionsinformation.

Abstract

Pythonisaninterpreted,object-oriented,high-levelprogramminglanguagewithdynamicsemantics.Itshigh-

levelbuiltindatastructures,combinedwithdynamictypinganddynamicbinding,makeitveryattractivefor

rapidapplicationdevelopment,aswellasforuseasascriptingorgluelanguagetoconnectexistingcomponents

together.Python’ssimple,easytolearnsyntaxemphasizesreadabilityandthereforereducesthecostofprogram

maintenance.Pythonsupportsmodulesandpackages,whichencouragesprogrammodularityandcodereuse.The

Pythoninterpreterandtheextensivestandardlibraryareavailableinsourceorbinaryformwithoutchargeforall

majorplatforms,andcanbefreelydistributed.

Thisreferencemanualdescribesthesyntaxand“coresemantics”ofthelanguage.Itisterse,butattemptsto

beexactandcomplete.Thesemanticsofnon-essentialbuilt-inobjecttypesandofthebuilt-infunctionsand

modulesaredescribedinthe PythonLibraryReference . Foraninformalintroductiontothelanguage,seethe

PythonTutorial . ForCorC ++ programmers,twoadditionalmanualsexist: ExtendingandEmbeddingthePython

Interpreter describesthehigh-levelpictureofhowtowriteaPythonextensionmodule,andthe Python/CAPI

ReferenceManual describestheinterfacesavailabletoC/C ++ programmersindetail.

CONTENTS

1Introduction 1

1.1AlternateImplementations ...................................... 1

1.2Notation ............................................... 2

2Lexicalanalysis 3

2.1Linestructure ............................................. 3

2.2Othertokens ............................................. 6

2.3 Identiﬁersandkeywords ....................................... 6

2.4Literals ................................................ 7

2.5Operators ............................................... 10

2.6Delimiters .............................................. 10

3Datamodel 13

3.1Objects,valuesandtypes ....................................... 13

3.2Thestandardtypehierarchy ..................................... 14

3.3New-styleandclassicclasses .................................... 20

3.4Specialmethodnames ........................................ 21

4Executionmodel 33

4.1Namingandbinding ......................................... 33

4.2Exceptions .............................................. 34

5Expressions 37

5.1Arithmeticconversions ........................................ 37

5.2Atoms ................................................ 37

5.3Primaries ............................................... 40

5.4Thepoweroperator .......................................... 42

5.5Unaryarithmeticoperations ..................................... 43

5.6Binaryarithmeticoperations ..................................... 43

5.7Shiftingoperations .......................................... 44

5.8Binarybit-wiseoperations ...................................... 44

5.9Comparisons ............................................. 44

5.10Booleanoperations .......................................... 46

5.11Lambdas ............................................... 46

5.12Expressionlists ............................................ 46

5.13Evaluationorder ........................................... 47

5.14Summary ............................................... 47

6Simplestatements 49

6.1Expressionstatements ........................................ 49

6.2Assertstatements .......................................... 49

6.3Assignmentstatements ....................................... 50

6.4The pass statement ......................................... 52

6.5The del statement ......................................... 52

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