Python dir() — A Simple Guide with Video - Finxter

If used without argument, Python's built-in dir() function returns the function and variable names defined in the local scope—the namespace of your current ... Skiptocontent Menu Ifusedwithoutargument,Python’sbuilt-indir()functionreturnsthefunctionandvariablenamesdefinedinthelocalscope—thenamespaceofyourcurrentmodule.Ifusedwithanobjectargument,dir(object)returnsalistofattributeandmethodnamesdefinedintheobject’sscope.Thus,dir()returnsallnamesinagivenscope. TableofContents UsageVideodir()Syntaxdir()InteractiveShellExercise:Understandingdir()Usingdir()onModulesOverwritingdir()with__dir__()SummaryWheretoGoFromHere? Usage Learnbyexample!Herearesomeexamplesofhowtousethedir()built-infunction. Here’stheusewithoutanargument: alice=22 bob=42 print(dir()) Itprintstheimplicitlyandexplicitlydefinednamesinyourmodulewhereyourunthiscode: ['__annotations__','__builtins__','__doc__','__file__','__loader__','__name__','__package__','__spec__','alice','bob'] Thelasttwovaluesinthelistarethenames'alice'and'bob'. Thefollowingcodeexemplifiestheuseofdir()withanobjectargumentofclassCar. classCar: speed=100 color='black' porsche=Car() print(dir(porsche)) TheclassCarhastwoattributes.IfyouprintthenamesoftheporscheinstanceoftheCarclass,youobtainthefollowingoutput: ['__class__','__delattr__','__dict__','__dir__','__doc__','__eq__','__format__','__ge__','__getattribute__','__gt__','__hash__','__init__','__init_subclass__','__le__','__lt__','__module__','__ne__','__new__','__reduce__','__reduce_ex__','__repr__','__setattr__','__sizeof__','__str__','__subclasshook__','__weakref__','color','speed'] Thefinaltwoattributesare'color'and'speed',theonesyoudefined.Therearemanyothernamesinthelistwiththedoubleunderscore(calleddunder).ThesearetheattributeandmethodnamesalreadydefinedimplicitlybythePythonenvironmentforanyobject.Forexample,__str__givesthedefaultstringrepresentationofagivenobject. Videodir() Syntaxdir() Syntax: dir()->namesdefinedinthelocalscope/namespace. dir(object)->namesdefinedfortheobject. ArgumentsobjectTheobjectforwhichthenamesshouldbereturned.ReturnValuelistReturnsallnamesdefinedinthenamespaceofthespecifiedobject.Ifnoobjectargumentisgiven,itreturnsthenamesdefinedinthelocalnamespaceofthemoduleinwhichyourunthecode. InteractiveShellExercise:Understandingdir() Considerthefollowinginteractivecode: Exercise:Guesstheoutputbeforerunningthecode.Dobothcars,porscheandtesla,generatethesameoutput? Butbeforewemoveon,I’mexcitedtopresentyoumynewPythonbookPythonOne-Liners(AmazonLink). Ifyoulikeone-liners,you’llLOVEthebook.It’llteachyoueverythingthereistoknowaboutasinglelineofPythoncode.Butit’salsoanintroductiontocomputerscience,datascience,machinelearning,andalgorithms.TheuniverseinasinglelineofPython! Thebookwasreleasedin2020withtheworld-classprogrammingbookpublisherNoStarchPress(SanFrancisco). Link:https://nostarch.com/pythononeliners Usingdir()onModules YoucanalsousePython’sbuilt-indir()methodonmodules.Forexample,afterimportingtherandommodule,youcanpassitintothedir(random)function.Thisgivesyouallthenamesandfunctionsdefinedinthemodule. importrandom print("Therandommodulecontainsthefollowingnames:") print(dir(random)) Theoutputisthefollowing: Therandommodulecontainsthefollowingnames: ['BPF','LOG4','NV_MAGICCONST','RECIP_BPF','Random','SG_MAGICCONST','SystemRandom','TWOPI','_BuiltinMethodType','_MethodType','_Sequence','_Set','__all__','__builtins__','__cached__','__doc__','__file__','__loader__','__name__','__package__','__spec__','_acos','_bisect','_ceil','_cos','_e','_exp','_inst','_itertools','_log','_os','_pi','_random','_sha512','_sin','_sqrt','_test','_test_generator','_urandom','_warn','betavariate','choice','choices','expovariate','gammavariate','gauss','getrandbits','getstate','lognormvariate','normalvariate','paretovariate','randint','random','randrange','sample','seed','setstate','shuffle','triangular','uniform','vonmisesvariate','weibullvariate'] Thisway,youcanquicklyexplorethecontentsofamoduleandwhichfunctionsyoumaywanttouseinyourowncode! Overwritingdir()with__dir__() Tocustomizethereturnvalueofthedir()functiononacustomclass,youcanoverwritethe__dir__()methodandreturnthevaluestobereturned.Thisway,youcanhidenamesfromtheuserorfilteroutonlyrelevantnamesofyourobject. classCar: speed=100 color='gold' def__dir__(self): return['porsche','tesla','bmw'] tesla=Car() print(dir(tesla)) Theoutputisthenonsensicallistof“names”: ['bmw','porsche','tesla'] Summary Therearetwodifferentusecasesforthedir()function. Ifusedwithoutargument,Python’sbuilt-indir()functionreturnsthefunctionandvariablenamesdefinedinthelocalscope—thenamespaceofyourcurrentmodule.Ifusedwithanobjectargument,dir(object)returnsalistofattributeandmethodnamesdefinedintheobject’sscope. Thus,dir()returnsallnamesinagivenscope. Source:Documentation Ihopeyouenjoyedthearticle!ToimproveyourPythoneducation,youmaywanttojointhepopularfreeFinxterEmailAcademy: DoyouwanttoboostyourPythonskillsinafunandeasy-to-consumeway?Considerthefollowingresourcesandbecomeamastercoder! 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