__init__ in Python - Python Morsels

The __init__ method is used to initialize a class. The initializer method accepts self (the class instance) along with any arguments the class accepts and ... Articles Screencasts Exercises Courses Pastebin Gift / SignUp SignIn Watchasvideo 03:09 Showcaptions Autoplay Auto-expand Signintochangeyoursettings SignintoyourPythonMorselsaccounttosaveyourscreencastsettings. Don'thaveanaccountyet?Signuphere. Let'stalkaboutthe__init__methodinPython. ApointlessPointclass Here'saclasscalledPoint: classPoint: """2-dimensionalpoint.""" Wecanconstructanewinstanceofthisclassbycallingit: >>>p=Point() >>>p WehaveaPointobjectatthispoint,butthisPointobjectreallyhasnopointbecauseithasnofunctionality(itdoesn'tstoreanyusefuldataorhaveanymethods). WecouldmanuallyaddattributestoPointobjectstostoresomedataonthem: >>>p.x=1 >>>p.y=2 >>>p.x 1 Butdoingsowouldbealittlesilly. Itwouldbebetterifwecouldsomehowcallthisclasswithargumentstostoreattributesautomatically. Theinitializermethod Currently,ifwetrytocallthisclasswitharguments,we'llseeanerror: >>>p=Point(1,2) Traceback(mostrecentcalllast): File"",line1,in TypeError:Point()takesnoarguments >>> Inordertoacceptarguments,weneedtodefinea__init__methodinourclass. def__init__(self,x,y): self.x=x self.y=y Thefirstargumentinour__init__methodwillalwaysbeself(justlikeprettymucheveryothermethod). Afterthatweneedtodeclareanyargumentswewantourclasstoaccept. Themainthingyou'llprettymuchalwaysseeina__init__method,isassigningtoattributes. ThisisournewPointclass classPoint: """2-dimensionalpoint.""" def__init__(self,x,y): self.x=x self.y=y Ifwecallitlikebeforewithoutanyarguments,we'llseeanerrorbecausethisclassnowrequirestwoarguments,xandy: >>>p=Point() Traceback(mostrecentcalllast): File"",line1,in TypeError:__init__()missing2requiredpositionalarguments:'x'and'y' WeneedtogiveourPointclasstwoargumentsinordertogetanewinstanceofthisclass: >>>p=Point(1,2) ThisPointobjectnowhasanxattributeandayattribute: >>>p.x 1 >>>p.y 2 Thatmeansour__init__methodwascalled! Pythoncalls__init__wheneveraclassiscalled Wheneveryoucallaclass,Pythonwillconstructanewinstanceofthatclass,andthencallthatclass'__init__method,passinginthenewlyconstructedinstanceasthefirstargument(self). Unlikemanyprogramminglanguages,__init__isn'tcalledthe"constructormethod". Python's__init__methodiscalledtheinitializermethod. Theinitializermethodinitializesournewclassinstance. Sobythepointthattheinitializermethodiscalledtheclassinstancehasalreadybeenconstructed. Summary WhenyoumakeanewclassinPythonthefirstmethodyou'lllikelymakeisthe__init__method. The__init__methodallowsyoutoacceptargumentstoyourclass. Moreimportantly,the__init__methodallowsyoutoassigninitialvaluestovariousattributesonyourclassinstances. Series:Classes Classesareawaytobundlefunctionalityandstatetogether. Theterms"type"and"class"areinterchangeable:list,dict,tuple,int,str,set,andboolareallclasses. You'llcertainlyusequiteafewclassesinPython(remembertypesareclasses)butyoumaynotneedtocreateyourownoften. TotrackyourprogressonthisPythonMorselstopictrail,signinorsignup. 0% Whatisaclass? 04:34 Classesareeverywhere 03:14 Python'sself 03:28 __init__inPython 03:09 DocstringsinPython 04:43 Inheritingoneclassfromanother 04:08 AttributesareeverywhereinPython 02:30 Methodsarejustfunctionsattachedtoclasses 05:02 Whereareattributesstored? 03:07 Howattributelookupsandassignmentswork 03:35 WheredoesPythonlookformethods? 03:22 Restrictingclassattributeswith__slots__ 04:17 Classmethods 03:47 Staticmethods 02:44 WhatcomesafterIntrotoPython? IntrotoPythoncoursesoftenskipoversomefundamentalPythonconcepts. SignupbelowandI'llexplainconceptsthatnewPythonprogrammersoftenoverlook. Website SignupforPythonConceptsBeyondtheBasics ✕ ↑ ConceptsBeyondIntrotoPython IntrotoPythoncoursesoftenskipoversomefundamentalPythonconcepts. SignupbelowandI'llshareideasnewPythonistasoftenoverlook. Website Watchasvideo 03:09 TableofContents NextUp 04:43 DocstringsinPython InPythonwepreferdocstringstodocumentourcoderatherthanjustcomments.Docstringsmustbetheveryfirststatementintheirfunction,class,ormodule.Python'shelpfunctionusesthese.