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12,300 | data hiding is software development technique specifically used in object oriented programming to hide internal object details(data membersit ensures exclusive data access to class members and protects object integrity by preventing unintended or intended changes data hiding is also known as information hiding an objec... |
12,301 | file " :\python programs\class_method py"line in print("total count", __secretcountcannot access private variable directly attributeerror'counterobject has no attribute '__secretcountdata encapsulation and data abstractionwe can restrict access of methods and variables in class with the help of encapsulation it will pr... |
12,302 | two underscores examplefor access modifiers with data abstraction class student__a= #private variable = #public variable def __private_method(self)#private method print("private method is called"def public_method(self)#public method print("public method is called"print(" ",self __a#can be accessible in same class =stud... |
12,303 | constructors are generally used for instantiating an object the task of constructors is to initialize(assign valuesto the data members of the class when an object of class is created in python the __init__(method is called the constructor and is always called when an object is created syntax of constructor declaration ... |
12,304 | student object is created roll no of student name no of studentajay age no of student programsdefine class rectangle using length and width it has method which can compute area class rectangledef __init__(self, , )self = self = def area(self)return self *self =rectangle( , print( area()output |
12,305 | getarea and getcircumference inside this class class circledef __init__(self,radius)self radius=radius def getarea(self)return *self radius*self radius def getcircumference(self)return * *self radius =circle( print("area=", getarea()print("circumference=", getcircumference()outputarea circumference types of constructor... |
12,306 | argumentclass studentdef __init__(self)print("this is non parameterized constructor"def show(self,name)print("hello",names =student( show("world"outputthis is non parameterized constructor hello world examplecounting the number of objects of class class studentcount= def __init__(self)student count=student count+ |
12,307 | =student(print("the number of student objects",student countoutputthe number of student objects parameterized constructorconstructor with parameters is known as parameterized constructor the parameterized constructor take its first argument as reference to the instance being constructed known as self and the rest of th... |
12,308 | outputthis is parameterized constructor hello world destructora class can define special method called destructor with the help of _del_ (it is invoked automatically when the instance (objectis about to be destroyed it is mostly used to clean up non memory resources used by an instance(objectexamplefor destructor class... |
12,309 | this is non parameterized constructor this is non parameterized constructor destructor called method overloadingmethod overloading is the ability to define the method with the same name but with different number of arguments and data types with this ability one method can perform different tasksdepending on the number ... |
12,310 | area( area( , output traceback (most recent call last)file " :\python programs\trial py"line in area( , typeerrorarea(takes positional argument but were given python does not support method overloading it is not possible to define more than one method with the same name in class in python this is because method argumen... |
12,311 | output in the above example same method works for two different data types it is clear that method overloading is not supported in python but that does not mean that we cannot call method with different number of arguments there are couple of alternatives available in python that make it possible to call the same metho... |
12,312 | elif !=noneprint(" argument"elseprint(" arguments"obj=demo(obj arguments("amol","kedar","sanjay"obj arguments("amit","rahul"obj arguments("sidharth"obj arguments(output arguments arguments argument arguments |
12,313 | overloading class operationdef add(self, , )return + op=operation(to add two integer numbers print("addition of integer numbers",op add( , )to add two floating numbers print("addition of integer numbers",op add( , )to add two strings print("addition of stings",op add("hello","world")outputaddition of integer numbers ad... |
12,314 | the mechanism of designing and constructing classes from other classes is called inheritance inheritance is the capability of one class to derive or inherit the properties from some another class the new class is called derived class or child class and the class from which this derived class has been inherited is the b... |
12,315 | class aproperties of class class ( )class inheriting property of class more properties of class example example of inheritance without using constructor class vehicle#parent class name="marutidef display(self)print("name",self nameclass category(vehicle)drived class price= def disp_price(self)print("price",self priceca... |
12,316 | namemaruti price example example of inheritance using constructor class vehicle#parent class def __init__(self,name,price)self name=name self price=price def display(self)print("name",self nameclass category(vehicle)drived class def __init__(self,name,price)vehicle __init__(self,name,price#pass data to base constructor... |
12,317 | car display(car disp_price(outputnamemaruti price namehonda price multilevel inheritancein multilevel inheritancefeatures of the base class and the derived class are further inherited into the new derived class this is similar to relationship representing child and grandfather |
12,318 | class aproperties of class class ( )class inheriting property of class more properties of class class ( )class inheriting property of class thusclass also inherits properties of class more properties of class example python program to demonstrate multilevel inheritance #mutilevel inheritance class def display (self)pri... |
12,319 | print("class " = ( display ( display ( display (outputclass class class example python program to demonstrate multilevel inheritance base class class grandfathergrandfathername ="def grandfather(self)print(self grandfathername |
12,320 | class father(grandfather)fathername "def father(self)print(self fathernamederived class class son(father)def parent(self)print("grandfather :"self grandfathernameprint("father :"self fathernamedriver' code son( grandfathername "srinivass fathername "ankushs parent(outputgrandfather srinivas |
12,321 | multiple inheritancewhen class can be derived from more than one base classes this type of inheritance is called multiple inheritance in multiple inheritanceall the features of the base classes are inherited into the derived class syntaxclass avariable of class functions of class class bvariable of class functions of c... |
12,322 | more properties of class examplepython program to demonstrate multiple inheritance base class class fatherdef display (self)print("father"base class class motherdef display (self)print("mother"derived class class son(father,mother)def display (self)print("son" son( display ( display ( display ( |
12,323 | son mother father hierarchical inheritancewhen more than one derived classes are created from single base this type of inheritence is called hierarchical inheritance in this programwe have parent (baseclass and two child (derivedclasses example python program to demonstrate hierarchical inheritance base class class par... |
12,324 | print("this function is in parent class "derived class class child (parent)def func (self)print("this function is in child "derived class class child (parent)def func (self)print("this function is in child "object child (object child (object func (object func (object func (object func ( |
12,325 | this function is in parent class this function is in child this function is in parent class this function is in child method overridingmethod overriding is an ability of class to change the implementation of method provided by one of its base class method overriding is thus strict part of inheritance mechanism to overr... |
12,326 | def display(self)print("this is derived class"obj= (instance of child obj display(child class overriden method outputthis is derived class using super(methodthe super(method gives you access to methods in super class from the subclass that inherits from it the super(method returns temporary object of the superclass tha... |
12,327 | obj= (instance of child obj display(child class overriden method outputthis is base class this is derived class composition classesin composition we do not inherit from the base class but establish relationship between classes through the use of instance variables that are references to other objects composition means ... |
12,328 | instance_variable_of_generic_class=genericclass #use this instance somewhere in the class some_method(instance_varable_of_generic_classfor examplewe have three classes emailgmail and yahoo in email class we are referring the gmail and using the concept of composition exampleclass gmaildef send_email(self,msg)print("sen... |
12,329 | client =email(client send_email("hello"client set_provider(yahoo()client send_email("hello"outputsending 'hellofrom gmail sending 'hellofrom yahoo customization via inheritance specializing inherited methodsthe tree-searching model of inheritance turns out to be great way to specialize systems because inheritance finds... |
12,330 | instancesubclasses completelyprovide attributes that may replace inherited attributes to superclass expects findand extend superclass methods by calling back to the superclass from an overridden method examplefor specilaized inherited methods class "parent class#parent class def display(self)print("this is base class"c... |
12,331 | behavior rather than replacing it completely extension is the only way to interface with superclass the following program defines multiple classes that illustrate variety of common techniques super defines method function and delegate that expects an action in subclass inheritor doesn' provide any new namesso it gets e... |
12,332 | class superdef method(self)print("in super method"#default behavior def delegate(self)self action(#expected to be defined class inheritor(super)pass class replacer(super)#replace method completely def method(self)print("in replacer method"class extender(super)#extend method behavior def method(self)super method(selfpri... |
12,333 | programming in python object oriented programming is way of computer programming using the idea of "objectsto represents data and methods it is alsoan approach used for creating neat and reusable code instead of redundant one |
12,334 | procedural oriented programming object-oriented programming (oopprocedural-oriented programming (popit is bottom-up approach it is top-down approach program is divided into objects program is divided into functions makes use of access modifiers 'public'private'protecteddoesn' use access modifiers it is more secure it i... |
12,335 | class is collection of objects or you can say it is blueprint of objects defining the common attributes and behavior now the question ariseshow do you do thatclass is defined under "classkeyword exampleclass class ()/class is the name of the class |
12,336 | exampleclass employee()def __init__(self,name,age,id,salary)//creating function self name name /self is an instance of class self age age self salary salary self id id emp employee("harshit", , , //creating objects emp employee("arjun", , , print(emp __dict__)//prints dictionary |
12,337 | methodologiesinheritance polymorphism encapsulation abstraction |
12,338 | ever heard of this dialogue from relatives "you look exactly like your father/motherthe reason behind this is called 'inheritancefrom the programming aspectit generally means "inheriting or transfer of characteristics from parent to child class without any modificationthe new class is called the derived/child class and... |
12,339 | single level inheritance enables derived class to inherit characteristics from single parent class |
12,340 | class employee ()://this is parent class def __init__(selfnameagesalary)self name name self age age self salary salary class childemployee(employee )://this is child class def __init__(selfnameagesalary,id)self name name self age age self salary salary self id id emp employee ('harshit', , print(emp ageoutput |
12,341 | multi-level inheritance enables derived class to inherit properties from an immediate parent class which in turn inherits properties from his parent class exampleclass employee()://super class def __init__(self,name,age,salary)self name name self age age self salary salary class childemployee (employee)://first child c... |
12,342 | def __init__(selfnameagesalary)self name name self age age self salary salary emp employee('harshit', , emp childemployee ('arjun', , print(emp ageprint(emp ageoutput , |
12,343 | hierarchical level inheritance enables more than one derived class to inherit properties from parent class exampleclass employee()def __init__(selfnameagesalary)self name name self age age self salary salary //hierarchical inheritance |
12,344 | def __init__(self,name,age,salary)self name name self age age self salary salary class childemployee (employee)def __init__(selfnameagesalary)self name name self age age self salary salary emp employee('harshit', , emp employee('arjun', , |
12,345 | multiple level inheritance enables one derived class to inherit properties from more than one base class exampleclass employee ()//parent class def __init__(selfnameagesalary)self name name self age age self salary salary |
12,346 | def __init__(self,name,age,salary,id)self name name self age age self salary salary self id id class childemployee(employee ,employee )def __init__(selfnameagesalary,id)self name name self age age self salary salary self id id emp employee ('harshit', , emp employee ('arjun', , , |
12,347 | you all must have used gps for navigating the routeisn' it amazing how many different routes you come across for the same destination depending on the trafficfrom programming point of view this is called 'polymorphismit is one such oop methodology where one task can be performed in several different ways to put it in s... |
12,348 | compile-time polymorphism run-time polymorphism |
12,349 | compile-time polymorphism also called as static polymorphism which gets resolved during the compilation time of the program one common example is "method overloading |
12,350 | class employee ()def name(self)print("harshit is his name"def salary(self)print(" is his salary"def age(self)print(" is his age"class employee ()def name(self)print("rahul is his name"def salary(self)print(" is his salary"def age(self)print(" is his age" |
12,351 | obj name(obj salary(obj age(obj_emp employee (obj_emp employee (func(obj_emp func(obj_emp outputharshit is his name is his salary is his age rahul is his name is his salary is his age |
12,352 | run-time polymorphism is alsocalled as dynamic polymorphism where it gets resolved into the run time one common example of run-time polymorphism is "method overriding |
12,353 | class employee()def __init__(self,name,age,id,salary)self name name self age age self salary salary self id id def earn(self)pass class childemployee (employee)def earn(self)//run-time polymorphism print("no money" |
12,354 | an introduction to oop using pythonpart --basic principles and syntax what is object-oriented programming object-oriented programming (oop)deservedly or nothas something of reputation as an obtuse and mysterious way of programming you may have heard of itand even heard that it is powerful way of writing programsbut you... |
12,355 | procedural vs object-oriented programming one good way of describing something new is to compare it with something old most atmospheric and oceanic scientists have had experience with procedural programmingso we'll start there procedural programs look at the procedural world in terms of two entities"dataand "functions ... |
12,356 | soin summaryobjects are made up of attributes and methodsthe structure of common pattern for set of objects is called its classand specific realizations of that pattern are called "instances of that class recall that all the python "variableswe introduced earlier are actually objects (in factbasically everything in pyt... |
12,357 | let' do quick review of syntax for objects firstto refer to attributes review of syntax for or methods of an instanceyou add period after the object name and then objects put the attribute or method name to set an attributethe reference should be on the lefthand side of the equal signthe opposite is the case to read an... |
12,358 | example of how objects workarrays while lists have their usesin scientific computingarrays are the central object most of our discussion of arrays has focused on functions that create and act on arrays arrayshoweverare objects like any other object and have attributes and methods built-in to themarrays are more than ju... |
12,359 | the non-double-underscore names are names of "publicattributes and methodsi attributes and methods normal users are expected to access public attributes and and (possiblyredefine number of the methods and attributes of are methods duplicates of functions (or the output of functionsthat act on arrays ( transposet)so you... |
12,360 | the array the cumsum method returns flattened version of the array where each element is the cumulative sum of all the elements before finallythe object attribute is the transpose of the array versions of astypeshapeand cumsum while it' nice to have bunch of array attributes and methods attached to the array objectin p... |
12,361 | remembermethods need to be called or else they don' do anythingincluding the parentheses to specify the calling argument list tells the interpreter you're calling the method in terms of the "outputof the methodsome methods act like functionreturning their output as return value other methods do their work "in-place,on ... |
12,362 | example (example of class definition for book class)this class provides template for holding and manipulating information about book the class definition provides single method (besides the initialization methodthat returns formatted bibliographic reference for the book the code below gives the class definition and the... |
12,363 | object this has to do with the oop idea of inheritancewhich is topic beyond the scope of this book suffice it to say that classes you create can inherit or incorporate attributes and methods from other classes base classes (class that do not depend on other classesinherit from objecta special object in python that prov... |
12,364 | if you type print beauty write bib entry(at the interpreter (after running the file)what will happen how would you change the publication year for the beauty book to " "solution and discussionmy answers typeprint pynut author remember that once an instance of book is createdthe attributes are attached to the actual ins... |
12,365 | and place information will be unneeded and article titlevolume numberand pages will be needed make sure this class also has the methods write bib entry and make authoryear solution and discussionhere are my answers here' another instance of bookwith call to the write bib entry methodmadeup book("doe""john""good book""c... |
12,366 | the new portion is lines - none of the rest of the class definition needs to change the class definition for article (with line continuations added to fit the code on the pageis class article(object)def __init__(selfauthorlastauthorfirstarticletitlejournaltitlevolumepagesyear)self authorlast authorlast self authorfirst... |
12,367 | programming easier making classes work together to make complex programming easier so in our introduction to object-oriented programming (oop)we found out summary of introduction that objects hold attributes (dataand methods (functions that act on datato oop together in one related entity realizations of an object are ... |
12,368 | the bibliography class hasas its main attributea list of entries which are instances of book and article classes rememberinstances of book and article can be thought of as books and articlesthe instances are the "objectsthat specific books and articles are nextwe write methods for bibliography that can manipulate the l... |
12,369 | note that at the end of the sort entries alpha method definitioni use the del command to make sure that tmp disappears need to do this because lists are mutableand python assignment is by reference not value (see for more discussion on reference vs valueif do not remove tmpthe tmp might float around as reference to the... |
12,370 | the procedural sorting function you' write would need know which elements you want to sort with (here the second and third elements of the arraybut the index for every array of data would potentially be differentdepending on where in the array that data is stored for that source type thusin your sorting functionyou' ne... |
12,371 | to initialize stringin order to grow it in concatenation steps such as in for loopstart by setting the string variable to an empty string (which is just ''solution and discussionhere is the solution for the entire classwith the new method included import operator class bibliography(object)def __init__(selfentrieslist)s... |
12,372 | work--surface domain management what the write bibliog alpha method illustrates about oop here toolet' ask how would we have written function that wrote out an alphabetized bibliography in procedural programmingprobably something like the following sketchdef write_bibliog_function(arrayofentries)[open output filefor in... |
12,373 | work--surface domain management cannot also like the example because all of us have had to write bibliographyand the idea of "sources(booksarticlesvery nicely lends itself to being thought of as an "object but can the oop way of thinking help us in decomposing geosciences problemin this sectionwe consider class for man... |
12,374 | work--surface domain management hintan example may help with regards to what ' asking for with respect to the - arrays if lon= arange( and lat= arange( )then the lonall instance attribute would be[[ [ [ [ ]and the latall instance attribute would be[[ [ [ [ ]solution and discussionthe two solutions described below (with... |
12,375 | work--surface domain management import numpy as class surfacedomain(object)def __init__(selflonlat)self lon array(lonself lat array(lat[xallyalln meshgrid(self lonself latself _lonall xall self _latall yall del xallyall sowhat does this surfacedomain class illustrate about oop applied to the geosciencespretend you have... |
12,376 | class account(object)'' class for objects representing an account ''methods def withdraw(selfamount)self balance -amount def deposit(selfamount)self balance +amount def print_info(self)print("balance:"self balanceif __name__ ="__main__"annesacc account(annesacc balance annesacc deposit( annesacc withdraw( annesacc prin... |
12,377 | when operating on instance objectsyou should always use the first waybecause it leaves the job to look up the class to python and your code will be more flexible this will become clear later when we talk about inheritance constructors are useful for initialization the code for the class as written above is not very rob... |
12,378 | object is automatically assigned to the self parameterand inside the constructor methodwe can now assign the necessary attributes to the object the python statement annesacc account( "anne"triggers the following steps new object is created from the account class and assigned to the variable annesacc the constructor met... |
12,379 | manipulate attributes only via instance methods it was said earlier that assigning value to an object' attribute like this is bad stylestefansacc balance in oopan important principle is the one of data encapsulationwhich means that the attributes of an object should be 'hiddenfrom manipulations from 'outside( from the ... |
12,380 | provide for changing attributes by defining setter methods sometimesan attribute has to be changed completely assumefor tax reasonsit is preferable for stefan to change the account holder to its wife because we said that assigning value to an attribute from the outside like stefansacc holder "andreais bad stylewe provi... |
12,381 | string representations of objects oftenit is useful to have meaningful string representation of an object if we tell python to print an objectfor instance print(annesacc)python gives the cryptic answer "insteadwe would rather have string representation that really tells us what' going on with the attributes of the obje... |
12,382 | classes are objectstoo in pythonclasses are objectstoo they are created when defining class using the class statement after defining the account classexactly one class object for the account class becomes available each time we call this class ( annesacc account())we create new instance object of this class the object ... |
12,383 | assigns the object on which the method was called to this self parameter so this is what happens herein line we create the object annesacc from the account class the object annesacc is linked to the account classwhich provides the three instance methods mentioned above in line we add an attribute called balance to the ... |
12,384 | class account '' class representing an account '' class attributes num_of_accounts constructor def __init__(selfnumperson) self balance self number num self holder person account num_of_accounts + methods main part of the program if __name__=="__main__" print(account num_of_accounts"accounts have been created " annesac... |
12,385 | so farso good in the following casehoweverit gets tricky and we have to program carefully in order to avoid bugs annesacc num_of_accounts account num_of_accounts annesacc num_of_accounts stefansacc num_of_accounts in line we assign new instance attribute to the annesacc object it just happens to have the same name as t... |
12,386 | class account '' class representing an account '' class attributes num_of_accounts @staticmethod def accounts_info() print(account num_of_accounts"accounts have been created " if __name__=="__main__" call static method account accounts_info(we can also call class methods on objects of the classfor instance annesacc acc... |
12,387 | composition/aggregation recall that each value in python has typee has the type float or 'pythonhas the type str (=stringif we create an objectit also has typewhich is the class from which it was created we can check the type of an object using the type function stefansacc account( "stefan" type(stefansacc the type of ... |
12,388 | in uml class diagramswe can show that one class has an attribute whose type is another class using line that connects the two classes the diamond symbol shows that the account class uses the person class in the case of compositionthe diamond symbol is filled (blackplease note that uml class diagrams show the class desi... |
12,389 | both the savings account and the checking account are some type of account we can deposit money into either account type the account statements to be printed out are the same for the two account types the savings account and the checking account both have the following attributesaccount number account holder balance th... |
12,390 | derived classes provide for special needs let' turn to the savings accounts in factthey are specialized case of the account class we have just written nextwe are going to write class called savingsaccount which extends the account classor is derived from it this basically means that all functionality that is available ... |
12,391 | even simplerwhen calling annesacc deposit( )python starts looking for deposit method at the annesacc objectbut doesn' find one there it then looks at the class from which the object was createdwhich happens to be savingsaccount it doesn' find the method there eitherso it continues looking for the class in the superclas... |
12,392 | stefansacc checkingaccount( "stefan" stefansacc deposit( annesacc checkingaccount( "anne" annesacc deposit( annesacc withdraw( print(annesaccprint("trying to withdraw "cash annesacc withdraw( print("got only"cashprint(annesaccas we can seethe checkingaccount class provides constructor method init when creating an objec... |
12,393 | the image below shows the complete class hierarchy and our two account objects when creating annesaccpython looks for the constructor method in the savingsaccount classdoesn' find onand moves on to the account class it then modifies the newly created object as coded in the init method of the account class when creating... |
12,394 | this might even make sense if our bank provides many more types of accounts and in most of these accountsthe withdrawal works as defined in the account class thenmost of the classes derived from account simply default to this behaviorwhile we can provide special behavior for checking accounts subclasses can extend func... |
12,395 | in line we call the constructor method of the account class herewe need to explicitly pass on the self parameterbecause we are not calling the method 'on an object'but 'on the classby passing on the self parameterpython will know which object to operate on when it executes the constructor method of the account class in... |
12,396 | tuesday wednesday : - : introduction to python : - : exercises object oriented programming with python : - : coffee break exercises : - : control structures coffee break : - : exercises : - : : - : lunch break numpy fast array interface to python : - : functions and modules : - : exercises : - : exercises lunch break :... |
12,397 | |
12,398 | moderninterpretedobject-orientedfull featured high level programming language portable (unix/linuxmac os xwindowsopen sourceintellectual property rights held by the python software foundation python versions and is not backwards compatible with this course uses version |
12,399 | fast program development simple syntax easy to write well readable code large standard library lots of third party libraries numpyscipybiopython matplotlib |
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