You use the phrase is-a when you talk about objects and classes being related to each other by a class relationship. You use has-a when you talk about objects and classes that are related only because they reference each other.

Can you give me an example shows the meaning ??

i can't understand what does he mean with ! related to each other by a class relationship & because they reference each other.

&

def __init__(self, name):

self.name = name

why we must type this line ?? (self.name = name)

Thanks all

I can't think of any practical example for "is-a" in programming right now, but conceptually, take this:

A teacher is a human. This can be modelled by having a class inheritance:

class Human

class Teach(Human)

A teacher also might have a schoolbook. This is a "has-a" relation, as the teacher doesn't derive of schoolbook, but instead uses it:

class Human

class Schoolbook

class Teacher(Human)

    def __init__(self)
        self.book = Schoolbook()

This is achieved via aggregation, as I've shown here. Thats whats meant by "reference each other". The Teacher references a Schoolbook, in that it posses & possibly uses it.

def __init__(self, name):

self.name = name

why we must type this line ?? (self.name = name)

__init__ is a function, executed with a bunch of parameters. at that point "name" is merely a local variable, but you want to use it as a class variable. So in order to do that, you have to assign the local "name" variable to the instance of the class ("self"), by calling "self.name" (this instances "name" variable) "= name" (is assigned the local "name").

Ty

but please answer this question

class Teacher(Human)

    def __init__(self,name)
        self.name=name

now we are talking about the object that object have name etc

so you are talking about the human not the teacher ,, between the bracket i type the object right ??

so now saying human has-a name not teacher right ?

so you are talking about the human not the teacher ,, between the bracket i type the object right ??

so now saying human has-a name not teacher right ?

In the bracket, you type the current classes parent class, so thats "is-a". See https://docs.python.org/2/tutorial/classes.html chapter 9.5.

must be defined in a scope containing the derived class definition

but see :

class product(object):

why we type object !!

where i type object !

Sorry for hard understanding

.................

but i think in

class Teacher(Human)

    def __init__(self,name)
        self.name=name

it was inheritance

but in ..

class product(object):

i here type the object Because (it is not an inheritance from another class)

Thanks

Phil...is that you?

sorry for hard understanding

hil...is that you?

i shouldn't ask sorry

but in ..
class product(object):
i here type the object Because (it is not an inheritance from another class)

`product` inherits `object`, which is a built-in class in Python.

Sorry for hard understanding smile.png

stop apologizing, just get your shit together, geez...

Hahaha, Beer, play nice now.