Checkpoints

#7.1
Objects of the same kind are defined by using a common class. The relationship between
classes and objects is analogous to that between an apple-pie recipe and apple pies. You can
make as many apple pies (objects) as you want from a single recipe (class).

#7.2
class ClassName:
    initializer
    methods

#7.3
objName = ClassName(args)

#7.4
__init__

#7.5
self is a parameter that references the object itself. Using self, you can access object’s
members in a class definition.

#7.6
ClassName(args)
The arguments of the constructor match the parameters in the __init__ method without self.
The constructor first creates an object in the memory and then invokes the initializer.

#7.7
Initializer is a special method that is used to initialize object's data when creating object.

#7.8
dot operator(.).

#7.9
Variable i in class a isn't initialized.
Fix: a = A(x), where x is any value.

#7.10
(a) The constructor should be __init__(self).
(b) radius = 3 should be self.radius = 3.

#7.11
count is 100
times is 0

#7.12
count is 0
n is 1

#7.13
AttributeError: no attribute '__i', the i attribute is
a private data field.
To fix this we can make i public by removing the leading __
or provide getter method.

#7.14
Yes. It prints "Welcome"

#7.15
The code is not correct.
To fix this we can make on attribute public by
removing leading __ or provide getter method to
on attribute:
class A:
    def __init__(self, on):
        self.on = not on
OR
class A:
    def __init__(self, on):
        self.__on = not on
    def isOn(self,on):
        return self.__on

def main():
     a = A(False)
     print(a.isOn)

main() # Call the main function

#7.16
Making data fields private protects data and makes the class easy to maintain.
To prevent direct modifications of data fields, don’t let the client directly access data fields.
This is known as data hiding. This can be done by defining private data fields. In Python, the
private data fields are defined with two leading underscores. You can also define a private
method named with two leading underscores.

#7.17
def __methodName(parms):

#7.18
The object-oriented approach combines the power of the procedural paradigm
with an added dimension that integrates data with operations into objects.
In procedural programming, data and operations are separate, and this methodology
requires sending data to methods. Object-oriented programming places data and the operations
that pertain to them together in an object. This approach solves many of the problems
inherent in procedural programming. The object-oriented programming approach organizes
programs in a way that mirrors the real world, in which all objects are associated with both
attributes and activities. Using objects improves software reusability and makes programs
easier to develop and easier to maintain.