Encapsulation:-
- Concept of binding or grouping related data members along with its related functionalities is known as Encapsulation
Example:-
For Customer
cname,caadr,caccno
and cbal are variables
deposit( ),withdraw( ),transfer( )
and balenq( ) are methods
For Employee
eid,ename,eaddr,esal
and email are variables
da( ),ta( ),hra( ),pf( ),tax( )
and tsal( ) are methods
- class is a syntax of structure is used to grow related data members along with its related functionalities.
- Implement the Encapsulation practically by using class syntax.
syntax:
class <class_name>:
""" doc string
"""
..................
..................
..................
print("start")
class Test:
""" this is sample class"""
x=10
def m1(self):
print("m1 in Test")
x=Test.x+500
print("end")
t1=Test()
t1.m1()
t1.m1()
t2=Test()
t2.m1()
t2.m1()
start
end
m1 in Test
m1 in Test
m1 in Test
m1 in Test
class Test:
def m1(self):
self.x=10
t1=Test()
t1.m1()
print(t1.x)
t1.x=t1.x+5
print(t1.x)
t2=Test()
t2.m1()
print(t2.x)
t2.x=t2.x+2
print(t2.x)
t3=Test()
t3.m1()
print(t3.x)
10
15
10
12
10
Constructor:-
- Constructor is a special kind of method , which is used to initialize the non-static variables of a class at the time of creation of the Object.
- Constructor will be executed automatically.
Syntax:
def __init__(self, ...):
-------------------
-------------------
-------------------
class X:
def __init__(self): -----> constructor
print("Constructor of X")
def m1(self): ---------> method
print("In m1 of X")
x1=X( )
x1.m1( )
Constructor of X
In m1 of X
class X:
def __init__(self):
self.i=10
self.j=20
def disp(self):
print(self.i)
print(self.j)
x1=X( )
x1.disp( )
x1.i=30
x1.j=40
x1.disp( )
x2=X( )
x2.disp( )
x2.i=50
x2.j=60
x2.disp( )
10
20
30
40
10
20
50
60
class X:
def __init__(self,i,j):
self.i=i;
self.j=j
def disp(self):
print(self.i)
print(self.j)
x1=X(10,20)
x1.disp( )
x2=X(30,40)
x2.disp( )
10
20
30
40
Differences between the method and the Constructor
Methods
|
Constructors
|
Method name can be Anything or any name
|
Constructor name should be _ _init_ _
|
After creating the object if we call a method
then only method will be executed.
|
Constructor will be executed automatically
whenever we created object
|
with respect to one object one method can be called for any
number of times
|
with respect to one object one constructor
will be executed only once
|
Methods are used to represent the business
logics to perform the operations
|
Constructors are used to initialize the
non-static variables.
|
why method takes self parameter:
- when objects are instantiated,the object itself is passed in to the self parameter of the method.
Garbage Collector:-
- It is a pre-defined program which is present inside python software.
- Garbage collector removes the unused or unreferenced objects from the memory location. If the reference count of any object is 0(zero) then we call that object as a unreferenced or unused object.
- Whenever any object reference count is zero then python interpreter calls the Garbage collector and GC(Garbage collector) removes the object.
- After executing the GC more memory is available for the program so that rest of the program execution becomes faster.
class X:
def __init__(self):
print("in constructor of X")
def __del__(self):
print("in destructor of X")
x1=X( )
x2=x1
x2=X( )
x1=X( )
in constructor of X
in constructor of X
in constructor of X
in destructor of X
- Before going to delete the objects from the memory location it internally executes destructor.
- _ _del_ _ is known as a destructor.
- del is a keyword, which is used for removing the attributes.
class X:
def __init__(self):
print("in constructor of X")
def __del__(self):
print("in destructor of X")
x1=X()
x2=X()
x3=X()
del x1
del x2
del x3
in constructor of X
in constructor of X
in constructor of X
in destructor of X
in destructor of X
in destructor of X
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