Object oriented programming in python:

Author: Dr. Rahul Remanan

CEO and Chief Imagination Officer

Moad Computer

Objects are an encapsulation of variables and functions into a single entity.
Objects get their variables and functions from classes.
Classes are essentially a template to create your objects.

Part 01 -- Functions in python:

Just add two numbers:



In [1]:

    
a = int(input())
b = int(input())



In [2]:

    
print (a+b)

Explicitly calling garbage collection to free-up working memory:



In [3]:

    
import gc

del a
del b
gc.collect()









    Out[3]:





221

A very basic python function:

A function to add two numbers.
Uses positional argument.



In [4]:

    
def add_function(a,b):
  print ('Calculating the sum of: ' + str(a) + " , " + str(b))
  return (a+b)

The input() helps user pass an input value.



In [5]:

    
input_1 = int(input())
input_2 = int(input())



In [6]:

    
result = add_function(input_1, input_2)









    



Calculating the sum of: 56 , 65



In [7]:

    
print (result)

Explicitly freeing-up working memory and calling garbage collector:

Object oriented programing is memory efficient.



In [8]:

    
import gc

del input_1
del input_2
del result

gc.collect()









    Out[8]:





115

Another basic python function:

This is a function to add two numbers.
Uses keyword arguments instead of positional arguments.
The function takes two decimal values instead of two integer values in the function above.
Explicit error messages.



In [9]:

    
def add_function(input_1=None, input_2=None):
  if input_1 and input_2 !=None:
    print ('Calculating the sum of: ' + str(input_1) + " , " + str(input_2))
    return (a+b)
  else:
    print ('Nothing to do here ...')
    print ('Ensure add_function passes two keyword variables: input_1 and input_2 ...')



In [10]:

    
a = float(input())
b = float(input())



In [11]:

    
result = add_function(input_2=b, input_1=a)









    



Calculating the sum of: 3.14 , 5.65



In [12]:

    
print (result)









    



8.790000000000001

Explicit error message looks like this:



In [13]:

    
result = add_function(input_1=a)









    



Nothing to do here ...
Ensure add_function passes two keyword variables: input_1 and input_2 ...

Python is an “object-oriented programming language.” This means almost all the code is implemented using a special construct called classes. Programmers use classes to keep related things together. This is done using the keyword “class,” which is a grouping of object-oriented constructs.

Define a very basic class in python:

Contains a variable called "some_variable".
Contains a function called "some_function".



In [14]:

    
class some_class:
    some_variable = "Some string inside python class."
    def some_function(self):
        return ("This is a message inside the class.")

Assign an object to the class:

To assign the above class(template) to an object(variable), do the following:



In [15]:

    
some_object = some_class()

Accessing object variables:

To access the variable inside of the newly created object object_name.variable_name.



In [16]:

    
print(some_class.some_variable)









    



Some string inside python class.



In [17]:

    
print(some_object.some_variable)









    



Some string inside python class.



In [18]:

    
some_object.some_variable = 'This is the modified variable.'



In [19]:

    
print (some_object.some_variable)









    



This is the modified variable.

Accessing object functions:

To access the function inside the newly created object the syntax is: object_name.function_name().



In [20]:

    
print(some_object.some_function())









    



This is a message inside the class.

Importance of object oriented programing:

Object oriented programing helps create multiple different objects.
They are of the same class with the same variables and functions defined.
Each of those objects contain independent copies of the variables defined in the class.
If another object with the "some_class" class is defined, then the string in the variable can be changed as follows:



In [21]:

    
first_object = some_class()
second_object = some_class()



In [22]:

    
second_object.some_variable = "Modified variable string for some_class."



In [23]:

    
print(first_object.some_variable)
print(second_object.some_variable)









    



Some string inside python class.
Modified variable string for some_class.

Accessing object functions:

To access a function inside of an object in python, the notation similar to accessing a variable.



In [24]:

    
print(first_object.some_function())









    



This is a message inside the class.

Part 03 -- Constructor or initializer in python:

The init function is called a constructor, or initializer.
Construcor or initializer is automatically called when you create a new instance of a class.
init doesn't initialize a class, it initializes an instance of a class or an object.

A slightly more complex example of object oriented programing:

Uses a constructor for variables "name" and "type".
Uses a class variable, "kind".
Has an object function, "color".



In [25]:

    
class Dog:
  kind = 'I am a dog. According to scientists, I belong to a species called Canis lupus, under the sub-species familiaris.'
  
  def __init__(self, name =  None, type = None):
    self.name = name
    self.type = type

  def dog_color(self, color = None):
    if color and self.name and self.type != None:
      color = color.lower()
      if color == ('pink'):
        print ("Your dog " + str(self.name) + "'s " + color + " color is so cute ...")
      elif color == ('blue'):
        print ("Your dog " + str(self.name) + "'s " + color + " color makes it look like a smurf ...")
      else:
        print ("Your dog: " + str(self.name) + "'s " + "color is: " + color + ".")
    else:
      print ("Nothing to do here ...")
      
  def my_dog(self):
    if self.name and self.type != None:
      print ("Your dog " + str(self.name) + " is: " + str(self.type))
    else:
      print ("Nothing to do here ...")



In [26]:

    
my_dog = Dog()



In [27]:

    
my_dog.name = 'Puppy'



In [28]:

    
my_dog.type = 'Maltese'



In [29]:

    
print(my_dog)









    



<__main__.Dog object at 0x03D8FF10>



In [30]:

    
print(my_dog.name)









    



Puppy



In [31]:

    
print(my_dog.kind)









    



I am a dog. According to scientists, I belong to a species called Canis lupus, under the sub-species familiaris.



In [32]:

    
print(my_dog.type)









    



Maltese



In [33]:

    
my_dog = Dog(name = 'Puppy', type = 'Maltese')



In [34]:

    
my_dog.my_dog()









    



Your dog Puppy is: Maltese

An object can store any random variable:

An object can store any variables, not necessarily those sepcified in the class.



In [35]:

    
my_dog.hello_world = "Hello World"



In [36]:

    
my_dog.hello_world









    Out[36]:





'Hello World'

Accessing an object function that also takes a keyword argument:



In [37]:

    
my_dog.dog_color(color = 'Pink')









    



Your dog Puppy's pink color is so cute ...



In [38]:

    
my_dog.dog_color(color='Blue')









    



Your dog Puppy's blue color makes it look like a smurf ...

Change the values of a variable in an object:



In [39]:

    
my_dog.name = "Cute Puppy"



In [40]:

    
my_dog.my_dog()









    



Your dog Cute Puppy is: Maltese



In [41]:

    
my_dog.dog_color(color='Black')









    



Your dog: Cute Puppy's color is: black.

Object oriented programming in python:

Author: Dr. Rahul Remanan

CEO and Chief Imagination Officer

Moad Computer

Part 01 -- Functions in python:

Just add two numbers:

Explicitly calling garbage collection to free-up working memory:

A very basic python function:

Explicitly freeing-up working memory and calling garbage collector:

Another basic python function:

Explicit error message looks like this:

Part 02 -- Classes in python:

Define a very basic class in python:

Assign an object to the class:

Accessing object variables:

Accessing object functions:

Importance of object oriented programing:

Accessing object functions:

Part 03 -- Constructor or initializer in python:

A slightly more complex example of object oriented programing:

An object can store any random variable:

Accessing an object function that also takes a keyword argument:

Change the values of a variable in an object: