Everything in python are objects

Objects are instances of classes

This is how to create an object



In [4]:

    
class Student(object):
    def __init__(self, nameInput):
        self.name = nameInput



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student1 = Student('Casey')



In [7]:

    
student1.name









    Out[7]:





'Casey'

In the above

Student is a class By convention, use captilization

student1 is an object student1 is the instance of the class Student

Classes have attributes Attributes are like data

init is used to initialize object attributes self refers to the instantiated object

By convention, the above is usually defined as



In [8]:

    
class Student(object):
    def __init__(self,name):
        self.name = name

# note how nameInput has been changed to name



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student1 = Student('Casey')
print student1.name









    



Casey



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student2 = Student(name='Varma')
print student2.name









    



Varma

class

We have class

objects

We have instantiated objects

attributes

We have class attributes

methods

Then we have methods

Methods are class functions



In [19]:

    
class Rectangle(object):
    def __init__(self, height, width):
        self.height = height
        self.width = width
        
    def area(self):
        return self.height*self.width



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rect1 = Rectangle(1,2)
print 'Area is', rect1.area()









    



Area is 2



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class Circle(object):
    pi = 3.14

    # Circle get instantiated with a radius (default is 1)
    def __init__(self, radius=1):
        self.radius = radius 

    # Area method calculates the area. Note the use of self.
    def area(self):
        return self.radius * self.radius * Circle.pi

    # Method for resetting Radius
    def setRadius(self, radius):
        self.radius = radius

    # Method for getting radius (Same as just calling .radius)
    def getRadius(self):
        return self.radius


c = Circle()

c.setRadius(2)
print 'Radius is: ',c.getRadius()
print 'Area is: ',c.area()









    



Radius is:  2
Area is:  12.56

Notice methods are functions and are called as function

class object attributes

These are common to all objects of a class



In [25]:

    
class Student(object):
    
    # class object attribute
    college = 'A&M'
    
    def __init__(self,name):
        self.name = name



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student3 = Student('Rahman')
print student3
print student3.name
print student3.college









    



<__main__.Student object at 0x10ea74ad0>
Rahman
A&M

Then there is inheritance and special methods

Inheritance

There is a base class and a derived class.

Base class

gets attributes and methods from the base class
can overwirte attributes from the base class
can have additional attributes compared to the base class

Here is a Base class



In [42]:

    
class Animal(object):
    def __init__(self):
        print 'Animal created'
        
    def whoAmI(self):
        print 'Animal'
        
    def eat(self):
        print 'Eating'
        
    def __del__(self):
        print 'del is a standard python object'
        print 'Here del is used as a special method'
        print 'Animal destroyed'



In [43]:

    
anim1 = Animal()
print anim1.whoAmI()
print anim1.eat()
del anim1









    



Animal created
Animal
None
Eating
None
del is a standard python object
Here del is used as a special method
Animal destroyed

strangely 'None' is getting printed. This is due to not returning in methods function call

Check stackoverflow discussion Also Tips on markdown

Anyways, here is a derived class



In [45]:

    
class Dog(Animal):
    def __init__(self):
        print 'Dog created'
        
    def bark(self):
        return "Woff woof"
        
    def whoAmI(self):
        print 'I am a dog.'
        return 'Did you expect Animal to print?'
        
dog1 = Dog()
print dog1.bark()
print dog1.whoAmI()
print dog1.eat()









    



Dog created
del is a standard python object
Here del is used as a special method
Animal destroyed
Woff woof
I am a dog.
Did you expect Animal to print?
Eating
None

Notice

Base class

gets attributes and methods from the base class
can overwirte attributes from the base class
can have additional attributes compared to the base class

del

del is used as a special method



In [47]:

    
print 'GOOD luck!'









    



GOOD luck!



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