Introduction to python

Classes

Mauricio Sevilla

email= j.sevillam@uniandes.edu.co

04.03.19

This is the last class of the introductory part of python, then we'll explore the intermediate level where libraries such as numpy and matplotlib.

That is why this topic is so important, it gathers together all the previous concepts and tools.

As we have mentioned during the class, python is a object oriented based language and today we will understand what does it mean.

The missing structure is called classes

In [1]:
 class animal:
        def __init__(self,name,age,specie):
            self.name=name
            self.age=age
            self.spe=specie
In [2]:
animalito=animal('Comino',2,'Dog')
animalito.spe
Out[2]:
'Dog'
In [3]:
A=animal('Scooby',2,'Dog')
In [4]:
A.age=3
In [5]:
A.age
Out[5]:
3
In [6]:
Zoo=[]
In [7]:
animals=['Dog','Cat','Mouse']
names=['Scooby','Tom','Jerry']
In [8]:
for i in range(len(animals)):
    Zoo.append(animal(names[i],1,animals[i]))
In [9]:
print(Zoo)

[<__main__.animal object at 0x1040846a0>, <__main__.animal object at 0x1040846d8>, <__main__.animal object at 0x104084710>]

Take a look at this structure

In [10]:
print(Zoo[0])

<__main__.animal object at 0x1040846a0>

What do you think it means?

We saved there a Dog named Scooby and 1 year old!,

But, What if....

In [11]:
print(Zoo[0].name,Zoo[0].spe,Zoo[0].age)

Scooby Dog 1

Let us construct a different example.

We are going to work on a problem we already did, Let us create ourselves!

Lets have a student class.

In [12]:
import random
random.seed(10987654321012345678910)
class student:
    def __init__(self,name,age,career,semester):
        self.name=name
        self.age=age
        self.career=career
        self.semester=semester
    def Grade(self):
        return round(random.random()*5,1)
In [13]:
Me=student('Mauricio',80,'Professor',1)
In [14]:
Me.Grade()
Out[14]:
2.2
In [15]:
Me.Grade()
Out[15]:
0.0
In [16]:
Me.Grade()
Out[16]:
3.5

Let us create a more complex class

In [17]:
 class animal2:
        "This class helps you to create an animal"
        def __init__(self,name,age,specie,talk):
            self.name=name
            self.age=age
            self.spe=specie
            self.speech=talk
        def talk(self):
            return self.speech
        def sit(self):
            if(self.spe=='Dog'):
                return 'Sitted!'
            else:
                return'Nee'
In [18]:
Zoo2=[]
animals=['Dog','Cat','Mouse']
names=['Scooby','Tom','Jerry']
ages=[1,2,3]
speeches=['Woof','Miau!','Cheese!']
In [19]:
for i in range(len(animals)):
    Zoo2.append(animal2(names[i],1,animals[i],speeches[i]))
In [20]:
print(Zoo2[-1].talk())

Cheese!
In [21]:
print(Zoo2[2].name)

Jerry
In [22]:
print(Zoo2[2].sit())

Nee
In [23]:
print(Zoo2[1].talk())

Miau!
In [24]:
?animal2

Inheritance

Let see some examples of what does inheritance means while programming.

For example, my family as a class

In [25]:
class Sevilla:
    def __init__(self,name,age):
        self.name=name
        self.age=age
    def hair(self):
        return 'Black' #We all have black hair
    def eyes(self):
        return 'Brown' #We all have Brown eyes
    def LastName(self):
        return 'Sevilla' #We all have the same last name

If someday i have a son/daughter, for sure he/she will have some features I do, so

In [26]:
class SonDaugther(Sevilla):
    def __init__(self,name):
        self.na=name
In [27]:
Me=Sevilla('Mauricio',80)
In [28]:
MySon=SonDaugther('son')
In [29]:
print(MySon.na)

son
In [30]:
print(MySon.hair())

Black
In [31]:
print(MySon.eyes())

Brown
In [32]:
print(MySon.LastName())

Sevilla
In [33]:
class SonDaugther2(Sevilla):
    def __init__(self,name):
        Sevilla.__init__(self,'Nombre',10)
        self.na=name
In [34]:
MySon2=SonDaugther2('name')
In [35]:
MySon2.age
Out[35]:
10