Class anatomy: attributes and methods

Introduction to Object-Oriented Programming in Python

George Boorman

Curriculum Manager, DataCamp

A Customer class

class Customer:

    # Code for class goes here

    pass

class <name>: starts a class definition
Code inside class is indented
Use pass to create an "empty" class

c_one = Customer()
c_two = Customer()

Use ClassName() to create an object of class ClassName

Add methods to a class

class Customer:  

    def identify(self, name):
        print("I am Customer " + name)

Method definition = function definition within class
Use self as the first argument in method definition

cust = Customer()
cust.identify("Laura")

I am Customer Laura

Ignore self when calling a method on an object

class Customer:  
    def identify(self, name):
        print("I am Customer " + name)

cust = Customer()
cust.identify("Laura")

What is self?

Classes are templates
self should be the first argument of any method
self is a stand-in for a (not yet created) object
cust.identify("Laura") will be interpreted as Customer.identify(cust, "Laura")

We need attributes

OOP bundles data with methods that operate on data
- Customer's' name should be an attribute

$$\text{\Large{Attributes are created by assignment (=) in methods}}$$

Add an attribute to class

class Customer:  
    # Set the name attribute of an object to new_name
    def set_name(self, new_name):

        # Create an attribute by assigning a value
        # Will create .name when set_name is called
        self.name = new_name

# Create an object
# .name doesn't exist here yet
cust = Customer()

# .name is created and set to "Lara de Silva"
cust.set_name("Lara de Silva")

print(cust.name)

Lara de Silva

Old version

class Customer:  



    # Using a parameter
    def identify(self, name):
        print("I am Customer" + name)

cust = Customer()

cust.identify("Eris Odoro")

I am Customer Eris Odoro

New version

class Customer:  
   def set_name(self, new_name):
       self.name = new_name


    # Using .name from the object it*self*
    def identify(self):
        print("I am Customer" + self.name)

cust = Customer()
cust.set_name("Rashid Volkov")
cust.identify()

I am Customer Rashid Volkov

Let's practice!

Introduction to Object-Oriented Programming in Python