Objects, classes, methods

Question 1

what are Objects and Classes?

Answer 1

• everything in python is an object: value, function, variable, etc
• everytime we create a variable we are making a new object
• every object has a type or class associated with it (str, int, float, list etc)
• objects are instances of a class (type)
• ‘instance’ and ‘object’ used interchangeably

alex = Tutrle(0,0)
alex is instance of Turtle class

Question 2

Object-Oriented Programming

Answer 2

Class (i.e Person)
Attributes (i.e name, age, city, gender)
Methods (i.e eat, study, sleep, play)

general form of a Class:

class CamelCase:

CONSTRUCTOR
def __init__(self, param1, param2, …)
…
body

METHOD
def method1(self, parameters):
body

Question 3

Instantiate

Answer 3

creating (constructing) an instance of a class

i.e
alex = Turtle(0,0)

Question 4

Methods (Functions)

Answer 4

• a function defined in a class
• when defining method, first parameter refers to instance being manipulated(self)
• method call automatically inserts an instance reference as first argument
• defining methods without self will not cause an error, error only occurs when u call function

def up(self):
body

def goto(self, x, y):
body

to call:
instance_of_class.method()
i.e
ben.up()

Question 5

Attributes (Data)

Answer 5

• a variable bound to an instance of a class

alex = Turtle(0,0)

to access:

alex. x
alex. y

Question 6

Constructor

Answer 6

• responsible for setting up the initial state of a new instance

def __init__(self, x, y):

self. x = x
self. y = y

__iniit__ method is automatically run during instantiation

Question 7

self

Answer 7

• reference to the instance of the class
• at the time of designing the class we don’t know what these instance neames will be so use self

i.e urmom is self

Outside Class

urmom. attribute
urmom. method

Inisde Class

self. attribute
self. method

Question 8

Encapsulation

Answer 8

• core of OOP is organization of the program by encapsulating related data and functions together on an object
• keeping data and the code that uses it in one place and hiding the details of exactly how they work tgt

Question 9

Objects as Data Attributes of Classes

Answer 9

-objects are programmer-created data types that can be used just like other data types

i.e
create a Sqaure class and use Point instances and attributes

class Square:

def __init__(self, x1, x2, y1, y2):

self. lower_left = Point(x1, y1)
self. upper_right = Point(x2, y2)

Question 10

Printing Information

Answer 10

• to not have to write a print statement when we want to display attribute info
  use: def __str__(self):

def __str__(self):
“””
(self) -> str
Return the coordinates of the Point
“””
return “(“ + str(self.x) + “,” + str(self.y) + “)”

my_point = Point()
print(my_point)
–> (0,0)