Object and Classes

Question 1

To create an object, you must first define a ___ that indicates what it contains

Answer 1

class

Question 2

Create a cat class in python

Answer 2

> > > class Cat:
… pass

We need to say pass to indicate this class is empty

Question 3

A _____ is a variable inside a class or object

Answer 3

attribute

Question 4

A _____ is afunction in a class

Answer 4

method

Question 5

If you want to assign object attributes at creation time, you need the special Python object initialization method

Answer 5

__init__()

> > > class Cat:
… def __init__(self):
… pass

Question 6

When you define __inti__() in a class definition, its first parameters should be named ___.

Answer 6

self –argument specifies that it refers to the individual object itself

Question 7

EXAMPLE

Answer 7

> > > class Cat():
… def __init__(self, name):
… self.name = name
…

Question 8

Create an object from the cat class

Answer 8

> > > furball = Cat(‘Grumpy’)

Question 9

Function that allows you to check is a class is derived from another class

Answer 9

issubclass()

Question 10

Child class ____ methods from parnt class

Answer 10

inherits

Question 11

You can also _____ methods in the parent class

Answer 11

override

Question 12

The child class can also ____ a metohd that was not present in parent cas

Answer 12

add

Question 13

We can override any methods including _____

Answer 13

__init__()

Question 14

Wat if child class wated to call parent method?

Answer 14

super()

Question 15

Example of using super in the initialize function

Answer 15

> > > class EmailPerson(Person):
… def __init__(self, name, email):
… super().__init__(name)
… self.email = email

Question 16

Some object-oriented languages support _____ object attributes that can’t be accessed directly from the outside. Programmers then may need to write _____ and _____ methods to read and write the values of such private attributes.
Python doesn’t have private attributes, but you can write getters and setters with obfuscated attribute names to get a little privacy

Answer 16

private, getter, setter

Question 17

The Pythonic solution for attribute privacy is to use _______

Answer 17

properties

Question 18

There are two ways to do this. The first way is to add __________________ as the final line of our previous Duck class definition:

Answer 18

name = property(get_name, set_name)

Question 19

In the second method, you add some decorators and replace the method names get_name and set_name with name

Answer 19

@property, which goes before the getter method
*@name.setter, which goes before the setter method

Question 20

You can assign attributes to _____, and they’ll be inherited by their child objects

Answer 20

classes
»> class Fruit:
… color = ‘red’
…
»> blueberry = Fruit()
»> Fruit.color
‘red’
»> blueberry.color
‘red’

Question 21

*If there’s no preceding decorator, it’s an ______ _____, and its first argument should be self to refer to the individual object itself

Answer 21

instance method

Question 22

*If there’s a preceding @classmethod decorator, it’s a _____ ______, and its first argument should be cls (or anything, just not the reserved word class), referring to the class itself.

Answer 22

class method

Question 23

*If there’s a preceding @staticmethod decorator, it’s a ______ ______, and its first argument isn’t an object or class

Answer 23

static method

Question 24

Examples of class method vs instance method

Answer 24

> > > class A():
… count = 0
… def __init__(self):
… A.count += 1
… def exclaim(self):
… print(“I’m an A!”)
… @classmethod
… def kids(cls):
… print(“A has”, cls.count, “little objects.”)
…

Question 25

The first parameter of an instance method is ____, and Python passes the object to the method when you call it

Answer 25

self

Question 26

__eq__(self,other)

Answer 26

self == other

Question 27

__ne__(self,other)

Answer 27

self != other

Question 28

__str__(self)

Answer 28

str(self)

Question 29

__len__(self)

Answer 29

len(self)

Question 30

Aggregation example

Answer 30

>>> class Bill(): ... def __init__(self, description): ... self.description = description ... >>> class Tail(): ... def __init__(self, length): ... self.length = length ... >>> class Duck(): ... def __init__(self, bill, tail): ... self.bill = bill ... self.tail = tail ... def about(self): ... print('This duck has a', self.bill.description, ... 'bill and a', self.tail.length, 'tail') ... >>> a_tail = Tail('long') >>> a_bill = Bill('wide orange') >>> duck = Duck(a_bill, a_tail) >>> duck.about()

Question 31

For example, if duck has tail and bill, and we create classes Tail and Bill, we can make tail and bill objects and provie them to the new ___ object

Answer 31

duck

Question 32

A named tuple is a subclass of tuples with which you can access values by ____ (with .name) as well as by position (with [ offset ]).

Answer 32

name

Question 33

how to import named tuple

Answer 33

>>> from collections import namedtuple

Question 34

Creating a named tuple

Answer 34

>>> from collections import namedtuple >>> Duck = namedtuple('Duck', 'bill tail') >>> duck = Duck('wide orange', 'long') >>> duck Duck(bill='wide orange', tail='long') >>> duck.bill 'wide orange' >>> duck.tail 'long'

Question 35

Creating a named tuple from dictionary

Answer 35

>>> parts = {'bill': 'wide orange', 'tail': 'long'} >>> duck2 = Duck(**parts) >>> duck2 Duck(bill='wide orange', tail='long')

Question 36

Names tuples are _____, bu you can replace one or more fileds and return another named tuple

Answer 36

immutable

Question 37

Examples of data classes

Answer 37

>> class TeenyClass(): ... def __init__(self, name): ... self.name = name ... >>> teeny = TeenyClass('itsy') >>> teeny.name 'itsy' Doing the same with a dataclass looks a little different:>>> from dataclasses import dataclass >>> @dataclass ... class TeenyDataClass: ... name: str ... >>> teeny = TeenyDataClass('bitsy') >>> teeny.name 'bitsy'