Object Oriented Programming

Question 1

Why is object oriented programming important?

Answer 1

It is something that has revolutionized the way programming is done today. It also is great for code maintenance

Question 2

In OOP classes have what two types of characteristics?

Answer 2

Attributes and Methods. What is has and what is can do. Variables inside a class and functions inside a class

Question 3

Using the class, what can you create?

Answer 3

You can create different instances / different objects

Question 4

Say you don’t want an instance of an object to have certain attributes?

Answer 4

You can use the private functionality to make the attribute or function not available to the object

Question 5

Say you want to branch and upgrade the barrack?

Answer 5

You can utilize inheritance, naming the parent barrack as the parent class to inherit attributes

Question 6

Describe ‘user’ use case for OOP

Answer 6

Let’s say we want to create a web app and will need lots of instances of users. We can start from scratch and create each user, but this clearly isn’t going to scale. Maybe we could have some sort of system for creating a user based upon a set of instructions. What attributes and actions are common across all instances of users?

It may seem like having a blueprint means that each user must be the same. The blueprint will only dictate what qualities (attributes) we must track for each user and what each user object should be able to do. When a new user is created, a value must be filled in for the name attribute.

Question 7

How do you create a class in Python?

Answer 7

You can create by first keyword class then the name of your class followed by (Object)

class ClassName(object):

Question 8

Classes include two types of things

Answer 8

Attributes - Characteristics shared by all instances of the class type. Take our User class, for example. All users have a name and an email. You might be wondering how each user can have a differet name and email

Methods - Actions that an object can perform. A user, for example, might be able to make a purchase. A method is like a function that belongs to a class. It’s some instructions that will only work when called on an object that has been created from that class.

Storage of information and ability to execute some logic

Question 9

Using a person example, walkthrough attributes and methods

Answer 9

I am a person. Like other people I have hair. Like other people I can walk

Question 10

What is implicit passage of self?

Answer 10

Any method we create we need to include

Question 11

What is self?

Answer 11

Self is essentially a placeholder for the object. We can change the STATE of the SINGLE object by making modifications only to self. The self parameter includes all the information about the individual object that has called the method. Without self, every time we changed one’s object’s attributes, we’d change the attribute for ALL the items of that type.

Question 12

__init__()

Answer 12

Python’s __init__method is something that’s known as a magic method. Magic methods are automatically created and sometimes invoked when a new instance of a class is created. One method you’ll be working with

Question 13

what is __init__() useful?

Answer 13

Because it allows us to set some attributes when a new instance is created. Because we know that the init method will run immediately.

Question 14

Explain how to chain methods

Answer 14

If each method returns self, then you can chain your methods together.

Question 15

What is DRY

Answer 15

don’t repeat yourself

Question 16

What are modules?

Answer 16

Simply python files with the .py extension which implement a set of functions. They are imported using the import command

Question 17

How do we use a function within a module?

Answer 17

We use dot notation after the module name
urllib.urlopen(..)

Question 18

How do you create your own module?

Answer 18

Create a new .py file with the module name in the same directory as the file that will import the module. Then we import it using the import command and the Python file name

Question 19

What are standard Built In Modules

Answer 19

Python comes with a library of standard modules. Some modules are built into the interpreter; these provide access to operations that are not part of the core of the language but are nevertheless built-in, either for efficiency or to provide access to operating system primitives such as system calls.

Question 20

Are some modules exclusive to a platform?

Answer 20

Yes, like winreg module is only for Windows system. However, sys is built into every Python interpreter

Question 21

What are two important modules that come in handy when exploring modules in Python….what are they?

Answer 21

dir and help functions.

Question 22

What is a package?

Answer 22

A module is a single file (or files) that are imported under one import. A package is a collection of modules in directories that give a package hierarchy

Question 23

What must be in the package folder?

Answer 23

Each package in Python is a folder which MUST contain a special file called __init__.py. This file can be empty, and it indicates that the directory containing it is a Python package, so it can be imported the same way a module can be imported

Question 24

What are two ways to import a module within a package?

Answer 24

import my_modules.test_module
or
from my_modules import test_module

Question 25

How can you determine which modules to export as an API while keeping other moduesl internal?

Answer 25

The __init__.py file can also decide which modules this package will export as an API, while keeping other modules internal, by overriding the __all__variable, like so:

__init__.py:
__all__ = [“test_module”]

Question 26

What is inheritance

Answer 26

Is forming new classes using classes that have already been defined. In other words, it allos one class to take on some or even all of its attributes and methods from a parent class.

Question 27

What are the benefits of inheritance?

Answer 27

It allows one class to take on some or even all of its attributes and methods from a parent class. Code reuse and reductio of complexity of a program. THE DERIVE CLASSES (DESCENDANTS) CAN OVERRIDE OR EXTEND THE FUNCTIONALITY OF BASE CLASSES (ANCESTORS)

Question 28

When we defined each of our classes, we typed Bike(Vehicle), Car(Vehicle), Airplane(Vehicle). How could you read this in plain engligh?

Answer 28

“Make a class BIke/Car/Airplane that INHERITS from Vehicle”

This is known as implicit inheritance which allows us to use inherited attributes and methods of the Vehicle(parent) class in our new subclasses

Question 29

What is you want to pass in a variable number of arguments, or want to capture multiple arguments into a single parameter?

Answer 29

Placing an asterisk before the name of the parameter after the ‘normal’ parameters does just that. The asterisk is called a ‘splat’ operator. Bundle the remaining arguments into a new TUPLE, which is then assigned to that parameter

Question 30

What is super and what is it’s syntax?

Answer 30

Sometimes in your OOP you will want to create updates versions of methods that are defined in the parent class, because in addition to your custom code, you want specifically to call the parent implementation of that method as well (or instead). In these cases, you would reference that parent object with the keyword ‘super’

super(ChildClassName, self).parent_method()

Question 31

How can we change the child class attributes after it has inherited?

Answer 31

One thing we may want to do is call the Parent class’s __init__ method, but also have our Child class change attributes defined by its Parent class.