Object-Oriented Programming Concepts

Procedural Programming

• Procedural programming involves writing programs using functions that execute specific tasks.
• Procedures operate on data items separate from the procedures themselves.
• Data is frequently passed between procedures.
• The focus is creating procedures operating on program data.

Object-Oriented Programming (OOP)

• OOP emphasizes creating objects.
• An object is an entity containing data and procedures.
• Data attributes are known as data attributes; procedures within the object are called methods.
• Methods perform operations on the data attributes.
• Encapsulation is combining data and code into a single object.

Components of OOP (Object)

• Objects, depicted as illustrations of an apple, a car, and a clock.

Attributes

• Illustrations of cars, showing different attributes (e.g., color, type).

Behaviors (Methods)

• Illustrations of a car, showing actions like starting or stopping the engine.

Defining an Object

• An object is defined by its attributes (its state) and its behaviors (or methods, what it can do).

Components of OOP (Class)

• A Class is used to create an object, similar to a blueprint for a house or a cookie cutter.
• It describes what the object will be.
• A Class is not the object itself; it is a definition or a blueprint.
• It's a generic object definition.

Car Class Example

• A Car Class is presented with attributes like Make, Model, and Color alongside methods for actions like Park, Start, and Accelerate.
• Instances of a Car Class are shown as examples of Volkswagen Beetle, Audi A8, and BMW 330i.

Encapsulation

• Encapsulation involves combining data and code within a single object in a way that protects from accidental data corruption.
• Data attributes are hidden inside the object.
• Access to these attributes is restricted, only available via object methods.
• Outside code doesn't need to know the object's internal structure.

Object Reusability

• Objects can be reused in multiple programs.
• For example, a 3D image object can be used in architecture and game programming.

An Everyday Example (Clock Object)

• Data attributes for a clock include attributes for the hour, minute, and second.
• Example data attributes: current_second (value 0-59), current_minute (value 0-59), current_hour (value 1-12), alarm_time, and alarm_is_set (True or False).

Public Methods

• Public methods allow external code to access or manipulate object attributes.
• Examples in a clock application could include setting the alarm time by pressing a button or turning it on/off.

Private Methods

• Private methods are used for the object's inner workings, typically not accessible from external code.

Classes definition

• Defines a class' data attributes and methods.
• Uses the format class ClassName
• Class names start with an uppercase letter.
• Methods are like normal Python functions; each method requires a self parameter.

Initializer method

• Automatically executed when a class instance is created
• Initializes needed attributes in the object.
• Formatted as def init(self:...)
• Usually the first method defined in the class and is executed immediately when an object instance of the class is created.

Class Definitions (continued)

• To create a new class instance, call the initializer method. (e.g. my_instance = ClassName()).
• To access a method of the class instance use dot notation, (e.g., my_instance.method()).

Car Class Example (Code)

• Python code of a car class showing methods init, drive, and stop.

Coin Class Example (Code)

• Python code of a coin class demonstrating methods: init, toss and get_sideup.

Hiding Attributes in Modules

• An object's data attributes should be private.
• Two underscores (__) in front of an attribute name (e.g., __balance) makes it private.
• This convention hides the attribute from outside code, preventing accidental corruption, protecting integrity and maintaining data safety.

Storing Classes in Modules

• Classes can be stored inside modules that end with .py
• Modules can be imported into other programs to use the class definitions they contain.

The BankAccount Class

• The BankAccount class is stored in a module bankaccount
• This class simulates a bank account, allowing the user to define a starting balance, make deposits, make withdrawals and get the current balance.

BankAccount Methods

• Class methods, such as init, can have multiple input parameters, such as a starting balance.
• Specific parameters for each method help define the actions performed on object attributes.

### Class Methods with Parameters

• Class methods, such additional parameters, are needed.to create a class instance; an example is a BankAccount object created with a balance.
• Methods can have more parameters (e.g., the amount to be deposited in a deposit method).

The str Method

• The str method displays the object's state or current values.
• This str method displays a representation of the object's attributes.
• It is automatically called by the print function.

Instance Attributes

• Instance attributes are objects from a class, and belong to a specific class instance.
• They are created when a class method uses the self parameter to create an attribute.
• Each instance has its own set of attributes.

Passing Objects as Arguments

• Methods and functions often need to accept objects as their arguments.
• When an object is passed as an argument, a reference to that object is passed.
• The method or function has access to the actual object's attributes and can change them.

Storing Objects in a Dictionary

• Classes (like Contact) can store data like names, phone numbers, and email addresses.
• Methods help manage the data (e.g., setting or retrieving data such as phone numbers).

Techniques for Designing Classes (UML Diagrams)

• UML diagrams are standard graphical representations of object-oriented systems.
• A class UML box usually has three sections: the class name, data attributes, and methods.
• There are detailed UML diagrams for Coin, CellPhone, Customer, and ServiceQuote examples.

Finding Classes in a Problem

• The first goal in object-oriented programming is identifying classes in the problem domain.
• Examine the given description of the problem domain and identify nouns.
• Refine the list of nouns to include only relevant classes.

Writing a Problem Domain Description

• A description outlines the actions and desired behavior of the program.

Listing Nouns in a Problem Domain Description

• Identify all the nouns and noun phrases in the problem description to gather potential classes for object-oriented programming.

Refining the List of Nouns: Removing Duplicates & Unnecessary Classes

• Eliminate repeated nouns or synonymous words.
• Discard nouns representing simple data values (e.g., dates, sizes).

Test your understanding of Object-Oriented Programming (OOP) concepts such as classes, objects, encapsulation, and methods. This quiz will help reinforce your knowledge of how data attributes and procedures are managed within objects. Dive into the specifics like object reusability and data hiding.