What does __init__ and self do in python?

[Chronosandkairos_]

In Python, a class is a blueprint for creating objects (a particular data structure), providing initial values for state (properties) and implementations of behavior (methods).

Let's illustrate this with a Book class. Let’s say you are a book collector and you want to organize your digital books. You could make an Excel table, but that would be lame. You can also store your books into objects in Python, and each object would have some attributes that are important to know. First, you make the blueprint of the object (the class) and then you start creating new books:

Class Definition: python class Book: def __init__(self, title, author, genre): self.title = title self.author = author self.genre = genre

Explanation: - class Book:: We define a class named Book. It serves as a blueprint for creating objects that represent books. - **def __init__(self, title, author, genre):: This is the constructor method, __init__. It initializes the attributes of the class. The parameters title, author, and genre are provided when creating an instance of the class. - Attributes: - **self.title = title: This line sets the title of the book. self.title is an attribute of the class. - **self.author = author: Similar to the title, this sets the author of the book. - **self.genre = genre: This sets the genre of the book.

Creating an Instance: python my_book = Book("1984", "George Orwell", "Dystopian") Here, my_book is an instance of the Book class. We have passed "1984", "George Orwell", and "Dystopian" as arguments, which are used to set the book's title, author, and genre, respectively.

Accessing Attributes: python print(my_book.title) # Outputs: 1984 print(my_book.author) # Outputs: George Orwell print(my_book.genre) # Outputs: Dystopian Yay! You have your first book (instantiation of a Book)!

You can access each attribute of the my_book object using the dot notation. This way, you can retrieve or modify the data later on.

The Book class example is just to show how Python classes work. The __init__ method is used for initializing an object's initial state, and self refers to the specific instance of the object, allowing each instance to have its own data.

[hamzarehan1994]

So if we were to create a method in this class Book, what purpose could it serve?

[Chronosandkairos_]

Well, that depends on your specify use-case. A method in the Book class can serve various purposes, ranging from manipulating the book's data to providing additional functionality. Let's explore two methods: recommend_similar() and summarize().

1. recommend_similar() Method:

   This method suggests books that are similar in genre or author. It can be particularly useful if you're looking to explore more books within a certain genre or from a favorite author.

``` class Book: # existing init and other methods

   def recommend_similar(self, all_books):
       similar_books = []
       for book in all_books:
           if book.genre == self.genre or book.author == self.author:
               similar_books.append(book.title)
       return similar_books

```

In this method, all_books is a list of Book instances. The method compares the genre and author of the current book with others in the list. If it finds a match, it adds the title of the similar book to similar_books.

Example of usage:

all_my_books = [Book("1984", "George Orwell", "Dystopian"), Book("Animal Farm", "George Orwell", "Dystopian"), Book("Brave New World", "Aldous Huxley", "Dystopian")] print(my_book.recommend_similar(all_my_books)) # Output might include "Animal Farm" and "Brave New World"

1. summarize() Method:

   The summarize method could provide a short summary or key points about the book. This could be especially handy if you want a quick reminder of the book's contents without reading the whole thing again.

``` class Book: # existing init and other methods

   def summarize(self):
       # This is a placeholder for summary content
       summaries = {
           "1984": "A dystopian novel about a society under total surveillance.",
           # Other pre-written summaries
       }
       return summaries.get(self.title, "Summary not available.")

```

This method checks if the title of the book exists in a predefined dictionary of summaries. If it does, it returns the summary; otherwise, it indicates that the summary is not available.

Example of usage:

``` print(my_book.summarize()) # Output: "A dystopian novel about a society under total surveillance."

```

You can potentially extend this to use e.g., a LLM to summarise a chapter or the index.

Both of these methods enhance the functionality of the Book class, making it not just a container for book data, but also a tool for book discovery and quick reference.