Music Store

Music store is an application used to asses the knowledge of OOP concepts in python. The application is a simple music store that allows users to add, list and search for music disc. The application is implemented using classes and objects in python.

The model of the application is as follows:

The application code is incomplete, the idea is to complete it taking into account the following steps.

1. Complete de class Transaction taking into account the following requirements:

   • The class should have a constant SELL of type int with value 1.

   • The class should have a constant SUPPLY of type int with value 2.

   • The class should have an __init__ method that receives the following parameters:

     • type of type int.
     • copies of type int.

     In the __init__ method the class should initialize the attributes type and copies with the values received as parameters.

   • The class should have an attribute date of type datetime that should be initialized with the current date and time (you can use the datetime.now() function to get the current date an time).

2. Complete the Disc class taking into account the following requirements:

   • The class should have an __init__ method that receives the following parameters:

     • sid of type str.
     • title of type str.
     • artist of type str.
     • sale_price of type float.
     • purchase_price of type float.
     • quantity of type int.

     In the __init__ method the class should initialize the attributes sid, title, artist, sale_price, purchase_price and quantity with the values received as parameters.

   • The class should have the attributes transactions of type list[Transaction] and song_list of type list[str]. Both attributes should be initialized as an empty list.

   • The class should have an instance method add_song that receives a parameter song of type str and adds the song to the song_list attribute.

   • The class should have an instance method sell that receives a parameter quantity of type int and does the following:

     • If the parameter copies is greater than the quantity attribute of the disc, the method should return False.
     • Otherwise, the method decreases the quantity attribute of the disc by the value of the parameter copies and adds a new Transaction object to the transactions list with the type Transaction.SELL and the number of copies sold.
     • The method should return True.

   • The class should have an instance method supply that receives a parameter copies of type int and does the following:

     • Increases the quantity attribute of the disc by the value of the parameter copies
     • Adds a new Transaction object to the transactions list with the type Transaction.SUPPLY and the number of copies supplied.

   • The class should have an instance method copies_sold that returns an int with the total number of copies sold.

     Hint: you could add the number of copies of each transaction of type Transaction.SELL.

   • The class should have an instance method __str__ that return a str with the following format:

     SID: {sid}
     Title: {title}
     Artist: {artist}
     Song List: {song_list}
     

     Where {sid}, {title} and {artist} should be replaced with the values of the attributes of the disc. The {song_list} should be replaced with the list of songs of the disc separated by a comma and a space.

     Hint: you could use an f-string (f"") to format the string and \n within the string for a new line.

3. Complete the MusicStore class taking into account the following requirements:

   • The class should have an __init__ method that initializes the discs attribute of type dict[str, Disc] as an empty dictionary.

   • The class should have an instance method add_disc that receives the parameters sid of type str, title of type str, artist of type str, sale_price of type float, purchase_price of type float and quantity of type int and does the following:

     • Checks if the sid is not already in the discs dictionary.
     • If the sid is not in the discs dictionary, the method creates a new Disc object with the received parameters and adds it to the discs dictionary using the sid as the key.

   • The class should have an instance method search_by_sid that receives the parameter sid of type str and returns Disc | None. The method should return the disc with the sid received as parameter or None if the disc is not found.

   • The class should have an instance method search_by_artist that receives the parameter artist of type str and returns list[Disc]. The method should return a list with all the discs that have the artist received as parameter.

   • The class should have the instance methods sell_disc and supply_disc that receive the parameters sid of type str and copies of type int. Copy the following code to the MusicStore class to complete the methods:

     def sell_disc(self, sid: str, copies: int) -> bool:
         disc = self.search_by_sid(sid)
         if disc is None:
             return False
         
         return disc.sell(copies)
     
     def supply_disc(self, sid: str, copies: int) -> bool:
         disc = self.search_by_sid(sid)
         if disc is None:
             return False
         
         disc.supply(copies)
         return True

   • The class should have an instance method worst_selling_disc that returns Disc | None with the disc that has sold the least number of copies or None if there are no discs in the store.