# Import the dataclass module from the dataclasses library
from dataclasses import dataclass

# Use the dataclass decorator to create a dataclass called Person
@dataclass
class Person:
    # Define the attributes of the Person class with their respective data types
    name: str # Name attribute of type string
    age: int # Age attribute of type integer
    
    # Define a method called say_hello that takes in the self parameter
    def say_hello(self):
        # Print a greeting message using the name and age attributes of the Person object
        print(f"Hello, my name is {self.name} and I'm {self.age} years old.")

# Define a class called Person
class Person:
    # Initialize the class with name and age attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    # Define a method to print the person's name and age
    def __str__(self):
        return f"{self.name} is {self.age} years old."

# Create an instance of the Person class with name "John Doe" and age 35
john = Person("John Doe", 35)

# Print the instance of the Person class
print(john) # Output: John Doe is 35 years old.

# Importing necessary modules
from dataclasses import dataclass, field # Importing the dataclass module and the field function
from typing import List # Importing the List type from the typing module

# Defining a dataclass with the 'order' parameter set to True
@dataclass(order=True)
class Student:
    name: str # Defining a 'name' field of type string
    grade: int = 0 # Defining a 'grade' field of type integer with a default value of 0
    
    # Defining a post-init method to add a default value of 10 to the 'grade' field
    def __post_init__(self):
        self.grade += 10
        
    # Defining a property method to calculate the total grade of the student
    @property
    def total(self):
        return self.grade * 2

# Creating a list of Student objects
students: List[Student] = [Student("Alice", 85), Student("Bob")] # Passing in values for the 'name' and 'grade' fields

# Sorting the list of students based on their total grade and then their name
sorted_students = sorted(students, key=lambda s: (s.total, -s.name)) # Using a lambda function to specify the sorting criteria

# Printing the sorted list of students
print(sorted_students)

# Inheritance also works with dataclasses! You can create a subclass of your data class and add some extra functionality to it:

# Importing necessary modules
from dataclasses import dataclass, field
from typing import List

# Defining a dataclass called "Student" with two attributes: name and grade
@dataclass(order=True) # Adding the "order" parameter to enable ordering of instances based on attributes
class Student:
    name: str
    grade: int = 0 # Adding a default value of 0 to the "grade" attribute
    
    # Defining a method to be executed after the initialization of an instance
    def __post_init__(self):
        self.grade += 10 # Adding 10 to the default value of "grade" attribute
        
    # Defining a property called "total" which returns the total grade of a student (grade * 2)
    @property
    def total(self):
        return self.grade * 2

# Defining a dataclass called "TopStudent" which inherits from the "Student" dataclass
@dataclass(order=True) # Adding the "order" parameter to enable ordering of instances based on attributes
class TopStudent(Student):
    # Defining a nested class called "Meta" to add metadata to the dataclass
    class Meta:
        abstract = True # Adding the "abstract" attribute to make the class abstract (cannot be instantiated)
    
    # Defining a method to be executed after the initialization of an instance
    def __post_init__(self):
        super().__post_init__() # Calling the parent's constructor to execute its __post_init__ method
        
        # Checking if the total grade of the student is greater than 100
        if self.total > 100:
            print("Congratulations! You are a top student.") # Printing a congratulatory message if the condition is met