# oop/dataclass.py
from dataclasses import dataclass


@dataclass
class Body:
    '''Class to represent a physical body.'''
    name: str
    mass: float = 0.  # Kg
    speed: float = 1.  # m/s

    def kinetic_energy(self) -> float:
        return (self.mass * self.speed ** 2) / 2


body = Body('Ball', 19, 3.1415)
print(body.kinetic_energy())  # 93.755711375 Joule
print(body)  # Body(name='Ball', mass=19, speed=3.1415)


"""
$ python dataclass.py
93.755711375
Body(name='Ball', mass=19, speed=3.1415)
"""