@dataclassをちょっと理解する

環境

python: 3.12

dataclassを使わない場合の書き方

class Point:
    def __init__(self, x, y):
        self.x: str = x
        self.y: str = y

    def __repr__(self):
        return f"Point({self.x}, {self.y})"

    def __eq__(self, other):
        if isinstance(other, Point):
            return self.x == other.x and self.y == other.y
        return False

    def __hash__(self):
        return hash((self.x, self.y))

    # ...etc
    

print("__init__")
point1 = Point(1, 2)
point2 = Point(1, 2)

print("__repr__")
print(point1)  # Point(1, 2)
print(point2)  # Point(1, 2)

print("__eq__")
print(point1 == point2)  # True

print("__hash__")
point_set = {point1}
print(point_set)  # {Point(1, 2)}
print(point2 in point_set)  # True

dataclassを使う場合の書き方（frozen=False）

from dataclasses import dataclass


@dataclass
class Point:
    x: int
    y: int

# クラスの使い方
print("__init__")
point1 = Point(1, 2)
point2 = Point(1, 2)

print("__repr__")
print(point1)  # Point(1, 2)
print(point2)  # Point(1, 2)

print("__eq__")
print(point1 == point2)  # True

# print("__hash__")
# point_set = {point1}  # エラー
# print(point_set)  # {Point(1, 2)}
# print(point2 in point_set)  # True

print(point1.x)  # 1
point1.x = 3
print(point1.x)  # 3

dataclassを使う場合の書き方（frozen=True）

from dataclasses import dataclass


@dataclass(frozen=True)
class Point:
    x: int
    y: int


# クラスの使い方
print("__init__")
point1 = Point(1, 2)
point2 = Point(1, 2)

print("__repr__")
print(point1)  # Point(1, 2)
print(point2)  # Point(1, 2)

print("__eq__")
print(point1 == point2)  # True

print("__hash__")
point_set = {point1}
print(point_set)  # {Point(1, 2)}
print(point2 in point_set)  # True

print(point1.x)  # 1
point1.x = 3  # エラー