dataclasses

提供一个装饰器，自动生产init 和 repr

from dataclasses import dataclass

@dataclass
class InventoryItem:
    """Class for keeping track of an item in inventory."""
    name: str
    unit_price: float
    quantity_on_hand: int = 0

    def total_cost(self) -> float:
        return self.unit_price * self.quantity_on_hand

#等价于下面所示代码
def __init__(self, name: str, unit_price: float, quantity_on_hand: int = 0):
    self.name = name
    self.unit_price = unit_price
    self.quantity_on_hand = quantity_on_hand

dataclasses.dataclass用法

下示三种用法作用是相同的

@dataclass
class C:
    ...

@dataclass()
class C:
    ...

@dataclass(init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False, match_args=True, kw_only=False, slots=False)
class C:
   ...

如果frozen =True 则属性不可赋值

dataclasses.field用法

dataclasses.asdict 用法

将dataclass实例转化为字典

@dataclass
class Point:
     x: int
     y: int

@dataclass
class C:
     mylist: list[Point]

p = Point(10, 20)
assert asdict(p) == {'x': 10, 'y': 20}

c = C([Point(0, 0), Point(10, 4)])
assert asdict(c) == {'mylist': [{'x': 0, 'y': 0}, {'x': 10, 'y': 4}]}

dataclasses.astuple 用法

将dataclass实例转化为元组

@dataclass
class Point:
     x: int
     y: int

@dataclass
class C:
     mylist: list[Point]

p = Point(10, 20)
assert astuple(p) == (10, 20)

c = C([Point(0, 0), Point(10, 4)])
assert astuple(c) == ([(0, 0), (10, 4)],)