如何初始化Python数据类二维列表？

Question

可以为初始化 2D 数组的 python 数据类创建默认初始化程序，即结果与

from dataclasses import dataclass, field
from typing import List
MAX = 5
@dataclass
class AlgoData:
    list2D: List[List[int]]  # = ???
    list1D: List[int] = field(default_factory=list)

b = [[] for m in range(MAX)]
a = AlgoData(b)

但没有b争论。结果：

AlgoData(list2D=[[], [], [], [], []], list1D=[])

Answer 1

您可以使用lambda函数代替default_factoryfor field：

from dataclasses import dataclass, field
from typing import List
MAX = 5
@dataclass
class AlgoData:
    list2D: List[List[int]] = field(default_factory=lambda: [[] for m in range(MAX)])
    list1D: List[int] = field(default_factory=list)

a = AlgoData()

a变成：

AlgoData(list2D=[[], [], [], [], []], list1D=[])