Question

可以为Python数据类创建默认的初始化程序，以初始化2D数组，即与

相同

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参数。结果：

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

Answer 1

您可以使用lambda函数代替default_factory的{{1}}：

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()变为：

Answer 2

另一种选择是在初始化后（通过__post_init__）分配属性。

给出

from typing import List

from dataclasses import dataclass, field


MAX = 5

代码

@dataclass
class AlgoData:
    """Algorithm data."""
    list1D: List[int] = None
    list2D: List[List[int]] = field(default_factory=list)

    def __post_init__(self):

        self.list2D = [[] for _ in range(MAX)]

演示

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

如何初始化Python数据类2D列表？

2 个答案: