带有可变默认参数的Python数据类继承返回零值
我试图从包含笛卡尔坐标x,y和z的3个列表中计算一个类似半径的量。 下面是我的最小代码示例,用于重现我所面临的问题; 子类计算半径数量,但返回零值。 原因是什么?如何解决 脚本:带有可变默认参数的Python数据类继承返回零值,python,python-3.x,oop,inheritance,python-dataclasses,Python,Python 3.x,Oop,Inheritance,Python Dataclasses,我试图从包含笛卡尔坐标x,y和z的3个列表中计算一个类似半径的量。 下面是我的最小代码示例,用于重现我所面临的问题; 子类计算半径数量,但返回零值。 原因是什么?如何解决 脚本: # -*- coding: utf-8 -*- from dataclasses import dataclass, field from typing import List @dataclass class LoadHalo: x: List = field(default_factory=list)
# -*- coding: utf-8 -*-
from dataclasses import dataclass, field
from typing import List
@dataclass
class LoadHalo:
x: List = field(default_factory=list)
y: List = field(default_factory=list)
z: List = field(default_factory=list)
def __post_init__(self):
self.x = [1, 2, 3]
self.y = [1, 3, 5]
self.z = [1, 4, 7]
@dataclass
class BinHalo(LoadHalo):
r: List = field(default_factory=list)
def __post_init__(self):
self.r = self.modulus(self.x, self.y, self.z)
def modulus(self, *args):
"""Modulus of vector of arbitrary size."""
return sum([i ** 2 for containers in args for i in containers]) ** .5
halo = BinHalo()
print(f"halo.x: {halo.x}")
print(f"halo.r: {halo.r}")
输出x和r的以下值:
halo.x: []
halo.r: 0.0
因为您正在重写uu post_init uuuu,所以列表仍然是空的,因为除了空列表默认值之外,它们从未被初始化过。如果还需要其行为,则必须调用要重写的超类方法
您需要的是以下内容:
def __post_init__(self):
super().__post_init__()
self.r = self.modulus(self.x, self.y, self.z)
注意类型提示中的几点:您可能希望子类中的r字段和模数的返回类型使用float:
此外,还应使用float对象初始化默认列表,以便编写:
x: List[float]
对于列表字段,因为您可能希望使用浮点数学
总而言之,我对一切都有如下定义:
from dataclasses import dataclass, field
from typing import List
@dataclass
class LoadHalo:
x: List[float] = field(default_factory=list)
y: List[float] = field(default_factory=list)
z: List[float] = field(default_factory=list)
def __post_init__(self) -> None:
self.x = [1.0, 2.0, 3.0]
self.y = [1.0, 3.0, 5.0]
self.z = [1.0, 4.0, 7.0]
@dataclass
class BinHalo(LoadHalo):
r: float = 0.0 # or whatever is suitable
def __post_init__(self) -> None:
super().__post_init__()
self.r = self.modulus(self.x, self.y, self.z)
def modulus(self, *args: List[float]) -> float:
"""Modulus of vector of arbitrary size."""
return sum([i ** 2 for containers in args for i in containers]) ** .5
在self.r=self.moduleusself.x、self.y、self.zVery之前添加super.\uuuuuu post\uuu init\uuuuuuuuuu非常清晰的工作示例。这正是我想要的。谢谢你@juanpa。arrivillaga@GustavRasmussen不用担心,你应该考虑使用MyPy来检查你的代码。
from dataclasses import dataclass, field
from typing import List
@dataclass
class LoadHalo:
x: List[float] = field(default_factory=list)
y: List[float] = field(default_factory=list)
z: List[float] = field(default_factory=list)
def __post_init__(self) -> None:
self.x = [1.0, 2.0, 3.0]
self.y = [1.0, 3.0, 5.0]
self.z = [1.0, 4.0, 7.0]
@dataclass
class BinHalo(LoadHalo):
r: float = 0.0 # or whatever is suitable
def __post_init__(self) -> None:
super().__post_init__()
self.r = self.modulus(self.x, self.y, self.z)
def modulus(self, *args: List[float]) -> float:
"""Modulus of vector of arbitrary size."""
return sum([i ** 2 for containers in args for i in containers]) ** .5