python - 如何在键为对象的 Python 中初始化字典？

Question

我正在尝试重新表述发现的实现 here .这是我目前所拥有的:

import csv
import math
import random

training_set_ratio = 0.67

training_set = []
test_set = []


class IrisFlower:
    def __init__(self, petal_length, petal_width, sepal_length, sepal_width, flower_type):
        self.petal_length = petal_length
        self.petal_width = petal_width
        self.sepal_length = sepal_length
        self.sepal_width = sepal_width
        self.flower_type = flower_type

    def __hash__(self) -> int:
        return hash((self.petal_length, self.petal_width, self.sepal_length, self.sepal_width))

    def __eq__(self, other):
        return (self.petal_length, self.petal_width, self.sepal_length, self.sepal_width) \
               == (other.petal_length, other.petal_width, other.sepal_length, other.sepal_width)


def load_data():
    with open('dataset.csv') as csvfile:
        rows = csv.reader(csvfile, delimiter=',')
        for row in rows:
            iris_flower = IrisFlower(float(row[0]), float(row[1]), float(row[2]), float(row[3]), row[4])
            if random.random() < training_set_ratio:
                training_set.append(iris_flower)
            else:
                test_set.append(iris_flower)


def euclidean_distance(flower_one: IrisFlower, flower_two: IrisFlower):
    distance = 0.0
    distance = distance + math.pow(flower_one.petal_length - flower_two.petal_length, 2)
    distance = distance + math.pow(flower_one.petal_width - flower_two.petal_width, 2)
    distance = distance + math.pow(flower_one.sepal_length - flower_two.sepal_length, 2)
    distance = distance + math.pow(flower_one.sepal_width - flower_two.sepal_width, 2)
    return distance


def get_neighbors(test_flower: IrisFlower):
    distances = []
    for training_flower in training_set:
        dist = euclidean_distance(test_flower, training_flower)
        d = dict()
        d[training_flower] = dist
        print(d)
    return


load_data()
get_neighbors(test_set[0])

目前，在以下代码块中打印语句:

def get_neighbors(test_flower: IrisFlower):
    distances = []
    for training_flower in training_set:
        dist = euclidean_distance(test_flower, training_flower)
        d = dict()
        d[training_flower] = dist
        print(d)
    return

将有类似的输出

{<__main__.IrisFlower object at 0x107774fd0>: 0.25999999999999945}

没关系。但我不想先创建字典，然后附加键值，如:

d = dict()
d[training_flower] = dist

所以这就是我正在尝试的:

d = dict(training_flower = dist)

但是，dist 方法似乎不是在使用实例，而是一个字符串，因为我看到的打印内容如下:

{'training_flower': 23.409999999999997}
{'training_flower': 16.689999999999998}

如何在一个语句中使用对象作为键来创建字典？

Answer 1

在您编写 d = dict(training_flower=dist) 的代码段中，“training_flower”是 dict 函数的关键字参数，而不是对象。相当于写d = {'training_flower': dist}。创建以对象为键的字典的唯一方法是使用后一种语法:

d = {training_flower: dist}