Question

我正在尝试在python中从头实现KNN。所有功能都可以正常工作，直到我进入main（）函数

import csv
import random
import math
import operator

with open('iris.csv', 'r') as csvfile:
    lines = csv.reader(csvfile)
    for row in lines:
        print(', '.join(row))

在这里我创建了一个函数来读取iris.csv文件

def loadDataset(filename, split, trainingSet=[] , testSet=[]):
    with open(filename, 'r') as csvfile:
        lines = csv.reader(csvfile)
        dataset = list(lines)
        for x in range(len(dataset)-1):
            for y in range(4):
                dataset[x][y] = dataset[x][y]
            if random.random() < split:
                trainingSet.append(dataset[x])
            else:
                testSet.append(dataset[x])

这是我测试功能的地方

trainingSet=[]
testSet=[]
loadDataset('iris.csv', 0.66, trainingSet, testSet)
print('Train: ' + repr(len(trainingSet))) 
print('Test: ' + repr(len(testSet)))

这是距离函数

def euclideanDistance(instance1, instance2, length):
    distance = 0
    for x in range(length):
        distance += pow((instance1[x] - instance2[x]), 2)
    return math.sqrt(distance)

测试距离函数

data1 = [2, 2, 2, 'a']
data2 = [4, 4, 4, 'b']
distance = euclideanDistance(data1, data2, 3)
print('Distance: ' + repr(distance))

邻居功能

def getNeighbors(trainingSet, testInstance, k):
    distances = []
    length = len(testInstance)-1
    for x in range(len(trainingSet)):
        dist = euclideanDistance(testInstance, trainingSet[x], length)
        distances.append((trainingSet[x], dist))
    distances.sort(key=operator.itemgetter(1))
    neighbors = []
    for x in range(k):
    neighbors.append(distances[x][0])
    return neighbors

测试邻居功能

trainSet = [[2, 2, 2, 'a'], [4, 4, 4, 'b']]
testInstance = [5, 5, 5]
k = 3
neighbors = getNeighbors(trainSet, testInstance, 1)
print(neighbors)

获得响应的功能

def getResponse(neighbors):
    classVotes = {}
    for x in range(len(neighbors)):
        response = neighbors[x][-1]
        if response in classVotes:
            classVotes[response] += 1
        else:
            classVotes[response] = 1
    sortedVotes = sorted(classVotes.items(), key=operator.itemgetter(1), reverse=True)
    return sortedVotes[0][0]

测试功能

neighbors = [[1,1,1,'a'], [2,2,2,'a'], [3,3,3,'b']]
response = getResponse(neighbors)
print(response)

精度函数

def getAccuracy(testSet, predictions):
    correct = 0
    for x in range(len(testSet)):
        if testSet[x][-1] is predictions[x]:
            correct += 1
    return (correct/float(len(testSet))) * 100.0

测试准确性功能

testSet = [[1,1,1,'a'], [2,2,2,'a'], [3,3,3,'b']]
predictions = ['a', 'a', 'a']
accuracy = getAccuracy(testSet, predictions)
print(accuracy)

出现错误所在的main（）

#main
def main():
    # prepare data
    trainingSet=[]
    testSet=[]
    split = 0.67
    loadDataset('iris.csv', split, trainingSet, testSet)
    print ('Train set: ' + repr(len(trainingSet)))
    print ('Test set: ' + repr(len(testSet)))
    # generate predictions
    predictions=[]
    k = 3
    for x in range(len(testSet)):
        neighbors = getNeighbors(trainingSet, testSet[x], k)
        result = getResponse(neighbors)
        predictions.append(result)
        print('> predicted=' + repr(result) + ', actual=' + repr(testSet[x][-1]))
    accuracy = getAccuracy(testSet, predictions)
    print('Accuracy: ' + repr(accuracy) + '%')

main()

但是当我进入main（）函数时，会收到此错误消息

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-68-ba4ef0fcfe9f> in <module>()
     18     print('Accuracy: ' + repr(accuracy) + '%')
     19 
---> 20 main()

<ipython-input-68-ba4ef0fcfe9f> in main()
     11     k = 3
     12     for x in range(len(testSet)):
---> 13         neighbors = getNeighbors(trainingSet, testSet[x], k)
     14         result = getResponse(neighbors)
     15         predictions.append(result)

<ipython-input-62-d13cbe2070b3> in getNeighbors(trainingSet, testInstance, k)
      3     length = len(testInstance)-1
      4     for x in range(len(trainingSet)):
----> 5         dist = euclideanDistance(testInstance, trainingSet[x], length)
      6         distances.append((trainingSet[x], dist))
      7     distances.sort(key=operator.itemgetter(1))

<ipython-input-60-93ee3f7cf267> in euclideanDistance(instance1, instance2, 
length)
      2     distance = 0
      3     for x in range(length):
----> 4         distance += pow(float(instance1[x] - instance2[x]), 2)
      5     return math.sqrt(distance)

TypeError: unsupported operand type(s) for -: 'str' and 'str'

Answer 1

您已经发布了太多的代码，但是幸运的是，错误消息和堆栈跟踪很清楚：您正在尝试“减去”字符串而不是数字这两项。 tableView.value(forKey: "pendingSelectionIndexPath") as! IndexPath包将所有内容返回为字符串，因此在将数字列视为数字之前，需要将结果中的数字列显式转换为UIViewControllerPreviewingDelegate（或csv）。

我对此错误消息有疑问。TypeError：-的不支持的操作数类型：“ str”和“ str”

1 个答案: