老师，请问为什么我这样写不能执行

Question

from sklearn import datasets
from math import sqrt
import numpy as np
from collections import Counter

# digits=datasets.load_digits()
iris=datasets.load_iris()
# print(iris)
X=iris.data
y=iris.target

def train_test_split(X,y,test_ratio=0.2):
    shuffle_indexes = np.random.permutation(len(X))

    test_size = int(len(X) * test_ratio)

    test_indexes = shuffle_indexes[:test_size]
    train_indexes = shuffle_indexes[test_size:]

    X_train = X[train_indexes]
    y_train = y[train_indexes]
    # print(X_train.shape)
    # print(y_train.shape)

    X_test = X[test_indexes]
    y_test = y[test_indexes]
    # print(X_test.shape)
    # print(y_test.shape)

    return X_train,X_test,y_train,y_test



class KNNClassifier:
    def __init__(self,k):
        self.k=k
        self._X_train=None
        self._y_train=None

    def fit(self,X_train,y_train):
        self._X_train=X_train
        self._y_trian=y_train
        return self

    def predict(self,X_predict):
        y_predict = [self._predict(x) for x in X_predict]
        return np.array(y_predict)

    def _predict(self,x):
        distances = []
        for x_train in self._X_train:
            d = sqrt(np.sum((x_train - x) ** 2))
            distances.append(d)

        nearest = np.argsort(distances)
        topK_y = [self._y_train[i] for i in nearest[:self.k]]

        votes = Counter(topK_y)
        return votes.most_common(1)[0][0]

    def _repr_(self):
        return "KNN(k=%d)"% self.k

X_train,X_test,y_train,y_test=train_test_split(X,y)
knn_clf=KNNClassifier(3)
knn_clf.fit(X_train,y_train)
y_predict=knn_clf.predict(X_test)
print(y_predict)

Traceback (most recent call last):
File “E:/软件/PyCharm/works/MachineL/KNN.py”, line 67, in
y_predict=knn_clf.predict(X_test)
File “E:/软件/PyCharm/works/MachineL/KNN.py”, line 46, in predict
y_predict = [self._predict(x) for x in X_predict]
File “E:/软件/PyCharm/works/MachineL/KNN.py”, line 46, in
y_predict = [self._predict(x) for x in X_predict]
File “E:/软件/PyCharm/works/MachineL/KNN.py”, line 56, in _predict
topK_y = [self._y_train[i] for i in nearest[:self.k]]
File “E:/软件/PyCharm/works/MachineL/KNN.py”, line 56, in
topK_y = [self._y_train[i] for i in nearest[:self.k]]
TypeError: ‘NoneType’ object is not subscriptable

Answer 1

liuyubobobo 2018-12-30 14:44:36

目测最后 topK_y = [self._y_train[i] for i in nearest[:self.k]] 一句话，或者是_y_train，或者是nearest为空。如果你确定你的knn算法和课程一致的话，请确认你的调用过程没有问题，尤其是传给knn的X_train，y_train和predict的x是正确的。

这个课程的所有代码，都可以通过课程的官方github获得。可以先尝试在你的环境下运行课程的官方代码，看看是否有问题？如果没有问题，请仔细调试比对，看看自己的代码哪里有问题？传送门：https://github.com/liuyubobobo/Play-with-Machine-Learning-Algorithms    

如果访问github有困难，也可以使用慕课网内部该课程的官方代码仓：https://git.imooc.com/coding-169/coding-169   

加油！：）

• 提问者 慕云19 #1

  嗯嗯，谢谢老师，这么快就回复我了，而且确实是y_train那个地方写错了，导致传的值为空

Answer 2

提问者 慕云19 2018-12-30 14:29:11

老师我知道了，有个地方写错了