我买了一本《精通scikit-learn机器学习》，并开始按照书中的内容进行学习。然而，书中相当一部分代码现在已经过时了。

书中第一个代码片段，

import matplotlib.pyplot as pltX = [[6], [8], [10], [14],   [18]]y = [[7], [9], [13], [17.5], [18]]plt.figure()plt.title('Pizza price plotted against diameter')plt.xlabel('Diameter in inches')plt.ylabel('Price in dollars')plt.plot(X, y, 'k.')plt.axis([0, 25, 0, 25])plt.grid(True)plt.show()

运行得很好。然而，当我继续第二个代码片段时：

from sklearn.linear_model import LinearRegression# Training dataX = [[6], [8], [10], [14],   [18]]y = [[7], [9], [13], [17.5], [18]]# Create and fit the modelmodel = LinearRegression()model.fit(X, y)print 'A 12" pizza should cost: $%.2f' % model.predict([12])[0]

它给我了一个错误：

 A 12-inch pizza should cost: $%.2f /home/dave/anaconda3/lib/python3.5/site-packages/sklearn/utils/validation.py:386: DeprecationWarning: Passing 1d arrays as data is deprecated in 0.17 and willraise ValueError in 0.19. Reshape your data either using X.reshape(-1, 1) if your data has a single feature or X.reshape(1, -1) if it contains a single sample.   DeprecationWarning) Traceback (most recent call last):   File "002----Chapter2-B.py", line 11, in <module>     print ("A 12-inch pizza should cost: $%.2f") % model.predict([12])[0] TypeError: unsupported operand type(s) for %: 'NoneType' and 'float'

而它应该给我的结果是：

 A 12" pizza should cost: $13.68

有什么方法可以修复这个问题吗？

回答：

尝试以下方法：

print ("A 12-inch pizza should cost: $%.2f" % model.predict(np.array([12]).reshape(1, -1)[0]))

我使用了reshape(1,-1)来将二维数组传递给predict函数。