代码运行错误，我是按照老师的代码写的啊

import matplotlib.pyplot as plt

import numpy as np

y = df.loc[0:100,2].values

y = np.where(y==1, 2,-2)

X=df.iloc[0:17, [0,2]].values

plt.scatter(X[:9,0],X[:9,1],color='red',marker='o',label='setosa')

plt.scatter(X[9:17, 0], X[9:17,1], color='blue', marker='+', label='rating')

plt.xlabel("Length of Petal")

plt.ylabel("Length of Scape")

plt.legend(loc='upper left')

plt.show()

报的错误是: ValueError: First argument must be a sequence

请问各位大神，这个问题怎么解决啊，昨天花了大半天也没搞清楚这个错误是什么。谢谢了先！！！