使用matplotlib画图，为什么我的颜色不变？

Question

问题遇到的现象和发生背景

使用matplotlib画图，为什么我的颜色不变？

用代码块功能插入代码，请勿粘贴截图

%matplotlib inline

import numpy as np
import matplotlib.pyplot as plt
import matplotlib as mpl

np.random.seed(314)
data_size1=100
x1=np.random.randn(data_size,2)+np.array([4,4])
y1=[0 for _ in range(data_size)]
data_size2=100
x2=np.random.randn(data_size,2)+np.array([10,10])
y2=[0 for _ in range(data_size)]

x=np.concatenate((x1,x2),axis=0)
y=np.concatenate((y1,y2),axis=0)

data_all_size=data_size1+data_size2
shuff_index=np.random.permutation(data_all_size)
x=x[shuff_index]
y=y[shuff_index]

train_size=int(data_all_size*0.7)
train_x=x[:train_size]
train_y=y[:train_size]
test_x=x[train_size:]
test_y=y[train_size:]

for i in range(train_size):
if train_y[i]==0:
plt.scatter(train_x[i,0],train_x[i,1],s=38,c='g',marker='*')
else:
plt.scatter(train_x[i,0],train_x[i,1],s=38,c='r',marker='.')
mpl.rcParams['font.family'] = 'SimHei'
plt.title("训练数据")
plt.savefig("fig-res-knn-traindata.pdf")
plt.show()

运行结果及报错内容

Answer 1

因为train_y[i]一直都是0