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问题场景：

      在读取CSV文件后，在新增一个特征列并根据已有特征修改新增列的值，结果在修改的过程中碰到SettingWithCopyWarning警告。

报错的做法：

1 import pandas as pd  2 import numpy as np  3   4 aa = np.array([1,0,1,0])  5 bb = pd.DataFrame(aa.T, columns=['one'])  6   7 bb['two'] = 0  8   9 for i in range(bb.shape[0]): 10         bb['two'][i] = 1 11  12 print(bb)

正确的做法：

1 # -*- coding: utf-8 -*-  2 import pandas as pd  3 import numpy as np  4   5 aa = np.array([1,0,1,0])  6 bb = pd.DataFrame(aa.T, columns=['one'])  7   8 # 建立  9 two = np.zeros(bb.shape[0]) 10  11 # 修改 12 for i in range(bb.shape[0]): 13     two[i] = random.random() 14  15 # 插入 16 bb.insert(0,'two',two) 17  18 print(bb)