python - 向 numpy 数组添加索引

Question

我有一个 numpy 数组:

prob_rf = [[0.4, 0.4, 0.4], 
           [0.5, 0.5, 0.5], 
           [0.6, 0.6, 0.6]]

我想为每个内部数组添加一个索引号:

prob_rf = [[1, 0.4, 0.4, 0.4],
           [2, 0.5, 0.5, 0.5],
           [3, 0.6, 0.6, 0.6]]

然后使用 numpy.savetxt 将该数组保存到 csv 文件中。

我目前正在这样做:

    id = [i for i in xrange(1,len(prob)+1)]
    prob_rf = np.insert(prob_rf, 0, id, axis=1)
    np.savetxt("foo.csv", prob_rf, delimiter=",", fmt='%1.1f')

但是这是给输出作为

[[1.0, 0.4, 0.4, 0.4], 
 [2.0, 0.5, 0.5, 0.5], 
 [3.0, 0.6, 0.6, 0.6]]

谁能告诉我如何得到输出

[[1, 0.4, 0.4, 0.4], 
 [2, 0.5, 0.5, 0.5], 
 [3, 0.6, 0.6, 0.6]]

Answer 1

使用带有 fmt 参数的列表来指定每一列的格式:

fmt=['%d', '%1.1f', '%1.1f', '%1.1f']

完整示例:

import numpy as np
prob_rf = [[1, 0.4, 0.4, 0.4],
           [2, 0.5, 0.5, 0.5],
           [3, 0.6, 0.6, 0.6]]
np.savetxt("foo.csv", prob_rf, delimiter=",", fmt=['%d', '%1.1f', '%1.1f', '%1.1f'])

生成的文件:

1,0.4,0.4,0.4
2,0.5,0.5,0.5
3,0.6,0.6,0.6