在 pandas.DataFrame 的对角线上设置值 [英] Set values on the diagonal of pandas.DataFrame

问题描述

我有一个 Pandas 数据框，我想将对角线设为 0

I have a pandas dataframe I would like to se the diagonal to 0

import numpy
import pandas

df = pandas.DataFrame(numpy.random.rand(5,5))
df

Out[6]:
     0           1           2           3               4
0    0.536596    0.674319    0.032815    0.908086    0.215334
1    0.735022    0.954506    0.889162    0.711610    0.415118
2    0.119985    0.979056    0.901891    0.687829    0.947549
3    0.186921    0.899178    0.296294    0.521104    0.638924
4    0.354053    0.060022    0.275224    0.635054    0.075738
5 rows × 5 columns

现在我想将对角线设置为 0:

now I want to set the diagonal to 0:

for i in range(len(df.index)):
    for j in range(len(df.columns)):
        if i==j:
            df.loc[i,j] = 0
df
Out[9]:
     0           1           2           3           4
0    0.000000    0.674319    0.032815    0.908086    0.215334
1    0.735022    0.000000    0.889162    0.711610    0.415118
2    0.119985    0.979056    0.000000    0.687829    0.947549
3    0.186921    0.899178    0.296294    0.000000    0.638924
4    0.354053    0.060022    0.275224    0.635054    0.000000
5 rows × 5 columns

但一定有比这更pythonic的方式！?

but there must be a more pythonic way than that!?

推荐答案

In [21]: df.values[[np.arange(df.shape[0])]*2] = 0

In [22]: df
Out[22]: 
          0         1         2         3         4
0  0.000000  0.931374  0.604412  0.863842  0.280339
1  0.531528  0.000000  0.641094  0.204686  0.997020
2  0.137725  0.037867  0.000000  0.983432  0.458053
3  0.594542  0.943542  0.826738  0.000000  0.753240
4  0.357736  0.689262  0.014773  0.446046  0.000000

请注意，这仅在 df 的行数与列数相同时才有效.另一种适用于任意形状的方法是使用 np.fill_diagonal:

Note that this will only work if df has the same number of rows as columns. Another way which will work for arbitrary shapes is to use np.fill_diagonal:

In [36]: np.fill_diagonal(df.values, 0)

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