Set values on the diagonal of pandas.DataFrame

Question

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 

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 

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

Answer 1

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 

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)