pandas怎么修改部分数据但输出所有的值

Question

这是df的数据

df
Out[86]: 
        one       two     three
A -0.709805  1.070332  0.931865
B       NaN       NaN       NaN
C  2.370934 -0.688606       NaN
D  0.868554 -1.443167       NaN
E -0.668985 -1.378245 -1.302251

我想要只替换掉one two两列的nan，然后其余的原样输出

书上给的例子 df[['one','two']].replace(np.nan,'hello')

Out[88]: 
        one       two
A -0.709805   1.07033
B     hello     hello
C   2.37093 -0.688606
D  0.868554  -1.44317
E -0.668985  -1.37825

由于有df[['one','two']]提前进行了列筛选，导致最后结果虽然只替换了one two两列，但也只输出了one two两列
想问
怎么在仅对两列替换的同时，把四列全部显示出来

Answer 1

df[['one','two']]=df[['one','two']].replace(np.nan,'hello')
df