# using of M.permute_rows_and_columns

Hi

I am aware that with this question my Karma will drop a notch !

despite explanations

I don't understand the use of M.permute_rows_and_columns() how to use it to do this function below ?

```
M = matrix(ZZ,[[1,0,0,0,0],[0,2,0,0,0],[0,0,3,0,0],[0,0,0,4,0],[0,0,0,0,5]])
def permRandC(a,b) :
"permute row and column a,b"
Mc=copy(M)
Mc[:,a]=M[:,b]
Mc[:,b]=M[:,a]
Mr=copy(Mc)
Mr[a,:]=Mc[b,:]
Mr[b,:]=Mc[a,:]
return Mr
show(permRandC(0,1))
```