dataframe 找出空值的行or列

import pandas as pd
import numpy as np
n1=np.arange(20,dtype=float).reshape(5,4)
n1[3,3]=np.nan
n1
index1=['m1','m2','m3','m4','m5']
col1=['c1','c2','c3','c4']
mat1=pd.DataFrame(data=n1,index=index1,columns=col1)
mat1.isnull().any()
mat1.isnull().T.any()
mat1[mat1.isnull().T.any()]