pandas dataframe 乘法得到nan

为啥在i=1 j=0 相乘就错了

df.iloc[i*4:i*4+4,j]*m1

这个时候乘法结果是8个值

import pandas as pd
import numpy as np
df =  pd.DataFrame(np.ones((16,4)))

m0 = pd.DataFrame(np.arange(4))
m = pd.DataFrame(np.zeros((4,4)))
for i in range(4):
	m.iloc[:,i] = m0
	
m1 = m.iloc[:,0]

df2 = pd.DataFrame(np.zeros_like(df))

for i in range(4):
	for j in range(4):
		tmp =  df.iloc[i*4:i*4+4,j]
		df2.iloc[i*4:i*4+4,j] = df.iloc[i*4:i*4+4,j]*m1

print(df2)