关于python报错 unsupported operand type(s) for +: 'int' and 'str'

for i in range(len(Y_Train)):
y.append(Y_Train[i])
x=X_Train[i]
#求各测项的平均值
x_AMB_TEMP_sum=0
x_CH4_sum=0
x_CO_sum=0
x_NMHC_sum=0
for j in range(9):
x_AMB_TEMP_sum=x_AMB_TEMP_sum+x.iloc[0,j]
x_CH4_sum = x_CH4_sum + x.iloc[1, j]
x_CO_sum = x_CO_sum + x.iloc[2, j]
x_NMHC_sum = x_NMHC_sum + x.iloc[3, j]

            这个是怎么回事啊

x.iloc[1, j]
->
int(x.iloc[1, j])