Value not overwritten after every iteration in python

A=[[1,-2,3],
  [-4,5,-6],
  [7,-8,9]]
temp=A[1:]
l=[]
for i in range(len(temp[0])):
    temp1=temp[:]
    for j in range(len(temp)):
        temp1[j].pop(i)

it is a block of code for the calculation of determinant of a matrix without using the numpy or scipy module . in this block temp1 should be overwritten after every iteration of i but it isn't and the temp list is also changing.