why the answer is wrong?!

Question

In the below code, I'll expect the answer is [[0, 1, 0, 0, 0], [1,0, 2, 0, 0], [0, 2, 0, 3, 4], [0, 0, 3, 0, 0], [0,0, 4, 0, 0]] , but the answer will be different.

def filler(mat,zar,n):

new=[[0]*n]*n
for k in mat:
for i in range(n):
for j in range(n):
if k[0]-1 == i and k[1]-1 == j:
new[i][j] = zar[mat.index(k)]
new[j][i] = zar[mat.index(k)]
return new
#-------------------------------------------------------
a = [[1, 2, 1, 2], [2, 3, 1, 2], [3, 4, 1, 2], [3, 5, 1, 2]]
b = [1,2,3,4]
c = 5

f = filler(a,b,c)
print(f)

#-------------------------
please help me.

Answer 1

new=[[0 for i in range(n)] for j in range(n)]

Your code fills "new" with five references to the same list. If you change one of them, you change all of them.

Answer 2

thanks Anna