[1, 0.6, 0.8, 0.3]
.[
[1, 0.6, 0.8, 0.3],
[0.6, 1, 0.6, 0.8],
[0.8, 0.6, 1, 0.6],
[0.3, 0.8, 0.6, 1]
]
l = [1, 0.6, 0.8, 0.3]
l_len = len(l)
res = [[l[abs(x-y)] for y in range(l_len)] for x in range(l_len)]
print(res) # [[1, 0.6, 0.8, 0.3], [0.6, 1, 0.6, 0.8], [0.8, 0.6, 1, 0.6], [0.3, 0.8, 0.6, 1]]