Why a and b are not same?

Question

a = [1,[1,2]]
b= a[:]
a[0] = 3
a[1][1] = 5
print(a)
print(b)

Output:
[3,[1,5]]
[1,[1,5]]

Answer 1

a[:] is shallow copying . Only reference for outer list is changed . Inner list [1, 2] is pointing to same reference .

If you need to make both list same then just assign a to b, i.e. b=a.