When I have a list a, I can create a shallow copy of a by the following four different methods:

a = [1, 2, 3]

b = list(a)
b = a.copy()
b = a[:]

import copy
b = copy.copy(a)

Here, I am wondering whether they always give the same result b, or possibly are there some cases (of a) that may give different results for b? (I guess performance may be different between the above methods, but here I am interested in the value of b rather than computational efficiency.)