[Python] I'm confused about how objects in shallow copy and deep copy are referenced

Shallow_Copy

foo = [1, 2, []]
bar = foo.copy()
foo[0] is bar[0]
foo[2] is bar[2]


True
True


Does this mean they both reference to the same objects? However, they behave differently when I modify them.

bar[0] = 0
print(foo)


[1, 2, []]


bar[-1].append(3)
print(foo)


[1, 2, [3]]


if foo[0] and bar[0] are referencing the same object, when I modified bar[0] why did foo[0] stay the same? And when I modified bar[2], foo[2] changed

Deep_Copy

foo = [1, 2, []]
bar = copy.deepcopy(foo)
foo[0] is bar[0] foo[2] is bar[2]


True
False


Additionally, why foo[2] and bar[2] don't reference the same object here

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