(Yet Another) List Aliasing Conundrum

Question

I thought I had the whole list alias thing figured out, but then I came across this:

    l = [1, 2, 3, 4]
    for i in l:
        i = 0
    print(l)

which results in:

    [1, 2, 3, 4]

So far so good.

However, when I tried this:

    l = [[1, 2], [3, 4], [5, 6]]
    for i in l:
        i[0] = 0

I get

    [[0, 2], [0, 4], [0, 5]]

Why is this?

Does this have to do with how deep aliasing goes?

Answer 1

The first rebinds the name. Rebinding a name changes only the local name. The second mutates the object. Mutating an object changes it everywhere it is referenced (since it's always the same object).