Why does Python list initialization method affect indexing?

Question

I recently stumbled on some serious weirdness with python lists if you try to use them like arrays (not by appending):

make a list by duplication:

myLists = 5 * [3 * [0]]
print(myLists)

[[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]]

run this...you get:

for i in range(5):
    for j in range(3):
        myLists[i][j] = i + j
print(myLists)

[[4, 5, 6], [4, 5, 6], [4, 5, 6], [4, 5, 6], [4, 5, 6]]

why only the last row copied everywhere?

now, create the list contiguously with list comprehension:

myLists = [[0 for i in range(3)] for j in range(5)]
print(myLists)

here it is (it's the same structure):

[[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]]

run the same loops...now you get:

for i in range(5):
    for j in range(3):
        myLists[i][j] = i + j
print(myLists)

[[0, 1, 2], [1, 2, 3], [2, 3, 4], [3, 4, 5], [4, 5, 6]]

now it's correct...

I'm guessing some strange linked-list-related pointer details under the CPython hood cause this, but I don't know what they are...

Can anyone help?