Output of python code

Question

Why does updating the first list update all of them, instead of just the first one? Are they somehow all linked by reference?

print(arr := [[]]*3)
print(arr[0],arr[1],arr[2])
arr[0].append(7)
print(arr[0],arr[1],arr[2])

Answer 1

I believe it’s because it’s using the same list three times.

Try this:
print(arr := [[],[],[]])
print(arr[0],arr[1],arr[2])
arr[0].append(7)
print(arr[0],arr[1],arr[2])