What's the logic behind this guys

Question

I really don't understand the logic behind this, could someone explain this to me
https://code.sololearn.com/cu6H2dd1xTI9/?ref=app

Answer 1

a = [[]]*3
a[0].append(3)
print(a)

1. 3 multiplies the empty lists inside the 2d 3 times this it will look like this.
[[],[],[]]
2. Then you want to append the 3 at the index 0 of each list in the 2d list.
And it will be.
[[3],[3],[3]]

Answer 2

Thank you so much bro