About List in Python

Question

I don’t know how it works. Can someone explain it for me please.
Why x = [[1, 0], [1, 0]] after I assign x[0][0] = 1 ?

https://code.sololearn.com/ck5II3snR97a/?ref=app

Thanks!

Answer 1

Anh Hoàng Thế In addition to what the others have already explained, the outer multiplication appears to be referencing a copy of the first list instead of creating a unique reference to a new list.

I created a new variant of your code to demonstrate this further.

https://code.sololearn.com/cU7W5mYzTCV9/?ref=app

Answer 2

Although the list in your question looks like a list with two lists in it, it's in reality a list with *one* list in it - the same list twice!

So if you change one, you change the other too. Because it isn't really an *other*.

Answer 3

It works like this because you multiply by two. If you use x=[[0,0],[0,0]] as initialisation instead it works as expected.

Answer 4

Thank you all very much! 😃