Help with classes, object and nodes

Question

Can someone please explain why is there an index passed in node_q ie why is it node_q[0] to access attributes of objects (parents, act, cost etc)

https://code.sololearn.com/ch8h61GK3IQZ/?ref=app
https://code.sololearn.com/ch8h61GK3IQZ/?ref=app

Answer 1

Have you read on basic concepts of object oriented programming?