Comparing of elements in deque in python

Question

Can someone explain me, how works comparing of tree nodes in deque. For example, I pushed two children of two same binary trees in two different deques and I got deque1 = deque([TreeNode{val: 2, left: None, right: None}, TreeNode{val: 3, left: None, right: None}]), deque2 = deque([TreeNode{val: 2, left: None, right: None}, TreeNode{val: 3, left: None, right: None}]), but when I compared them, I got False. Why if two deques includes same nodes they are not equal? Thank you in advance!

Answer 1

You are right in thinking that if your deque objects contained equal objects then the two deque instances would also evaluate to be equal. The problem you are running into is that complex objects, like instances of TreeNode, by default are equal only if they are the same object, not necessarily if they have have the same contents. Here is a simplified example:

class TreeNode():
    def __init__(self,val, left, right):
        self.val = val
        self.left = left
        self.right = right
        
t1 = TreeNode(2, None, None)
t2 = TreeNode(2, None, None)

print(t1 == t2)
print(t1 == t1)

False
True

Take a look at this post for some tips on how to work around the issue.