[Python] Infinite loop in multiple assignment in one line

I used these two versions of code in a LeetCode probleme.

1.

node.right = rights.pop()
node = node.right


node = node.right = rights.pop()


The first one got accepted but the second one went into an infinite loop and got time limit exceeded. But aren't they exactly the same???

The whole code is as follows:

# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def flatten(self, root: Optional[TreeNode]) -> None:
"""
Do not return anything, modify root in-place instead.
"""
rights = []
node = root
while node:
if node.right:
rights.append(node.right)
if node.left:
node.right = node.left
node.left = None
node = node.right
elif len(rights):
node = node.right = rights.pop()
'''
node.right = rights.pop()
node = node.right
'''
else:
return root

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