construct_string_from_binary_tree.py

# 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 tree2str(self, root: TreeNode) -> str:
        if root is None: return ''
        if root.left is None and root.right is None: return f'{root.val}'
        if root.right is None: return f'{root.val}({self.tree2str(root.left)})'
        return f'{root.val}({self.tree2str(root.left)})({self.tree2str(root.right)})'