.##### Height Height of a binary tree is count of longest path from the root node

def height(root):
    def helper(node, height):
        if node is None:
            return height
        left = 0
        right = 0
        if node.left is not None:
            left = helper(node.left, height + 1)
        if node.right is not None:
            right = helper(node.right, height + 1)
        return max(left, right) + 1
    return helper(root, 0)

Diameter

Diameter of a binary tree is count of the longest path between any two nodes in a binary tree

def diameter(root):
    diameter = 0
    def helper(node, height):
        if node is None:
            return height
        left = 0
        right = 0
        if node.left is not None:
            left = helper(node.left, height + 1)
        if node.right is not None:
            right = helper(node.right, height + 1)
        nonlocal diameter
        diameter = max(diameter, left + right)
        return max(left, right) + 1
    helper(root, 0)
    return diameter

Here for calculating diameter we consider each node as the curving point, and the node with maximum sum of height of left and right subtrees would be the longest path.