inp = open('input.txt', 'r') # working with file
out = open('output.txt', 'a')


class Node:           # class to building tree
    def __init__(self, data):
        self.left = None
        self.right = None
        self.data = data

    def insert(self, data):
        if self.data is None:
            self.data = data
        else:
            if data < self.data:
                if self.left is None:
                    self.left = Node(data)
                else:
                    self.left.insert(data)
            elif data > self.data:
                if self.right is None:
                    self.right = Node(data)
                else:
                    self.right.insert(data)


n = Node()
data = inp.read()
n.insert(data)
out.write(str(data))
inp.close()
out.close() 

Parameter 'data' unfilled Shadows name 'data' from outer scope

I don't understand how to fix it. It would be grateful if you could help me with my problem.