TypeError: "'TrieNode' object is not callable" - What is wrong with my code?

Question

I wrote this code to test prefix tree, but for some reason I get the error "TrieNode" object is not callable. Could someone help me resolve this error?

Why is the TrieNode() class not callable?

# Prefix Tree or Trie Data Structure
class TrieNode(object):
    def __init__(self):
        self.children = {}
        self.endOfWord = False

class Trie(object):
    def __init__(self):
        self.root = TrieNode()

def insert(self,word):
    node = self.root()
    for w in word:
        if w not in node.children:
            node.children[w] = TrieNode()
        node = node.children[w]
    node.endOfWord = True

def search(self,word):
    node = self.root
    for w in word:
        if w not in node.children:
            return False
        node = node.children[w]

    return node.endWord

def startsWith(self,prefix):
    node = self.root
    for w in prefix:
        if w not in node.children:
            return False
        node = node.children[w]
    return True

if __name__ == "__main__":
    trie = Trie()
    trie.insert("apple")
    trie.insert("apples")
    trie.insert("bat")
    trie.insert("bate")    
    print trie.search("apple")

Answer 1

It should read

def insert(self,word):
    node = self.root

Watch the root() -> root there. You are currently calling an instance attribute while in fact you only want to get a reference to it.