Update 0208-implement-trie-prefix-tree.py

It is better to use is None instead of == None when checking for None in Python. The reason is that `is` checks for identity (whether the two objects are the same object in memory), whereas == checks for equality (whether the two objects have the same value).

In Python, None is a singleton object, and using is to check for None is more efficient and idiomatic. It ensures that you are specifically checking if a variable is bound to the None object and not just a value that happens to be equivalent to None.

Author: cwillett

python/0208-implement-trie-prefix-tree.py

@@ -18,7 +18,7 @@ def insert(self, word: str) -> None:
         curr = self.root
         for c in word:
             i = ord(c) - ord("a")
-            if curr.children[i] == None:
+            if curr.children[i] is None:
                 curr.children[i] = TrieNode()
             curr = curr.children[i]
         curr.end = True
@@ -30,7 +30,7 @@ def search(self, word: str) -> bool:
         curr = self.root
         for c in word:
             i = ord(c) - ord("a")
-            if curr.children[i] == None:
+            if curr.children[i] is None:
                 return False
             curr = curr.children[i]
         return curr.end
@@ -42,7 +42,7 @@ def startsWith(self, prefix: str) -> bool:
         curr = self.root
         for c in prefix:
             i = ord(c) - ord("a")
-            if curr.children[i] == None:
+            if curr.children[i] is None:
                 return False
             curr = curr.children[i]
         return True