Add tests to __len__()

TheAlgorithms · cclauss · May 18, 2020 · Mar 25, 2020 · May 2, 2020 · May 18, 2020
commit 485b7d461c7554de47178b9708d2122bdac1db5b
diff --git a/data_structures/linked_list/singly_linked_list.py b/data_structures/linked_list/singly_linked_list.py
@@ -108,15 +108,34 @@ def __setitem__(self, index, data):
         current.data = data
 
     def __len__(self):
-        """Return length of linked list i.e. number of nodes """
-        cur_node = self.head
+        """
+        Return length of linked list i.e. number of nodes
+        >>> linked_list = LinkedList()
+        >>> len(linked_list)
+        0
+        >>> linked_list.insert_tail("head")
+        >>> len(linked_list)
+        1
+        >>> linked_list.insert_head("head")
+        >>> len(linked_list)
+        2
+        >>> _ = linked_list.delete_tail()
+        >>> len(linked_list)
+        1
+        >>> _ = linked_list.delete_head()
+        >>> len(linked_list)
+        0
+        """
+        if not self.head:
+            return 0
+
         count = 0
-
-        if not cur_node: return count #if list is empty
+        cur_node = self.head
         while cur_node.next:
-            count+=1
+            count += 1
             cur_node = cur_node.next
-        return count+1
+        return count + 1
+
 
 def main():
     A = LinkedList()