len() funktion, fix pop() funktion, assertions in starten.py

linked-lists/linked_list.py

@@ -55,17 +55,38 @@ class LinkedList:
 
     def pop(self) -> int | None:
         if self.head is None:
-            self.head = None
             return None
 
         node = self.head
+
         assert node is not None
 
+        if node.next is None:
+            data = node.data
+            self.head = None
+            return data
+
+        assert node.next is not None
+
         while True:
-            if node.next is None:
-                return node.data
+            prev_node = node
             node = node.next
 
+            if node.next is None:
+                data = node.data
+                prev_node.next = None
+                return data
+
+    def len(self) -> int:
+        node = self.head
+        i = 0
+
+        while node is not None:
+            node = node.next
+            i += 1
+
+        return i
+
     def print(self):
         node = self.head
         while node is not None: