diff --git a/DIRECTORY.md b/DIRECTORY.md
index 78095b264..78afe07ec 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -622,6 +622,7 @@
   * [Boyer Moore Search](https://github.com/TheAlgorithms/Python/blob/master/strings/boyer_moore_search.py)
   * [Check Pangram](https://github.com/TheAlgorithms/Python/blob/master/strings/check_pangram.py)
   * [Is Palindrome](https://github.com/TheAlgorithms/Python/blob/master/strings/is_palindrome.py)
+  * [Jaro Winkler](https://github.com/TheAlgorithms/Python/blob/master/strings/jaro_winkler.py)
   * [Knuth Morris Pratt](https://github.com/TheAlgorithms/Python/blob/master/strings/knuth_morris_pratt.py)
   * [Levenshtein Distance](https://github.com/TheAlgorithms/Python/blob/master/strings/levenshtein_distance.py)
   * [Lower](https://github.com/TheAlgorithms/Python/blob/master/strings/lower.py)
diff --git a/data_structures/linked_list/circular_linked_list.py b/data_structures/linked_list/circular_linked_list.py
index cf523f0a4..290e30ebf 100644
--- a/data_structures/linked_list/circular_linked_list.py
+++ b/data_structures/linked_list/circular_linked_list.py
@@ -37,6 +37,15 @@ class CircularLinkedList:
         >>> cll.append(1)
         >>> len(cll)
         1
+        >>> cll.prepend(0)
+        >>> len(cll)
+        2
+        >>> cll.delete_front()
+        >>> len(cll)
+        1
+        >>> cll.delete_rear()
+        >>> len(cll)
+        0
         """
         return self.length
 
@@ -130,6 +139,9 @@ class CircularLinkedList:
         >>> cll.delete_front()
         >>> print(f"{len(cll)}: {cll}")
         1: <Node data=2>
+        >>> cll.delete_front()
+        >>> print(f"{len(cll)}: {cll}")
+        0: Empty linked list
         """
         if not self.head:
             raise IndexError("Deleting from an empty list")
@@ -137,7 +149,7 @@ class CircularLinkedList:
         current_node = self.head
 
         if current_node.next_ptr == current_node:
-            self.head, self.length = None, 0
+            self.head = None
         else:
             while current_node.next_ptr != self.head:
                 current_node = current_node.next_ptr
@@ -146,6 +158,8 @@ class CircularLinkedList:
             self.head = self.head.next_ptr
 
         self.length -= 1
+        if not self.head:
+            assert self.length == 0
 
     def delete_rear(self) -> None:
         """
@@ -162,6 +176,9 @@ class CircularLinkedList:
         >>> cll.delete_rear()
         >>> print(f"{len(cll)}: {cll}")
         1: <Node data=1>
+        >>> cll.delete_rear()
+        >>> print(f"{len(cll)}: {cll}")
+        0: Empty linked list
         """
         if not self.head:
             raise IndexError("Deleting from an empty list")
@@ -169,7 +186,7 @@ class CircularLinkedList:
         temp_node, current_node = self.head, self.head
 
         if current_node.next_ptr == current_node:
-            self.head, self.length = None, 0
+            self.head = None
         else:
             while current_node.next_ptr != self.head:
                 temp_node = current_node
@@ -178,6 +195,8 @@ class CircularLinkedList:
             temp_node.next_ptr = current_node.next_ptr
 
         self.length -= 1
+        if not self.head:
+            assert self.length == 0
 
 
 if __name__ == "__main__":
diff --git a/strings/jaro_winkler.py b/strings/jaro_winkler.py
index 73827c233..de0953854 100644
--- a/strings/jaro_winkler.py
+++ b/strings/jaro_winkler.py
@@ -34,7 +34,7 @@ def jaro_winkler(str1: str, str2: str) -> float:
                 matched.append(l)
                 _str2 = f"{_str2[0:_str2.index(l)]} {_str2[_str2.index(l) + 1:]}"
 
-        return ''.join(matched)
+        return "".join(matched)
 
     # matching characters
     matching_1 = get_matched_characters(str1, str2)
@@ -42,17 +42,22 @@ def jaro_winkler(str1: str, str2: str) -> float:
     match_count = len(matching_1)
 
     # transposition
-    transpositions = len(
-        [(c1, c2) for c1, c2 in zip(matching_1, matching_2) if c1 != c2]
-    ) // 2
+    transpositions = (
+        len([(c1, c2) for c1, c2 in zip(matching_1, matching_2) if c1 != c2]) // 2
+    )
 
     if not match_count:
         jaro = 0.0
     else:
-        jaro = 1 / 3 * (
-            match_count / len(str1)
-            + match_count / len(str2)
-            + (match_count - transpositions) / match_count)
+        jaro = (
+            1
+            / 3
+            * (
+                match_count / len(str1)
+                + match_count / len(str2)
+                + (match_count - transpositions) / match_count
+            )
+        )
 
     # common prefix up to 4 characters
     prefix_len = 0
@@ -65,7 +70,8 @@ def jaro_winkler(str1: str, str2: str) -> float:
     return jaro + 0.1 * prefix_len * (1 - jaro)
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     import doctest
+
     doctest.testmod()
     print(jaro_winkler("hello", "world"))