From 24731b078c0e30d0f9bdd4ed96749f33574860c6 Mon Sep 17 00:00:00 2001
From: Dylan Buchi <devybuchi@gmail.com>
Date: Tue, 2 Nov 2021 07:09:46 -0300
Subject: [PATCH] [mypy] fix type annotations in
`data_structures/queue/circular_queue_linked_list.py` (#5749)
* [mypy] fix type annotations in circular_queue_linked_list
* Remove 10 blank lines
Co-authored-by: Christian Clauss <cclauss@me.com>
---
.../queue/circular_queue_linked_list.py | 37 ++++++++++++-------
1 file changed, 24 insertions(+), 13 deletions(-)
diff --git a/data_structures/queue/circular_queue_linked_list.py b/data_structures/queue/circular_queue_linked_list.py
index 1878403b..e8c2b8bf 100644
--- a/data_structures/queue/circular_queue_linked_list.py
+++ b/data_structures/queue/circular_queue_linked_list.py
@@ -1,6 +1,8 @@
# Implementation of Circular Queue using linked lists
# https://en.wikipedia.org/wiki/Circular_buffer
+from __future__ import annotations
+
from typing import Any
@@ -18,8 +20,8 @@ class CircularQueueLinkedList:
"""
def __init__(self, initial_capacity: int = 6) -> None:
- self.front = None
- self.rear = None
+ self.front: Node | None = None
+ self.rear: Node | None = None
self.create_linked_list(initial_capacity)
def create_linked_list(self, initial_capacity: int) -> None:
@@ -27,7 +29,7 @@ class CircularQueueLinkedList:
self.front = current_node
self.rear = current_node
previous_node = current_node
- for i in range(1, initial_capacity):
+ for _ in range(1, initial_capacity):
current_node = Node()
previous_node.next = current_node
current_node.prev = previous_node
@@ -49,9 +51,14 @@ class CircularQueueLinkedList:
>>> cq.is_empty()
True
"""
- return self.front == self.rear and self.front.data is None
- def first(self) -> Any:
+ return (
+ self.front == self.rear
+ and self.front is not None
+ and self.front.data is None
+ )
+
+ def first(self) -> Any | None:
"""
Returns the first element of the queue
>>> cq = CircularQueueLinkedList()
@@ -74,7 +81,7 @@ class CircularQueueLinkedList:
'b'
"""
self.check_can_perform_operation()
- return self.front.data
+ return self.front.data if self.front else None
def enqueue(self, data: Any) -> None:
"""
@@ -92,11 +99,13 @@ class CircularQueueLinkedList:
...
Exception: Empty Queue
"""
+ if self.rear is None:
+ return
+
self.check_is_full()
- if self.is_empty():
- self.rear.data = data
- else:
+ if not self.is_empty():
self.rear = self.rear.next
+ if self.rear:
self.rear.data = data
def dequeue(self) -> Any:
@@ -117,6 +126,8 @@ class CircularQueueLinkedList:
Exception: Empty Queue
"""
self.check_can_perform_operation()
+ if self.rear is None or self.front is None:
+ return
if self.front == self.rear:
data = self.front.data
self.front.data = None
@@ -133,15 +144,15 @@ class CircularQueueLinkedList:
raise Exception("Empty Queue")
def check_is_full(self) -> None:
- if self.rear.next == self.front:
+ if self.rear and self.rear.next == self.front:
raise Exception("Full Queue")
class Node:
def __init__(self) -> None:
- self.data = None
- self.next = None
- self.prev = None
+ self.data: Any | None = None
+ self.next: Node | None = None
+ self.prev: Node | None = None
if __name__ == "__main__":