diff --git a/2-python/ch06/1-1.py b/2-python/ch06/1-1.py
index 257d2d6..e3b25b3 100644
--- a/2-python/ch06/1-1.py
+++ b/2-python/ch06/1-1.py
@@ -1,13 +1,10 @@
 class Solution:
-    def isPalindrome(self, s: str) -> bool:
-        strs = []
-        for char in s:
-            if char.isalnum():
-                strs.append(char.lower())
+    def isPalindrome(self, string: str) -> bool:
+        chars = [char.lower() for char in string if char.isalnum()]
 
         # 팰린드롬 여부 판별
-        while len(strs) > 1:
-            if strs.pop(0) != strs.pop():
+        while len(chars) > 1:
+            if chars.pop(0) != chars.pop():
                 return False
 
         return True
diff --git a/2-python/ch06/1-2.py b/2-python/ch06/1-2.py
index 1d9caa7..3f7d032 100644
--- a/2-python/ch06/1-2.py
+++ b/2-python/ch06/1-2.py
@@ -1,18 +1,12 @@
-import collections
-from typing import Deque
+from collections import deque
 
 
 class Solution:
-    def isPalindrome(self, s: str) -> bool:
-        # 자료형 데크로 선언
-        strs: Deque = collections.deque()
+    def isPalindrome(self, string: str) -> bool:
+        chars = deque(char.lower() for char in string if char.isalnum())
 
-        for char in s:
-            if char.isalnum():
-                strs.append(char.lower())
-
-        while len(strs) > 1:
-            if strs.popleft() != strs.pop():
+        while len(chars) > 1:
+            if chars.popleft() != chars.pop():
                 return False
 
         return True
diff --git a/3-linear-data-structures/ch07/10-2.py b/3-linear-data-structures/ch07/10-2.py
index 7e8492f..15d9cd7 100644
--- a/3-linear-data-structures/ch07/10-2.py
+++ b/3-linear-data-structures/ch07/10-2.py
@@ -3,12 +3,10 @@
 
 class Solution:
     def arrayPairSum(self, nums: List[int]) -> int:
-        sum = 0
         nums.sort()
 
-        for i, n in enumerate(nums):
-            # 짝수 번째 값의 합 계산
-            if i % 2 == 0:
-                sum += n
-
-        return sum
+        return sum(
+            number
+            for i, number in enumerate(nums)
+            if i % 2 == 0
+        )
diff --git a/3-linear-data-structures/ch07/11-1.py b/3-linear-data-structures/ch07/11-1.py
index 7a756ce..973e35b 100644
--- a/3-linear-data-structures/ch07/11-1.py
+++ b/3-linear-data-structures/ch07/11-1.py
@@ -3,15 +3,16 @@
 
 class Solution:
     def productExceptSelf(self, nums: List[int]) -> List[int]:
-        out = []
-        p = 1
-        # 왼쪽 곱셈
-        for i in range(0, len(nums)):
-            out.append(p)
-            p = p * nums[i]
-        p = 1
-        # 왼쪽 곱셈 결과에 오른쪽 값을 차례대로 곱셈
-        for i in range(len(nums) - 1, 0 - 1, -1):
-            out[i] = out[i] * p
-            p = p * nums[i]
-        return out
+        result = []
+
+        left_accumulated = 1
+        for number in nums:
+            result.append(left_accumulated)
+            left_accumulated *= number
+
+        right_accumulated = 1
+        for i in range(0, len(nums))[::-1]:
+            result[i] *= right_accumulated
+            right_accumulated *= nums[i]
+
+        return result
diff --git a/3-linear-data-structures/ch07/12-2.py b/3-linear-data-structures/ch07/12-2.py
index ebd2109..355f01b 100644
--- a/3-linear-data-structures/ch07/12-2.py
+++ b/3-linear-data-structures/ch07/12-2.py
@@ -5,7 +5,7 @@
 class Solution:
     def maxProfit(self, prices: List[int]) -> int:
         profit = 0
-        min_price = sys.maxsize
+        min_price = sys.maxsize  # or prices[0]
 
         # 최소값과 최대값 계속 갱신
         for price in prices:
diff --git a/3-linear-data-structures/ch08/13-4.py b/3-linear-data-structures/ch08/13-4.py
index 18f9617..7173926 100644
--- a/3-linear-data-structures/ch08/13-4.py
+++ b/3-linear-data-structures/ch08/13-4.py
@@ -12,7 +12,13 @@ def isPalindrome(self, head: ListNode) -> bool:
         # 런너를 이용해 역순 연결 리스트 구성
         while fast and fast.next:
             fast = fast.next.next
-            rev, rev.next, slow = slow, rev, slow.next
+
+            next_node = slow.next
+            previous_node = rev
+
+            rev = slow
+            rev.next = previous_node
+            slow = next_node
         if fast:
             slow = slow.next