diff --git a/Chapter04/append_at_any_location_singly_linkedlist.py b/Chapter04/append_at_any_location_singly_linkedlist.py
index c2e1f2f..fa8d1b7 100644
--- a/Chapter04/append_at_any_location_singly_linkedlist.py
+++ b/Chapter04/append_at_any_location_singly_linkedlist.py
@@ -28,19 +28,19 @@ def append_at_a_location(self, data, index):
         node = Node(data) 
         count = 1 
         while current: 
-            if count == 1:         
+            if index == 1:         
                 node.next = current 
                 self.head = node 
                 print(count) 
                 return 
-            elif index == index: 
+            elif count == index: 
                 node.next = current  
                 prev.next = node 
                 return 
             count += 1 
             prev = current 
             current = current.next 
-        if count < index: 
+        if count <= index: 
             print("The list has less number of elements") 
 
      
diff --git a/Chapter05/Stack_using_array.py b/Chapter05/Stack_using_array.py
index 20ad138..b76997f 100644
--- a/Chapter05/Stack_using_array.py
+++ b/Chapter05/Stack_using_array.py
@@ -1,51 +1,50 @@
 size = 3
-data = [0]*(size)   #Initialize the stack
+data = [0] * (size)  # Initialize the stack
 top = -1
 
+
 def push(x):
-  global top
-  if top >= size-1:
-    print("Stack Overflow")
-  else:
-    top = top + 1
-    data[top] = x
+    global top
+    if top >= size - 1:
+        print("Stack Overflow")
+    else:
+        top = top + 1
+        data[top] = x
 
 
 def pop():
-  global top
-  if top == -1:
-    print("Stack Underflow")
-  else:
-    top = top-1
-    data[top] = 0
-    return data[top+1]
+    global top
+    if top == -1:
+        print("Stack Underflow")
+    else:
+        item = data[top]
+        data[top] = 0
+        top = top - 1
+        return item
 
 
 def peek():
-  global top
-  if top == -1:
-    print("Stack is empty")
-  else:
-    print(data[top])
-
+    if top == -1:
+        print("Stack is empty")
+    else:
+        print(data[top])
 
 
-
-push('egg')
-push('ham')
-push('spam')
-push('new')
-push('new2')
+push("egg")
+push("ham")
+push("spam")
+push("new")
+push("new2")
 
 print(data[0 : top + 1])
 
 print(data[0 : top + 1])
+print(pop())
+print(pop())
+print(pop())
 pop()
-pop()
-pop()
-pop()
-print(data[0:top+1])
+print(data[0 : top + 1])
 
 peek()
 
-print(data[0:top+1])
+print(data[0 : top + 1])