diff --git a/21 BlackJack.py b/21 BlackJack.py
index dc93cf4..0c4a9e5 100644
--- a/21 BlackJack.py	
+++ b/21 BlackJack.py	
@@ -89,4 +89,4 @@ def calculate_hand(hand):
 
 # Dealer hits until their total is 17 or higher
 while total < 17:
-    dealer
+    raise NotImplementedError()
diff --git a/27.03 Library Item Inheritance.py b/27.03 Library Item Inheritance.py
index 492e103..09612ef 100644
--- a/27.03 Library Item Inheritance.py	
+++ b/27.03 Library Item Inheritance.py	
@@ -1,69 +1,84 @@
 import datetime
 import random
 
+
 class LibraryItem:
-    def __init__(self, t,a,i):
+    def __init__(self, t: str, a: str, i: str | int):
         self.__Title = t
         self.__AuthorArtist = a
         self.__ItemID = i
         self.__OnLoan = False
         self.__DueDate = datetime.date.today()
 
-    def GetTitle(self):
+    def GetTitle(self) -> str:
         return (self.__Title)
-    def GetAuthorArtist(self):
+
+    def GetAuthorArtist(self) -> str:
         return (self.__AuthorArtist)
-    def GetItemID(self):
+
+    def GetItemID(self) -> str | int:
         return (self.__ItemID)
 
-#lend book
-    
-    def ShowDetail(self):
+    #lend book
+
+    def ShowDetail(self) -> None:
         print("ID: ", self.GetItemID())
         print("Title: ", self.GetTitle())
         print("Author: ", self.__AuthorArtist)
 
+
 class Book(LibraryItem):
     def __init__(self, t, a, i):
         LibraryItem.__init__(self, t, a, i)
         self.__IsRequested = False
         self.__RequestedBy = 0
+
     def ShowDetail(self):
         LibraryItem.ShowDetail(self)
         #print("is requested: ", self.__IsRequested)
 
+
 class CD(LibraryItem):
     def __init__(self, t, a, i):
         LibraryItem.__init__(self, t, a, i)
         self.__Genre = ""
+
     def GetGenre(self):
         return (self.__Genre)
+
     def SetGenre(self, g):
         self.__Genre = g
+
+
 class Borrower:
     def __init__(self, n, e):
         self.__BorrowerName = n
         self.__Email = e
-        self.__BorrowerID = random.randint(100,200)
+        self.__BorrowerID = random.randint(100, 200)
         self.__ItemsOnLoan = 0
 
     def GetBorrowerName(self):
         return self.__BorrowerName
+
     def GetEmail(self):
         return self.__Email
+
     def GetBorrowerID(self):
         return self.__BorrowerID
+
     def GetItemsOnLoan(self):
         return self.__ItemsOnLoan
+
     def UpdateItemsOnLoan(self):
         self.__ItemsOnLoan += 1
-    
+
     def PrintDetail(self):
         print("ID: ", self.GetBorrowerID())
         print("Name: ", self.GetBorrowerName())
         print("Email: ", self.GetEmail())
         print(f"There are {self.__ItemsOnLoan} items borrowed.")
-        
+
+
 ##Title=input("Enter book title: ")
 ##Author = input("Enter book author: ")
 ##ItemID = random.randint(10000, 50000)
diff --git a/27.05 Library Item Borrower.py b/27.05 Library Item Borrower.py
index 492e103..4b69a77 100644
--- a/27.05 Library Item Borrower.py	
+++ b/27.05 Library Item Borrower.py	
@@ -2,23 +2,23 @@
 import random
 
 class LibraryItem:
-    def __init__(self, t,a,i):
+    def __init__(self, t:str,a:str,i:str|int):
         self.__Title = t
         self.__AuthorArtist = a
         self.__ItemID = i
         self.__OnLoan = False
         self.__DueDate = datetime.date.today()
 
-    def GetTitle(self):
+    def GetTitle(self) -> str:
         return (self.__Title)
-    def GetAuthorArtist(self):
+    def GetAuthorArtist(self) -> str:
         return (self.__AuthorArtist)
-    def GetItemID(self):
+    def GetItemID(self) -> str | int:
         return (self.__ItemID)
 
 #lend book
     
-    def ShowDetail(self):
+    def ShowDetail(self) -> None:
         print("ID: ", self.GetItemID())
         print("Title: ", self.GetTitle())
         print("Author: ", self.__AuthorArtist)
diff --git a/27.06 Library Items.py b/27.06 Library Items.py
index a1d16b6..40ba65e 100644
--- a/27.06 Library Items.py	
+++ b/27.06 Library Items.py	
@@ -19,7 +19,7 @@ def GetItemID(self):
     def Borrow(self, bid):
         self.__BorrowerID = bid
         self.__OnLoan = True
-        self.__DueDate = datetime.date.today()+7
+        self.__DueDate = datetime.date.today() + datetime.timedelta(weeks=1)
     def Return(self):
         self.__BorrowerID = 0
         self.__OnLoan = False
@@ -76,7 +76,7 @@ def PrintDetail(self):
         print(f"There are {self.__ItemsOnLoan} items borrowed.")
 
 def Menu():
-    pass
+    raise NotImplementedError()
 
 ##Title=input("Enter book title: ")
 ##Author = input("Enter book author: ")
diff --git a/27.07 Library with Utility.py b/27.07 Library with Utility.py
index d6d67c9..43c45b4 100644
--- a/27.07 Library with Utility.py	
+++ b/27.07 Library with Utility.py	
@@ -19,7 +19,7 @@ def GetItemID(self):
     def Borrow(self, bid):
         self.__BorrowerID = bid
         self.__OnLoan = True
-        self.__DueDate = datetime.date.today()+7
+        self.__DueDate = datetime.date.today()+datetime.timedelta(weeks=1)
     def Return(self):
         self.__BorrowerID = 0
         self.__OnLoan = False
@@ -77,7 +77,7 @@ def PrintDetail(self):
 
 def Menu():
     choice = 't'
-    while choice not in (0,1,2,3,4,5,6,7,8,9):
+    while choice not in range(0,10):
         print("1 – Add a new borrower")
         print("2 – Add a new book")
         print("3 – Add a new CD")
@@ -107,20 +107,8 @@ def main():
             name =  input("Enter name of borrower ")
             email = input("Enter email of borrower ")
             Borrowers.append(Borrower(name,email))
-        elif choice ==2:
-            pass
-        elif choice==3:
-            pass
-        elif choice==4:
-            pass
-        elif choice==5:
-            pass
-        elif choice==6:
-            pass
-        elif choice==7:
-            pass
-        elif choice==8:
-            pass
+        elif choice in range(2, 9):
+            print("Not implemented yet")
         elif choice==9:
             print(Borrowers[0].GetBorrowerName())
         choice = Menu()
diff --git a/9 - 17-9 - car record using classes.py b/9 - 17-9 - car record using classes.py
index cb6abc5..71b5217 100644
--- a/9 - 17-9 - car record using classes.py	
+++ b/9 - 17-9 - car record using classes.py	
@@ -1,5 +1,6 @@
 import pickle
 
+
 class CarRecord:
     def __init__(self):
         self.VehicleID = ""
@@ -8,11 +9,12 @@ def __init__(self):
         self.EngineSize = 0
         self.PurchaseSize = 0.00
 
-Car = [None]*10 # Create an empty array of 10 objects called Car
+
+Car = [CarRecord()] * 10  # Create an empty array of 10 objects called Car
 
 for i in range(10):
-    ThisCar = CarRecord() # Create an instance of class CarRecord named ThisCar
-    Car[i] = ThisCar # Assign reference of this Car object to array location
+    ThisCar = CarRecord()  # Create an instance of class CarRecord named ThisCar
+    Car[i] = ThisCar  # Assign reference of this Car object to array location
 
 Car[1].EngineSize = 2500
 Car[5].EngineSize = 3000
@@ -36,17 +38,17 @@ def __init__(self):
 Car[1].EngineSize = 3500
 Car[5].EngineSize = 8000
 
-Car2 = [None]
+Car2 = [CarRecord()] * 10
 #for i in range(10):
-    #ThisCar = CarRecord()
-    #Car2[i] = ThisCar
+#ThisCar = CarRecord()
+#Car2[i] = ThisCar
 
 CarFile = open('Cars.DAT', 'rb')
 
 while True:
     try:
         Car2.append(pickle.load(CarFile))
-    except (EOFError):
+    except EOFError:
         break
 
 CarFile.close()
@@ -55,5 +57,6 @@ def __init__(self):
 for i in range(10):
     print(Car2[i].EngineSize)
     print("")
+
 #print(Car[1].EngineSize)
 #print(Car[5].EngineSize)
diff --git a/A2 Modular Search and Sort.py b/A2 Modular Search and Sort.py
index b753577..c1e90c0 100644
--- a/A2 Modular Search and Sort.py	
+++ b/A2 Modular Search and Sort.py	
@@ -1,92 +1,77 @@
 import random
+
 SIZE = 7
-data = [random.randint(1,20) for x in range (SIZE)]
+data = [random.randint(1, 20) for x in range(SIZE)]
+
+
 #print(data)
 
-def LinearSearch(data):
+def LinearSearch(data: list) -> None:
     key = int(input('Enter value to search'))
     found = False
 
-    for x in range (SIZE):
+    for x in range(SIZE):
         if key == data[x]:
             print("found at location: ", x)
             found = True
 
-    if found==False:
+    if found == False:
         print('value not found')
 
+
 def BubbleSort(data):
-    temp = 0
-    n = 30 -1
-    for i in range (SIZE):
+    n = 30 - 1
+    for i in range(SIZE):
         for j in range(n):
-            if data[j]>data[j+1]:
+            if data[j] > data[j + 1]:
                 temp = data[j]
-                data[j] = data [j+1]
-                data [j+1] = temp
-        n = n -1
+                data[j] = data[j + 1]
+                data[j + 1] = temp
+        n = n - 1
+
 
 def InsertionSort(data):
-    ItemToBeInserted = 0
-    CurrentItem = 0
-    index = 0
-    
     for index in range(len(data)):
         ItemToBeInserted = data[index]
-        CurrentItem = index -1
-        while (data[CurrentItem]>ItemToBeInserted and
-               CurrentItem>-1):
-            data[CurrentItem+1]=data[CurrentItem]
-            CurrentItem-=1
-        data[CurrentItem+1] = ItemToBeInserted
+        CurrentItem = index - 1
+        while (data[CurrentItem] > ItemToBeInserted and
+               CurrentItem > -1):
+            data[CurrentItem + 1] = data[CurrentItem]
+            CurrentItem -= 1
+        data[CurrentItem + 1] = ItemToBeInserted
         #print(data)
 
-def BinarySearch(data):
+
+def BinarySearch(data:list) -> None:
     lowerBound = 0
-    upperBound = len(data)-1
-    
+    upperBound = len(data) - 1
+    mid = -1
+
     key = int(input("Enter value to search: "))
     found = False
-    searchFailed = False
-    while not searchFailed and not found:
+
+    while (not found) and lowerBound <= upperBound:
         mid = lowerBound + (upperBound - lowerBound) // 2
-        
-        if data[mid]==key:
+
+        if data[mid] == key:
             #print('found at location : ', mid)
             found = True
-        elif data[mid]>key:
-            upperBound =  mid - 1
+        elif data[mid] > key:
+            upperBound = mid - 1
         else:
-            lowerBound = mid + 1 
-        if lowerBound > upperBound:
-            print('search failed')
-            searchFailed = True
-      
-    if found:
+            lowerBound = mid + 1
+
+    if found and mid != -1:
         print(mid)
     else:
         print('value does not exist in the list')
 
+
 #BubbleSort(data)
 InsertionSort(data)
 print(data)
 BinarySearch(data)
 
-
-
-
-
-
-
-
-
-
-
-
-
-
-            
-  
 #LinearSearch(data)
 BubbleSort(data)
 print(data)
diff --git a/LinearSearch.py b/LinearSearch.py
index b14ab09..6b837f8 100644
--- a/LinearSearch.py
+++ b/LinearSearch.py
@@ -1,13 +1,15 @@
 import random
 
-data = [random.randint(1,20) for x in range (30)]
+SIZE = 30
+
+data = [random.randint(1,20) for x in range (SIZE)]
 #print(data)
 
 def LinearSearch(data):
     key = int(input('Enter value to search'))
     found = False
 
-    for x in range (30):
+    for x in range (SIZE):
         if key == data[x]:
             print("found at location: ", x)
             found = True
@@ -16,9 +18,8 @@ def LinearSearch(data):
         print('value not found')
 
 def BubbleSort(data):
-    temp = 0
-    n = 30 -1
-    for i in range (30):
+    n = SIZE - 1
+    for i in range (SIZE):
         for j in range(n):
             if data[j]>data[j+1]:
                 temp = data[j]
@@ -27,10 +28,6 @@ def BubbleSort(data):
         n = n -1
 
 def InsertionSort(data):
-    ItemToBeInserted = 0
-    CurrentItem = 0
-    index = 0
-    
     for index in range(len(data)):
         ItemToBeInserted = data[index]
         CurrentItem = index -1
@@ -43,6 +40,7 @@ def InsertionSort(data):
 def BinarySearch(data):
     lowerBound = 0
     upperBound = len(data)-1
+    mid = -1
     
     key = int(input("Enter value to search: "))
     found = False
diff --git a/LinkedList.py b/LinkedList.py
index 593c317..e42f2be 100644
--- a/LinkedList.py
+++ b/LinkedList.py
@@ -1,73 +1,77 @@
+import dataclasses
+
 SIZE = 12
 
+
+@dataclasses.dataclass
 class Node:
-    data = ''
+    data = None
     nextP = 0
 
 
-myList = [Node() for x in range (SIZE)]
+myList = [Node() for x in range(SIZE)]
 for x in range(SIZE):
-    myList[x].nextP=x+1
-    myList[11].nextP=-1
+    myList[x].nextP = x + 1
+    myList[11].nextP = -1
 freeListPointer = 0
 startPointer = -1
-        
 
 for x in range(SIZE):
     print(self.thisList[x].data, end=' ')
     print(self.thisList[x].nextP)
 
-if self.__freeListPointer!= -1:
+if self.__freeListPointer != -1:
     newNodePtr = self.__freeListPointer
     self.__thisList[newNodePtr] = s
     self.__freeListPointer = self.__next[freeListPointer]
     #find insertion point
-            
+
 
 def printAll(self):
     thisPtr = startPointer
     while self.__next != -1:
         print(self.__thisList[thisPtr])
-        thisPtr+=1
+        thisPtr += 1
+
 
 def insert(self, s):
-        if nextFree == 0:
-            print('List is full')
-        else:
-            Node[nextFree].Data = s
-        if start == 0:
+    if nextFree == 0:
+        print('List is full')
+    else:
+        Node[nextFree].Data = s
+    if start == 0:
+        start = nextFree
+        temp = Node[nextFree].link
+        Node[nextFree].link = 0
+        nextFree = Temp
+    else:
+        #traverse the list - starting at start to find
+        # the position at which to insert the new item
+        Temp = Node[nextFree].link
+        if s < Node[start].data:
+            #new item will become the start of the list
+            nodeNext[free].link = start
             start = nextFree
-            temp = Node[nextFree].link
-            Node[nextFree].link =0
-            nextFree = Temp
+            nextFree.Temp
         else:
-            #traverse the list - starting at start to find
-            # the position at which to insert the new item
-            Temp = Node[nextFree].link
-            if s < Node[start].data:
-                #new item will become the start of the list
-                nodeNext[free].link = start
-                start = nextFree
-                nextFree.Temp
-            else:
-                #the new item is not at the start of the list
-                previous = 0
-                current = start
-                found = False
-                while found == False and current !=0:
-                    if s <= Node[current].data:
-                        Node[previous].link = nextFree
-                        Node[nextFree].link = current
-                        found = True
-                    else:
-                        nextFree = Temp
-                        #move to the next node
-                        previous = current
-                        current = Node[current].link
-                if current==0:
+            #the new item is not at the start of the list
+            previous = 0
+            current = start
+            found = False
+            while found == False and current != 0:
+                if s <= Node[current].data:
                     Node[previous].link = nextFree
-                    Node[nextFree].link = 0
+                    Node[nextFree].link = current
+                    found = True
+                else:
                     nextFree = Temp
+                    #move to the next node
+                    previous = current
+                    current = Node[current].link
+            if current == 0:
+                Node[previous].link = nextFree
+                Node[nextFree].link = 0
+                nextFree = Temp
 
 
 myList = linkedList()
diff --git a/PassByVal.py b/PassByVal.py
index 31f943b..5929899 100644
--- a/PassByVal.py
+++ b/PassByVal.py
@@ -5,6 +5,7 @@ def main():
     print(m) #10
     check(m)
     print(m) #10
+    assert m == 10
 
 def check(n):
     n+=10
diff --git a/Recursion Binary Conversion.py b/Recursion Binary Conversion.py
index 7939293..ad56955 100644
--- a/Recursion Binary Conversion.py	
+++ b/Recursion Binary Conversion.py	
@@ -1,9 +1,10 @@
 def X(n):
-    if n==0  or n==1:
-        print(n,end='')
+    if n == 0 or n == 1:
+        print(n, end='')
     else:
-        X(n//2)
+        X(n // 2)
         print(n % 2, end='')
 
+
 if __name__ == "__main__":
     X(36)
diff --git a/Recursion/BinarySearchRecursive.py b/Recursion/BinarySearchRecursive.py
index 1e7eefd..65c061a 100644
--- a/Recursion/BinarySearchRecursive.py
+++ b/Recursion/BinarySearchRecursive.py
@@ -7,7 +7,7 @@ def BinarySearch(item, lBound, uBound, myList):
     if uBound < lBound:
         return -1 #item not in the list
 
-    index = (uBound + lBound) // 2
+    index = uBound + (lBound - uBound) // 2
     ThisItem = myList[index]
 
     if item == ThisItem: #base case 2 item found
diff --git a/Recursion/BinaryToDenary Recursive.py b/Recursion/BinaryToDenary Recursive.py
index 9fb5915..8e73673 100644
--- a/Recursion/BinaryToDenary Recursive.py	
+++ b/Recursion/BinaryToDenary Recursive.py	
@@ -1,16 +1,18 @@
-def DenToBin(n):    #recursive
-    if n==0  or n==1: #base case
-        print(n,end='')
-    else:           #general case
-        DenToBin(n//2)
+def DenToBin(n):  # recursive
+    if n == 0 or n == 1:  # base case
+        print(n, end='')
+    else:  # general case
+        DenToBin(n // 2)
         print(n % 2, end='')
 
-def DenToBinary(n): #iterative solution
+
+def DenToBinary(n):  # iterative solution
     s = ''
-    while n !=0:
-        s=str(n%2)+s
-        n//=2
+    while n != 0:
+        s = str(n % 2) + s
+        n //= 2
     print(s)
 
+
 if __name__ == "__main__":
     DenToBin(12)
diff --git a/Recursion/BubbleSortRecursive (2).py b/Recursion/BubbleSortRecursive (2).py
index ba78580..8a6af04 100644
--- a/Recursion/BubbleSortRecursive (2).py	
+++ b/Recursion/BubbleSortRecursive (2).py	
@@ -27,28 +27,28 @@
 print("sorted")
 print(MyList)
 
-    def bubbleSortRecursive(self, n=None): 
-        if n is None: 
-            n = self.length 
-        count = 0
-  
-        # Base case 
-        if n == 1: 
-            return
-        # One pass of bubble sort. After 
-        # this pass, the largest element 
-        # is moved (or bubbled) to end. 
-        for i in range(n - 1): 
-            if self.array[i] > self.array[i + 1]: 
-                self.array[i], self.array[i +
-                1] = self.array[i + 1], self.array[i] 
-                count = count + 1
-  
-        # Check if any recursion happens or not 
-          # If any recursion is not happen then return 
-        if (count==0): 
-            return
-  
-        # Largest element is fixed, 
-        #  recur for remaining array 
-        self.bubbleSortRecursive(n - 1)
+def bubbleSortRecursive(self:list, n=None):
+    if n is None:
+        n = len(self)
+    count = 0
+
+    # Base case
+    if n == 1:
+        return
+    # One pass of bubble sort. After
+    # this pass, the largest element
+    # is moved (or bubbled) to end.
+    for i in range(n - 1):
+        if self.array[i] > self.array[i + 1]:
+            self.array[i], self.array[i +
+            1] = self.array[i + 1], self.array[i]
+            count = count + 1
+
+    # Check if any recursion happens or not
+      # If any recursion is not happen then return
+    if (count==0):
+        return
+
+    # Largest element is fixed,
+    #  recur for remaining array
+    self.bubbleSortRecursive(n - 1)
diff --git a/Recursion/BubbleSortRecursive.py b/Recursion/BubbleSortRecursive.py
index 21bbdb2..913f3c1 100644
--- a/Recursion/BubbleSortRecursive.py
+++ b/Recursion/BubbleSortRecursive.py
@@ -1,4 +1,7 @@
 import random
+
+from Recursion.BinarySearchRecursive import myList
+
 MaxIndex = 12
 
 MyList = [random.randint(1,100) for x in range(MaxIndex)]
@@ -9,7 +12,7 @@
 
 
 
-def bubbleSortRecursive(myList, n): 
+def bubbleSortRecursive(myList:list, n:int= len(myList)):
 ##    if n is None: 
 ##        n = self.length 
     swapped = False
diff --git a/Recursion/Factorial.py b/Recursion/Factorial.py
index 3b8a2ce..3ecfa93 100644
--- a/Recursion/Factorial.py
+++ b/Recursion/Factorial.py
@@ -1,11 +1,12 @@
 def main():
     print(Factorial(100))
 
-def Factorial(n):
-    if n==1 :
-        return n
+
+def Factorial(n:int):
+    if n == 0:
+        return 1
     else:
-        return n*Factorial(n-1)
+        return n * Factorial(n - 1)
 
 
 main()
diff --git a/Recursion/Fibonacci.py b/Recursion/Fibonacci.py
index fddb17c..dc8fb77 100644
--- a/Recursion/Fibonacci.py
+++ b/Recursion/Fibonacci.py
@@ -1,11 +1,12 @@
 def main():
     print(Fibonacci(5))
 
-def Fibonacci(n):
-    if n==1 :
-        return n
+
+def Fibonacci(n: int):
+    if n == 0:
+        return 0
     else:
-        return n+Fibonacci(n-1)
+        return n + Fibonacci(n - 1)
 
 
 main()
diff --git a/Recursion/GCD.py b/Recursion/GCD.py
index a81cde3..3b78943 100644
--- a/Recursion/GCD.py
+++ b/Recursion/GCD.py
@@ -1,17 +1,21 @@
 def main():
-    print(HCF(75,30))
-    print(GCD(75,30))
+    print(HCF(75, 30))
+    print(GCD(75, 30))
 
-def HCF(n1,n2):
-    if n2!=0 :
-        return HCF(n2,n1%n2)
+
+def HCF(n1: int, n2: int):
+    if n2 != 0:
+        return HCF(n2, n1 % n2)
     else:
         return n1
 
-def GCD(n1,n2):
-    while n2!=0:
-        r = n1 %n2
-        n1=n2
+
+def GCD(n1: int, n2: int):
+    while n2 != 0:
+        r = n1 % n2
+        n1 = n2
         n2 = r
     return n1
+
+
 main()
diff --git a/Recursion/HexToDenRecursive.py b/Recursion/HexToDenRecursive.py
index a642163..561317b 100644
--- a/Recursion/HexToDenRecursive.py
+++ b/Recursion/HexToDenRecursive.py
@@ -1,21 +1,18 @@
-def HexToDen(HexString):
-    if len(HexString)==1
-        HexDigit = HexString[0]
-        if HexDigit == 'a':
-            HexValue = 10
-        elif HexDigit == 'b':
-            HexValue = 11
-        elif HexDigit == 'c':
-            HexValue = 12
-        elif HexDigit == 'd':
-            HexValue = 13
-        elif HexDigit == 'e':
-            HexValue = 14
-        elif HexDigit == 'f':
-            HexValue = 15
-        else:
-            HexValue = int(HexDigit)
-        ValueSoFar = HexToDen(HexString[1:]) *16 + HexValue
-        return ValueSoFar 
+MAP: dict[str, int] = {
+    'a':10, 'b':11, 'c':12, 'd':13, 'e':14, 'f':15,
+}
+
+def HexToDen(HexString:str) -> int:
+    if len(HexString) == 0:
+        raise ValueError('Hex string must not be empty')
+    HexDigit = HexString[0]
+    HexValue = MAP.get(HexDigit, None)
+    if not HexValue:
+        HexValue = int(HexDigit)
+    if len(HexString) == 1:
+        return HexValue
+    ValueSoFar = HexToDen(HexString[1:]) * 16 + HexValue
+    return ValueSoFar
+
 
 print(HexToDen('ff'))
diff --git a/Recursion/Iterative vs Recursive.py b/Recursion/Iterative vs Recursive.py
index fc3d36e..78b9d39 100644
--- a/Recursion/Iterative vs Recursive.py	
+++ b/Recursion/Iterative vs Recursive.py	
@@ -3,18 +3,16 @@
 ##        print(x)
 
 
-def countDown(n):
-    if n !=-1:
+def countDown(n:int):
+    assert n >= -1
+    if n != -1:
         print(n)
-        countDown(n-1)
+        countDown(n - 1)
+
+
 countDown(7)
 
 
-def CountUp(n):
-    for x in range(n+1):
+def CountUp(n:int):
+    for x in range(n + 1):
         print(x)
-
-def CountDown(n):
-    print(n)
-    if n!=1:
-      CountDown(n-1)
diff --git a/Recursion/LinkedList2ArrayRecursion.py b/Recursion/LinkedList2ArrayRecursion.py
index 225eade..2a818a2 100644
--- a/Recursion/LinkedList2ArrayRecursion.py
+++ b/Recursion/LinkedList2ArrayRecursion.py
@@ -1,22 +1,24 @@
 NULL = -1
 SIZE = 7
-#Data = [""]* SIZE
+# Data = [""]* SIZE
 Data = ["Hamza", "Abbad", "Faheem", "Ibbad", "Zeeshan", "Muntazir", "Bashir"]
-Next = [3,6,0,5,-1,4,2]
-#Next = [0] * SIZE
+Next = [3, 6, 0, 5, -1, 4, 2]
+# Next = [0] * SIZE
 Free = 0
-#Start = NULL
+# Start = NULL
 Start = 1
 
+
 def init():
     global Data
     global Next
     global SIZE
-    
+
     for x in range(SIZE):
-        Next[x] = x+1
-    Next[SIZE-1]=NULL
-    
+        Next[x] = x + 1
+    Next[SIZE - 1] = NULL
+
+
 def output():
     global Data
     global Next
@@ -24,39 +26,43 @@ def output():
 
     idx = Start
     print(Data[idx])
-    while Next[idx] !=NULL:
+    while Next[idx] != NULL:
         idx = Next[idx]
         print(Data[idx])
 
-def outputRecursive(Data , Next , idx):
-    '''arrat with data array with pointers'''
-    #idx = Start
-    if Next[idx]==NULL:
-        print( Data[idx])
+
+def outputRecursive(Data: list, Next: list[int], idx: int):
+    """arrat with data array with pointers"""
+    # idx = Start
+    if Next[idx] == NULL:
+        print(Data[idx])
     else:
         outputRecursive(Data, Next, Next[idx])
         print(Data[idx])
-    
+
+
 def search(val):
     global Data
     global Next
     global Start
-    
+
     isFound = False
     idx = Start
-    if Data[idx]==val: isFound=True
-    
-    while Next[idx] !=NULL:
+    if Data[idx] == val: isFound = True
+
+    while Next[idx] != NULL:
         idx = Next[idx]
-        if Data[idx]==val: isFound=True
+        if Data[idx] == val: isFound = True
     return isFound
-def main():
 
-    #init()
+
+def main():
+    # init()
     outputRecursive(Data, Next, Start)
     print()
     output()
-    #print(search("Faheem"))
-    #print(search("Ali"))
+    # print(search("Faheem"))
+    # print(search("Ali"))
+
 
 main()
diff --git a/Recursion/RecursiveCountDown.py b/Recursion/RecursiveCountDown.py
index 148cc35..9093360 100644
--- a/Recursion/RecursiveCountDown.py
+++ b/Recursion/RecursiveCountDown.py
@@ -1,16 +1,16 @@
-
-def fibRecursive(n):
-    if n==1:
-        return 1
+def fibRecursive(n:int):
+    if n == 0:
+        return 0
     else:
-        return n+fibRecursive(n-1)
-    
-def fibIterative(n):
+        return n + fibRecursive(n - 1)
+
+
+def fibIterative(n:int):
     total = 0
-    for x in range (1,n+1):
-        total +=x
+    for x in range(1, n + 1):
+        total += x
     return total
 
+
 print(fibIterative(7))
 print(fibRecursive(7))
-
diff --git a/Recursion/RecursiveDenToBin.py b/Recursion/RecursiveDenToBin.py
index f0f88ca..b3b8d91 100644
--- a/Recursion/RecursiveDenToBin.py
+++ b/Recursion/RecursiveDenToBin.py
@@ -1,12 +1,12 @@
-def DenToBin(n:int):
-    b=n%2
-    if n==0:
-        print('0',end='')
-    elif n==1:
-        print('1',end='')
+def DenToBin(n: int):
+    b = n % 2
+    if n == 0:
+        print('0', end='')
+    elif n == 1:
+        print('1', end='')
     else:
-        DenToBin(n//2)
-        print(str(b),end='')
+        DenToBin(n // 2)
+        print(str(b), end='')
+
 
 DenToBin(121)
-        
diff --git a/Recursion/RecursiveReverseString.py b/Recursion/RecursiveReverseString.py
index d7e9608..9b59a30 100644
--- a/Recursion/RecursiveReverseString.py
+++ b/Recursion/RecursiveReverseString.py
@@ -1,37 +1,34 @@
-def ReverseStrRecursive(s):
+def ReverseStrRecursive(s: str) -> str:
     print(s[-1], end='')
-    if len(s)>1:
+    if len(s) > 1:
         ReverseStrRecursive(s[:-1])
+    return ""
 
 
-
-def reverseStr(s):
+def reverseStr(s: str) -> str:
     rs = ''
-    for x in range(len(s)-1, -1, -1):
+    for x in range(len(s) - 1, -1, -1):
         rs += s[x]
     return rs
 
 
-
-print(ReverseStrRecursive('faheem'))
-print(reverseStr('faheem'))
-print(CountUp(7))
-print(CountDown(7))
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+def CountUp(n: int):
+    for x in range(n + 1):
+        print(x)
 
 
+def CountDown(n: int):
+    """
+        In the best programming language, this would be (conceptually):
+        while (n > 0)
+            println (n--);
+    """
+    if n > 0:
+        print(n)
+        CountDown(n - 1)
 
 
+print(ReverseStrRecursive('faheem'))
+print(reverseStr('faheem'))
+CountUp(7)
+CountDown(7)
diff --git a/Recursion/Total.py b/Recursion/Total.py
index da92ace..3363017 100644
--- a/Recursion/Total.py
+++ b/Recursion/Total.py
@@ -1,12 +1,12 @@
 def main():
     print(Total())
 
+
 def Total():
-    x = int(input("Enter a number [0 to end] "))
-    if x==0 : #base
+    x = int(input("Enter a number [0, inf) : "))
+    if x == 0:  # base
         return x
-    else:
-        return x+Total()
+    return x + Total()
 
 
 main()
diff --git a/Recursion/guess recursive.py b/Recursion/guess recursive.py
index a14a42f..0d8000f 100644
--- a/Recursion/guess recursive.py	
+++ b/Recursion/guess recursive.py	
@@ -1,13 +1,22 @@
 import random
-def guess(n):
-    inp=int(input('Enter a number between 1 and 10: '))
-    if(n==inp):
+
+
+def guess(n: int):
+    try:
+        inp = int(input('Enter a number between 1 and 10: '))
+    except ValueError:
+        print('Invalid input')
+        guess(n)
+        return #unreachable
+    if (n == inp):
         print('Congratulation! You guessed it correctly.')
         return
-    elif(n>inp):
+    elif (n > inp):
         print('Enter a bigger number')
         guess(n)
     else:
         print('Enter a lesser number')
         guess(n)
-guess(random.randint(1,11))
+
+
+guess(random.randint(1, 11))
diff --git a/Recursion/isPrime.py b/Recursion/isPrime.py
index d3be7b2..fa116bc 100644
--- a/Recursion/isPrime.py
+++ b/Recursion/isPrime.py
@@ -1,25 +1,25 @@
 ##student work
+#edited slightly
 
-global i
 i = 2
-global prime
 prime = True
 
 
 def isPrime(n: int):
     global prime, i
-    if n == 1: # base case 1
+    if n == 1:  # base case 1
         prime = False
-    elif n == 2 or n == 3: # base case 2
+    elif n == 2 or n == 3:  # base case 2
         prime = True
     elif n > 3:
         if n > i:
-            if n%i == 0:
+            if n % i == 0:
                 prime = False
             else:
-                i+=1
+                i += 1
                 isPrime(n)
 
+
 isPrime(3)
 print(prime)
 isPrime(4)
diff --git a/Recursion/palindrome recursive.py b/Recursion/palindrome recursive.py
index e4dd26b..236e8b4 100644
--- a/Recursion/palindrome recursive.py	
+++ b/Recursion/palindrome recursive.py	
@@ -1,4 +1,4 @@
-def is_palindrome(word):
+def is_palindrome(word: str):
     """Return True if word is a palindrome, False if not."""
     if len(word) <= 1:
         return True
diff --git a/Recursion/primeRecursive.py b/Recursion/primeRecursive.py
index 0c60421..a1e38f4 100644
--- a/Recursion/primeRecursive.py
+++ b/Recursion/primeRecursive.py
@@ -1,17 +1,17 @@
-def prime(n,d=3):
-    if n==2 or n==3:
+def prime(n: int, d: int = 3):
+    if n == 2 or n == 3:
         return True
-    elif n==1:
+    elif n == 1:
         return False
-    elif n%2==0:
+    elif n % 2 == 0:
         return False
-    elif n%d==0:
+    elif n % d == 0:
         return False
-    elif d>=n//3:
+    elif d >= n // 3:
         return True
     else:
-        return prime(n,d+2) #general case
-        
+        return prime(n, d + 2)  # general case
+
 
 print(prime(1))
 print(prime(2))
diff --git a/Recursion/quick sort recursive.py b/Recursion/quick sort recursive.py
index 819ccdc..0d4df33 100644
--- a/Recursion/quick sort recursive.py	
+++ b/Recursion/quick sort recursive.py	
@@ -1,13 +1,15 @@
 import statistics
 import random
 
-def get_random_numbers(length, minimum=1, maximum=100):
+
+def get_random_numbers(length: int, minimum: int = 1, maximum: int = 100):
     numbers = []
     for _ in range(length):
         numbers.append(random.randint(minimum, maximum))
 
     return numbers
 
+
 def quicksort(numbers):
     if len(numbers) <= 1:
         return numbers
@@ -26,7 +28,7 @@ def quicksort(numbers):
         )
 
         return (
-            quicksort(items_less) +
-            pivot_items +
-            quicksort(items_greater)
+                quicksort(items_less) +
+                pivot_items +
+                quicksort(items_greater)
         )
diff --git a/Recursion/recursive.py b/Recursion/recursive.py
index 2ece8db..b2a8b19 100644
--- a/Recursion/recursive.py
+++ b/Recursion/recursive.py
@@ -1,10 +1,11 @@
 def main():
     p(5)
 
-def p(a):
+
+def p(a: int):
     print(a)
-    if a!=1:
-        p(a-2)
+    if a >= 1:
+        p(a - 2)
 
 
 main()
diff --git a/Recursion/recursiveString.py b/Recursion/recursiveString.py
index 4f3b754..466ee56 100644
--- a/Recursion/recursiveString.py
+++ b/Recursion/recursiveString.py
@@ -1,9 +1,10 @@
 def main():
     p('faheem')
 
-def p(a):
+
+def p(a: str):
     print(a[-1], end='')
-    if len(a)>1:
+    if len(a) > 1:
         p(a[:-1])
 
 
diff --git a/Stack.py b/Stack.py
index c1e4754..4fd081b 100644
--- a/Stack.py
+++ b/Stack.py
@@ -1,59 +1,32 @@
-<<<<<<< HEAD
 size = 2
-stackArray = ['']*size
+stackArray = [''] * size
 tos = 0
 
+
 def push(s):
     global tos
     global size
     global stackArray
-    if tos==size:
+    if tos == size:
         print('stack full.')
     else:
-        stackArray[tos]=s
-        tos+=1
-def pop():
-    global tos
-    global stackArray
-    if tos==0:
-        print('no data to show')
-    else:
-        tos-=1
-        print(stackArray[tos])
+        stackArray[tos] = s
+        tos += 1
 
-pop()
-push('faheem')
-push('ali')
-push('nadeem')
-pop()
-pop()
-=======
-size = 2
-stackArray = ['']*size
-tos = 0
 
-def push(s):
-    global tos
-    global size
-    global stackArray
-    if tos==size:
-        print('stack full.')
-    else:
-        stackArray[tos]=s
-        tos+=1
 def pop():
     global tos
     global stackArray
-    if tos==0:
+    if tos == 0:
         print('no data to show')
     else:
-        tos-=1
+        tos -= 1
         print(stackArray[tos])
 
+
 pop()
 push('faheem')
 push('ali')
 push('nadeem')
 pop()
 pop()
->>>>>>> d2ba29fbfd3c554d05834d91472d14f729dcb33b
diff --git a/positionInFile.py b/positionInFile.py
index 2d52aef..eb50182 100644
--- a/positionInFile.py
+++ b/positionInFile.py
@@ -4,7 +4,7 @@
 print("read string is: ",str)
 #check current position
 position=fo.tell();
-print ("current position: ",position
+print ("current position: ",position)
 #reposition pointer at the beginning
 position=fo.seek(0,0);
 str=fo.read(10);