diff --git a/py/p1.py b/py/p1.py
index b648ec0..83c7e5c 100644
--- a/py/p1.py
+++ b/py/p1.py
@@ -4,13 +4,15 @@
 #           ***
 #          *****
 
-def asterisk_tree(height,level):
-  if level > height:
-    return
-  for j in range(2*level-1):
-    print("*", end="")
-  print()
-  asterisk_tree(height, level + 1)
+def asterisk_tree(height, level):
+    if level > height:
+        return
+    for _ in range(height - level):
+        print(" ", end="")
+    for j in range(2 * level - 1):
+        print("*", end="")
+    print()
+    asterisk_tree(height, level + 1)
 
-n=int(input("Enter height of tree : "))
+n = int(input("Enter height of tree: "))
 asterisk_tree(n, 1)
diff --git a/py/p10.py b/py/p10.py
index cfc822f..bd445df 100644
--- a/py/p10.py
+++ b/py/p10.py
@@ -1,16 +1,18 @@
-#Finding Average RGB values using the listmaker fuction to generate list of rgb values for a pixel
-
-def listmaker(r,g,b,list1=[]):
+def listmaker(r, g, b, list1=None):
+    if list1 is None:
+        list1 = []
     list1.append(r)
     list1.append(g)
     list1.append(b)
     return list1
 
-pixel1=listmaker(23,78,34)
-pixel2=listmaker(210,56,67)
-pixel3=listmaker(23,78,248)
-r=(pixel1[0]+pixel2[0]+pixel3[0])/3
-g=(pixel1[1]+pixel2[1]+pixel3[1])/3
-b=(pixel1[2]+pixel2[2]+pixel3[2])/3
-rgb=[r,g,b]
-print("Average RGB values of the pixels are",rgb)
+pixel1 = listmaker(23, 78, 34)
+pixel2 = listmaker(210, 56, 67)
+pixel3 = listmaker(23, 78, 248)
+
+r = (int(pixel1[0]) + int(pixel2[0]) + int(pixel3[0])) / 3
+g = (int(pixel1[1]) + int(pixel2[1]) + int(pixel3[1])) / 3
+b = (int(pixel1[2]) + int(pixel2[2]) + int(pixel3[2])) / 3
+
+rgb = [r, g, b]
+print("Average RGB values of the pixels are", rgb)
diff --git a/py/p11.py b/py/p11.py
index 3d35661..8ae9993 100644
--- a/py/p11.py
+++ b/py/p11.py
@@ -1,9 +1,9 @@
 # Function to convert decimal to binary number
 
 def binaryconversion(n):
-   print(n % 2,end = '')
-   if n > 1:
-       binaryconversion(n/2)
+   if n > 0:
+       binaryconversion(n // 2)
+       print(n % 2, end = '')
 
 number=int(input("Enter Number: "))
 binaryconversion(number)
diff --git a/py/p12.py b/py/p12.py
index c5b0f4d..820823d 100644
--- a/py/p12.py
+++ b/py/p12.py
@@ -1,5 +1,4 @@
 # Program to multiply two matrices using nested loops
-
 A = [[1,2,3],[4,5,6],[7,8,9]]
 B = [[10,11,12],[13,14,15],[16,17,18]]
  
diff --git a/py/p2.py b/py/p2.py
index 237c9b9..10af50f 100644
--- a/py/p2.py
+++ b/py/p2.py
@@ -2,8 +2,11 @@
 # input- 1 -> output- [1], input- 2 -> output- [2]
 
 def add_item(item, items=[]):
-   items.append(item)
-   return items
+    if items!=[]:
+        items.remove(items[0])
+    items.append(item)
+    return items
+
 
 print(add_item(1))
 print(add_item(2))
diff --git a/py/p3.py b/py/p3.py
index c83d5ad..c6d89e6 100644
--- a/py/p3.py
+++ b/py/p3.py
@@ -1,13 +1,12 @@
 #program to remove all even numbers from the beginning of a list
 #eg: [2, 4, 6, 17, 10] -> [17, 10] 
 
-def delete_starting_evens(list):
-  for item in list:
-    if list[0] % 2 == 0:
-      list.pop(0)
-    else:
-      break
-  return list
+def delete_starting_evens(lst):
+    i = 0
+    while i < len(lst) and lst[i] % 2 == 0:
+        lst.pop(i)
+    return lst
+
+lst = [2, 8, 10, 11]
+print(delete_starting_evens(lst))
 
-list = [2, 8, 10, 11]
-print(delete_starting_evens(list))
diff --git a/py/p4.py b/py/p4.py
index 2ae30d4..d8c031f 100644
--- a/py/p4.py
+++ b/py/p4.py
@@ -6,12 +6,12 @@ def countSort(arr):
     ans = [0 for i in range(len(arr))]
     for i in arr:
         count[i] += 1
-    for i in range(k+1):
+    for i in range(1, k+1):
         count[i] += count[i-1]
-    for i in range(len(arr)-1, -1, -1):
-        ans[count[arr[i]]] = arr[i]
+    for i in range(len(arr)):
+        ans[count[arr[i]]-1] = arr[i]
         count[arr[i]] -= 1
-    return ans 
+    return ans
 
 arr = [3, 4, 12, 2, 4, 5, 5, 6, 12, 33, 10, 1, 2, 8, 6]
 ans = countSort(arr)
diff --git a/py/p5.py b/py/p5.py
index 01e1d53..ca907fc 100644
--- a/py/p5.py
+++ b/py/p5.py
@@ -1,5 +1,4 @@
 #recursive program to accept a number between 1 and 10 and print it
-
 def get_number():
     val1 = input('Enter a number: ')
     try:
diff --git a/py/p6.py b/py/p6.py
index fc571ba..9bfaa34 100644
--- a/py/p6.py
+++ b/py/p6.py
@@ -1,5 +1,4 @@
 #program to perform binary addition
-
 def addBinary(a: str, b: str) -> str:
     s = []
     carry = 0
diff --git a/py/p9.py b/py/p9.py
index 4ea1c58..430f386 100644
--- a/py/p9.py
+++ b/py/p9.py
@@ -3,7 +3,6 @@
 
 import string
 import sys
-
 # Define a function named 'ispangram' that checks if a string is a pangram
 def ispangram(str1, alphabet=string.ascii_lowercase):
     alphaset = list(alphabet)