In the following code at the end of the for loop I use the assert function in order to test that a[i+1] is greater than or equal to a[i] but I get the following error (after the code below). Also in c++ the assert with the following seems to work just fine but in python (the following code) it does not seem to work...anyone know why? import random class Sorting: #Precondition: An array a with values. #Postcondition: Array a[1...n] is sorted. def insertion_sort(self,a): #First loop invariant: Array a[1...i] is sorted. for j in range(1,len(a)): key = a[j] i = j-1 #Second loop invariant: a[i] is the greatest value from a[i...j-1] while i >= 0 and a[i] > key: a[i+1] = a[i] i = i-1 a[i+1] = key assert a[i+1] >= a[i] return a def random_array(self,size): b = [] for i in range(0,size): b.append(random.randint(0,1000)) return b sort = Sorting() print sort.insertion_sort(sort.random_array(10)) The Error: Traceback (most recent call last): File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 27, in <module> print sort.insertion_sort(sort.random_array(10)) File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 16, in insertion_sort assert a[i+1] >= a[i] AssertionError