I am doubtful of my implementation of the merge sort for two cases specifically:

1. If the size of the list is 2, then I have swapped the values if they are not in the ascending order else I have returned them.

2. In the merge function when the list tries to check outside the number of elements in it, I have assigned the greatest number (9999), so that in case of comparison with it always comes false.
Can anyone tell me if the implementation of my merge sort is correct or not? As in sorting is complete, but is the implementation of merge sort exact or is it wrong because of the cases?

Here is my code:

# unsorted LIST
u_list = [3, 6, 8, 1, 4, 7, 2, 12, 45];# Size of the unsorted list
global_size = len(u_list)def foo(temp_list):size_of_list = len(temp_list)# If the size of the list is 1if size_of_list == 1:return temp_list# If the size of the list is 2if size_of_list == 2:if temp_list[0] > temp_list[1]:temp_list[0],temp_list[1] = temp_list[1],temp_list[0]return temp_listelse: return temp_list# If the size of the list is greater than 2                if size_of_list > 2:count = 1i = 0if size_of_list % 2 == 0:mid1 = size_of_list / 2else:mid1 = (size_of_list / 2) + 1mid2 = size_of_list - mid1newlist1 = list()newlist2 = list()for e in temp_list:if count >= mid1 + 1:newlist2.append(e)else:newlist1.append(e)if count == size_of_list:breakcount = count + 1sorted_list = list()return merge(foo(newlist1), foo(newlist2))# Merging all the sorted components
def merge(list1, list2):i = 0j = 0k = 0size_of_list = len(list1) + len(list2)sorted_list = list()while k <= size_of_list - 1:if i == len(list1):list1.append(9999)if j == len(list2):list2.append(9999)if list1[i] < list2[j]:sorted_list.append(list1[i])i = i + 1elif list2[j] < list1[i]:sorted_list.append(list2[j])j = j + 1k = k + 1return sorted_listprint foo(u_list)

To be honest, I feel very uneasy if I see code like this ;). It may be correct, but my guts feeling sais it's not (what if there are numbers > 9999?). It is more complicated than necessary. The syntax is Python, but you are not using the power of Python.

Here's how I would implement merge sort in Python:

def merge_sort(sequence):if len(sequence) < 2: return sequencemid = int(len(sequence) / 2)left_sequence = merge_sort(sequence[:mid])right_sequence = merge_sort(sequence[mid:])return merge(left_sequence, right_sequence)def merge(left, right):result = []i = j = 0while i < len(left) and j < len(right):if left[i] < right[j]:result.append(left[i])i += 1else:result.append(right[j])j += 1 result += left[i:]result += right[j:]return result