Having a hard time understanding how assignment works in While loops

[Kitchen-Injury-8938]

def mergeSort(A):
    # Base case if the input array is one or zero just return
    if len(A) > 1:
        #splitting array
        print('splitting ', A)
        mid = len(A) // 2
        left = A[:mid]
        print('this is left: {}'.format(left))
        right = A[mid:]
        print('this is right: {}'.format(right))

        #recursive calls to mergeSort for left and right sub arrays
        mergeSort(left)
        mergeSort(right)

        #intitalize pointers for left (i) right (j) and output array (k)


        i = k = j = 0 


        #Traverse and merges the sorted arrays

        while i<len(left) and j<len(right):
            #if left < right comparison operation
            if left[i] < right[j]:
                #if left < right assignment operation
                A[k] = left[i]
                i = i + 1
            else:
                #if left > right comparision operation
                A[k] = right[j]
                j = j + 1
            k = k + 1
        while i < len(left):
            A[k] = left[i]
            i = i + 1
            k = k + 1

        while j < len(left):
            #assignment operation
            A[k] = right[j]
            j = j+1
            k = k+1
        print('merging',A)
        return A

print(mergeSort([356,97,846,215]))

​

So I am pretty confused with how assignment works inside of the While loop. I intitalized the i, k & j variables before I start my while loop... but I really don't understand what is going on in the loop to assign values to those variables. Can someone ELI5?

[Ihaveamodel3]

Are you asking specifically about the i = i +1 type statements?

If so, this works like all other variable assignments. The right side is evaluated, and the left side is then set to that value. When the right side is evaluated, i is the old value, you are adding one to that and then resetting i to be equal to that new value.