python merge sort code

mergeSort.py

def merge(array, p, q, r):
    sub1 = array[p:q+1]
    sub2 = array[q+1:r+1]
    k, i, j = p, 0, 0
    for k in range(p,r+1):
        if(i > len(sub1) - 1):
            array[k] = sub2[j]
            j+=1
        elif(j > len(sub2) - 1):
            array[k] = sub1[i]
            i+=1
        elif(sub1[i] > sub2[j]):
            array[k] = sub2[j]
            j+=1
        else:
            array[k] = sub1[i]
            i+=1

def mergeSort(array, p, r):
    if(r > p):
        q = (p + r)//2
        mergeSort(array, p, q)
        mergeSort(array, q + 1, r)
        merge(array, p, q, r)