mergy.py

def mergesort(arr, l, m, r):
    n1 = m-l+1
    n2 = r-m
    L=[0]*n1
    R=[0]*n2
    for i in range(n1):
        L[i]= arr[l+i]
    for j in range(n2):
        R[j]= arr[m+1+j]

    i=0
    j=0
    k=l

    while(i<n1 and j<n2):
        if(L[i]<=R[j]):
            arr[k] = L[i]
            i+=1
        else:
            arr[k]=R[j]
            j+=1
        k+=1

    while(i<n1):
        arr[k]=L[i]
        i+=1
        k+=1
        
    while(j<n2):
        arr[k]=R[j]
        j+=1
        k+=1
    return(arr)



        
def divide(arr, l, r):
    if(l<r):
        m=(l+(r-1))//2
        divide(arr, l, m)
        divide(arr, m+1, r)
        return mergesort(arr, l, m, r)

arr = [12, 11, 13, 5, 6, 7]
print(divide(arr, 0, len(arr)-1))