MergeSort - Bottom Up - Python

a = [6,5,4,3,2,1]
print 'unsorted:',a
z = len(a)
tmp = range(len(a))
def sort(a,tmp):
        width=1
        while(width<z):
                i=0
                while(i<z):
                        left =i
                        middle = i+width
                        right = i+2*width
                        merge(a,left,middle,right,tmp)
                        i = i+2*width
                width=width*2
                print '\n'
def merge(a,iLeft,iMiddle,iRight,tmp):
        i = iLeft
        j = iMiddle
        k = iLeft
        print iLeft,iMiddle,iRight,'[',i,j,k,']'
        #print i ,j, k,'\n\n'

        while(i<iMiddle and j<iRight):
                if(i<iMiddle and j<iRight):
                        if(a[i]<a[j]):
                                tmp[k]=a[i]
                                i += 1
                                k += 1
                        else:
                                tmp[k]=a[j]
                                j += 1
                                k += 1

                elif (i==iMiddle):
                        tmp[k] = a[j]
                        j += 1
                        k += 1
                elif (j==iRight):
                        tmp[k]= a[i]
                        i += 1
                        j += 1

sort(a,tmp)
print 'Sorted Array:',tmp