Python: sort (3)

Abstract: bitmap sort

bitmap can store huge list with less memory usage. Another application of bitmap is for sort. But a shortage of bitmap sort is no duplicates allowed in a given list.

The result:
Unsorted list: [401, 293, 207, 304, 107, 10, 696, 677, 13, 788]
Sorted list by increasing: [788, 696, 677, 401, 304, 293, 207, 107, 13, 10]
Sorted list by decreasing: [10, 13, 107, 207, 293, 304, 401, 677, 696, 788]

The script:
# -*- coding: utf-8 -*-
"""
Created on Fri Jul 17 11:51:57 2015

@author: yuan
"""
import random
import math

class sort_methods:
    def __init__(self, arr):
        self.num=len(arr)
        self.arr=arr
       
    def to_bitmap(self):
        #create bitmap
        bitmap_len=int(math.ceil(max(self.arr)/32.))
        bitmap=[0]*bitmap_len
        for v in self.arr:
            divide, remainder = divmod(v, 32)
            bitmap[divide]=(2**remainder)+bitmap[divide]
       
        #convert to list
        mylist=[]
        for i in range(bitmap_len):
            bit_str=format(bitmap[i], 'b')[::-1]
            #print bit_str
            for index, element in enumerate(bit_str):
                a=0
                if int(element)==1:
                    a=i*32+index
                    mylist.append(a)
                #print index,element, a
        return mylist
   
    def Mysort(self,decreasing=0):
        #get bitmap
        sorted=self.to_bitmap()
        if decreasing ==1:
            sorted=sorted[::-1]
        return sorted
       

#####################
#main programm
arr=random.sample(range(1000),10)
print "Unsorted list:", arr
#
S=sort_methods(arr)           

#increasing
sorted=S.Mysort(decreasing=1)
print 'Sorted list by increasing:', sorted

#increasing
sorted=S.Mysort(decreasing=0)
print 'Sorted list by decreasing:', sorted