Directory size listing

The following python code lists the subdirectories and files of the given directory in the descending order of their size.

#!/usr/bin/python
import os

# this function returns the size of the given directory or file.

def getDirectorySize(directory):
    if os.path.isfile(directory):
        return os.path.getsize(directory)
    dir_size = 0
    for (path, dirs, files) in os.walk(directory):
        for file in files:
            filename = os.path.join(path, file)
            try:
                dir_size += os.path.getsize(filename)
            except OSError:
                pass #to manage for exampling a missing link etc
    return dir_size

#this function lists the directory contents of the 
#given directory by calling getDirectorySize(directory) 
#to get the size of each directories

def getDirectorySizeListing(directory):
    filesize = {}
    dir = os.listdir(directory)
    os.chdir(directory)
    for item in dir:
        sz = getDirectorySize(item)/2**20 #for converting into megabytes
        if sz: filesize[item] = sz
     
    #to sort the dictionary based on values
    from operator import itemgetter
    filesize = sorted(filesize.iteritems(),key=itemgetter(1),reverse=True)

    return filesize

#application code
d = "/home/suresh/"
x = getDirectorySizeListing(d)
for i,val in enumerate(x):
    print val