Python removes unnecessary large files from the system

import os, sys
#引入统计模块
from stat import *
BIG_FILE_THRESHOLD = 10000000L
dict1 = {}    # filesize 做 key, filename 做 value
dict2 = {}     # filename 做 key, filesize 做 value
def treewalk(path):
    try:
        for i in os.listdir(path):
            mode = os.stat(path+"/"+i).st_mode
            if S_ISDIR(mode) <> True:
                filename = path+"/"+i
                filesize = os.stat(filename).st_size
                if filesize > BIG_FILE_THRESHOLD:
                    if filesize in dict1:                      
                        dict2[filename] = filesize
                        dict2[dict1[filesize]]=filesize
                    else:
                        dict1[filesize] = filename                 
            else:
                treewalk(path+"/"+i)
    except WindowsError:
        pass
def printdict(finaldict):
    for i_size in finaldict.values():
        print i_size
        for j_name in finaldict.keys():
            if finaldict[j_name] == i_size:
                print j_name
        print "\n"
if __name__=="__main__":
    treewalk(sys.argv[1])
    printdict(dict2)