大家好啊=2001 用python计算

#!/usr/bin/env python
#coding:utf-8
import os,sys
"""
      大
    大家
  大家好
大家好啊
2 0 0 1 
"""
def sum(num):
 #with open num.txt as f:
 if os.path.exists('num.txt'): # 判断文件是否存在
 if os.path.getsize('num.txt'): # 判断文件是否为空
 f=open('num.txt','a+') # 以追加方式打开文件
 f.truncate() # 清空文件内容
 else:
 os.mknod('num.txt')
 f=open('num.txt','a+')
 for d in range(10):
 for j in range(10):
 for h in range(10):
 for a in range(10):
 sum=d*1000+d*100+d*10+d+j*100+j*10+j+h*10+h+a 
 f.write('%s,%s,%s,%s = %s \n' % (d,j,h,a,sum)) 
 if sum == int(num):
 print d,j,h,a
 if d==j==h==a == 9:
 print "%s is a last num" % sum
 print "please input the num must less than %s" % sum
 f.close()
if __name__=='__main__':
 if len(sys.argv) == 1:
 sum(2001)
 elif len(sys.argv) == 2:
 sum("%s" % sys.argv[1])
 else:
 print "use: python %s %s " % (sys.argv[0],'num')